Summary

In Australia, research under this ACIAR project and a complementary FRDC project have provided the base for the development of diets for silver perch (Bidyanus bidyanus). This species is a new species for aquaculture and this is the first major nutritional study conducted. Most commercial diets now in use were formulated and evaluated by the project leader and contain only 5% fishmeal. Major nutritional requirements for silver perch are now known and the potential for a wide range of available ingredients thoroughly evaluated. Commercial feed manufacturers now have the information to formulate low-cost, effective diets using Australian agricultural ingredients, with no fishmeal.

Development of low-cost effective diets has been of critical importance to the development of the silver perch farming industry in Australia. This industry is expanding rapidly. Nutritional research by NSW Fisheries (including that under this ACIAR project and a complementary FRDC project) has led to the development of diets based on Australian agricultural ingredients such as meatmeal, poultry offal meal, lupins, field peas, canola and wheat with no need for expensive imported ingredients such as fishmeal. These diets have been adopted by commercial feed manufacturers (some have retained 5% fishmeal) and the cost of feeding silver perch has now been reduced to around $1.00/kg of fish. The overall cost of production on efficient farms is below $5.00/kg.

Annual production in NSW doubled each year from 2.6 tonnes in 1992/93, to 81 tonnes in 1996/97, and around 250 tonnes in 1997/98. An additional 30-50 tonnes are farmed annually in Queensland. There are around 400 ha of ponds completed or under construction in NSW and Queensland. Currently there is a low proportion of permit holders producing fish, and a small area of ponds under culture. Most operational farms, and consequently the industry as a whole, are inefficient and not producing any where near their potential. Successful nutrition research and subsequent commercial diet development combined with the production capacity of silver perch in ponds and the large number of licenced, but unproductive or inefficient farms, provide the basis for a dramatic increase in production over the next 5-10 years. If the industry realises this potential, it will become one of Australia's largest fisheries.

In Thailand, research under the ACIAR project has provided a sound base for diet development from the hybrid walking catfish (Clarias macrocephalus x C. gariepinus). In similarity with the situation with silver perch, this is the first major nutrition study conducted with the hybrid walking catfish. It has become clear that the hybrid walking catfish has somewhat different nutritional requirements compared with either parent species.

Partly as a result of this project, hybrid walking catfish culture has expanded enormously in Thailand. Estimates of catfish production in Thailand when the project commenced were about 50 000 t/yr. Recent figures suggest current production now exceeds 60-70 000 t/yr. The project has contributed to this expansion by making technology for nutritionally adequate farm-made diets widely available. This has been achieved through a focused, comprehensive extension program involving extension articles and booklets (over 12 000 copies of one of these have been printed), video presentations (screened on national television) and farmer-orientated workshops (over 220 people have received comprehensive training in farm-made feeds).