Age and Size at Sexual Maturity of Heavily Exploited Arctic Char and Brown Trout in Lake Atnsjø, Southeastern Norway

Abstract

In Lake Atnsjo, Southeastern Norway, Arctic char Salvelinus alpinus and brown trout Salmo trutta both attained sexual maturity mainly at 6 years of age and older, usually at a body length larger than 26 cm. Both species have been heavily exploited at least since the turn of the century. The annual survival rate was estimated at 0.38 for Arctic char (age-groups 6–9) and 0.49 for brown trout (age-groups 4–9). Mean female age at maturity was higher than the optimal age at maturity predicted if female reproductive success only depended on fecundity. We argue that reproductive advantages of larger parental body size, due to high competitive ability during spawning, favored late female maturation and also limited the selective effect by the fishery for earlier maturation.