Abalone 577
Abalone are generally found on temperate and tropical 4) Culture of free‐swimming larvae.
shores, attached to rocks and boulders, and often found 5) Settlement and metamorphosis of larvae.
in crevices and cracks in rocks. Their strong, muscular 6) Growth of postlarvae and juveniles.
foot allows them to adhere to the substratum, even where 7) Grow‐out of adults.
moderate to strong wave action occurs. They occur from
the low intertidal to a depth of about 30 m, and tend to 25.4.1 Broodstock
favour areas supporting seaweed beds, particularly kelps.
Farms that do not have a captive, breeding population of
Most abalone adults are macroalgal herbivores, abalone adults, normally have to resort to collection of
feeding on whatever algae are available in their habitat, suitable adults from the wild, which normally requires a
usually by trapping drift algae under the muscular foot. permit from local authorities. In some cases (e.g.,
A file‐like radula is used to scrape algae from rocks or to Australia) ripe adults are collected and transferred to a
rasp the surface layers from macroalgae. Some species hatchery at a time to coincide with the natural spawning
show preferences for particular types of algae, although season whilst, in other cases (e.g., South Africa), adult
laminarian phacophytes are the most commonly con- animals are brought into the farm and maintained under
sumed (Leighton, 2000). Some abalone will also eat small controlled conditions until their gonads are fully devel-
invertebrates attached to the algae. Postlarvae and very oped. Successful conditioning of broodstock is a crucial
small juveniles graze on benthic diatom films and step for breeding programs. Gonad maturation and lar-
encrusting algae that coat rock surfaces. val settlement success of abalone are known to vary sea-
sonally and there is a large variability in spawning
Sexes are separate and, in most species, a 1:1 sex ratio events, hatchability, and larval and juvenile survival
is maintained (Geiger and Owen, 2012). The gonad tis- rates during the same season between batches and
sue becomes visible when the shell reaches about 30 mm hatcheries. The most important factors affecting the
shell length (SL), and the gonads can be seen under the time that it takes for gonads to develop are water tem-
edge of the mantle membrane or under the foot. The sex perature and access to adequate and appropriate feeds.
of an adult can be determined by turning an abalone Physiologically, neurosecretory cells, associated with
upside‐down and pushing the foot aside to observe the cerebral, pleural‐pedal, and visceral ganglia have been
colour of the gonad. When immature, the gonad is gen- shown to control gametogenesis, vitellogenesis and
erally a dark‐brown colour, but it turns green in females spawning (Leighton, 2000).
and cream‐white in males as they mature. Most species
grow between 15 to 30 mm in their first year and become During conditioning, animals can be either fed on
mature at between 3 to 5 years. Some very large abalone natural food, including seaweeds, or on a specially
have been estimated to live up to 50 years (Geiger and formulated artificial diet. Formulated feeds designed to
Owen, 2012). maximise growth rates are not necessarily appropriate
to produce viable, high quality eggs and larvae. There is
Successful reproduction requires that males and growing evidence that specific dietary lipids play
females spawn synchronously, often responding to exter- an important role in gonadogenesis of abalone. For
nal cues such as water temperature, photoperiod or lunar Australian species, the inclusion of red seaweeds in
cycles. Abalone are broadcast spawners, the eggs and conditioning diets has been found to be important.
sperm being released into the water where fertilisation This is because red seaweeds contain arachidonic acid
occurs externally. For successful fertilisation, a minimum (20:4n‐6) which is a major precursor of prostaglandins
population density is required in the natural environ- that play a vital role in molluscan reproduction. Artificial
ment and, although this varies between species, an feeds, specifically designed for broodstock conditioning,
example quoted for California, suggestes that a mini- should also contain appropriate dietary lipids.
mum population density of 2000/ha is required
(California Department of Fish and Wildlife, 2014). At temperatures within the normal range, there is a
positive linear relationship between the Visual Gonad
25.4 Culture Techniques Index VGI and conditioning time of H. discus hannai.
The rate of increase in VGI is proportional to water tem-
The successful culture of abalone requires the following perature, and when each value is plotted against water
seven phases, which are characteristic of the aquaculture temperature, the zero value for VGI can be calculated,
of many marine species and are illustrated in Figure 25.4: giving an estimate of the Biological Zero Point (BZP), the
temperature below which no gonad development occurs.
1) Collection and conditioning of broodstock. By subtracting the BZP from the daily water temperature
2) Induction of spawning. and summing this figure over the conditioning
3) Fertilisation. time (in days), it is possible to describe the Effective
578 Aquaculture
Fertilisation Free Swimming Figure 25.4 The life cycle of abalones.
Trochophore larva Source: Reproduced with permission
from Peter Cook.
Sperm Ovum Veliger
larva
Released into water
Settlement
Postlarval to
Juvenile stage
Male ADULTS Female
Accumulative Temperature (EAT, expressed as °C × days) During hatchery spawning, fully ripe adults are usually
for completion of gametogenesis and spawning. As an separated by sex and placed into filtered seawater in
example, the EAT for H. discus hannai is about 1000 °C‐ relatively small plastic containers, generally three to four
days for males and about 1500°C‐days for females individuals per container. Filtered, UV‐irradiated seawa-
(Leighton, 2000). By keeping adults at warmer than ter is passed through the container at about 0.5 L/min.
ambient temperatures, similar to those present during The intensity of UV light required depends on the
the spawning season, and with access to adequate food, s pecies but for H. discus hannai, an intensity of 2.42 W/L
gonad development can be accelerated. For Australian is generally used. Spawning usually occurs after about 2
species, the BZP for greenlip abalone (H. laevigata) hr of exposure. If the hydrogen peroxide method is used,
is about 6.9°C and for blacklip abalone (H. rubra) is the container is emptied and then filled with 3% (v/v)
about 7.8°C. hydrogen peroxide, buffered with 2 mol/L Tris‐buffer.
The animals are left in this solution for up to 2 hr, but the
25.4.2 Spawning buffered seawater is replaced with clean, filtered seawa-
Once the gonads of adult abalone are completely devel- ter as soon as there is any sign of gamete release.
oped, they sometimes spawn spontaneously, probably in
response to minor environmental changes or to handling 25.4.3 Fertilisation
stress. In a hatchery, however, control of the timing of Eggs and sperm are collected soon after spawning.
both male and female spawning is essential to obtain suc- Fertilisation is achieved by adding a small volume of
cessful fertilisation. A number of spawning induction water containing about 25 000 sperm/mL, to a bucket
methods have been developed, the most common of containing eggs. The ratio is between 10 to 100 sperm
which are the manipulation of water temperature, short per egg. The contents of the bucket are carefully mixed,
periods of exposure to air, the addition of hydrogen and the eggs are then allowed to settle. After 5 to 10 min
peroxide and the application of UV light. the water is siphoned from the bucket and replaced with
clean, filtered seawater at the same temperature. The
In the past, short periods of desiccation, by removing fertilised eggs are then washed several times with clean,
the animals from water for an hour or so, or thermal filtered seawater and then transferred to hatching tanks.
shock, produced by increasing water temperature by 5 to
10oC, were commonly used to induce spawning; but both 25.4.4 Larval Development
methods are unreliable and sometimes produce poor Fertilised eggs remain at the bottom of the hatching tank
quality gametes. More effective and reliable methods are during pre‐hatch development and no aeration is applied
to irradiate seawater with UV light or treat it with hydro- at this stage. Care is taken to ensure that the layer of eggs
gen peroxide at slightly elevated pH. In both cases, on the bottom is not too crowded, a density of 200/cm2
spawning induction appears to be in response to the
presence of free oxygen radicals in the seawater.
being recommended. Water is changed at least once Abalone 579
per day. The time between fertilisation and hatching var-
ies between species and depends on water temperature, The length of time that larvae can remain free‐
but it is generally between 10 to 24 hr. After hatching, swimming before settlement depends on the endogenous
the free‐swimming veliger larvae swim into the water supply of yolk. Generally, if they do not find a suitable
column and generally accumulate near the surface. settlement substratum within a week or so, post‐
Gentle water exchange and aeration can be applied at settlement survival is very low.
this stage. ‘Banjo’ sieves, with a very fine mesh of not
more than 100 μm, are used to prevent the veligers from In the natural environment, encrusting coralline algae,
being washed out of the hatching tanks. diatoms, and bacterial films appear to be the most
effective inducers of settlement. Coralline algae induce
A few days after hatching, larvae are removed from the attachment and metamorphosis in all abalone species but
hatching tank, usually by siphoning water and larvae the settlement‐inducing chemicals from corallines have
from near the water surface, care is taken not to suck up not been identified. The use of coralline algae to induce
un‐hatched eggs or dead larvae from the bottom of the settlement in hatcheries is not considered practical.
tanks. Larvae are transferred to large larval rearing tanks
at a density of between 5 to 20 larvae/mL. Continuous Veliger larvae are transferred into settlement tanks at a
gentle aeration and water exchange are employed at this density of 1000–2000/m2 of available settlement surface.
stage. The larvae are lecithotrophic and, therefore, do In these tanks larvae are usually settled on to clear, p lastic
not need to be fed. The length of time spent as free‐ plates, normally held in batches by being fixed vertically
swimming larvae depends on a number of factors, par- into racks (Figure 25.5). A range of different techniques
ticularly water temperature, but generally, this is between can be used to induce settlement and metamorphosis,
5 to 7 days. Larval mortality is high at this stage, often the most common of which are:
reaching up to 90%. Veliger larvae reach metamorphic
competence after 3–8 days post‐fertilisation. Once the ●● coating the plates with a film of diatoms and/or
larvae have reached metamorphic competence, they are bacteria;
ready to settle onto a suitable substratum. Settlement of
abalone larvae involves larval attachment (a reversible ●● coating the plates with a green, encrusting algae,
behavior) followed by metamorphosis (which involves Ulvella lens;
irreversible physical changes).
●● allowing abalone juveniles to graze on diatom‐coated
plates before placing the plates into settlement tanks
(the juveniles leave a mucous trail on the plates);
●● treating the water in the settlement tank with gamma‐
amino butyric acid (GABA) at a concentration of 10−6 M.
Figure 25.5 Plastic settlement plates held vertically in a frame, and a large corrugated plastic feeding plate, with juvenile abalone
attached to the underside. Source: Reproduced with permission from Peter Cook.
580 Aquaculture is to place horizontal feeding plates, usually p lastic sheets
with access holes drilled into them (Figure 25.5), above
When diatom films are used to induce settlement, it is the vertical settlement plates. Juveniles still feed on the
important that the species and size of the diatoms are diatoms adhering to the vertical settlement plates but will
appropriate. Generally small, pennate diatoms, with a gradually transition onto the food provided on the hori-
length of about 10 μm or less, such as species of zontal feeding plates. In other cases (e.g., in New Zealand)
Navicula, Cocconeis, Amphora, and Nitzschia, have the more common method is to leave juveniles in the set-
been found to be suitable for first‐feeding postlarvae. tlement tanks for 6–9 months, by which time they will
In some farms, particularly in Australia, Ulvella lens has have reached 10–15 mm SL. An alternative method, used
become a commonly used replacement for diatoms to particularly in South Africa, is to transfer juveniles, at
induce settlement and as a food source for first‐feeding about 3–5 mm SL, to an intermediate stage between set-
postlarvae. tlement and grow‐out. Small inverted plastic cones are
placed on the bottom of a shallow tank and aeration is
Pre‐grazed settlement plates are prepared by allowing applied beneath the cones. Diatoms and algae are added
small juveniles of conspecific abalone to graze on plates to the tank. Animals remain under the cones during the
conditioned with diatoms before placing them into day, but emerge to feed on the algae and diatoms at night.
the settlement tanks. As the juvenile abalone move over
the plates, they leave a trail of mucus which becomes When juveniles reach 5–10 mm SL in the wild, they
populated with bacteria. The mucus from the foot of start to feed on large seaweeds, eating an average of
grazers probably contains chemicals that trigger attach- about 20% of their body weight per day. Many farms also
ment or metamorphosis, but such chemicals have not use seaweeds to feed juveniles, the species of seaweed
been positively identified. Together with the diatoms, the used depending, to a large extent, on local availability.
bacteria, and mucus provide a food source for the newly Examples of seaweeds commonly used are Ecklonia,
settled larvae and postlarvae. Although the pre‐grazing Laminaria, and Macrocystis, often supplemented with
method is still sometimes used in Japan, it is too labour‐ Ulva or Gracilaria. Whenever possible, red seaweeds
intensive for most modern abalone farms, and has (e.g., Porphyra) are included in the diet of juveniles as
g enerally been replaced by other methods. they have been found to promote good growth rates.
Various pure chemicals can be used to induce attach- 25.6 Grow‐Out Systems
ment and/or metamorphosis of abalone larvae. These
may bind to larval receptors (e.g., GABA) or may act as There are many different types of grow‐out systems
neurotransmitter inhibitors, but their precise mode of used in different countries, often reflecting the local
action remains unclear. None of these chemicals is con- water conditions and the specific requirements of the
sidered to be a natural settlement cue, and only GABA abalone species being farmed. The most commonly
has been used in abalone hatcheries. Some hatcheries used now are:
use antibiotics together with GABA but this practice is ●● land‐based tanks with pump‐ashore water;
generally discouraged now for environmental reasons. ●● sea cages;
●● intertidal ponds;
25.5 Postlarvae and Juveniles ●● sea ranching.
The choice of grow‐out method is determined by factors
Once settled onto a suitable substratum, the postlarvae such as:
begin to feed. On settlement plates, they initially feed on ●● availability and cost of land;
the biofilm of diatoms and bacteria. At this stage, a post- ●● the cost of labour;
larval density of 10/cm2 is common. Subsequent growth ●● swell and sea conditions at the farm location;
and development of the postlarvae depends very much ●● water quality of the local seawater;
on an adequate supply of food in the microbial film. ●● access to secure ranching locations;
Many farms achieve high postlarval densities by adding a ●● local and national environmental regulations.
daily supply of diatoms. In many cases, however, exhaus- In Taiwan and China, a multi‐tiered basket system has
tion of the food supply may reduce the achievable been developed whereby abalone are placed into plas-
p ostlarval density to about 1/cm2. tic cages, stacked several tiers high, and housed in
indoor cement ponds. Whilst ponds are drained, the
As the postlarvae grow to between 3 to 5 mm SL, they baskets can be opened so that seaweed food can be
gradually transition onto a diet of macroalgae. In a hatch-
ery, however, unless the operation has access to supplies
of seaweeds, this transition is often onto small pellets of
an artificial diet.
There are many different methods used to culture
juveniles. A common method (used, for example, in China)
hand‐fed into the cages. This system is particularly Abalone 581
useful where land availability is limited or very expen-
sive. In some farms, the system has been extensively u ndertaken in off‐shore cages, where overall produc-
mechanised so that entire stacks of baskets can be tion costs are significantly lower (Figure 25.6).
lifted by cranes to facilitate feeding or cleaning, whilst
leaving the ponds completely full of water. Although Off‐shore cages are also used in Chile to grow abalone
the tiered basket system has many advantages, (Figure 25.7) although, in this case, the cages are much
the majority of Chinese abalone production is now larger and usually require a barge with an on‐board crane
to lift them for feeding, cleaning, and harvesting.
In countries such as South Africa and Australia, where
sea conditions and swells are generally unfavourable for
Figure 25.6 An off‐shore abalone farm in, Xaimen, China using net cages. Source: Reproduced with permission from Peter Cook.
Figure 25.7 Large cage used in an
off‐shore abalone farm near Puerto Montt,
Chile. Source: Reproduced with permission
from Peter Cook.
582 Aquaculture
Figure 25.8 A shallow‐water slab tank as used in Australia for on‐growing abalone. Water depth is normally about 10 cm. Source:
Reproduced with permission from Peter Cook.
in sea culture, land‐based tanks are commonly used. The Australia and South Africa, ranching is a more recent
precise design of such tanks is, however, very variable. innovation and utilises either natural reef, or artificial
The designs most commonly used in South Africa are substrate designed specifically for this application. The
deep tanks and slab tanks are used in Australia. The advantage of this method of abalone production is that,
South African deep tank is particularly suitable where once deployed into the sea, relatively little labour is
the abalone are fed mainly on seaweeds, whereas the required to maintain them until they are ready to be har-
Australian slab tank was designed primarily for use with vested. A disadvantage, particularly in South Africa, is
artificial, pelleted feeds. that it is difficult to secure the animals from illegal
exploitation during their time on the reef.
In the South African, deep tank system, abalone are
usually held in nets or plastic baskets, suspended in the In order to ensure the economic viability of a farming
water. Surface area is maximised by use of a series of ver- operation, it is important that the animals achieve an
tical plates, usually held in place by a rack. Seaweed, as acceptable growth rate. In land‐based tanks, a growth rate
food, is inserted between the vertical plates. A horizontal of up to 30 mm/yr can be achieved during the first grow‐
plate is often located over the top of the vertical plates, out year, but the rate generally reduces after this. It can
and this can be used as a feeding platform. take animals up to four or five years in grow‐out to reach
marketable size. A notable exception is the tropical aba-
The Australian slab tank system is based on very large lone, H. asinina, which grows very quickly in warm water,
concrete tanks in which the abalone are kept in very shal- and can achieve 60 mm SL after a year in grow‐out.
low water, perhaps only about 20 cm deep (Figure 25.8).
Overall tank dimensions can be as much as 15 m long by Abalone farmers have a choice of feeding their stock
5 m wide. Water movement is maintained by a water‐ either on natural seaweeds, on formulated feeds, or on a
dumping bucket system, located at one end of the slab. combination of both. In countries such as South Africa,
Some recent variations of this system (used, for example, where huge quantities of harvestable kelp are available,
in New Zealand) use plastic tanks of similar dimensions this is often the feed of choice. In other countries, such as
that can be stacked several layers high. Australia, less seaweed is available and, therefore, it is
more common to utilise formulated feeds. Both systems
In some countries, abalone are grown on near‐shore have their advantages and disadvantages and, as an
reefs, in various types of ranching operations. The juve- example, the characteristics of a seaweed diet and for-
niles are produced in hatcheries and then moved into the mulated feed used in South Africa, are listed in Table 25.2.
sea when they are about 50 mm SL. This method has
been used in Japan for many years, natural reefs being A wide variety of seaweeds can be used as abalone
used to deploy the juveniles. In other countries, such as feed. In China and Taiwan, Gracilaria is often cultured
Table 25.2 Characteristics of a seaweed and formulated diet Abalone 583
(including % Proximal Composition) used in South Africa.
then spread to wild populations. It seems likely, however,
Component Seaweed (e.g., kelp) Formulated feed that factors such as over‐stocking of farms and deterio-
ration of water quality near farms, have contributed to
Protein (%) 10–17 26–34 the spread of parasites and diseases. The two main types
Fat (%) Negligible <5 of abalone diseases and two main types of parasites,
Ash (%) 25 10 described below, have been identified as being the most
Carbohydrate (%) 62 50–60 important.
