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

Abstract

AbstractBarrier nets can be an effective alternative for reducing impingement mortality of fish 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 while it was in place. Behavioral 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 gill netting. The DIDSON provided useful and valuable information on relative fish densities, relative school sizes, and behavior of fish as individuals, small groups, or schools on both the outside and inside of the FDS, as well as general behavior of fish approaching the FDS. There was no evidence of passage through the net based on DIDSON evaluation; however, fish passage occurred when the FDS net was considered to be in a degraded condition (from biofouling or storm events, or both) and passage occurred over the net, not through it. 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, and 98% for the three seasons combined. 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 at the station whereby impingement biomass was reduced by greater than 80% for each of the first 3 years after installation compared with before installation of the barrier net. Overall, the FDS was demonstrated to offer significant fish protection from potential impingement at the Pickering Nuclear Generating Station.Received July 21, 2013; accepted December 6, 2013