Ecology and conservation of cetaceans in the waters between Angola and the Gulf of Guinea, with focus on the Atlantic humpback dolphin (Sousa teuszii)


Weir, C. R.






398 pp.


West Africa, Gulf of Guinea, Balaenoptera edeni, Physteter macrocephalus, Sousa teuszii, Atlantic humpback dolphin


Part one of this thesis examined the tropical oceanic cetacean community occurring between Togo and Angola (6°N-11°S latitude). Twenty-two cetacean species were recorded during 5905.3 hr of dedicated survey effort from platforms of opportunity between 2004 and 2009. Sperm whales (Physeter macrocephalus) and humpback whales (Megaptera novaeangliae) were the most frequently-sighted species, and exhibited significant differences in occurrence related to water depth and survey month. Five species inhabited both neritic and oceanic waters, while the remainder were exclusively oceanic. The habitat preferences and niches (based on depth, seabed slope, sea surface temperature (SST) and frontal strength) of eight species were examined using classification trees and a principle component analysis. Water depth and SST appeared to be the primary variables (of those examined) explaining the presence of most species. Part two of the thesis was a study of the Atlantic humpback dolphin (Sousa teuszii), a species endemic to nearshore eastern tropical Atlantic (ETA) waters. A total of 1,626.8 km of boat- and vehicle-based effort in Namibe Province during 2008, produced 52 S. teuszii sightings. Further sightings were recorded during 53.7 hr of shore-effort at Flamingos (n=6) and opportunistically (n=13). Ten individuals were photo-identified. Multiple resightings (and an absence of unmarked animals) indicated low abundance, high site fidelity and year-round occurrence. Sousa teuszii produced simple (85% had a single inflection point) whistles in the 2.5-23.4 kHz fundamental frequency range and broadband click trains with repetition rates varying from 5.8-250.8 clicks/s. The implications of the findings for the future monitoring and conservation of cetaceans in the ETA are discussed.