Bishop, M., Krassoi, R., McPherson, R., Brown, K., Summerhayes, S., Wilkie, E. and O’Connor, W., 2010. Does aquaculture of non-native species facilitate biological invasion? Presentation given at the Australian Marine Science Association. Conference, 4 – 8 July 2010, Wollongong, New South Wales, Australia.

Summary

The spread of a species introduced for aquaculture to the natural environment can threaten native ecosystems. Following the introduction of Pacific oysters, Crassostrea gigas, to Port Stephens, NSW, Australia, and the later (1991) decision to permit their culture, we assessed whether Pacific oysters had spread and overgrown the native Sydney rock oyster, Saccostrea glomerata. Sampling of seven rocky-shore and four mangrove sites in Port Stephens immediately before aquaculture of Pacific oysters was allowed (1990), immediately after culture began (1991–1992) and nearly two decades later (2008) did not find evidence of further Pacific oyster spread or that overgrowth of Sydney rock oysters had occurred. The non-native oyster, relatively uncommon immediately before the start of aquaculture, remained confined to the inner port of Port Stephens and its percentage contribution to oyster populations generally declined over the two decades. Pacific oyster populations were dominated by small individuals of < 40-mm shell height, with established adults being rare. Only at one site did Pacific oysters increase in abundance and the number of Sydney rock oysters declined. The failure to see the catastrophic changes in oyster communities seen elsewhere in the world could reflect factors such as estuarine water circulation patterns that restrict the spread of Pacific oyster larvae and the susceptibility of Pacific oysters to existing native predators (fish, crabs and birds).