Lake Ontario August gillnet survey and Lake Trout assessment, 2023

Abstract

Lake Ontario lake trout ( Salvelinus namaycush ) rehabilitation has been annually assessed with fishery independent surveys since 1983, to evaluate program benchmarks and compare observations with management objectives. These surveys provide information on the abundance, strain composition, and condition of the adult lake trout stock, as well as information on levels of natural recruitment, sea lamprey ( Petromyzon marinus ) wounding rates, and abundance indices of other coldwater fish species (burbot Lota lota , cisco C oregonus artedi , and lake whitefish C. clupeaformis ). In 2023, the catch per unit effort (CPUE) of total lake trout in gillnets was notably lower (12.1 fish/net) compared to recent survey years 2018–2022 (average = 17.3 ± 1.0 SD fish/net). CPUE of mature females fell below target levels. Wildproduced mature lake trout remain rare in the adult population (1.0% of adult catch). Strain composition of stocked fish indicated approximately half (51%) of all coded wire tagged lake trout captured in 2023 were from the Superior Klondike strain. Sea lamprey wounding rates decreased in 2023 and were near the target level (2.09 A1 wounds per 100 lake trout). Lake trout condition (predicted weight at length) remains high. Overall, the 2023 survey results suggest that lake trout indicators continue to meet some of the management objectives, however, recruitment of wild-produced offspring to the adult stock continues to be limited, and abundance of stocked fish may be decreasing relative to recent years in response to reduced stocking levels.