Reviving the oyster lover’s oyster

Flinders University PhD candidate Yibing Liu (pictured) is working with Marine Innovation Southern Australia (MISA) scientists to help South Australian oyster growers revive the culture of the native or flat oyster, Ostrea angasi.

A trial to address hatchery issues and growing techniques involving up to three million oyster spat is being conducted at SARDI Aquatic Sciences, West Beach, over the next few months.

Known as the oyster lover’s oyster, the native oyster can command twice the price of the introduced Pacific oyster, Crassostrea gigas, which is now commonly grown on oyster leases along the South Australian coastline, mainly on Eyre Peninsula.

MISA scientist, Professor Xiaoxu Li, says native oyster farming could become another major aquaculture sector in the next five to ten years.

“The native oyster, which is considered a delicacy and is highly nutritious, was the first substantial fishery in South Australia, having been exploited from the mid-1800s,” says Professor Li.

The industry collapsed around the 1880s primarily due to overfishing, and subsequent attempts to recover this valuable resource were hindered due to poor spat survival.

Professor Li and Mr Liu are using local broodstock to assess the best hatchery methods to help build the industry.

Under natural conditions, the female native oysters look after their progenies inside their shells and release them as free swimming larvae into the water column when they are about a week old. The larvae further develop and then metamorphose into spat and settle on the substrate.

In this project, the progenies of different ages, from a few hours to a week old, are collected from the females directly, and then reared in 2000 litre round tanks and fed a mixture of four microalgae species.

The microalgae are about five to ten micron (one-thousandth of a millimetre) in diameter, and so tiny that they have to be counted under a microscope. The microalgae are being produced in SARDI’s Algal Culture Room in plastic bags where they receive balanced light, nutrients and carbon dioxide to promote fast growth and good nutritional quality. The microalgae in the bags are being maintained at a density of up to ten million cells per millilitre.

Professor Li says that initial hatchery trials last year achieved survival rates of at least 70 per cent from early stage larvae to metamorphosis, providing around one million spat to oyster farmers to trial in the field.

“This year’s embryo survival rates have greatly improved, and we now aim to evaluate native oyster performance across a greater range of environmental conditions in South Australia,” says Professor Li.

MISA, an initiative of the Government of South Australia established in 2005, is a partnership between the South Australian Research and Development Institute, Flinders University, the University of Adelaide, the South Australian Museum, the Department of Environment, Water and Natural Resources, Primary Industries and Regions SA and the SA seafood industry.

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