FCR 15 (wet); 2.4 (dry) 1
Cost (USD) 103/wet t 140/t Withering syndrome is an abalone disease that was
originally found in California in 1986 in black (H. crach-
Source: Data with permission from Peter Britz, Ichthyology and erodii) and red (H. rufescens) abalone. Some populations
Fisheries Science, Rhodes University, South Africa. of black abalone declined by almost 99% soon after the
disease was first observed in the Channel Islands of
as abalone feed. Macrocystis species are usually used in California and off Santa Barbara. More recently, it
California, whilst in South Africa, Laminaria species has also been described in pink (H. corrugata), white
and Ecklonia species are more common. In preference (H. sorenseni) and green (H. fulgens) abalone. Although
experiments, abalone have been found to select red sea- originally described as a viral disease, it is known that it
weeds, and there is some evidence that a combination of is closely associated with a Rickettsiales‐like prokaryote
different seaweed species gives a better growth rate than (RLP); possibly suggesting that it is actually the RLP that
a monospecific food source. Seaweeds can also be used is responsible for the symptoms of the disease. The
in combination with formulated diets and this can also disease attacks the lining of the gut, inhibiting the
produce good growth rates. p roduction of digestive enzymes. To prevent starvation,
the abalone consumes its own body mass, causing its
The use of formulated abalone diets was first devel- muscular foot to wither. This reduces the animal’s ability
oped in Japan, but now most farms throughout the world to cling to rocks, making it far more vulnerable to preda-
use artificial diets at some stage of their production tors. Withering syndrome has had a devastating effect on
cycle. Much research is still being carried out on the Californian abalone populations and came close to
development of artificial diets, particularly aimed at completely wiping out all populations of some of the
reducing manufacturing costs, whilst also improving local species. Intensive recovery efforts have recently
performance. Manufactured abalone diets generally improved the situation and it may be that, in the future,
contain high levels of proteins and carbohydrates, and with continued conservation actions, populations in the
low levels of fat and fibre. Some formulated diets are wild may be restored.
manufactured to include feeding attractants. Additives
to reduce leaching of nutrients are also important. Another important viral disease, called Abalone Viral
Ganglioneuritis (AVG), was discovered in abalone farms
The formulation of abalone diets is still the subject of in Australia in 2005. Confined mainly to Victoria and
intense research, particularly aimed at reducing costs Tasmania, this had devastating effects on both wild and
whilst, at the same time, maintaining dietary efficiency. Of farmed abalone populations. AVG can cause high mor-
particular importance, in recent years, has been the reduc- tality rates of up to 90%, in all age classes. It was first
tion of fishmeal and fish oils in diets, and their replace- detected in two Victorian abalone processing plants, and
ment by plant‐based, or synthetic componants. In subsequently in wild Victorian abalone stocks. It was
addition, it has been recognised that different stages of the later confirmed in Tasmania in 2008 in both wild stocks
abalone life history require different dietary formulations, and in processing plants. Tasmania has reported further
a particularly important change occurring as the animals outbreaks of AVG in 2010 and 2011. Once AVG was
become sexually mature, usually at about 30 mm SL. identified, it was declared a notifiable disease in Australia
under the Diseases of Livestock Act, 1994. A similar viral
25.7 Diseases and Parasites disease occurs in several other countries, including
Taiwan. AVG affects the nervous system of abalone and
Until recent years, little was known about abalone results in curling of the foot, swelling of the mouth, and
disease in the wild, but as aquaculture increased, disease eventually weakness and death. AVG affects both black-
occurrence became more common. It is generally lip (H. rubra) and greenlip (H. laevigata) abalone, as well
uncertain whether these diseases originated from wild as the hybrid between the two, but there is no evidence
populations or whether they originated on farms and that AVG has any effect on human health. Since the dis-
covery of AVG, very strict biosecurity protocols have
been imposed on both the abalone farming and fishing
industries. In addition, a Code of Practice, designed to
584 Aquaculture create an over‐supply in world markets and reduced
market prices. A large percentage of the Chinese
improve biosecurity procedures, was developed and production is, however, sold and consumed within
applied to aquaculture farms, commercial harvesters, China and the overall influence of China on the world
recreational divers, and commercial processors. So far, abalone market has, therefore, been less than some may
the improved biosecurity appears to have helped to pre- have expected. Prices fell by as much as 30% between
vent further spread of the disease. about 2008 and 2012 but the Global Financial Crisis was
the main reason for this (Cook and Gordon, 2010),
Another important abalone disease is caused by by a rather than an over‐supply of product. The fall in price,
boring sabellid worm (Terebrasabella heterouncinata), together with the outbreak of several diseases, com-
which is endemic to South Africa (Ruck and Cook, 1998), bined to reduce confidence in abalone farming in China
but in the mid‐1990s was also discovered in California, and, several farms ceased to operate during that time or
possibly resulting from the illegal importation of South turned to producing alternative species.
African abalone into the USA. The sabellid worms bore
small holes into the growing edges of abalone shells, The future of abalone farming, both in China and the
resulting in the shells becoming deformed. Infected rest of the world, and the predicted level of production,
individuals show reduced growth rates and poor meat are still the subject of much speculation. What is certain,
yield, probably because of the extra energy that is however, is that to be competitive in the future, farms
c hanneled into shell repair as opposed to meat growth. both inside and outside of China, will need to reduce the
cost of production by implementing more efficient
The mudworm (Polydora species), has also been found production methods, in particular by reducing the costs
in abalone where it bores into the shell and causes inter- of labour and by the use of less expensive and more
nal mud blisters. Because the blisters can affect the efficient feeds. Recently, some farms have adopted inter-
a dhesion of the body to the shell, this can cause signifi- national environmental certification standards and,
cant mortalities on farms, sometimes up 60% of the stock. besides the possibility that this will increase market
Proliferation of the mudworms can generally be con- access, it may also help them to improve efficiency and
trolled by good animal husbundry techniques, including reduce production costs.
keeping the animls off the bottom and preventing the
build‐up of excessive bottom sediments. Infected animals
are usually culled to prevent the spread of the parasites.
25.8 The World Abalone Market 25.9 Summary
Even though there have been huge recent increases in ●● Abalone are large gastropod molluscs, belonging to
abalone farming, worldwide demand still exceeds supply, the exclusively marine family, Haliotidae, that has
and it is a ‘demand‐driven’ market. The total supply of 56 valid species, with 18 sub‐species.
abalone available to the world market in 2015 was more
than five times that which was available in the 1970s. ●● Abalone are found on shallow, sub‐tidal rocky shores
This, of course, has resulted from huge increases in farm in many tropical and temperate waters and, in several
production. What effect this will have on the interna- countries, they form the basis of commercial fishery
tional abalone market is a question that has often been and aquaculture industries. Although many of the
asked. China is both a major producer and consumer of world’s fisheries have been over‐exploited, abalone
abalone, and whilst China has often been regarded as a farming has expanded rapidly over the past decade or
huge marketing opportunity, over‐production in China so, especially in China and South Korea.
could also represent a risk that may swamp world
markets. Although it is expected that Chinese farm ●● On farms, ripe adults are either collected from the wild
production will continue to increase, the rate of increase and transferred to a hatchery at a time to coincide with
in production is expected to slow. the natural spawning season, or adult animals are
brought into the farm and maintained under con-
Prices paid for farmed abalone on the world market are trolled conditions until their gonads are fully devel-
affected by a number of different factors including the oped. Synchronous spawning of males and females is
species cultured, the country of origin, the size at which essential to obtain successful fertilisation.
the animals are marketed, and the quality of the meat. In
Chinese and Japanese markets, H. discus hannai is the ●● The most common hatchery spawning methods
most valuable species and, in general, larger size animals include the manipulation of water temperature, short
command higher prices per kg. periods of exposure to air, the addition of hydrogen
peroxide and the application of UV light. Fertilised
Considering the recent huge increases in farm pro- eggs hatch after about 24 hr, and then the free‐
duction in China, it might be expected that this would swimming veliger larvae swim into the water
column.
●● After hatching, larvae are transferred to large larval Abalone 585
rearing tanks, where they reach metamorphic
c ompetence after 3–8 days. Settlement of larvae onto a ●● The juvenile abalone are then transferred into grow‐out
suitable substratum involves larval attachment, fol- systems, the details of which vary in different countries,
lowed by metamorphosis. In farms, veliger larvae are often reflecting the local water conditions and the
settled onto clear, plastic plates, which have been pre‐ specific requirements of the abalone species being
conditioned. The plates are normally held in batches farmed. The most commonly used grow‐out systems
by being fixed vertically into racks. The postlarvae are land‐based tanks with pump‐ashore water; sea
then begin to feed, initially on a biofilm of diatoms and cages; intertidal ponds; or sea ranching. In these, aba-
bacteria and subsequently, as they grow to between 3 lone are either fed natural seaweeds or formulated diets.
to 5 mm SL, they gradually transition onto a diet of
macroalgae or onto small pellets of an artificial diet. ●● With the recent huge increases in abalone produced
on farms, the total supply of abalone available to the
world market in 2015 was more than five times that
which was available in the 1970s.
R eferences fishable biomass following a mass mortality in an
Australian molluscan fishery. Journal of Fish Diseases,
California Department of Fish and Wildlife (2014). 34, 287–302.
www.wildlife.ca.gov/Conservation/Marine/ Park, Choul‐Ji and Kim, S. Y. (2013). Abalone aquaculture
Red‐Abalone‐FMP [accessed April 2016]. in Korea. Journal of Shellfish Research, 32, 17–19.
Ruck, K. R. and Cook, P. A. (1998). Sabellid infestations in
Cook, P.A. and Gordon, G.H. (2010). World abalone the shells of South African molluscs: implications for
supply, markets and pricing. Journal of Shellfish abalone mariculture. Journal of Shellfish Research,
Research, 29, 569–571. 17, 693–699.
Simpson, B. J. A. and Cook, P. A. (1998). Rotation diets: a
Hahn, K. O. (1989). Handbook of Culture of Abalone and method of improving growth of cultured abalone using
other Gastropods. CRC Press, Boca Raton, FL. natural algal diets. Journal of Shellfish Research,
17, 635–640.
Leighton, D.L. (2000). The Biology and Culture of Californian Shepherd, S.A., Tegner, M.J. and Guzman del Proo, S.A.
Abalone. Dorrance Publishing Company, Pittsburgh, PA. (Eds.) (1992). Abalone of the World: Biology, Fisheries
and Culture. Fishing News Press. Oxford.
Lessard, J. and Campbell, A. (2007). Describing northern
abalone, Haliotis kamtschatkams, habitat: Focusing
rebuilding efforts in British Columbia, Canada. Journal
of Shellfish Research. 26, 677–686
Mayfield, S., McGarvey, R., Gorfine, H.K., Peters, H.,
Burch, P. and Sharma, S. (2011). Survey estimates of
587
26
Aquaculture in the Aquarium Industry
Thane A. Militz
CHAPTER MENU 26.6 Sustainable Development, 612
26.1 Introduction, 587 26.7 The Future of Aquaculture in the Aquarium Industry, 614
26.2 The Aquarium Industry, 587 26.8 Summary, 614
26.3 The Need for Aquaculture in the Aquarium Industry, 589
26.4 Aquaculture of Tropical Freshwater Organisms, 593 References, 615
26.5 Aquaculture of Tropical Marine Organisms, 601
26.1 Introduction These facets combined with growing affluence in the
primary markets have boosted the popularity of the
The domestication of aquatic organisms for aesthetic and aquarium hobby and have contributed significantly to
ornamental purposes has been practiced for over a thou- recent trade and industry growth.
sand years. Starting in ancient China (ca. 265–420 AD),
culture of the normally grey or silver carp (Carassius 26.2 The Aquarium Industry
auratus), for human consumption, would occasionally
yield ‘gold’ phenotypes. These ‘golden’ carp became a The trade of aquatic organisms for private and public
symbol of wealth and prosperity for the imperial family aquariums, as well as water gardens, along with associ-
and were kept in outdoor ponds as part of manicured, ated equipment, furniture, accessories, and literature has
ornamental gardens. The more than 300 strains of goldfish become a multi‐billion dollar industry known as the
commonly available today reflect more than a century of aquarium or aquatic‐ornamental industry. The most
aquaculture production and selective breeding of these recent estimates of the value of the aquarium industry
original ‘golden’ carp. A similar, although often briefer, are in the vicinity of USD 15 billion/yr (Prang, 2007;
history is reflected in many of the aquatic organisms Whittington and Chong, 2007).
currently traded in the aquarium industry.
Organisms supplied for the aquarium industry include
The market and trade of aquarium species in the last fishes, a diversity of invertebrates, and aquatic plants.
25–30 years has grown substantially. Establishment of Among this myriad of aquatic organisms traded, fresh-
rapid and reliable transportation and improved shipping water and marine fish species are the most popular and,
techniques has allowed remote locations that are har- aside from aquarium supplies, form the primary product
bouring unique aquatic species to be connected with of the aquarium industry. An estimated 2 billion live
consumers. The past 15 years, in particular, have seen aquarium fishes are transported internationally every
developments in captive husbandry and life‐support year (Monticini, 2010). On a unit weight basis, aquarium
technology making aquarium care easier, more success- fishes are the most valuable fisheries commodity in the
ful, and allowing for a greater diversity of aquatic organ- world: freshwater aquarium fishes having a value of USD
isms to be held in captivity. This is especially true for 77–130/kg; while marine aquarium fishes fetch USD
the marine aquarium industry. High profile exposure of 500–1300/kg (Wabnitz et al., 2003; Monticini, 2010). By
the trade through motion pictures (Finding Nemo and value, the sale of freshwater fishes dominates the trade in
Finding Dory) has also brought substantial media atten- aquarium organisms, making up approximately 80% of
tion to the aquarium hobby (Militz and Foale, 2017).
Aquaculture: Farming Aquatic Animals and Plants, Third Edition. Edited by John S. Lucas, Paul C. Southgate and Craig S. Tucker.
© 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
588 Aquaculture recently been affected by a shift in sourcing organisms
from regions closer to the consumer, to reduce rising
sales. However, the volume of traded individuals is much transportation expenses.
greater for freshwater fishes due to the higher unit value
of marine aquarium fish sales. The major use of organisms traded in the aquarium
industry is largely for the purpose of private aesthetic
Comprehensive and accurate trade statistics that enjoyment by the consumer. Other desires reflected
define trends in aquarium industry trade activities are by consumers include use of aquaria as a symbol of
limited and variable. This is largely due to prestige, therapeutic furniture or as an educational
●● the complexity of the industry leading to inconsisten- endeavour (Figure 26.1). As a hobby or luxury item,
consumers of aquarium organisms are largely concen-
cies in reporting between countries and companies trated in affluent countries that conform to a world-
within countries, view embracing the intrinsic and aesthetic value of
●● differences in freight stocking densities, and nature. The leading importers of aquarium fishes
●● sporadic or missing record keeping by both importing reflecting this trend is the USA which is the primary
and exporting countries. consumer followed by Europe, Japan and Australia
It is widely accepted that trends in aquaculture production (Prang, 2007). A substantial aquarium fish market
and fisheries catch for the industry vary from year to year exists in China. However, this demand is largely met
depending on factors such as the economic situation in from domestic aquaculture production with few imports.
the importing/exporting country, the popularity of the In the USA it is estimated that 10% of households keep
aquarium hobby in competition with other activities freshwater aquaria with 0.8% of households keeping
(e.g., information technology), disease outbreaks and marine aquaria. This puts the marine aquarium hobby
major weather phenomena (Prang, 2007). Traditional
sources of origin for many aquarium organisms has also
Figure 26.1 The aquarium industry provides a hobby, luxury, or educational good to consumers. Consumption is often for private
aesthetic enjoyment, but aquaria can also function as a symbol of prestige or as an educational endeavour. Pictured is a public aquarium
exhibit featuring hard corals, soft corals, fish, and various invertebrates. Source: Photograph by T. Bayly. Reproduced under the Creative
Commons Attribution Share Alike license, CC‐BY‐SA 2.0.
at a comparable frequency to luxury sport car owner- Aquaculture in the Aquarium Industry 589
ship among the population.
of custody and are subjected to routine maintenance of
It is estimated that 90–96% of freshwater fishes traded their aquaria. This is also, due in part, to the shorter
are cultured and the others are wild‐captured (Monticini, chain of custody that aquaculture organisms generally
2010). In contrast, it is estimated that only 1–10% of pass through, compared to wild‐caught organisms,
marine fishes traded originate from aquaculture before reaching the end consumer (Figure 26.2). Cultured
(Moorhead and Zeng, 2010). Considering wild‐capture organisms are generally weaned onto an inert (i.e., pellet
and aquaculture production for the aquarium industry, or flake) diet during the aquaculture production process
over 100 countries are involved in the supply. Countries and are suggested to be more willing to accept aquarium
such as Thailand, Indonesia, China, Malaysia and Japan foods than wild‐caught organisms. While such claims
have long specialised in the aquaculture of freshwater follow logical rationale, there is a lack of scientific studies
aquarium fishes. However, global increases in transporta- comparing cultured and wild organism physiology, particu-
tion expenses have resulted in production centres moving larly in relation to the aquarium industry.
closer to major markets, with domestic aquaculture (i.e.,
aquaculture occurring within the country of consump- 26.3.2 Ethically Responsible
tion) being more frequent. European markets are increas- The capture of wild organisms for private entertainment
ingly turning to producers in the Czech Republic, Spain, value is a contentious issue in the current social climate
Israel, Belgium and the Netherlands for supplies of of modern society. There is increasing criticism of the
freshwater aquarium fishes. Similarly, both the USA and aquarium industry for removing organisms from natural
Australia have seen an increase in domestic aquaculture, habitats and confining them in the restricting space of a
with Florida now containing 200 farms and raising more private aquarium. This sentiment stems from the fact
than 800 freshwater fish strains (Monticini, 2010). that many organisms, particularly marine fishes, often
have vast home ranges in their natural environments.
26.3 The Need for Aquaculture For example, surgeon fishes (Acanthuridae) are a popu-
in the Aquarium Industry lar group of fishes in the marine aquarium industry. The
natural home ranges of surgeon fishes are reported to
The aquaculture of organisms for the aquarium industry range from 50 m to 5 km, which is grossly in excess of
is often viewed in competition with wild‐capture. While the space provided by typical home aquaria (generally
in some cases there is an overlap of species supplied to less than 400 L). These characteristics are shared by
the aquarium industry by both sources, there are several other marine, as well as freshwater, fishes.
considerations necessitating further development of
aquaculture within this industry. Many of the perceived The second notion of ethical responsibility stems from
benefits of producing aquarium organisms through the fact that wild capture of aquarium organisms, par-
aquaculture as distinct from wild‐capture are not estab- ticularly marine organisms, may involve environmentally
lished. They should be the focus of future research. It is destructive techniques. This includes, but is not limited
important to address these perceptions to obtain an to, dispersal of anaesthetising agents, such as sodium
understanding of the market appeal, production targets, cyanide, to stun fish for collection, which kills non‐target
and future role of aquaculture in the aquarium industry. organisms. Such chemicals are also known to impair the
physiology of collected organisms and often lead to
26.3.1 Suitability for Life in Captivity delayed mortality that may occur further along the chain
It is generally perceived that cultured organisms are of custody. The extent to which such practices are
more suited to life in captivity than wild‐caught organ- employed in the collection of organisms for the aquar-
isms. This stems from the fact that cultured organisms ium industry is largely unknown. Aquaculture offers a
are produced in a captive environment similar to the product in which the buyer can have a high degree of
environments afforded by public and private aquaria. confidence that such practices were not employed in
With exposure to human contact from an early life stage, bringing the fish to market.
cultured organisms, particularly fishes, are claimed to be
more socially engaging and less easily frightened than 26.3.3 Biosecurity
wild‐caught specimens. Following this reasoning, it is The aquarium industry presents serious biosecurity con-
believed cultured organisms experience less stress than cerns given the diversity of species traded, the range of
wild‐caught organisms as they move through the chain habitats and locations from which organisms are sourced,
and the large volume of international trade. This encom-
passes both the introduction of disease and the potential
for aquatic organisms to become established outside
590 Aquaculture
(a)
Domestic aquaculture
Aquaculture Export Import Retail Consumer
(b)
Village 2nd Buyer
Fisher Buyer Export Import Retail Consumer
Figure 26.2 The chain of custody for (a) aquaculture organisms and (b) wild‐caught organisms in the aquarium industry. Aquaculture,
particularly domestic aquaculture, results in a much‐reduced chain of custody for traded organisms compared to those sourced from
wild‐capture. Source: Reproduced with permission from Thane Militz.
their natural distribution. The intentional release or the outside environment. Such practices are typical for
escape of aquatic organisms as a result of the aquarium inland hatcheries using indoor tank‐based culture, but
industry has been identified to contribute to some of the become increasingly difficult to enforce the more closely
most severe aquatic bio‐invasions. The introduction of production is tied to the outside environment. Pond pro-
the Pacific lionfish (Pterois volitans) into the Caribbean duction or sea ranching of aquarium organisms greatly
and the near global establishment of the guppy (Poecilia limits the capacity for pathogen control (Figure 26.3). At
reticulata) in freshwater habitats are largely linked to present, the majority of aquarium industry aquaculture
the release of unwanted aquarium specimens by end production originates from countries without the neces-
consumers. These examples are only two amongst many. sary infrastructure, training, or education to operate
bio‐secure facilities. Given the high density of organisms
Aquaculture offers the capacity to manipulate organism inherent in the production process, this can cause dis-
development, yielding mono‐sex, or sterile individuals ease to amplify and aquaculture is currently implicated
with certain procedures. By supplying the aquarium in contributing to, rather than mitigating, the invasion
industry with mono‐sex or sterile organisms the threat risks of pathogens and commensal fauna (Whittington
of bio‐invasions can be greatly reduced. However, the and Chong, 2007).
methods used in producing mono‐sex or sterile organisms
in the food production sector have yet to be trialled in 26.3.4 Supporting Research
the aquarium industry. This aspect merits further research The knowledge gleaned from commercial and private
as the concerns of aquarium‐related bio‐invasions aquaculture production of aquarium organisms and
become increasingly realised. their contributions to science is often under‐represented.
