Barramundi - aquaculture prospects

Introduction

The barramundi (Lates calcarifer) is a large predatory fish found in tropical regions of Australia. It has a natural distribution extending from the Ashburton River in Western Australia (WA), throughout the Northern Territory (NT), to the Maryborough River in Queensland (QLD). The barramundi is a greenish grey on the dorsal surface, changing to silver on the sides. The mouth is large and the eye glows red at night under flashlight.

The species is portrayed widely in northern Australian Aboriginal mythology where it has been used historically as a primary food item. It is also commonly regarded as the premium recreational sportfish in northern Australia. The barramundi's attributes as an aquaculture species have more recently been realised.

Biology

Barramundi can tolerate all levels of salinity from fresh to seawater and frequent a number of environments including coastal regions, estuaries, landlocked freshwater billabongs and rivers. Juvenile males spend the beginning of their lives in the freshwater reaches of rivers, migrating to a brackish environment to breed. All barramundi are hermaphroditic and begin their lives as male, changing sex to female at a weight of around 5kg.

In nature, spawning takes place between November to February, on the third-night full moon, coinciding with the mid-evening high tides. Each female will lay up to 40 million eggs. The eggs hatch within 18 hours and the fry are ready to feed two days later.

Barramundi are carnivorous, feeding on live prey such as fish and prawns. The fish grow large and rapidly and have been known to reach over 5ft in length and weighing 60 kg. Their majestic appearance and size make the barramundi a premier sport and table fish and a valuable recreational fishery based on this species thrives within the tropical reaches of Australia.

NSW industry status

The barramundi is not native to NSW and is not currently bred in hatcheries in this State. However a large hatchery industry exists in QLD and the NT. There are a number of licensed barramundi farms in NSW. See the NSW DPI aquaculture production report for the current figures.  In 2000 there were five licensed barramundi farms in NSW. The colder climate and potential power costs involved with tank culture have, to some extent, restricted the development of this industry.

Due to the small number of farms, production of this species has been limited. Barramundi are however cultured in large volumes in tropical Australia, as well as overseas, particularly in places such as Taiwan, Vietnam and China where they are known as 'Sea Bass'.

The barramundi is known to be a potential carrier of the Barramundi Nervous Necrosis Virus (BNNV) which has potential to affect a number of species native to NSW. As such, NSW DPI has imposed tight restrictions on the culture of barramundi in this State.

Growth and reproduction

Due to the potential for the spread of BNNV to native NSW fish, culture of barramundi in NSW has been restricted to intensive recirculation tanks only. Most of the research done in northern Australia has focused on pond culture, however, much of this technology is being transferred to tank culture systems, particularly in the southern states and the cooler regions of Queensland. Tank culture technology has made it possible for most mainland states to produce barramundi.

Stocking rates in tank systems vary, depending on the capacity of the system and the intensity of the operation. Many producers work on a stocking rate of around 30-40kg/m3, however more advanced systems may be able to increase the stocking rate, depending on the experience of the farmer and husbandry practices used.

The optimum temperature for barramundi culture is 28°C, with acceptable growth rates between 26-30°C. Temperatures below this range will result in decreased metabolism and growth. Barramundi generally stop feeding at temperatures below 20°C. To maintain acceptable growing temperature conditions, some existing farms rely on the use of warm subterranean bore water and climate controlled or insulated sheds. Expensive alternatives include the heating of individual tanks with electric submerged heaters. At optimum temperatures, barramundi can be raised to market size (500g) between 6-12 months.

Due to the carnivorous nature of barramundi, a high protein diet is required for efficient growth. Commercial diets are readily available from a number of feed manufacturers and are generally produced in a floating or sinking pellet. Food conversion ratios (FCRs) for barramundi should be in the range of 1.5-2:1 (kg of food:kg of weight growth), however lower FCR's have been reported by some industry members.

The very nature of intensive recirculation tank farming means that water requirements are much lower than that for pond culture. However, the high stocking densities, reliance on powered biofilters and use of high protein feeds can lead to water quality deterioration if left unchecked, therefore greater supervision in required. Tanks should be cleaned and biofilters back-washed regularly to avoid blockage. Backup power generation should also be supplied.

Behaviour

Barramundi are gregarious (readily school) and adapt easily to high stocking densities. However, by nature they are also highly cannibalistic and will eat tank mates up to two thirds of their own size. To avoid problems of cannibalism, stock should be graded at least once a week and separated into appropriate size classes. This will also reduce size variation between groups (assist in marketing), while reducing expensive mortality through cannibalism.

Site selection and system design

Site selection for tank culture has fewer constraints than pond based culture including reduced land and water requirements and potential access to more areas due to reduced soil type and topography limitations. In temperature controlled systems, the need to farm in a suitable climate is also reduced. However, due to the risks associated with the culture of a non-native species discussed earlier, strict criteria must be followed in selecting a barramundi-farming site in NSW. This includes the following:

• Site must be above the 1/100 year flood heights.
• Site must be at least 500m from a natural waterway.
• Access to good quality water.
• Adequate area for expansion and effluent disposal.
• Close to markets and infrastructure.

