Wild barramundi live in freshwater, brackish water or saltwater, and its native habitats include streams, rivers, lakes, billabongs, estuaries and coastal waters of tropical regions.
The majority of production takes place in north Queensland, the Kimberley region of Western Australia and the Northern Territory, where barramundi are produced in outdoor, fresh or saltwater ponds and/or sea cages. In south east Queensland, New South Wales, Victoria, South Australia and southern Western Australia, barramundi are produced in tanks using thermal spring water or fresh water.
Barramundi is a tropical species requiring water temperatures of 20–30°C. However, for commercial growth rates, water temperatures above 25°C are recommended because the amount of feed required by barramundi decreases in line with a decrease in water temperature, which slows growth. In Queensland, maximum food consumption occurs at 27–29°C and decreases to almost zero at 20°C.
In the Northern Territory, the optimum temperature for growth is 28–32°C and the optimum salinity range is 0–36 parts per thousand (ppt).
Growth rates of fish produced in outdoor ponds or cages will vary with seasonal changes in temperature. Fish deaths have been observed when water temperatures drops below 13°C in commercial operations. An extended water temperature drop to below 20°C can result in stress-related deaths and disease outbreaks.
Barramundi can be farmed in a number of ways – ponds, sea cages and indoor recirculating or flow through aquacluture systems.
Farming barramundi in ponds usually involves housing the fish in floating cages for the first part of their grow-out phase. These cages are usually 1.5m deep and can vary in size from 2m x 2m to 6m x 12m and are accessed from raised walkways.
Barramundi are released from the cages when they are around 300g in weight and raised free-range in the pond to a weight of 2-3kg. Ponds can range from 0.2ha to 1.5ha in size and are 2–3m deep. The ponds are normally aerated mechanically and water is flushed to manage ammonia and algal blooms.
If farming barramundi at sea, fingerlings are transferred to sea cages, where they reach market size at about 18-24 months depending on market requirements. These cages are large and robust to withstand environmental conditions.
Indoor recirculating or flow through aquaculture systems
Intensive heated indoor recirculating aquaculture systems tend to consist of a series of large production tanks in a warehouse or shed, connected to a central filter and waste removal system or external settlement ponds.
The benefit of this system is being able to regulate environmental conditions for optimum growth. Additionally, these systems are more compact than ponds, so they can be established in a range of locations, with the potential to be closer to markets than some outdoor pond operations. However, this is a complex system to operate with a high degree of mechanical automation and will require a greater level of management than pond systems.
If seeking to grow barramundi in a state where barramundi is not endemic, an indoor recirculating aquaculture system may be required under licence conditions, in order to protect native fish species.
Barramundi are carnivorous. In the wild they eat other fish (including other barramundi), crustaceans like prawns and mussels, and insects.
In aquaculture systems, barramundi are fed speciality pellets available from aquaculture feed suppliers. Fingerlings are fed 5–6 times a day but feeding decreases to 1–2 times a day as they grow to market size. Broodstock barramundi might be fed fresh seafood, like whole mullet and squid, supplemented with a vitamin mix.