A voluntary reduction in the commercial catch of rock lobster (Jasus edwardsii) in a New Zealand fishery

Abstract

We describe the development and application of a management procedure (decision rule) that resulted in a voluntary reduction in the commercial catch of spiny rock lobster (Jasus edwardsii) in the lower east coast of North Island of New Zealand. The management procedure was developed from an accepted assessment of the CRA 4 (Wellington-Hawke's Bay) fishery, which used an integrated length-based assessment model fitted to commercial fishery catch-per-unit-effort (CPUE) biomass indices, commercial length-frequency data, and tag-recapture data. The assessment model had been Bayesian, and used the joint posterior distribution of parameters to predict the effect of 384 alternative harvest control rules on the future size of the CRA 4 stock. The harvest control rules all used CPUE as their input, and generated annual changes in catch, which were then simulated by the population dynamics of the operating model. Uncertainty was added to evaluations through observation error, added to the simulated CPUE observations, and stochastic serial auto-correlation variation in recruitment. We describe how this management procedure was used to effect a voluntary reduction in catch to address the problem of a rapidly declining population.