Feasibility of estimating Chilko River Sockeye Smolt abundance using upward facing SONAR

The objective of this proposed work is to test the feasibility of using upward facing SONAR technology to assess daily abundances of Chilko Lake Sockeye as they migrate through the Chilko River in the spring 2019. This technology has proven to be effective for enumerating migrating smolts in comparable rivers in Alaska. The reliably of the method will be evaluated based on how well the daily SONAR-derived abundance indices predict the daily migration totals observed at the weir. If proven effective, the SONAR method would provide an alternate assessment method for the Chilko watershed that could be quickly employed in years when high flows either prevent the installation of the weir at the beginning of the migration, or necessitate the removal of the weir before the smolt migration is largely complete.

Additionally, if proven successful at Chilko, the upward facing SONAR method could potentially be used to assess Sockeye smolt populations in other areas of the Fraser watershed where population assessments are not currently conducted. Both the Cohen Report and the Fraser River Panel identified upstream juvenile Fraser Sockeye Salmon monitoring as a priority to address major data gaps. Expanding on this methodology, if deemed successful, would represent an important step to help improve stock specific information related to Fraser Sockeye productivity and an understanding of the potential limiting factors in the freshwater environment.