Effect of density on the reproductive behaviour of the territorial male demoiselle Chromis dispilus (Pisces: Pomacentridae)

Abstract

Characteristics of nest sites and reproductive behaviour of territorial male demoiselles Chromis dispilus were examined at sites of low, medium and high population density in northeastern New Zealand, by use of SCUBA diving and a remote underwater video system. Nest territories were closer together at high density (relative to areas of low population density) and this was accompanied by an increase in the frequency of spawning sequences and territorial defence against conspecifics. Territorial males were more aggressive during periods of display and spawning than during egg guarding. Fish from areas of low density spent more time on courtship display (signal jumps) and territorial defence against fish of other species, than demoiselles from areas of high population density. Territories and nest sizes tended to be largest in areas of medium population density. As in other damselfishes, population density is a major determinant of the frequency and intensity of reproductive behaviours.