Post-release exploration and diel activity of hatchery, wild, and hybrid strain brown trout in semi-natural streams

Behaviour that is adaptive in captivity may be maladaptive in the wild and compromise postrelease survival of hatchery fish. The understanding of behavioural variation displayed immediately after release could help to improve hatchery protocols and development of behavioural tests for assessing the fitness of fish reared for releases. We characterized the postrelease behaviour of common-garden-raised offspring of wild resident, captive-bred migratory, and hybrid brown trout (Salmo trutta) in two experiments: in small artificial channels and in high and low densities in seminatural streams. The results from seminatural streams showed that hatchery fish were more likely to disperse downstream from the initial stocking site compared with hybrid and wild strain fish. The small-scale experiment did not reveal this ecologically pivotal difference in postrelease performance among strains, and individual responses were inconsistent between the experiments. Circadian activity patterns did not differ among strains. These detailed observations of postrelease behaviour reveal important intrinsic differences in dispersal traits among brown trout strains and suggest that selective breeding and crossbreeding can substantially affect these traits.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author