Eco-evolutionary consequences of selective exploitation on metapopulations illustrated with Atlantic salmon

Abstract

While the eco-evolutionary consequences of dispersal and exploitation are increasingly recognized, consideration of these effects and how they interact for management and conservation remains limited. We addressed this gap by examining population exploitation within a metapopulation framework, using Atlantic salmon as a case study. We compared eco-evolutionary consequences of alternative exploitation strategies by incorporating selective exploitation based on life history traits and spatial dimension of exploitation (i.e., whether populations were net exporter or importer of individuals). We used a demo-genetic agent-based model to examine demographic and evolutionary consequences of these strategies across a gradient of population-specific exploitation rates. At the metapopulation scale, we found both lower abundance and earlier sexual maturation with increasing exploitation, particularly when fishing was selective on larger individuals. The spatial selectivity of exploitation had an overall additional detrimental effect on metapopulation performance and fisheries yield, and induced stronger evolutionary changes than when exploitation was evenly spread over all populations. We discuss the implications of metapopulation functioning for species management and how considering dispersal patterns and intensity might change how we apply harvest. Nevertheless, our findings suggest that the safest approach remains to distribute exploitation efforts evenly across all populations, especially in the absence of variation in intrinsic productivity and with the dispersal rates and spatial configuration simulated. However, this strategy might not completely prevent negative consequences at the local scale. Therefore, we advise managers to critically assess the relevance of our results and dispersal assumptions in the specific cases they may have to deal with.