Mediterranean brown trout catch-and-release recreational fisheries might not be sustainable under concurrent climate warming and hydrological change

Abstract

Climate change is reducing the harvestable surplus that supports recreational fisheries, which, in turn, is affecting the resilience of exploited populations to the demographic and eco-evolutionary impacts of climatic changes. Consequently, total catch-and-release (C&R) fishing is a growing conservation strategy implemented to ensure the self-sustainability of exploited populations. We used an eco-genetic individual-based model to (1) assess the demographic and phenotypic effects of C&R regulations on exploited brown trout populations across a range of scenarios involving different combinations of fishing pressure and post-release mortality under two environmental scenarios (warming vs. concurrent warming and flow reduction); and (2) determine the regulations leading to recruitment overfishing under each environmental scenario. Our simulations suggest that in the absence of flow reductions, population compensatory mechanisms would make C&R fishing sustainable unless fishing pressure and post-release mortality rate were too extreme. However, exploited populations would be dominated by smaller and younger individuals, which could affect the social sustainability of the fishery. Our study also suggests that if substantial warming and flow reduction concur, the decrease in total population fecundity caused by environmental changes is so strong that even low fishing pressure and post-release mortality would lead to recruitment overfishing, increasing the risk of population collapse.