The Natural History and Conservation of Indian Ocean Humpback Dolphins (Sousa plumbea) in South African Waters

Plön, Stephanie; Cockcroft, Victor G.; Froneman, P. W.

doi:10.1016/bs.amb.2015.08.005

Cited by 24 publications

(32 citation statements)

References 37 publications

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“…In Richard's Bay, the mortality in bather protection nets continues to contribute to unsustainable loss of humpback dolphins (4.3 individuals or 5–10% of the population per year; Atkins, Cliff, & Pillay, ; Atkins et al, ). It is clear that, owing to its nearshore distribution, the species is highly vulnerable to anthropogenic activities, such as coastal constructions, bather protection nets, acoustic and chemical pollution and fisheries, leading to risks of direct mortality and/or population fragmentation (Plön et al, ). All of these data support the recent up‐listing of the species to ‘Endangered’ in terms of South Africa's Red List for Mammals (Plön et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…Within its global range, the humpback dolphin has probably been most studied in South Africa (Braulik et al, ; Elwen, Findlay, Kiszka, & Weir, ; Plön et al, ; Plön, Cockcroft, & Froneman, ). Studies have been conducted on diet (Barros & Cockcroft, ; Cockcroft & Ross, ), growth rates (Cockcroft & Ross, ), distribution (Conry, ; Durham, ; Karczmarski, Cockcroft, & McLachlan, ; Ross, Heinsohn, & Cockcroft, ), habitat selection (Conry, ; Durham, ; Karczmarski, Cockcroft, & McLachlan, ), abundance (Atkins & Atkins, ; Durham, ; James, Bester, Penry, Gennari, & Elwen, ; Jobson, ; Karczmarski, Winter, Cockcroft, & McLachlan, ; Keith, Peddemors, Bester, & Ferguson, ), behaviour (Atkins, Pillay, & Peddemors, ; Keith, Atkins, Johnson, & Karczmarski, ) and long‐term temporal variation in group size and sighting rates (Koper, Karczmarski, Du Preez, & Plön, ).…”

Section: Introductionmentioning

confidence: 99%

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Indian Ocean humpback dolphin (Sousa plumbea) movement patterns along the South African coast

Vermeulen

Bouveroux

Plön

et al. 2017

Aquatic Conservation

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The Indian Ocean humpback dolphin was recently uplisted to 'Endangered' in the recent SouthAfrican National Red List assessment. Abundance estimates are available from a number of localized study sites, but knowledge of movement patterns and population linkage between these sites is poor. A national research collaboration, the SouSA project, was established in 2016 to address this key knowledge gap. Twenty identification catalogues collected between 2000 and 2016 in 13 different locations were collated and compared.2. Photographs of 526 humpback dolphins (all catalogues and photos) were reduced to 337 individuals from 12 locations after data selection. Of these, 90 matches were found for 61 individuals over multiple sites, resulting in 247 uniquely, well-marked humpback dolphins identified in South Africa.3. Movements were observed along most of the coastline studied. Ranging distances had a median value of 120 km and varied from 30 km up to 500 km. Long-term site fidelity was also evident in the data. Dolphins ranging along the south coast of South Africa seem to form one single population at the western end of the species' global range.4. Current available photo-identification data suggested national abundance may be well below previous estimates of 1000 individuals, with numbers possibly closer to 500. Bearing in mind the poor conservation status of the species in the country, the development of a national Biodiversity Management Plan aimed at ensuring the long-term survival of the species in South Africa is strongly recommended. At the same time, increased research efforts are essential, particularly to allow for an in-depth assessment of population numbers and drivers of changes therein.5. The present study clearly indicates the importance of scientific collaboration when investigating highly mobile and endangered species.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Indian Ocean humpback dolphin (Sousa plumbea) movement patterns along the South African coast

Vermeulen

Bouveroux

Plön

et al. 2017

Aquatic Conservation

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“…The Indian Ocean humpback dolphin ( Sousa plumbea ) has been well researched in South African waters. Several studies have been conducted on its abundance (Atkins & Atkins, ; James, Bester, Penry, Gennari, & Elwen, ; Jobson, ; Karczmarski, Cockcroft, & McLachlan, ; Keith, Peddemors, Bester, & Ferguson, ), distribution (Atkins, Pillay, & Peddemors, ; Durham, ; Karczmarski, Cockcroft et al, ; Karczmarski, Winter, Cockcroft, & McLachlan, ; Melly, McGregor, Hofmeyr, & Plön, ), diet (Barros & Cockcroft, ), genetics (Mendez et al, ), life history (Plön, Cockcroft, & Froneman, ), and health assessment (Cockcroft, ; Lane et al, ; Plön, Albrecht, Cliff, & Froneman, ). This species has recently been recognized as separate from the Indo‐Pacific humpback dolphin ( Sousa chinensis ), based on molecular and morphological studies (Jefferson & Rosenbaum, ; Mendez et al, ).…”

