A voluntary harvest control rule for a New Zealand rock lobster (Jasus edwardsii) stock

Abstract

This paper describes a study to develop and test a simple harvest control (decision) rule that could be used by the commercial rock lobster industry in the CRA 5 quota management area in New Zealand. Time contraints prevented a full stock assessment, so alternatively the history of annual production was estimated from catch and catch‐per‐unit‐of‐effort (CPUE) data, and two versions of an operating model were based on the results: one used a fitted relation between biomass and production, and the other used constant production. Production was simulated with autocorrelated stochastic variation, and CPUE was simulated with observation error. Using a base case and two sensitivity trials for each model gave six operating models. Six candidate harvest control rules were developed, and sets of 1000 simulations were made for each combination of rule and model. The rules were then compared on the basis of fishery and stock indicators. Although choosing a specific rule is difficult, having a voluntary harvest control rule that reduces catches when CPUE is low maintains a higher mean biomass and prevents low biomass episodes.