"Over-catch" (fouling) and pest species (oysters, barnacles, sea squirts, flatworms, mudworm) cost the Australian oyster industry an inestimable sum each year in grading and handling labour, product loss and reduced price due to unmarketable product. The pests are regionally specific, the issue is common across all growing areas and in all cases is a major financial burden. In NSW overcatch is currently treated through labour expensive heat treatment and stock management. The cost effectiveness of the alternate proposed treatment froms part of this proposal.

For example, oyster overcatch is one of the primary deterrents to interstate investment into Port Stephens, NSW which previously was a highly productive single species estuary. It is estimated that NSW production would be increased by 12.5% (GVP of almost $5m) through Marine Culture's use of a successful overcatch treatment in Port Stephens alone. Marine Culture propose to farm an output of 750,000 dozen Pacific Oysters off the area.

This project expands investigative research by NSW I&I (Heasman 2005) in which experimental, small scale cold shock trails “resulted in the death of advanced rock oyster over-catch in as little 5 seconds and complete mortality after exposure periods of 60 seconds and above. By contrast, no deaths nor discernable negative effects on the health and flesh condition of host Pacific oysters were detected for cold shock durations of up to 2 minutes”.

The project will include a more comprehensive range of oysters sizes and types, and fouling organisms. Further, and critically, the method needs to be assessed on a large scale under commercial operating environments to demonstrate practicality and cost effectiveness.

Marteiliosis (QX disease, aetiological agent the protozoan parasite marteilia sydneyi) typically causes serious, seasonally recurrent mortalities in farmed and wild rock oysters in eastern Australia. The disease is listed as notifiable by the OIE and is included on the Australian National List of Reportable Disease of Aquatic Animals.

The OIE has recently adopted the concept of zoning to facilitate trade and to prevent spread of disease within a country. In turn, Australia has recognised the value of zoning in its aquaculture industries with the adoption and endorsement of Zoning Policy Guidelines by Standing Committee on Fisheries and Aquaculture.

The establishment of scientifically defensible zoning and translocation policies, particularly in relation to QX disease control, is critical to the long term development of the rock oyster aquaculture industry. NSW Fisheries currently prohibits movement of oysters from known QX infected estuaries to those thought to be free of infection. However, given the many millions of rock oysters translocated annually between NSW estuaries of undetermined disease status, there is an urgent need to accurately identify free an infected zones. This, in turn, depends upon the availability of standardised, validated diagnostic tests.

Histopathology is currently viewed as the 'gold standard' for QX disease diagnosis, while preliminary comparative data (Callinan and Wesche, unpublished data) suggest that an alternative cytological method, stained tissue imprints of oyster digestive gland, has a sensitivity of 60% and specifically of 100%. Recently, however, there have been major advances in development of PCR tests for marteiliosis (Berthe et al. 2000; Kleeman and Adlard 2000). It is possible that PCR can be used to confirm presumptive/inconclusive diagnoses obtained by histopathology or cytology. PCR may also have potential as a cheap and reliable mass screening diagnostic test. In either event, however, rigorous standardisation and validation will be necessary before a PCR test can be accepted for use in zoning-related QX disease surveillance.