A preliminary assessment of cisco (Coregonus spp.) diversity in Yellowknife Bay, Great Slave Lake, Northwest Territories

Abstract

Northern freshwater fi shes, particularly members of the genus Coregonus, have been used as a model for studying microevolution due to their well known colonization history coupled with parallel patterns of phenotypic differentiation. We assessed and described the phenotypic diversity among ciscoes in the Yellowknife Bay region of Great Slave Lake using 1) traditional taxonomic methods for cisco species and 2) contemporary linear and geometric morphometric methods. Four morphs were identifi ed using a qualitative visual assessment of gross morphology and/or location of capture in comparison to published taxonomy for the genus Coregonus. The morphs identifi ed were assigned the following colloquial names: A) 'adfl uvial', B) 'lacustrine', C) 'shortjaw', and D) 'least'. Univariate analyses on taxonomic measures indicated that cisco varied in terms of age, number of lateral line scales, number of anal fi n rays, middle gill raker length, and lower gill arch length. By contrast, fi ve morphs were identifi ed using cluster analysis of linear and geometric morphometric data combined with age and gill raker number. The additional phenotypic cluster entailed a splitting of large and small lacustrine morphs into two groups. Multivariate analyses indicated a strong relationship between body shape and gill raker number, eye size, age and mouth morphology. These results suggested that the segregation among morphs was based on differential usage of trophic and/or habitat resources as well as life history variation such as age at maturity. Our results indicated that the level of phenotypic diversity was greater than previously documented for Great Slave Lake and that this diversity was similar to that reported for ciscoes in the Laurentian Great Lakes.