Cetacean distribution and relative abundance in offshore Gabonese waters

• Published in: Journal of the Marine Biological Association of the United Kingdom
• Main Author: de Boer, Marijke N.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 2010
• Subjects: baleen whale; Humpback Whale; Megaptera novaeangliae; Sperm whale
• Online Access: http://dx.doi.org/10.1017/s0025315410001165; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0025315410001165

Information on cetaceans off Gabon in tropical West Africa is summarized from boat-based surveys carried out between 7 March and 7 August 2009. Thirteen cetacean species were positively identified comprising two baleen whale species, one sperm whale species and ten species of delphinid. Bryde's whale ( Balaenoptera brydei ) and humpback whale ( Megaptera novaeangliae ) were the most frequently encountered species. Cetaceans were found throughout a range of sea surface temperature between 20.5°C and 27.5°C and a wide range of depths with the majority of effort and sightings occurring seaward of the shelf break. Of particular interest from the study were the following: (1) Gabonese waters have a broad cetacean diversity, especially with a large and diversified delphinid community in the northern part of the study area; (2) the variations in oceanographic conditions within Gabonese waters are likely to result in a temporal variation in species composition; (3) the sightings of Atlantic spotted dolphin ( Stenella frontalis ) are the first at-sea sightings confirmed for these waters, although not unexpected given their distribution and abundant presence in surrounding waters; and (4) the poorly known Clymene dolphin ( Stenella clymene ) was sighted on four occasions in deep oceanic waters and was the most abundant cetacean. These are the first confirmed records of Clymene dolphins in Gabonese waters.