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.
