Cetacean strandings in Ghana appear to be becoming more common. Whales washing ashore may be due to ship strike, population dynamics, or an increase in human coverage and reporting. There are at least 28 species of cetaceans — seven baleen whales and 21 toothed whales — in the Gulf of Guinea, of which Ghana’s coast covers 550 km from Aflao to Axim. Scientific approaches to cetacean diversities have not been taken until recently, and 18 species were confirmed during researches.
Types of whales Whales in Ghanaian marine environment belong to species of families Ziphiidae (beaked whales), Physeteridae (sperm whales) and Kogiidae (pygmy sperm whales). 'Dolphins', and other species recorded along western African waters but not within Ghanaian waters such as blue whales, bryde's whales, and minke whales are not listed below. Most common of dolphins along Ghanaian waters include Atlantic humpback dolphins and common bottlenose dolphins.
Melon-headed whales Melon-headed whales are accidentally caught in Ghana waters. Specimens have been landed in Shama in 1994 and four in Dixcove in 2000 and 2002. An adult-sized pygmy killer whale landed at Dixcove in December 2007 is the first documented record in the Gulf of Guinea.Van Waerebeek K, Ofori-Danson PK, Debrah J (2009). The cetaceans of Ghana: a validated faunal checklist. West African Journal of Applied Ecology 15, 61–90 Status is unknown but, as elsewhere, pygmy killer whales are probably rare.
False killer whales Records of false killer whales in Ghana is not abundant while the species regularly appears in the Gulf waters.
Pilot whales Short-finned pilot whales seem to be common in Ghana marine waters, and also occur off the coast of Ivory Coast.(Cadenat, 1959)World Register of Marine Species Short-finned pilot whales are irregular by-catch victims in drift gill nets off Ghana (3.5% of cetacean catches,Ofori-Danson PK, Van Waerebeek K, Debrah S (2003). A survey for the conservation of dolphins in Ghanaian coastal waters. Journal of the Ghana Science Association 5, 45–54.) and was landed at Shama, Axim and Dixcove. Most specimens are too big to haul onboard artisanal fishing boats and are towed to port. The Vridi specimen was harpooned for research purposes.Cadenat (1959) World Register of Marine Species A single skeletal specimen was known for Ghana and was probably collected in 1956.
Killer whales Killer whales are present in Gulf of Guinea waters although population size is not considered in great numbers. A killer whale was harpooned some 15-20 nm south of Abidjan in 1958 but the animal sank. This shows that killer whales are present in the West African marine waters. Observers on industrial tuna purse-seiners reported a few sightings off the coast of Liberia, Ivory Coast and Ghana.(Hammond and Lockyer, 1988). Distribution of killer whales in the eastern North Atlantic. Rit Fiskideildar 11, 24–41 The first record in Ghana comprises three false killer whales landed at Apam in 2003. Skulls were collected from a false killer whale stranded near Assini, Ivory Coast, in 1970 (van Bree, 1972) and from a specimen in Benin.(Van Waerebeek et al, 2001; Tchibozo and Van Waerebeek, 2007)
Cuvier's beaked whale Cuvier's beaked whale (Ziphius cavirostris) Offshore Cuvier's beaked whale is a cosmopolitan ziphiid found in pelagic tropical to warm temperate waters. A juvenile landed at Axim in 1994 is the first documented beaked whale in the Gulf of Guinea. The status of Cuvier’s beaked whale is unknown, but no threats are identified. The single capture in Ghana among hundreds of other small cetaceansDebrah JA, Ofori-Danson PK, Van Waerebeek K (2010). An update on the catch composition and other aspects of cetacean exploitation in Ghana. IWC Scientific Committee document SC/62/SM10, Agadir, Morocco, Jun 2010 suggests that impact from bycatch is probably negligible.
Sperm whales In Ghana, a dwarf sperm whale was taken by fishermen from Apam in 1998. Two unidentified Kogia sp. were landed, one at Shama in 1994 and another at Apam in 2003. Very little information is available on sperm whales in the Gulf of Guinea, however females and juveniles are believed to be present throughout the year beyond the continental shelf. This is because two dead sperm whales were washed ashore, first near Accra in 1994 and a second at Dixcove in 2002.
