Inter-reef vertebrate communities of the Great Barrier Reef Marine Park determined by baited remote underwater video stations

A fleet of baited remote underwater video stations was set in lagoonal and inter-reef waters of the Great Barrier Reef Marine Park, across 14° of latitude and the entire shelf. Counts of the maximum number seen in any one field of view were used to estimate relative abundance of 347 species of bony fishes, cartilaginous fishes and sea snakes. Boosted regression trees were used to assess the influence of depth and location of sampling sites on species richness. Multivariate regression trees and indices of specificity and fidelity (Dufrêne-Legendre indices) were used to distinguish 17 spatially contiguous vertebrate groups within a hierarchy of spatial scales. Location across the shelf and depth had the greatest influence on species richness, with peaks occurring around the ~35 m isobath in the inter-reef waters of the reef matrix, coinciding with shallow banks and shoals. Richness increased slightly toward the equator. Nine terminal vertebrate communities parallel to the coast were distinguished inshore and offshore in deep and shallow water along a latitudinal gradient. There were important community boundaries at Bowen in the south, Townsville in the centre, and Cape Flattery in the north. Latitudinal groupings were most evident inshore. Offshore communities were spatially extensive and separated lagoonal, mid-shelf and outer-shelf sites. Community boundaries were correlated with knowledge of strong gradients in sedimentary and oceanographic processes influenced by the shape of the reef matrix and regional tides and currents.