Reef Fish Inventory of Juan De Nova's Natural Park (Western Indian Ocean)

Abstract

This paper constitutes the first study on reef fish communities at Juan de Nova, one of the Eparses Islands in the Mozambique Channel. These remote islands, with no permanent habitation, except a small military base, represent sites which experience minimal direct human influence. Sampling was firstly done by underwater visual observations, using SCUBA diving gear, at 31 stations distributed equally over the coral reef, between depths ranging from 0-15 m, and secondly, by using an anaesthetic in littoral rockpools. A total of 299 species belonging to 55 families were recorded. Nearly half of the observed species belong to five main families: Labridae (41 species), Pomacentridae (28 species), Acanthuridae (24 species), Serranidae (22 species), and Chaetodontidae (18 species). Among the reported species, 73% are carnivores, 16% herbivores and 11% omnivores. Some families are well represented, especially the carnivores such as sharks (Carcharhinidae, 6 species), the groupers (Serranidae, 20 species) and the snappers (Lutjanidae, 10 species), which are common at nearly every station sampled. The presence of these carnivorous species could be related to the absence of fishing pressure in the area. However, some species known to be common in the area seemed rare (e.g. Chaetodon trifascialis, Dascyllus carneus, Labroides bicolour) or entirely absent (Pseudanthias cooperi, Cephalopholis miniata, Chaetodon unimaculatus, Plectroglyphidodon johnstonianus and Lepidozygus tapeinosoma). From a biogeographic point of view, this study revealed a fairly diverse reef fish community for such a small, isolated island, located on the westward extreme (~ 45°E, 15°S) of the Indo-Pacific. The absence or the paucity of certain species and/or families could be the consequence of the 1998 massive coral bleaching. There is a need for long-term studies in order to better understand the resilience of coral reef communities to environmental disturbances..

Keywords: reef fishes, diversity, Eparses Islands, natural reserve, western Indian Ocean, biogeography, massive bleaching

West Indian Ocean Journal of Marine Science Vol. 4 (2) 2005: pp. 145-162