Mulloway are well regarded as a good eating fish with firm white flesh and few bones. The fish may be cooked whole or as cutlets or fillets, with the fillets holding together well when raw and cooked. It is suitable for a large variety of recipes.
Wild mulloway have been commercially harvested and recreationally fished in significant quantities since at least the 1940s. In New South Wales (NSW), commercial catch records show a steady and substantial decline from 380 tonnes during 1973–74 to 37 tonnes during 2008–09. Mulloway are now regarded as overfished.
Aquaculture is an increasingly important means of meeting the world’s demand for protein and consumers’ desire for marine fish to be produced in an environmentally sustainable way. Fish species similar to and related to mulloway are becoming the basis of significant aquaculture industries in many regions of the world, including the United States of America, China, Greece, Italy and Spain.
The mulloway endemic to Australian waters, Argyrosomus japonicas, is considered a good species for aquaculture. They grow quickly, accept artificial food, are highly fecund with good food conversion ratios, tolerate a wide range of salinity and temperature, tolerate low oxygen levels, are not cannibalistic and can be grown at high stocking densities.
To date, they have been farmed mainly in coastal sea cages, however turbid earthen ponds are proving to be a very successful system for commercial production, especially when growers may already have the infrastructure established for prawns or other fish.
While earthen pond production systems are yielding excellent results and market prospects are good, farmed production faces the challenges of any emerging industry; access to low cost fingerlings for grow out and the need to refine feedstock formulations and feeding regimes for greater efficiency and product quality control.
Facts and figures
- Mulloway are a temperate fish, native to Australian waters and several other regions of the world
- Mulloway is the aboriginal name for the fish, meaning ‘the greatest one’ – in Australia the species may also be called jewfish, butterfish and kingfish
- Wild fish spawn at sea and then juveniles settle in turbid waters of estuarine nursery areas until they reach a length of 46cm which takes three to four years
- A 10kg wild fish is likely to be about six to seven years of age
- In the wild, 30kg fish are common and they are thought to live for about 30 years
- Farmed fish present a sustainable alternative to wild-caught mulloway
- In earthen (prawn) ponds, fish can reach market size (1kg+) in under two years, with high survival rates, good growth and minimal disease
- Fish in earthen ponds have high production rates, approaching 14t/ha but may be as high as 20t/ha
- The production of mulloway in earthen ponds is a very new industry and production techniques are still being refined
In 2010–11, 644 tonnes of mulloway were produced in aquaculture systems in Australia.
Sea cage production accounted for 572 tonnes produced in South Australia and 72 tonnes in New South Wales. Sea cage production has stalled in recent years despite a potentially large market for cultured marine fish. In South Australia, mulloway are not achieving suitable growth rates in sea cages; and in New South Wales, commercial interest in reinvesting in sea cage production is currently low due to a limited number of suitable sites, difficulty of the current approval processes and access to development capital.
The mulloway produced in New South Wales were produced in earthen ponds. This form of aquaculture is a new industry, and proving to be a successful alternative enterprise for prawn farmers whose businesses are struggling against low-priced imports of prawns from Asia.
In northern New South Wales, research work since 2008 has shown that prawn farms can be easily and successfully converted to mulloway farms. In terms of production systems, much higher growth rates of mulloway are being achieved in earthen ponds compared with sea cages.
The volume of mulloway sourced from wild-catch fishing is declining as natural populations are overfished and new and more strict fishing rules are applied to commercial (and recreational) fishing in estuaries and the ocean.