Evaluating the Effectiveness of the Pickering Nuclear Generating Station Fish Diversion System Barrier Net

Barrier nets can be an effective alternative for reducing fish impingement mortality at power plant intakes. In 2010, a paired, split-beam hydroacoustic method was used as the primary assessment tool for comparing relative fish density between the lake (“outside”) and station (“inside”) side of the Pickering Nuclear Generating Station fish diversion system (FDS) barrier net. Behavioural information was also collected using a DIDSON acoustic camera and underwater video camera to determine fish responses to the FDS. Verification monitoring was completed using conventional netting. The DIDSON provided useful and valuable information on relative fish densities, relative school sizes and behaviour of fish as individuals, small groups or schools in response to the FDS. Analysis of the hydroacoustic data based on the weighted average biomass indicated that FDS effectiveness was 75, 98, and 100% for the spring, summer, and fall periods, respectively. The summer and fall estimates were based on net performance under optimal net deployment conditions and if the net degrades, effectiveness is reduced significantly as observed in the spring data. Our study results were supported by impingement monitoring whereby impingement biomass was reduced by greater than 80% for each of the first three years post-installation compared to baseline conditions.