Characteristics of brown trout males influence growth and survival of their offspring

Half-sib groups of juvenile brown trout Salmo trutta (0+ years) having fathers with different characteristics were compared in several respects. Two kinds of experiments were performed, aquarium observations in the laboratory and stocking in a semi-natural stream. It was found in the aquarium experiments that the offspring of fathers with larger adipose fins were more active and were probably better at defending territories. Offspring of males chosen by females had higher growth rate. The feeding rate was higher in juveniles having a less aggressive father or a father that was chosen by the mother. The stream experiments showed that offspring of dominant males had higher growth rates, and that offspring of less aggressive fathers had higher survival. Thus, characteristics of the males (fathers) influences the quality of the offspring, and there seem to be benefits for the females both to choose among potential mates and to spawn with the most dominant male. As these male characteristics are never regarded during the process of artificial breeding in hatcheries, the results indicate a basis for divergence between hatchery and wild populations. (c) 2007 The Authors Journal compilation (c) 2007 The Fisheries Society of the British Isles.