EFFECT OF DENSITY ON THE REPRODUCTIVE-BEHAVIOR OF THE TERRITORIAL-MALE DEMOISELLE CHROMIS-DISPILUS (PISCES, POMACENTRIDAE)

Characteristics of nest sites and reproductive behaviour of territoria l male demoiselles Chromis dispilus were examined at sites of low, med ium and high population density in northeastern New Zealand, by use of SCUBA diving and a remote underwater video system. Nest territories w ere closer together at high density (relative to areas of low populati on density) and this was accompanied by an increase in the frequency o f spawning sequences and territorial defence against conspecifics. Ter ritorial males were more aggressive during periods of display and spaw ning than during egg guarding. Fish from areas of low density spent mo re time on courtship display (signal jumps) and territorial defence ag ainst fish of other species, than demoiselles from areas of high popul ation density. Territories and nest sizes tended to be largest in area s of medium population density. As in other damselfishes, population d ensity is a major determinant of the frequency and intensity of reprod uctive behaviours.