Change in wild-oyster assemblages of Port Stephens, NSW, Australia, since commencement of non-native Pacific oyster (Crassostrea gigas) aquaculture
Melanie J. Bishop A F , Fredrick R. Krassoi B C , Ross G. McPherson B D , Kenneth R. Brown B , Stephen A. Summerhayes B , Emma M. Wilkie A and Wayne A. O’Connor EA Department of Biological Sciences, Macquarie University, NSW 2109, Australia.
B Department of Environmental Science, University of Technology Sydney, Broadway, NSW 2007, Australia.
C Ecotox Services Australasia Pty Ltd, 27/2 Chaplin Drive, Lane Cove, NSW 2066, Australia.
D Environment Division, Hornsby Shire Council, Hornsby, NSW 2077, Australia.
E Port Stephens Research Centre, Industry and Investment NSW, Taylors Beach, NSW 2316, Australia.
F Corresponding author. Email: mbishop@bio.mq.edu.au
Marine and Freshwater Research 61(6) 714-723 https://doi.org/10.1071/MF09177
Submitted: 10 July 2009 Accepted: 4 January 2010 Published: 25 June 2010
Abstract
Proliferation of species introduced for aquaculture can threaten the ecological and economic integrity of ecosystems. We assessed whether the non-native Pacific oyster, Crassostrea gigas, has proliferated, spread and overgrown native Sydney rock oysters, Saccostrea glomerata, in Port Stephens, New South Wales (NSW), Australia, following the 1991 decision to permit its aquaculture within this estuary. Sampling of seven rocky-shore and four mangrove sites immediately before (1990), immediately after (1991–1992) and nearly two decades after (2008) the commencement of C. gigas aquaculture did not support the hypotheses of C. gigas proliferation, spread or overgrowth of S. glomerata. The non-native oyster, uncommon immediately before the commencement of aquaculture, remained confined to the inner port and its percentage contribution to oyster assemblages generally declined over the two decades. C. gigas populations were dominated by individuals of <40-mm shell height, with established adults being rare. Only at one site was there an increase in C. gigas abundance that was accompanied by S. glomerata decline. The failure of C. gigas in Port Stephens to cause the catastrophic changes in fouling assemblages seen elsewhere in the world is likely to reflect estuarine circulation patterns that restrict larval transport and susceptibility of the oysters to native predators.
Acknowledgements
We thank L. McClusky, M. Connell, B. Pearson and I. Anderson for field assistance during the earlier years of the project. B. Coates and S. Taylor assisted with the 2008 sampling. We thank NSW Department of Primary Industries, Taylors Beach for use of their facilities. Funding from NSW Fisheries supported the 1990 sampling. The 2008 sampling was funded by an Australian Research Council Linkage Grant LP0776360 to M. J. Bishop and W. A. O’Connor. All collecting was done under a NSW Department of Primary Industries Scientific Research Permit and complied with the laws of NSW. Professor A. Boulton and two anonymous reviewers provided helpful comments on an earlier version of this paper.
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