Fish and benthic surveys in intermediate and deeper waters of Ningaloo Marine Park, Western Australia, using baited remote underwater video stations (BRUVS (TM))

A total of 18 BRUVS sets were made offshore from Mandu Mandu, Point Cloates and Maud Point in depths ranging from 66-96 metres. Most of the sets were made where the habitats in the immediate field of view were flat sediments, with or without visible bioturbation from the activities of small burrowing animals. All three sets at Mandu Mandu were in flat, sandy habitats. Three of the six sets made off Point Cloates had significant cover of benthic sponges, fan and whip gorgonians, and other biotic or abiotic structures. Only two of the nine sets made offshore from Maud Point had such cover, and it was much sparser in the field of view of the cameras. Most taxa were identified to species level, with the notable exception of the very small juveniles of threadfin breams (Nemipterus sp.), and the small (<60 cm total length) sharpnose or sliteye sharks (Rhizoprionodon taylori or Loxodon macrorhinos). Published diagnostic features for these species could not be resolved on the footage. The maximum number of fish from each species seen in each video frame (MAXN) was recorded. The surrounding habitat was classified into three broad classes: fine sand, course sand and megabenthos. The measures of the various depths, the habitat classes, and the fish species abundance were analysed from multiple BRUVS sites, or sets. Multivariate analyses are required to examine the multidimensional relationships among the sites, the environmental variables and fish species. These analyses allowed us to describe the major groupings in the BRUVS data, measure the strength of fish-habitat associations, and identify indicator species defining these patterns.

The study was undertaken for the Commonwealth Government Department of the Environment and Heritage, to begin a process of describing deepwater biodiversity in the Ningaloo Marine Park and to address a lack of such information seaward of Ningaloo Reef crest. Another aim of the project was to identify any areas of high biodiversity in both Commonwealth and State waters of the park. This information would be used to assist in identifying potential sanctuary zones to preserve the areas of high biodiversity that are considered to be relatively important within the reserve. The study sites chosen were adjacent to existing State marine sanctuary zones. BRUVS deployments were made to investigate fish and elasmobranch community composition in relation to habitat within the study sites.