Short-finned eel

From Academic Kids

Short--finned Eel
Scientific classification
Kingdom:Animalia
Phylum:Chordata
Class:Actinopterygii
Order:Anguilliformes
Family:Anguillidae
Genus:Anguilla
Species:A. australis
Binomial name
Anguilla australis
Richardson, 1841

The Short-finned eel (Anguilla australis) is one of the 15 species of eel in the family Anguillidae. It is native to the lakes, dams and coastal rivers of south-eastern Australia, New Zealand, and much of the South Pacific, including New Caledonia, Norfolk Island, Lord Howe Island, Tahiti, and Fiji.

The body is long and snakelike, roughly tubular and the head is small, with the jaws reaching back to below the eye or further. The dorsal and anal fins are of roughly equal length. The colour varies considerably from one individual to another; a deep olive-green is typical but it can be much lighter; golden or even (rarely) yellowish. There are no markings of note, but the underside is pale, often silvery, and the fins greenish. When full grown, they reach about 90cm.

They are common throughout the lowlands of New Zealand, including both Chatham and Stewart Island, but tend not to ascend as far inland as longfin eels. In Australia, they are restricted to the area on the seaward side of the Great Dividing Range, from about Mount Gambier in western South Australia to the Richmond River in northern New South Wales. Unable to scale the Great Divide, and not extending as far west as the outlet of the Murray River, they are excluded from the thousands of miles of waterways that drain inland eastern Australia.

Like the other anguillids, Short-finned eels are catadromous: when they reach maturity, they stop feeding and migrate downstream to the sea, then anything up to three or four thousand kilometres to a spawning ground in deep water somewhere in the Coral Sea off New Caledonia. (For a comparison with northern hemisphere eels, in particular the European eel, see eel story.) The larvae drift on the ocean currents and eventually reach coastal waters, where they metamorphose into elvers (tiny, semi-transparent eels). From there, they migrate upstream, traversing numerous obstacles—if necessary, leaving the water and travelling short distances over moist ground. They are well fitted to this task, being able to absorb 50% of the oxygen they need through the skin. Eventually, they take up residence in a lake, swamp, dam or river, typically occupying a home range of about 400m in length, where they remain until they reach maturity at about 14 years for males and 18 to 24 years for females. They are carnivorous, eating crustaceans, fish, frogs and even small birds.

Like other angullids, Short-finned eels are remarkably hardy: they can tolerate high water temperatures and low oxygen concentrations, endure long periods without food, and bury themselves in mud or sand and enter an energy-saving torpor when the water temperature drops below 10 degrees. They are one of the few Australian freshwater fish to have coped well with the wholesale introduction of European and American species.

Short-finned eels make excellent eating. Prior to European settlement at least two Aboriginal Australian civilisations farmed eels on a large scale, trading smoked eel with distant communities in return for other goods. For the Maori people of New Zealand, starved of protein after the extinction of New Zealand megafauna, the Short-finned eel was a significant food resource. Present-day recreational anglers catch and eat them regularly, and New Zealand has a well-established commercial eel fishery.

References:

  • Allen, Midgley & Allen, Field Guide to the Freshwater Fishes of Australia, Western Australian Museum, 2002. ISBN 0730754863.
  • National Institute of Water & Atmospheric Research, Atlas of New Zealand Freshwater Fishes (http://www.niwa.cri.nz/rc/freshwater/fishatlas/species/anguillidae.htm).
  • info on fishbase (http://ichtyonb1.mnhn.fr/Summary/SpeciesSummary.cfm?ID=297&genusname=Anguilla&speciesname=australis%20australis)
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