Maternal effects in vulnerability to eye-parasites and correlations between behavior and parasitism in juvenile Arctic charr

摘要

Hatchery-reared fish show high mortalities after release to the wild environment.Explanations for this include potentially predetermined genetics, behavioral, and physiologicalacclimation to fish farm environments, and increased vulnerability to predationand parasitism in the wild. We studied vulnerability to Diplostomum spp. parasites(load of eye flukes in the lenses), immune defense (relative spleen size) and antipredatorbehaviors (approaches toward predator odor, freezing, and swimming activity) inhatchery-reared juvenile Arctic charr (Salvelinus alpinus) using a nested mating design.Fish were exposed to eye-fluke larvae via the incoming water at the hatchery. Fish sizewas positively associated with parasite load, but we did not find any relationshipbetween relative spleen size and parasitism. The offspring of different females showedsignificant variation in their parasite load within sires, implying a dam effect in thevulnerability to parasites. However, the family background did not have any effect onspleen size. In the mean sire level over dams, the fish from the bolder (actively swimming)families in the predator trials suffered higher loads of eye flukes than those frommore cautiously behaving families. Thus, the results indicate potentially maternallyinherited differences in vulnerability to eye-fluke parasites, and that the vulnerabilityto parasites and behavioral activity are positively associated with each other at the sirelevel. This could lead to artificial and unintentional selection for increased vulnerabilityto both parasitism and predation if these traits are favored in fish farm environments.