The Australian Farmed Oyster Industry

Oysters are farmed in Tasmania, South Australia and New South Wales with the three species grown being Sydney Rock Oysters, Pacific Oysters and Native Oysters. Oysters are not only delicious, they are also one of the most nutritionally balanced food available. They contain protein, lipids and carbohydrates. It has also been suggested that oysters are an ideal food for inclusion in low-cholestrol diets. Oysters are an excellent source of vitamins A, B1 (thiamin), B2 (riboflavin), B3 (niacin), C (ascorbic acid) and D (calciferol). Four or five medium sized oysters will supply the recommended daily allowance of iron, copper, iodine, magnesium, calcium, zinc, manganese and phosphorus.

The history of oyster farming is well documented in this link: www.findarticles.com/p/articles/mi_m3089/is_3_63/ai_100732740

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Oyster Growing in South Australia

The South Australian Oyster industry was established in the late 1980's with the South Australian oyster industry now consisting of seven growing regions which pride themselves on producing a premium product for both domestic and international consumers. The primary oyster growing regions are Coffin Bay, Streaky Bay (Haslam), Cowell (Franklin Harbour), Kangaroo Island, Yorke Peninsula (Stansbury and Port Broughton), Louth Bay and Smoky Bay.

The oyster industry is the second largest aquaculture sector in South Australia producing almost 3.5 million dozen oysters in 2001/02, valued at over $A14.1M.

South Australian oysters are grown using several methods, on traditional rack and rail systems, the unique South Australian BST longline system or hybrid systems that suit particular growing areas. Culturing systems differ from bay to bay and are developed to allow oysters the greatest access to food to ensure that the optimum meat to shell ratio is obtained and quality assured.

Oysters are graded several times before they are sold to minimise parasite settlement & maximise growth opportunities. South Australian oysters are sold as Bistros, Plates, Standards, Large or Jumbos. The growout time varies with size, but usually takes between 18-30 months.

Information taken from www.oystersa.com.au/saorc and www.pir.sa.gov.au/aquaculture/aquaculture_industry/oysters

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Oyster Growing in Tasmania

The Tasmanian oyster industry is based primarily on the Pacific Oyster with the growing-out of hatchery spat on licensed marine farms. Oysters are grown at various sites around the north and east coasts of Tasmania, from the Smithton region through to the southern part of the D’Entrecasteaux Channel, south of Hobart.

Tasmanian oysters are sold in three forms: fresh unopened (by far the most common form), fresh opened and frozen opened. Most growers sell their own oysters unopened in 50kg bags. The unopened oysters are sent by chilled road freight. Because of their shorter shelf life, processed (opened) fresh oysters need to be sent by airfreight.

The majority of Tasmanian oysters are still distributed to domestic markets. Historically Victoria was the main market for Tasmanian oysters but other states are also now taking an increased share of Tasmania's production. In 2002-2003, exports to Japan increased in the frozen half-shell form.

Information taken from www.tasea.com.au

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Oyster Growing in New South Wales

Pacific Oysters have been commercially cultivated in Port Stephens since 1991, but are declared a noxious fish in other New South Wales waters. In 2001-02, production of Pacific Oysters in New South Wales was 444,000 dozen, valued at $A1.95 million.

Commercial production of the Sydney Rock Oyster occurs in 41 marine estuaries and bays between Eden and Tweed Heads. The main production areas are at Wallis Lake and the Hawkesbury River, which are in the East-central Marine Region.

Information taken from www.australian-aquacultureportal.com/industrygroups/oysters_pacific.html

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Pacific Oysters

The Pacific Oyster Crassostrea gigaswas introduced from Japan for aquaculture and supports a thriving industry in Tasmania. It is cultivated in intertidal and subtidal conditions, from estuarine to fully marine areas. It attains a maximum size of 250 mm, although most product is sold at 60-85 mm size.

After opening, the size of an oyster is measured by the length of the flat (top) shell. It takes an average of two years to grow an oyster to the Buffet size, with an additional eighteen months to two years to reach Jumbo size.

This information was taken from www.tasea.com.au but more detailed information on the Pacific Oyster can be found at www.fish.gov.au

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The Native Oyster

The Native Oyster Ostrea angasi grows wild in Tasmania, although they also occur across southern Australia. They have thick shells, growing to a maximum size of 180mm. Native Oysters are harvested from sandy or silty seafloors in deep water around the Tasmanian coastline. Native Oysters have a reputation for their distinctive, full-bodied taste but have a stronger flavour than Pacific Oysters.

More detailed information on the Native Oyster can be found at www.fish.gov.au

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The Sydney Rock Oyster

The Sydney Rock Oyster Saccostrea glomerata are endemic to Australia, and are found in bays, inlets and sheltered estuaries from Hervey Bay in Queensland to Wingan Inlet in Eastern Victoria.

They have a thick shell with a smooth exterier surface. There are hinge teeth on the inner margin of their upper shell. The mantle edges and adductor muscle scar are pale coloured.

Sydney Rock Oysters are capable of tolerating a wide range of salinities. They are usually found in the intertidal zone to 3 metres below the low water mark.

Sydney Rock Oysters are "broadcast spawners" that is eggs and sperm are released into open water where fertilisation occurs. Within hours of fertilisation the eggs develop into free swimming planktonic larvae. The larvae swim in esturine and coastal waters for up to three weeks during which time they develop transparent shells and a retractable foot. The larvae then settle on a clean substrate using the foot to find a suitable site. The foot is reabsorbed once the larva is attached. The shell darkens and the small animal takes on the appearance of an adult oyster.

Growth rates vary with local conditions. Sydney Rock Oysters generally reach 40-60g in 2 - 3 years. Sydney Rock Oysters also change sex during life. They start out as males and later change to females. About 75% of prime eating oysters are female.

Oysters are filter feeders, straining planktonic algae from the water. They are prey to a variety of fish, including stingrays, mud crabs, whelks and starfish.

There is no commercial harvesting of wild Sydney Rock Oysters. All commercial stocks are farmed.

Information was provided by www.sea-ex.com/fishphotos/oyster and more detailed information can be found at www.fish.gov.au

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