Buffers for Scientific Uncertainty in Stock Assessments—How Big Should They Be

To account for scientific uncertainty and bias in stock assessment models, fisheries managers often include precautionary buffers in their allowed catch estimates to reduce the risk of overfishing. It is unclear however just how large—or small—these buffers should be. Finding a minimum buffer size could be useful for both managers and fishers, allowing for greater certainty in management decisions and potentially more allowable catch.

In this study, researchers compared estimates among different assessments of the same stock using Bayesian hierarchical models.  The goal was to quantify the variation among stock assessments of marine fishes and invertebrates in assessment outputs used to determine allowable biological catch such as terminal year biomass, reference points, and overfishing limits. Among assessments of the same stock, researchers found region-specific variations in estimates of biomass, fishing mortality, reference points, relative biomass, and fishing mortality rate, and overfishing limits; there was little evidence of inter-assessment bias. These results quantify one aspect of uncertainty in assessments, which in turn provides a base for determining a minimum buffer for scientific uncertainty. In future work, researchers will use this information to assess how climatic, environmental, ecological, and assessment-related factors impact stock assessment performance.

Read the full paper here.

Reference

Bi, R., Collier, C.; Mann, R., Mills, K.E., Saba, V., Wiedenmann, J., Jensen, O.P. (2022) How consistent is the advice from stock assessments? Empirical estimates of inter-assessment bias and uncertainty for marine fish and invertebrate stocks. Fish and Fisheries. https://doi.org/10.1111/faf.12714