Currently there are about 180 licensed silver perch growers in all states; however, only about a third of these are producing fish commercially. Although a small number of farms achieve high production rates, most farms are inefficient and not producing anywhere near their potential. Survival, growth and production rates are much lower, and FCR's higher than achievable with good husbandry and management. Fish are being lost from disease and poor water quality, and growth rates are perceived by some farmers to be "slow".

Consultation with industry has identified that research into winter diseases and health management is a high R&D priority.

Diseases, in particular those caused by infectious agents, are recognised as an important threat to the viability of finfish aquaculture. In 1996/97 a pilot monitoring program aimed at identifying diseases causing significant production losses in silver perch was conducted on a coastal zone farm in north-eastern NSW. Results suggested that growth rates were reduced by ecto-parasitic infestations and by adverse water quality conditions. More recently, in 1998 and 1999, there have been reports of serious disease problems that have caused significant losses on some silver perch farms. These have included regular outbreaks of fungal diseases during winter, particularly in the cooler, inland areas of eastern Australia. It appears that some, or most of these outbreaks are not just the result of poor husbandry. The fungal disease, winter saprolegniosis is a serious problem in the large channel catfish industry in the USA, and relatively new winter fungal diseases have been reported in freshwater fishes in other parts of the world. There is strong evidence of a similar, but currently undescribed winter fungal disease in silver perch. Clearly there is a need to describe the major diseases, including important emerging diseases, on silver perch farms and identify their causes. Cost-effective control and prevention measures can then be developed.

More broadly, as the industry matures, silver perch farmers are becoming increasingly aware of the importance of systematic, cost-effective measures aimed at reducing disease-related losses to acceptable levels. However, no such validated programs are currently available to the industry. To fill this vacuum, it is essential that "Health Management Programs" i.e. generic disease control and prevention programs, are developed, validated and extended to farmers. These programs can be modified to suit the needs of individual farms and integrated with routine management activities. On individual farms, the programs will comprise (a) broadly targeted measures based on established principles and aimed at general disease prevention, early detection and control, with (b) specifically targeted measures aimed at reducing losses caused by important diseases (e.g. winter diseases) occurring in the farm's geographic area.

The production capacity of silver perch (10 tonnes/ha/year), the established culture techniques, the large number of inefficient farms, and the ready availability of sites provide the basis for a dramatic increase in production of silver perch over the next 5 to 10 years. However, research to address the current disease problems is required to maximise the value of previous research and to enable the industry to realise its full potential.

Research into freshwater crayfish has resulted in steady production increases in Australia over the last two decades. In an effort to take production and profitability to the next level, scientists in Australia have taken the opportunity to host IAA 13. Furthermore, the strategy of organisers has been to couple the event with a one-day workshop/seminar focussing on Australian crayfish aquaculture. The timing of the workshop/seminar (the day before the conference begins) has been set to attract participation from international astacologists, already in Fremantle for IAA 13. This will promote technology transfer into Australia, by giving access to local industry participants at a non-scientific level.

Following on from the one day aquaculture workshop, the IAA 13 symposium will provide a mechanism for the direct transferal and dissemination of cutting-edge research within Australia, as well as providing an international platform for local crayfish scientists to present their research to world-renowned astacologists, and pursue collaborative links for future research. Fisheries WA are planning to present at least six papers at the symposium, including recent research into yabby and marron aquaculture.

The fragility of crayfish aquaculture was highlighted in the 1980s when the crayfish plague, Aphanomyces astaci, obliterated stocks throughout Europe. Research has subsequently identified Australian crayfish as being extremely vulnerable to this infection, reminding Australia of the importance of comprehensive translocation policies. This has been further highlighted by recent disease concerns within the yabby industry. A forum for discussing these issues, and hearing from scientists representing afflicted countries, will augur well for the continuation of sound policy to protect Australia's prime market niche.

As with the majority of world wild fisheries, the sustainable landings of Australian rock lobsters have reached their maximum. Nevertheless, demand from the world markets to which Australia exports to continue to increase. Increases in rock lobster production will only arise from aquaculture production.

