Title
On the status of the common bottlenose dolphin Tursiops truncatus in western Africa,with emphasis on fisheries interactions, 1947-2015
Author(s)
Waerebeek, Koen Van; Ofori-Danson, Patrick K.; Debrah, Joseph; Collins, Tim; Djiba, A.; Bilal, Abdellahi Samba Ould
Published
2016
Abstract
A region-wide review indicates that T.truncatus is distributed in coastal (neritic) and offshore (continental slope andpelagic) waters along most of western Africa coasts. No, or very few (<4), records for Sierra Leone, Côte d'Ivoire, Togo,Benin, Nigeria and Equatorial Guinea likely reflect scarcity of survey effort. Inshore-occurring bottlenose dolphins,presumably (semi-)resident, are documented in certain localities from Western Sahara (Dakhla Bay) south to Guinea;also in Gabon, Congo and Angola. Insular stocks are reported from Madeira, Cape Verde Islands, Sao Tomé Island andSt. Helena. As demonstrated for Madeira, some insular communities may not be significantly differentiated geneticallyfrom the surrounding pelagic population. No reliable abundance estimates exist for any range state or offshore area butaround São Tomé 76 individuals were photo-identified. Occasional bycatches are recorded (opportunistically) invirtually all range states. The largest takes, but also the most monitoring effort occurs in Ghana. Extrapolated fromcatches during 2013-2014, an estimated 66 bottlenose dolphins were landed per annum at Dixcove port alone, result ofan ongoing dolphin exploitation. Total national catches are unclear, but sustainability is an issue. Most dolphins arekilled in drift gillnets. Carcasses are typically processed either into cetacean bushmeat for human consumption orapplied as bait in shark fisheries. No geographic variation in group size is apparent, ranging 1-50 ind., with the highermean (44.7) at São Tomé Island. The larger groups generally tend to occur offshore. In deep pelagic or slope waters,bottlenose dolphins frequently associate with short-finned pilot whales. Except for two preliminary studies involvingrespectively Madeira and Senegal/Mauritania, no population identification data have been published. Future researchshould focus on increased fisheries monitoring, the possible existence of distinct morpho- and genotypes mirroringinshore and offshore ecotypes, and abundance estimations.
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PUB15997