An Ecological Survey of the Marine Fauna of Low Isles, Queensland

Abstract

The marine fauna of Low Isles was surveyed by the Great Barrier Reef Expedition of 1928-9. A cyclone in 1950 caused damage to the island's coral, and an expedition visited Low Isles in 1954 with the prime objectives of assessing the extent of this damage, and of ascertaining the extent and nature of changes undergone by the island and its fauna and flora since 1929.

It was found that the cyclone had caused great destruction to branching corals but that massive corals had, in most cases, survived. A heavy swell accompanying the cyclone had struck what is normally the lee side of the island, where a dense growth of fragile corals occurred. It is believed that the mechanical force exerted by breaking waves was the chief factor causing the destruction of corals. Coral rubble resulting from this destruction was being rolled about by waves on the seaward slopes of the island, and was hampering recolonization by hard corals. Soft corals, which appeared to have been unaffected by the cyclone, had spread, and appeared to be competing with hard corals for the available substratum.

Alterations in the topography of habitats investigated by the 1928-9 expedition were observed. Some of the shingle ramparts had increased in size, and shingle was encroaching on many of the moats. The mangrove area had increased in extent.

No marked changes in the faunistic composition of the fauna generally had occurred since 1929. However, direct comparison of the results of the 1928-9 expedition with those of the present survey proved difficult. In order to provide a basis for future surveys of the fauna, attempts were made to separate a large number of distinctive habitats, and to list the species found within each of these habitats. The relative abundance of each species found in each habitat was noted, and the general ecology and biogeography of the commoner animals investigated.