remora, (family Echeneidae), any of eight species of marine fishes of the family Echeneidae (order Perciformes) noted for attaching themselves to, and riding about on, sharks, other large marine animals, and oceangoing ships. Remoras adhere by means of a flat oval sucking disk on top of their head. The disk, derived from the spiny portion of the dorsal fin, contains a variable number of paired crosswise plates.
Remoras are thin, elongated, rather dark fishes that live in tropical and subtropical oceans and seas. Remoras typically range from 30 to 90 cm (11.8 to 35.4 inches) in length, depending on the species. The live sharksucker, or slender suckerfish (Echeneis naucrates), is the longest, growing up to 110 cm (43.3 inches) in length; the white suckerfish, or white remora (Remora albescens), is the shortest, the largest individuals measuring only 30 cm as adults. Remoras feed on the leavings of their hosts’ meals or, in some instances, act as cleaners by eating the external parasites of their transporters.
Seven of the eight species of remoras are classified as species of least concern by the International Union for Conservation of Nature and Natural Resources. The conservation status of the eighth species, the whitefin sharksucker (Echeneis neucratoides), has not been fully assessed. Ecologists are concerned, however, that remoras could become threatened over time as shark populations continue to decline worldwide.