New Zealand longfin eel
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| Anguilla dieffenbachii Gray, 1842 |
The New Zealand longfin eel, Anguilla dieffenbachii, is one of the 15 species of eel in the family Anguillidae. It is found only in New Zealand (including the Chatham Islands), in all its waterways. They do not usually exceed 1.2 m in length and 10 kg in weight, but exceptional specimens 2 m long and weighing over 50 kg have been reported. The female is consistently almost twice the length of the male.
The body is long and snakelike, roughly tubular and the head is small, with the jaws reaching back to behind the eye. The anal fin starts about half way along the underside of the body, and the dorsal fin midway between this and the hind edge of the pectoral fin, and this is an important diagnostic character. The jaws contain many rows of fine sharp teeth that project backwards, and there are vomerine teeth on the roof of the mouth.
Long tubular nostrils project forwards from the upper lip and behind these are the relatively small eyes.
Coloration is a dark brown to grey-black above and yellow or grey below, the fins being the same colour as the body.
Like the other anguillids, New Zealand longfin 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. 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 400 m in length, where they remain until they reach maturity at between 11 and 34 years for males and 24 to 47 years for females. They are carnivorous, eating crustaceans, snails, frogs, insect larvae, and in the case of the largest eels,fish.
Like other angullids, New Zealand longfin 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 °C.
New Zealand longfin eels make excellent eating. For the Māori people of New Zealand, starved of protein after the extinction of New Zealand megafauna, the New Zealand longfin 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.
The epithet dieffenbachii refers to German naturalist Ernst Dieffenbach.
[edit] References
- "Anguilla dieffenbachii". FishBase. Ed. Ranier Froese and Daniel Pauly. February 2006 version. N.p.: FishBase, 2006.
- Tony Ayling & Geoffrey Cox, Collins Guide to the Sea Fishes of New Zealand, (William Collins Publishers Ltd, Auckland, New Zealand 1982) ISBN 0-00-216987-8
