Near-shore distribution of Heaviside's (Cephalorhynchus heavisidii) and dusky dolphins (Lagenorhynchus obscurus) at the southern limit of their range in South Africa

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dc.contributor.author Elwen, Simon Harvey
dc.contributor.author Thornton, Meredith
dc.contributor.author Reeb, Desray
dc.contributor.author Best, Peter B.
dc.date.accessioned 2010-06-15T11:08:05Z
dc.date.available 2010-06-15T11:08:05Z
dc.date.issued 2010-04
dc.description.abstract Photo-identification surveys over three years along 390 km of coastline north of Cape Town, revealed that Heaviside’s dolphin distribution was consistent between years and higher in areas more exposed to swells and with greater long-term availability of small hake Merluccius capensis (their principal prey). Dusky dolphin sighting rates varied considerably between years, but were generally higher in areas with lower hake availability and sandier shores (mostly straighter coastline). Large groups of 50–200 dusky dolphins were only seen in St Helena Bay, the site of a wind-driven upwelling zone. Heaviside’s dolphins were found in shallower, cooler water than dusky dolphins and were more likely to be seen during brighter phases of the moon (when nocturnal light conditions may influence the vertical migration patterns of prey) and in areas of high hake abundance. Near-shore fishing activity was higher in the northern half of the study area and clustered around harbours. Set netting occurred only at Yzerfontein and St Helena Bay, but due to changes in the industry is currently thought to be a low threat to the population. Interactions between Heaviside’s and dusky dolphins were usually neutral and sympatry appears to be mediated by differences in overall range and the type and size of prey species taken. en
dc.identifier.citation Elwen, SH, Thornton, M, Reeb, D & Best, PB 2010, 'Near-shore distribution of Heaviside's (Cephalorhynchus heavisidii) and dusky dolphins (Lagenorhynchus obscurus) at the southern limit of their range in South Africa', African Zoology, vol. 45, no. 1, pp. 78-91. [http://www.bioone.org/loi/afzo] en
dc.identifier.issn 1562-7020
dc.identifier.uri http://hdl.handle.net/2263/14283
dc.language.iso en en_US
dc.publisher Zoological Society of Southern Africa en_US
dc.rights Zoological Society of Southern Africa. en_US
dc.subject Fisheries interactions en
dc.subject Heaviside's dolphin (Cephalorhynchus heavisidii) en
dc.subject.lcsh Animal population density en
dc.subject.lcsh Cephalorhynchus -- Behavior -- South Africa en
dc.subject.lcsh Dusky dolphin -- Behavior -- South Africa en
dc.subject.lcsh Home range (Animal geography) en
dc.subject.lcsh Lagenorhynchus -- Behavior -- South Africa en
dc.subject.lcsh Predation (Biology) en
dc.title Near-shore distribution of Heaviside's (Cephalorhynchus heavisidii) and dusky dolphins (Lagenorhynchus obscurus) at the southern limit of their range in South Africa en
dc.type Article en


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