Lakeward Migrations by Juvenile Atlantic Salmon, Salmo salar

Abstract

Atlantic salmon parr, Salmo salar, undertook lakeward migrations from outlet streams in the Wings Brook system, eastern Newfoundland. Lakeward movement occurred from May through November, intensifying over a 6- to 8-wk period during spring. Parr remained in the lakes where they either matured (usually males) or smoltified (predominantly females) before returning to the streams. Mature parr emigrated from the lakes during autumn whereas smolts entered the streams during spring. Lakes provided conditions for increased parr growth and survival to the smolt stage relative to the riverine environment, and appeared to represent important overwintering habitat. Smolt production occurred almost entirely within the lakes. Parr movement into lakes could not be explained by physical environmental factors. Lakeward migrations appear to have an adaptive basis and can be explained as an evolutionarily stable reproductive tactic.