Justification for retention of the catch-and-release in the wild brown trout Salmo cf. trutta fishery

Abstract

Total catch-and-release (C&R) is a regulatory measure implemented for maintaining the self-sustainability of stocks encountering strong fishing pressure. The River Đetinja is a tailwater with very strong fishing pressure, managed for more than a decade by C&R. That fishing regime was questioned by a new fishery manager, without the justification provided. The only available data for examining the brown trout growth were those from catches of two fly fishermen over five consecutive years. Only in one year did the average catch of one fisherman slightly surpass the legal limit for taking brown trout, and in none of years was the average size of pooled catches close to it. Survival data were similar, suggesting the stability of the brown trout stock through the period of investigation. Asymptotic length L∞ gradually increased and coincided with the growth speed ϕ and maximal yield length Lopt values. In spite of that, the high fishing pressure and low proportion of brown trout above both the legal taking limit of ≥25 cm SL and Lopt values in catches strongly support the retention of C&R as a regulatory measure on the River Đetinja.