Humpback whale Irvine 1947A. B. Irvine, M. D. Scott (1987) “Social Structure in Migrating Humpback Whales (Megapteranovaeangliae).” recorded a possible humpback whale at Prampram in September 1938. Van Waerebeek and Ofori-Danson (1999)Van Waerebeek K, André M, Sequeira M et al.(1999). Spatial and temporal distribution of the minke whale Balaenoptera acutorostrata Lacépède 1804 in the southern Northeast Atlantic and the Mediterranean Sea, with comments on stock identity. Journal of Cetacean Research and Management 1, 223–37. first confirmed the species from Ghana based on a fresh neonate stranded at Ada in September 1997. An adult-sized humpback whale stranded at Ada Foah in October 2006. Humpback whales are regularly sighted inshore from the Dixcove Castle, from September till December. A neonate stranded in Lomé, Togo, in August 2005.Tchibozo S, Van Waerebeek K (2007). La baleine à bosse et le lamantin d’Afrique, des potentielles ressources de tourisme de la nature au Bénin. Poster presentation, WATCH Symposium; 16–20 Oct 2007, Adeje, Tenerife, Spain Rasmussen et al. (2007)Rasmussen, K., D. M. Palacios, J. Calambokidis, M.T. Saborío, L. Dalla Rosa, E. R. Secchi, G. H. Steiger, J. M. Allen & G. S. Stone 2007. Southern Hemisphere humpback whales wintering off Central America: insights from water temperature into the longest mammalian migration. Biology Letters 3: 302-305. encountered several pods including a mother and possible newborn calf in Ghanaian waters in October 2006. From the presence of humpback whales exclusively from early August till late November, and the frequent observations of neonates and ‘competitive groups’, it is evident that the continental shelf of Benin, Togo, Ghana, and western Nigeria hosts a breeding/calving population with a Southern Hemisphere seasonality,Van Waerebeek K (2003). A newly discovered population of humpback whales in the northern Gulf of Guinea. CMS Bulletin 18, 6–7. referred to as the ‘Gulf of Guinea stock’. Its parametric distribution suggests it may be related to the IWC-defined breeding stock ‘B’ from central-west Africa.(International Whaling Commission (1997) Journal of Cetacean Research and Management: Special Issue 3 Mother and calf pairs have been sighted exclusively near shore in Benin, sometimes just beyond the surf-zone. The westernmost authenticated record is a stranding at Assini Mafia, eastern Ivory Coast in August 2007.Tchibozo S, Van Waerebeek K (2007). La baleine à bosse et le lamantin d’Afrique, des potentielles ressources de tourisme de la nature au Bénin. Poster presentation, WATCH Symposium; 16–20 Oct 2007, Adeje, Tenerife, Spain (Van Waerebeek et al, 2007) For many years, small-scale, seasonal humpback whale-watching sorties have been conducted from the ports of Sekondi-Takoradi, Lomé and Cotonou.Van Waerebeek K, Tchibozo S, Montcho J et al.(2001). The Bight of Benin, a North Atlantic breeding ground of a Southern Hemisphere humpback whale population, likely related to Gabon and Angola substocks. IWC Scientific Committee document SC/53/IA21; Jul 2010, London. The breeding stock off Gabon and Angola is the subject of longterm dedicated studies.Best PB (2007) Whales and Dolphins of the Southern African Subregion. Cambridge University Press, Cape Town, South Africa Possibly up to 10% of world population of humpbacks migrate into Gulf of Guinea.
No abundance estimate is available for the Bight of Benin population, but the encounter rate in October 2000 was approximately 5.9 humpback whales per 100 km surveyed (0.109/nautical mile) .Van Waerebeek K, Tchibozo S, Montcho J et al. (2001). The Bight of Benin, a North Atlantic breeding ground of a Southern Hemisphere humpback whale population, likely related to Gabon and Angola substocks. IWC Scientific Committee document SC/53/IA21; Jul 2010, London The reported neonates stranded in unknown circumstances of natural and anthropogenic causes are possible. At least some humpback whale strandings in the area are thought to be animals killed in vessel collisions, which may be far more common in African waters than scarce reports suggest.(Félix and Van Waerebeek, 2005; Van Waerebeek et al, 2007) Humpback whales near Cotonou’s harbour entrance and crossing the main shipping lanes, incur obvious risk. The individual that stranded at Assini Mafia was reported with external trauma consistent with a propeller hit.Tchibozo S, Van Waerebeek K (2007). La baleine à bosse et le lamantin d’Afrique, des potentielles ressources de tourisme de la nature au Bénin. Poster presentation, WATCH Symposium; 16–20 Oct 2007, Adeje, Tenerife, Spain.
About five of the whales which died are hunchbacks which were stranded in Ghanaian waters. Ghana’s coast forms part of the distribution range of a ‘Gulf of Guinea’ humpback whale breeding stock with estimated population at over 10,000 individuals.
Paths of whales Ghana is on a path of migration for whales heading from South Africa to the waters off Britain and with the current flowing east, whatever killed the whales could be off the coast of Ivory Coast or further west. Some whales from the eastern North Atlantic migrate to the tropical coast of western Africa and the Cape Verde Islands Various methods are used including satellite tags which can track whale movements in near real time. It is not known why humpback whales migrate although possible suggestions include predator avoidance and the energetic benefits of warm water during the winter when food production is low in the feeding grounds. Swimming off the coast of Africa, humpback whales encounter more than warm waters for mating and bearing young, according to a new study led by the Wildlife Conservation Society (WCS). They also encounter offshore oil rigs, major shipping routes and potentially harmful toxicants.
Death of whales
Most of the deaths of the whales have occurred at the coast of the Western Region of Ghana and raised fears that it was the oil drilling that is responsible for the deaths. Since the discovery of oil in 2007 some environmentalists are skeptical whether oil and gas will be handled judiciously to avoid environmental degradation.Paul Collier (2012), One Year of Oil and Gas production in Ghana. Speech made at University of Ghana New Year School Decomposed whale carcasses have been washing onto beaches in western region making environmental groups worried the country's growing petroleum industry may be killing marine life. Local people count a total of 20 dead whales discovered along Ghana's coastline in the last four years, including at least eight since September 2013. Whales are mammals and what kills them is still unresolved.
Causes of death of whales Speculations on the causes of death have generated heated arguments. Some Ghanaians believe that with the start of the exploration of oil and gas in 2007 to 2010 eleven whales have died within three years. They believe that seismic air guns used for oil exploration generate so much noise that if a whale goes deaf it cannot survive.
The academia is not sure of the causes of death of the whales. "It's definitely unusual. But what may be the cause we can't put our finger on," said A.K. Armah,https://www.google.com/ALeqM5gTSRM-FH32Uks_jAvrmzRdnr4esA a lecturer at the University of Ghana, who studies marine life.