Developmental stability and environmental stress in Salmo salar (Atlantic salmon)

We have studied the developmental stability (measured as fluctuating asymmetry of five meristic characters) of three populations of Atlantic salmon Salmo salar (rivers Imsa, Lone and Ogna, western Norway). All three populations were both sampled in the wild, and hatched and reared in a common environment in a hatchery (with water from the river Imsa) from fertilization until smoltification. Both the Imsa and Lone hatchery populations have been sea-ranched in the Imsa for 10 years, whereas the Ogna populations is novel to the hatchery environment. Individual biochemical heterozygosity was scored at 50 loci, of which 11 were polymorphic. There was no correlation between biochemical heterozygosity and fluctuating asymmetry at the individual level, neither when tested within groups nor when tested between groups. There were no differences in fluctuating asymmetry between wild and hatchery Imsa and Lone fish, indicating that the hatchery environment did not disrupt early developmental homeostatic processes. However, the Ogna hatchery fish had significantly elevated levels of fluctuating asymmetry compared to the wild Ogna fish, indicating that the hatchery environment was hostile. The Ogna hatchery fish also had significantly higher fluctuating asymmetry than the Imsa hatchery and the Lone hatchery fish. Maladaptation to the hatchery environment is the most likely explanation for the increased asymmetry in river Ogna fish.