Contrasting phenotypic variation among river and lake caught cisco from Great Slave Lake: Evidence for dwarf and large morphs

► We assessed cisco in Great Slave Lake to determine if different morphs exist. ► Analyses of phenotypic data assigned 2 morphs: (1) adfluvial and (2) lacustrine. ► Adfluvial ciscoes were young, small, and fusiform relative to the lacustrine morph. ► Results suggest morph evolution was driven by ecological and not human factors.