Their work often lays the fundamentals for scientific
With appropriate management, aquaculture can also understanding of the early life history of aquatic species
reduce the risk of introducing foreign aquatic diseases and contributes to the collective understanding of
through the trade of aquarium organisms. For this
benefit to be realized, aquaculture facilities must operate
in a bio‐secure manner that separates production from
Aquaculture in the Aquarium Industry 591
Figure 26.3 Sea cage aquarium aquaculture operation in Ambon, Indonesia. This operation has a land‐based hatchery with sea cages
being used for conditioning broodstock and grow‐out of juveniles. Novel strains of amphiprionin species and non‐indigenous fishes were
cultured in this manner, including clownfish (Amphiprion percula) and Banggai Cardinal fish (Pterapogon kauderni). Source: Reproduced
with permission from A. Basford.
aquatic environments. The dissemination of collected from a single cohort. This minimises the potential bias
knowledge between the aquarium industry aquaculture from use of wild‐caught organisms where genetic‐
sector and professional academics has supported signifi- relatedness and early life history are often unknown.
cant advances in captive husbandry and culture. Many of Culturing organisms under different environmental
the culture techniques employed by commercial aqua- conditions is a critical research component to evaluating
culture operations for aquarium fishes were originally anthropogenic impacts and climatic change on tropical
pioneered by aquarium hobbyists. ecosystems.
As participants in the aquarium industry, public 26.3.5 Less Pressure on Wild Stocks
aquariums present a unique opportunity to facilitate In order for aquaculture to successfully lessen pressure
research and educate the general populace about on wild stocks, two things must happen:
aquatic organisms. Public aquariums can have conser- 1) the species must have commercially developed
vation, educational, and scientific impacts on visitors
(Figure 26.1). Aquaculture offers the capacity for public production methods; and
aquariums to showcase the larval or juvenile life stages 2) the cost of aquaculture production must be compara-
of aquatic organisms to visitors and to demonstrate the
role of aquaculture in conservation (section 26.3.6) and ble to that of wild‐caught specimens.
aquatic organism production. When wild stocks are abundant, wild‐capture of an
organism is relatively easy and transportation costs are
Numerous scientific studies make use of cultured low. It is generally cheaper for organism supply to
organisms to gleam understanding of natural aquatic originate from the field rather than aquaculture. With
systems, their inhabitants, anthropogenic impacts, and this scenario, aquaculture production will be limited to
climatic change. Given the overlap in species cultured low numbers targeting the niche market of environmen-
for the aquarium industry and those inhabiting biodi- tally conscious consumers willing to pay a price premium
verse tropical ecosystems, scientists often make use of for cultured specimens. However, there is often a point
industry‐developed culture techniques or the cultured where, due to a decrease in wild stock abundance,
organisms directly. Cultured organisms have a known
life history and experimental individuals can be drawn
592 Aquaculture
Production costs of giant clams (Tridacninae), seahorses (Syngnathidae),
and hard corals (Scleractinia) allows for a sustainable and
legal supply of these organisms, given their listing under
CITES Appendix II. In addition to supplying the aquar-
ium industry with cultured organisms, aquaculture offers
the opportunity for restocking natural populations that
have been depleted or eliminated. Successful examples
include barbs (Barbus) being reintroduced in Sri Lanka
and giant clams being reintroduced to some Pacific
islands.
Wild stock abundance 26.3.7 Novel Strains
Figure 26.4 Cost of bringing aquarium organisms to market in A novel strain is best defined as an aquaculture‐pro-
relation to their wild stock abundance. The cost of wild‐caught duced variant of natural phenotypes, produced through
organisms (blue line) will inevitably increase as wild populations selective breeding, genetic manipulation, or dietary
decline. In contrast, the cost of aquaculture organisms (red line) is alteration(s).
generally independent of wild population abundance. At the
point of cost equivalence (green arrow) supply has the capacity to Aquaculture can provide the opportunity for two sepa-
switch from wild harvest to aquaculture. Source: Reproduced with rate species with the capacity to interbreed, to hybridise,
permission from Thane Militz. and produce offspring. While ecological or geographical
isolation would prevent such hybridisation in nature, arti-
difficulties in obtaining specimens, or an increase in trans- ficially manipulating broodstock encounters can produce
portation expenses, that the cost of harvest becomes com- new hybrid strains in some cases. The indigo dottyback
parable to the cost of aquaculture production (Figure 26.4). (Pseudochromis fridmani x P. sankeyi) is a novel strain in
At the point of cost equivalence, supply has the capacity to the marine aquarium industry. This pairing results in a
switch from wild harvest to aquaculture (Figure 26.4). The hybrid with intermediate phenotypic characteristics of
capacity for aquaculture to lessen pressure on wild stocks of the two parent species that has an aesthetic appeal to
aquatic organisms at this point abides by the rationale that consumers resulting in continued demand. There are
for every organism cultured, one less organism will be similarly many freshwater, hybrid novel strains, particularly
sourced from the field. This is likely to be true except where within the Cichlidae and Poeciliidae families (Figure 26.5).
the promotional activities of the aquaculture sector lead to
an overall increase in organism demand that cannot be Novel strains can also be developed through intensive
matched by aquaculture production alone. trait selection. All organisms have phenotypic diversity;
26.3.6 Species Conservation Figure 26.5 A ‘Flowerhorn’ fish at the Asian Fish exhibition, 2009
Aquaculture provides the opportunity for organisms sup- Agriculture Fair, Paris. They are highly-prized hybrids of the
plying the aquarium industry to originate entirely from freshwater fish Amphilophus labiatus X A. trimaculatus and an
captivity. This is the basis for species survival programs aquaculture industry has been involved in developing a variety of
and the capacity for the aquarium industry to function as strains: Zhen Zhu, Golden Monkey, Golden Base (Faders), King
an ‘Aquarium Ark’ in the context of preserving natural Kamfa, etc. ‘Flowerhorn’ fish may sell for more than USD 1000.
diversity. The Asian arowana (Scleropages formosus), bala Source: Reproduced under the terms of the Creative Commons
shark (Balantiocheilos melanopterus), and pygmy loach Attribution share licence, CC BY-SA 3.0.
(Ambastaia sidthimunki) are all endangered freshwater
fishes in demand by the aquarium industry and have been
conserved through aquaculture production (Ng and Tan,
1997. In the marine sector, aquaculture supply of the ban-
gai cardinalfish (Pterapogon kauderni) helps mitigate the
continuing unregulated wild collection of this endan-
gered species. Aquaculture production also plays a key
role in supplying species listed on CITES Appendices I
and II to the aquarium industry. Aquaculture production
however natural selection often limits frequent encoun- Aquaculture in the Aquarium Industry 593
ters with the extremity of this diversity in nature. The
aquaculture environment generally negates natural known to impact phenotype expressions. This method of
selection and often broadens the spectrum of pheno- phenotype manipulation allows the phenotype to be
typic diversity that can be observed. Many of the atypical maintained permanently. By limiting the highly unsatu-
phenotypes are culled as part of the quality‐control rated fatty acids (HUFA) available to developing clown-
process, but occasionally an aesthetically‐attractive phe- fishes, an increased frequency of juvenile fishes will
notype will present itself. Preserving such specimens as develop stripe pattern aberrations.
future broodstock and pairing broodstock with similar
traits can yield an increase in the desired phenotype Genetically‐modified organisms are the most recent
among the subsequent generations of offspring. development in novel strain production for the aquar-
Repeating this process of selection, often encompassing ium industry. By genetically modifying organisms the
a high degree of inbreeding, can yield novel phenotypes genetic code of the resulting strain is allowed to be
of high aesthetic appeal to the aquarium industry. This patented and trademarked by the producing company.
methodology has been used to produce an array of novel The first genetically‐modified organisms for the marine
strains for both the freshwater and marine industries. aquarium trade became publicly available in 2003. This
Well-known examples include guppies (Poecilia reticu was the GloFish®, a zebrafish (Danio rerio) with genes
lata), having 51 fin and colour‐strain variants, and fight- for a green fluorescent protein, originally extracted from
ing fish (Betta splendens), having 17 colour strains and jellyfish, integrated into the zebrafish’s genome causing
8 fin types (Figure 26.6). In the marine sector many of the fish to brightly fluoresce. Further development of
the recently emerged ‘designer’ strains of clownfish this technique has yielded orange, blue, purple, and red
(Amphiprioninae) have been produced in this manner. fluorescing zebrafish as well as tetra (Gymnocorymbus
ternetzi) and tiger barb (Puntius tetrazona) GloFish®
A third method of producing novel strains occurs (Fig. 7.13).
from dietary alterations. In some cases, phenotype
manipulation is achieved using diet supplements. The Novel strains are of high importance to the economic
use of astaxanthin, a colourful, lipid‐soluble pigment, development of aquaculture for the aquarium industry.
incorporated into diets of aquarium fishes is used to By producing novel strains, aquaculture operations cre-
increase the saturation of red or orange pigmentation. ate a product for which it is the exclusive source. This
However, the longevity of phenotype manipulation in provides aquaculture with a competitive niche in supply
this manner is generally temporary, persisting only as for the aquarium industry. However, the success of novel
long as the diet supplement is supplied and for a short strains largely depends on consumer acceptance and
time thereafter. Dietary alterations targeting the early whether consumer preference favours a novel strain over
development of organisms, such as larval fishes, are also the wild‐type organism. While there has long been
acceptance of novel strains in the freshwater aquarium
industry, novel strains have only recently obtained con-
sumer acceptance in the marine aquarium industry.
Figure 26.6 Selectively bred for bright colours and long fins, this 26.4 Aquaculture of Tropical
male Siamese fighter fish (Betta splendens) is shown with its Freshwater Organisms
bubble nest. Source: Photograph by ErgoSum88. Reproduced
under the terms of the Creative Commons Attribution share The vast majority of freshwater aquarium organisms
licence, CC BY-SA 3.0. originate from aquaculture. The type and size of the
business varies greatly in different regions and often
reflects the socio‐economic environment in which the
business is found. Within Asia and South America, farms
can vary in size from small backyard set‐ups to large
pond farms, but they are generally low technology
ventures. In Singapore, businesses are small and often
family owned and operated, or they are grouped into
agro‐technology parks by government agencies. In the
poorer areas of the Philippines and Indonesia, basic
aquarium aquaculture businesses operate even in areas
where sanitation and general living conditions are poor.
In developed countries such as the USA, culture tends to
occur at a more intensive level through high‐capacity
594 Aquaculture duction in the ponds may partly or completely satisfy the
feeding requirements of larval and juvenile fishes; how-
aquaculture companies. However, in Europe and ever, some degree of supplemental feeding may occur.
Australia the aquarium fish trade is sustained by a few
intensive commercial businesses and various individuals Harvest typically involves batch harvesting. Where
or groups of amateur and professional breeders that sell aquatic plants are produced, these can be removed by
to wholesalers and retailers. hand. In the case of fishes and invertebrates, common
harvesting methods are traps or seine nets. The least
In many instances, the key to success for producers is stressful and damaging harvest method will ensure good
variety. Aquaculture operations that are able to provide survival and minimise aesthetic impairment, which
a larger variety of cultured species and novel strains will affects sales value. Catchment sumps in ponds are also
often be able to sell a larger number of fishes. Given the used to concentrate fish when the pond is drained,
diversity of the trade, wholesalers want to capture the making harvesting easier. After harvest from ponds, fish
greatest amount of diversity in the fewest business are often kept in holding tanks with high‐quality water
transactions as possible. This business demand is in and treated for parasites and disease, inspected and
contrast to the traditional mono‐culture production sorted, and purged prior to transport.
focus that characterises food‐production aquaculture
with aquarium farms culturing many different species Cage culture within ponds can also be employed for
and novel strains. Thus, a given farm can contain organ- the production of fishes. This method enables farmers
isms that vary not only in appearance and value, but also to benefit from the natural productivity of ponds, harvest
water quality requirements, nutrition, and mode of more easily, culture multiple species or cohorts of dif-
reproduction. Aquarium aquaculture can therefore ferent size or age in the one pond, or confine broodstock
often require a higher level of knowledge, expertise, and while allowing fry to swim freely into the open pond.
management ability compared to other types of Additional labour is needed to control biofouling on
aquaculture. cages; however, particularly for producers with large
ponds, cage culture increases their ability to diversify
Freshwater aquarium species can be cultured in ponds, production, which is an important advantage in aquarium
pond cages, raceways, and enclosed tanks and aquaria. aquaculture.
Yields at harvest‐time may vary greatly depending on
the culture methods and techniques used. In general, Pond culture is one of the cheapest methods for pro-
facilities for the production of aquarium fish are small ducing aquarium organisms owing to the relatively low
compared to food fish production facilities, with lower level of labour required for maintenance and low inputs.
stocking densities during larval rearing and grow‐out. Until recently, pond culture has been the only effective
However, production can resemble semi‐intensive food method of rearing fish larvae with a small mouth gape,
fish production, with stocking densities of some aquar- such as those of the dwarf gourami (Trichogaster lalius).
ium fish species matching that of food species. However, there is little control over the environmental
parameters within ponds and there are inherent difficul-
26.4.1 Culture Systems ties in controlling water quality. Ponds are also more sus-
ceptible to the entry of pests, such as weeds, parasites,
26.4.1.1 Pond Culture pathogens, and predators, which can reduce production
Pond culture of freshwater aquarium organisms is glob- output, decrease fish quality, and make harvest difficult.
ally the most popular technique for commercial produc- The use of ponds is therefore limited to areas with satis-
tion. A number of freshwater aquarium fishes, factory soil conditions, environmental parameters within
invertebrates, and aquatic plants are commercially pro- the tolerance range of the organisms being farmed and a
duced using pond culture. Ponds can vary in size, type source of good quality water. Additionally, with increas-
(earthen or lined) and cost. In Florida for example, the ing latitude, farming regions are subject to more varied
majority of ponds are water‐table ponds constructed on environmental conditions with changes in season.
a sandy loam, and have an average size of roughly Organisms that respond to environmental cues as a part
8 × 24 m. In China, ponds are often located near lakes or of their reproductive cycle, may cease breeding for parts
rivers, with ponds as large as 20 m × 60 m to several acres of the year, limiting farm production. For example, gold-
in size. fish pond culture in China is restricted to two spawning
seasons per year, in autumn and spring. Goldfish fry are
Organisms are generally produced using an extensive also very sensitive to temperature change in the first few
culture method, with low stocking densities. Ponds are weeks after hatching which can result in heavy losses of
initially dried, cleared of vegetation, and then filled. fry raised in ponds. Growth rates will also decrease as
Depending on the organism being produced, fertiliser temperature drops. For tropical aquarium species, the
may be added to promote plant growth or, in the case of majority of pond culture is restricted to tropical regions.
fishes, to promote primary productivity and subsequent
zooplankton growth (sections 2.2.1 and 9.7). Natural pro-
26.4.1.2 Outdoor Raceway and Tank Culture Aquaculture in the Aquarium Industry 595
Outdoor systems of large tanks and raceways are also
commonly used for culture of freshwater ornamental no research efforts for optimising production techniques
fish, invertebrates, and aquatic plants. These culture for many traded species. As such, a number of technolo-
structures can be constructed of plywood lined with gies and techniques commonly used in food‐fish aquacul-
canvas, high‐density polyethylene or concrete. They ture have been adapted for the production of freshwater
typically range from several hundred to thousands of aquarium fishes until such a time that species‐specific
litres in volume. In some cases, tanks may be sheltered to protocols are developed.
minimise algal growth while some production methods
take advantage of sunlight to fuel plant growth or pri- This section aims to provide an introductory over-
mary production and zooplankton blooms. Tanks and view of the common commercial production methods
raceways may be fertilised in much the same way as for freshwater aquarium fishes. This section, however,
ponds, or seeded with water from ponds with algal avoids detailing species‐specific husbandry requirements
blooms. The stocking densities tend to be higher than which can readily be obtained from aquarium fish care
pond culture, with higher levels of supplemental feeding. guides, available both online, and in print.
These systems may operate as static, flow‐through,
semi‐recirculating or recirculating systems with their The aquaculture production process starts with brood-
own biological filtration systems. Like ponds, however, stock selection. There are two sources from which
farms with large tanks and raceways tend to be confined broodstock can be obtained: wild‐caught or aquaculture.
to areas that suit the environmental tolerances of the Wild broodstock are generally considered advantageous
culture species, and may be subject to variable produc- as they bring new genetic diversity into the captive popu-
tion according to environmental seasonality. lation of the aquarium industry. This offers the potential
to develop new novel strains. However, disadvantages of
26.4.1.3 Indoor Tank Culture wild broodstock include lack of knowledge of broodstock
Completing the production cycle of aquarium organ- spawning history, potential difficulties in adapting to
isms entirely indoors allows maximum control of envi- captivity and the potential for introducing disease to
ronmental conditions, disease, feeding and stocking the facility. There are some exceptions where broodstock
densities during culture. Due to the high level of envi- of certain species can only be obtained from cultured
ronmental control, indoor tank culture can occur in sources. This is often due to declining populations in the
regions outside the range of environmental tolerances wild, an absence of aquarium collectors currently operat-
for the organisms being produced. This allows aquarium ing within the fishes’ natural distribution or where the
aquaculture facilities to be located close to major markets source country has banned collection.
in temperate regions. However, due to the high level of
environmental control that necessitates greater technol- Cultured organisms will also be used as broodstock
ogy (e.g., recirculating filtration systems) and infrastruc- when the production aims to further develop an exist-
ture investments the operating costs are relatively high. ing novel strain. Often this entails selecting and rearing
To be financially successful, indoor tank culture typically the most desired individuals from production for use as
produces organisms at high density in small water the next generation of broodstock. However, when
volumes generally less than 1000 litres. sourcing cultured broodstock from outside the farm,
care must be taken to ensure broodstock are obtained
Such systems place an emphasis on production of from a reputable source that can provide details of the
higher value organisms. Indoor production is commonly genetic history. This is done to prevent the potential for
used to raise fish that are difficult to breed or have spe- inbreeding.
cific larval‐rearing requirements. Pond farmers may also
make use of indoor systems to achieve year‐round Identifying male and female fish is quite easy for most
spawning of broodstock prior to stocking ponds for freshwater aquarium fishes, given the frequent occur-
grow‐out; they may also collect young from outdoor rence of sexual dimorphism. Male and female fish often
breeding ponds and rear them indoors. differ in colour, body size, fin morphology and other
morphological traits. When sexing immature fishes or
26.4.2 Freshwater Fishes species with limited dimorphism it is often necessary to
There are approximately 500 strains of tropical freshwater examine the fish’s vent. The vent is the external opening
fish that are commonly cultured for the aquarium indus- to the digestive, urinary and reproductive tracts, located
try (Monticini, 2010). With the variety and diversity of anterior to the anal fin. The genital papilla of the repro-
fish species being cultured, it is surprising that there are ductive tract for females is generally wider than that of
males. Where a female fish is gravid, the genital papilla
can even be observed protruding slightly.
Successful spawning is often achieved in response to
external environmental stimuli working collectively to
trigger the release of gonadotropin‐releasing hormones
(GnRH) by the hypothalamus. In response to GnRH the
596 Aquaculture origin they are a universal first feed for freshwater aquar-
ium fishes. This is largely due to the convenience of
pituitary gland then produces and releases gonadotropin their culture and reduced risk of introducing pathogens.
hormones (GtH). Successful ovulation in females is Given that Artemia nauplii can only tolerate freshwater
dependent on the release of GtH from the pituitary for two to three hours, regular replacement of the live
(Figure 6.1). For most freshwater aquarium fishes, main- food source is needed. Success with widespread use of
taining sexually mature fish with a high protein diet, Artemia is because freshwater fish do not require the
optimal water quality, long photo‐periods, and an long chain HUFA required by marine fishes (Chapter 8,
appropriate sex ratio is enough to encourage final oocyte section 8.4.2). The capacity for freshwater fishes to syn-
maturation and to elicit ovulation. However, for some thesise HUFA from linolenic acid (18:3‐n‐3) greatly
species there has been limited or no success in eliciting simplifies the nutritional requirements in culture. Given
final oocyte maturation. Redtail (Labeo bicolor) and that most Artemia strains contain linolenic acid at rela-
rainbow ‘sharks’ (Epalzeorhyncus frenatus), several spe- tively high concentrations compared to other fatty acids,
cies of loaches (Botiidae) and many species of catfishes no enrichment (section 9.2.14) is required. As an alterna-
(e.g., Auchenipteridae) and cyprinids require hormonal tive to the supply of feed or where Artemia nauplii are
manipulation to reach final oocyte maturation and ovu- too large as an initial prey item, outdoor culture methods
lation under captive conditions. Following techniques may be used that leave the fry to feed on natural freshwater
for hormone‐induced spawning of food fish (section 6.2.1) zooplankton blooms.
the culture of these species is feasible.
