Title
False killer whale (Pseudorca crassidens) sightings in continental shelf habitat off Gabon and Coˆte d’Ivoire (Africa)
Author(s)
Weir, C. R.;Collins, T.;Cross, T.;Gill, A.;Elwen, S.;Unwin, M.;Parnell, R. J.
Published
2013
Publisher
Marine Biodiversity Records
Abstract
The false killer whale Pseudorca crassidens is currently documented from only six eastern tropical Atlantic (ETA) range states, five of which are evidenced by strandings, by-catch or skeletal remains rather than at-sea sightings and consequently provide no information on habitat or behaviour. Here we report six false killer whale records from cetacean surveys carried out off Gabon (four records) and Coˆte d’Ivoire (two records) between 2002 and 2012, providing the first at-sea sightings inthose two existing range states. All six sightings were located in continental shelf waters (≤103 m depth) and in relatively nearshore (mean ¼ 13.9 km) habitat. Forty-three false killer whales were photo-identified during three encounters on the Gabonese shelf; seven individuals were matched between 2002 and 2006, including two individuals that were present during all three sightings. Observations included predation of Atlantic sailfish Istiophoms albicans and two occurrences inproximity to humpback whales Megaptera novaeangliae. Whistles recorded during one sighting had simple structure, short duration and a mean fundamental frequency of 7.8 kHz. These are the first verified records of false killer whales using continental shelf waters in the ETA, indicating that the species occupies neritic habitat in the region in addition to its previouslydocumented oceanic habitat. The re-sightings of marked individuals between sightings and years suggest that at least some individuals exhibit a degree of site fidelity to Gabonese shelf waters. Further information on distribution, abundance, movements, population structure and mortality rates are required for effective management of the species in the ETA.

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PUB14939