Variation in Acute Thermal Tolerance within and among Hatchery Strains of Brook Trout

Abstract

AbstractThe ability of coldwater species and populations to respond to temperature increases associated with climate change will depend on the existing adaptive potential within and among populations. Brook trout Salvelinus fontinalis is a valued coldwater species that has been widely stocked across its native range as well as extensively introduced in western North America. We investigated the thermal tolerance of the three primary brook trout hatchery strains used in Ontario (Dickson Lake, Lake Nipigon, and Hill's Lake strains) and the thermal tolerance of a brook trout subspecies, Aurora trout S. fontinalis timagamiensis; all strains were reared in a common hatchery environment. In addition to comparing the strains’ responses to acute thermal stress, we also examined variability in temperature tolerance among families within several of these strains. Evidence for significant differences in temperature tolerance was observed both within and among the strains, with Aurora trout showing the least capacity to cope with higher temperatures. The results of this study suggest that thermal performance of brook trout populations will be under substantial selective pressure as water temperatures increase and that strains with existing tolerances for warmer conditions will be better equipped to handle these anticipated changes.