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Farming Sydney Rock Oysters

The oyster industry in 2007/2008 was worth $41 million, oyster farming has been the most valuable aquaculture industry in New South Wales for over 100 years. Sydney rock oysters make up 94% of edible oyster production in New South Wales, small amounts of Pacific and native flat oysters are also grown. In recent years annual production has stabilized at almost 100 million oysters

.Around 75% of all oysters grown in NSW are sold within the State, the remaining oysters are sold in other states. Less than 1% were exported in 2000-01.

The industry is the fourth largest aquaculture industry in Australia, behind the bluefin tuna aquaculture industry, the pearl aquaculture industry and the Tasmanian salmon aquaculture industry.

Oysters are grown in 41 estuaries of rivers from the NSW Victoria border to the NSW Queensland border except for around the Sydney area. There are 380 oyster aquaculture permit holders that hold between themover 3,000 aquaculture leases, with a total area of about 3,100 hectares of submerged Crown land. The leases are administered by NSW DPI.

There are strict environmental management controls in place to ensure that environmental degradation and problems with disease are minimised. Shellfish sanitation programs have also been set up to increase consumer confidence in oysters.

There are two main farming methods used in New South Wales - stick farming and tray type farming.

An oyster farm in NSW

Where Sydney Rock Oysters are grown

Stick farming

This method has been the mainstay of the industry since the 1930's and commences with oyster larvae settling on hardwood sticks 1.8 metres long and 25 mm square covered with tar. These are placed in areas of estuaries where the settling of spat is most reliable, typically near river mouths.

The sticks are then moved to areas with few spat to prevent too many settling on the sticks and are grown to maturity on horizontal racks. The process takes from 3 to 4 years with great care needed in the first two years to protect the oysters from high temperatures and predators. The oysters are then removed from the sticks and graded into various sizes before marketing.

At harvest, oysters not large enough to be sold as ‘large’ (15–25 oysters per kilogram), or as ‘bistro’ or ‘bottle’ oysters (25– 35 oysters per kilogram) are usually placed on trays and returned to the same or other estuaries to develop to a marketable size.

Tray farming

Oyster trays are usually one metre wide and from 1.8 - 2.7 metres long, made from timber and wire or plastic. Trays are more portable, easier to manage and allow precise stocking densities to encourage oysters to grow in a more uniform and marketable shape.

Single seed farming

In this new method, oyster farmers remove oyster spat from the catching surface ( sticks or PVC slats) very soon after settlement when the oysters are still only 3to 8 mm in diameter. The spat are then either placed on specially constructed trays or in newly developed plastic mesh cylinders or baskets.

These methods provide excellent protection from predators and the early removal of the stick prevents oysters becoming misshapen or clumped together. Faster growth rates have also been reported. Whilst single seed techniques have a large setup cost faster growing, better shaped oysters generally allow more precise grading into sizes and the oysters usually can be sold for higher prices.

Research is being carried out to produce breeds of oysters that grow faster, have better disease resistance, and can be marketed in the off season.