Semi-quantitative, timed censuses of fish abundance and diversity were made off Enewetak Atoll, Marshall Islands at depths from 30 to 180 m, by means of the RSV Makali'i, and supplemented by a series of qualitative dives at various points around the atoll to depths of 300 m. Analysis
of data indicate a monotonic depth-associated decline in number of species seen, a peak in total population density between 90 and 120 m, and abrupt declines between 75 and 90 m in community diversity and proportional representation of shallow water species. Each of six trophic groups exhibited
a different depth distribution, about the abundances of coralivores, herbivores, benthic predators and cleaners correlated across depths. Data suggest the occurrence of a single faunal assemblage of reef fishes from the surface to approximately 250 m, which can, however, be profitably divided
into three communities: a shallow fore reef community (0 to 75–90 m) characterized by high diversity and high densities of fishes, a middle fore reef community (75–90 to 120 m) dominated by a few species of planktivores and characterized by a high percentage of species that do
not normally occur closer to the surface, and a deep fore reef community (120 to roughly 250 m) characterized by very low levels of fish diversity and abundance.
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