Recovery of a reef fish assemblage following hermatypic coral destruction by Acanthaster planci infestation

Research Project

Project/Area Number	05660200
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	General fisheries
Research Institution	The University of Tokyo
Principal Investigator	SANO Mitsuhiko The University of Tokyo, Faculty of Agriculture, Assistant Professor, 農学部, 助手 (50178810)
Project Period (FY)	1993 – 1994
Project Status	Completed (Fiscal Year 1994)
Budget Amount *help	¥1,300,000 (Direct Cost: ¥1,300,000) Fiscal Year 1994: ¥600,000 (Direct Cost: ¥600,000) Fiscal Year 1993: ¥700,000 (Direct Cost: ¥700,000)
Keywords	Dead corals / Recovery / Fish assemblage
Research Abstract	Changes in the structure of a reef fish assemblage along with recovery of hermatypic corals following heavy mortality by the coral-feeding starfish Acanthaster planci were investigated at Amitori and Sakiyama bays of Iriomote Island, one of the Ryukyu Islands of Japan, in October 1993 and 1994. At Amitori Bay, staghorn corals were completely killed with A.planci between 1981 and 1982. Dead coral branches had been strikingly degraded, and a flat plain of low-relief coral rubble remained by 1993. This reef is referred to as "dead coral reef." Corals of some areas at the bay, however, have recovered since 1988, and mean surface coverage of living staghorn corals on the reef was 81% in 1993 and 94% in 1994. This reef is referred to as "81% recovery coral reef" and "94% recovery coral reef, " respectively. Corals on the Sakiyama Bay reef, on the other hand, were not infested with the starfish, so living coral coverage on the reef was more than 95% in both years. Five transects 20 m long and 1 m wide were established on the living, dead, and recovery reefs each year. Fishes on each transect were counted by direct observation. The mean numbers of fish species and individuals per transect markedly decreased on the unstructured dead reef, compared with the living, 81% recovery, and 94% recovery reefs. These numbers showed no significant difference between the living reef and the 2 kinds of recovery reefs. Fish species composition also was similar between the living and recovery reefs each year. These facts suggest that the structure of the fish assemblage on the recovery reef returned to the predisturbance state, although living coral coverage did not recover the levels prior to the outbreak of A.planci.