The Wrack

The Wrack is the Wells Reserve blog, our collective logbook on the web.

Pre-restoration fish surveys in Branch Brook

Posted by | June 14, 2012

Goal

Assess occurrence of migratory fish species in Branch Brook to establish a baseline prior to anticipated restoration and improvement of an inoperable fish ladder.

Project Background

Fish ladder at K K W Water District treatment plantThe fish passage structure at the Kennebunk/ Kennebunkport/ Wells Water District treatment plant dam is in disrepair and presents a barrier to aquatic species attempting to migrate upstream. About 95 percent of stream habitat within Branch Brook is therefore inaccessible to sea-run fish. The structure, located about 0.75 mile above head-of-tide, was built in 1954 (revitalized in 1995) and does not incorporate advances in fish passage technology made over the last six decades.

Historic counts at the fish ladder indicate the structure allows only three species of migratory fish to pass (brook trout, American eel, sea lamprey) all of which are regarded as highly mobile. An operable fish ladder would allow a greater variety of fish species, including alewife, blueback herring, and possibly Atlantic salmon, to pass upstream.

The Wells Reserve, the KK&W Water District, and Maine Rivers are pursuing the restoration and improvement of the Branch Brook fish ladder. If these efforts are successful, construction would occur in autumn 2012. Obtaining pre-restoration data is intended to help measure the success of restoration.

Project Period

Spring/Summer 2012

Activities

  • Survey mature fish above and below the fish ladder using fyke nets, gill nets, and electrofishing
  • Survey larval and juvenile fish above and below the fish ladder using ichthyoplankton tows and seines
  • Survey other potential stream barriers in the Branch Brook watershed

Principal Investigators

  • Michele Dionne
  • Jacob Aman

Key Findings

We documented 13 species of fish in both the estuarine and freshwater reaches of Branch Brook, four of which were identified as having restoration potential at the start of the project. Brook trout were the most abundant fish species sampled in freshwater habitat. We assessed stream habitat and riparian conditions at 10 locations in Branch Brook. Of these 10 sites, 4 contained gravel spawning substrates and riffle habitat favored by brook trout and sea lamprey, and these were located either upstream of the dam near the headwaters, or downstream of the dam on a tributary. Suitable spawning conditions for blueback herring were more limited, due to predominantly shallow water depths at most sites. However, habitat at one site between the dam and the head of tide offers deeper slow moving water with organic and silt substrates.

The presence of migratory fish downstream of the KKWWD dam, and the occurrence of spawning habitat upstream, demonstrates that restoration of fish passage will benefit target species, and that these benefits could be seen in the short term if fish currently utilizing the lower river are allowed upstream access.

Resulting Reports

Assessment of Pre-restoration Habitat Conditions and Fish Populations in Branch Brook (2.7 MB)

Funding

State Planning Office, Maine Coastal Program

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