Diet of the Cape fur seal <i>Arctocephalus pusillus pusillus</i> at the Robberg Peninsula, Plettenberg Bay, and implications for local fisheries

Huisamen, Johan; Kirkman, SP; Lingen, CD van der; Watson, Laurence H.; Cockcroft, Victor G.; Jewell, Rebecca Lucy; Pistorius, Pierre A.

doi:10.2989/1814232x.2012.725524

Cited by 15 publications

(15 citation statements)

References 37 publications

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“…Individuals displayed diel variation, diving to shallower depths at night and reaching the deepest recorded dives for females of any fur seal species during daylight hours ( ca 450 m). These findings are consistent with previously published reports of the Cape fur seal diet from the Benguela comprising primarily schooling fish [18,22,71] and highlight the potential negative consequences of environmental changes affecting the distribution of such prey [72] on foraging effort for the population.…”

Section: Discussionsupporting

confidence: 92%

Dive behaviour and foraging effort of female Cape fur sealsArctocephalus pusillus pusillus

et al. 2019

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While marine top predators can play a critical role in ecosystem structure and dynamics through their effects on prey populations, how the predators function in this role is often not well understood. In the Benguela region of southern Africa, the Cape fur seal (Arctocephalus pusillus pusillus) population constitutes the largest marine top predator biomass, but little is known of its foraging ecology other than its diet and some preliminary dive records. Dive information was obtained from 32 adult females instrumented with dive recorders at the Kleinsee colony (29°34.17′ S, 16°59.80′ E) in South Africa during 2006–2008. Most dives were in the depth range of epipelagic prey species (less than 50 m deep) and at night, reflecting the reliance of Cape fur seals on small, vertically migrating, schooling prey. However, most females also performed benthic dives, and benthic diving was prevalent in some individuals. Benthic diving was significantly associated with the frequency with which females exceeded their aerobic dive limit. The greater putative costs of benthic diving highlight the potential detrimental effects to Cape fur seals of well-documented changes in the availability of epipelagic prey species in the Benguela.

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Section: Discussionsupporting

confidence: 92%

Dive behaviour and foraging effort of female Cape fur sealsArctocephalus pusillus pusillus

et al. 2019

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“…Another important change in the Plettenberg Bay marine ecosystem since the early 2000s is the recolonization and rapid growth of the Cape fur seal ( Arctocephalus pusillus pusillus ) colony on Robberg Peninsula, which forms the southern boundary of the bay [ 69 ]. Increased fur seal abundance may firstly increase inter-specific competition for prey resources [ 64 , 70 ]. Secondly, fur seal presence on the south coast of South Africa is associated with an increase in aggregations of white sharks ( Carcharodon carcharias) , especially during winter [ 71 , 72 ].…”

Section: Discussionmentioning

confidence: 99%

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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“…), red tjor-tjor ( Pagellus bellotii ), sardine ( Sardinops sagax) and octopus ( Octopus spp .) [43,48]. Furthermore, there is likely to have been an increase in the abundance of great white sharks ( Carcharodon carcharias ), that are attracted to seal colonies, in the area.…”

Section: Discussionmentioning

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

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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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Diet of the Cape fur seal Arctocephalus pusillus pusillus at the Robberg Peninsula, Plettenberg Bay, and implications for local fisheries

Cited by 15 publications

References 37 publications

Dive behaviour and foraging effort of female Cape fur sealsArctocephalus pusillus pusillus

Dive behaviour and foraging effort of female Cape fur sealsArctocephalus pusillus pusillus

Abundance of 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

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