Biological characteristics of inland Lake Whitefish populations in Ontario

ObjectiveTo assess the biological characteristics of Lake Whitefish Coregonus clupeaformis within inland lakes in Ontario at multiple scales and test whether there have been any changes in relative abundance, measured by catch per unit effort, spatially and temporally over 15 years.MethodsA Broad-scale Monitoring Program, which uses a standardized random sample of the fish assemblage, has been conducted within inland lakes in Ontario since 2008 in roughly 5-year cycles on about 750 lakes. Lake Whitefish attribute and catch per unit effort data were used to assess variation in characteristics across the landscape.ResultFrom 2008 to 2022, 54,941 Lake Whitefish were sampled among 524 different water bodies. Lake Whitefish relative abundance varied among fisheries management zones (FMZs), but not across cycles within or among FMZs. Relative abundance of Lake Whitefish was greater in lakes with lower large-bodied fish species diversity, greater Secchi depth, mean depth, and higher levels of hypolimnetic dissolved oxygen. Their relative abundance was greatest in the 12-35-m depth strata. Growth potential, age, and length at 50% maturity were similar between the sexes at the provincial and FMZ scales. Mean annual survival for populations with at least 50 Lake Whitefish sampled was 87%.ConclusionThe demographics and relative abundance of Lake Whitefish throughout inland lakes in Ontario was indicative of limited exploitation on these populations at a landscape scale.