ICES provides independent advice on sustainable fishing opportunities using the maximum sustainable yield (MSY) approach, which maximizes the average long-term yield of a given stock while maintaining productive fish stocks within healthy marine ecosystems. The majority of the advice is based on single stock assessments and management goals. However, demersal stocks are typically caught in hauls comprised of multiple species. As a result, achieving single species maximum sustainable yield in a naturally heterogeneous mixed demersal fisheries is challenging, as the objectives for different stocks may not align.
The Working Group on Mixed Fisheries (WGMIXFISH) addresses this sustainability challenge annually through the production of mixed fisheries advice for a number quota managed stocks across three ecoregions: Iberian waters, North Sea, and Celtic Seas. This mixed fisheries advice is a step towards ecosystem based fisheries management as it accounts for the true heterogeneity of stocks in demersal fisheries, as well as trends in fishing effort, fisher behaviour and vessel power. Mixed fisheries advice highlights the potential implications of single stock management on the catches of multiple stocks caught together in mixed fisheries. This advice is produced using the past fishing patterns and catchability of the different fleets, as well as the single species advice, to provide quantitative forecast of over- and under- exploitation of the different stocks given mixed fishery interactions.
WGMIXFISH provides additional qualitative summaries of historical trends in catch compositions, effort and catchability, of gears and fleets which provide essential insight into the complex interactions and interdependencies of different stocks, fleets and member states operating within these dynamic demersal fisheries. The combination of mixed fisheries forecasts and these informative historical trends provide managers with the tools required to define safe and sustainable thresholds for economic operations within these ecoregions.
WGMIXFISH continue to develop and expand the toolbox of methods and data used to summaries these complex demersal mixed fisheries interactions and to address the growing complexity of fisheries management within Europe (i.e. zero quota species, landing obligation).
Unlike single stock advice, there is no single recommendation, so these scenarios assume the roles of conceivable catch options. Since it isn't possible to achieve all management objectives simultaneously, this method aims at presenting sets of trade-offs for whatever choices are made at sea. Photo: Jonathan White.