There is potential for significant growth of blue crab fisheries in South Australia and other crab-producing states driven by demand of export markets. However, the industry and resource managers lack reliable information on the productivity and likely sustainable harvests of blue crabs. Since June 1996, the blue crab fishery has been managed under both output (catch quotas) and input (pot limits) controls. A lack of biological information and concern about the uncertainty of the stock's capacity to withstand increased fishing effort have prompted a precautionary approach to management. Information on the fisheries biology of blue crabs is necessary to augment the fisheries dependent information collected in South Australia. Such information will promote bolder, more entrepreneurial management strategies with concomitant opportunities for increased economic wealth and industry development.

After presenting a full research report proposal for blue crab in 1995, the South Australian Research and Development Board recommended that additional supportive research program necessary for the management of this fishery would augment basic research funded by the blue crab fishing industry. Under these circumstances, the basic research program was tailored to provide the information urgently needed to initiate management processes. The basic research program started in July 1996. The proposed research will complement this basic program and research in other states consistent with the national strategy (Kumar 1997b).

This proposal addresses a need for cost-effective assembly of research information. The applicants recognise that the current landed value of blue crabs in Australia is not large enough to support a resource intensive program and seek to augment current research conducted in South Australia and in other states by proceeding with a collaborative program of research aimed at gaining biological information relevant to the assessment of blue crab stocks. The research will concentrate on determining the key biological parameters influences recruitment, growth, movement, and survival and identify the main sources of variation in those parameters. Finally, an important outcome will be the development of a spatially explicit production model that will allow managers to confidently evaluate the consequences of alternative management strategies.

Management of the ETBF is complex because of the cross-jurisdictional nature of the stocks and governance through the Commonwealth Harvest Strategy Policy and the WCPFC. Current assessments conducted by the WCPFC assume that these species comprise either single discrete stock units throughout the WCPFC area or across the Southern Hemisphere portion of the region and genetic methods used in the past have been unable to refute such assumptions. Biological information on growth rates and reproduction, movement data derived from tagging studies and spatial and temporal variability in catches of these species however, suggest that there is likely to be some structure to stocks throughout the WCPFC region and assumptions of single spawning populations may not be accurate.

More recently, traditional and next generation genomic methods have provided evidence of population structure in yellowfin tuna across the Pacific (e.g. Aguilar et al. 2015; Grewe et al. 2015) and provide some support to the hypothesis that yellowfin tuna fished by Australia’s tuna fisheries may be a localised stock within the Coral and Tasman Sea region. If yellowfin tuna and if any of the other principal species occurring in the ETBF do comprise localised stocks, this has obvious implications for the management both within national and regional contexts. Clarification of the connectivity and population structure of species in Australia’s Tropical Tuna fisheries with the broader WCPFC region is required for appropriate governance through the Commonwealth Harvest Strategy Policy and the WCPFC, to ensure any risks to regional stock biomass are minimised and to improve stakeholder concern over stock management.