Evaluating an empirical harvest control rule for the Torres Strait Panulirus ornatus tropical rock lobster fishery

Abstract

The Torres Strait tropical rock lobster, Panulirus ornatus (Fabricius, 1798), fishery is a culturally and economically important fishery. The Australian Commonwealth has an obligation under the Torres Strait Treaty to protect the traditional way of life and livelihood of Traditional Inhabitants, as well as promote employment opportunities for them. Management of the fishery is complicated by the high natural recruitment variability, and diving surveys have been used for the past 28 yrs to monitor changes in the size of the recruiting population. Here, we describe development of an empirical harvest control rule (eHCR) to achieve defined biological, economic and sociocultural objectives for the lobster fishery. A key principle is that fishery managers, fishers, and key stakeholders utilize pre–agreed upon and pretested rules to adjust management recommendations given updates of data. The performance of eHCR alternative candidates is evaluated using four alternative operating models, with 200 stochastic replicates each and 800 total simulations, accounting for observation error and implementation uncertainty. The eHCR adjusts recommended biological catches relative to a recent average, based predominantly on the logarithm of the slopes of recent trends in the preseason recruiting lobster, with lower weighting accorded to trends in recently-settled lobster and catch per unit effort (CPUE) from two fishing sectors. In addition, a maximum catch limit of 1000 t is set. The eHCR formula thus uses recent trends in survey and CPUE information to implement rapid, but precautionary, short- term adjustments needed to effectively manage a highly variable fishery.