I. Aquatic Connectivity

Drivers & Stressors Condition of the bay human connections

I. Aquatic Connectivity

Sea-Run Fish Regaining Access to the
Presumpscot Watershed

Relic Dams Block Fish from Swimming Up Royal River, Stroudwater River,
and Some Coastal Streams
RiveRrIVEHReHrEriRRInNgG /pYeErARYear
why it matters status & trends Jerry Monkman, Ecophotography.com

Being able to move freely among different types of habitats Connectivity between aquatic habitats in Casco Bay and
is essential for many aquatic species. Anadromous fish such the Presumpscot River watershed has steadily expanded
as river herring, shad, and rainbow smelt, which are prey for since the 1990s as a result of concerted efforts by NGOs,
commercially important saltwater fish like cod and haddock, state and federal agencies, and businesses to remove
must be able to migrate upstream from estuaries to fresh dams, construct technical fishways, and replace inade-
water each spring to reach spawning habitat. Eastern brook quate culverts. These efforts have facilitated restoration
trout and other fish that require cold, oxygen-rich water move of alewife, blueback herring, and shad runs into some
seasonally among spring-fed streams, mainstem rivers, and historical spawning habitats in the Presumpscot River
estuaries in order to reproduce and feed. Terrestrial animals watershed. These efforts have also benefited sea-run
often travel and feed along rivers and streams. brook trout.

Construction of dams, roads, and railways in Casco Bay's Fish Returning to SpawnHighland LakeDam in PresumpscotCumberland MillsDam River

watershed severed many of these vital linkages and caused 112200,0,0000 Cumberland Mills Fishway
110000,0,0000 Highland Lake Fishway
severe declines in anadromous fish populations. Dams block

passage between upstream and downstream habitats, and 8800,0,00000

interrupt the natural movement

of sediment, wood, nutrients, 6600,0,0000

and floodwaters. Where roads 4400,0,0000

and railways cross waterways, 2200,0,0000

inadequate culverts often -0

impede fish passage. Cold- Total ann220u0040a4 l 22r000e50t5u22r000n60s6 o22000f70r7iv220e0080r8 h220e0090r9rin22010g010(a220l10e111w2i20f10e212, b22010l3u13e2b2010a414ck220105h15e2r20r106i1n6 g220,107a17 n2d2010818 22010919
shad) at two counting stations in the Presumpscot River watershed. The
water species cannot thrive number of returning fish remains variable, peaking in 2018 with over
117,000 observations, but there is potential for continued growth now
in the warm, oxygen-impaired that fishway construction is complete at Saccarappa Falls in Westbrook.

This perched, slip-lined round culvert waters behind dams and Source: University of Southern Maine; Maine Department of Marine Resources
obstructs movement of fish and perched culverts.
other aquatic organisms. (Photo:
Maine Stream Habitat Viewer)

Current and Historical Amounts of Sea-Run Fish Habitat

Presumpscot RIver ROYAL RIver Coastal/other total

Species Units Current Historical Current Historical Current Historical Current Historical

Alewife Acres 640 31,597 0 460 85 85 725 32,142

Blueback Herring Miles 11.7 24.2* 0.3 60.0 0 0 12.0 84.2

American Shad Miles 11.7 24.2* 0.3 60.0 0 0 12.0 84.2

Sea-Run Rainbow Smelt Sites 2 2 22 19 37 23 41

* Minimum mileage only. May be substantially higher if additional tributaries were shown to be historical habitat.
Note that habitat for other sea-run species such as American eel, sea-run brook trout, and sea lamprey exists in Casco Bay streams, but data for those habitats is either not
available or not reflected here to focus on the species above. Source: U.S. Fish and Wildlife Service (2015)

21 casco BAY estuary partnership

condition of the bay Bethel I. Aquatic Connectivity
Mason
Twp

Greenwood

AlbaBneythTewl p Many Fish Spawning Habitats Remain Blocked by
Dams and Substandard Culverts
StonMehaasomn
Orange indicates historical spawn-
Twp ing habitats for blueback herring,
American shad, and alewife that the
Greenwood fish currently cannot access because
of dams and culverts. A survey of the
Albany Twp Norway Casco Bay watershed in 2008-2010
found 573 severe (or assumed severe)
LSotovneellham barriers and 551 potential barriers to
Waterford fish passage.

Lovell Norway

Sweden Waterford Harrison

SwedeBnridgton Otisfield Auburn Alewives encountering a barrier in Mill

Harrison Brook, Westbrook. (Photo: Jerry Monk-
man, Ecophotography.com)
Poland

Otisfield Auburn

Bridgton Poland

Denmark

Naples Casco Durham

Denmark Raymond New Gloucester

Naples Casco Durham Bath
West
Sebago Raymond New Gloucester Bath

Hiram Sebago Gray Freeport Brunswick Bath
Pownal
Hiram Baldwin Gray West
Frye
Baldwin Island NorthPYoawrnmaol uthFreeport Brunswick Bath

Frye North Yarmouth
Island
Windham Cumberland
Royal River
WindhamPresumpscot River Yarmouth

Standish Cumberland

Falmouth Yarmouth

Standish Falmouth

Dam Chebeague
SeDaa-rmun rainbow smelt site Chebeague Island
Westbrook Harpswell
Sea-run rainbow smelt site Island
BAlmuABeelmbruieaecCbrcaiakcunCcarhksurneehrhsrnraeehrtndrainrtdirngergeaaaacncnhdhdeess GorhamWestbrook Portland Harpswell
Buxton Gorham Portland Phippsburg
HisHtiostroicriacl Phippsburg
AleAwleifweifpeopnodnsds Buxton Long
Long Island
AcAccecsessisbiblele South South Island Portland
InaIncaccecsessisbiblele PortlanPdortland Portland

ScarbSocraorubgohrough Cape Cape
SacSoaco ElizabethElizabeth

successes & challenges

▶ Maine is a national leader in restoration of stream connectivity. Maine’s Stream Smart training program
guides the process of designing and replacing culverts, and the Maine Department of Environmental
Protection provides grant funds for addressing derelict municipal culverts. Despite many successes,
much work remains, as over 80 percent of culverts pose a barrier to passage of aquatic organisms.

▶ The pace of dam removal remains slow even though most dams in the Casco Bay watershed are
decades, if not centuries, old and no longer serve their original purpose. Despite the compelling
ecological and resilience benefits of dam removal, some people are reluctant to embrace the
necessary changes in river recreation (e.g., flatwater paddling, fishing, and ice skating) and scenery.

STATE OF casco BAY 22