Marine reserve design and the evolution of size at maturation in harvested fish

By significantly changing size-dependent mortality, fisheries can cause rapid evolution toward earlier maturation in harvested species. Because earlier maturation negatively affects biomass yield and sustainability, ignoring evolutionary changes could significantly reduce the success of fisheries management policy. With a quantitative genetic model of size at maturation that incorporates phenotype plasticity, we examine the impact of different management strategies including traditional effort control and Marine Protected Areas (MPAs). After verifying the model's accuracy, using historical trajectories for size at maturation in cod (Gadus morhua), we test model predictions under different management schemes with life history parameters for red snapper (Lutjanus campechanus) and two rockfish species (Sebastes paucispinis and S. ruberrimus). The model results show that no-take MPAs can protect against strong fisheries-based selection for earlier maturation. The potential to protect against anthropogenic selection declines with increasing fragmentation of reserves to networks of small reserves. Accounting for the evolution of size at maturation increases the predicted biomass contribution from MPA populations to harvested populations. Traditional management approaches, such as adjustments to harvest rate and maximum size limits, can lead to equivalent protection against anthropogenic selection and equivalent or greater long-term biomass yield than establishing MPAs; however, the protection and yield from establishing no-take MPAs appears more robust to uncertainty.