Bony fish have a skeleton of bone, and a single gill opening on each side of the head. In most species the skin is covered in scales, which protect the fish. Bony fish are extremely diverse in shape and size, adapting to a wide range of different habitats and having specialised mouthparts to exploit different food, from algae to invertebrates and other fish. Most species have external fertilisation, with some species caring for their young.
The fish fauna of Lord Howe Island has been well documented, with more than 490 species recorded. Approximately 60% of the fish species are tropical, 15 species are endemic to the region, and the remainder are sub-tropical and temperate fish species. Most of the fishes are widely distributed in the Indian and Pacific Ocean areas, as well as in the adjacent waters in eastern Australia. It is generally concluded that there are still unrecorded species, and that the total count could easily exceed 500 species. As a result of ongoing larval dispersal from the Great Barrier Reef, the LHI fish fauna will always be changing, and may never be completely known.