Most analysts agree that the farming of barramundi, Lates calcarifer, has a bright future in Australia.
The species is hardy, fast growing, and universally regarded as a premium table fish. Barramundi are well suited to grow-out in recirculating tanks.
Being an estuarine fish, it can tolerate a wide range of environmental conditions and, perhaps most importantly, the species thrives at high density.
Barramundi also wean readily onto pellet feed, and grow relatively quickly.
Barramundi are currently farmed in Queensland, the Northern Territory, South Australia, Western Australia and New South Wales.
They are farmed within cages in ponds in northern Queensland and Western Australian and Northern Territory, and within enclosed recirculating systems in the temperate regions of South Australia, New South Wales and southern Queensland.
To be successful, fish farms need a number of services; proven growout technology, a year-round supply of disease free fingerlings, cost-effective feeds, enlightened farm management, clever marketing, and easy sourcing of all the material and equipment needed on the farm.
Natural Distribution:
In Australia, barramundi are distributed in tropical coastal and fresh waters from the Ashburton River in Western Australia to the Noosa River in Queensland. Globally, they are widely distributed in the Indo- West Pacific region from the Arabian Gulf to China, Taiwan, Papua New Guinea and northern Australia.
Barramundi move between fresh and salt water during various stages of their life cycle. Mature barramundi live in estuaries and associated coastal areas or in the lower reaches of rivers. Larvae and young juveniles live in brackish temporary swamps associated with estuaries and older juveniles inhabit the upper reaches of rivers.
Culture Of Barramundi:
Northern Australia
Research into the culture of barramundi in Australia began in 1984 with studies carried out by the Queensland Department of Primary Industries. This work was aimed at adapting culture techniques developed in Thailand to Australian conditions.
Eggs for culture operations initially came from wild broodstock and after hatching, the larvae were reared in a flow-through tank system until they reached fingerling size (30 to 40 mm total length).
Most operations now retain captive broodstock and use extensive systems of fertilised brackish or salt water earthen ponds for larval rearing. This method has the advantages of requiring less labour and hence is less expensive than tank system hatcheries and larval rearing facilities for the production of an equivalent number of larvae.
In grow-out operations, fingerlings are usually stocked in floating cages in ponds where they are held until they achieve a marketable size of about 400 grams - usually reached in as little as 6 months. Growth rates vary, and regular grading of the fish is required to reduce cannibalism on smaller fish. Some farms will also produce larger sized barramundi to supply market demand for larger sized.
South Australia:
There are currently twenty registered barramundi farms in South Australia. One of these, located adjacent to a hot artesian bore in the south east, rears fish in a flow-through tank system, while the majority utilise recirculating systems to culture barramundi. Using recirculation systems enables yearround production of fish that can be reliably maintained and managed on a commercial scale.
As barramundi are a tropical fish, to produce barramundi in South Australia, they must be reared in a totally enclosed temperature controlled environment. They cannot survive in outdoor ponds south of their natural distribution.
Barramundi farms consist of a fully enclosed, insulated building in which grow-out tanks are housed. A biological filter treats the dissolved wastes in the water, while at the same time providing aeration. Constant mechanical filtration removes solids and particulate material from the water.
The combination of biological and mechanical filtration means that a farm can operate with maximum water consumption of around 10 – 20% total water capacity per day. This relatively low water consumption means the water can be heated and waste-water can be disposed of on land or used for irrigation.
Rotational stocking and harvesting allows a recirculation system to reliably supply quality fresh fish throughout the year. Tanks are stocked with fish in rotation. When production first commences fish are stocked every month into a new tank.
After the fifth month of stocking, the fish that were stocked in month one are ready to be harvested. Every month thereafter, fish are harvested from each tank and new fish are stocked.
An efficient recirculating system should be fully enclosed and allow a greater degree of disease management than any other type of fish farm. The emphasis of disease management is on preventing the entry or outbreak of disease. There are five ways in which this is achieved:
- All the fingerlings used in the farms are produced according to a strict protocol. Under this protocol the eggs are reared in artificial sea water and the fingerlings tested for any signs of disease in the hatchery and in the nursery.
- The only water which can be used in the farms is bore water. This requirement is specifically aimed at minimising the opportunity for fish diseases to be introduced into the farm through the water supply. Although it is possible to treat the water from rivers or dams to remove disease organisms, the cost of failsafe sterilisation of water is generally substantially greater than the cost of establishing and operating a bore.
- The food which is used in the farms is manufactured and heat treated during the manufacturing process. The feeding regime for the farms is based on a quality controlled and tested pellet diet.
The use of local or home made diets is avoided.
- The farms are fully enclosed and the possibility of introducing airborne, water or bird carried diseases is limited. The day to day operations use procedures which limit the opportunity for disease organisms to enter the farm.
- Stocking densities are up to 50 kg/m3 . The production tanks are dark in colour and the farms have low light levels. This is to maintain a stress free environment. Fish that are stress free will grow more rapidly and are much less susceptible to infection or disease.
Recirculating systems can cost anywhere between $50,000 up to a few million to construct depending on the size and the components of the system and its production capacity. Growers claim that it can take up to a year or so before initial returns can be made.
A recirculating aquaculture facility may be established anywhere that there is power and access to adequate water supply. With proper design, recirculating systems use minimal water, make very little noise and produce little waste. Recirculation systems should be isolated from disease, predators and free of uncontrollable environmental changes.
Risks associated with recirculation aquaculture are inherent, in that all facets of life support and culture are placed in the hands of the manager.
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