Determination of fish community composition in the untempered regions of a thermal effluent canal--the efficacy of a fixed underwater videography system.

High flows and deep waters associated with thermal discharge canals invoke safety concerns and preclude the use of conventional fish sampling methodologies. Despite these challenges, it is critical that assessments of thermal effects from power generation do not rely solely on data collected in the plume, but also focus on fish living in the canal, particularly in regions above the zone of tempering influence. We deployed a fixed underwater videography apparatus to monitor the community composition and abundance patterns of fish in the Nanticoke thermal generating discharge canal on the north shore of Lake Erie from February 1, 1999 until July 31, 1999. We also compared the number of species observed using video to angling surveys, visual observations through the air/water interface and two modified netting procedures. Our results indicate that videography permitted the detection of the most species and the highest number of individuals. Variable visibility was the largest limitation of this approach. The addition of infrared lighting for low light conditions and a series of cameras positioned at several depths would be a cost effective, safe, and efficient method of assessing community structure and behaviour of fish in thermal discharge canals.