In 2018, Associate Professor Greg Skilleter from the University of Queensland led a team revisiting four sites along the length of the estuary, that he first took dozens of samples from back in 1998.

The results revealed up to a 65 per cent decline of benthic species in that 20 years — the tiny worms, snails clams and crustaceans that live in the mud and sand, providing food for fish and crabs targeted by commercial and recreational fishers.

“We found that there is between a 30 to 65 per cent loss of [benthic] species along the system, but it’s worse than that because the numbers of these animals have crashed also — a lot of the species that were found, we only found one or two individuals in the whole system,” Skilleter said.

“They’re probably not viable populations anymore, so even though the species itself might not have disappeared it is probably getting close to local extinction because the numbers are so small.”

Bring Back the Fish

The study is part of the Bring Back the Fish research program, a $1.4-million co-funded research effort that is a joint initiative of the Noosa Biosphere Reserve Foundation (NBRF), Noosa Parks Association and The Thomas Foundation.

NBRF chair, Rex Halverson, said many people had been misled by the A- water quality rating the Noosa River received, which was amongst the best in Queensland.

“That does not cover everything that might be of concern, especially biodiversity,” Halverson said.

“It doesn’t take a rocket scientist to figure out if we’ve lost a lot of the fish food source that has to have implications on the fish populations as well.”

He said the biodiversity in the Noosa River System study was the third component of Bring Back the Fish, in conjunction with Keep it in Kin Kin sediment mitigation projects and the Oyster Reef Restoration Pilot Study.

Skilleter said he would be recommending that council take action to release the sediment.

“They need to start thinking about a periodic forced opening of the river mouth, probably corresponding with a heavy rainfall event,” he said.

“We did a study for council 20 years ago, which was looking at the impacts of dredging in the mouth of the Noosa River, and we actually showed that, yes, there are definite effects from that — but the system recovers and those effects are actually on par with a flood event.”

Noosa Councillor, Tom Wegener, said ratepayers helped fund the research through the environment levy and future decisions would be based on science.

“That [dredging the river mouth] would be very controversial,” he said.

“This is a serious situation— we really want to get the river up to where it should be, we’ve messed with the river over the years.”

– ABC / Jennifer Nichols