Juvenile fish
The sexes are separate in this species, and both sexes become mature at a length of about . Large aggregations of fish occur at breeding time, with both sexes liberating their gametes into the water column. The scalpels on the caudal peduncle are retractable and are very sharp; they are displayed when the tail is thrust to the side and are used to slash at rival fish and for protection against predators. Juvenile fish are shorter and more deep-bodied than adults. They are deep brown at first, with a yellowish, unnotched caudal fin, and gradually change colour as they reach a length of between .