Changes in the structure of a fish assemblage following macroalgal overgrowth on an Acanthaster-infested coral reef

点击翻译按钮获取中文摘要

At Amitori Bay of Iriomote Island, one of the Ryukyu Islands of Japan, staghorn corals were completely killed with Acanthaster planci between 1981 and 1982. By 1986, all of the dead corals had collapsed drastically, and a flat plain of low-relief coral rubble remained. Since around 1994, a regular increase in the cover of erect fleshy macroalgae has occurred in an area at the plain, attaining about 36% cover in 1999, although some other areas have undergone recovery of corals. I examined, therefore, the patterns of responses of a fish assemblage to a large increase in macroalgae on a coral reef degraded by an outbreak of A. planci in October from 1997 to 1999.Five transects 20 m long and I m wide were established on the macroalgal area and rubble area without erect algae. Fishes (adults and juveniles) on each transects were counted by direct observation.The mean number of species of adults per transect showed no significant difference between the algal area and rubble area every year from 1997 to 1999. The mean number of adult individuals was significantly greater in the algal area than in the rubble area each year, but the density of the former area remained low. For juveniles, on the other hand, there were no significant differences between the two areas in the mean numbers of species and individuals each year. These facts suggest that dominance of reefs by macroalgae following extensive mortality of corals has only a little effect on the structure of fish assemblages.