Comparison of life history traits between anadromous and lacustrine stocks of broad whitefish (Coregonus nasus): An intra-specific test of Roff’s hypothesis
Vangerwen-Toyne, M.; Tallman, R.F.; Gillis, D.
Roff (1992) hypothesized that more migratory fishes would have later maturity, higher fecundity and faster growth than less migratory forms. We compared the demographic structure of anadromous and lacustrine populations of broad whitefish (Coregonus nasus) to determine if vital rates would conform to expectation. Size-at-age (otolith annulus measurements), reproductive effort (fecundity and egg size), and observed age-at-maturity were compared between two anadromous populations, the Peel River and Arctic Red River, and a lacustrine population in Travaillant Lake. Populations were minimally exploited and selected from the same latitude to avoid extraneous effects. Fish from the anadromous populations were not the same size-at-age until age 15 and beyond. Fish from Travaillant Lake were larger than the fish from the Peel River at all ages, but similar to those from Arctic Red River from age two to nine years. The anadromous populations were not significantly different in estimates of fecundity, but both were significantly more fecund than fish from Travaillant Lake. Observed age-at-maturity for fish in the Peel and Arctic Red Rivers were age 7 and 6 years, respectively, compared to 6 years for Travaillant Lake. We conclude that for broad whitefish, Roff’s predictions may only be applicable to the reproductive trait of fecundity. Unlike other anadromous species, freshwater existence was not associated with younger age-at-maturity or lower growth rate. We provide some explanations why the characteristics we observed did not correspond to Roff’s predictions.