Find a Fish
Numbfish
Hypnos monopterygium (Shaw & Nodder, 1795)
I found this animal washed up on the beach (Umina Beach - Central Coast) about 1 month ago. I haven't seen anything like it, in books or film. It seemed to resemble a stingray, though it was only about 45cm head to tail.
I'm sorry I ran out of film to take more pictures. The animal, although it had been ripped open, was entire. It had well formed "lips", a small mouth and a tiny tail about 5-10cm long.
It appeared to have eaten a rodent which was undigested and encase in the "intestine". I can't think how it swallowed such a rodent through its small mouth, or did the rodent get into it after it was caught by a fishing trawler etc. (there was a trawler operating off the beach, as usual, this day.)This animal was about 5cm thick. Its backbone had torn through its back.
I'm intrigued as to its identity. I hope you can help.
Thanks,
Cilla Johnstone.
The fish is known as Numbfish or Coffin Ray, Hypnos monopterygium, family Hypnidae. It is a type of electric ray that is well known to divers who occasionally get quite a jolt when they kneel on this fish buried in the sand. The Numbfish is one of eight Australian rays which are known for their ability to produce electric shocks. A powerful electric shock is produced from large kidney-shaped organs in both pectoral fins, and is believed to startle potential predators and to stun prey.
The Numbfish is only found in Australia, and occurs from southern Queensland to southern New South Wales and from north-western Western Australia to St Vincents Gulf in South Australia.
We were initially somewhat skeptical about the rat in the gut of the fish. Ms Johnstone however stated that it definitely was a hairy rodent and pointed out that in one of the images you can see a foot protruding from the gut of the Numbfish. The enlarged image above clearly shows this. Numbfishes have small mouths and normally eat crabs, worms and small fishes which are stunned and eaten whole. Why this fish has a dead rat in its gut is unknown.
View the Numbfish fact sheet.
Follow-up letter from C. Henderson on Numbfish feeding.
Letter from S. McMahon on Numbfish that had eaten penguins.
Further reading
- Last, P.R. & J.D. Stevens. 1994 Sharks and Rays of Australia. CSIRO. Pp 513
