What Are We Protecting? the Challanges of Marine Protected Areas for Multispecies Fisheries

In the quest to limit the bycatch of non-target species, fisheries managers have wielded a range of policy tools.  One instrument that has achieved substantial use is marine protected areas (MPAs) to protect vulnerable aggregations of bycatch species.  MPAs are often popular with ecologists and fishery managers because of their relative ease of administration, the potential for multiple benefits due to protection of habitat from damage, and the widespread acceptance of MPAs as an instrument of choice for “ecosystem-based management” of fisheries.  Despite these merits, we argue that MPAs may have significant limitations that should figure in their adoption.  First, closures can displace fishermen from favored fishing grounds, potentially reducing the productivity of fishing effort and increasing the variable costs of fishing.  Second, by reducing fishermen’s spatial choice set, closures can create significant spillovers for the management of other species.  For instance, a closure intended to protect one vulnerable species may increase fishing pressure on another. 

To provide empirical context for our criticisms, we examine the closure of grounds in the Bering Sea flatfish trawl fishery for the protection of red king crab.  We utilize the availability of detailed spatial data on fishing effort and catch before and after the closure to estimate zero-inflated negative binomial models of king crab and halibut bycatch.  We demonstrate that, while the MPAs were effective in reducing crab bycatch, they also displaced fishermen to grounds with increased density of an alternative bycatch species – halibut.  By utilizing novel simulation techniques from the pre and post-closure data, we demonstrate how the spatial “corner solution” presented by the MPAs is not cost effective and how a policy that allows fishing over the entire grounds while providing a disincentive for both crab and halibut bycatch (as in a multispecies individual quota system) can achieve the multispecies bycatch conservation targets adopted by managers while increasing fishery profits.