Thirty-five experimental fisheries reveal the mechanisms of selection

Fisheries have been described as large-scale evolutionary experiments; yet such experiments tend to be poorly replicated and therefore lack the predictive power essential for designing appropriate management strategies to minimize the effects of fisheries-induced selection. Large-scale removal of non-native trout from 35 montane lakes in California provided repeated experimental fisheries that allowed us to explore how environmental parameters affect the three potential contributors to overall selection: the fitness-trait correlation, trait variability, and fitness variability. Our results demonstrate that fishing rapidly altered the size structure of harvested populations, and that the magnitude of change was primarily driven by the fitness-trait correlation (net selectivity). Fishing-induced selection was repeatable overall but was also influenced by environmental (lake size and quality) and demographic (size structure) parameters. Decomposing fishing-induced selection into its key components can improve the management of stocks experiencing fishing-induced selection by identifying the drivers of selection and therefore the appropriate target for management.