Summary

The Sydney rock oyster is considered a gourmet's delight and is the mainstay of the oyster industry in New South Wales. Since 1990, production has averaged 8 million dozen oysters per annum and has been worth around $30 million. Oyster farming is the oldest aquaculture industry in NSW and has been a valuable contributor to regional economies of the state for over 100 years.

Unfortunately, like other farm animals such as cattle, sheep, pigs, poultry and fish, oysters also suffer from diseases. Just like in other farm animals, there is an interaction between the environment and disease and oyster farmers can modify their farming practices to minimise both the incidence and impact of some diseases. The practice of 'highway oyster farming', which involves transferring oysters between estuaries for on-growing, was established during the 1960's and increases the risk of spreading diseases.

Sydney rock oysters suffer from two protozoan diseases called 'winter mortality' and 'QX'. The effects of winter mortality can be greatly reduced by sound farm management and oyster husbandry practices. However, this is not the case for QX disease. It needs tight quarantine regulations to avoid spread of this parasite. Fortunately, breeding and selection for resistance against QX disease is making excellent progress. Mortality from two other diseases, mudworm and flatworm can to a large extent be minimised by good farm management and oyster husbandry practices.