The rapid expansion of the Australian abalone culture industry is being underpinned by advances in research and development that have seen tank designs and formulated diets become far more cost-effective. Market prospects are excellent (Johnston, 1996) and investment capital and available sites do not seem to be limiting factors. The hatchery sector is performing very well and its capacity is expanding rapidly.

The major threat to this optimistic scenario is a decline in the health status of abalone and the most likely cause is inadequate water quality. The threat is real based on results obtained from our previous FRDC-funded, environmental requirements (bioassay) research. The 30% reduction in growth rate noted above would be enough to destroy profit margins in most aquaculture industries.

We need to determine safe levels of more of the water quality variables that threaten the health of abalone and to refine the estimates for some of the variables assessed so far; greenlip abalone have proved to be even more sensitive to ammonia and nitrite than we had expected. In some states there is more emphasis on blacklip abalone culture and we need to assess that species at least in terms of its sensitivity to the most likely stressors. We also need to develop diagnostic tools for the tissue damage that these water quality variables do when outside these safe ranges so that health workers can identify the cause of a health problem in abalone.

This project is compatible with the FRDC strategic plan as it is commercially attractive (prevents loss of profitability), it is feasible (the experimental system, methods and expertise have already been developed), it is collaborative (hosted by industry), has been given the highest priority by the Subprogram Steering Committee, it relates strongly to growth and survival within aquaculture development, and the species involved are primarily being produced for the Asia - Pacific market. Additionally, it contributes to export technology (live holding) and Ecosystem Protection by defining tolerances of a key commercial and recreational species.

Traditionally, catch per unit of effort (CPUE) is used to monitor the health of the fishery and indicate the success or otherwise of management practices. Under current input controls CPUE is based on fishers maximising their total catch. In contrast, under output controls where catch is predetermined fishers will alter their catching scenarios to maximise the return (dollars per kilogram) from their catch. In southern rock lobster fisheries there is significant potential to alter fishing patterns to maximise economic return, especially through seasonal shifts in effort. As this change occurs, the value of using CPUE data to continue monitoring the fishery will be eroded. As such, both fisheries independant means of monitoring the fishery and new monitoring methods will become increasing important.
Both exploitation rates and biomass estimates are important stock assessment parameters and biological reference points in sustainable management of fisheries resources.
This project will evaluate fishery independant means of deriving these estimates and by determining the precision of derived estimates, demonstrate their suitability as biological reference points.
In a report to the Department of Industry, Technology and Commerce titled "Oceans of Wealth?", the Review Committee on Marine Industries, Science and Technology stated in their conclusion, 'The knowledge gained from scientific research into fish stocks and the impacts of the environmental and harvesting factors is a necessary but not sufficient element in the conservation of productive fish stocks. A vital element in both scientific assessments is the availability of reliable information about exploitation levels'. This project is aimed at addressing this need for southern rock lobster.

Estimates of participation rates, catch and effort are essential for effective fisheries management. Such data are collected from the commercial fishery through logbook programs but are unavailable for the recreational sector in Tasmania. As many of the fisheries resources are believed to be either fully or over-exploited and as resource sharing and other management issues become increasingly important, so too does the need for total fishery data.

The size of the recreational catch is a major uncertainty in stock assessments of the main Tasmanian fisheries, i.e. scalefish, rock lobster and abalone. There are presently over 9000 recreational gillnet licenses in Tasmania, with an estimated effort, for the first part of the 1995/96 licensing year, of around 100000 net days. The impact on inshore scalefish stocks is unknown but is likely to be significant.

The move towards quota management in the Tasmanian rock lobster fishery has increased the need for accurate stock assessments on which to set catch limits. A complex model of the Tasmanian rock lobster fishery has been developed, with the size of the recreational catch an important input parameter.

The Tasmanian Government is developing management plans for all fisheries including the recreational fishery. The general lack of hard data for the recreational sector is making decision making difficult and uncertain. A number of important management changes are, however, proposed. Particularly significant are those that relate to the use of gillnets and include reductions in the number of nets per licensee and limits on the number of nets that can be used from a boat. If adopted, these changes are unlikely to become effective until the 1997/98 licensing year. Detailed catch and effort information prior to and following implementation of these changes will provide a unique opportunity to assess their effectiveness in reducing gillnet effort (and catch).