Parin, N. V., Mironov, A. N., & Nesis, K. N. 1997. Biology of the Nazca and Sala y Gomez submarine ridges, an outpost of the Indo-West Pacific fauna in the eastern Pacific Ocean: composition and distribution of the fauna, its communities and history. Pp. 145-242 in Gebruk, A. V., Southward, E. C., & Tyler, P. A. (eds) The Biogeography of the Oceans. Advances in Marine Biology 32, 145-242.

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Study of the fauna of the submarine ridges in the south-eastern Pacific began in the 1950s, but the most detailed investigations were made in 1973-1987 during cruises of several Russian research vessels, notably the 'Ikhtiandr', 'Professor Mesyatzev' and 'Professor Shtokman'. At 22 seamounts of the Sala y Gomez and Nazca ridges, 177 genera and 192 species of benthopelagic and benthic invertebrates and 128 genera and 171 species of fishes were identified. Seven genera and 150 species were described for the first time: four and 74 among invertebrates, three and 76 among fishes. Bottom invertebrate communities of the seamount summits are characterized by strong dominance of a few species. At depths less than 400 m the spiny lobster Projasus bahamondei is dominant to the east of 83°W, while sea urchins predominate to the west. At greater depths sponges, gorgonarians, starfishes or shrimps are most abundant, in various combinations. Horse mackerel, Trachurus symmetricus murphyi (a temporary visitor from Chilean waters), usually dominates benthopelagic fish communities above the seamounts eastward of 85°W. Other abundant species are Emmelichthys cyanescens, E. elongatus, Decapterus muroadsi, Zenopsis oblongus, Epigonus elegans and Pentaceros quinquespinis, which all form the basis of a commercial fishery. Among bottom fishes Caelorinchus immaculatus (Nazca Ridge) and Pterygotrigla nicta were noted domains. The greatest diversity of fishes was observed at depths shallower than 500-600 m; the communities of soft-bottom and rocky biotopes differ significantly. The fauna of benthic and benthopelagic invertebrates and fishes of the area is much more closely related to Indo-West Pacific than to the Eastern Pacific fauna and is characterized by very high degree of endemism at species level (51% among identified bottom invertebrates, 44% among fishes). The seamounts of the Sala y Gomez Ridge and transitional Sala y Gomez/Nazca area westward of 83-84°W should be considered as a separate Nazcaplatensis Province of the Indo-West Pacific Region. Based on fish populations, the seamounts of the Nacza Ridge proper may be included in the same province, as a faunistically impoverished portion. On the basis of benthic invertebrates there is a link to the Eastern Pacific subcontinental Region. The faunistic composition of the main fauna of the Sala y Gomez and Nazca ridges can be explained by two main processes: eastward dispersal of the western Pacific fauna and active speciation in situ.

Pacific Ocean

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