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Reefs to boost oyster growth along island's north

A series of small-scale reefs has been established along a section of the South Australian coastline in an innovative project to establish healthy colonies of native angasi oysters.

The reefs along Kangaroo Island's north coast will be seeded during autumn with spats, baby angasi oysters caught from the island's bays.

They have been constructed from limestone, oyster shells, terracotta tiles and timber to provide environments similar to those found in the wild.

Also being used are 1000 ceramic forms, crafted to mimic the shape of razorfish shells, a popular habitat for a variety of marine life.

Kangaroo Island Landscape Board project officer Alex Comino said angasi oysters surrounding Kangaroo Island released millions of larvae into the water.

"These larvae drift in the tides and seek out suitable hard areas of seabed to settle and grow," she said.

"Sadly, many of these larvae do not survive due to natural predation and the lack of suitable substrate to colonise."

Angasi oyster reefs were once common along the southern coast of Australia but were over-harvested in the late 1800s to the point where only a few pockets of native oysters still exist.

Ms Comino said the new reefs would also provide important habitat for recreational and threatened fish species, such as King George whiting and southern calamari, pipefish and seadragons, with access from both Kingscote and American River boat ramps.

"At the same time, they will restore exploited native flat oyster reefs by providing a structure for angasi oysters to settle on and grow," she said.

"It's hoped that once the oyster reefs are seeded and established, they will continue to grow as native oysters are extremely gregarious, meaning they actively seek out habitats where other oysters live during the larval stage before settlement.

"The successful techniques may then be scaled up in the future."