Occurrence and distribution of cetaceans in São Tomé and Príncipe tropical archipelago and their relation to environmental variables

Abstract

São Tomé and Príncipe is an archipelago located in the Gulf of Guinea. This archipelago seems to be an important area for cetaceans, probably due to large concentrations of prey, as well as the existence of several small bays and shallow water that constitute preferred rest areas. In comparison to other areas of the world, little is known about cetacean communities in this archipelago. Boat-based surveys to record sightings of cetaceans were conducted between 2002 and 2005, which represents the first approach to study the occurrence of whales and dolphins in this tropical region. Sightings of humpback whales(Megaptera novaeangliae), bottlenose dolphins(Tursiops truncatus), pantropical spotted dolphins(Stenella attenuata), killer whales(Orcinus orca), sperm whales(Physeter macrocephalus)and pilot whales(Globicephala melas)were recorded. Cetaceans were found throughout a range of sea surface temperature between 24 and 29°C and a wide range of depths. Significant differences were found regarding the occurrence of some species. Humpback whales showed a preference for shallower waters between 20 and 100 m. Bottlenose dolphins occurred most commonly along the continental shelf (20 to 100 m) and pantropical spotted dolphins occurred in deep slope waters (>1000 m).