Assessing effects of tidal power development on fishes using hydroacoustics

Tidal power is becoming an increasingly viable alternative energy option for coastal communities across the nation.  Developments associated with the most advanced commercial tidal energy site in the United States, in Cobscook Bay, Maine, provide opportunities to develop effective observation and analysis techniques for determining the effects of large-scale cross-flow turbines on their local marine environment.  Fish communities are one component of the marine environment likely to be affected.  DIDSON acoustic cameras were used to observe the direct interaction of fish and other marine species with a barge-mounted pilot turbine.  In addition, SIMRAD echosounders (38 and 200 kHz) were placed up- and down-stream of the turbine to monitor the distribution of fish in the water column before and during turbine operation, allowing us to quantify the behavior of local fish species around a single turbine.  Before-After-Control-Impact studies have been initiated at proposed full-scale project deployment sites to assess possible changes in fish distribution.  DIDSON and mid-water trawling were used for species verification of hydroacoustic surveys.  Analyses from these methods will be used to provide feedback to engineers and regulators to minimize the impact of tidal energy projects on local ecology.