Bishop M.J.,Macquarie University |
Krassoi F.R.,University of Technology, Sydney |
Krassoi F.R.,Ecotox Services Australasia Pty Ltd. |
McPherson R.G.,University of Technology, Sydney |
And 4 more authors.
Marine and Freshwater Research | Year: 2010
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. © 2010 CSIRO.
Lowry M.,Port Stephens Research Center |
Folpp H.,Port Stephens Research Center |
Gregson M.,Port Stephens Research Center
Fisheries Research | Year: 2011
This paper describes a solid state memory (SSM) video camera system designed for extended deployment as a remote underwater video device with applications for measuring fish abundance and diversity. The video camera was evaluated in a series of lab-based trials to establish performance parameters (power consumption, data accumulation rates and maximum continuous recording time). The system performed reliably with a mean maximum continuous recording time of 13.3 (±0.3). h. Field trials were carried out to (a) compare results of video parameters, number of species identified (Nsp), maximum number of each species (MaxN) and time at first appearance of each species (TFAP) to a conventional standard definition video system and (b) examine the effect that a reduction in image resolution has on these parameters. Results indicated no significant differences between the standard definition camera and the test system at the highest resolution stetting (640 × 480). However, the total number of species identified by the reader was significantly less at the low resolution setting (176 × 144) and a significant reduction in relative abundance (MaxN) and TFAP were identified for both the mid (320 × 240) and lowest resolution (176 × 144) settings. Results indicate the solid state camera system is useful for extending recording time above that of standard definition cameras. However, there is limited potential to extend deployment times of BRUV systems via a reduction in video resolution without significant compromises to the accuracy and precision of the key indicators for diversity and abundance of fishes. © 2011 Elsevier B.V.