Australia's sunny climate has been linked to high rates of skin cancer in humans but it now seems fish could also be susceptible.
Melanomas have been detected in wild fish populations for the first time in species on the Great Barrier Reef.
The most likely culprit is ultra-violet radiation, says lead researcher Michael Sweet from Britain's Newcastle University.
The university and the Australian Institute of Marine Science examined 136 coral trout caught at Heron Island and One Tree Island.
About 15 per cent had dark lesions on the surface of the skin, but were otherwise healthy.
