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The Cetaceans of Mauritania, West Africa: a concise zoogeographical review with two new species records
Abdellahi Samba Bilal, Moulaye Mohamed Wagne, Abdoulaye Wagué, Abdoul Dia, Koen van Waerebeek,
Volume 5, Issue 1 (3-2023)
Abstract
The exact number of cetacean species present in Mauritanian waters is unknown. A first overview was published only in 1980, the latest in 1998. Yet, published information remains modest compared to, e.g., neighboring Senegal (first review in 1947). The complex oceanography of Mauritanian waters permits a mixed assemblage of cetacean fauna, with the distribution of both cool temperate and (sub) tropical species. In this review, we use our own observations from strandings, bycatches and vessel-based surveys, as well as published and grey literature, to support an updated inventory of cetaceans of Mauritania. This checklist includes two new authenticated species records: Kogia sima (Owen) (Kogiidae) and Lagenodelphis hosei Fraser (Delphinidae). Stenella coeruleoalba (Meyen) (Delphinidae) is verifiably documented for the first time. Further, a first specimen record of Stenella longirostris (Gray) (Delphinidae) is described, as well as second specimen records of Mesoplodon europaeus (Gervais) (Ziphiidae), Steno bredanensis (G. Cuvier) (Delphinidae) and Megaptera novaeangliae (Borowski) (Balaenopteridae). Of 30 reported species, 27 (of six families) are fully supported, while three species lack (accessible) voucher material though probably (P) occur in Mauritania: Balaenopteridae: Megaptera novaeangliae (Borowski), Balaenoptera musculus (Linnaeus), B. borealis Lesson, B. omurai Wada, Oishi and Yamada, B. acutorostrata Lacépède, B. physalus (Linnaeus) and B. brydei Olsen (P); Physeteridae: Physeter macrocephalus Linnaeus; Kogiidae: Kogia sima (Owen) and K. breviceps (Blainville); Delphinidae: Sousa teuszii (Kükenthal), Tursiops truncatus (Montague), Delphinus delphis Linnaeus, Stenella frontalis (G. Cuvier), Stenella attenuata (Gray), Stenella coeruleoalba (Meyen), Stenella longirostris (Gray), Stenella clymene (Gray), Steno bredanensis (G. Cuvier), Peponocephala electra (Gray) (P), Lagenodelphis hosei (Fraser), Grampus griseus (G. Cuvier), Globicephala macrorhynchus Gray, Globicephala melas (Traill) (P), Orcinus orca (Linnaeus) and Pseudorca crassidens (Owen); Ziphiidae: Ziphius cavirostris G. Cuvier, Mesoplodon europaeus and Mesoplodon densirostris (de Blainville); Phocoenidae: Phocoena phocoena (Linnaeus). Finally, we report the first case for continental northwest Africa of tattoo skin disease in a stranded D. delphis.

Status of two Delphinidae, the Atlantic humpback dolphin, Sousa teuszii (Kükenthal) and inshore common bottlenose dolphin Tursiops truncatus (Montagu) on Benin’s coast: an update
Séverin Tchibozo, Koen van Waerebeek, Hong-Yu Lai,
Volume 6, Issue 3 (9-2024)
Abstract
In 2022–2024, we visually surveyed, both slow walking and stationary, the coastal areas near 50 fish landing sites along Benin’s shoreline, undertook a few experimental sorties in small canoe and interviewed 251 locals, mostly artisanal fishermen, seeking information on cetaceans. A total of 120 km was covered for an effective search duration of 83 hrs. The study was especially focused on two coastal cetacean species, the Atlantic humpback dolphin Sousa teuszii (Kükenthal) and the (inshore ecotype) common bottlenose dolphin Tursiops truncatus (Montagu). Although neither species was directly observed during dedicated field research, two sightings of S. teuszii and an unusual entanglement in large plastic debris were reported by members of the public. Furthermore, a new lethal bycatch was photographed in SE Nigeria by a Beninese fisher. Strandings of 10 large whales were documented in the period 2009–2023, including humpback whales Megaptera novaeangliae (Borowski) (n= 5), sperm whales Physeter macrocephalus Linnaeus (n= 3) and unidentified species (n= 2). Eight sightings of live humpback whales, one with a small calf, were reported in July–October 2022. Video recorded by a fisherman provided the first likely evidence of melon-headed whale Peponocephala electra (Gray) for Benin. A live-stranded Gray’s pantropical spotted dolphin Stenella a. attenuata (Gray) was also a first record. The beach and small-boat surveys, as well as fishermen’s perceptions indicate that nearshore occurrence of dolphins in Benin varies from ‘occasional’ to ‘rare’. Entanglement in fishing gear, particularly in ubiquitous beach seines and set and drift gillnets appear to be the main cause of mortality of inshore dolphins, while large plastic debris is newly identified as potentially lethal. The conservation status of inshore T. truncatus, not encountered in Benin for 24 years, may be as dire as that of S. teuszii. Citizen science is playing an increasingly important role in marine mammal information collection in the Gulf of Guinea and western Africa.
 

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