Longfin Eel, Anguilla reinhardtii Steindachner, 1867

The Longfin Eel is a large, primarily carnivorous fish that has a broad head, and a large mouth with fleshy lips.

Identification

The Longfinned Eel has well developed pectoral fins, a broad head, and a large mouth with fleshy lips. It can be distinguished from the similar-looking Shortfinned Eel, Anguilla australis, by the length of the dorsal fin. The dorsal fin origin of the Longfinned Eel is well forward of the anal fin origin, whereas the dorsal fin origin of the Shortfinned Eel is above the anal fin origin. The two species also differ in dentition and colouration. The Longfinned Eel usually has olive or brown blotches above and on the sides, fading to pale on the belly. The median fins are brown and the pectoral fins are often yellowish. The Shortfinned Eel is usually a uniform colour and does not have a blotched pattern.

Habitat

The Longfinned Eel lives in rivers, lakes and swamps, but appears to prefer flowing water.

Distribution

The species occurs in Australia, New Caledonia and New Zealand. In Australia, it is known from the entire coastal margin of eastern Australia from Cape York to Melbourne and also from northern and eastern Tasmania and Lord Howe Island.

The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums. Click on the map for detailed information.

Life history cycle

Longfinned Eels undergo a remarkable migration to sea to breed. Adult Longfinned Eels swim downstream* to the sea and then migrate to their spawning grounds near New Caledonia. Female eels can have millions of eggs in the ovaries. Developing leptocephali take about one year to return to the streams of eastern Australia. Glass eels arrive in New South Wales in early Summer. Those that make the additional journey south to Victoria arrive from January to late May. Young eels (called elvers) then swim upstream and spend a number of years maturing in freshwater.

The closely related New Zealand Longfin Eel (Anguilla dieffenbachii) is reported to live up to 60 years in freshwater before migrating. Researchers at NIWA in New Zealand have tagged NZ Longfin Eels in an attempt to identify the location of the spawning grounds. This research is yielding very interesting information.

* Merrick (see further reading) stated that "Anguilla reinhardtii has been observed to move downstream, over dam walls, during daylight hours. Observations of adults migrating out of Warragamba Dam in April indicated that they went over the spillway tail first; they swam normally to 5 metres from the top of the spillway and then suddenly reversed their direction to go over".

View an account of glass eels swimming up a small creek in Palm Cove, Cairns, Queensland.

Danger to humans

From Wikipedia: "Eel blood is toxic (if injected) to humans and other mammals, but both cooking and the digestive process destroy the toxic protein. The toxin derived from eel blood serum was used by Charles Richet in his Nobel winning research which discovered anaphylaxis (by injecting it into dogs and observing the effect)."

References

1. Allen, G.R. 1989. Freshwater Fishes of Australia. T.F.H. Publications. Pp. 240.
2. Allen, G.R., Midgley, S.H. & M. Allen. 2002. Field Guide to the Freshwater Fishes of Australia. Western Australian Museum. Pp. 394.
3. Beumer, J.P. in McDowall, R.M. 1996. Freshwater Fishes of South-Eastern Australia. Reed Books. Pp. 247.
4. Hoese, D.F., Bray, D.J., Paxton, J.R. & G.R. Allen. 2006. Fishes. In Beesley, P.L. & A. Wells. (eds) Zoological Catalogue of Australia. Volume 35. ABRS & CSIRO Publishing: Australia. parts 1-3, pages 1-2178.
5. Merrick, J.R. & G.E. Schmida. 1984. Australian Freshwater Fishes. Biology and Management. John R. Merrick. Pp. 409.
6. Park, A. 1986. Incredible Voyagers. Australian Geographic. January-March 1(1): 24-33. View online.
7. Tsukamoto, K. 2006. Spawning of eels near a Seamount. Nature. 439: 929.

Further reading

1. Nuwer, R. Closing In on Where Eels Go to Connect. New York Times. Online. December 7, 2015