Aquatic Invasions (2016) Volume 11, Issue 4: 425–436 DOI: http://dx.doi.org/10.3391/ai.2016.11.4.07 Open Access © 2016 The Author(s). Journal compilation © 2016 REABIC Research Article Quantifying abundance and distribution of native and invasive oysters in an urbanised estuary Elliot Scanes1,2,*, Emma L. Johnston3,4, Victoria J. Cole1,2, Wayne A. O’Connor5, Laura M. Parker1 and Pauline M. Ross1,2 1School of Life and Environmental Sciences, Coastal and Marine Ecosystems Group, The University of Sydney, Sydney, NSW 2006, Australia 2 School of Science and Health, Western Sydney University, Penrith, Sydney NSW 2750, Australia 3School of Biological, Earth and Environmental Sciences, Evolution and Ecology Research Centre, The University of New South Wales, Sydney, NSW 2052, Australia 4Sydney Institute of Marine Science, Mosman, NSW 2088, Australia 5New South Wales Department of Primary Industries, Port Stephens Fisheries Institute, Taylors Beach, NSW 2316, Australia *Corresponding author E-mail:
[email protected] Received: 9 January 2016 / Accepted: 2 August 2016 / Published online: 25 August 2016 Handling editor: Darren Yeo Abstract Human activities have modified the chemical, physical and biological attributes of many of the world’s estuaries. Natural foreshores have been replaced by artificial habitats and non-indigenous species have been introduced by shipping, aquaculture, and as ornamental pets. In south east Australia, the native Sydney rock oyster Saccostrea glomerata is threatened by pollution, disease and competition from the invasive Pacific oyster Crassostrea gigas. This study assessed the abundance (as number m-2), size, and distribution of both invasive and native oyster species at 32 sites in the heavily urbanised Port Jackson Estuary, Australia.