It comes a week after the mysterious death of thousands of fish in the Port Stephens-Great Lakes marine park.

Commercial fisherman Neville Smith, who was involved in a survey around Mungo Brush and Dees Corner on Tuesday, estimated about half a tonne of dead fish was strewn along a kilometre of the shore.

"There were a lot of little fish, mostly bream, luderick and whiting," he said.

Many of the fish found last week had brown fungus growth around their mouths and gills, possibly the result of a weakened immune system.

Mr Smith said he and other fishermen had stopped fishing in the Myall Lakes due to concerns about the health of fish stocks.

"I've moved down to Port Stephens," he said.

"It just means there are more blokes working in another fishing area."

Recreational fisherman Andrew Sharp, who found hundreds of dead fish along the Myall Lakes shore last week, said he suspected some fish were also infected with red spot fungal disease.

"I was fishing at Corrie Island [on Monday]," he said.

"The bream had nasty lesions which seemed to be different to the fungus that the fish in the lake had on them."

Opinions among fishermen vary about what sparked last week's fish kill, but they include acid sulphate run-off from road works and agricultural sewage run-off.

Department of Primary Industry test results from dead fish collected from the shore last week are expected in coming days.

Great Lakes councillor Len Roberts has called for the creation of a single management authority for the Myall River.

No bans have been placed on fishing in the Myall Lakes.