Morphology and life history of the G reat S lave L ake ciscoes ( S almoniformes: C oregonidae)

The taxonomy of the N orth A merican ciscoes ( S almoniformes: C oregonidae) remains unresolved. We provide the first comprehensive description of the G reat S lave L ake ciscoes. Our analysis supports the hypothesis that the G reat S lave L ake cisco complex includes at least two nominate species ( C oregonus artedi and C oregonus 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 oregonus sardinella has previously been identified from G reat S lave L ake, 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 and a shortjaw‐like morph C oregonus zenithicus . Although the big‐eye morph was not identified by body shape and linear phenotypic measures, it was visually identified on the basis of differences in traditional phenotypic proportions, such as orbital length, paired fin lengths, head and gillraker morphology expressed as thousands of standard length and showed different age and growth structure compared with the other lacustrine cisco morphs. C oregonus zenithicus was distinguished visually and by a statistical model of linear phenotypic traits as well as by gillraker number and morphology. Identifying, characterising and managing locally adapted cisco morphs that reflect important ecological and bioenergetic linkages are critical to conserving the ecological integrity of northern ecosystems.