Distribution of Acanthaster planci at Lord Howe Island, the southern-most Indo-Pacific reef

Abstract

Lord Howe Island, at 31°33′S, supports the southern-most coral reef in the Indo-Pacific region, located approximately 150 and 200 km south of Elizabeth and Middleton Reefs and 1000 km south of the Great Barrier Reef (GBR). Systematic SCUBA searches in 1987 indicated that Acanthaster planci was present at 3 of 10 sites surveyed, at densities of up to 5 individuals ha-1. Further surveys in 1989 indicated that the population was increasing, with densities of 20–46 ha-1 recorded from 7 of 13 sites. The size structures of the 1987 and 1989 populations were suggestive of annual recruitment since 1985. Individuals larger than 25 cm diameter were gravid during both surveys, raising the possibility that the population may be self-seeding. Alternatively, the population may be maintained by larvae dispersed in the East Australian Current from the southern GBR or in eddies from Elizabeth and Middleton Reefs. This study provides the first records for distribution of 7 species of scleractinian coral at Lord Howe Is. Reef.