Monitoring the abundance of lake trout, Salvelinus namaycush, with index netting

grantor: University of TorontoThe catch-per-unit-effort (CUE) from index netting is commonly used as an index of abundance. Catchability, a proportionality parameter, relates the index of abundance (CUE) to the actual abundance of the population. Catchability was measured for a spring littoral index netting method used by the Ontario Ministry of Natural Resources to estimate the density of lake trout populations province-wide. The catchability of this method was modeled as a function of population density and lake size. Across lakes, catchability was found to decrease with density and increase with lake surface area. In one lake the catchability of lake trout in bottom-set gillnets was observed to be two-times higher in the spring compared to summer due to seasonal shifts in lake trout foraging and spatial distribution. Consequently, among-lake variation in catchability may be more pronounced in the summer due to differences in trophic structure making the interpretation of CUE more difficult.M.Sc