Fatty acid signatures and stomach contents of four sympatric Lake Trout: assessment of trophic patterns among morphotypes in Great Bear Lake

• Published in: Ecology of Freshwater Fish
• Main Authors: Chavarie, Louise, Howland, Kimberly, Gallagher, Colin, Tonn, William
• Other Authors: Fisheries and Oceans Canada, Natural Sciences and Engineering Research Council of Canada, Association of Canadian Universities for Research in Astronomy
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2014
• Subjects: Great Bear Lake
• Online Access: http://dx.doi.org/10.1111/eff.12195; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Feff.12195; https://onlinelibrary.wiley.com/doi/pdf/10.1111/eff.12195

Abstract Sympatric diversification in L ake T rout is generally linked to differences in habitat use (especially depth) as a result of foraging on different prey items. However, extensive sympatric divergence has taken place in the shallow waters (≤30 m) of G reat B ear L ake, with multiple L ake T rout morphs varying in head and fin characteristics. To investigate diet partitioning as a potential explanatory mechanism for this diversification, we assessed trophic characteristics and relationships among four sympatric shallow‐water morphs of L ake T rout via analyses of fatty acids and stomach contents. Fatty acids and stomach contents both identified L ake T rout, C isco and M ysis as key prey items in L ake T rout diets. Interestingly, terrestrial invertebrates were also seasonally important among morphs, reflecting temporal variability of available prey in this arctic lake. Some diet partitioning was observed among morphs; M orph 1 was characterised as a generalist, M orph 3 was more benthic‐oriented, and M orphs 2 and 4 were mainly pelagic feeders. Of the latter, M orph 4 was the most specialised, whereas M orph 2 exhibited alternative feeding tactics of benthic cannibalistic and pelagic piscivorous feeding. Our findings demonstrate that complementary dietary methods can elucidate habits of opportunistic feeders, a task that can often be problematic, given their complex and variable diets. Our results add new information and perspectives on the current model of L ake T rout differentiation, demonstrating niche partitioning based on benthic versus pelagic habitat use and generalist versus specialist feeding tactics.