Distribution and habitat use of Indo-Pacific bottlenose dolphins <i>Tursiops aduncus</i> along the south coast of South Africa

Vargas-Fonseca, O. Alejandra; Kirkman, SP; Conry, Danielle; Rishworth, GM; Cockcroft, Victor G.; Pistorius, Pierre A.

doi:10.2989/1814232x.2018.1547221

Cited by 8 publications

(11 citation statements)

References 46 publications

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“…Ninety-seven kilometres of the coastline of the study area is within MPAs, namely the Goukamma, Robberg and Tsitsikamma MPAs. There are two main dolphin hotspots in this area, namely the Goukamma MPA and the Plettenberg Bay area [23]; both areas are characterized by sandy shores and gentle slopes. The stretch between Goukamma to Robberg MPA and Tsitsikamma MPA is largely uninhabited (by humans) with exposed rocky coasts and steeper gradients.…”

Section: Methodsmentioning

confidence: 99%

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Estimates of abundance and change in abundance of the Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa

Vargas-Fonseca¹,

Kirkman²,

Oosthuizen³

et al. 2019

Preprint

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We investigated the abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa, from the Goukamma Marine Protected Area (MPA) to the Tsitsikamma MPA, between 2014 and 2016. During this period, 662.3h of boat-based photo-identification survey effort was carried out, and the sighting histories of 817 identified individuals were used to estimate abundance using mark-recapture modelling. The selected open population model (POPAN) provided an estimate of 2,295 individuals (95% CI: 1,157-4,553) for the entire study area. A model estimate was produced for a subset of the study area, Plettenberg Bay, which could be compared with a past estimate for this location (2002-2003). The comparison suggested a 72.3% decrease in abundance, from 6,997 (95% CI: 5,230-9,492) in 2002-2003 to 1,940 (95% CI: 1,448-2,600) in 2014-2016. The decline in abundance was supported by a 72% reduction in mean group size for Plettenberg Bay between the periods. It is essential to be able to assess abundance changes at other locations to inform revision of T. aduncus conservation status in South Africa.

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Section: Methodsmentioning

confidence: 99%

“…Bi-monthly boat surveys were conducted between March 2014 and February 2016. At least two experienced observers were present during surveys which were performed at a constant speed of approximately eight knots (see [23] for further information on study area, survey design and data collection procedures).…”

Section: Methodsmentioning

confidence: 99%

Estimates of abundance and change in abundance of the Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa

Vargas-Fonseca¹,

Kirkman²,

Oosthuizen³

et al. 2019

Preprint

Self Cite

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“…There are two main dolphin space-use hotspots in the Goukamma MPA and the Plettenberg Bay area [28]; both characterized by sandy shores and gentle slopes. Coastal development within the study area is largely limited to the two half-heart bays, Buffels Bay (10 km from Knysna) and Plettenberg Bay.…”

Section: Plos Onementioning

confidence: 99%

“…Surveys in Sections 1, 2 and 3 were conducted using chartered vessels (7.9 m) equipped with two outboard engines (115 to 150 hp). For Sections 4 and 5, a rigid inflatable boat (5.5 m or 7.6 m) equipped with two outboard engines (70 hp or 100 hp) was used [28].…”

Section: Plos Onementioning

confidence: 99%

“…Once dolphins were located, they were approached at low speed so that the species, GPS location, group size, group composition and behaviour could be recorded, and to allow photographs of the dorsal fins of dolphins to be taken. After encounters, survey effort was usually resumed on the transect near where dolphins were initially encountered [28].…”

Section: Plos Onementioning

confidence: 99%

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Abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa

Vargas-Fonseca

Kirkman²,

Oosthuizen

et al. 2020

PLoS ONE

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Coastally distributed dolphin species are vulnerable to a variety of anthropogenic pressures, yet a lack of abundance data often prevents data-driven conservation management strategies from being implemented. We investigated the abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa, from the Goukamma Marine Protected Area (MPA) to the Tsitsikamma MPA, between 2014 and 2016. During this period, 662.3h of boat-based photo-identification survey effort was carried out during 189 surveys. The sighting histories of 817 identified individuals were used to estimate abundance using capture-recapture modelling. Using open population (POPAN) models, we estimated that 2,155 individuals (95% CI: 1,873-2,479) occurred in the study area, although many individuals appeared to be transients. We recorded smaller group sizes and an apparent decline in abundance in a subset of the study area (Plettenberg Bay) compared to estimates obtained in 2002-2003 at this location. We recorded declines of more than 70% in both abundance and group size for a subset of the study area (Plettenberg Bay), in relation to estimates obtained in 2002-2003 at this location. We discuss plausible hypotheses for causes of the declines, including anthropogenic pressure, ecosystem change, and methodological inconsistencies. Our study highlights the importance of assessing trends in abundance at other locations to inform data-driven conservation management strategies of T. aduncus in South Africa.

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Distribution and habitat use of Indo-Pacific bottlenose dolphins Tursiops aduncus along the south coast of South Africa

Vargas-Fonseca

Kirkman

Conry

et al. 2018

African Journal of Marine Science

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Distribution and habitat use of Indo-Pacific bottlenose dolphins Tursiops aduncus along the south coast of South Africa

Cited by 8 publications

References 46 publications

Estimates of abundance and change in abundance of the Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa

Estimates of abundance and change in abundance of the Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa

Abundance of Indo-Pacific bottlenose dolphins (Tursiops aduncus) along the south coast of South Africa

Distribution and habitat use of Indo-Pacific bottlenose dolphins Tursiops aduncus along the south coast of South Africa

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