Evidence for two morphotypes of lake charr, Salvelinus namaycush, from Great Bear Lake, Northwest Territories, Canada

The lake charr, Salvelinus namaycush, is generally characterized as a morphologically stable specialized deepwater piscivore. Empirical observations suggested the existence of two or more morphotypes of lake charr in Great Bear Lake, NWT. I gathered morphological data over two seasons from a total of 72 individuals and used principal components analysis to summarize variation in the dataset. UPGMA classification showed that there were two groups in the dataset. I classified individuals into one of two morphotypes using discriminant function analysis. The two forms differed primarily in head proportions. I developed a function, usable in the field, that classifies 80% of all specimens correctly. This study represents one of the first documentations of sympatric morphotypes of lake charr outside the Laurentian Great Lakes and provides the basis for further investigation into origins of and genetic, morphological and ecological differences between the forms.