Basic intensive recirculation systems consist of a number of tanks (usually 1000-13000L or larger in size) housed within a vermin proof and preferably climate controlled room or shed. Tanks are independently or group-filtered by solids removal filters and large biofilters, which are used to strip nitrogenous waste and nutrients from the water. Recirculation systems can also incorporate a number of other filtration units including UV and ozonation systems to disinfect water, protein skimmers to remove protein based wastes etc. After passing through the filters, the water is then recycled back to the tanks.

To comply with the NSW DPI Barramundi Farming Policy (also on this site), culture facilities in NSW must meet a number of additional design requirements including provision of a bund wall, effluent sterilization facilities, self draining floor, provision of sterilizing equipment eg foot-baths, etc. Proponents should consult the Policy and discuss the proposal with NSW DPI Aquculture Unit prior to lodging.

Water quality

The osmoregulatory abilities of barramundi allow their culture in both freshwater and saltwater environments and they have the ability to quickly acclimatize to changes in salinity. They are also very hardy and generally do well in highly intensive situations. However, in order to maximise growth, tank conditions should remain as close as possible to optimum levels. The farmer should monitor water quality and fish health closely and take action immediately where required.

In the initial stages, barramundi should only be stocked at a rate that the system can handle. This can be increased, as the farmer becomes more experienced. Dissolved oxygen levels should be between 4-9ppm, however levels as low as 3ppm will be tolerated for very short periods. Free ammonia levels should not exceed 1mg/L and temperatures should be maintained at 26-28°C. Barramundi will tolerate exposure to levels slightly outside of the ranges listed above but will result in slowed growth rates and stress. Prolonged exposure to sub-optimum conditions will result in increased incidence of disease and death.

Diseases and parasites

Barramundi are naturally susceptible to most bacterial, fungal and parasitic infections particularly at times of stress. This is as with most other aquaculture species and can usually be avoided by appropriately quarantining new stock before release into culture tanks, maintaining water quality and a stress free environment and regular disease monitoring of stock. In the event of disease outbreak, stock can sometimes be effectively treated by salt or freshwater bathes, or via veterinarian prescribed treatments.

Of particular concern to NSW DPI are the aforementioned BEV and the possible introduction of this virus to NSW. To address these concerns NSW DPI have included provision within the Barramundi Farming Policy for the sterilization of all effluent to be removed, as well as a specific import protocol for the importation of barramundi fingerlings from out-of-state. This includes the testing of fingerlings for presence of the BEV as well as other diseases and virus. This policy will not only reduce the chance of translocation of the virus into NSW, but also ensures that the farmer has a guarantee of healthy good quality seedstock.

Marketability

One advantage to barramundi farmers is that the species has been commercially fished for a number of years, and as such has a well-established position in the market place. There are a number of product presentations available to producers, including the live fish trade, plate size whole (300-500g) trade and fillet or larger whole fish (2kg) trade. The reputation of barramundi as well as its premium edible properties (white, firm, mild tasting) also provides a good marketing platform for new producers.

Barramundi (cultured and wild-caught) is sold in most major fish markets or retail outlets, with cultured barramundi usually in the form of the whole plate size product. Live fish are also sold, targeted mainly at the Asian restaurant trade. Farmers usually receive an average price of around $9-10/kg at the farm gate for barramundi, with higher prices for value added products eg fillets and live fish. The average price used to be higher however, it has been driven down by the number of new producers entering the industry, as well as cheaper imports from other countries such as Vietnam.

Due to the higher production costs associated with barramundi culture compared to overseas producers, there is probably only limited potential to create export markets for this species.

Further information

For further information, call NSW DPI: Port Stephens Fisheries Centre on  02 4916 3900.

Copies of licensing and policy requirements for barramundi are available from here. Further information on the farming of barramundi can also be obtained from the following references.

References

Barlow, C (1998). 'Barramundi'. The New Rural Industries - A Handbook for Farmers and Investors. Rural Industries Research and Development Corporation.

Forteath, N (1990). A Handbook on Recirculating Systems for Aquatic Organisms. Fishing Industry Training Board of Tasmania Inc, Australia.

Hart, P and O'Sullivan, D (eds.) (1993). Recirculation Systems: Design, Construction and Management. Aquaculture Sourcebook, Tasmania.

NSW Fisheries (1997). Barramundi Farming Policy - NSW Fisheries Policy Paper.

Phillips, C (1998). 'Barramundi Farming'. Proceedings from the Queensland Warmwater Aquaculture Conference (Status and Potential) 1998. Aquaculture Information Technologies (ed).

Rimmer, M (1995). Barramundi Farming, an Introduction. Queensland Department of Primary Industries