Reef to revive native oyster in Australia

By / 3rd of July, 2017
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WORK has begun on the biggest oyster reef restoration project out side of the United States.

The 20 hectare (50 acre) reef in the waters of Gulf St Vincent in South Australia is the first of what is hoped to be five major reef projects in the state to revive wild populations of the almost extinct native mud oyster, Ostrea angasi.

The project just off the coast of South Australia’s Yorke Peninsula also aims to increase fish stocks for recreational anglers and improve water quality and biodiversity in the Gulf.

The first of 60 one-tonne concrete reef structures and more than 800 tonnes of limestone have started being sunk at the site. About 7 million native baby oysters will then be planted on the reef to further attract fish and help revive the almost extinct wild oyster species.

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Concrete structures and limestone being lowered into the water at the reef site in Gulf St Vincent. Picture: Anita Nedosyko, The Nature Conservancy. 

The original reef was to be 4ha in size but additional funding from the Australian Government, The Nature Conservancy, Yorke Peninsula Council and the University of Adelaide will allow it to be extended to 20ha over the next few years, making it the largest shellfish restoration project outside of the United States.

The first 4ha of the project is being delivered by the South Australian Department of Primary Industries and Regions (PIRSA) and is expected to be opened to recreational anglers before the end of the year.

Diving will be allowed on the reef but the taking of oysters prohibited. The 4ha reef will be closed to commercial fishing permanently, however, the fishing rules for the remainder of the 20ha reef are yet to be determined.

Oyster reefs are considered the temperate water equivalent to coral reefs in tropical waters. Australia’s southern coastline was home to thousands of kilometres of oyster reefs before European settlement but dredging practices to remove the oysters for food and substrate for lime production wiped out all the reefs except for one off the coast of Tasmania.

The Nature Conservancy has been involved in dozens of shellfish reef restoration projects, chiefly in the United States and is considered a global expert on their establishment.

TNC Project Officer Anita Nedosyko said a six-year study on the reef would measure the environmental benefits on water quality, fish production and seagrass regeneration.

She said each oyster could filter more than 100 litres of water a day, removing harmful nutrients and turning them into pseudofaeces, which becomes a food source for bay fish and crustaceans.

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“We see the Yorke Peninsula reef as just the beginning and what The Nature Conservancy would like to see is a similar-sized reef at five different locations across South Australia,” Nedosyko said.

“This is a really innovative fisheries management approach which seeks to bring back important habitat for commercial and recreational fish species.”

University of Adelaide School of Biological Sciences researcher Dominic McAfee said if successful, the reef would be home to hundreds of million or billions of native oysters.

“What people need to appreciate is that 20ha is hugely ambitious and oysters take a while to grow and mature so it will be a while before we see substantial populations that are self-recruiting,” Dr McAfee said.

“The realisation that we’ve lost the spatial equivalent of the Great Barrier Reef but in oyster reefs and the capacity to rebuild them is very new in Australia

“This is going to provide a sharp and necessary learning curve but we expect that if it’s successful, it will lead to many more reefs.”

It is hoped the reef will become a breeding ground to help improve the stocks of many species including King George whiting, snapper, garfish, squid and blue swimmer crabs.

Peak body RecFish SA began lobbying for an artificial reef in 2013.

RecFish SA Executive Officer Danny Simpson said had been an excellent decision to evolve the project from a strictly artificial reef to include the native oysters.

“We’re very confident that this is going to be of great benefit to recreational fishing,” Simpson said.

“The technical organisations involved in the design and deployment of the reef are very skilled and where they’ve done these things before it’s proven to be tremendous for boosting fish stocks and benefitting rec fishing.

“We know that many fish stocks are under pressure and if the reef contributes to improving those stocks then it is doing a fantastic job.”

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The lifecycle of native oysters on the reef. Courtesy The Nature Conservancy.

PIRSA Fisheries Enhancement Program Leader Sarah-Lena Reinhold said 50 per cent of tourists to Yorke Peninsula visited specifically for recreational fishing.

She said it was expected to take about two years for the reef to be colonised to the point where additional fish production was noticeable.

“It’s a huge win and it’s a proactive way of enhancing fishing opportunities in a really sustainable way and bringing back the habitat that previously supported all those species,” Reinhold said.

“It’s really putting a light on South Australia and the Yorke Peninsula region and it’s going to be a real asset to everybody in that area as well as people who want to visit.”