Population surveys of juvenile sockeye salmon (Oncorhynchus nerka) in Bowron Lake, British Columbia between 2017 and 2021 / by Lucas B. Pon and Garrett W. Lidin.: Fs97-13/1420E-PDF

"Bowron Lake serves as nursery rearing habitat for the COSEWIC listed Bowron Sockeye Salmon (Oncorhynchus nerka) population (DU 2; endangered). While adult returns to the Bowron system have been assessed on a regular basis, past juvenile abundance assessments have been limited. A renewed effort to monitor Bowron juveniles occurred with paired acoustic-trawl surveys in the fall of 2017, 2018, 2019, and 2021. This report details Sockeye Salmon and Kokanee (O. nerka) fry abundances and densities, as well as fish size data, and fry diet analyses. Kokanee were the primary competitor to Sockeye Salmon in all years, and were the dominant planktivorous species in years following low adult Sockeye returns. Sockeye Salmon fry were consistently larger than Kokanee in all years where comparisons could be made. Diet of juvenile O. nerka consisted primarily of Daphnia spp. and fry were generally found to be fairly well fed in all years. In some years of low returns, Sockeye fry abundance relative to the number of spawners appeared abnormally high, highlighting the potential challenges of enumeration under such conditions. Continued acoustic-trawl surveys of Bowron Lake are recommended as efforts to enhance the juvenile population with hatchery reared fry have been recently engaged by DFO's Salmonid Enhancement Program"--Abstract, page vii.

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