Ecological Recovery in the Kennebec Estuary and Nearshore Marine Environment

Nathaniel Niles’15 (Earth and Oceanographic Science and Environmental Studies).  Bowdoin College. “Ecological Recovery in the Kennebec Estuary and Nearshore Marine Environment.” John Lichter, advisor.

Project Summary:
American Shad (Alosa sapidissima) is an anadromous fish species of significant ecological and economic importance in the Androscoggin River.  However, shad populations have seen declines due to overfishing, industrial pollution and dam building.  Each year shad return to the Androscoggin River to spawn, but the Brunswick hydroelectric dam prevents their upstream passage.  Although there is a fish ladder installed on the dam, it is unsuccessful at passing large numbers of shad (this year only 24 shad scaled the ladder).  Thus the dam prevents the shad from reaching nearly half of their historical breeding grounds, which extended to the base of the Lewiston falls (Neil Ward pers. comm.).  By allowing the shad to pass upstream of the dam, shad runs in the Androscoggin could see a significant increase.

In collaboration with the Androscoggin River Alliance and Brookfield Environmental, the dam owner, I conducted an experimental study that aims to determine if a fish lift installed at the Brunswick hydroelectric dam would attract shad into a collector bucket.  A fish lift acts as an elevator for fish and could be the best solution short of removing the dam for increasing the annual shad migration on the Androscoggin River.  As part of the study, an electrically powered flow inducer, consisting of two spinning turbines, was installed at the base of the dam.  The flow inducer increased the flow of water (200 cubic feet per second) to mimic the conditions of a fish lift.  Alternating every 24 hours, the flow inducer was turned on and off to allow for control and experimental conditions.  Additionally, two underwater cameras were installed in the tailrace of the dam, one at the entrance of the fishway and the other roughly 100 yards downstream.  The cameras streamed footage to computers installed at the dam which was processed by motion detection software, Salmonsoft FishTick.  The software compiled the footage, saving only the video in which fish were present.  Data, in the form of video, will help monitor and quantify the shad entering near the flow inducer.  Preliminary evidence suggests placement of a fish lift would have a significant effect on its efficacy.


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