One approach towards aquaculture production is that of ranching. It is already possible to grow rock lobsters from newly-settled puerulus harvested from natural recruitment, in commercial fisheries areas, to market size in 2-3 years using cost effective diets. However, natural settlement is unreliable and recruitment from the wild fishing sector has many political implications. The only method for resolving this problem is to develop a cost/effective larval culture technique to produce pueruli from eggs.

The participants at the FRDC Rock Lobster Propagation workshop in 1999 concluded that culture of pueruli from eggs was biologically feasible and worthy of investigation. The workshop identified several components needing to be addressed by further research in order to improve the survival and growth of larvae through the extended larval phase, including:

1. Advancing the design of larval culture systems.
2. Identifying larval nutrition requirements and production of cost effective larval feeds.
3. Reducing the long larval period.

Preliminary research of the RLEAS subprogram in 1999/00 indicates that progress can be made towards addressing the three major constraining components. Based on the recent Workshop for Rock Lobster Enhancement and Aquaculture Subprogram (RLEAS) in Hobart (February 2000), the RLEAS Steering Committee requested that separate funding applications be submitted for the research effort towards issues of nutrition and larval period.

This proposal represents an attempt to develop alternative technologies that would allow the prawn trawl industry to meet present and future strict environmental standards at a reduced operating cost. The proposal is not without risk, but reflects a genuine need to consider alternative fishing approaches outside the current thought envelope. If successful it would allow the industry to claim high environmental standards, meeting or exceeding the community expectations.

Alternatives to established fishery harvest methods are essential to meet ecologically sustainable development (ESD) requirements as dictated by international (UN) and national legislation (both federal and state) covering the marine environment. In recent years drift nets have been banned in many areas due to their detrimental impacts on non-targeted species and ecosystem structure. Similarly, ground trawling has been identified as a harvest technology that requires either restriction or banning due to its putative detrimental impacts on benthic ecosystems and disruption to food webs. Whereas drift net has been largely replaced by the sustainable and targeted method of hook and line harvesting, there are few alternatives to ground trawling.

Traps are used extensively for the harvesting of crustacea. Suitably designed pot traps can result in a minimum of by-catch and target individuals of specific size classes. However, pot trap fisheries utilise food as bait by which to attract the targeted species into the trap. Baited traps and pots are used for the commercial harvesting of pandalid prawns in the east Pacific and North Atlantic, where average catch/vessel/day of fishing effort is 80-110 kg. A smaller pot fishery exists for penaeid prawns in various parts of the Pacific basin and the Caribbean. However, attempts to date to develop a large pot trap fishery based on food bait for penaeid prawns have been largely unsuccessful.

It is proposed that chemical attractants, and not food bait, be examined as a means to harvest penaeid prawns in pots. The development of alternative harvest methods could form a non-trawl fishery with minimum by-catch, open up new areas to harvesting which are unsuitable for trawling, and produce a less stressful method to collect broodstock P. monodon prawns for the aquaculture sector as well as have spin-off potential for the development of pot trap fisheries for other species of crustacea.

Biofouling on pearl oysters, and the equipment used in culture of these oysters, is a major cost to the pearl industry throughout Australia. Rapid biofouling necessitates frequent cleaning, a process that is labour and capital intensive. The cost of cleaning, as estimated by the Pearl Produces Association, is approximately $15 to $20 per shell per year. The cost to the industry as a whole is likely to exceed $20 million/annum. Indirect costs include losses due to shell mortality, reduced growth rates and reduced pearl production from effects to nacre deposition.

Biofouling of oysters and equipment presents several problems if unattended. Invertebrates dominate fouling communities common to the pearl industry and these compete directly with pearl oysters for food. Several organisms, such as the sponge Cliona (red arse) and boring shellfish, directly attack the pearl oysters and result in shell damage or mortality. Excessive fouling of underwater surfaces also increases drag forces and increase the susceptibility of lines to storm damage. It is noteworthy that frequently cleaning is also problematic since evidence suggests that this type of handling reduces shell growth.