Behavioural effects in juvenile brown trout in response to parental angling selection

Abstract

Fishing that selectively captures and removes fish based on their behavioural decisions is predicted to induce evolution towards timid fish stocks. Thus, offspring behaviour should associate with parental vulnerability to angling. We examined phenotypic behavioural variation in juvenile brown trout (Salmo trutta) whose parents, representing a hatchery and a wild stock, were experimentally grouped based on their relative vulnerability to angling. The F1 offspring from highly vulnerable (HV) and low vulnerable (LV) parents were reared in common garden conditions together with a crossbred wild × hatchery reference group and tested for boldness during their first summer. Wild LV juveniles were the shyest of all fish, but not distinctly shyer than wild HV juveniles. Contradictorily, hatchery LV juveniles expressed bolder behaviour than hatchery HV juveniles. We show that angling selection may have transgenerational behavioural effects independently of size variation, but changes in behaviour can manifest differently in fish from different backgrounds. Our results partly support the earlier findings of increased angling-induced timidity in wild populations and thus call for management focus on behavioural effects of fishing.