Evidence for resource polymorphism in the lake charr (Salvelinus namaycush) population of Great Bear Lake, Northwest Territories, Canada

We sampled lake charr, Salvelinus namaycush, from Great Bear Lake, Northwest Territories, Canada, from June 30 to August 28, 2000. We assessed morphological variation in relation to stomach contents, age, and growth history of individual fish. We found significant differences in the morphology of insect-eating lake charr and fish-eating lake charr, specifically upper and lower jaw length, pectoral fin length, and caudal-peduncle depth. The age at capture did not vary between feeding types. However, otolith increment-width differences in the first 19 y of life were highly significant between feeding types. These results suggest that piscivorous lake charr grew faster than did insectivores. Our results support the hypothesis of trophic polymorphism in the lake charr in Great Bear Lake.