The Department of Primary Industries is investigating a new outbreak of red spot disease in the Myall Lakes.
Ten bream caught on the Tea Gardens waterfront last week all showed signs of the fungal disease, which is associated with poor water quality.
"DPI is aware of reports of possible red spot affecting fish in the Myall Lakes. Aquatic biosecurity officers are taking samples from the area for testing to confirm the presence of the condition," a spokeswoman said.
"Healthy fish with no sign of red spot can still be caught and consumed by recreational fishers and caught and sold by licensed commercial fishers. Severely ulcerated fish should not be eaten."
In addition to red spot, blue green algae has been reported in the parts of the lakes.
The two conditions have raised further concerns about the health of the iconic waterway.
"The red spot is caused by low salinity. We have had a fair amount of rain that has contributed to this. There are other factors that can play a role and we are trying to determine what can be done," Myall River Action Group spokesman Gordon Grainger said.
Locals have been warning for months that the rapid build up of sand at the river entrance could cause it to close over, effectively choking the estuary.
The river's natural channel was dredged in 2015 and again in 2019.
While the dredging resulted in an improvement in water quality, it didn't take long before sand started building up again at the river mouth.
Locals are lobbying to have the river dredged every three years.
"We have a lot of support from within the council to dredge it more frequently but there is no money," Mr Grainger said.
Experts argue the river's hydro-dynamics are complex, however, it is widely agreed that a key part of the problem is sand sweeping back into the river from Jimmys Beach.
Ironically, the sand used to replenish the erosion hotspot, via a sand transfer system, is sourced from a stockpile of sand dredged from the river.
An historic sand spit known as Myall Point used to run out into Port Stephens and protect the river' entrance. The spit was swept away in 1929 but there is recent evidence that it is rebuilding.
"A three year dredge this time would greatly assist this process," Mr Grainger said.
Red Spot affects many species of fish and is reasonably common in NSW coastal catchments. Fish species known to be susceptible to the disease include bony bream, silver scat, sole, bream, mullet, whiting, dusky flathead, silver trevally, eels and catfish.
