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Kingsbridge, United Kingdom

Zwart S.J.,Africa Rice Center | Weir C.R.,Ketos Ecology | Weir C.R.,University of Aberdeen
Marine Biodiversity Records | Year: 2014

A sighting of four Atlantic humpback dolphins (Sousa teuszii) was recorded and photographed close to the Benin coast on 3 November 2013. This is the first record of the species for Benin, and also represents the first verified record within a 3,065Â km stretch of coast extending from Sierra Leone to Nigeria (encompassing the entire northern coast of the Gulf of Guinea). The sighting supports the possibility that some other potential range states may have remained unconfirmed to date due to a paucity of field research in suitable nearshore habitat rather than an absence of the species. Copyright © Marine Biological Association of the United Kingdom 2014.

Weir C.R.,Ketos Ecology | Weir C.R.,University of Aberdeen
Mammal Review | Year: 2010

The cetacean fauna of the west coast of Africa is poorly described. Therefore, literature on the occurrence of cetacean species in the waters of 13 potential West African range states from the Gulf of Guinea to Angola was reviewed, including sighting, stranding, capture, bycatch and whaling records. At least 28 species of cetacean were documented in the study region, comprising seven baleen whale species and 21 species of toothed whale (including at least 17 delphinid species). Cetaceans could be broadly split into seven ecological categories, based on their distribution. A warm temperate/tropical deep-water cetacean community dominated the study area. Cooler water from the Benguela Current influenced southern Angola (≤16°S latitude) and at least three cetacean species occurred predominantly in this region. Only three or fewer species were confirmed in the waters of Togo, Nigeria, Cameroon and the Democratic Republic of Congo. Seventeen or more species were documented in Ghana, Gabon and Angola, where dedicated cetacean research projects have been initiated in recent years. Angola had the most diverse documented cetacean community: 28 confirmed species. The humpback whale Megaptera novaeangliae was the most widely recorded species, and was documented in 11 (85%) countries. Sperm whales Physeter macrocephalus, Bryde's whales Balaenoptera cf. brydei, bottlenose dolphins Tursiops truncatus and Atlantic spotted dolphins Stenella frontalis were recorded in over half of the countries. © 2010 The Author. Journal compilation © 2010 Mammal Society.

Weir C.R.,Ketos Ecology | Weir C.R.,University of Aberdeen
African Journal of Marine Science | Year: 2015

Ecological data for the Atlantic humpback dolphin Sousa teuszii are scant. Six on-effort Sousa teuszii sightings were recorded during 817.6 km of boat-based effort in the Río Nuñez region of Guinea during October and November 2013. Two incidental sightings were also reported. Groups comprised 1–25 animals. Photo-identification produced a minimum population estimate of 47 animals. Most sightings (n = 5) were located close (<1 km) to shore along a 5.7 km stretch of coast on the west side of Île de Taïdi, primarily over shallow, sand–mud habitat. Two very distinctive individuals were present in all four Taïdi photo-identification encounters, suggesting high site fidelity and stable associations. Two sightings occurred in the outer Río Nuñez Estuary much farther from the coast (5–12 km) but in relatively shallow water (≤15 m) over sand–mud sediment. Focal follows (n = 5: 0.2–3.8 h duration) produced 9.02 h of behavioural data. Travel (51%), foraging (39%) and feeding (9.2%) dominated, with Taïdi dolphins spending more time foraging and feeding than the outer estuary groups. Three individuals had linear-severed dorsal fins consistent with injuries from fishing line. Some management implications of variation in habitat, site fidelity and movements of Sousa teuszii groups are discussed. © 2015 NISC (Pty) Ltd.

Weir C.R.,Ketos Ecology | Weir C.R.,University of Aberdeen
African Journal of Marine Science | Year: 2011

The species richness, spatial distribution, seasonality and interspecific associations of cetaceans in tropical oceanic waters between the Gulf of Guinea and Angola were examined using 5 905.3 h of dedicated survey effort collected from 13 platforms of opportunity (geophysical vessels) between 2004 and 2009, and from incidental records. Most effort (87.8%) was recorded in waters >1 000 m deep. A total of 1 814 on-effort and 1 496 incidental sightings were recorded, comprising 22 species. Physeter macrocephalus and Megaptera novaeangliae were the most frequently sighted cetacean species, with Globicephala macrorhynchus and Stenella frontalis the most frequently sighted delphinids. Five species occurred in both neritic and oceanic waters, while the remainder had exclusively oceanic distributions. The occurrence of P. macrocephalus and M. novaeangliae differed significantly according to depth category. Most species occurred year-round; however, M. novaeangliae exhibited a strong, significant winter and spring occurrence. There were 65 interspecific groups recorded, involving at least 12 species. Mixed schools of G. macrorhynchus and Tursiops truncatus accounted for 55.4% of recorded associations. This extensive year-round dataset adds considerably to the understanding of cetacean distribution in the eastern tropical Atlantic and provides baseline information on which to base cetacean conservation and management in this poorly studied region. © NISC (Pty) Ltd.

Nelms S.E.,University of Exeter | Piniak W.E.D.,Gettysburg College | Weir C.R.,Ketos Ecology | Godley B.J.,University of Exeter
Biological Conservation | Year: 2016

Seismic surveys are widely used in marine geophysical oil and gas exploration, employing airguns to produce sound-waves capable of penetrating the sea floor. In recent years, concerns have been raised over the biological impacts of this activity, particularly for marine mammals. While exploration occurs in the waters of at least fifty countries where marine turtles are present, the degree of threat posed by seismic surveys is almost entirely unknown. To investigate this issue, a mixed-methods approach involving a systematic review, policy comparison and stakeholder analysis was employed and recommendations for future research were identified. This study found that turtles have been largely neglected both in terms of research and their inclusion in mitigation policies. Few studies have investigated the potential for seismic surveys to cause behavioural changes or physical damage, indicating a crucial knowledge gap. Possible ramifications for turtles include exclusion from critical habitats, damage to hearing and entanglement in seismic survey equipment. Despite this, the policy comparison revealed that only three countries worldwide currently include turtles in their seismic mitigation guidelines and very few of the measures they specify are based on scientific evidence or proven effectiveness. Opinions obtained from stakeholder groups further highlight the urgent need for directed, in-depth empirical research to better inform and develop appropriate mitigation strategies. As seismic surveying is becoming increasingly widespread and frequent, it is important and timely that we evaluate the extent to which marine turtles, a taxon of global conservation concern, may be affected. © 2015 The Authors. Published by Elsevier Ltd.

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