Fish Fauna of the Nazca and Sala Y Gomez Submarine Ridges, the Easternmost Outpost of the Indo-West Pacific Zoogeographic Region

Fishes are now available from 22 of the numerous seamounts rising from the crests of the Nazca and Sala y Gomez Ridges which extend from Easter Island to near South America. A total of 173 species of fishes, in 66 families, exclusive of pelagic species, are now known from these seamounts, largely as the result of recent (1979 to 1987) Soviet expeditions in the area. Of these, 136 species in 58 families were found at depths of 160–580 m. The other 37 species are deeper-dwelling species found on the seamount slopes at depths of more than 600 m. There is a high degree of endemism, 42.8%, mostly related to species of Indo-West Pacific origin; 29.5% are Atlantic Indo-Pacific species; 14.4% are southern subtropical species; and 5.2% are species of uncertain assignment. Only 12 species occur on the ridges and along the coasts of South America. The vast majority are of Indo-West Pacific origin so it appears necessary to shift the boundary of the Indo-West Pacific by extending its southeastern margin from 106°W east to 80°. The high degree of endemism indiates that the area should be considered a separate zoogeographic province divided into two subareas, the Sala y Gomez Ridge and the Nazca Ridge.