Assessing Undiscovered Fish Biodiversity on Deep Coral Reefs Using Advanced Self-Contained Diving Technology

Due primarily to limitations of existing technology, deep (60‐150 m) coral reefs have remained largely unexplored. In 1989 I began developing the use of mixed-gas SCUBA and other ‘technical’ diving techniques as a tool for ichthyological investigation of coral reefs at depths of 60‐150 m, and have since conducted initial exploratory expeditions to the Cook Islands, Papua New Guinea, and the Patau Islands. These expeditions yielded over 200 fish specimens, comprising more than 100 species representing 20 different families. Among these are more than fifty new species, three-quarters of which belong to the families Labridae, Gobiidae, and Serranidae, and the rest are among 9 other families. The number of new species within each family parallels that of the overall deep-reef species assemblage, except for Apogonidae with a total of 7 collected species, none of which were new. Analysis of specimens and videotape surveys of the ichthyofauna at one 90-m site in Patau suggests that as many as 70% of the species inhabiting this depth are undescribed. New species assemblages on deep reefs show comparatively low distributional overlap (both between different island groups, and between sites within each island group), suggesting higher rates of geographic endemism than for shallow-reef assemblages. Based on these and other observed patterns, conservative extrapolations suggest as many as 2,000 or more coral-reef fish species await discovery on deep coral reefs throughout the Indo-Pacific.