A newly discovered wintering ground of humpback whale on the Northwest African continental shelf exhibits a South Atlantic seasonality signature
Van Waerebeek, K.; Djiba, A.; Krakstad, J.-O.; Almeida, A.; Mbye, E.M. (2012). A newly discovered wintering ground of humpback whale on the Northwest African continental shelf exhibits a South Atlantic seasonality signature. International Whaling Commission: [s.l.]. 7 + figures + tables pp.
|
| Keywords |
Megaptera novaeangliae (Borowski, 1781) [WoRMS]
Marine/Coastal |
| Author keywords |
HUMPBACK WHALE; WINTERING GROUNDS; SHELF; SENEGAL; THE GAMBIA; GUINEA-BISSAU; GUINEA |
| Authors | | Top |
- Van Waerebeek, K., more
- Djiba, A.
- Krakstad, J.-O.
|
|
|
| Abstract |
Twenty-one sightings, including 17 confirmed and 4 probable records, of humpback whale were documented during a sighting survey from a fisheries research vessel as platform-of-opportunity, making it the most frequently encountered cetacean on the 100km-wide continental shelf between Conakry and Dakar in the period 21 Oct - 5 Nov 2011. No humpback whales were encountered in the northern stratum from Dakar to Agadir, 6 Nov-15 Dec 2011. Guinea-Bissau, The Gambia and Senegal are newly recognized range states for M. novaeangliae; Guinea is re-confirmed after Bamy et al. (2010). Group sizes ranged 1-6 (mean 1.94; SD 1.20, n=17; median, 2). At least 5 groups (29%) consisted of adult/calf pairs, suggesting a nursing ground. All sightings occurred in shallow water with depth range 22-60m (mean 35.0m; SD 10.13, n=17); 22.7 - 61m for probable-humpback whale groups. Survey effort in deeper, more offshore water was negligible. Sea surface temperatures at sighting positions ranged 25.5-29.0°C (mean 27.34; SD 0.96, n=17). Oceanographic survey design with frequent stations did not allow abundance estimation, however the sum of group sizes was 32 individuals, or 41 including probable humpback whales. The Cape Verde Islands are the only known wintering ground in the NE Atlantic. This survey uncovered a distinct wintering ground in continental shelf waters between Guinea and Senegal. Its seasonal signature, ca. 0.5yr out-of-phase with peak occurrence in Cape Verde Islands, in addition to the presence of neonates is consistent with a South Atlantic stock. Seasonality overlaps with that of the large subpopulations assemblage in the Gulf of Guinea and SE Atlantic, of which we suggest it may comprise its northwestern-most component. Surveys in other seasons are necessary to consolidate insights linking temporal and spatial distribution with hemispheric stock identity and migration. |
|
