Fish with skin cancer discovered for first time

Skin cancer in wild marine fish has been discovered for the first time, new research has revealed.

The study, conducted by Newcastle University and the Australian Institute of Marine Science, found cases of melanoma in coral trout on the Great Barrier Reef, directly below the world's largest hole in the ozone layer.

The research team, led by Newcastle University's Dr Michael Sweet, said this is the first time cancer has been found in wild fish and it is almost identical to that found in humans.

Dr Sweet said: "The individuals we looked at had extensive surface melanomas, which means the cancer had not spread any deeper than the skin so apart from the surface lesions the fish were basically healthy.

"Further work needs to be carried out to establish the exact cause of the cancer but having eliminated other likely factors such as microbial pathogens and marine pollution, UV radiation appears to be the likely cause."

"Once the cancer spreads further you would expect the fish to become quite sick, becoming less active and possibly feeding less, hence less likely to be caught.

"This suggests the actual percentage affected by the cancer is likely to be higher than observed in this study."

The research found of the 136 coral trout sampled, 15% showed dark lesions on the skin. This ranged from covering as little as 5% of the skin to an almost entirely black appearance.

Dr Sweet said: "Now it's been found it's more than likely that people will start to notice it elsewhere and we think we have only found the early stages.

"The fish with the later stages might well suffer from big behaviour changes, for example they could be eaten by predators or simply die.

"The findings are strongly linked to UV and it's too much of a coincidence for it not to be linked to the hole in the ozone layer."

Up until this discovery by the experts from Newcastle University, the Australian Institute of Marine Science and James Cook University, Australia, UV-induced melanoma in fish had only been seen under laboratory conditions.

Dr Michelle Heupel from the Australian Institute of Marine Science stated: "This is a crucial finding in an iconic and high value reef species.

"Given climate change scenarios and continuing alteration of coral reef environments understanding the cause of this disease is important to continued conservation and management of reefs and their inhabitants."

The coral trout itself is an important species that is found throughout the western Pacific and in Australia supports a large fishery on the Great Barrier Reef.

The fish caught for the study came from two locations, Heron Island and One Tree Island, both in the southern Great Barrier Reef Marine Park.

It is expected that the next step in the study will be to look at a much larger sample and determine to what extent the disease is present and the causes of it.

PA