Community Structure and Fish Diversity in Some Mangrove Ecosystems with Varying Levels of Naturalness and Human Activity on Bawean Island, East Java, Indonesia

Abstract

The research aimed to evaluate the quality of some mangrove ecosystems on Bawean Island with varying levels of naturalness and human activity through community structure and diversity of fish species. Sampling was carried out in 11 mangrove ecosystems of Sawahmulya, Sungai Rujing, Hijau Daun, Sidogedungbatu, Pamona, Pasir Putih, Bangsal, Dekatagung, Jherat Lanjheng, Lebak and Pulau Cina. Fish were collected using the net (pore size 5 mm) and visual encounter method. Fish found were identified then the abundance of each species was used to determine the total abundance, taxa richness, and some indices of diversity, dominance, and evenness. Results showed that there were 18 fish species we found in all locations with varying taxa richness in each mangrove ecosystem. The total abundance of mangrove fish is in the range of 61-165 Idv/25m2. All the research sites show a low value (less than 1) in the Diversity Index of Shannon Wiener, low evenness (0.02-0.07), and high variation of dominance Index (0.26-0.94). The higher the level of naturalness and the lower the hemeroby Index, it was found to have an impact on the higher diversity, taxa richness, and evenness of fish. This research indicated that the quality of some mangrove ecosystems on Bawean Island was still low and needed to be managed.