Branch Oceans and Coasts

Cape Town, South Africa

Branch Oceans and Coasts

Cape Town, South Africa
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Carpenter-Kling T.,Nelson Mandela Metropolitan University | Dyer B.M.,Branch Oceans and Coasts | Makhado A.B.,Nelson Mandela Metropolitan University | Pistorius P.A.,Nelson Mandela Metropolitan University
Polar Biology | Year: 2017

Plumage aberrations, such as leucism, isabellinism, albinism and melanism, are hereditary and are caused by irregularities in the formation of melanin. This paper presents opportunistic observations of plumage aberrations in 15 Macaroni Penguins Eudyptes chrysolophus at sub-Antarctic Marion Island during 2008–2016. Across five colonies, full and partial leucism, isabellinism and partial melanism were recorded. Plumage aberration in Macaroni Penguins is rarely reported elsewhere in the world. The relatively high number of recorded individuals at Marion Island, in conjunction with limited mixing between global Macaroni Penguin colonies, suggests that a relatively high proportion of the population is entrained with this genetic predisposition. © 2017 Springer-Verlag Berlin Heidelberg

O'Connell C.P.,University of Massachusetts Dartmouth | Andreotti S.,Stellenbosch University | Rutzen M.,Shark Diving Unlimited | MeYer M.,Branch Oceans and Coasts | He P.,University of Massachusetts Dartmouth
Ocean and Coastal Management | Year: 2014

Beach nets are preventative devices that are utilized to minimize the potential interaction between a beachgoer and a predatory shark. One species, the great white shark (Carcharodon carcharias), the focal species for the present study and a protected species in South African waters, is often killed in beach nets within the KwaZulu-Natal (KZN) region. To address the issue of C.carcharias capture in beach nets and to reduce mortality of this species, two related experiments were carried out: the bait experiment and the magnetic-control barrier experiment. Both experiments were aimed to determine the effect of permanent magnets on C.carcharias. During the bait experiment, a total of twenty C.carcharias interacted with the control and magnetic apparatuses. The results indicate that avoidance and feeding behaviors were significantly associated with treatment type, suggesting that permanent magnets had C.carcharias deterrent capabilities. In addition, it was demonstrated that the likelihood of an avoidance behavior on the magnet-associated baits was not significantly correlated with water visibility or conspecific density. For the second experiment, results from stage I of the magnetic-control barrier experiment indicate that behavior was not associated with treatment zo≠ however, stage II indicated that behavior was significantly associated with treatment type. Results from the magnetic-control barrier experiment clearly demonstrate that although a visual barrier, such as the procedural control barrier, may be sufficient to deter C.carcharias from an area, the addition of permanent magnets provide additional successful deterrence of C.carcharias. This study demonstrates that C.carcharias are sensitive to strong permanent magnetic fields; therefore a large-scale experiment with a substantially greater sample size is warranted to investigate the potential of a non-invasive magnetic barrier to replace detrimental beach nets in KwaZulu-Natal, South Africa. © 2012 Elsevier Ltd.

Segre P.S.,Stanford University | Seakamela S.M.,Branch Oceans and Coasts | Meyer M.A.,Branch Oceans and Coasts | Findlay K.P.,Cape Peninsula University of Technology | Goldbogen J.A.,Stanford University
Current Biology | Year: 2017

A central paradigm of aquatic locomotion is that cetaceans use fluke strokes to power their swimming while relying on lift and torque generated by the flippers to perform maneuvers such as rolls, pitch changes and turns [1]. Compared to other cetaceans, humpback whales (Megaptera novaeangliae) have disproportionately large flippers with added structural features to aid in hydrodynamic performance [2,3]. Humpbacks use acrobatic lunging maneuvers to attack dense aggregations of krill or small fish, and their large flippers are thought to increase their maneuverability and thus their ability to capture prey. Immediately before opening their mouths, humpbacks will often rapidly move their flippers, and it has been hypothesized that this movement is used to corral prey [4,5] or to generate an upward pitching moment to counteract the torque caused by rapid water engulfment [6]. Here, we demonstrate an additional function for the rapid flipper movement during lunge feeding: the flippers are flapped using a complex, hydrodynamically active stroke to generate lift and increase propulsive thrust. We estimate that humpback flipper-strokes are capable of producing large forward oriented forces, which may be used to enhance lunge feeding performance. This behavior is the first observation of a lift-generating flipper-stroke for propulsion cetaceans and provides an additional function for the uniquely shaped humpback whale flipper. © 2017 Elsevier Ltd

Makhado A.B.,University of Pretoria | Bester M.N.,University of Pretoria | Somhlaba S.,Forestry and Fisheries | Crawford R.J.M.,Branch Oceans and Coasts
Polar Biology | Year: 2013

