Gray Unicornfish, Naso caesius (Acanthuriformes: Acanthuridae), from Kita-daito-jima, Daito Islands, Okinawa Prefecture, Japan; first northwest Pacific record

Abstract

A single specimen of the acanthurid fish Naso caesius Randall and Bell, 1992 (Acanthuriformes), previously reported from Micronesia, Polynesia, Melanesia, eastern Indonesia, New Guinea and Australia, was recently collected from Kita-daito-jima, Daito Islands, Okinawa Prefecture, Japan, the northernmost record for the species and first from the northwest Pacific Ocean. Naso caesius differs from its congeners in having two semicircular keels lacking antrorse spines on the caudal peduncle bony plates, no hornshaped process on the forehead, VI–VII, 27–30 dorsal-fin rays, 28–31 anal-fin soft rays, 16–18 pectoral-fin rays, a truncate caudal fin in adults, vertically elongate pale blotches on the upper two-thirds of the body, and a white tongue and brown anal fin. The new standard Japanese name “Yumihari-tenguhagimodoki” is proposed for the species.