Impact of Indonesian coral reef fisheries on fish community structure and the resultant catch composition

Abstract

Species and size composition of fish community structures were studied with underwater visual census (UVC), on Indonesian coral reefs subjected to different levels of fishing intensity. Comparisons were made between reefs within Spermonde Archipelago off SW Sulawesi, between reefs inside and outside a marine park in Komodo coastal area off West Flores, and between the reef areas of Spermonde and Komodo. In Spermonde, the species and size composition of the commercial catch at sites with high and low fishing intensity were recorded to determine how these catches reflected shifts in fish community structure. Overall fishing intensity in Spermonde was 557 boatdays km −2 reef yr −1, eight times higher than in Komodo (65 boatdays km −2 reef yr −1), but catch rates were eight times lower in Spermonde (5.6 kg per trip) than at reefs in Komodo (48 kg per trip). Total yield was similar in Spermonde (3.2 t km −2 reef) and in Komodo (3.1 t km −2 reef). Mean length of fish in the catch was significantly related to fishing intensity. Spatial patterns in the fish community within Spermonde as observed with UVC were not significantly related to patterns in fishing intensity. Within Komodo, total fish biomass and biomass of piscivores as observed with UVC were significantly higher inside than outside the park. Fish communities at reefs differed largely between Spermonde and Komodo, in mean individual length and in total biomass but numerical densities were similar. Our results indicate that an effect of fishing pressure on the fish community structure can be detected by UVC only when comparing sites which differ greatly in fishing intensity (Spermonde and Komodo) or when comparing sites with low and with medium fishing intensity (inside and outside a marine park). The species and size composition of commercial catches still demonstrate the differential effect of fishing intensity on fish community structures and so on the resultant catches in the on-average intensively fished reef area of Spermonde.