Life-history variation in perch (Perca. fluviatilis L.) in five neighbouring Norwegian lakes

Perca fluviatilis L.) from five neighbouring lakes in Norway. The lakes vary in water quality, varying from strongly acidified (pHless than or equal to5.0) to not acidified (pHgreater than or equal to6.0). Estimated annual survival rates did not differ among populations. There was no strong relationship between age at maturity in female perch and acidification. However, age at maturity was lower for female perch from the most acidic lake (c. 2 years) compared with perch in the four other lakes (2.5-3.5 years). There was no relationship between acidification level and size-adjusted egg size, fecundity or reproductive investment (Gonadosomatic index - GSI). Perch in the most acidified lake showed large variation in egg size, the lowest length-specific fecundity, the highest GSI, and the lowest age at maturity. Environmental stress, such as acidification, induces a number of changes to a lake community. It is therefore difficult to predict how acidification will influence the population dynamics and reproductive biology of a perch population.