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Sampling Design
Reefs are surveyed for crown-of-thorns starfish using the manta tow technique in 11 sectors of the Great Barrier Reef (Cape Grenville, Princess Charlotte Bay, Cooktown/Lizard Island, Cairns, Innisfail, Townsville, Cape Upstart, Whitsunday, Pompey Complex, Swain and Capricorn Bunker sectors). Benthic communities are surveyed annually within six of these sectors (Cooktown/Lizard Island, Cairns, Townsville, Whitsunday, Swain and Capricorn Bunker sectors) on permanent sites. In each of these sectors (except for the Capricorn Bunker sector) three shelf positions (inner, mid and outer) have been identified. In the Capricorn Bunker sector, only outer shelf reefs are represented, with four reefs being surveyed. Shelf position is determined by the position of the reef relative to the coast and continental slope, with inner shelf reefs being closest to the coast. In addition to the manta tow survey and water sampling, a single habitat is surveyed on each reef, typically situated on the north-east flank of the reef. It is defined as the first stretch of continuous reef, going in a clockwise direction from the back reef zone towards the reef front, with a slope less than vertical. The selection of a common habitat allows comparisons to be made between reefs, both within and between sectors. Within this habitat three sites are selected, each containing five, permanently marked, 50 metre long transects, lying roughly parallel to the reef crest. Further details of the design can be found in Oliver et al. (1995). Transects are set-up along the reef slope between 6 and 9 metres depth. The transect is marked at the beginning and at the end with a starpicket and at 10 metre intervals with steel reinforcing rods (10 mm diameter.). A tape measure stretched between the starpickets and rods mark the centre line of each transect. Each starpicket is labelled with an aluminium tag (identifying the transects as belonging to AIMS project 221). The GPS position of the starpicket at the beginning of the first transect of each site is recorded in a database. This starpicket is also marked with a subsurface buoy to aid in locating the site. Fish abundance surveys, benthic surveys and SCUBA search surveys for coral mortality are conducted along each transect.
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