Port Elizabeth Museum

Port Elizabeth, South Africa

Port Elizabeth Museum

Port Elizabeth, South Africa
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Kucherera G.T.,Port Elizabeth Museum | Zingoni A.,University of Cape Town
Insights and Innovations in Structural Engineering, Mechanics and Computation - Proceedings of the 6th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2016 | Year: 2016

An understanding of the buckling behaviour of cooling towers in response to changes in shell geometry is of paramount importance. In this paper, a linear eigenvalue buckling analysis is presented for various cooling tower shell geometries. The shell is subjected to increasing wind speed, and the critical wind speed (at which the shell first buckles) and corresponding buckling mode are observed, as the geometric parameters of the shell are varied through the practical range for industrial cooling towers. It is observed the variation of critical wind speed with cooling-tower height is similar to the Euler buckling curve for axially-loaded struts. There appears to be a certain optimum throat-height to total-height ratio (about 0.75) at which the critical wind speed is a maximum. The critical wind speed is observed to vary linearly with the cooling tower thickness, and non-linearly with shell-diameter parameters. The results may be used as a basis for the preliminary design of cooling towers against wind-induced instability. © 2016 Taylor & Francis Group, London.

Kessel S.T.,University of Windsor | Hussey N.E.,University of Windsor | Webber D.M.,Vemco Ltd. | Gruber S.H.,Bimini Biological Field Station | And 4 more authors.
Animal Biotelemetry | Year: 2015

Background: When employing acoustic telemetry to study aquatic species, understanding the functional dynamics of the monitoring system is essential for effective study design, data interpretation, and analysis. Typically, researchers are concerned with maximum effective detection range and consequently tend to employ the largest most powerful tags the study species can carry without considerable energetic burden. In ideal acoustic conditions of low ambient noise environments, low attenuation, and reflective structure, higher powered tags can be detected at larger distances from the receiver, but they can also be subject to the phenomenon 'Close Proximity Detection Interference' (CPDI). This occurs when reflective barriers, such as a calm water surface and/or hard substrate, result in strong transmission echoes that interfere with the transmission sequence. As a result, transmissions in close proximity to the receiver are not effectively decoded and logged. Results: CPDI was assessed from the results of three detection range tests conducted using the Vemco 69kHz telemetry system in three contrasting study systems: a sheltered marine Arctic embayment, a temperate freshwater lake, and an exposed marine sub-tropical reef line. For the Arctic embayment, CPDI was absent with the lower power V9 tag (90% of transmissions received at 55m) but was recorded for the V13 tag and was most prevalent for the highest power V16 tag (18% and 8% of transmissions received at 55m, respectively). Comparing V16 tag detection profiles between study systems, CPDI was evident in the low ambient noise Arctic embayment and temperate freshwater lake (highest transmission proportions recorded at 370 and 207m, respectively) but was absent on the high ambient noise sub-tropical reef line. Functional examples highlight the ways in which CPDI can affect different study designs if not acknowledged or accounted for. Conclusions: CPDI was shown to be the most prominent in low ambient noise study systems and should be considered when choosing tag type/power during study design. If unaccounted for, CPDI could lead to misinterpretation during the analysis of acoustic telemetry data. The identification of CPDI highlights the complexities associated with the functionality of acoustic telemetry systems and supports recommendations for thorough detection range testing. © 2015 Kessel et al.; licensee BioMed Central.

