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Editor’s summary

Assessment of the status of fisheries stocks is a key component of their management. Although there has been much debate around how to do fishery assessments, there has been a general belief that estimates are roughly accurate. Edgar et al. used publicly available data on 230 of the best-known fisheries species to test whether stock biomass estimates made in the year of the estimate were as accurate as specifically calculated hindcast models (see the Perspective by Froese and Pauly). They found that, especially in overfished species, historical estimates were higher than later estimates, indicating the presence of excessively positive assessments of stock status. —Sacha Vignieri

Abstract

Effective fisheries management requires accurate estimates of stock biomass and trends; yet, assumptions in stock assessment models generate high levels of uncertainty and error. For 230 fisheries worldwide, we contrasted stock biomass estimates at the time of assessment with updated hindcast estimates modeled for the same year in later assessments to evaluate systematic over- or underestimation. For stocks that were overfished, low value, or located in regions with rising temperatures, historical biomass estimates were generally overstated compared with updated assessments. Moreover, rising trends reported for overfished stocks were often inaccurate. With consideration of bias identified retrospectively, 85% more stocks than currently recognized have likely collapsed below 10% of maximum historical biomass. The high uncertainty and bias in modeled stock estimates warrants much greater precaution by managers.