There are five common species of wrasse (Labridae) in British coastal waters, two of which are hermaphrodite, (Labrus bergylta Ascanius and Labrus mixtus L.) and three are gonochorists with discrete sexes (Ctenolabrus rupestris) (L.), Centrolabrus exolelus (L.) and (Crenilabrus melops (L)) (Dipper & Pullin, 1979; Dipper, 1981). L. bergylta (Sjolander, Larson & Engstrom, 1972; Potts, personal observation) and L. mixtus (Wilson, 1958; Potts, 1984) lay their eggs in shallow depressions excavated in coarse paniculate substrates often closely associated with sublittoral reefs. Ctenolabrus rupestris, the smallest of the species is most usually associated with sublittoral crevices, and is the only one to produce pelagic eggs despite showing territorial aggression in the spawning season, a behaviour mostly confined to species with demersal eggs. Little is known about Centrolabrus exoletus, but from the striking sexual dichromism at maturity and its association with rocky reefs it may be supposed that it exhibits some form of parental care for the demersal eggs (Potts, 1984). Crenilabrus melops shows parental care of its eggs which are laid in large and complex algal nests, a feature which is common to all this genus (Fiedler, 1964; Quignard, 1966; Potts, 1984). The corkwing wrasse is one of the commonest coastal species which at maturity show sexual dimorphism and dichromism, a feature which led to taxonomic confusion among earlier workers and which is discussed by Potts (1974).