Research Document - 2013/047
Morphology and life history of the Great Slave Lake ciscoes (Salmoniformes: Coregoninae)
By A.M. Muir, P. Vecsei, M. Power, C.C. Krueger, and J.D. Reist
Abstract
The ciscoes (Salmoniformes: Coregoninae) have radiated into complexes of closely related species, life history types, and ecological variants. The taxonomy of the North American ciscoes remains unresolved. We provide the first comprehensive description of the Great Slave Lake ciscoes by comparing gross body morphology, phenotypic and life history traits, and habitat use among morphs, and assessing the validity of morphs within the context of existing taxonomy. At a minimum, our analysis supports the hypothesis that the Great Slave Lake ciscoes include two strongly differentiated species (Coregonus artedi and C. sardinella) and an adfluvial C. artedi morph that is distinct from its lacustrine conspecific in terms of life history, morphology, age, growth, and mortality. C. sardinella has previously been identified from Great Slave Lake, but we provide the first comprehensive description of this species in the lake and confirm a significant range extension for the species. The lacustrine C. artedi differs little from descriptions throughout its range. In addition to these three ciscoes, linear phenotypic traits, gillraker number and morphology, and growth data support the possible occurrence of two other, less-distinct morphs, the big-eye cisco C. artedi and C. zenithicus. Although the big-eye morph was not identified by cluster analysis of body shape and linear phenotypic measures, it was visually identified on the basis of differences in traditional phenotypic proportions, such as eye diameter, paired fin lengths, and head and gillraker morphology expressed as thousands of standard length. In addition, the big-eye morph showed different age and growth structure compared to the other lacustrine cisco morphs. C. zenithicus was distinguished visually and by the statistical model of linear phenotypic traits as well as by gillraker number and morphology, which were within the range for the species across its distribution. Identifying, characterizing, and managing locally-adapted cisco morphs that reflect important ecological and bioenergetic linkages is critical to conserving the ecological integrity of northern ecosystems.
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