Contrasting reef fish diversity and abundance in the Derawan Islands: A multi-temporal observations

Abstract

Derawan Island, East Kalimantan Province, is located in the coral triangle, the center of mega biodiversity of the world's marine life, including reef fish. In this study, reef fish data were collected from 1994, 2003, and 2019 at six islands (Panjang, Derawan, Samama, Sangalaki, Kakaban, and Maratua) in Derawan Islands using the Underwater Visual Census (UVC) technique. The analysis results focused on herbivores, carnivores, and corallivores reef fish show that the total species diversity and abundance in 1994, 2003, and 2019 amounted to 116 species (5,268 fish/ha), 93 species (2,664 fish/ha), and 104 species (5,332 fish/ha), respectively. Those reef fishes decreased from 1994 to 2003 due to overexploitation but increased again in 2019, especially Acanthurid, Scarid, and Lutjanid fish taxa, possibly due to local government conservation regulations. Biodiversity and abundance were found higher in the Kakaban and Maratua Islands for herbivorous fish (>25 species, >3,500 fish/ha) followed by carnivores and corallivores (±20 species, ±2,000 fish/ha) than in other islands. The diversity of corallivores, herbivores, and carnivores was moderately correlated with live coral cover with R2 of 0.78, 0.77, and 0.61, respectively, but low for fish abundance. Long-term reef fish monitoring is necessary to know coral reef health in this area.