Report on the occurrence of Sydney rock oysters on the east coast of Tasmania

Several specimens of Sydney rock oysters ( Saccostrea glomerata ) were found by an oyster industry representative in the Prosser River at Orford and in the Little Swanport estuary in late 2014. These were identified by numerous bumps (teeth) on the margin of the upper internal valve near the hinge ligament, and were verified by DNA testing. These are the first records of Sydney rock oysters being found on the Tasmanian mainland; previously they had only been located as far south as Flinders Island. Further sampling was conducted in Georges Bay at St Helens where several Sydney rock oyster specimens were identified and again verified by DNA testing. This distribution of Sydney rock oysters suggests that the range of this species is extending south along the Tasmanian east coast, rather than specific introductions. However, no Sydney rock oysters were found from opportunistic sampling in the Leven River on the northwest coast or in North West Bay, southern Tasmania. Identification of Sydney rock oysters from Pacific oysters by external characteristics proved to be unreliable and either destructive sampling to examine internal features or DNA analysis is required.