A multispecies catch-ratio estimator of relative stock depletion

Abstract

Abstract A simple approach is described that uses the ratio of catches among a reference and a target stock to estimate their relative depletion. The catch-ratio estimator was simulation tested to identify conditions under which it can be expected to provide precise and unbiased estimates of relative depletion. The catch-ratio estimator is strongly affected by diverging catch reporting rate and catchability among reference and target stocks. Outside of these issues, the approach is unbiased for a range of life-history characteristics, temporal patterns in exploitation rate and changes in the age vulnerability to fishing. Coupled with the depletion estimates of a data-rich stock, the catch ratio estimator can be used to infer depletion of a data-limited stock without an assessment.