Quest to reintroduce native oysters to Narooma's sapphire waters

On a quiet Thursday afternoon without fuss or fanfare, natural resource management officer James Caffery and oyster farmer Damon Fernihough, and a small band of volunteers, undertook the task of placing an estimated 600,000 bagged infant oysters into the water.

Last year, in a similar way, approximately two million oyster larvae were settled on to clean oyster shells before being placed on a newly reconstructed oyster reef in the inlet.

The predation rate of the young oysters was high, so this year the team have kept them longer in the hatchery tanks. Damon said this was one of the steps they were taking to "mitigate their vulnerability".

"Once they reach a certain size they are pretty much able to hold up to fish predation - which is the main predator for baby oysters," he said.

"So once we get them to a certain size they should be able to take care of themselves."

James had taken six tagged oyster shells from each tank and placed them beneath a microscope, to obtain an idea of how many larvae had settled on each shell. From here the team can estimate how many potential oysters they are returning to the inlet.

The oyster shells were contained in netted bags inside the tank, and would remain in the bags for a period in the waters of Wagonga Inlet, before spreading them out across the reef.

With James' estimations complete, the 68 netted bags were carefully transported to the water's edge from the purpose built tent on the shoreline housing the four tanks. From here they were placed in batches on Damon's punt and taken out to designated spots for immersion.

Angasi oysters are functionally extinct, meaning a small population survives and breeds but they do not contribute to the ecosystem as they should.

James explained that due to the high concentration of lime in the large, thick shells of the Angasi, they were dredged for the production of concrete in the late 1800s and early 1900s.

"Because they are not as attached to the substrate as say a Sydney rock oyster was, and because they were so much bigger, they would dredge them and literally just pull out whole populations, whole reefs, and then not even use the meat the majority of the time," he said.

"They just mined them - they just crushed it straight up and put it in the concrete mix."

The program is part of the larger Wagonga Inlet Living Shoreline project that has seen 17,500 saltmarsh and terrestrial plants reintroduced to the regraded shoreline and the construction of an intertidal and a subtidal reef.

Public infrastructure will be returned to the stretch of shoreline, including a boardwalk, a jetty and educational signage. Indigenous art and sculpture will also feature.

Although the mortality rate is expected to be high, James says this is natural. The divers from the Joonga Land and Water Aboriginal Corporation will monitor the population and measure its success as best they can.

"We will definitely see some rates of success this year," said James

"Give this project two or three years and go for a snorkel down there, you will see a flourishing ecosystem that has so many other little animals down there that we didn't restore - that came in naturally.

"Give it a few years and it will look like what a reef actually should look like, and give it 10 years and it will be completely full I reckon."

Project partners include The Nature Conservancy, Department of Primary Industries - Fisheries and Eurobodalla Shire Council.