Scats of subantarctic fur seals Arctocephalus tropicalis at Marion Island were collected from 1996 to 2,000, to examine temporal variability in the diet, factors affecting the variability and how the diet differed from that of the Antarctic fur seal A. gazella in the same period. For A. tropicalis, 19 prey species, of which 18 were fish and one a cephalopod, were identified in 213 scats. Fish were the main prey, occurring in 98.1 % of scats, whereas the cephalopod was present in only 1.4 % of scats. Amongst fish species, Myctophidae were most abundant, with Gymnoscopelus piabilis, G. fraseri and Electrona carlsbergi being the commonest prey items. Other fish families present in the diet in small numbers were Channichthyidae, Paralepididae, Nototheniidae, Microstomatidae and Notosudidae. Fish eaten ranged in size from Protomyctophum bolini and Krefftichthys anderssoni of standard length (SL) 25 mm to a single Dissostichus eleginoides of SL 249 mm. Differences in the diet existed between summer and winter. However, prey type accounted for most variability in the diet. In previous studies based on scats, a dominance of fish in the diet of A. tropicalis was also found at Possession Island (Iles Crozet), Amsterdam Island and Macquarie Island, but the dominant prey species differed between the various localities, also suggesting that prey availability is a major determinant of diet. At Marion Island, from 1996 to 2000 the diet of A. gazella comprised similar prey to that of A. tropicalis, but the proportional contribution of prey types differed in instances. © 2013 Springer-Verlag Berlin Heidelberg.

Lamont T.,Branch Oceans and Coasts | Lamont T.,University of Cape Town | Barlow R.G.,Bayworld Center for Research and Education | Barlow R.G.,University of Cape Town
African Journal of Marine Science | Year: 2015

During February 2010, studies of primary production (PP) and physiology were conducted at five selected sites in the KwaZulu-Natal (KZN) Bight of the Agulhas ecosystem as part of a programme to elucidate the influence of major physical driving forces and nutrient inputs on the structure and functioning of biological communities. These sites were located in the vicinity of the Durban lee eddy, in the midshelf region of the central part of the bight, off the Thukela Mouth, and to the north and south of Richards Bay. At four of the sites, chlorophyll a ranged from 0.10 to 1.44 mg m–3 and integrated PP ranged between 0.35 and 2.58 g C m–2 d–1. The highest biomass and PP, which were comparable to those observed in a wind-driven upwelling system, were associated with a diatom community observed at the midshelf site, and varied between 0.26 and 4.27 mg m–3 and 7.22 and 9.89 g C m–2 d–1, respectively. Environmental conditions at each of the sites differed substantially and appeared to be influential in initiating and controlling the development and distribution of phytoplankton biomass and production. Phytoplankton adaptation to variable environmental conditions was characterised by a decreased light-limited slope (αB) and increased rate of photosynthesis (Pm) and light saturation (Ek) with elevated temperatures. The converse (increased αB and decreased Pm and Ek) was observed as irradiance levels declined. Generalised additive models indicated that irradiance, temperature and biomass were important variables influencing photosynthetic parameters and photosynthetic rates. © 2015 NISC (Pty) Ltd.

Cury P.M.,Institute Of Recherche Pour Le Developpement | Boyd I.L.,University of St. Andrews | Bonhommeau S.,French Research Institute for Exploitation of the Sea | Anker-Nilssen T.,Norwegian Institute for Nature Research | And 11 more authors.
Science | Year: 2011

Determining the form of key predator-prey relationships is critical for understanding marine ecosystem dynamics. Using a comprehensive global database, we quantified the effect of fluctuations in food abundance on seabird breeding success. We identified a threshold in prey (fish and krill, termed "forage fish") abundance below which seabirds experience consistently reduced and more variable productivity. This response was common to all seven ecosystems and 14 bird species examined within the Atlantic, Pacific, and Southern Oceans. The threshold approximated one-third of the maximum prey biomass observed in long-term studies. This provides an indicator of the minimal forage fish biomass needed to sustain seabird productivity over the long term.

Pretorius M.,University of the Western Cape | Huggett J.A.,Branch Oceans and Coasts | Huggett J.A.,University of Cape Town | Gibbons M.J.,University of the Western Cape
African Journal of Marine Science | Year: 2016

Zooplankton biomass and distribution in the KwaZulu-Natal Bight were investigated in relation to environmental parameters during summer (January–February 2010) and winter (July–August 2010). Mean zooplankton biomass was significantly higher in winter (17.1 mg dry weight [DW] m–3) than in summer (9.5 mg DW m−3). In summer, total biomass was evenly distributed within the central bight, low off the Thukela River mouth and peaked near Durban. In winter, highest biomass was found offshore between Richards Bay and Cape St Lucia. Zooplankton biomass in each size class was significantly, negatively related to sea surface temperature and integrated nitrate, but positively related to surface chlorophyll a and dissolved oxygen. Zooplankton biomass was significantly related to bottom depth, with greatest total biomass located inshore (<50 m). Distribution across the shelf varied with zooplankton size. Seasonal differences in copepod size composition suggest that a smaller, younger community occupied the cool, chlorophyll-rich waters offshore from the St Lucia upwelling cell in winter, and a larger, older community occurred within the relatively warm and chlorophyll-poor central bight in summer. Nutrient enrichment from quasi-permanent upwelling off Durban and Richards Bay appears to have a greater influence on zooplankton biomass and distribution in the bight than the strongly seasonal nutrient input from the Thukela River. © 2016 NISC (Pty) Ltd.

