Changes in the distribution and abundance of crown-of-thorns starfish (Acanthaster planci) and hard corals over an outbreak cycle at John Brewer Reef, central Great Barrier Reef

Two permanent study sites were established along the fore reef slope of John Brewer Reef in October 1982. Quantitative surveys of the hard corals at each site were made using line transect techniques. Two replicate line transects, each 50 m in length, were laid out along the following depth contours: 1.5 m (reef flat), 3 m (reef crest), 6 m, 9 m and 12 m below mean water level at site A. Because of insufficient depth, line transects were laid out only to the 9 m contour at site B.

The corals at Site A were surveyed during October 1982 and resurveyed in May 1984. Site B was surveyed in May 1983 and resurveyed in January 1984. Corals were identified to species level and the percentage cover of hard corals was determined.

Manta tow surveys around the perimeter of the reef were conducted in October 1982, October 1983, January 1984 and May 1984 and the abundance of crown-of-thorns starfish was recorded for each 2 minute tow.

The sizes of a large number of crown-of-thorns starfish (Acanthaster planci), occurring in areas with the largest concentration of starfish at the time of sampling, were measured. Starfish were measured at one site in October 1983, two sites in January 1984 and three sites in September 1984.