I&I NSW work to uncover facts about oyster winter mortality

Industry & Investment NSW researchers at the Elizabeth Macarthur Agricultural Institute (EMAI) and the Port Stephens Fisheries Institute are working to find the cause of a disease that has impacted many oyster farms along the NSW coast.

EMAI research scientist, Dr Cheryl Jenkins, said the project aimed to find the cause of the Winter Mortality Syndrome which impacts Sydney rock oysters in estuaries south of Port Stephens.

“Winter Mortality Syndrome is responsible for significant losses of Sydney rock oysters each year, however very little is know about the disease,” Dr Jenkins said.

“The disease is considered to be associated with a protozoal parasite called Bonamia roughleyi, however recent research at EMAI suggests this may not be the case.

“It appears the disease is more severe in oysters that are farmed below the standard growing height in an estuary and has also been linked with higher salinity levels.

“While affected oyster farmers undertake some preventative measures against Winter Mortality Syndrome including moving oyster stocks to upstream leases where water is less saline and purchasing Sydney rock oysters that have a higher level of resistance to the disease, there are no treatments available.

“We are hopeful this research will give us a better understanding of Winter Mortality Syndrome and confirm whether a protozoal parasite is the cause."

The Hermon Slade Foundation, an organisation set up to encourage the pursuit of excellence in scientific research, will contribute $23,000 towards the project. I&I NSW is also investing $45,000 towards the collaborative research project.

Port Stephens Fisheries Institute researcher, Dr Wayne O’Connor, said a study is underway that aims to collect oyster samples over the entire Winter Mortality season in two estuaries where the disease regularly occurs.

“We are working with oyster farmers in the Shoalhaven River and the Georges River to collect samples for laboratory testing at EMAI every three weeks to monitor for the presence of protozoal parasites and signs of disease.” Dr O’Connor said.

Finding out more about Winter Mortality Syndrome will allow us to make better recommendations on improved biosecurity measures that will minimise the impact of the disease on commercial oyster production and marine ecosystems.”