Developing integrated assessments for Dissostichus eleginoides based on the CCAMLR precautionary approach

This paper describes a possible method for implementing the precautionary approach in assessments of Dissostichus stocks when a number of different datasets are being integrated for estimating current biomass and age structure. Consideration is given to its application to the assessment of Dissostichus eleginoides in Division 58.5.2. CASAL and GYM are key elements in the implementation described in this paper but the methodology is laid out in such a way that alternative software solutions could be used in either or both of their places. The framework for this procedure has four main components. The first is the integrated assessment, undertaken external to the GYM by software such as CASAL. The second step is the sampling of the “current state” and associated parameters to provide inputs to the GYM. The third step is to use the GYM to undertake a number of projection trials, determining the median pre-exploitation spawning biomass and future states of the stock under the nominated harvest strategy. The fourth step is to test the performance of the harvest strategy against the decision rules. A controller is proposed to be used to manage the entire process including calling the CASAL or other software, the GYM and for evaluating the harvest strategy. The structure of this approach will help explore the value of integrating the datasets for Dissostichus elegionoides assessments such as are available for Division 58.5.2, which include recruitment surveys, commercial catch data from trawl and longline activities (biomass, length composition and age), and mark-recapture data. This method is an extension of current practice, although the framework is newly described and better coordinates the integration of the different steps in the precautionary approach used by WG-FSA. It is recommended that this approach be implemented for use by WG-FSA at its next meeting.