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Numbfish
Hypnos monopterygium (Shaw & Nodder 1795)

A Numbfish partially buried in the sand at a depth of 4 m, west of Lilli Pilli Point, Port Hacking, New South Wales, April 2000. View larger image.

A Numbfish at a depth of 15 m, Shiprock, Port Hacking, New South Wales, January 2002. View larger image.

A Numbfish at a depth of 15 m, Shiprock, Port Hacking, New South Wales, January 2002. View larger image.

A 40 cm long Numbfish at a depth of 8 m, Shiprock, Port Hacking, New South Wales.

A gilled leech Branchellion sp beside the nostril of a Numbfish. This image was taken at a depth of 14 m, Cabbage Tree Island, outside Port Stephens, New South Wales, April 1999. View larger image.

The Numbfish is shaped like two discs. The head and pectoral fins form a large disc, while a second smaller disc is formed by the pelvic fins. Located on the second disc are two small dorsal fins, immediately followed by a similar-looking caudal fin.

This species can vary from grey or light brown through to black.

It grows to at 60 cm in length but is uncommon over 40 cm.

The Numbfish can deliver powerful electric shocks with an electric organ located in each pectoral fin. This organ is used to shock crabs, worms and fishes, which make up the Numbfish's diet. The electric organs of the torpedo rays (family Torpedinidae) can also deliver strong electric shocks (50 amps, with peak of pulses sometimes exceeding 1 kilowatt).

To swallow relatively large prey whole, the Numbfish is able to greatly expand its mouth. (View the letters on feeding Numbfish and Numbfish that had eaten a rat, a penguin and a Three-bar Porcupinefish)

This species is found on sand and mud bottoms in shallow bays and estuaries, but is also known to depths over 200 m. When seen by divers it is usually buried in the sediment where a telltale rounded depression gives away its presence (view image).

The Numbfish is endemic to Australian waters. It is recorded from southern Queensland, around the south of the country and north to the north-western coast of Western Australia. It is rare in Victoria and absent from Tasmania.

View a map of the collecting localities of specimens in the Australian Museum Fish Collection.

Related links

• For more information on how the Numbfish produces electricity view the FAQ page.
• View a low resolution movie clip (87k) of this species. Go to the movies page for high and low resolution versions.

Further reading

1. Edgar, G.J. 1997. Australian Marine Life: the plants and animals of temperate waters. Reed Books. Pp. 544.
2. Hoar, W.W. & D.J. Randall. 1971. Fish Physiology. Sensory systems and electric organs. Academic Press. Volume V. Pp 347.
3. Last, P.R. in Gomon, M.F., Glover, C.J.M. & R.H. Kuiter (Eds). 1994. The Fishes of Australia's South Coast. State Print, Adelaide. Pp. 992.
4. Hutchins, B. & R. Swainston. 1986. Sea Fishes of Southern Australia. Complete Field Guide for Anglers and Divers. Swainston Publishing. Pp. 180.
5. Kuiter, R.H. 1996. Guide to Sea Fishes of Australia. New Holland. Pp. 433.
6. Kuiter, R.H. 2000. Coastal Fishes of South-eastern Australia. Gary Allen. Pp. 437.
7. Last, PR & J.D. Stevens. 1994 Sharks and Rays of Australia. CSIRO. Pp. 513.
8. Randall, J.E., Allen, G.R. & R.C. Steene. 1997. Fishes of the Great Barrier Reef and Coral Sea. Crawford House Press. Pp. 557.