Composition, distribution and regional affinities of the deepwater ichthyofauna of the Lord Howe Rise and Norfolk Ridge, south-west Pacific Ocean

Fishes were collected from seamounts and insular slopes of the northern Tasman and southern Coral Seas in the environs of the Reinga Ridge, Norfolk Ridge and Lord Howe Rise, at depths ranging from 49 to 1927 m. A total of 348 demersal fish species in 99 families, which were collected from 135 samples taken with a variety of sampling gear, greatly improved taxonomic knowledge of this poorly known area. Twenty five percent of the fish sampled are considered to be potentially new species. Relatively high levels of regional endemicity and diversity are attributed to geological history, and the complexity of contemporary climatology, hydrography and habitat diversity of the region. Fish assemblages were highly structured by depth, but across regions, deep-water fish faunas showed stronger taxonomic affinities than shallower faunas. Although less pronounced, spatial differences pointed towards distinct faunas between the southern and northern parts of the area. The distribution patterns and affinities to regions adjacent to the survey area indicate that (1) the fish fauna on the Lord Howe Rise near Lord Howe Island and further north is distinct from the rest of the survey regions, and exhibits eastern Australian and northern (Coral Sea) affinities, (2) the Northern Norfolk Ridge fauna is distinct from the other regions and has strong affinities with New Caledonia, (3) fishes on the Southern Norfolk Ridge, Western Norfolk Ridge and Lord Howe Plateau have more shared species compared to the other regions indicating a high level of connectedness and affinities with New Zealand fauna, and (4) some species have a wide distribution along the Norfolk Ridge providing a possible deepwater pathway between New Caledonia and New Zealand. Survey data is also useful for assessing the regions' conservation values by identifying rare or unusual components of the fauna, those with very limited distributions, those with low productivity that may be vulnerable to human disturbance (fishing, mining), and for defining bioregions.