Common patterns, common drivers: comparative analysis of aggregate surplus production across ecosystems

Marine ecosystems are dynamic, often have open boundaries, and their overall productivity responds nonlinearly to multiple drivers acting at multiple temporal and spatial scales, under a triad of influences: climatic, anthropogenic, and ecological. In order to further our understanding of how the structure and functioning of marine ecosystems influence and regulate patterns of fisheries production, and how they are affected by this triad of drivers, a comparative approach is required. We apply a system-level surplus production modeling approach to the total aggregated catch and biomass of all major targeted fish species in 12 exploited Northern Hemisphere ecosystems. We use 2 variations of a surplus production model: a regression model and a dynamic model, each fit with and without environmental and biological covariates. Our aims were to explore (1) the effects of common drivers at the basin scale and their relative influence within the triad of drivers among systems, (2) the impact of covariates on biological reference points and implications for fisheries management, and (3) the relationship between maximum sustainable yield (MSY) and production. Our results show that the environment affects estimates of system-level MSY across all ecosystems studied and that specifically water temperature is a major influence on productivity. Emergent properties of northern hemisphere systems suggest that MSY values and optimal exploitation rates are relatively consistent: MSY ranges between 1 and 5 t km(-2) and optimal exploitation rate between 0.1 and 0.4 yr(-1). Finally, we suggest that the relationship between fisheries yield and primary production is not as simple as suggested in other studies. These results put fisheries in a broader ecosystem context and have implications for an ecosystem approach to management.