How does species association affect mixed stock fisheries management? A comparative analysis of the effect of marine protected areas, discard bans, and individual fishing quotas

We developed a spatially explicit bioeconomic model of a mixed-stock fishery with an unproductive and a productive stock to examine how the spatial overlap between species affects the outcome of a fishery under alternative management methods. We considered a competitive total allowable catch (TAC) system, with and without a ban on discards, and an individual vessel quota (IVQ) fishery managed either to maximum sustainable yield (MSY) or maximum economic yield (MEY). We also evaluated the utility of marine protected areas (MPAs) designed to protect the unproductive species for each management scenario. Banning discarding (whether under a TAC or IVQ) created the biggest increase in profit regardless of species overlap as it moves the target species biomass toward Bmey. MPAs reduced the profit in most cases and were not always successful at conserving the unproductive stock above a target size. The IVQ system managed to MEY produced the most profit among all scenarios while preserving the populations above some target values in most cases, but an IVQ system managed to MSY produced lower profits than a competitive TAC with a discard ban at some levels of species overlap.