Habitat overlap of juvenile and adult lake trout of Great Bear Lake: Evidence for lack of a predation gradient?

• Published in: Ecology of Freshwater Fish
• Main Authors: Chavarie, Louise, Howland, Kimberly L., Harris, Les N., Hansen, Mike J., Gallagher, Colin P., Harford, William J., Tonn, William M., Muir, Andrew M., Krueger, Charles C.
• Other Authors: Fisheries and Oceans Canada, Great Lakes Fishery Commission
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2019
• Subjects: Great Bear Lake
• Online Access: http://dx.doi.org/10.1111/eff.12470; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Feff.12470; https://onlinelibrary.wiley.com/doi/pdf/10.1111/eff.12470; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/eff.12470

Abstract A range of organisms, from plankton to fish, commonly shift their habitat distributions horizontally or vertically due to predation risk. Juvenile lake trout, Salvelinus namaycush , are generally viewed as occupying deep areas of lakes to decrease predation pressure from adults. In contrast, we found that juvenile lake trout from Great Bear Lake, NT, Canada, occupied a variety of habitats and from shallow to deep depths (0–150 m), overlapping with adult lake trout. No evidence occurred for a length depth‐based segregation (e.g., ontogenetic shift). Genetic variation was also similar among juveniles in the different depth zones. However, isotopic niches and C:N ratios among juveniles showed some variability in niche widths and positions for individuals caught from the 51–150 m zone compared to juvenile individuals caught from 0–20 m and 21–50 m zones. The uniformly distributed adult lake trout in Great Bear Lake may evenly distribute predation pressure (including cannibalism) across shallow‐ and deep‐water habitats more than in other lakes. As a result, juveniles may respond to differences in foraging opportunities rather than predation risks. Juvenile lake trout did not appear to conform to the general pattern of juveniles seeking a deep‐water refuge to reduce predation risks. In contrast, juvenile lake trout of Great Bear Lake displayed broad resource use across all depths and habitats.