Surveys of fish-habitat associations using Baited Remote Underwater Video Stations (BRUVS (TM)) offshore from Port Hedland, Western Australia

In July 2012, baited remote underwater video stations (BRUVS (TM)) were deployed in the vicinity of Port Hedland, in two areas parallel to the coast (inshore and offshore) on either side of the shipping channel and some dredge spoil grounds, in depths of 4.6 to 24 metres.The survey design specified the deployment of 230 BRUVS (TM) at random within grids of the two study areas, at a spacing not less than 450 metres apart, to minimise the likelihood of individuals moving between stations and being double-counted. Of the 230 BRUVS (TM) deployed during the field campaign, 221 produced imagery of sufficient quality for analysis.Commencing immediately after reaching the seafloor, 60 minutes of bottom-time was analysed for all video recordings, regardless of whether video extended longer. Data was recorded using a purpose built interface and included identification to species level and life stage (adult or juvenile) of all vertebrates, relative abundance (MaxN ; maximum number visible at any single point on the tape), time of arrival and the time elapsed before MaxN and feeding occurs. Depth and GPS position of each deployment, estimates of water clarity and the timing of ancillary events such as feeding activity and loss of bait bag were also recorded.The habitat at each station was classified by reviewing an image of the seafloor from each of the BRUVS (TM) sampling stations. To provide quantitative estimates of habitats, the percentage cover (to the nearest 10%) was then determined for six categories of (abiotic) substratum, summed to 100%, and for 12 categories of (biotic) epibenthos, also summed to 100%. This study was undertaken to provide baseline estimates of fish diversity and relative abundance in direct relation to habitat and depth within inshore and offshore areas in the vicinity of Port Hedland, where a large expansion of port facilities will be accompanied by dredging and relocation of dredge spoil on adjacent seabeds in the local region.