There is a major difference between food fish and
Spawning and egg care, are highly diverse but conform aquarium fish aquaculture in the highly‐reduced grow‐
to one of five major reproductive strategies: out period of the later. Purchasers of aquarium fish
●● live‐bearing; typically want to watch their fish grow in their private
●● mouth‐brooding; aquaria creating a demand for juvenile fishes. Further
●● substrate spawning; more, given that the end product is sold live, fishes
●● bubble nesting; and must be transported to market in a volume of water
●● egg scattering. making the sale of smaller fishes further advantageous
The method of egg care employed by a species has the in reducing shipping costs. A suitable market size can
greatest impact on the culture methods utilised and each generally be achieved within two to six months after
of these reproductive strategies is discussed at the end of hatching for most cultured species. This results in a
this section. In short, these different reproductive strate- rapid production cycle.
gies reflect differences in requirements for spawning, the
number of offspring produced, the size of hatched larvae 26.4.2.1 Live‐bearers
and the availability of endogenous yolk reserves. Among freshwater aquarium fishes the live‐bearing
reproductive strategy is most commonly encountered in
The early development of freshwater fishes is charac- the family Poeciliidae of which the most well‐known gen-
terised by three phases: era are Poecilia, guppies and mollies, and Xiphophorus,
●● the embryonic phase; swordtails and platies. Other live‐bearing fishes include
●● larval phase; and some members of the family Hemiramphidae, Goodeidae,
●● fry phase. and Anablepidae, although these are less demanded by
The embryonic phase starts with the insemination of the the aquarium industry.
egg and concludes with hatching. The larval phase begins
with hatching and lasts until the end of metamorphosis. Live‐bearing fishes retain eggs inside the body and give
It is during metamorphosis that pigmentation, scales, birth to live, free‐swimming juveniles. The reproductive
the lateral line, and other organs develop. With the con- strategy varies in the degree of maternal support given to
clusion of metamorphosis the juvenile fish are often developing larvae. Some are strictly ovoviviparous where
regarded as ‘fry’ and begin deriving their nutrition the internally‐incubated eggs contain sufficient yolk to
exogenously. Some species do not show remarkable support complete embryonic development. Other
metamorphosis with fish passing from larval to fry species are viviparous, with a majority of nutrients being
phase directly. provided to the eggs through the maternal blood supply
via structures analogous to the mammalian placenta.
The larvae of most freshwater fishes cultured for the Following spawning, gestation periods can range from
aquarium industry can sustain themselves on endoge- three to eight weeks depending on the species. Given the
nous yolk reserves from hatching until the fry phase. high level of parental investment into the developing
At this point, the fry are typically large enough to begin embryos, live‐bearers produce only a small number of
accepting finely ground inert food particles or newly juveniles (ranging from 2 to 200 fry).
hatched Artemia. Despite Artemia being of seawater
This reproductive strategy yields highly developed Aquaculture in the Aquarium Industry 597
juveniles capable of accepting inert food particles and
large prey items at birth. As such, juvenile care differs both parents (bi‐parental mouth‐brooding). Paternal
little from adult care. The domestication of live‐bearers mouth‐brooders include the osteoglossids and osphrone-
has been very successful in a short period of time mids. Among the cichlids, paternal mouth‐brooding is
because fishes can be offered foods rich in proteins and relatively rare with most species in demand for the
vitamins, foods rarely or never available in the fishes’ aquarium industry engaging in maternal or bi‐parental
natural environments. The higher nutritional content of mouth‐brooding.
aquaculture diets has led to unnaturally high reproduc-
tive rates and survival of juveniles. In nature the poeciliid In paternal mouth‐brooding the male fertilises the
species prefer environments with hard, alkaline water. eggs and then collects them in his mouth, holding onto
Similar water conditions should be replicated in the them until they hatch. During this time the male will
culture environment. either not feed or feed less often than he otherwise
would. The parent fish will also increase territorial
The most important advantage of live‐bearing to displays and aggressive behaviour to help protect the
the aquaculture production process is that one single brood. This places significant physiological stress on
fertilised female is enough to establish a subsequent the mouth‐brooding fish, typically resulting in weight
generation. This and short generation times of only one loss. Following hatching the male will require a period
to two years facilitates ease of selective breeding and has of re‐conditioning to restore energy reserves, before
resulted in the production of numerous novel strains. further participation in spawning can occur. In mater-
For many species, novel strains are more frequently nal mouth‐brooding the same process occurs but with
encountered in the industry than strains resembling the the male fertilising the eggs once they are in the
wild‐type species. Hybrid novel strains of the poeciliid female’s mouth.
species are also commonly cultured.
Parental care typically ceases when eggs hatch and the
Production of live‐bearers occurs across all culture larvae become free‐swimming juveniles; however, exten-
systems addressed above (section 26.4.1). However, sion of brood care to juvenile fish may be afforded where
some novel strains require indoor culture facilities for juvenile fish can return to their parent’s mouth when
production as the novelty factor of their phenotype, frightened. This high level of parental care generally
such as elaborate fins, greatly impairs survival in results in high survivorship of fertilised eggs but limits
more natural culture systems. In indoor culture, a the total number of eggs produced in each spawning.
high‐protein inert diet supplemented with Artemia Most cichlid mouth‐brooders have clutch sizes of only 5
nauplii helps intensify production and maximise colour to 100 eggs. This combined with the high aggression of
intensity. the parent fish limits the value of stocking a large num-
ber of broodstock into a pond or large aquarium. Rather
Where outdoor culture is employed, the fishes’ diet small populations of a single male and one or more
largely consists of natural foods: filamentous algae, zoo- females are maintained in smaller culture vessels. This
plankton, and mosquito larvae. Live‐bearers are not renders mouth‐brooders particularly well suited for
monogamous and so are stocked into breeding tanks as indoor tank culture systems. A high‐protein inert diet
groups, usually with male‐female ratios varying between supplemented with Artemia nauplii is usually suitable
1:1 to 1:5. Stocking densities in ponds can vary greatly, for juvenile fish. Given the large size of eggs, reflecting
with anywhere between 50 to 1000 of the best brood- large endogenous yolk reserves, juvenile fish are mor-
stock specimens being released into a single pond. Ponds phologically advanced at hatching.
are then typically harvested after a period of 6–7 months.
This harvest will contain multiple generations of fishes, Production of novel strains of mouth‐brooding fishes
and juveniles too small for resale can be held back until lags behind the development in live‐bearers owing to a
market size. longer generation time and consumer preference for
wild‐type strains. The exception to this is the high‐end,
26.4.2.2 Mouth‐brooders niche market for novel strains of arowana (Scleropages
Among freshwater aquarium fishes the mouth‐brooding species).
reproductive strategy is most commonly encountered
among members of the family Cichlidae, commonly 26.4.2.3 Substrate Spawners
known as cichlids. Mouth‐brooding is also seen in a few Similar to mouth‐brooding, the substrate spawning
genera of Osphronemidae (gouramis) and Osteoglossidae reproductive strategy is common among members of
(arowanas) that are cultured for the aquarium industry. the family Cichlidae. It is also common among species
Mouth‐brooding can be performed by the male (paternal of Loricariidae, commonly known as the ‘L‐number’
mouth‐brooding), female (maternal mouth‐brooding) or catfishes. The natural substrates to which eggs are
deposited vary among species but typically include
earthen caves, rock crevices, submerged wood, or plant
598 Aquaculture parent’s mucosal layer. Thus, it is important to allow off-
spring and parents of these fish to coexist until the fry
leaves. In culture these natural spawning substrates are begin accepting Artemia.
replicated with PVC piping, clay hides, bathroom tiles or
rocks. Eggs are deposited one by one, often close to each Novel strains are common among both Symphysodon
other, and are then fertilised by the male. Large spawns and Pterophyllum species. This encompasses different
can reach in excess of 1000 eggs, though smaller spawns strains of colouration and fins. There are also several
of less than 100 eggs are typical of some species. hybrid novel strains among cichlid substrate spawners,
with some crosses capable of reproduction.
Among the loricariid species brood care is provided
exclusively by the male, while for the cichlid species 26.4.2.4 Bubble‐nest Builders
brood care is provided by the male or both parent fish, Bubble nests, also called foam nests, are a reproductive
depending on the species. Brood care typically involves strategy that involves creation of a floating mass of bub-
protecting the eggs from predators, often involving dis- bles blown with an oral secretion. The nests are created
plays of aggression among the cichlid species, fanning as a place for fertilised eggs to be deposited while devel-
the eggs to remove debris, and consumption of eggs that oping until hatching. In the aquarium industry species in
were either unfertilised or damaged. Eggs of both the the family Osphronemidae, including gouramis and
loricariid and cichlid substrate spawners typically hatch fighting fish, are the primary bubble‐nest builders to be
in three to ten days. The relatively small clutch size and cultured.
aggressive behaviours of the parent fish renders substrate
spawners well suited for indoor tank culture systems The bubble nests are built by the male, and nest size,
(Figure 26.7). Broodstock are either maintained as breed- position and shape is dependent on the species. They are
ing pairs or harems of one male and several females. often built in and among aquatic plants at the water’s sur-
face. After spawning, eggs either float up to the bubble
Parental care typically extends beyond hatching in the nest or are carried there (in the case of negatively buoyant
form of protection from potential predators. Juvenile eggs) and actively deposited into the nest by the parents
fish either school with the parents or remain in the vicin- (Figure 26.9). Anywhere from 50 to 1000 eggs may be
ity of the spawning hide for days to weeks. In many cases spawned depending on the species. Nest care is under-
juvenile fish can be fed the same diet provided to the taken by the male fish that aggressively defends the nest,
adult fish. Artemia nauplii are provided as a food source and maintains it through continual production of bubbles
for smaller larvae (such as with the freshwater angel and retrieval of any eggs that detach from the nest.
fishes, Pterophyllum species) in addition to inert feeds.
Species of the genus Symphysodon, commonly traded as Hatching occurs one or two days following spawning
discus (Figure 26.8), have unique larval care require- with parental protection being afforded for several days
ments in that newly-hatched fry initially feed on the
Figure 26.7 Parent Jewel ciclids
(Hemichromis species) guarding eggs and
larvae. Source: Photograph by Ventus55.
Reproduced under the terms of the
Creative Commons Attribution share
licence, CC BY-SA 3.0.
Figure 26.8 A freshwater substrate spawner, discus (Symphysodon Aquaculture in the Aquarium Industry 599
aequifasciatus) is typically cultured by maintaining pairs of
broodstock in indoor tank culture systems. Egg care is left entirely more frequently produced than wild‐type strains. Bright
to the broodstock and is conducted by both male and female fish. colour varieties of the dwarf gourami (Trichogaster
These fish have made use of a PVC pipe as a spawning substrate lalius) have also been developed and are very popular
for their egg mass. Source: Photograph by Joe Mackereth. within the aquarium industry.
Reproduced under the terms of the Creative Commons
Attribution share licence, CC BY-SA 3.0. 26.4.2.5 Egg Scatterers
Egg scattering is the common reproductive mode of
Figure 26.9 Larvae in the bubble nest of a male Siamese fighting many freshwater aquarium fishes. Species in the families
fish (Betta splendens). The male will be below the nest returning Botiidae (loaches), Callichthyidae (armoured catfishes),
any detached larvae. Source: Photograph by ZooFari. Reproduced Characidae (characins, tetras), Cyprinidae (carps, minnows,
under the terms of the Creative Commons Attribution share etc.), Melanotaeniidae (rainbow fish), and Aplocheilidae
licence, CC BY-SA 3.0. (killifishes) are almost all egg scatterers with a few spe-
cies of the Cichlidae as well.
or for weeks depending on the species. At hatching the
larvae continue to utilise remaining yolk reserves, but Most egg scatterers spawn continuously or with high
are generally too small to accept Artemia nauplii by the frequency (e.g., every other week), with most activity
time the endogenous yolk reserves are depleted. in the morning hours. In natural habitats, algae and
Powdered diets or zooplankton must typically be offered dense vegetation are used as spawning substrates. The
before larvae are large enough to feed on Artemia. This male and female move tightly together scattering their
renders pond and large outdoor tank culture a popular gametes over the spawning substrate. During a single
option in the production of these fish, since they can spawning a few to more than 100 eggs are released.
easily provide the dietary needs of newly hatched larvae. The eggs are small, normally ca. 1 mm. Most species
Indoor tank culture are usually only used for higher value lay eggs that are strongly‐adhesive to semi‐adhesive,
strains. which will attach to whatever substrates they contact.
Species of the genus Danio (Cyprinidae), in contrast,
There are many novel strains for the fighting fish (Betta lay negatively buoyant, non‐adhesive eggs that are
splendens) with novel varieties of colouration and fins scattered among debris.
Following spawning the parent fishes of these species
provide no further care for the eggs. In many cases the
parent fish will eat any eggs they come into contact with
after spawning.
Hatching generally takes place after three to nine days,
although some species can take over two weeks. Hatched
larvae are initially non‐swimming and make use of
endogenous yolk reserves. When the yolk sac is absorbed,
typically two to three days after hatching, the larvae
begin feeding. Many of the larvae are initially too small
to accept Artemia nauplii and require a food source with
particle sizes of 100 to 200 µm. This can be provided in
the form of powdered inert feed or freshwater
zooplankton.
Egg scatterers are typically cultured in ponds or large
outdoor tanks. This allows fish to scatter eggs among
the natural vegetation of the pond and for newly
hatched larvae to make use of natural zooplankton
stocks. Given the limited aggression of parent fish,
multiple broodstock pairs can be stocked into a pond.
Where indoor tank‐based culture methods are used,
either for the entire production cycle or to stock ponds
exclusively with juveniles for grow‐out, an artificial
spawning substrate is provided to collect the eggs. This
can be something as simple as a bristle brush. Once
eggs are collected on the brush, it is moved to a sepa-
rate rearing tank to prevent parent cannibalism of eggs
and larvae.
600 Aquaculture ceans, with eggs being attached to the pleopods of the
female shrimp (Figure 23.11). Egg clutches can range
Stocking densities among aquarium fishes are highest from 10 to more than 100 eggs depending on the species
for egg scatters. Densities as high as 10 fry/L can be and age of the female. Developing embryos undergo
achieved in intensive culture. However, it is often reported direct development and at hatch are immediately capa-
that stocking densities higher than 400 to 450 fry/1000 L ble of feeding on plants, inert feeds, and biofilms in the
result in reduced growth rates. culture tank. Harvest from the culture tank begins after
26.4.3 Invertebrates two or three months. Juvenile shrimp, roughly half of
Freshwater invertebrates commonly traded in the aquar- their adult size, are continuously removed for harvest.
ium industry include crustaceans and gastropods. The A culture tank can remain in production for up to a year
capacity to keep fishes with invertebrates is limited in after which the tank is typically drained, dried and
that crustaceans and gastropods represent part of the cleaned before restocking with new broodstock.
natural diet for many of the commonly kept freshwater
fishes. This has largely restricted the popularity of fresh- Production of dwarf shrimp deals almost exclusively
water invertebrates in the aquarium industry. However, with novel strains. Currently the market is led by Japanese
the growing popularity of ‘nano’ or desktop aquaria has grading scales that govern the value of the end products.
resulted in an increased demand for freshwater inverte- Grading scales are strain‐specific and are often based on
brates, which fill functional roles in maintaining such the intensity of colour and range of colours present on
aquaria. Some of the most demanded invertebrates are the carapace. This emergent sector of aquarium aquacul-
novel strains of dwarf shrimp (Figure 26.10). Other pop- ture is likely to further intensify and diversify given a
ular freshwater invertebrates include the mystery snails growing consumer demand.
(Pomacea) and freshwater crayfish (Procambarus).
26.4.3.1 Freshwater Dwarf Shrimps 26.4.4 Aquatic Plants
Commercial scale culture of dwarf shrimps (Neocaridina A diversity of aquatic plant species and strains are pro-
and Caridina species) is a recent development over the duced for the freshwater aquarium industry (Figure 26.11).
past five years with Indonesia supplying the aquarium Many originate from tropical regions of the world. Among
industry hundreds of thousands of shrimps every month. the most commonly encountered families are Araceae
Production is exclusively by indoor tank culture given the (lilies), Alismataceae (sword plants, etc.), Lythraceae,
strict temperature requirements for breeding (23–24 °C) Polypodiaceae (Java fern), and Hypnaceae (mosses). Most
that necessitate environmental control. Production tanks require water temperatures above 22 °C year‐round and a
range from 100 to 500 L and are initially stocked with 100 photoperiod of around 10 to 12 hours daily. Pond culture
broodstock shrimps. Sexes can be distinguished from the dominates the production of aquatic plants throughout the
presence of ovaries visible through the carapace of female tropics with greenhouses containing large raceways being
shrimp. Spawning is similar to other freshwater crusta- used in sub‐tropical regions.
Figure 26.10 The freshwater shrimp Caridina cf. cantonensis ‘Ruby Given close similarities between terrestrial and aquatic
Red’. Source: Photograph by M. Hafermann. Reproduced under the plants, many common horticulture techniques have
terms of the Creative Commons Attribution Share Alike Licence, been adapted for aquarium plant propagation. The cul-
CC BY‐SA 3.0. ture of stemmed plants (Lythraceae and others) involves
taking tip cuttings from a parent plant and replanting
them to develop roots from the leaf nodes. In response to
the removal of a cutting, the parent plant sprouts side
shoots thereby increasing the number of growing tips.
Once grown, further cuttings can be taken, bunched, and
sold as ‘bunched’ plants. Plants cultured in this manner
are grown in raceways or shallow ponds.
Making use of the formation of plantlets is another
common method of aquatic plant propagation. Smaller
Araceae, such as Cryptocoryne species, produce creep-
ing side shoots called stolons. Young plants develop at
the tip of stolons and may remain linked to the parent
plant until developing its own roots. The aquatic ferns
of the Polypodiaceae form plantlets on their leaf margin
and sporangia on the underside of leaves. In many
Alismataceae, plantlets develop among the flowers,
Figure 26.11 Potted aquatic plants for freshwater aquaria for sale Aquaculture in the Aquarium Industry 601
in Hong Kong Goldfish Market. Source: Photograph by deror_avi.
Reproduced under the terms of the Creative Commons 26.5 Aquaculture of Tropical
Attribution share licence, CC BY-SA 3.0. Marine Organisms
sprouting from the axils of the bracts. In some species, The vast majority of marine aquarium organisms origi-
detached, free‐floating leaves are capable of develop- nate from wild‐capture in coral reefs. This is largely due
ing roots and growing into plantlets. This method of to the bright colour of coral reef inhabitants and niche
propagation is only commercially employed for java specialisations that endear such organisms to consum-
fern (Polypodiaceae) where fully grown leaves are ers. With global declines in coral reef ecosystems this
removed from the mother plant, spread out on moist makes this supply of the marine aquarium trade a con-
beds, and covered with plastic. After some weeks the tentious issue. In an effort to reduce relying on field col-
leaves develop roots around their margin and new lecting, there has been research on aquaculture of marine
leaves begin to sprout. aquarium organisms. The contribution of cultured
organisms to the market is steadily increasing. Among
Simply dividing adult plants in two along the root live corals, for instance, aquaculture supply was largely
base is a crude but effective culture technique for some non‐existent before 2000, but it now accounts for roughly
species. Larger Alismataceae and Araceae, such as 10% of live coral imports into the USA (Rhyne et al.,
Anubias species, form rhizomes that can be divided. 2012). There are similar trends for coral reef fishes, giant
This involves cutting the rhizome into pieces contain- clams and live rock.
ing three or four dormant buds. These dormant buds
will then sprout leaves and roots, yielding several new There are aquaculture production centres for marine
plants within a few weeks. aquarium organisms in the USA, Europe, and throughout
the Indo‐Pacific. The different centres of production
Indoor culture is largely limited to greenhouses given tend to focus on different organisms. Within developed
the expense of providing artificial light. An exception is countries, most marine aquarium aquaculture occurs
the developing in vitro method of aquatic plant culture. within indoor or greenhouse facilities given both the lack
This involves propagating plants from tissue in more of tropical marine coastline and the high regulatory
sterile conditions indoors. The young plants obtained framework surrounding aquaculture development in
are then cultivated in a nutrient gel within a container or coastal areas. The expense and availability of seawater
plastic bag and maintained in laboratory‐style nurseries also restricts development, given the cost of coastal prop-
for ca. 8 to 12 weeks until market size. Some strains of erties allowing direct access to seawater, the expense of
higher value species may take 10 months to be produced transporting fresh seawater to an inland facility, or the
in this manner. More than 25 plant species are now being cost of artificial seawater mixes. This combined with high
cultured using these methods. The marketing benefits of costs for electricity and staffing generally limits aquacul-
such culture methods are that the plants produced are ture operations to small water volume, high intensity pro-
free of unwanted contaminants, biofouling organisms duction systems. There is typically a large investment of
and invertebrate ‘hitchhikers’ that are typically trans- technology to replicate coral reef environments ex situ
ported with aquatic plants. However, consumer accept- and minimise the requirement for water exchange. Thus,
ance of tissue culture plants requires further advancement commercial aquaculture development in developed
before such culture methods become commonplace in countries largely focuses on organisms with high demand
the trade. and on products unavailable from field collecting, such
as novel strains. The reverse is true with aquaculture
development in the Indo‐Pacific where facilities are often
unreliable, aquaculture expertise is limited, and technol-
ogy is unobtainable. This limits the capacity for intensive
aquaculture production and reduces the feasibility of
producing organisms that have hatchery requirements
for live feeds, such as coral reef fishes. However, direct
access to seawater and coral reef environments can allow
for in situ production of marine organisms for the aquar-
ium trade with minimal investment. For this reason,
developing island countries tend to produce slow‐growing
organisms with large space requirements and with mini-
mal or no hatchery phase that would be uneconomical for
developed countries to produce.
