Salmon

Australian salmon or Australasian salmon are found in the waters off southern Australia (including Tasmania) and New Zealand. It should be noted that despite the common name, Australian salmon are not related to the salmon (family Salmonidae) of the Northern Hemisphere; the former were named so by early European settlers after their superficial resemblance to the salmoniform fishes.

Australian salmon are popluar amongst both recreational fishers and commercial. Commercially salmon are taken in great numbers by way of purse seine nets and trawling. They are also caught by fishermen along the southern coastline of Australia by beach seining. The Australian salmon is also known as kahawai in New Zealand English.

Recreational anglers often have success with salmon using bait such as cut fish flesh, whole pilchards and garfish on ganged hooks, bottle squid or squid pieces, prawns, beach worms and pipis. Occassionally salmon will also be caught using crabs, cunjevoi or even bread. Salmon are best caught using lightly-weighted or moving baits rather than those anchored to the bottom, they are also avid lure and fly takers.

Within Australia there are four species of slamon which can be described as follows:

• Australian herring, Australian ruff or tommy ruff, Arripis georgianus: Gippsland Lakes, Victoria to Shark Bay, Western Australia; endemic
• Eastern Australian salmon, Arripis trutta: From western Victoria to New Zealand, including the islands of Tasmania, Lord Howe, and Norfolk (rarely to Western Australia).
• Western Australian salmon, Arripis truttacea: Western Australia to Victoria and Tasmania
• Northern kahawai, Arripis xylabion: New Zealand, west to Lord Howe, Norfolk and Kermadec Islands

Australasian salmon are relatively long fish with a streamlined body and a large powerful forked tail - the upper lobe of which is equal to or less than the length of the head in the Eastern Australian salmon, Arripis trutta. The first (spinous, with nine spines) dorsal fin originates behind the pectoral fins, the former being confluent with, but noticeably higher than the much longer soft dorsal fin (with 15 - 19 rays), itself much longer than the anal fin (which has three spines and 9 - 10 soft rays). The pelvic fin is situated in a thoracic position.

The Western Australian salmon, Arripis truttacea, is the largest of the salmon species at a maximum 96 cm (three feet) standard length (that is, excluding the caudal fin) and 10.5 kg in weight. The Australian herring is the smallest of the species at maximum 41 cm (16 inches) fork length (that is, from the snout to the middle of the caudal fin's fork) and 800 g. Australian salmon share a passing resemblance to the unrelated yellowtail amberjack, Seriola lalandi, locally known as "kingfish", with which larger salmon are sometimes confused.

All species are strongly countershaded; dorsal colours range from dark blue-green in A. trutta, green in A. georgianus, and steel-blue to grayish- or greenish-black in A. truttacea; the colours fade to a silver-white ventrally. A smattering of yellow, gray, or blackish spots embellishes the dorsal half, the spots arranged vertically or longitudinally in a series of rows. There are marked differences in subadult coloration: for example, on the flanks of juvenile Australian herring are a series of dark golden vertical bars.

Australian salmon are all known to be "pelagic spawners"; that is, they spawn in open water during the austral spring, releasing a large number of tiny (1 mm in diameter), smooth spherical eggs made buoyant by lipid droplets. The eggs (and later the larvae), which possess an unsegmented yolk, become part of the zooplankton, drifting at the mercy of the currents until the larvae develop and settle. The young salmon then spend the first 2 - 5 years in sheltered coastal bays, inlets, and estuaries until they become sexually mature and begin to move into more open waters. Relatively long-lived fishes, Australian salmon may attain an age of 26 years in Arripis trutta and 7 - 9 years in other species.

Australian salmon form immense schools with hundreds to thousands of individuals, as both adults and juveniles. They are carnivorous and feed primarily on small fish such as pilchard; crustaceans such as krill, copepods, and other zooplankton (the latter comprising the bulk of the juvenile diet). The zoobenthos is also sampled to some extent, with primarily shellfish, crabs, and annelid worms eaten.

Together with the carangids, Australian salmon feed en masse by co-operatively bullying baitfish up to the surface; this herding technique is exploited by seabirds which are quickly attracted to, and feed upon, the foaming mass of fish at the surface.

Aside from seabirds, the salmon are also important in the diets of cetaceans such as Orca and Bottlenose Dolphins; several species of large sharks, for example; great white, dusky, copper, and sand tiger sharks; and eared seals such as the Australian Sea Lion.