Hawks Nest Sports Store owner, Stewart Patterson said more and more holiday-makers, weekenders and locals have told him they’ve caught mainly bream and flathead with red lesions and ulcers.

“One fella I knew caught six with red spot – that’s a 100 per cent catch rate. No one seems to know what’s going on and it’s a big worry.”

A spokesperson for the DPI said the cases are “reasonably common” and usually clear up on their own.

“The department will continue monitoring the Myall Lakes and other nearby waterways with the help of commercial and recreational fishers where red spot is suspected.”

But Mr Patterson said the health and safety of fishers must be considered.

“I say to tourists “look you may not be aware but there are fish with red spot in the river” just to alert them,” he said.

“There should be signs around to warn people that if a fish is caught with a spot on it to either kill it or throw it away. You’ve got to worry about people’s heath.”

The department said severely ulcerated fish should not be eaten or thrown back into the river, but disposed to landfill.