The Bight of Benin, a North Atlantic breeding ground of a Southern Hemisphere humpback whale population, likely related to Gabon and Angola substocks. Scientific Committee document SC/53/IA21, International Whaling Commission, July 2001, London

• Main Authors: Van Waerebeek, K., Tchibozo, S., Montcho, J., Nobime, G., Sohou, Z., Sehouhoue, P., Dossou, C.
• Format: Book
• Language: English
• Published: 2001
• Subjects: Megaptera novaeangliae; Pseudorca crassidens; Humpback Whale; Killer Whale; North Atlantic
• Online Access: https://www.vliz.be/imisdocs/publications/243239.pdf

Aiming to assess the feasibility for commercial whale-watching in coastal waters of Benin, exploratory boat transects were made from 12-19 October 2000. In 55h48min of observation, covering 349.6 nautical miles, 22 positive sightings of humpback whale and three ‘like-humpback whale’ groups were recorded. Relative group density was 0.448 sightings/hour observing or 0.072 sightings/nautical mile surveyed. Mean group size was 1.52 individuals (SD=0.92, range 1-5, N =25) and relative density 0.109 humpback whale/nautical mile. Additional evidence showed that other nations bordering the Bight of Benin, i.e. Ghana, Togo and Nigeria also are new Range States. Off Benin we observed three cow/calf pairs; one calf stranded in Ghana and more calves were reported from Togo. The calves, considering their small size and behaviour are thought to be born locally. Adult humpback whales often engaged in aerial display behaviour, including breaching, energetic surfacings, flipper-slaps, lob-tailing and spy-hopping. Two surface-active groups were seen, a behaviour linked to courting and mating. Occurrence off Benin and Togo is seasonal, from early August till early November. Although geographically situated firmly in the North Atlantic (boreal of 06°N), seasonality agrees with a breeding ground of a Southern Hemisphere population for which we propose the name ‘Bight of Benin substock’. Likely related to the IWC-defined Gabon and Angola substocks, combined these may form a wide-ranging Gulf of Guinea population. Overall sighting conditions were favorable and each of six trips resulted in at least one whale encounter, confirming whale-watching potential. A single ‘like-bottlenose dolphin’ group sighting was unrepresentative for small cetacean abundance when checked against frequent opportunistic observations. A collection of specimen identified as Pseudorca crassidens is the first record of false killer whale in the Bight of Benin.