Australian herring is a staple species for recreational and commercial fisheries in the south of Western Australia. Although named for a superficial resemblance to the herring of the northern hemisphere, they are not related. Australian herring can grow up to 41 cm in length but most are caught at about 20-25 cm. An endemic Australian species, it occurs in the coastal waters of southern Australia. Its lifecycle depends on prevailing currents. Australian herring populations are all from the same genetic stock.
Australian herring actually belong to the perch family. The Australian salmon (Arripis truttaceus) belongs to the same family, and in its juvenile stage, can be easily confused with adult herring (Arripis georgianus).
Juvenile Australian salmon are silvery white and smooth scaled, with a yellow pectoral fin (behind the head) and several rows of golden or brown spots on their backs and sides. Australian herring are silvery with vertical rows of golden spots on the upper side of the body and black tips to the tail fin. The scales are slightly rough. Herring have a larger eye and more rounded head.
Distribution and habitat
Australian herring live in southern coastal areas from Shark Bay in Western Australia down to Albany, across the south coast to South Australia and as far east as Victoria.
They are found mainly inshore, around offshore islands and in southern estuaries such as Wilson Inlet and Oyster Harbour.
Australian herring spawn (release sperm and eggs) in WA, around reefs off the lower west coast from Perth to Cape Leeuwin from late May to early June.
Each female releases 100,000 eggs on average. Currents carry eggs, larvae and juveniles east along the south coast. Tiny juveniles settle in inshore waters as far east as Victoria.
Some also settle on the lower west coast, close to where they were spawned, particularly in Geographe Bay. This is thought to be a vital source of recruitment (addition of young fish to a population) for the west coast fishery.
Most reach sexual maturity at two to three years of age and about 20 cm in length. To spawn, those that have grown up in nursery areas in South Australia and Victoria return to WA, and the lifecycle begins again.
After spawning, most adults stay in WA, feeding inshore. Some move north as far as Shark Bay.
A number enter south coast estuaries where there are plenty of food sources, such as shrimp, and may grow larger than coastal herring. When trapped in an estuary, they can remain there for life, without breeding.
The lifecycle is influenced by the Leeuwin Current, which transports warm tropical water south along the WA coast.
In years when there is a strong current, adults don’t travel as far up the coast. As to larvae, a strong current takes them as far as Victoria, while in years of a weak current, most remain in WA waters.
These factors affect juvenile recruitment levels, the abundance of adult fish, and subsequently, catches.
Young herring eat small crustaceans living in weed and seagrass. Adults eat small fish, such as blue sardines, juvenile fish, small crustaceans and insects that live in seaweed or have been washed into the water.
Herring are food for Australian salmon, mulloway, yellowtail kingfish, sea birds, seals and sea lions. They school in large numbers – a defence mechanism against predators – over seagrass meadows and reefs, which gives them additional protection. They school at depths of only one to two metres from the surface.
Illustration © R. Swainston/www.anima.net.au