Zonation of assemblages of Lutjanidae, Lethrinidae and Serranidae (Ephinephelinae) within and among midshelf and outershelf reefs in the central Great Barrier Reef

In December 1993, visual census surveys were conducted on three midshelf reefs (Rib Reef, John Brewer Reef and Lodestone Reef) and three outershelf reefs (Myrmidon Reef, Dip Reef and Bowl Reef) in the central Great Barrier Reef region.At each of the 6 reefs, surveys were conducted within 3 zones: the windward reef slopes; the lagoon; and the leeward back reef. Each census consisted of a 45 minute swim (on SCUBA) through a zone, recording the total number of each of the target species within approximately 5 m either side of the diver. All target species were surveyed simultaneously. Three replicate non-overlapping censuses, each covering a distance of approximately 400 m, were made in each zone on each reef.Census dives on the windward reef slope were unidirectional, consisting of a meandering swim from the reef crest to a depth of 12 m. In the lagoon and on the back reef, the paths were roughly unidirectional, meandering between bommies and coral outcrops to depths of 2-8 m and 12 m respectively. There was little information available describing the spatial distribution and abundance of demersal reef fish of commercial and recreational fishing significance in Australia. Visual census surveys were used to examine variation in assemblages of species of Lutjanidae, Lethrinidae and Serranidae within and among reefs at similar locations on the continental shelf and within and among reefs at different locations on the continental shelf.