Fish species community composition of Curacao bays and reef
Student Report - University Groningen
Tropical coastal bays often border coral reefs and host connected ecosystems such as seagrass beds and mangrove forests. Similarly, the bays of the Caribbean island of Curaçao support unique coastal systems that include submerged multi-species seagrass beds and fringing red mangroves. These marine plants are form productive systems that are an important habitat for a variety of species. This includes nursery habitats for juvenile coral reef fish species, which utilizes food resources and refuge for predators prior to migrating to the coral reef. Many Caribbean marine habitats are under pressure due to growing tourism, overfishing and climate change, resulting in fish species disappearing form the reef. Concurrent, nursery habitats are threatened by coastal construction and eutrophication of waters. For effective protection of fish species, it is essential to include all lifecycles and their habitats. This study focused on 1) determining the fish species community composition of 6 Curaçao bays and reefs, focusing on five nursery species (French grunt, Schoolmaster, Mangrove snapper, Yellowtail snapper and Mutton snapper). 2) Determine how environmental factors influence the fish species community composition, and 3) get insight in the historical changes in reef fish species community composition in the last 25 years. For this, conducted a field survey across 6 Curaçao bays (Bartolbaai, Fuikbaai, Piscadera, Santa Martha, Sint Joris, and Spanish Water) and adjacent reefs. On 9 mangrove and 9 seagrass sites in each bay we sampled abiotic and biotic environmental parameters and fish species using a ~0.5mm mesh size seine net. Reef fish data was collected through diving transect surveys. Surprisingly, species diversity did not differ among sampled bays when taking all fish species taken into account. In contrast, species abundance did differ among bays. Santa Martha had a significantly lower species abundance than Fuikbaai. Focusing on five nursery species, we observed a surprising difference in both species diversity and abundance between bays and the connected reef habitats. Fuikbaai and Santa Martha show a lower abundance for nursery species on the reef than in the bay. In the bays there are significant difference for species diversity and abundance between Bartolbaai/Piscadera and Santa Martha. Furthermore, our environmental analysis furthermore showed that both bay size and mangrove root density are determinants for fish species composition. Additionally, to mangrove root density, seagrass shoot density and bay depths are important determinants for the species composition of the selected nursery fish species. Multivariate tests showed that a shift in the reef species community composition has occurred. The results of this study help determine which environmental factors are critical in supporting fish species communities in Curaçao. In addition, it gives insight into alternative conservation measures to protect coral reef fish species.