Bioecological Study of Eightband butterflyfish (Chaetodon octofasciatus, Bloch 1787) to Detect Condition of Coral Reef Ecosystem in East Petondan Island, Seribu Islands, Jakarta

Abstract

Monitoring the changes of coral reefs is an important task considering many of the world’s coral reefs have been destroyed or severely degraded. There are reliable ways to indirectly assess the changes of a coral reef and monitor it through time: certain members of an easily identifiable conspicuous family of fish, Chaetodontidae, have been considered to be reliable indicators of reef health. Data of Chaetodon octofasciatus are based on field observation using SCUBA set on the reef slope (3 and 10 meter) and food and feeding habit analysis conduct in the laboratory. The percent coverage of living corals was estimated on the reef slope (3 and 10 meter) at all sites. A 50 m line transect were laid at each site and depth. By using belt transect the abundance of C. octofasciatus and the occurrence of each coral genus were counted and recorded in data sheets. Feeding rates were calculated by observing randomly selected species at study area. Ivlev’s electivity index was used to measure feeding selectivity, comparing the utilization of food with respect to its availability. The feeding bites to be larger in rich reef corals with high percentage of live coral. The feeding rates in south, west and north site which have high percentage of live coral is highest comparing to east site which have low percentage of live coral. Based on food and feeding analysis, the fish stomach contain 94,1% coral nematocysts and 0,59% periphytic algae, which indicated C. octofasciatus as an obligate coralivores.