602 Aquaculture production of giant clams, live corals, and live rock. There
are exceptions, with greenhouses allowing indoor tank
At present, it is difficult for aquaculture operations to production of live corals and recent attempts at in situ
compete with wild‐capture on market price, because culture of coral reef fishes using sea cages (Figure 26.3).
aquaculture‐produced organisms are often more expen-
sive than field collected supply. This typically encourages 26.5.1 Coral Reef Fishes
producers to focus on developing novel strains or pro- Despite the aquarium industry trading close to 2000
ducing naturally rare organisms. In many cases through- species of coral reef fishes, less than 100 species are
out the Indo‐Pacific, aquaculture operations work in commercially cultured for the aquarium industry today
partnership with, or are owned by, exporters of field col- (Table 26.1). Substantial research efforts have been made
lected marine organisms. This facilitates supply of cul- to examine potential aquaculture production of coral
tured organisms to market and minimises competition reef fishes and while many successes have been claimed,
between wild‐capture and aquaculture sectors within a few (ca. 23%) have translated to commercial viability and
country.
Culture of marine aquarium species is largely limited to
indoor tank production for coral reef fishes and ex situ
Table 26.1 Families of coral reef fishes in demand for the aquarium industry and number of commercially available species
from aquaculture in 2016. Families in bold represent the top five most traded fish families.
Family (common name) Species in family Species successfully cultured Commercially available
Acanthuridae (surgeonfishes) 84 2 0
Antennariidae (frogfishes) 51 1 0
Apogonidae (cardinalfishes) 363 15 5
Balistidae (triggerfishes) 42 3 0
Blenniidae (blennies) 405 19 3
Callionymidae (dragonets) 198 7 1
Carangidae (jacks) 148 2 2
Chaetodontidae (butterflyfishes) 133 2 0
Ephippidae (batfishes) 15 4 1
Gobiidae (gobies) 1829 35 9
Grammatidae (grammas) 15 3 0
Haemulidae (grunts) 4 3
Hemiscylliidae (epaulette sharks) 135 5 2
17
Labridae (wrasses) 7 0
Microdesmidae (dartfishes) 542 2 0
Monacanthidae (filefishes) 91 5 2
Opistognathidae (jawfishes) 3 0
Ostraciidae (boxfishes) 110 1 0
Plesiopidae (assessors, bettas) 84 6 2
26
Pomacanthidae (angelfishes) 50 35 2
Pomacentridae (clownfishes, damsels) 57 16
Amphiprioninae (clownfishes only) 90 25 16
Pseudochromidae (dottybacks) 401 28
Serranidae (anthias, basslets, groupers, hamlets) 6
Siganidae (rabbitfishes) 31 9 0
Syngnathidae (seahorses, pipefishes) 153 6 0
Tetraodontidae (puffers) 558 42 6
TOTAL 5 0
31
315 333 76
193
availability (Table 26.1). Clownfishes are a notable excep- Aquaculture in the Aquarium Industry 603
tion given the early development of successful culture
techniques and use of this species as the marine biology ing. Of these, commercially feasible techniques have
‘lab rat’ of coral reefs. Commercial scale production of primarily been developed for demersal spawners. This is
clownfishes began in the 1970s and 1980s with many of because of the inverse relationship between parental
these operations proving uneconomic. These initial investment and larval duration. Demersal spawning
attempts had high mortality of larval fish and malnutri- marine aquarium fishes that are commercially produced
tion‐induced mutations. include the Apogonidae (cardinalfishes), Pomacentridae
(damselfishes and clownfishes), Blenniidae (blennies),
Initial challenges for industry development included Gobiidae (gobies), Pseudochromidae (dottybacks),
identification of suitable live feeds that would be accepted Monacanthidae (filefishes), Hemiscylliidae (epaulette
by marine finfish larvae and be suitable for large‐scale cul- sharks), Plesiopidae (assossors) and Syngnathidae
ture. Adaptation of techniques developed for marine food (seahorses and pipefishes). This mode of reproduction
fish production led to substantial improvements in marine encompasses mouth‐brooders, pouch brooders, and
aquarium fish production. Most notable was an under- substrate spawners. These are similar to these modes of
standing of the importance of HUFA in larval develop- reproduction described for freshwater fishes (section
ment of marine fishes (section 8.4.7). Unlike freshwater 26.4.2). In both cases, spawning fish produce eggs that
fishes, marine fishes cannot synthesise eicosapentaenoic are maintained in a defined area and typically guarded
acid (EPA) and docosahexaenoic acid (DHA) from linolenic until hatching occurs. Only a few dozen to a few thou-
acid (18:3‐n‐3). Thus, EPA and DHA were found to be sand eggs are typically laid during a spawning session.
essential fatty acids and needed to be supplied in the form The eggs are generally large (a few millimetres in size)
of live prey items during hatchery culture. and hatching may occur two days or weeks after being
laid. During this time in the egg, the embryos develop
Use of the, now ubiquitous, rotifers in combination fins and pigmented eyes and hatch as larvae capable of
with live microalgae enrichment led to the first major locomotion and phototaxis (Figure 26.12). These larvae
commercial expansion of marine aquarium fish aqua- swim up into the plankton column to undergo further
culture. For much of the 1990s and 2000s, production of development while feeding on zooplankton. The larvae
marine aquarium fishes was largely focused on clown- return to a demersal life‐style post‐metamorphosis
fishes. Competition from low‐cost, wild‐caught fishes where they develop morphological features more similar
limited expansion into other species as did the paucity of to adults. The duration of this planktotrophic period
information on broodstock conditioning, larval devel- ranges from days to weeks among demersal spawners.
opment, hatchery production, and even natural ecology.
Together with information sharing among hobbyists In contrast, pelagic spawners produce thousands to
pioneering culture efforts, commercial operations have millions of small eggs that are dispersed into the water
been able to develop hatchery techniques for an ever‐ column to be fertilised and to drift into the pelagic zone.
expanding range of species. These eggs hatch after 24 to 36 hours yielding larvae that
lack pigmented eyes and a digestive system, and have
There are two modes of reproduction common to only rudimentary fins. These larvae initially float in the
coral reef fishes: demersal spawning and pelagic spawn- pelagic zone and are nourished by a small yolk supply,
Figure 26.12 Egg development of the fang blenny 8 cell stage 24 h 36 h 60 h
(Meiacanthus atrodorsalis) showing progressive
development until hatching occurs with the onset of
darkness after seven days (168 hr). At the time of
hatching, larvae are morphologically undeveloped with
many of the main organs becoming functional
posthatching. Source: Reproduced with permission of J.
Moorhead.
72 h 108 h 144 h 155.5 h
604 Aquaculture notable exception being the seahorses and pipefishes.
Thus broodstock are readily obtained and, in many
before they become sufficiently developed to begin cases, the geographical region from which broodstock
feeding. Larvae begin to require exogenous nutrition at a are sourced is known and, thus, the lineage of the result-
small size and are too small to ingest rotifers in culture. ing F1 generation is known. However, rising consumer
The larval period of pelagic spawners can extend beyond demand for novel strains in the marine aquarium indus-
90 days, which, combined with the small live feed try has seen a recent shift to sourcing broodstock from
requirements, renders the commercial production of F1 or F2 cultured generations of offspring. Where cultured
most pelagic spawners economically non-viable. As this juveniles are sourced as broodstock it may take many
section focuses on the aquaculture production of coral months for the fish to become reproductively mature
reef fishes currently in commercial production, only and be capable of spawning.
demersal spawners are discussed further. For a better
understanding of the bottlenecks of production and Given the small adult size of many highly‐sought fishes
developing culture methods for pelagic spawning species by the aquarium trade, there are limited options for
of coral reef fishes see Chapter 20, which addresses spawning induction. Hormonal injection, as applied to
the culture of groupers (Serranidae), a group of pelagic the food‐producing and freshwater aquarium aquacul-
spawners ture sectors, has not been extensively researched for
aquaculture of marine aquarium fish. Most commonly,
26.5.1.1 Broodstock spawning is encouraged by increasing water tempera-
Natural mating systems in coral reef fishes are highly tures above 28 °C or by simulating plankton blooms
diverse and a sound knowledge of the spawning system of through introduction of microalgae or Artemia into
the target species for culture is needed. The most com- broodstock tanks.
monly cultured demersal spawners establish long‐term,
pair‐bonding of a male and female fish (e.g., species of For all demersal spawners, eggs are best left in the
families Apogonidae, Pseudochromidae, Pomacentridae, care of the parent fishes that tend to the eggs by remov-
and some Gobiidae), although other cultured species ing unfertilised and dead eggs, by removing large parti-
form spawning harems (e.g., species of Blenniidae). There cles that settle on the eggs, and by oxygenating the egg
is also a diversity of mechanisms by which coral reef mass by fanning (Figure 26.13). These actions cannot
fishes become sexually mature, including: gonochorism, be adequately replicated in the absence of the parent
protandrous hermaphroditism (first male), protogynous fish. Often the eggs are removed from the parent fish
hermaphroditism (first female), and bi‐directional her- only hours before expected hatching and are then incu-
maphroditism (sex‐reversing, possibly multiple times). bated using strong aeration in a hatching tank. Hatching
Clownfishes, for example, are long‐term, pair‐bonding can often be induced by providing complete darkness
and protandrous hermaphrodites. Thus, an ideal pairing in the hatching tank when the developing embryos are
of broodstock would be one small fish (likely to be male) suitably developed. Once hatched, larvae are either
and one large fish (likely to be female). In another instance, reared directly in the hatching tank or transferred to a
Gobiodon species (Gobiidae) are long‐term pair bonding larval rearing tank.
bi‐directional hermaphrodites, so that any two individu-
als can be paired as broodstock. Figure 26.13 A clownfish protecting its developing clutch. Source:
Photograph by Silke Baron. Reproduced under the Creative
Conditioning broodstock often involves habituating the Commons Attribution Share Alike license, CC‐BY 2.0.
fish to human contact, feeding a nutritionally appropriate
diet, and providing an appropriate spawning substrate.
The natural diet of coral reef fishes may be highly special-
ised or quite broad. Replicating a natural diet as close as
possible is often the best approach to condition brood-
stock to spawn, although commercial feasibility generally
necessitates transitioning broodstock to a gelatine‐bound
wet diet made from various seafoods. The appropriate-
ness of a spawning substrate varies between species:
blennies readily spawn in PVC pipes, while clownfish will
spawn on ceramic tiles. In some cases, live algae or coral
may be required as the spawning substrates.
Broodstock are almost entirely sourced by wild‐capture.
In contrast to many endangered freshwater fishes in the
aquarium trade, nearly all marine fishes in the aquarium
trade are still available as wild‐caught organisms, the
26.5.1.2 Larval Rearing Aquaculture in the Aquarium Industry 605
Larval rearing begins immediately upon hatching.
Conical tanks ranging from 50 to 200 L are general suit- UJL
able with preference being given to black‐inside tanks. MGW
The dark background helps larvae visually identify prey LJL
items. Among demersal spawning fishes, newly hatched
larvae have only a minimal store of yolk remaining Figure 26.14 Mouth gape height can be determined from the
and are capable of first‐feeding almost immediately. upper jaw length (UJL) and lower jaw length (LJL). Mouth gape
Larval rearing typically involves static culture where width (MGW) is the distance between the left and right
larvae are maintained with gentle aeration, a live posteroventral tips of the articular bones of the jaw. Source:
food source (usually rotifers), and live or concentrated Reproduced with permission of Thane Militz.
microalgae paste. The live or concentrated microalgae
paste serves three functions in hatchery culture: width is measured as the distance between the left and
right postero‐ventral tips of the articular bones of the
1) it limits light intensity within the larval rearing tank jaw. From these measurements appropriately‐sized prey
allowing larvae to stratify themselves at a level of items can be determined.
appropriate illumination,
On the basis of mouth gape, rotifers are often the first
2) it provides a source of nutritional enrichment for the prey item offered to larval fish until they are capable of
nutritionally poor rotifers, and accepting newly hatched Artemia (Figure 9.7;
Figure 26.15). The appropriate time to introduce Artemia
3) it provides a dark background colour enabling larvae varies between species and with rate of development.
to easily distinguish prey items. For the clownfish (Amphiprion percula) reared at 30 °C,
larvae are competent to accept newly hatched Artemia
Larval rearing tanks are continually illuminated to max- by day three post‐hatching (Figure 26.15). However,
imise larval feeding and water exchanges may be done when rearing the clownfish (Premnas biaculeatus) at
once or twice daily to manage build‐up of nitrogenous similar water temperature, larvae are unable to accept
wastes and adjust live food densities. For most demersal Artemia until five days post‐hatching. Clownfish are
spawners, newly hatched larvae are capable of ingesting particularly quick to develop and Artemia are often not
the smaller (80–100 µm) ss‐strain rotifers (Brachionus introduced into larval cultures until 9 or 10 days post‐
rotundiformis). Rotifers are nutritionally enriched with hatching for most demersal spawning species. As growth
provision of microalgae or specifically manufactured rates vary between individual larvae, a period of weaning
rotifer enrichment products that are high in HUFA. larvae onto Artemia occurs. This weaning period encom-
Rotifers are maintained in the larval rearing tanks at den- passes offering larvae both rotifers and Artemia simulta-
sities between 2 to 20/mL. Studies show that larvae of neously (Figure 9.12) for roughly three days. This is done
demersal spawning fishes have similar survival over this to ensure survival of slower growing individuals and lar-
prey density because larvae encounter prey items fre- val acceptance of the new feed.
quently enough to invest minimal energy expenditure in
prey capture (Moorhead and Zeng, 2011). For some spe- As the newly hatched Artemia develop into metan-
cies of demersal spawners, the newly hatched larvae are auplii within 12 hours of hatching, they will quickly
too small to accept ss‐strain rotifers. In such instances, it become too large for the fish larvae to prey upon. This
is necessary to utilise copepod nauplii (50‐90 µm) as an requires regular clearing of Artemia metanauplii
initial prey item in combination with rotifers. through water exchange and replacement with more
newly hatched Artemia. This exchange is typically done
In determining the most appropriate first feed offered twice daily, coinciding with the growth of the Artemia.
to larval coral reef fishes it is necessary to assess a fish’s Once larvae are sufficiently large enough to accept the
mouth gape at both hatching and/or point of first feeding. larger metanauplii, this will become the principle food
Mouth gape will then need to be continually reassessed source introduced into culture (Figure 26.15). Due to
to determine the appropriate time in development to
begin offering larger prey items. There are two measures
of mouth gape of larvae: mouth gape height and mouth
gape width (Figure 26.14). Mouth gape height (MGH) can
be determined using the formula:
MGH UJL2 LJL2
Where upper jaw length (UJL) and lower jaw length (LJL)
is the upper and lower jaw length, respectively. Gape
606 Aquaculture
Figure 26.15 Developmental progression of clownfish (Amphiprion percula) reared in 29 °C seawater. This progression begins with newly
hatched larval fish at day 1. These fish are 4 mm in size and capable of accepting rotifers as a first feed. By day 3 of culture, substantial
morphological changes have occurred, and the mouth gape of larvae is large enough to allow ingestion of newly hatched Artemia. At
around day 6 or day 7 larvae metamorphose and are capable of beginning to accept enriched Artemia. Weaning fish onto an inert diet
begins shortly after metamorphosis with the aim of having juvenile clownfish requiring only an inert diet beyond day 15 of culture. By
two months of age juvenile clownfish (1‐2 cm) closely resemble adult fish. Source: Reproduced with permission from Thane Militz.
the changing nutritional value of growing Artemia, it required. Longer grow‐out periods of seven months are
becomes necessary to enrich metanauplii (section necessary for slower growing demersal spawners (i.e.,
9.2.14). Enrichment is typically done with purpose‐ plesiopid species). Longer grow‐out periods increase the
made products that increase the EPA and DHA content cost of production and high protein diets (often >50%)
of the Artemia. are provided to quicken growth. It is also during the
grow‐out period that colour‐enhancing pigments may be
Once larvae begin metamorphosis, the process by added to the diet. For example, astaxanthin inclusion in
which they undergo physiological changes and attain the the diet of certain clownfishes can enhance their red‐
characteristics of adult fish, weaning of larvae onto inert orange pigmentation.
feeds commences. Powdered aquaculture feeds in a size
range of 100 – 300 µm are introduced into culture several 26.5.2 Live Corals
times a day (Figure 26.15). These feeds are typically high Aquaculture production of live corals has increased
in protein (>50%). When successful weaning onto inert substantially over the past decade. This development is
feeds is achieved, the larvae are shifted to the nursery in response to advances in low cost lighting available for
and grow‐out stages of culture. This often involves trans- maintaining photosynthetic organisms in private
ferring settled juvenile fishes to a separate culture tank aquaria. The listing of all Scleractinia (stony corals) on
freeing up the larval rearing tank for culture of the next CITES Appendix II since 1985 has provided some politi-
batch of eggs. cal pressure to shift the supply of stony corals from field
collection to aquaculture. Trade in live coral for the
26.5.1.3 Nursery and Grow‐out aquarium industry appears to have peaked in 2006 at
Similar to freshwater aquarium fish production, the over 600 000 pieces of Scleractinia annually (Rhyne et al.,
grow‐out phase of culture is compressed into a short 2012). Since 2006, there has been a gradual decline in
time frame. The aquarium industry demands juvenile international trade of live coral, attributed to both the
fishes for ease of transport and the desire of many con- rise of domestic aquaculture and the global economic
sumers is to watch fishes grow in their private aquaria. crisis. In 2010, less than 10% of imported live corals were
Following the nursery phase where juvenile fish are identified as originating from an aquaculture source
weaned onto an inert diet, the grow‐out phase typically
lasts until the juvenile fish are 3 cm in length. For clown-
fishesa grow‐out period of three months is all that is
(Rhyne et al., 2012). However, the contribution of aqua- Aquaculture in the Aquarium Industry 607
culture supply varies greatly between species.
Broodstock coral are generally referred to as the
Aquaculture production of live coral occurs through ‘donor’ coral colony. Donor colonies can be wild coral
both in situ ocean‐based culture and ex situ land‐based growing on coral reefs or purposely cultured donor
culture (Barton et al., 2015). Both production systems colonies. The use of cultured donor colonies offers
revolve around coral polyp and asexual propagation. several advantages:
Each individual polyp of a live coral colony is capable of
self‐sustenance and regeneration. A piece of coral con- 1) the cultured donor colonies can be held close to the
taining one or several polyps will be removed from a aquaculture operation, minimising time spent and
broodstock coral colony and allowed to grow and regen- the expense of searching for suitable broodstock in
erate into a new, cultured coral colony. As most corals the wild,
sought by the aquarium trade rely on sunlight for photo-
synthesis of their symbiotic zooxanthellae, production 2) a source of desirable species or colours can be secured,
systems must supply appropriate levels of lighting. In in and
situ culture, lighting comes from sunlight and corals are
cultured at an appropriate water depth in areas with low 3) where donor colonies are maintained in similar envi-
water turbidity. In ex situ culture, lighting can come from ronmental conditions to the grow‐out of cultured
sunlight, where greenhouse culture is used, or from arti- coral, suitability of the grow‐out environment can be
ficial electric lighting. The latter raises the cost of culture assured.
substantially.
Where culture occurs ex situ, broodstock can similarly
Coral as sessile invertebrates requiring culture efforts be sourced from imported wild corals or their own cul-
to include an artificial base or substrate on which to tured stock.
grow, transport, and market the cultured coral colony.
