Is B1 = K an appropriate assumption when applying an observation error production-model estimator to catch-effort data?

Abstract

A Monte-Carlo simulation approach is used to investigate the relative robustness of the results of the Butterworth–Andrew (B1 = K and B1 estimated) dynamic production-model observation-error estimators to different “true” values of the ratio of initial biomass B1 to unexploited equilibrium biomass K. The simulations use an underlying operating model typical of that appropriate for stocks of Cape hake off southern Africa. The B1 = K variant of the estimator results in lower estimated expected discrepancies for a number of management quantities over a wide range of the value of the “true” ratio. In addition, it is less likely to provide severe overestimates of the f0.1 total allowable catch (TAC). Not all management quantities are equally sensitive to the value of the “true” ratio. In particular, f0.1) TACs can be severely overestimated, although the maximum sustainable yield (MSY) is relatively well determined over a wide range of values of the ratio. It is therefore recommended that harvesting strategies which do not permit TACs to be set in excess of the estimated MSY be preferred. © 1990 Taylor and Francis Group, LLC.