Surveys of deep water benthic fish and elasmobranchs using stereo-BRUVS in Ningaloo Marine Park, Western Australia (WAMSI Node 3 Project 1 Subproject 3.1.1)

Full description

This field survey was planned around the outcomes of the towed video and acoustic survey undertaken by AIMS staff and FUGRO in April of 2006. The towed video and acoustic survey provided information on the distribution of benthic habitats in the area between the 15 and 100 m depth contours and allowed us to target sampling within specific habitats and depths. Within these areas a number of random samples were allocated. Sampling occurred in five areas including Mandu, Osprey and Cloates Sanctuary Zones, and Osprey and Cloates reference areas. 185 stereo-Baited Remote Underwater Video Stations (stereo-BRUVS) samples in total were collected.
The aim of this research was to characterize the structure and distribution of deepwater fish assemblages (greater than 10 m depth) outside the crest of the Ningaloo Reef and to provide information about the diversity, spatial distribution and habitat affiliation of demersal fin fishes across a range of depths and habitats within the northern section of Ningaloo Marine Park.
The stereo-BRUVS used Sony HC15 digital camcorders within waterproof housings. Bait arms made of 20 mm plastic conduit with a standard rock lobster bait canister fastened to one end were attached to the stereo-video frame and detached after deployment. We used ~ 800 gms of crushed Sardinops sagax placed in the bait bag for each deployment. The stereo-BRUVS were retrieved after recording for one hour at each station. At deep sites where available light was extremely low on the seafloor, the stereo-BRUVS were set to record on night shot. Stereo-BRUVS rather than single cameras were used due to their ability to capture a baseline of the relative abundance of fishes and their length frequency. Single video BRUVS can only provide a measure of absence or presence of a species as data cannot be standardized for area sampled. Stereo-BRUVs facilitate measurement of distance allowing a consistent area to be defined and used spatially and temporally. Interrogation of each tape was conducted using a custom interface (BRUVS1.5.mdb©, Australian Institute of Marine Science 2006) to manage data from field operations, tape reading, capture the timing of events, capture reference images of the seafloor and fish in the field of view. The following data were recorded for each species; the time of first sighting, time of first feeding at the bait, the maximum number seen together at any one time on the whole tape (MaxN), time at which MaxN occurred, and any intraspecific and interspecific behaviour. The use of MaxN as an estimator of relative abundance has been reviewed in detail by Cappo et al. (2003, 2004). Estimates of MaxN are considered conservative, particularly in areas where fish occur in high densities.

Lineage

Maintenance and Update Frequency: asNeeded

Notes

Credit
Heyward, Andrew J, Dr (Principal Investigator)