Scharler U.M.,University of KwaZulu - Natal | Ayers M.J.,University of KwaZulu - Natal | de Lecea A.M.,University of KwaZulu - Natal | Pretorius M.,University of the Western Cape | And 5 more authors.
African Journal of Marine Science | Year: 2016

Riverine influences on nearshore oceanic habitats often have detrimental consequences leading to algal blooms and hypoxia. In oligo- to mesotrophic systems, however, nutrient delivery via rivers may stimulate production and even be a vital source of nutrients, as may nutrient supplements from upwelling. We investigated the nutrient content (C, N, P) and stoichiometry of sediment, and several pelagic, benthopelagic and benthic species in the KwaZulu-Natal (KZN) Bight, a narrow shelf area on the south-east coast of South Africa, bordering the Agulhas Current. Three suggested nutrient sources to the bight are the Thukela River in the central region of the bight, upwelling in the northern part and a semi-permanent eddy (Durban Eddy) in the southern part. Elemental content of the various groups studied showed significantly higher values for most groups at the site near the Thukela River. C:P and N:P were highest in the southern part of the bight, and lowest near the Thukela Mouth or at Richards Bay in the north, indicating the latter were the P-richer sites. Sediment organic matter showed lowest elemental content, as expected, and zooplankton stoichiometry was highest compared to all other biotic groups. Environmental heterogeneity played a greater role in organismal C, N and P content and stoichiometry compared to phylogeny, with the exception of the differences in C:P and N:P of zooplankton. From this bight-wide study, the higher elemental content and lower ratios at the Thukela Mouth site supported previous findings of the importance of coastal nutrient sources to the bight ecosystem. Reductions in river flow for water use in the catchment areas may therefore have negative consequences for the productivity of the entire ecosystem. © 2016 NISC (Pty) Ltd.

Kirkman S.P.,Branch Oceans and Coasts | Kirkman S.P.,University of Cape Town | Yemane D.,Forestry and Fisheries | Oosthuizen W.H.,Branch Oceans and Coasts | And 5 more authors.
Marine Mammal Science | Year: 2013

A time series of aerial censuses of Cape fur seal colonies, spanning four decades (1972-2009) and three countries (South Africa, Namibia, and Angola), was analyzed to assess spatio-temporal changes in population numbers. A weighted quantile regression approach was used to estimate trends in pup counts that were used as proxies for numbers of older animals at breeding colonies. There was a 74% increase in the number of breeding colonies over the study period, from 23 in 1973 to 40 in 2009. There was also a significant northward shift in the distribution of the breeding population. This was largely attributable to events in the northern part of the population's range coinciding with Namibia, where seal numbers declined at most colonies in the south of Namibia while several new breeding colonies developed in the northern part of Namibia and one in southern Angola. Despite range expansion and the development of new colonies, the overall size of the population in 2009 was similar to that of the early 1990s, according to the pup count models. Potential mechanisms for the observed changes, and their management implications, are discussed. © 2012 by the Society for Marine Mammalogy.

Fennessy S.T.,Oceanographic Research Institute | Roberts M.J.,Branch Oceans and Coasts | Paterson A.W.,South African Institute For Aquatic Biodiversity
African Journal of Marine Science | Year: 2016

This introductory paper lays the basis for this supplementary issue by briefly presenting the state of knowledge on the KwaZulu-Natal (KZN) Bight at the start of this multi-disciplinary, multi-institutional, ship-based research project that ran from 2009 to 2013. The rationale and aims of the project are also described. The project was a major component of the South African Department of Science and Technology’s African Coelacanth Ecosystem Programme (ACEP), which has been prominent in supporting research on the east coast of South Africa and the wider South-West Indian Ocean. Pivotal to this was the RS Algoa, which was made available for two 30-day surveys (winter and summer) in the KZN Bight by the Department of Environmental Affairs. Although some aspects of the bight ecology are known, much of the research is dated and fragmented, and required refreshing and consolidation in order to produce a platform upon which the understanding of the region’s ecosystem functioning could be established. Much of the oceanographic knowledge is also dated, with no dedicated surveys and significant measurements undertaken since 1989. The overarching theme of the KZN Bight project was to examine the relative importance of sources of nutrients to the central KZN coast and how these are taken up and recycled in the ecosystem, and to describe aspects of the benthic biodiversity, which is poorly described in much of this region. An ambitious project, its accessibility to a ship-based research platform and the diverse scientific skills of the participating scientists allowed considerable success, as reflected in the papers that follow. © 2016 NISC (Pty) Ltd.

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