Concerned Lake Conjola residents found hundreds of dead fish on the shoreline on Tuesday.
The discovery of hundreds of dead mullet and whiting in the lake, near Cunjurong Point boat ramp, follow the lake’s closure in recent weeks.
Residents speculated dredging that did not mimic the natural flow of the waterway was to blame for the fish deaths.
The Department of Primary Industries has been contacted for comment.
The lake was dredged in early 2016, but has since closed to the ocean again. Conjola Community Association publicity officer Kristen Bird said finding the dead fish was “sad”.
“It is another natural disaster because of the condition of the lake entrance,” she said. “It looks a bit third world.
“It happened last time it was closed before they dredged it with sea rays and they all died. It is affecting the fish in the lake when the lake is closed, obviously.”
Ms Bird said the natural causeway of the lake needed to be “scoured” regularly.
“Because of various weather phenomenons, it has needed some assistance and I don’t think the assistance that has been given in recent times was correct,” she said.
“The lake needs assistance to re-find its natural causeway, but I am not sure a one-off dredging is the answer."Kristen Bird
“I think an ongoing scouring to help it find it’s natural causeway is the answer.
“The most recent dredging lasted about two summers, and it did give the lake a good flushing out, but it was never going to last because they went a way the lake doesn’t naturally flow. They dredged along the northern shoreline, but the lake flows more to the southern shoreline.”
Association vice president Dirk Trelor said dredging in 1999 lasted 13 years.
“Dredging needs to go with the natural channel,” he said.
“The key for the channel location is for it to be on the southern side so on the outgoing tide, it transports sand back out through the entrance.
“It is about monitoring it and doing something, rather than doing nothing. The council has to be more open to working with the natural flow of the lake.”
Data states 40,000 cubic metres of sand comes in and 30,000 cubic metres goes out annually, leaving a surplus of 10,000 cubic metres.
The Department of Primary Industries has been contacted for comment on the issue.