Difference in the trophic structure of fish communities between artificial and natural habitats in a tropical estuary

Abstract

The present study tested the hypothesis that artificial habitats (pier and bridge) harbour different fish trophic guilds compared with natural habitats (mangrove roots) and that the trophic structure of fish communities on estuarine artificial habitats resembles adjacent coral reefs. High-definition cameras were used to survey the fish community associated with the different structures over a 6-month period. Benthos was also analysed following the point intercept method on the different habitats. In the estuary, fish abundance was up to threefold higher and species richness twofold higher on artificial structures compared with the natural habitat. Mangrove roots were mainly inhabited by juvenile carnivores, whereas the pier and bridge were mostly inhabited by sessile invertebrate feeders and roving herbivores. A less diverse benthic community was found on mangrove roots, mostly composed of mud and algae. In contrast, benthos at the bridge and pier was more diverse and dominated by sponges, octocorals and oysters. In addition, fish trophic structure from an adjacent coral reef area showed more than 60% similarity with the fish community on the artificial structures surveyed. The results of the present study indicate that artificial hard structures support unique fish communities compared with natural estuarine mangrove habitats.