Accounting for enforcement is essential to improve the spatial allocation of marine restricted-use zoning systems.
Abstract
Growing industrial and consumer demands are negatively affecting fish stocks, which are increasingly extracted above sustainable levels. Successful management of marine resources through restricted use zoning systems such as reserves and territorial user rights schemes relies on support from marine stakeholders; particularly coastal fishing communities. Restricted use zoning results in both management costs and benefits to stakeholders. To increase support for management decisions these need to be taken into account when designing optimal marine management. A linear spatial optimisation model was developed to identify zoning solutions which maximize fishers' revenue, while meeting conservation targets. Targets were based on maximum population abundance levels for two invertebrate and three reef fish species in Chile. Revenue was maximised by allocating the study area to different management zones: no-take, territorial user rights for fishing (TURFs), or open access. Costs are incurred to enforce no-take and TURF areas; but enforcement results in higher species abundance by preventing poaching and overfishing. Several scenarios were analysed to determine the impact of enforcement on revenue. Results demonstrated net benefits from enforcement: revenue under scenarios with enforcement was approximately 50% higher than under scenarios without it; and enforced-TURF areas were preferentially selected over other zones. Enforcement costs are one of the chief reasons that fishers in the study area stop actively managing TURFS. However, our analysis demonstrates that the often hidden benefits of enforcement far exceed the visible costs. These findings highlight the importance of accounting for both the benefits and costs of management in marine spatial design; particularly as they relate to marine stakeholders.