Evaluation of management tools for Australia's South East Fishery 2. How well can management quantities be estimated?

The ability to estimate some of the quantities relevant to the management of South East Fishery species is examined using Monte Carlo simulation. The analyses are based on scenarios for four of the species of this fishery (spotted warehou, tiger flathead, jackass morwong and pink ling). Integrated Analysis was found to perform best out of six potential methods of fisheries stock assessment (Schaefer and Fox production models, age-structured production model, Integrated Analysis, ad hoc tuned VPA and ADAPT) that are, or have been, applied to data for South East Fishery species. However, its performance, particularly for spotted warehou, is nevertheless relatively poor. The sensitivity of estimation ability to many factors including model uncertainty and the extent of observation and process error is examined. Factors that influence estimation performance markedly include: violation of the assumption of no population spatial structure; time-trends in catchability; the depletion of the resource at present; and uncertainty about the value of the instantaneous rate of natural mortality. Little improvement in estimation performance can be expected without resolution of issues related to model structure. This highlights the importance of considering model uncertainty in future studies of the estimation performance of stock assessment methods.