Synopsis of biological, fisheries and aquaculture-related information on mulloway Argyrosomus japonicus (Pisces: Sciaenidae), with particular reference to Australia

Argyrosomus japonicus is a member of the family Sciaenidae, which are commonly known as drums and croakers. A. japonicus occurs in estuarine and nearshore Pacific Ocean and Indian Ocean waters surrounding Australia, Africa, India, Pakistan, China, Korea and Japan. The biology of A. japonicus is relatively well studied in South Africa, and more recently studied in Australia, but no information is readily available from other areas of its distributional range. The early life history distribution of A. japonicus may differ among regions, with their distribution in estuaries linked to salinity, turbidity, freshwater flows and depth of water. Studies in South Africa and Australia found that juvenile fish grow rapidly, attaining 35 cm TL in 1 year and 87-90 cm TL in 5 years. Sexual maturity also differs among regions and is attained at 2-3 years of age and >50 cm in eastern Australia, 5-6 years of age and >80 cm TL in western Australia and southern Africa. The maximum reported length and age of A. japonicus is 175 cm and 42 years, respectively. Spawning most likely occurs in nearshore coastal waters although there is evidence to suggest that it may also occur in the lower reaches of estuaries. Time of spawning varies among geographic localities and is probably linked to water temperature and oceanography. Juvenile fish (<2 years) appear to be relatively sedentary, but sub-adults and adults can move relatively long distances (>200 km) and such movements may be linked to pre-spawning migrations. A. japonicus is important in many recreational and commercial fisheries, but like other sciaenids, is prone to overfishing. It is classified as recruitment overfished in South Africa and overfished in eastern Australia. Although much research has been done to minimize the capture of juveniles in Australian prawn-trawl fisheries, greater protection of spawners and improved fishing practices to enhance survival of discarded juveniles, particularly from prawn trawling, may be required. An aquaculture industry is developing for A. japonicus in Australia and preliminary research on the impacts and success of re-stocking wild populations has begun in an attempt to arrest the apparent decline in populations.