Are flawed MPAs any good or just a new way of making old mistakes?

The case for Marine Protected Areas (MPAs) is often supported by the observation that present fisheries management has failed. This overlooks the fact that, often, management plans are not implemented in accordance with advice and that subsequent regulations are frequently violated. Evidence is emerging that MPAs may be equally open to mismanagement, either because MPAs are smaller than recommended or through lack of compliance. Therefore, it is interesting to ask whether MPAs would also fail if they are not properly implemented or enforced. A population model was used to examine this question. The model demonstrates that biomass and yield are reduced, and can collapse under bad MPA management. When illegal, unreported, or unregulated fishing occurred within the MPA, yield and biomass declined almost linearly with increasing poaching pressure. Yield was more robust than biomass to the effects of making MPAs smaller than the optimum size for limited reductions in MPA size. Varying the degree of mobility had little impact on the response of yield and biomass. This analysis demonstrates the vulnerability of MPAs to design and governance failings, and the importance of considering enforcement during MPA design.