Fish communities as related to substrate characteristics in the coral reefs of Kepulauan Seribu Marine National Park, Indonesia, five years after stopping blast fishing practices

Abstract

Blast fishing occurred in Kepulauan Seribu ("Thousand Islands"), southwest Java Sea, since 1970 s, as well as the other parts of Indonesia. Blast fishing stopped since 1995 when the Kepulauan Seribu Marine National Park was founded. Six islands from three management zones (core zone, intensive use zone, traditional use zone) were selected. Underwater visual censuses were carried out within 45 day-intervals (October 2000 - August 2001) at 4-5 m depth, with three transects (50 × 5 m) on each island. Within the fish transects, underwater sequential photographs were taken (50 x 1 m) to assess benthic groups and coral reef coverage. Dead corals were the dominant cover in all islands surveyed (range: 52 - 83 %). The long-lasting impact of blast fishing on the substrate was reflected by the presence of extensive fields of dead coral rubble (31 - 59 %). In contrast to the zoning allocation, the percent hard coral cover in the Sanctuary Zone was lowest and percent cover of dead coral was highest. A total of 119 fish species belonging to 25 families were determined. Planktivore and omnivore fish were the two most abundant trophic groups. The composition of the fish community changed seasonally according to the alteration of west and east monsoon. During the west monsoon, Chromis atripectoralis and Halichoeres argus, while during the east monsoon Pomacentrus lepidogenys, P. alexanderae and Cirrhilabrus cyanopleura were abundant, respectively. The fish community was more related to the presence of benthic groups and life form categories than to the coverage of hard corals. Pomacentrus lepidogenys was abundant at encrusting corals. Pomacentrus alexanderae was abundant at mushroom and dead corals. Chaetodon octofasciatus were abundant in areas dominated by Acropora corals. Benthic feeders and omnivores preferred substrate with high cover of dead corals. The results highly suggest a re-zoning of the national park.