Rediscovery of Cameroon Dolphin, the Gulf of Guinea Population of Sousa teuszii (Kükenthal, 1892)

Abstract

Since the 1892 discovery of the Atlantic humpback dolphin Sousa teuszii (Delphinidae), a species endemic to coastal western Africa, from a skull collected in Cameroon, not a single record has been documented from the country or neighbouring countries. Increasing concern about the continued existence of the Gulf of Guinea population of S. teuszii or “Cameroon dolphin” prompted an exploratory survey in May 2011. Shore-based effort, on foot (30.52 km; 784 min), yielded no observations. Small boat-based surveys (259.1 km; 1008 min) resulted in a single documented sighting of ca. 10 (8–12) Cameroon dolphins in shallow water off an open sandy shore near Bouandjo in Cameroon's South Region. The combination of a low encounter rate of 3.86 individuals (100 km)−1 suggesting low abundance and evidence of both fisheries-caused mortality and of habitat encroachment raises concerns about the Cameroon dolphin's long-term conservation prospect. Our results add to indications concerning several other S. teuszii populations that the IUCN status designation of the species as “Vulnerable” may understate its threat level.

New records of Atlantic humpback dolphin in Guinea, Nigeria, Cameroon and Togo underscore fisheries pressure and generalised marine bushmeat demand

“…All humpback dolphin specimens reported here, both freshly dead individuals and cranial material, were encountered in a context of artisanal fisheries, adding weight to the notion that local fisheries constitute the most acute threat to the Atlantic humpback dolphin Van Waerebeek and Perrin 2007;Weir et al 2011;Ayissi et al 2014;Collins 2015). When queried, locals typically admitted that dolphins were cut up and were either consumed or used as bait for shark fishing.…”

“…Historical data. yielded no sightings and no beach-cast specimen remains or strandings (Ayissi et al 2014).…”

“…A first capture of S. teuszii, supported by photographs, was landed by small-scale fishers at Campo, southern Cameroon, on an unspecified date in 2012 (Ayissi et al 2014). An adult specimen landed at Londji fish landing site near Kribi (N02°56.1',E09°54.6') on 22 March 2014 ( Figure 5C) reportedly became accidentally entangled in an artisanal gillnet in the Douala-Edea Fauna Reserve.…”

“…Van Waerebeek et al Since both areas are then separated by less than 150 km of relatively undeveloped coastline of mangroves and sandy beaches, it seems reasonable to assume that gene flow occurs, hence we here define a Guineas stock combining the former Canal do Geba-Bijagos and South Guinea stocks . The humpback dolphins recorded in Togo, Benin and Nigeria are most likely "Cameroon dolphins", S. teuszii communities belonging to the Gulf of Guinea stock, so defined based on the holotype and a 2011 sighting in Cameroon (Ayissi et al 2014).…”

“…A comprehensive status review confirmed nine range states and provisionally identified eight management stocks based on the documented distribution record: Dakhla Bay (Western Sahara), Banc d'Arguin (Mauritania), Saloum-Niumi (Senegal, The Gambia), Canal do Gêba-Bijagos (Guinea-Bissau), South Guinea (Guinea), Cameroon Estuary (Cameroon), Gabon and Angola. Later field work confirmed continued presence in Cameroon after 110 yrs without a single record (Ayissi et al 2011(Ayissi et al , 2014 and provided an improved understanding of occurrence in Gabon (Collins et al 2004(Collins et al , 2010Collins 2012Collins , 2015 and Angola (Weir 2009;Weir et al 2011). Recent records evidenced the occurrence of S. teuszii in the Republic of the Congo (Collins et al 2010;Collins 2012), Benin (Zwart and Weir 2014), Nigeria (this paper) and Togo (this paper) 1 , bringing the count of confirmed range states to 13.…”