ABSTRACT
Gonad index and maturity stages of gonad were compared between aggregated and dispersed subpopulations of Acanthaster planci in Okinawa Island in 1988 and 1989. Duration of spawning activities were different between the two subpopulations: the aggregated animals spawned in a period similar to that reported by previous workers, but the dispersed animals began to spawn 2 to 3 weeks later than the aggregated ones. These data suggested that a conspecific stimulus enhanced synchronous spawning activities in the aggregated subpopulations and that spawning activities might have occurred sporadically in the dispersed animals.
