Evaluating bioeconomic tradeoffs of fishing reserves via spatial optimization

Abstract

No-take marine reserves are common strategies used in spatial fisheries management. There are at least four general objectives for marine reserve design: (1) maximizing conservation, (2) minimizing total reserve area, (3) maximizing reserve compactness, and (4) minimizing socioeconomic opportunity cost (e.g., fisheries revenue). A spatial optimization model was developed to solve for reserve placements under those four objectives, while evaluating the bioeconomic tradeoffs and potential gaps of a subset of bottomfish restricted fishing areas (BRFAs) for the Hawaiian bottomfish fishery. Optimized reserve placements with minimal opportunity costs had little overlap (< 9%) with the placements of the BRFAs, opportunity cost values 50–83% less than that of the BRFAs with 40–54% higher potential conservation value. When reserve placements were optimized to provide a maximal opportunity cost, solutions had up to 49% overlap with the BRFAs, highlighting a potential drawback of the BRFA system with respect to socioeconomic impacts. When opportunity cost was instead calculated as total area, the optimized placements also had considerable overlap (up to 42%) with the BRFAs, highlighting the importance of socioeconomic data to the reserve design process. The solutions that provided maximal reserve compactness may be the most pragmatic for a reserve design team with specific area and/or conservation targets, as these solutions produced compact reserve placements that best matched those targets at a minimal opportunity cost. This analysis emphasized the use of spatial optimization models to not only guide the reserve design process, but to highlight tradeoffs of conflicting fisheries objectives in reserve design.