Bream and silver biddy carcasses from Bombah Broadwater were tested last week by Department of Primary Industry scientists, who found them riddled with the fungal infection Saprolegniosis, or winter disease.

“In winter disease, fungus can sometimes be seen around the mouth and gills, and appears as a brown deposit a bit like a five o’clock shadow,” a department spokesperson said.

The fish were widely thought to have red spot disease, which was found near Tea Gardens earlier this year, but the department said the Myall outbreak is different.

Fish veterinarian Matt Landof said it was unusual for estuarine fish to contract winter disease. The fungus choking the fish can be found even in healthy waterways, but it can be devastating.

“It’s a common water fungus, but if the water gets cold very quickly it affects fishes’ immunity. Their skin and gills become vulnerable to it,” Dr Landof said.

“Water with low salinity also allows the fungus to thrive.”

Fishing has not been banned in the lakes, but the department warned that fish with tell-tale brown residue around the mouth and gills should not be eaten. Dr Landof agreed.

“If an adult fish with the disease was cooked and eaten there would be no impact [on the human], but I wouldn’t recommend eating a fish that shows signs of illness.”

A Department of Environment and Climate Change (DECC) spokesperson said experts were satisfied enough water passes through the Myall River mouth to keep it clean, but two Great Lakes councillors said the current outbreak is a symptom of mismanagement.

“Comments by the DECC that there’s sufficient flow to allow flushing are contrary to current reports and council’s own submission to dredge the opening,” Cr Len Roberts said.

Some fishermen shrugged off the outbreak, which they say is fairly common.

“It’s been going on for years,” lakes-based commercial fisherman Graeme Hockings told the Myall Coast Nota.