Artificial bases are usually given preference over pieces In producing cultured corals, a proportion of the
of natural reef rock or rubble because it clearly identifies donor colony is removed in a process known as frag-
that the coral colony originated from aquaculture. The mentation which involves breaking or cutting a portion
artificial bases used differ greatly between aquaculture of the donor colony to produce a fragment. The frag-
companies. This is done for marketing reasons to allow ment can consist of one or several polyps. Generally, a
consumers to quickly identify certain aquaculture com- fragment will be a 3–5 cm piece of the donor colony.
panies’ products, but it also reflects locally available This may be in the form of a branch or a tissue cutting.
supplies. In the Solomon Islands, artificial bases are To ensure the health of the donor colony is maintained
made from locally available ingredients, with the recipe after fragmentation it is recommended that no more
comprising cement, sand, and water. This mix is poured than 20% of the donor colony is harvested as fragments
into PVC rings placed on top of firmly packed sand at any one point in time. The fragment is secured to the
allowing the hardened cement mix to take on a small artificial base and will undergo a period of grow‐out
disc shape. A small indentation is made in the centre of in situ or ex situ for several months to years.
the base as a site to attach a coral fragment and holes
may be made around the periphery of the base to assist Grow‐out in situ requires a supporting frame to pre-
with securing the base for in situ grow‐out. Variations of vent the fragments from being disturbed by wave action
this basic method include the inclusion of larger rubble or covered with sedimentation. It ensures easy access for
and the use of oxides to colour the cement making the maintenance and cleaning. For this purpose, iron trestles
or frames are used to support metal, wooden, or plastic
artificial bases appear more natural. Other operations racks to which the artificial base holding the coral frag-
use trademarked plastic bases or ceramic bases pro- ment can be attached. These frames hold the corals
duced using moulds. These bases typically have a basal above the sediment, typically 1–2 m below the surface.
The racks can be transported to and from the frames as
extension that fits into grow‐out trays, orienting the new fragments are made or fragments become cultured
coral upwards. This basal extension can also be used by corals ready for marketing. In ex situ culture, corals can
the end consumer to secure the cultured coral colony be produced while sitting directly on a raceway or tank
into the rockwork of their aquarium. However, bases bottom (Figure 26.16).
with extensions are generally only suited for grow‐out in
26.5.2.1 Hard Corals
areas of limited wave action or ex situ grow‐out. Given The description ‘hard or stony coral’ refers to all corals
that aquarists purchase the cultured coral colony for with hard, calcareous skeletons. These are species of
aesthetic enjoyment, substantial effort is invested into Scleractinia and include single polyp, large‐polyp colo-
nial, and small‐polyp colonial species. These corals can
making the artificial bases appear neat and aesthetically take several growth forms depending on species and
pleasing. environmental conditions. Growth forms can include:
608 Aquaculture in warm tropical climates, with prolonged shelf life only
possible with refrigeration. In contrast, two‐part under-
Figure 26.16 Newly produced coral fragments are being stocked water epoxies have a long shelf life until mixed. However,
into raceways to allow epoxy to cure before transfer to an ex situ these products typically have a longer cure time (gener-
grow-out site in Papua New Guinea. The round cement base ally around 1 hr) and a greater amount of adhesive is
provides a stable anchorage for the vertical coral fragments that required. The larger amount of adhesive renders the
are fixed in place with epoxy. Source: Reproduced with permission product less aesthetically pleasing and may require a
of Thane Militz. longer grow‐out period to ensure the base of the coral
fragment encrusts and covers the adhesive). In remote
branching, boulder, encrusting, plating, and solitary. areas where adhesives are not available, the scale of
Typically, species with branching and plating growth investment is small, or labour investment is irrelevant,
forms can be characterised by rapid growth, while spe- attachment of coral fragments to artificial bases may be
cies of solitary and boulder growth forms are slower achieved by using fishing line to tie down the coral frag-
growing. Aquaculture production focuses on the more ment. This methodology requires patience and skill but
rapid growing branching and plating species, mainly is commonly practiced by community‐based coral farms
species of the genera Acropora, Montipora, Pocillopora, throughout the Indo‐Pacific where the community is
and Seriatopora. Among Acropora species imports into paid per unit produced rather than hourly wages.
the USA in 2010, 26% of specimens were reported to be
from aquaculture production (Rhyne et al., 2012). Hard corals require a grow‐out period of six to twelve
months from initial attachment until they are ready for
All aquaculture production of hard coral for the aquar- market (Figure 26.16). A market ready coral colony is
ium industry relies on asexual reproduction. A fragment typified by having encrusted the artificial base and devel-
containing a number of polyps is first removed from a oped several branches causing the colony to resemble a
donor colony. Often the fragment will have an apical small ‘tree’ in shape. For plating growth forms the frag-
polyp, which is a polyp from the tip of linear growth such ment must encrust the artificial base and show some
as a branch tip or the edge of a plating coral. The frag- three‐dimensional growth.
ment removed can vary in size, but higher survival is
seen where fragments are 3–5 cm in length. Given the 26.5.2.2 Soft Corals
hard calcareous skeleton this is done with either wire The term ‘soft coral’ refers to all corals with soft, fleshy
cutters (for branching species) chisel (for plating and hydrostatic skeletons. This includes the species of
encrusting species), or table saw (for plating and encrust- Alcyonacea, Corallimorpharia, and Zoantharia. The
ing species). Fragments are then either tied or glued to techniques of culture differ more dramatically between
an artificial base with either cyanoacrylate gel or epoxy. growth forms than those for hard corals. The species of
Cyanoacrylate gel offers a quick cure time (gener- Corallimorpharia, Zoantharia, and some Alcyonacea take
ally < 5 min) resulting in rapid attachment of the frag- on encrusting growth forms. For this growth form a small
ment and only a small amount of adhesive is required. number of polyps can be tied, using fibrous string, to an
However, there is a limited shelf life of cyanoacrylate gels artificial base. The attached polyps will encrust, undergo
binary division, and spread over the artificial base at
which point the coral colony is ready for marketing. An
alternative production method is to place the encrusting
coral on loose substrates, such as rock rubble. With
appropriate environmental conditions the coral encrusts
the surrounding substrate and the connective tissue
between polyps can be cut to yield small mats of encrusted
coral that can easily be removed from the loose substrate.
This later approach is commonly employed in tank‐based
culture systems where there is no wave disturbance or
sedimentation on the loose substrate.
A number of species of Alcyonacea demanded in the
aquarium industry have branching or ‘mushroom’‐
shaped growth forms. Obtaining fragments from donor
colonies is similar to that of hard corals for these growth
forms. However, due to the fleshy hydrostatic skeleton a
knife or razor blade is the preferred tool used to take tis-
sue fragments from the donor colony. Fragments cut
Aquaculture in the Aquarium Industry 609
away from the donor colony must include living polys.
Given the fleshy hydrostatic skeleton, adhesives such as
cyanoacrylate gel or epoxy are unsuitable for attaching
fragments to an artificial base. Rather fibrous string or
something as simple as the threads of rice bags are used
to ‘sew’ the fragment directly to the base. Use of fishing
line is generally avoided because the smooth surface can
allow the fragment to slide around its point of attach-
ment and when pulled taught the line can slice through
the soft coral tissue.
Following attachment, the soft coral fragment is placed
in a suitable area with minimal wave action to allow
quick attachment to the base and subsequent grow‐out.
The grow‐out period of soft corals produced in situ (3–6
months) is typically more rapid than that of hard corals.
26.5.3 Giant Clams Figure 26.17 Tridacna noae broodstock spawning eggs 10 min
The majority of giant clam (Tridacninae) aquaculture after injection with 1‐mL of serotonin directly into the gonad
occurs in the Indo‐Pacific. This is due to the slow using a hypodermic needle. Source: Reproduced with permission
production to market size (typically > 1 year), bright from Thane Militz.
light requirements of the clam to allow their symbiotic
zooxanthellae to photosynthesise, and large space shed gametes, or serotonin injection. Heat stress involves
requirements for production. These requirements put laying broodstock clams on their side in full sun for
island nations close to the equator at a production 30–40 min before returning them to a spawning tank.
advantage given the year round high sunlight, warm This method works well for regions that experience an
water, and coastal habitat allowing grow‐out to occur annual shift in ocean temperature but is less successful in
in situ. Annual production of cultured giant clams in equatorial regions where clams are exposed to warm
the Pacific exceeds 70 000 individuals that contribute to water year round. An alternative method for spawning
the supply of both the aquarium industry and restock- induction is serotonin injection, whereby a 0.5–1.0 mL
ing of natal reef populations for subsistence fishing. injection of a 2 mM solution of 5‐hydroxytryptomine
Production for the aquarium industry focuses on four creatinine sulphate complex (serotonin) is injected
species: Tridacna crocea, T. derasa, T. maxima and directly into the clam’s gonad using a hypodermic needle
T. squamosa. These species are typified by their bright penetrating the mantle tissue. Injection is made through
mantle colours and small adult size making them more the mantle tissue below the excurrent siphon into the
suited to the confines of aquaria. gonad below. Where eggs are obtained (Figure 26.17),
these can be introduced into tanks of non‐spawning
Obtaining broodstock can be particularly difficult clams to induce spawning. This is known as gamete
given depletion of giant clam populations throughout exposure and in some cases a broodstock may be sacri-
their range due to exploitation for food, curios, and the ficed to obtain eggs via gonadal maceration to induce
aquarium industry. In some regions of the Philippines spawning of remaining broodstock. Given that individual
and Indonesia giant clam species are locally extinct. This clams typically release sperm and eggs in sequence, care
makes obtaining broodstock from local reefs impossible is taken to isolate the gametes and avoid self‐fertilisation.
and it has previously required the translocation of adult This is achieved by transferring clams to new spawning
clams from different regions or even different countries tanks after cessation of sperm release but prior to the
to establish aquaculture operations. As broodstock are spawning of eggs. Once eggs are spawned they are ferti-
simultaneous protandrous hermaphrodites, large speci- lised with a small aliquot of sperm suspension within
mens are needed (>20 cm for most species) to ensure 10 min. At this point larval rearing begins.
broodstock are reproductively mature as females and are
capable of spawning eggs. Obtaining juvenile cultured 26.5.3.1 Larval Rearing
clams and on‐growing these until reproductively mature Giant clams are typical of bivalve molluscs, going through
is not a viable option for new aquaculture operations as trochophore, veliger, and pediveliger stages before com-
the time to reproductive maturity can take several years. pleting metamorphosis into juveniles (Figure 26.18).
differences between species are minimal with the length
Spawning of broodstock is typically induced. Spawning of each developmental stage depending on factors such
induction can occur through heat stress, exposure to
610 Aquaculture (b) (c)
(a) (e) (f)
(d)
Figure 26.18 Larval developmental stages of the giant clam Tridacna noae showing: D‐stage veliger with extended velum (a); settled
veliger (b); veliger‐pediveliger transition showing extended foot (c); pediveilger with well extended foot (d); pediveliger with incorporated
zooxanthellae (arrow) (e); and metamorphosed juvenile with gills (arrow) (f ). Source: Southgate et al. 2016. Reproduced with permission
from Journal of Shellfish Research.
as water temperature and availability of exogenous (500–1000 L) hatching tanks. This often incorporates
nutrition. In general, larvae will reach the straight hinge use of antibiotics, such as streptomycin sulphate, as a
(D‐stage) veliger stage within 24 hr post‐fertilisation. bacterial preventative. At 24 hr post‐fertilisation, free‐
At this point the oesophagus and stomach have yet to swimming veliger larvae are then ‘selected’ from the
fully develop and it is not until 48 hr post‐fertilisation water column of the hatchery tank and stocked into large
that larvae can begin exogenous feeding. Veliger larvae (2000–10 000 L) larval rearing/nursery tanks or raceways
are initially free‐swimming using a ciliated velum, but by at a reduced density of 2 larva/mL. Water exchanges of
120 hr post‐fertilisation the larvae settle to the substrate 100–200% tank volume occur daily, and larvae are fed
where regression of the velum and development of the starting at 48 hr post‐fertilisation. Golden‐brown flagel-
foot indicates their progression to the pediveliger stage, lates are an ideal microalgae food source, with Isochrysis
typically occurring ca. 140 hr post‐fertilisation. It is gen- sp. and Pavlova sp. being most commonly used. Cell
erally accepted that between the pediveliger stage and densities used to feed the larvae are low (3000 cells/mL)
metamorphosis the larvae clams acquire the symbiotic compared to some other bivalves. The developing
dinoflagellate cells, termed zooxanthellae, which become larvae are maintained this way until metamorphosis is
incorporated into the developing mantle post‐metamor- complete when feeding stops.
phosis. Metamorphosis marks the transition of pedive-
ligers into juveniles and metamorphosis is considered In extensive hatchery culture, eggs are stocked directly
complete once developed gills are observed. Completion into large (2000–10 000 L) larval rearing/nursery tanks
of metamorphosis can happen as quickly as 10 days or raceways at a density of 2 eggs/mL. With the exclu-
though less‐optimal conditions can delay metamorphosis sion of aeration, the larval rearing tanks are maintained
to one month post‐fertilisation. as static cultures without the addition of food or water
exchange. Occasionally water exchange may begin once
Generic hatchery culture methods have proved suita- the larvae have settled, though the exchange rate is
ble for production of almost all giant clam species given kept low (≤100% per day). This culture method relies
the similarities of larval development and adult ecology. on developing larvae to make use of endogenous lipid
Commercially‐employed hatchery methods for producing reserves as their principal energy source. The success
juveniles typically conform to either an ‘intensive’ or of extensive hatchery culture is largely dependent on
‘extensive’ approach. In intensive hatchery culture, eggs culture water temperature. Warmer water temperature
are stocked at a density of 5–15 mL‐1 in small volume quickens larval development progression allowing a
greater number of larvae to reach metamorphosis solely Aquaculture in the Aquarium Industry 611
on their lipid reserves. This typically restricts the use of
extensive hatchery culture for giant clams to equatorial will quickly overgrow the juvenile clams and smother
locations, with supplemental exogenous nutrition being them. Suppression of algae growth is facilitated using
required at locations with higher latitude (i.e., Australia). light‐reducing shade‐cloth to cover culture tanks. A light
transmittance reduction of 50–70% is often employed
While a proportion of unfed larvae are able to meet the during the first two to three months of juvenile culture.
energetic requirements of metamorphosis from these At three months of age, nutrient supplementation in the
tissue lipid reserves at certain locations, survival is gen- form of nitrogen or phosphate has been found to increase
erally less than when supplemental exogenous nutrition growth rates of juvenile clams. However, care must be
is provided. taken not to over‐fertilise culture tanks as surplus
nutrients can also encourage algae growth.
For all methods of culture, it is necessary to ensure
provision of the symbiotic zooxanthellae prior to meta- At 2 cm shell length clams are typically either redistrib-
morphosis. This is often done by sacrificing a ‘donor’ uted or relocated for further grow‐out. This is necessary
clam and removal of its mantle so the zooxanthellae can to prevent overcrowding of juveniles as they grow and
be harvested. The mantle is either processed in a blender often to take advantage of faster growth rates achieved
or delicately sliced with a blade and washed with seawater in situ. Transferring giant clams to ocean grow‐out is
to harvest the zooxanthellae. The resulting suspension commonly practised to maximise production per unit
containing zooxanthellae is sieved to minimise the space. In the ocean, giant clams are initially maintained
introduction of organic matter to culture tanks, and in protected cages, racks, or suspended rafts. This mini-
zooxanthellae are then introduced into the culture tanks mises sediment accumulation and smothering of clams,
at a density of 20 to 50 cells/mL. The introduction of but they also protects clams from potential predators.
zooxanthellae is often done several times before meta- Minimal care is provided to clams during grow‐out, the
morphosis to ensure acquisition of the cells by larvae. exception being regular inspections and removal of pred-
ators (gastropods most notably). The grow‐out phase can
The hatchery method selected for giant clam culture is last from six months to several years depending on the
largely governed by feasibility. Where seawater is warm size required by the aquarium industry. Typically clams
(28–30 °C) year‐round and the technical capacity to between 3 cm and 10 cm are most demanded as they are
maintain live microalgae cultures is limited, an extensive large enough to survive transport and establishment in
hatchery culture method is typically employed. Where aquaria but small enough to minimise costs of transport
seawater is cooler (<28 °C) and trained aquaculture tech- to market.
nicians are available, more intensive hatchery culture
methods are generally selected. Current research efforts 26.5.4 Live Rock
in giant clam hatchery culture are examining the use of Contrasting with the use of dead coral skeletons for the
commercially‐available microalgae concentrates as a decoration of marine aquaria that was common during
live microalgae replacement (Southgate et al., 2017). the 1970s and 1980s, modern coral reef aquaria typically
Products offering off‐the‐shelf convenience and requir- try to reflect the natural reef environment. This involves
ing limited technical capacity are ideal for the developing providing a reef‐like foundation in aquaria using live
island nations were the bulk of giant clam production rock. The name ‘live rock’ can lead to misunderstandings,
occurs. Microalgae concentrates offer the potential to as the rock itself is not actually alive, rather the rock is
deliver the higher survival and productivity of intensive composed of aragonite reef remains. It is only alive in the
hatchery culture without requiring a technical capacity to sense that the rock, taken directly from the ocean, is
produce large volumes of high‐quality live microalgae. home to a diversity of micro‐ and macroscopic marine
organisms. Notable functions of live rock include:
26.5.3.2 Nursery and Grow‐out ●● aesthetic appeal, as the rock becomes encrusted with
Nursery culture encompasses the period from newly
metamorphosed juvenile clams up until they attain a coralline algae;
shell length of ca. 2 cm. Typically, nursery culture occurs ●● harbouring a diversity of macro‐invertebrates that act
in the larval rearing tanks or raceways where the meta-
morphosed juveniles are left to grow. Disturbing clams as detritus feeders;
prior to 2 cm can damage the developing byssus and foot, ●● a food source for resident fishes; and
resulting in mortalities. This phase of culture will last six ●● serving as the primary biological filter.
months to a year depending on the growth rate of the For the latter function, the live rock is embedded with
species being cultured. The primary challenge of nursery populations of Nitrosomonas and Nitrobacter species
culture is to encourage clam growth while suppressing bacteria in the aerobic outer layers of the rock, while the
growth of fouling algae. Left unmanaged, fouling algae anaerobic core of the rock is known to be embedded
612 Aquaculture rock is cultured in situ, being transported by boat to a
culture site of several hectares in size. Culture sites are
with populations of anaerobic bacteria, such as Pseudo typically sand flats removed from the actual reef or
alteromonas species. These bacteria function in the intertidal areas where natural live rock is collected.
breakdown of nitrogenous wastes (Chapter 4) and mini- Here the rock is maintained for 1.5 years allowing it to
mise the accumulation of ammonia and nitrite in the become colonised by marine flora and fauna. During
confines of the aquarium. the culture period, labour is invested to periodically
rotate the rocks ensuring even coverage of coralline
Historically, supply of live rock to the aquarium trade algae and batch consistency. Where live rock is removed
came exclusively from field collection. Reef rubble, from the leased culture site, it is quickly replaced with
originating from cyclones and the natural regenerative recently produced rocks.
process of coral reefs, accumulates along reef bases and
intertidal areas, and was hand collected. However, a There has been a recent development of ex situ live
number of live rock operations have been closed in the rook production in the USA. This method makes use of
last decade and increased regulation has limited harvest. produced rock where non‐toxic water‐based pigments
This coupled with an increasing demand and rising can be added to mimic coralline algae. The rocks are
transportation costs has led to the farming of live rock then cultured in large volume tanks (>10 000 L) within
closer to the end markets becoming cost‐effective. greenhouses. The culture period is only three to four
Aquaculture production of live rock occurs primarily in months or until nitrifying and denitrifying bacteria
Fiji and within the Caribbean. Newly emerging land‐ become established. By being a closed culturing system,
based culture of live rock also occurs in the USA. the diversity of coral reef flora and fauna that establishes
on the rocks is greatly reduced compared to in situ
In culturing live rock, priority is given to creating production. This method of production reduces the
‘natural’ shapes and maximising the porosity of the rock likelihood of introducing ‘pest’ flora and fauna into a
to reduce the weight per unit volume. This is because consumer’s aquaria but also limits the diversity of poten-
consumers favour such traits and the need to compete tially desirable organisms.
with wild‐collected product. The degree of porosity is an
important trait of live rock given that the retail cost of Following in situ production, rock is generally cleaned
the product primarily reflects the freight rate and live and ‘cured’ to reduce decay of organisms during transit.
rock is typically sold on a weight basis. High porosity This involves physical removal of sessile invertebrates
results in a lower cost product per unit volume but also and algae followed by air emersion under seawater
increases the inhabitable surface area available to micro‐ spray bars. The later process encourages the larger
and macroscopic organisms. mobile invertebrates (typically ‘pest’ species) to vacate
the porous cavities of the live rock. The cured live rock
The initial step in producing cultured live rock is to is then shipped moist in styrofoam boxes either by boat
formulate or source the base rock that will be cultured. (taking six to eight weeks) or air freight (taking two to
Where existing rock is sourced, preference is given to three days), the latter allows for greater survival of
limestone (calcium carbonate‐based rock) that can be flora and fauna inhabiting the rock but comes at a price
purchased from mining operations. The high calcium premium to the consumer. Where production of live
carbonate content of limestone closely resembles the rock occurs close to market there is the option to ship
biochemical composition of natural live rock. However, ‘wet rock’ where uncleaned rock immediately harvested
the diversity of shapes available in the sourced rock can from the ocean is packed with seawater and shipped via
be limited and often an extended period of time (>5 years) expedited courier. Usually this service is limited to live
is required to naturalise the mined shapes and improve rock aquaculture operations selling direct to consumers.
porosity. The alternative to sourcing rock is to produce
rock. This option offers unlimited flexibility in crafting 26.6 Sustainable Development
shapes demanded by the consumer, with rock being
crafted into branching forms, plate forms, and intricate Poorly managed development of aquaculture poses
boulder forms. Produced rock typically consists of a substantial risk to the environment and consumer sup-
cement mixture incorporating sand and larger calcium‐ port for the aquarium industry. This section examines
carbonate based rubble. Once the cement mixture is the primary risks of poor management practices that
crafted into the desired shape it is allowed to cure. The could impair sustainable development of the aquarium
initial curing process of produced rock can take six aquaculture sector. In many cases, aquaculture operations
weeks as earlier exposure to seawater can result in the make use of field collected broodstock every two to three
cement component dissolving. Commercial operations generations, which creates a continued dependence on
producing live rock can achieve production of around
7000 pieces per week.
