These species called coral trout, found on Australia's Great Barrier Reef, were brought to the attention of Dr.Michael Sweet at the University of Newcastle in the UK last year.
Dr.Sweet and his colleagues after a collaborative study ruled out the speculations of any fungal disease and said that the black scars, which look like human melanomas, are in fact the symptoms of skin cancer. Of the 136 fish sampled, 20 (15%) showed dark lesions on the skin .
Source: New Scientist
Image Source: MSNBC