Acanthaster planci population survey on the north coast of Moorea, French Polynesia

Abstract

Recent increases in observations of Acanthaster planci in lagoons on the North Coast of Moorea, French Polynesia have prompted a population survey on both the outer reef slope and inside the lagoon. Nine transects were performed along the coast between (S 17°28.971’, W 149°54.130’; & S 17°28.65’, W 149°50.75’). A. planci population was found to be very patchy. Timed surveys using SCUBA showed the population of stars on the outer reef slope to be concentrated in a depth range between 15-30m, with a high concentration 40/Ha near one of our transects. Measured density transects were performed at this site and the density was shown to be 4,000/km2, higher than the 6/km2 baseline for the western Pacific. Transects inside the lagoon were between 120-220/km2 for three areas surveyed. The overall A. planci population appears slightly higher than normal when sampling difficulty, and error margins are factored in.