A history and evaluation of catch-only stock assessment models

Abstract

Understanding the status of fish stocks is a critical step in ensuring the ecological and economic sustainability of marine ecosystems. However, at least half of global catch and a vast majority of global fisheries lack formal stock assessments, largely due to a lack of sufficient data. Catch data, loosely referring to any catch records be it inclusive of discards or not, are the only type of fishery data available across a wide range of fisheries at a global scale. This has given rise to a long list of so-called “catch-only” models, intended to estimate aspects of stock status based primarily on characteristics of a fishery's catch history. In this paper, we review the history, performance and potential of “catch-only” models to estimate stock biomass status. While individual catch-only models often report good performance, repeated efforts to examine the performance of these models have consistently found them to be imprecise and biased when applied to new data-limited fisheries. We demonstrate that a large reason for this is the simple lack of information on stock status contained in the shape of a catch history alone. Off-the-shelf use of catch-only models can lead to poor and biased estimates of stock status, potentially hindering efforts at effective management.