Explorative behavior increases vulnerability to angling in hatchery-reared brown trout (Salmo trutta)

Animals, including fish, display individually consistent behavioral differences that may affect an individual's vulnerability not only to predation, but also to fishing. Compared with complex natural environments, plain hatchery environments might induce development of behaviors that increase vulnerability to fishing, which would in turn have major implications for the management of stocks by supportive releases. We studied whether the vulnerability of hatchery-reared brown trout (Salmo trutta) to angling could be predicted by rearing method (standard versus enriched) or behavioral variation that was assessed using long-term observations of moving activity in groups. High moving activity in the beginning of the behavioral tests (i.e., exploration behavior) predicted increased vulnerability to angling independently of fish body size. Standard rearing promoted high exploration rate among fish, whereas enriched rearing promoted improvement in body condition in (semi-) natural conditions. However, the driving influence of hunger on vulnerability could not be ruled out, as the most explorative standard-reared fish appeared unable to maintain their body condition during the experiments. This study provides direct evidence that standard hatchery rearing method promotes behaviors that directly predict vulnerability to angling.