HORIZONTAL AND VERTICAL DISTRIBUTIONS OF LARVAL FISHES AROUND AN ISOLATED OCEANIC ISLAND IN THE TROPICAL PACIFIC

Ichthyoplankton and oceanographic sampling was conducted in November 1984 in waters surrounding Johnston Atoll (16-degrees-44'N, 169-degrees-32'W). a small, isolated atoll in the central Pacific Ocean. The typical flow pattern in this region is westward; the nearest island is in the Hawaiian Archipelago, 760 km away. Most collections were dominated by oceanic taxa. In the 0-50 m stratum, larval densities were relatively uniform horizontally. but densities down-current of the island tended to be higher, and fish eggs were concentrated there. In the 50-100 m stratum. larval abundance on the down-current side of the island was markedly higher than either up-current or farther down-current. Oceanic taxa did not display this pattern, while marked areas of very high abundance characterized the island-related taxa, the most abundant including the gobiid Eviota epiphanes and the apogonid Pseudamiops sp. Estimates of geostrophic flow indicate that the region down-current of the atoll was one of return flow associated with apparent mesoscale eddies or meanders north and west of the island. This region may serve as a down-current retention area for the pelagic larvae of island-related taxa and may facilitate recruitment back to the source populations.