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Marine fish stocks are an important part of the world food system and are particularly important for many of the poorest people of the world. Most existing analyses suggest overfishing is increasing, and there is widespread concern that fish stocks are decreasing throughout most of the world. We assembled trends in abundance and harvest rate of stocks that are scientifically assessed, constituting half of the reported global marine fish catch. For these stocks, on average, abundance is increasing and is at proposed target levels. Compared with regions that are intensively managed, regions with less-developed fisheries management have, on average, 3-fold greater harvest rates and half the abundance as assessed stocks. Available evidence suggests that the regions without assessments of abundance have little fisheries management, and stocks are in poor shape. Increased application of area-appropriate fisheries science recommendations and management tools are still needed for sustaining fisheries in places where they are lacking.

arising from B. S. Halpern et al. Nature488, 615–620 (2012)10.1038/nature11397 How close to maximum sustainable food provision is current seafood harvest from the world’s oceans? Halpern et al. 1 suggest that the answer is 25% from a global index of food provision, part of their multifaceted index of ocean health. Rigorous methods used for management, however, demonstrate that their food provision index is uncorrelated with actual food provision, and that global ocean food provision is in the range of 71–95%. Their results stem from an uncertain method of estimating maximum sustainable yield (MSY), and we believe that this approach should be avoided as a measure of food provision. There is a Reply to this Brief Communication Arising by Halpern, B. S. et al . Nature 495, http://dx.doi.org/10.1038/nature11975 (2013).

Requirements for a fishery to achieve Marine Stewardship Council (MSC) certification include demonstrating that targeted populations (‘MSC stocks’) are fished at sustainable levels. The credibility of this claim can be evaluated by comparing estimated abundance of MSC stocks to benchmarks based on sustainability criteria. Additionally, to evaluate whether MSC certification provides a meaningful distinction, the sustainability status of MSC stocks can be compared with that of populations without a linked certificate (‘non-MSC stocks’). It is expected that MSC stocks are more likely to be maintained at levels of high abundance relative to sustainability benchmarks compared to non-MSC stocks. Similarly, it is expected that MSC stocks are less likely to become overfished, and if they do become overfished, that fisheries are incentivised to aid in their rebuilding to avoid suspension of certification. We compare published biomass estimates relative to biological reference points between MSC stocks and non-MSC stocks of wild-caught marine fish and invertebrate species around the world. These are observational data, and though we control for the propensity of certification, certification is not independent of relative biomass and therefore we describe associations rather than causal influences. Individual stocks from both groups were highly variable in relative biomass trends over the past two decades, with substantial overlap in the distributions of MSC and non-MSC stocks. In recent years (2014-2018), MSC stocks had, on average, greater biomass relative to biomass at maximum sustainable yield ( B MSY ) than non-MSC stocks. MSC stocks were also less frequently overfished compared to non-MSC stocks, with estimated biomass below a limit reference point ( B lim ) for 9% of MSC stocks and for 26-33% of non-MSC stocks. Eight MSC stocks currently or previously certified and defined as overfished in 2017 or 2018 had previously entered the program based on scientific advice available at the time indicating they were fished within sustainable limits. Subsequently, when revised stock assessments estimated the biomass to be lower than previously thought, fisheries for those stocks were suspended from certification. Together, these results suggest that eco-certification is associated with a credible claim on sustainable stock status and provides a useful distinction from other seafood. Further, our results show how the rare exceptions to this pattern may arise from retrospective changes in scientific advice.

Re-sampling fisheries from FAO ranges for overexploited fisheries, fully exploited fisheries and underexploited fisheries3 and estimating food provision using the Pella-Tomlinson model yields a mean food provision index of 82% (95% CI, 81-84%). [...]food provision from oceanic fisheries is consistently estimated to be in the range of 71-95% by a wide variety of methods, which is far from the 25% estimated by Halpern et al.1. [...]Halpern et al.1 believe that it must be possible to extract MSY and food provision estimates from a simple function of current catch and maximum catch.