Section: Introductionmentioning

confidence: 99%

Another dolphin in peril? Photo‐identification, occurrence, and distribution of the endangered Indian Ocean humpback dolphin (Sousa plumbea) in Algoa Bay

Bouveroux

Melly

McGregor

et al. 2018

Aquatic Conservation

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1. In South Africa, the humpback dolphin (Sousa plumbea) has been recognized as the most endangered marine mammal, with a low abundance, a discontinuous distribution, and numerous threats. This research was initiated in 2008 to estimate the number of individual humpback dolphins in Algoa Bay, as well as studying their residency patterns and distribution.2. The last boat-based study on humpback dolphins, conducted 24 years ago, formed an important reference against which to compare current findings. This study reveals that since the 1990s the number of identified animals decreased from 70 to 50 individuals, and the mean group size of humpback dolphins has also decreased, from seven to three animals.3. Humpback dolphin behaviour was predominantly that of foraging and travelling, although the overall frequency of foraging still seems to have decreased since early 1990s. 4. Although the species was seen almost all year round, the number of sightings per survey was lowest in January, March, and April. The number of sightings per kilometre surveyed substantially decreased from 0.018 sightings per kilometre in 2008 to 0.004 in 2011, and the number of animals per kilometre also decreased from 0.042 to 0.009. The re-sighting rates were low, ranging from one to eight times, with 52% of identified dolphins seen only once throughout the study period. Only 6% of the individuals were seen more than three times. 5. Reduced humpback dolphin numbers and sighting rates could be indicative of the rise in anthropogenic activities, such as shipping and recreational boating, as well as a rise in pollution from vessels and urban development.6. Conservation strategies, such as a Biodiversity Management Plan for the species, are urgently needed in Algoa Bay, especially in the south-west part of the bay, between Cape Recife and the Port Elizabeth Harbour, where the species occurs most frequently.

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“…The recommended status of Indian Ocean humpback dolphins Sousa plumbea (inhabiting coastal waters from South Africa to the Bay of Bengal) was endangered based on their limited near-shore distribution, continuing decline in habitat quality, likely fragmentation of subpopulations and anthropogenic related mortality (Braulik et al 2015, Plön et al 2015. The most pervasive threats are fisheries bycatch and habitat loss/degradation.…”

Section: Introductionmentioning

confidence: 99%

Net loss of endangered humpback dolphins: integrating residency, site fidelity, and bycatch in shark nets

Atkins¹,

Cantor²,

Pillay³

et al. 2016

Mar. Ecol. Prog. Ser.

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Fisheries bycatch-the incidental catch of non-target species during fishing-is problematic for large marine vertebrates. Bather protection programmes that use gillnets to kill sharks cause the incidental mortality of humpback dolphins (Sousa spp.) potentially impacting the long-term survival of these threatened species. Understanding dolphins' spatial and temporal use of gillnetted areas is critical for designing effective mitigation strategies. We photoidentified dolphins over eight years in a high-bycatch area (Richards Bay, South Africa) to assess the residency, site fidelity, and movement patterns of Indian Ocean humpback dolphins S. plumbea and evaluate how emigration, immigration and mortality rates influence the use of Richards Bay at various temporal scales. Overall, residency was low but site fidelity was high, leading to high population turnover in the short term but low turnover over six months and longer. There was clear individual variation in visitation but no evidence of seasonality. By considering such movements, the net loss of dolphins from the area became evident. While dolphins naturally emigrate from the area, the recognition of several catalogued individuals among the bycaught dolphins indicated that mortality in the shark nets contributes to the permanent loss of both residents and transients. Richards Bay may represent an ecological trap: high site fidelity indicates dolphins perceived the area as ecologically attractive, but high mortality due to shark nets makes it risky. We examined these results relative to gillnet bycatch mitigation methods and recommend that stakeholders collaborate as a mitigation team to prioritise management actions to reduce bycatch without compromising bather safety.

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The Natural History and Conservation of Indian Ocean Humpback Dolphins (Sousa plumbea) in South African Waters

Cited by 24 publications

References 37 publications

Indian Ocean humpback dolphin (Sousa plumbea) movement patterns along the South African coast

Indian Ocean humpback dolphin (Sousa plumbea) movement patterns along the South African coast

Another dolphin in peril? Photo‐identification, occurrence, and distribution of the endangered Indian Ocean humpback dolphin (Sousa plumbea) in Algoa Bay

Net loss of endangered humpback dolphins: integrating residency, site fidelity, and bycatch in shark nets

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