Abstract

Captive rearing may elicit environmental or genetically-based changes to salmonid antipredator behaviour, which may reduce its survival when released into the wild. While this subject has received considerable attention, there has been little research using fish reared for a short period of time (2 generations or less of captive breeding). In addition, few studies have tested wild-caught and hatchery-reared fish originating from the same population and none have done so under natural conditions. Hence, I conducted a semi-natural field study comparing the antipredator behaviour of wild-caught, F1 (offspring of wild-caught adults) with that of F2 (second generation) hatchery-reared juvenile Atlantic salmon (from the same source population) to standardized predation cues. Wild-caught salmon exhibited strong antipredator responses to the predation threat, while F1 and F2 salmon showed weaker responses. Interestingly, F1 salmon showed stronger responses than F2 salmon. The observation that wild-caught and F2 salmon were consistently different supports the hypothesis that even one full generation of hatchery rearing may be sufficient to select for maladaptive responses to predators under natural conditions. The observation that F1 salmon were intermediate to wild-caught and F2 salmon suggests that individual experience may also play a significant role on the observed reduced antipredator response. Given the current decline of many salmonid populations across North America and the controversy regarding the effectiveness of hatchery programs for conservation use, the results of this study suggest that minimizing hatchery time may reduce the behavioural differences between wild and hatchery-reared fishes.