Considerations on the design and evaluation of surveys for estimating recruitment of Patagonian toothfish (Dissostichus eleginoides) with preliminary outcomes for the Heard Island plateau region (Division 58.5.2)

Assessments of long-term sustainable yield using the Generalised Yield Model and the setting of total allowable catches (TAC) for Patagonian Toothfish, Dissostichus eleginoides, for the Heard Island Plateau region (Division 58.5.2) are based on data obtained from annual random stratified trawl surveys (RSTS) and from targeted commercial fishing operations via an observer program. The current RSTS design for Division 58.5.2 is reviewed and estimates of optimal distribution of trawl stations among strata provided for estimates of abundance of individual pre-recruitment age classes and total abundance for a range of levels of confidence. The results indicate that while the current and previous survey stratifications appear appropriate, the current levels of survey effort are not sufficient to provide reasonable levels of confidence in the estimates of abundance for all but the youngest year class. It is recommended that the implications of these results need to be examined as part of a full evaluation of the current management procedure for D.eleginoides in Division 58.5.2 in order to determine the potential implications for meeting long-term yield and conservation objectives. An approach to progressing such evaluations in the context of the elements of the current monitoring and assessment methods is outlined.