Assessing spillover from marine protected areas to adjacent fisheries : Baltic and North Seas, Atlantic EU Western Waters and Outermost Regions : final report

Marine protected areas (MPAs) are widely recognized as an important tool for biodiversity conservation and fisheries management. Despite empirical evidence that abundance and biomass of fished species increase within MPA boundaries, the potential for MPAs to provide fisheries benefits to adjacent waters remains debated. This study documents the first systematic review of empirical evidence for spillover from MPAs in the European Union and other temperate regions. Findings show that scientific evidence of ecological and fishery spillover is relatively sparse. The combination of MPA characteristics (its age, local context and whether it is part of a network) proved capable of predicting the occurrence of spillover and therefore these are key considerations for the design of MPAs. Further, this study confirms that species mobility and reproductive strategies are important traits in explaining occurrence of spillover. There is a wide range of methodological approaches (sampling design, methods, statistical analyses) used in the literature to investigate spillover. Ideally, assessment should be based on a Before After Control Impact design, with a distance gradient sampling scheme integrated over time. A combination of studies, using biological sampling and tagging, gives a more complete picture of potential spillover effects. Using the literature available and study quantitative analyses, a conceptual model tool was developed to estimate the likelihood of spillover for existing and proposed MPAs. The tool integrates the potential social, ecological and economic factors that may lead to MPA spillover. Finally, qualitative and quantitative approaches were used to evaluate ecological and/or fishery spillover effects for 15 case studies from across Europe. The case studies demonstrate that MPAs can lead to increased species spillover, but these patterns are species-specific, and spillover effects will take a relatively long time period to be relevant for fisheries. Overall, this work highlights elements that could guide strategies to enhance local fishery management using MPAs. Further research should focus on documenting the scale and magnitude of spillover, quantifying the dynamics of spillover and fisheries around MPA borders, as well as the interaction between protection time and other fishery management tools.