The actual culturing can begin once rock is sourced
or produced rock has finished curing. In Fiji, produced
wild stocks. One of the main arguments against aquacul- Aquaculture in the Aquarium Industry 613
ture production of aquarium organisms with depleted
wild stocks is that the repeated removal of wild animals inferior hatchery culture conditions. This created a
as broodstock further endangers wild populations of the stigma for aquaculture as a producer of ‘manufactured
organisms. For a truly sustainable aquaculture sector, freaks’ and novel strains failed to gain acceptance in the
broodstock will need to be sourced from cultured marine aquarium industry until decades later.
sources. This reduces both the impact on the wild stocks
and ensures the availability of broodstock supply despite Many of the ethical considerations in aquarium organ-
potential collection closures and changes in export/ ism production are most easily resolved by producing
import regulations that may prevent access to wild‐ organisms that respect natural phenotype variations.
caught organisms. Selective breeding that allows the organism to remain
fully functional with respect to its natural behaviour and
Maintaining genetic integrity of captive populations of could theoretically occur in the natural environment
aquarium organisms is also a broodstock issue. Where depending on selective pressures, is a code of practice
aquaculture operations produce wild‐type strains of aquaculture operations could adopt to avoid risk of nega-
organisms, care must be given to the genetic integrity of tive perceptions. However, not all aquaculture opera-
the cultured fishes to maintain regionally distinct genetic tions currently adhere to such codes of practice. Among
lines and minimise inbreeding. This is best accomplished guppies there exist novel strains with extended anal fins
with dependable record keeping on broodstock sourc- that are so long neither sex is able to perform proper
ing. To maintain genetic integrity, pairing or grouping of copulation. This ornamental form is unable to reproduce
broodstock originating from a select geographical area naturally, and surgery is performed to shorten the anal
should be encouraged. The resulting offspring should be fin allowing broodstock to reproduce.
marketed with respect to their geographical origin to
avoid consumers accidentally producing their own Infectious disease is an emerging concern regarding the
‘unnatural’ crosses. Culturing organisms with respect to economic and social sustainability of aquarium aquacul-
their geographical origins maintains the overall diversity ture. Unlike food fish, there are minimal regulations con-
of the captive population of organisms that are produced cerning the use of therapeutic drugs in the aquarium
in this manner. This genetic diversity is critical if captive industry. This has led to the widespread use of antibiotics
populations are ever used to restock depleted wild pop- and carcinogenic chemicals (e.g., malachite green) for the
ulations. The reality is that the genetic lineage of fishes treatment of disease. In many cases, aquarium aquacul-
produced in aquaculture is largely unknown, which in ture operations lack the equipment, expertise or capacity
itself, increases the risk of potential inbreeding. to access assistance in identifying pathogens. Many
aquarium aquaculture operations may simply not be
There are increased concerns of inbreeding where aware that their stock harbours pathogenic organisms
genetic integrity is forgone to produce novel strains. leading to the transhipment of infectious agents between
With a heavy commercial focus on the aesthetic appeal countries (Wittington and Chong, 2007). Identifying pre-
of novel strains, the emphasis of selective inbreeding ventative measures farmers can take, as opposed to reac-
typically prioritises aesthetic attributes of the genotype tive treatments, will be necessary to reduce the incidence
over those attributes required for vigour. Concerns of of infection disease in the aquarium aquaculture sector in
deleterious effects from inbreeding have already been a sustainable manner (Militz and Hutson, 2015). Coupling
realised for some species of freshwater fishes. For example, preventative management with the development of alter-
it was experimentally demonstrated that inbred strains natives to antibiotics and chemicals should also be priori-
of the guppy, Poecilia reticulata, had increased suscepti- tised as this sector develops (Militz and Hutson, 2015).
bility to parasites and lower capacity to clear infection Aquarium aquaculture can also have negative impacts
(Smallbone et al., 2016). In other cases, inbreeding on the environment where cultured organisms are
results in a high frequency of deformed offspring from released or escape into the natural environment. There
are over 185 species of non‐indigenous fishes found in
which a limited number of desired fish are kept and USA waters, with 75 species having established breeding
sold, culling the remainder. These practices raise ethical populations (Tlusty, 2002). Approximately, 65% of these
considerations in animal production. If consumers or the escapees have been linked with aquaculture, with much
general public become ethically opposed to such prac- of the remainder attributed to the release of aquarium
tices, which currently remain out of mainstream media fish by the end consumer. While some risk is mitigated
when tropical fish are produced in temperate regions,
focus, this could taint the overall perception of aquarium the reality is that substantial aquarium aquaculture pro-
aquaculture. Much of the delay in consumer acceptance duction occurs in tropical regions where outdoor culture
of novel strains in the marine aquarium industry, relative methods are practiced. The concern for aquaculture
escapees is most realised in examples where non‐
to the freshwater industry, was public media exposure indigenous species are maintained in situ, such as sea
of miss‐barred clownfishes being produced as a result of
614 Aquaculture goal of aquaculture is to improve aquarium industry
sustainability.
cage culture of novel strains of the clownfish, A. percula,
in Indonesia (Figure 26.3). There is particular concern 26.7 The Future of Aquaculture
with the release of novel strains within the geographical in the Aquarium Industry
range of the original wild‐type strain. Such novel strains
may have the capacity to breed with wild stocks, substan- As global affluence continues to rise, the marine aquar-
tially altering local population genetics and be likely to ium hobby has become increasingly popular. However,
introduce genes that result in a loss of organism fitness in sustained and continual growth of the sector cannot be
the natural environment. Being environmentally con- guaranteed given that this popularity closely reflects
scious of facility discharge, limiting in situ production to economic trends and, as luxury goods, demand for
indigenous species, and avoiding intentional release of aquarium organisms can rapidly decline where markets
gametes or juvenile fish into local water ways are basic experience economic depression. Where demand
concepts in responsible aquaculture development that decreases in primary markets (USA, Europe, Japan)
need to be more closely observed by the aquarium there is little value of aquarium organisms in other mar-
aquaculture sector. kets implicating potential risk of investment. Costs of
transportation and regional variations in production
There is also the sustainable development considera- expenses will dictate whether aquarium aquaculture
tion relating to where future aquaculture development undergoes future expansion. Where expansion does
occurs. At present, there has been a shift in the economic occur, investment will continue to be small relative to
base of most of the freshwater aquarium industry. Fishers food‐producing aquaculture sectors.
living in economically marginalised communities histori-
cally relied on their supply of field collected organisms to Aquaculture is likely to continually increase its market
the aquarium trade as their livelihood. However, aqua- share of live organism supply relative to wild‐capture. In
culture developments rarely occur within these margin- the context of increasing environmental concern regard-
alised communities, given their remoteness and the ing the sustainability of wild‐caught organisms, aquacul-
scale of investment required. This has resulted in a shift ture is seen as a solution. While aquaculture is not
whereby a fish (i.e., a cichlid species) once caught by without its own sustainability concerns, it offers an
communities of the African rift lakes are now almost internationally accepted option to supply the increasing
entirely produced by aquaculture operations in the USA number of CITES listed organisms demanded by the
or Southeast Asia. As a result of aquaculture develop- aquarium market. It is foreseeable that the marine aquar-
ment, these communities have lost their livelihood to ium sector will continue to advance in producing a
overseas development. Most alternative livelihoods greater variety of novel strains, similar to what is cur-
available to these marginalised, remote communities are rently available in the freshwater aquarium marketplace.
typically far more environmentally destructive (i.e., for- As novel strains attain increasing popularity among con-
estry, mono‐crop agriculture, mining, food fisheries) sumers, in both the freshwater and marine aquarium
than the collection of aquarium organisms. Thus, in markets, aquarium aquaculture will be able to better
order for aquaculture to be effective in conserving the ensure its own economic future.
natural habitats of fishes demanded by the aquarium
industry there are some development considerations 26.8 Summary
that need to be made. Firstly, a greater proportion of
aquaculture development should occur in the source ●● The global aquarium industry encompasses a large
countries that supply the aquarium industry with field diversity of freshwater and marine organisms.
collected organisms. This development is already seen
with giant clam, coral, and live rock production occur- ●● Freshwater aquarium organisms are primarily sourced
ring in communities historically engaged in the supply of from aquaculture.
field collected organisms. However, this development has
yet to be seen for freshwater and marine aquarium fishes. ●● Marine aquarium organisms are primarily sourced
A second option is to limit aquaculture development to from wild fisheries with aquaculture playing an
novel strains and species that cannot be sustainably increasingly important role.
collected from their source. For example, supply of the
cardinal tetra (Paracheirodon axelrodi) from its South ●● Aquaculture of aquarium organisms encompasses a
American source is highly sustainable and encourages diversity of production systems that are necessary to
communities to maintain natural habitats for this species. accommodate the diversity in species produced.
On this basis, there is little justification for aquaculture
to culture such a species. The entirety of social, economic, ●● There are many perceived benefits of aquarium organ-
and ecological considerations needs to be explored when isms produced via aquaculture that are likely to be the
developing aquaculture for a select species if a true subject of future research in this field.
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in culture. PLoS ONE, 10, e0117723. Embryonic and larval development of the giant clam
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and Commerce of Ornamental Fish: technical‐managerial Tlusty, M., 2002. The benefits and risks of aquaculture
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breeding techniques for marine ornamental fish: a UK. 66 p.
review. Reviews in Fisheries Science, 18, 315–343. Whittington, R.J. and Chong, R., 2007. Global trade in
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617
27
The Future of Aquaculture
John Hargreaves, Randall Brummett and Craig S. Tucker
CHAPTER MENU 27.4 Summary, 635
27.1 Introduction, 617 References, 636
27.2 Drivers of Future Demand and Supply, 619
27.3 Responding to the Challenges of the Future, 625
27.1 Introduction planet that have collectively characterised what has come
to be called ‘The Great Acceleration’ of the Anthropocene.
Aquaculture as a farming practice dates back millennia In 2014, global capture fisheries produced 93.4 million t
and traditional, small‐scale subsistence aquaculture of fish, with 20.9 million t destined for non‐food uses,
continues to be an important livelihood activity in rural leaving 72.5 million t for human food. Aquaculture pro-
areas around the world, especially in Asia. Scientific duced 73.8 million t of fish that year, almost all destined
aquaculture did not begin until the 1940s and it really for human food, which accounted for just over 50% of the
was not until the 1970s that aquaculture became recog- total human food fish production (146.3 million t).2
nised as having the potential to make a significant contri- In addition to fish production, aquaculture produced
bution to global protein supply. During the 1980s, the more than 27 million t of farmed aquatic plants. The
Blue Revolution of rapid expansion took place and aqua- transition from the dominance of capture fisheries to the
culture began to make a significant contribution to global dominance of aquaculture has occurred within about
fish supplies1, just as wild capture fisheries were reaching three decades — an amazingly short time for a change
a production plateau of around 90 million t. this profound.
Fish from capture fisheries and aquaculture combined The rapid growth of aquaculture raised issues related
is now the largest source of animal protein in the world. to environmental degradation, negative impacts on
Fish produced in aquaculture make an important con- biodiversity and other, mostly local, impacts. Symptomatic
tribution to the food security of millions of people, of unsustainable growth were much‐publicised issues
especially in the developing countries of Asia (Béné such as major disease outbreaks in shrimp and salmon,
et al., 2015). Fish provides 4.3 billion people with at least stock crashes in Lake Taal in the Philippines and the
15% of their consumption of animal protein. Aquaculture loss of mangrove forests in Indonesia and Thailand.
production is also the source of livelihoods for 188 In the 1990s, environmental concerns related to the
million people, 94% of which are in Asia. About 10% of sustainability of aquaculture came to the fore. Food
the global population works in fisheries or aquaculture safety, particularly antibiotic and chemical residues,
value chains. also emerged as a major concern at this time. In response,
from the mid‐1990s through the 2000s, commercial
Aquaculture is the youngest and fastest‐growing aquaculture sectors responded with the development of
commercial food‐production sector. The activity arose best management practices to address specific problems
very quickly, in accord with other rapid changes to the and ecolabeling certification systems comprising suites
of best management practices to address consumer
1 In this chapter, ‘fish’ will be used as a collective term referring to
finfish, crustaceans, and other shellfish grown in fresh, brackish, or 2 The State of World Fisheries and Aquaculture (SOFIA) FAO (2016)
marine waters. (It differs from ‘seafood’ which is used in some other http://www.fao.org/fishery/sofia/en
chapters, and which includes seaweeds and other aquatic plants.)
Aquaculture: Farming Aquatic Animals and Plants, Third Edition. Edited by John S. Lucas, Paul C. Southgate and Craig S. Tucker.
© 2019 John Wiley & Sons Ltd. Published 2019 by John Wiley & Sons Ltd.
618 Aquaculture
Figure 27.1 Fresh seafood at a market in Barcelona, Spain. The world’s seafood supply must increase to meet the demands of a growing
world population. Most of the future supply will come from aquaculture. Source: Photograph by Andy Mitchell. Reproduced under the
Creative Commons Attribution Share Alike license, CC‐BY‐SA 2.0.
concerns regarding the environmental performance of boundaries are emerging to constrain growth. Foremost
aquaculture. among these are looming resource limitations (Naylor
et al., 2009). The higher value and increasing scarcity of
The world needs to produce significantly more fish in some key resources—trends that will be exacerbated by
the future to provide high‐quality animal protein to a global climate change—will be major drivers of the new
growing and increasingly affluent population (Figure 27.1). growth trajectory for aquaculture. The annual growth
Undoubtedly, future supplies of fish will be dominated by rate of aquaculture in the future is expected to be lower
aquaculture.3 By 2030, the World Bank (2013) estimates than during the boom years of 1970‐2010 because of
that 62% of fish for human consumption will be produced the scarcity of fresh water, fewer locations available for
by aquaculture. Assuming no change in per capita con- optimum production, and the high costs of fishmeal and
sumption, aquaculture must continue to grow to keep fish feeds. As competition for these increasingly scarce
pace with the increased demand for fish associated with a or limited resources increases, so must the intensity of
world population expected to exceed 9 billion by 2050. aquaculture production systems. Another limitation will
be imposed by the inability to significantly expand the
Despite the pressing need to produce more fish, and land area needed to grow the crops used to produce
the market opportunities that this need creates, aquacul- aquaculture feeds.
ture will not be able to grow in the same way as it has
over recent decades. New limitations, restrictions and The challenge for aquaculture is to increase production
as a means to improve human health (reduce protein
3 With some overlap, species in aquaculture can be broadly classified malnutrition and obesity) and contribute to food security
as ‘extractive’ (e.g., molluscs and shellfish) or ‘fed’ (e.g., fish and while simultaneously minimising environmental damage.
shrimp). Although extractive species will continue to play an In other words, aquaculture must become more sustain-
important role in global aquaculture production, most of the able and use resources more efficiently to preserve the
discussion in this chapter will emphasize fed species.
natural capital and ecosystem services on which it The Future of Aquaculture 619
depends. Combining these key concepts is often referred
to as ‘sustainable intensification.’ The goals of the many demographic megatrends also represent threats to future
users of increasingly scarce resources must be balanced aquaculture through competition for increasingly scarce
against the maintenance of the structural and functional resources and from environmental pollution.
integrity of the ecosystems in which aquaculture and
other human activities are embedded. If it can succeed The human population is expected to be around 8 billion
in doing this, aquaculture will undoubtedly play a large in 2025, 8.3 billion by 2030 and 9.5 billion by 2050. This
role in the future of fish supply and the growing ‘Blue population growth will increase the demand for food,
Economy.’ Real prices of farmed fish are likely to rise in water and energy. By 2030, the global population will
coming decades. Whether aquaculture can grow to require 35% more food, 40% more water, and 50% more
meet the demand for fish will depend heavily on the energy. Without any change in the per capita consump-
extent to which it can internalise the need for sustainable tion of fish, aquaculture must grow just to meet the
intensification and innovate to increase efficiency. demand for fish by more than 9 billion people.
Aquaculture must change to adapt and work within the
limitations set by these new constraints and yet expand By 2030, 60% of the world’s population will be middle
to meet the demand for fish in the future. class, two‐thirds of the middle‐class population will be
from China and India, and 80% of the middle class will
27.2 Drivers of Future Demand live in developing countries. Soon, more people will be
and Supply middle class than poor. By 2030, there will be more than
3 billion people in the middle class in the Asia‐Pacific
The need for more fish produced in aquaculture is clear. region, dominated by China and India. Demand for fish
To maintain the current per capita seafood consumption will be profoundly influenced by rising affluence and
of 18–20 kg, a supply of 160 to 180 million t of fish will be increased purchasing power of the middle class, in part
needed by 2050, with at least 100 million t coming from related to increased recognition of fish as part of a
aquaculture (Merino et al., 2012). If predicted increases healthy diet and an increased environmental awareness
in the per capita demand for fish in China are realised, of the general population.
40% of this market will be in China (World Bank, 2013).
To keep pace with this growing demand, aquaculture Increasing affluence has been accompanied by a dietary
must grow at an annual rate of about 6%, but environ- shift towards a greater per capita consumption of animal
mental and social constraints have reduced annual protein, including fish. Rising income is considered to be
growth in recent years to less than 5%. a more important driver of the demand for fish than
population size (Béné et al., 2015). Global consumption
A useful approach to considering the future demand of meat has doubled in the last 50 years from around
and supply of fish from aquaculture is with reference to 23 kg to about 42 kg. People in developing countries are,
key global megatrends and drivers. Megatrends are long‐ on average, increasing meat consumption at 5% annually,
term transformative issues and forces, applicable for at with expectations of future growth ahead. Animal pro-
least 20 yr and are relevant globally. Megatrends and tein production can be resource intensive, placing pres-
drivers are political, social, economic, environmental sure on commodity grain markets and water resources.
and technological. They affect the flows of the natural
capital and ecosystem services that support aquaculture About two‐thirds of the global population will live in
and so specific geographic context is important. Here we cities in 2050 and most of the growth in urban popula-
describe some of the main megatrends and drivers of tions will occur in Africa and Asia. Urbanisation has
change and look into the future to assess how these will been directly associated with increased consumption of
shape the future evolution of aquaculture. animal protein, including fish. One of the main effects of
urbanisation on aquaculture will be associated with
27.2.1 Demographic Megatrends increased market demand for seafood from aquaculture.
There are four important demographic trends that will Urbanisation creates some obvious challenges for food
affect future demand for fish from aquaculture: global production. The economies of countries with a highly
population growth, the rise of the middle class in Asia, urbanised population are less dependent on agriculture
urbanisation, and ageing populations. Collectively these as a share of gross domestic product (GDP). However,
present a significant opportunity for future aquaculture urbanisation will stimulate agriculture and aquaculture
through increased market demand for fish. Some production in urban and peri‐urban areas because mar-
keting and food distribution are facilitated by urbanisa-
tion. In many growing cities around the world, especially
in Asia, urban land use is encroaching into former
peripheral areas used for food production, including
shrimp and fish farming (Figure 27.2). Poaching and
pollution become more problematic in interface areas,
making these sites less suitable for aquaculture.
620 Aquaculture
Figure 27.2 Transformation of mangrove wetlands (foreground) to shrimp ponds (left) and urban land use (right) in Guayaquil, Ecuador.
Urban land use is increasingly encroaching on pond aquaculture infrastructure. Source: Reproduced with permission from John
Hargreaves, 2017.
