Sexual Dimorphism in the Labrid Fish Pseudolabrus celidotus (Bloch and Schneider) 1801

Abstract

During a systematic study of New Zealand fishes belonging to the genus Pseudolabrus Bleeker 1861, it was observed that one of the commonest species, P. celidotus, occurred in two distinct colour phases. This was first noted by Richardson (1848) who described the two colour variants as separate species. The subsequent literature did not recognise these as species, but merely as varieties, although the true relationship was not clarified. A study of populations of this species, both in the field and in the laboratory, revealed that the colour differences were due to sexual rather than environmental or geographic factors, and represented a moderately developed degree of sexual dimorphism. An attempt has been made here to examine the relative proportions of each colour phase in selected populations, the sequence of transition from one colour phase to the other, and the sizes at which transition occurs.