Development of a spatially-structured model for stock assessment and TAC decision analysis for Australian abalone fisheries
Together, the state-managed abalone fisheries comprise one of Australia's most valuable fisheries worth over $125 million dollars per year. Whilst there are obvious differences among the fisheries in each state, all are managed in a very similar way with perhaps the most important restriction being the total catch removed each year by the commercial fishery (TACC). Historically, the TACC in many of the states has been changed in response to management or industry perceptions, with little attempt to incorporate the available biological information into the decision-making process. This has been in part caused by the lack of a sensible framework with which to condense the available biological information into advice concerning the likely risk and performance of different future TACC. In recent years, independent research in Victoria and New South Wales has started to formalise a very similar framework for TACC advice. Whist specific differences occur among the approaches in the two states, several fundamental similarities occur. These include the development of a length-structured, stochastic population model that can incorporate all available biological information and make forecasts of the likely effects of future TACC. Several aspects of the biology and ecology of abalone complicate the assessment of their fisheries. Perhaps most importantly, the short-distance dispersal of larval abalone leads to dis-aggregated populations with a limited ability to re-populate depleted areas. Further, the ability of commercial divers to differentially exploit spatially-separated sub-populations allows them to maintain catch rates despite reduced stock abundance. To date, such spatial structure has not been incorporated in any framework used for TACC advice. This is despite the availability of spatially-structured programs monitoring changes in the abundance of abalone of different sizes that have been completed within Victoria, South Australia and New South Wales for several years and are proposed in the other states. Such programs provide the necessary information with which to make spatially-structured assessments of the likely risk and performance of different future TACC.
1. Develop an appropriate modelling framework to incorporate all relevant biological information into a spatially-structured assessment of the likely risk and performance of different future TACC for an abalone fishery.
2. Develop the necessary software to complete such an assessment, and modify it to incorporate differences among the states and species.
3. Evaluate the capabilities of the modelling framework.
4. Compile the necessary data and complete a preliminary assessment of each state's abalone fishery.
Principal Investigator: H. Gorfine, B. Taylor, M. Cleland, M. Haddon, A. Punt, D. Worthington & I. Montgomery