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Courtship and spawning behavior is described for the grouper Cephalopholis spiloparaea from Rota, Mariana Islands. Daily courtship behavior began late in the afternoon and proceeded until after sunset. Males repeatedly visited females in single-male, multiple-female mating groups during each period and engaged in courtship bouts. Mating was observed only twice, was paired and pelagic. Two congeners, C. argus and C. urodeta, with overlapping geographical distributions, were also examined. Cephalopholis urodeta appeared to have a mating group organization similar to that of C. spiloparaea, with some similarity in courtship behavior. Cephalopholis argus also had a similar mating group organization but differed in courtship behavior. This species' behavior more closely resembled that of similarity-sized Epinephelus spp.

Behavior of male and female groupers, Cephalopholis spiloparaea, observed, between 1990 and 1991 in Sasanhaya Bay, Rota, Northern Mariana Islands, was compared to detect differences in proportional use between sexes, and between daylight and pre-courtship time periods. This species has male-dominated haremic groups. Time partitioning could not be measured exactly. Instead, the numbers of intra-and interspecific interactions, foraging, resting, swimming, and maintenance behaviors of each sex were measured during the observation periods. The proportion of acts in each category out of the total number of acts, termed effort, was used in comparisons. Males were predicted to devote more effort toward intra-and interspecific interactions compared to females and to maximize reproductive success. Females were predicted to devote more effort towards foraging, compared to males. This behavior maximizes reproductive effort. Both were predicted to engage in greater intra-and interspecific interactions during the pre-courtship period, corresponding both to the approaching time of courtship and to increases in the numbers of potential spatial and trophic competitors. Intra-and interspecific interactions of both males and females were greater during the pre-courtship period. Differences in all classes of behavior between sexes were only weakly significant for two, however. Males had greater effort in intra-and interspecific interactions. Females had greater effort only in maintenance behavior. Both differences were evident only during the pre-courtship period. Foraging behavior by both sexes was virtually absent during daylight and pre-courtship periods. Fish sought shelter and were not incidentally observed foraging after dusk, suggesting that this species actively forages later at night or during early morning hours, just prior to and during sunrise.

Habitat association and depth distribution of two sympatric coral reef groupers of the genus Cephalopholis were examined at Rota, Mariana Islands. The two species are similar in body size, morphology, and social organization. In this study, they differed in their association with habitat and microhabitat and in depth distribution. Cephalopholis spiloparaea occurred on the reef slope between the reef terrace and deep sand flats at depths between 15 and 26 m. This species was associated mainly with Porites rus corals. Cephalopholis urodeta occurred largely on the upper reef terrace at 1–12 m. This species was associated mainly with coral pavement. The observed pattern of segregation might be the result of competitive or noncompetitive interactions or of phylogenetic constraints, but the exact mechanism or combination thereof remains unknown.