Declining birth rates and reduced mortality rates 27.2.2 Limitations by Key Natural Resources
(especially child mortality) have resulted in increased life and Ecosystem Services
expectancy and an increase in the proportion of the elderly Supplies of the natural resource base that supports
in the global population. The fastest‐growing demographic human life on the planet are limited and some resources
group is people over 65 years of age. In 2011, 11% of the are being depleted at an alarming rate. Furthermore, the
world’s people were over 65 years old and this is forecast supplies of key resources, especially fresh water, are not
to reach 22% by 2050. This means the world will contain uniformly distributed (Figure 27.3). Some countries have
more than 1 billion people over 65 by 2030 and 2 billion adequate supplies of fresh water and land to support
people over the age of 65 years by 2050. Ageing popula- aquaculture development and others do not. As noted in
tions are generally more health‐conscious and, based on a the previous section, population growth, economic
concern with longevity, have begun to shift consumption development, and middle‐class consumption associated
to more healthful forms of protein, such as fish. with rising living standards will increase the demand
for key resources. Climate change will place additional
Based on assumptions about population growth, pressure on resource availability, especially fresh water
changing diets, and agricultural systems, the FAO esti- and food production. The challenge for food production
mates that food production needs to increase by 70% by is that productivity gains in agriculture have been declin-
2050 to meet demand. This includes growth in annual ing since 2000.
cereal production from 2.1 billion to 5.1 billion t and
meat production from 200 million to 470 million t.
The Future of Aquaculture 621
Little or no water scarcity Physical water scarcity Imminent physical water scarcity
Economic water scarcity Not estimated
Figure 27.3 The global distribution of fresh water is uneven. Notice the scarcity of water in countries in Asia that are important global
aquaculture producers. Source: Image from the World Water Development Report courtesy of Wikimedia Commons. Photograph by
Axelsaffran. Reproduced under the terms of the Creative Commons Attribution share licence, CC BY-SA 3.0.
The key natural resources used for aquaculture produc- from manufacturing, electricity generation, and domes-
tion are water, land/space, forage fish used for feed, and tic use. By 2030, the demand for water could be 40%
energy. Use of these resources in production can cause greater than supply, and water shortages could affect
water pollution and impacts on biodiversity. Resource 50% of the world’s population. There are 1.2 billion
use and the environment are discussed in Chapter 5. people that live where there is insufficient water to meet
Here we highlight aspects related to resource limitation human needs and by 2030 nearly half the world’s popula-
on future aquaculture. tion will live in areas with severe water stress. Overall,
water scarcity represents a serious challenge for food and
In the context of the global food production system, energy security. Water availability will be a key site‐selec-
aquaculture is a small sector and therefore uses much tion criterion for new aquaculture pond construction.
less fresh water, land, and energy than other, larger
sectors. The one important exception is the use of Agriculture is the largest consumer of fresh water
marine pelagic forage fish in feeds, for which aquacul- (4000 km3/yr), accounting for some 70% of total with-
ture uses most of the resource. In general, aquaculture drawals, mostly from rivers and groundwater aquifers.
uses resources efficiently to produce protein and is more The total supply of renewable fresh water is about 44 000
efficient than the production of most terrestrial animals km3/yr. Although estimates vary, the current use of fresh
(Table 27.1). The relatively small size of the aquaculture water in aquaculture is less than 200 km3/yr, about 5% of
sector should not preclude efforts to improve resource agricultural use.
use efficiency and lessen environmental impact.
Currently, 35% of the world’s crops are used for
27.2.2.1 Water animal feed. By 2030, shortages of fresh water could
Global water demand is forecast to increase by 55% cause a 30% reduction in grain production. Grain pro-
between 2000 and 2050, with the largest increases coming duction in China and India face significant challenges
from environmental stresses relating to water scarcity,
622 Aquaculture
Table 27.1 Some measures of the relative efficiencies of animal protein production.
Commodity Feed conversion Protein conversion N emissions P emissions
ratio (FCR) efficiency (%) (kg N/t protein) (kg P/t protein)
Beef 12.7 5 1200 180
Pork 5.9 13 800 120
Poultry 2.3 25 300
Salmon 1.0 43 284 40
Shrimp 2.0 27 309 71
Tilapia 1.8 24 593 78
Carp 1.5 30 471 172
148
Source: Data from Hall et al. (2011) and from Boyd and McNevin (2015). Feed conversion ratio = kg feed ÷ kg animal
growth; protein conversion efficiency = [(kg animal protein ÷ kg feed protein) × 100].
soil depletion, climate change and pressures on land as ingredients in aquaculture diets. More than 50% of
availability from urbanisation.
land use in carp farming and 40% of land use associated
As water becomes very scarce (prolonged and exten- with tilapia and catfish farming is attributable to pro-
sive droughts, for example) or altered through climate duction of crop‐based aquaculture feedstuffs. Globally
change, the likelihood of conflicts over water resources the amount of land used for aquaculture is small.
increases. Access to transboundary water resources may
become a more significant source of contention than As aquaculture grows, more land will be required to
energy or minerals in the coming decades. Historically, produce fish feeds, but the world is already farming its
water tensions have led to more water‐sharing agree- most productive land. The world loses 12 million ha
ments than violent conflicts, but this pattern could of productive agricultural land, capable of producing
change in the face of future risks. 20 million t of grain, each year to land degradation result-
ing from poor farming practices and deforestation. Given
Most aquaculture is conducted in fresh water and com- the limited availability of new agricultural land, improving
petition for this increasingly scarce resource is a much crop efficiency will be essential to meeting global food
greater problem than the availability of land. Pond aqua- needs. Sustainable intensification is the challenge for
culture does not use much water (5–10 m3/kg), but needs future agriculture. Intensive irrigated agriculture (includ-
good quality water, which may be polluted by other users, ing pond aquaculture) will be responsible for most future
even where the absolute amount of water is otherwise suf- gains in crop production.
ficient. Water is also needed to produce the feed ingredi-
ents required to sustain fish production. On average, Land and space availability is a key constraint for
feed‐associated water consumption accounts for around aquaculture growth. It is important to emphasise that
9% of total water use per unit aquatic animal production, land in this case refers to a specific local place and not
the remainder used to fill and maintain water level in land in the abstract of the global aggregate. In developing
ponds. Water limitation will be a key constraint for aqua- countries and in agricultural areas, especially in the
culture going forward, not only for its obvious need to major aquaculture producing countries of Asia, conflicts
support increased production but also for the irrigation of over the use of land for fish farming are rare, in part
crops used to produce future aquafeeds. because aquaculture is a traditional activity with a social
licence to operate. In contrast, disagreements with
Water scarcity will force aquaculture to develop and property owners, fishing companies, commercial ship-
implement technology and practices to become more ping interests, and recreational users are common in
efficient with the use of water and other inputs. The more prosperous countries. Often, sites chosen are in or
scope to improve water use efficiency on existing farms adjacent to land of high ecological value such as coastal
through intensification is considerable (Verdegem and and riparian wetlands and flood plains. In the USA and
Bosma, 2009). Europe, permits for seaweed, shellfish, and caged finfish
aquaculture installations within sight of land are
27.2.2.2 Land and Space expensive and extremely difficult to obtain. In response,
In 2010, global aquaculture occupied nearly 20 million ha aquaculture has intensified and moved into less expen-
of land, including 12.7 million ha of inland (freshwater) sive areas where competition and conflict over visual
lakes and rivers, and 6.0 million ha of coastal, mostly footprint is minimal. Unfortunately, in some instances
brackish water areas. Aquaculture also indirectly used an this has translated into destruction of biodiverse wetlands,
additional 26.2 million ha in 2010 to grow the crops used including mangrove forests.
27.2.2.3 Forage Fish and Feeds The Future of Aquaculture 623
The spectacular growth of aquaculture over the last
few decades is directly attributable to the widespread In 2010, 15 million t of wild fish (or roughly one‐sixth
adoption of manufactured feed as a key production of the marine catch) was converted to fishmeal and fish
input. For Chinese carps, the species with the greatest oil, most of which was consumed by aquaculture.
global production, the culture system has shifted from Aquaculture uses about 80% of the global supply of fish-
inputs of animal manures and agricultural by‐products meal and more than 90% of fish oil. Thus, at this time, the
as organic fertilisers to feeding with pellets. The major dependence of aquaculture on supplies of fishmeal and
source of animal protein in aquaculture feeds is fishmeal fish oil is very high, especially in China (Cao et al., 2015).
derived from the harvest and processing of small pelagic Given the current high rate of use of fishmeal and fish oil
forage fish (e.g., anchovy, menhaden, sardines) from the by aquaculture, one of the major challenges faced by
marine environment (Figure 27.4). aquaculture is that current supplies are not sufficient to
support the required expansion of aquaculture produc-
Figure 27.4 Good management of fisheries for small pelagic tion (Naylor et al., 2009).
forage fish will be essential for the future expansion of
aquaculture. Source: Photograph by Etrusko25 (Own work Foto di Forage fisheries are generally well managed, but
Alessandro Duci). Reproduced under the terms of the Creative supplies are variable and often influenced by large‐scale
Commons Attribution share licence, CC BY-SA 3.0. climatic phenomena such as the El Niño‐Southern
Oscillation (Figure 27.5). In general, similar to other
capture fisheries, production from forage fisheries is
limited because they are being exploited at approximately
their maximum sustainable yield and are not expected to
increase. The high dependence of aquaculture on wild
fish as feed ingredients can exacerbate negative impacts
on marine food chains. Arguably the use of forage fish
for feeds is the most important global‐scale environmen-
tal impact of aquaculture.
Prices of fishmeal and fish oil have been increasing,
based on the high demand from aquaculture and other
uses, especially since 2000. The price of other ingredi-
ents is also rising. The price of soybean meal, the main
plant protein ingredient in aquaculture feeds, has
increased in direct relation to fishmeal. As the price of
feed ingredients increases, it is obvious that aquaculture
feed prices will correspondingly increase. Feed typically
represents 50% or more of production costs and so price
14 000 000
Peruvian anchovy
7 000 000
0
1950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010
Figure 27.5 Global capture of Peruvian anchoveta, 1950–2010, indicating substantial fluctuation in annual catch. Source: Photograph by
Epipelagic. Reproduced under the terms of the Creative Commons Attribution share licence, CC BY-SA 3.0.
624 Aquaculture the crops used as feed ingredients. The intensification of
aquaculture will require more direct energy, especially
increases for fishmeal and feeds can have a profound for aeration, and indirect energy in the form of feeds.
impact on economic sustainability. The energy efficiency of farmed fish production, measured
as industrial energy input per protein energy output, is
The incorporation rate of fishmeal into feeds varies by better than that of most terrestrial livestock production.
species. Herbivorous and omnivorous species like carp,
tilapia, and catfish use relatively low levels of dietary It is unlikely that energy will be a resource that will
fishmeal and fish oil—usually less than 5% fishmeal and limit aquaculture in the future, but the desirability of
1% fish oil—and research has shown that these fish can continuing to use non‐renewable energy sources in light
be grown on feeds completely devoid of fish products. of attempts to curb greenhouse gas emissions will be a
However, for carnivorous species like salmon, marine big question going forward. The broader goal of reduc-
finfish, and marine shrimp, much higher levels are used ing greenhouse gas emissions to limit global climate
in feeds. It remains to be seen what kinds of species shifts change conflicts with the necessity of using more energy
will occur in response to higher fishmeal and fish oil to drive the intensification of aquaculture. Access to
prices. Although incorporation rates are low, most fish- energy supplies in the form of local electricity infra-
meal is used in diets for omnivorous carps and thus feed structure is more important than any large‐scale energy
prices would not be expected to be very sensitive to resource availability.
changes in the price of fishmeal (Tacon and Metian,
2015). Species with higher dietary incorporation rates of There are inevitable trade‐offs between land, water,
fishmeal tend to be higher‐value marine fish and shrimp energy, and feeds. For example, freshwater pond produc-
and these would be expected to be sensitive to fishmeal tion systems use energy and feeds efficiently, but can
price increases because consumers would be less willing consume more than 10 m3 of water per kg of fish pro-
to pay the high prices for such fish. On the other hand, duced when ponds are drained and refilled and to replace
rising affluence and shifting consumer preferences sug- water lost through seepage and evaporation. Closed,
gests that production of high‐value species will continue recirculating systems use little land and water (<2 m3/kg)
to expand. but require large amounts of energy. Marine finfish
farming directly uses practically no land or freshwater
The general trend has been towards reduced incorpo- but is going to have to innovate to replace increasingly
ration rates of fishmeal and fish oil in aquaculture feeds scarce and expensive fishmeal in diets. Trade‐offs will be
(Naylor et al., 2009). Fishmeal replacement is an active decided on the basis of the availability and price of the
and on‐going area of research and development and most limiting resource in a particular setting.
good progress has been made. Finding substitutes for
fish oil has proven much more difficult than replace- 27.2.2.5 Ecosystem Services
ments for fishmeal, suggesting that fish oil might limit There are growing pressures and demands on ecosys-
the expansion of aquaculture of high‐value species with a tems caused by population growth, human activities, and
high requirement for certain essential fatty acids. Many the shifting consumption patterns that result in increased
of the species important for food security in developing per capita resource use. Collectively these are causing
countries can be grown on diets with exclusively plant‐ ecosystem degradation, biodiversity loss, and an erosion
based protein sources. Furthermore, improvements in of life‐supporting ecosystem services. These also have
feed formulation and manufacture and especially feeding impacts on agriculture and fisheries production. The
practices have resulted in a better conversion efficiency main environmental pollutants are greenhouse gases,
of feeds to fish. fertiliser nutrients, and chemicals from industrial facili-
ties, especially persistent bioaccumulative toxins. Effluents
27.2.2.4 Energy from agriculture and wastewater treatment are projected
There is considerable uncertainty about future energy to increase, leading to detrimental effects such as
supplies, but relatively recent use of hydraulic fracturing eutrophication and acidification. For example, by 2050,
(‘fracking’) technology has resulted in a glut in supplies the number of lakes with hypoxia is expected to increase
of natural gas and oil reserves that were previously una- by 20%, most in Asia, Africa, and Brazil.
vailable using conventional technology. Aquaculture
uses about 1% of the energy in the global food system and Biodiversity loss is being caused by habitat fragmenta-
most of that energy is currently derived from fossil fuels. tion, resource overexploitation, environmental pollution,
invasive species, and climate change. The rate of biodi-
In aquaculture, the main direct uses of energy are for versity loss shows no sign of slowing. Despite an
water pumping and aeration. Overall, the biggest energy increased number of protected areas, deforestation of
demand in aquaculture is for capture of wild fish and tropical forests and conversion of wetlands and range-
reduction into fishmeal and fish oil for feeds (Hall et al., lands to cropland or urban areas represent irreversible
2011). Considerable embodied energy is contained in
aquaculture feeds, including the energy used to produce
loss of habitat and associated biodiversity. Reduced The Future of Aquaculture 625
catches of wild fish have increased the demand for
farmed fish, putting additional pressure on terrestrial decreased rainfall are expected to reduce yields of wheat,
ecosystems associated with the need for crop‐based feed rice, and corn.
ingredients. The trends of ecosystem degradation and
biodiversity loss will be exacerbated by climate change. The effects of climate change will disproportionately
In addition, the rapid expansion in crops used for biofu- affect disadvantaged people in developing countries.
els production has put additional pressure on terrestrial Climate change is already accelerating instability in
ecosystems and water resources. vulnerable areas of the world and the associated arising
resource scarcities are contributing to conflicts.
Ecosystem degradation and biodiversity loss are
leading to a loss of provisioning, regulating, and cultural The implications of climate change for aquaculture in
ecosystem services. Non‐market ecosystem goods and the future are profound. As climate change results in
services provide a majority of the total income of the increased frequency of droughts and extreme weather,
rural poor in many developing countries. Thus, the disruptions to pond‐based production can be expected.
effects of losses of ecosystem services will dispropor- Furthermore, reduced crop yields and increased demand
tionately affect vulnerable poor people in developing associated with population growth and economic growth
countries. will create scarcity and increase prices of commodity
crops used to produce aquaculture feeds. Sea level rise
27.2.3 Climate Change and extreme weather will increase the vulnerability of
Agriculture accounts for 35% of greenhouse gas emis- aquaculture in the coastal zone, including coastal shrimp
sions, and about 18% of emissions come from meat and fish ponds, shellfish rafts, and fish cages, especially
production. In 2010, aquaculture production contributed in Asia where there is abundant aquaculture infrastruc-
about 330 million t of CO2 in greenhouse gas emissions, ture (Figure 27.6). Ocean acidification will challenge
equal to about 5% of emissions from agricultural pro- the sustainability of coastal bivalve shellfish aquaculture.
duction and less than 1% of total global anthropogenic It is likely that global climate change will exacerbate
emissions. The accumulation of greenhouse gases from the susceptibility of aquaculture to disease events.
anthropogenic emissions has led to climate change,
challenging the resilience of natural ecosystems and The costs of climate change mitigation and adaptation
human‐built infrastructure. Throughout this century, will be enormous. Human communities can be buffered
climate change is projected to slow the rate of economic against adverse impacts of climate change through
development, erode food security, and increase income ‘adaptation services’ from coastal wetlands serving as
inequality to cause the displacement and migration of buffers against storm surge, for example. For the exist-
people. ing coastal pond infrastructure, it is prudent to begin
coastline fortification soon, followed by a gradual retreat
Average global air temperature is predicted to increase from the coast to more inland areas by the next century.
by 0.5–1.5°C by 2030 and impacts are expected to accel- The reality of climate change will require advance plan-
erate beyond a global temperature increase of 1–2°C. ning to implement measures to adapt or mitigate climate
Global ocean temperature in the upper 100 m is projected change impacts, especially for millions of highly vulner-
to increase by 0.6–2.0°C by 2100. Thermal expansion of able small‐scale fish farmers. Of necessity, developing
warming ocean water and melting of ice sheets and gla- resiliency will be a part of sustainable development
ciers are very likely to cause an increase in global mean strategies.
sea level of 10–35 cm by 2050. Climate change has also
resulted in the increased frequency of extreme weather 27.3 Responding to the Challenges
events, such as storms and droughts. By 2050, the costs of the Future
of extreme weather could reach 1% of global GDP per
year. About 20–35% of CO2 emissions are taken up by 27.3.1 Increasing Resource Use Efficiency
oceans, leading to ocean acidification. Increasing the resource use efficiency of any food
production activity is inherently desirable, resulting in
Climate change threatens unique and vulnerable beneficial (or less damaging) environmental effects and
ecosystems like coral reefs. In terrestrial and freshwater improved economic performance. However, resource
ecosystems, climate change causes biodiversity losses use efficiency in aquaculture should be considered in the
and increased colonisation by invasive species. The com- broader comparative context of resource use in animal
bined effects of sea‐level rise, coastal erosion, pollution, agriculture. Fish in aquaculture can convert the protein
and ocean acidification threaten coastal ecosystems. and grains in feed to fish protein more efficiently than
With respect to agriculture, increased temperature and most terrestrial livestock. Culture of extractive species,
such as molluscan shellfish, are among the most efficient
626 Aquaculture
Figure 27.6 Coastal aquaculture ponds, like these on the Bohai Sea, China, are vulnerable to the effects of climate change. Source:
Photograph by Planet Labs inc. Reproduced under the terms of the Creative Commons Attribution share licence, CC BY-SA 4.0.
animal protein production systems of all. Seaweeds Scarcity of water, land, feeds and energy has increased
actually make a net positive contribution to water quality their prices, driving aquaculture producers to increase
by capturing nutrients emitted from agriculture or fed the efficiency of farming operations out of self‐interest.
aquaculture. Among fed species, culture of relatively These trends of increased resource scarcity driving effi-
low trophic level, omnivorous fish are among the more ciency and intensification are likely to continue. Resource
efficient, with efficiency greater than many terrestrial scarcity has also driven private sector investment in
animal protein production systems (Hall et al., 2011). research and innovation, resulting in further efficiency
The resource use efficiency of higher trophic level spe- improvements. For example:
cies such as salmon and marine finfish approximates that ●● Scarce land has caused fish farmers in China and
of poultry and has much more scope for improvement.
Thus, aquaculture can play a role in improving the over- Vietnam to greatly intensify production in ponds, with
all environmental efficiency of animal protein produc- yields five or more times higher than the global
tion in the broadest sense. Aquaculture can add resilience average.
to the food system if the culture of lower trophic level ●● A limited supply of fishmeal and fish oil, and competi-
species is emphasised (Troell et al., 2014). The relative tion from other sectors for these resources (e.g., the
efficiency of certain kinds of aquaculture can be a neutraceutical industry4 that produces fish oil pills)
stimulus or incentive for more aquaculture, increasing
production efficiency, and shifting production to more 4 Nutraceuticals are products derived from food sources that are
efficient species. purported to provide extra health benefits, in addition to the basic
nutritional value found in foods
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