Branch W.R.,Port Elizabeth Museum | Branch W.R.,Nelson Mandela Metropolitan University | Bayliss J.,University of Cambridge | Tolley K.A.,South African National Biodiversity Institute | Tolley K.A.,Stellenbosch University
Zootaxa | Year: 2014

The taxonomic status of recently discovered populations of pygmy chameleons (Rhampholeon) from the northern Mozambique montane isolates of Mt. Chiperone, Mt. Mabu, Mt. Inago and Mt. Namuli are assessed, and compared with the closest geographical congeners, including Rhampholeon platyceps Günther 1893 from Mt. Mulanje, and Rh. chapmanorum Tilbury 1992 from the Malawi Hills, both in southern Malawi. Relationships were examined using morphological features and a phylogenetic analysis incorporating two mitochondrial and one nuclear marker. The phylogeny showed that each montane isolate contained a distinct, well-supported clade of chameleons. Chameleons from the Mozambican montane isolates are within a monophyletic clade inclusive of species from southern Malawi (Rh. platyceps and Rh. chapmanorum). Although some relationships are unresolved, the southern Malawi and Mozambican isolates appear to share their most recent common ancestor with species from the Eastern Arc Mountains and Southern Highlands of Tanzania and Malawi (Rh. moyeri, Rh. uluguruesis, Rh. nchisiensis). Along with Rh. beraduccii and Rh. acuminatus, all are included in the subgenus Rhinodigitum. Sister to this larger clade are species from west/central Africa (Rh. temporalis, Rh. spectrum) and the Rh. marshalli-gorongosae complex from southwest Mozambique and adjacent Zimbabwe. Morphological and molecular results confirm that Brookesia platyceps carri Loveridge 1953 is a junior subjective synonym of Rhampholeon platyceps Günther 1892. Historical records of Rh. platyceps from the Shire Highlands (Chiromo) and the Zomba Plateau, are incorrect and the species is now considered endemic to the Mulanje massif. All of the four newly discovered, isolated populations are genetically and morphologically distinct, and we take the opportunity to describe each as a new species. Rhampholeon (Rhinodigitum) maspictus sp. nov. is restricted to Mt. Mabu and distinguished by its large size, well-developed dorsal crenulations, and bright male breeding coloration; Rhampholeon (Rhinodigitum) nebulauctor sp. nov. is restricted to Mt. Chiperone and distinguished by its small size, weakly-developed dorsal crenulations, and a large rostral process in males; Rhampholeon (Rhinodigitum) tilburyi sp. nov. is restricted to Mt. Namuli and distinguished by its small size, weakly-developed dorsal crenulations, and prominent flexure of the snout in males; and Rhampholeon (Rhinodigitum) bruessoworum sp. nov. is restricted to Mt. Inago and distinguished by its small size, weakly-developed dorsal crenulations, large rostral process in males, and relatively long tail in both sexes. Copyright © 2014 Magnolia Press.

Stanley E.L.,Villanova University | Stanley E.L.,American Museum of Natural History | Bauer A.M.,Villanova University | Jackman T.R.,Villanova University | And 3 more authors.
Molecular Phylogenetics and Evolution | Year: 2011

Girdled lizards (Cordylidae) are sub-Saharan Africa's only endemic squamate family and contain 80 nominal taxa, traditionally divided into four genera: Cordylus, Pseudocordylus, Chamaesaura and Platysaurus. Previous phylogenetic analysis revealed Chamaesaura and Pseudocordylus to be nested within Cordylus, and the former genera were sunk into the later. This taxonomic revision has received limited support due to the study's poor taxon sampling, weakly supported results and possible temporary nomenclatural instability. Our study analyzes three nuclear and three mitochondrial genes from 111 specimens, representing 51 ingroup taxa. Parsimony, likelihood and Bayesian analyses of concatenated and partitioned datasets consistently recovered a comb-like tree with 10, well-supported, monophyletic lineages. Our taxonomic reassessment divides the family into 10 genera, corresponding to these well-supported lineages. Short internodes and low support between the non-platysaur lineages are consistent with a rapid radiation event at the base of the viviparous cordylids. © 2010 Elsevier Inc.

Booth A.J.,Rhodes University | Foulis A.J.,Rhodes University | Smale M.J.,Port Elizabeth Museum | Smale M.J.,Nelson Mandela Metropolitan University
Fishery Bulletin | Year: 2011

This study documents validation of vertebral band-pair formation in spotted gully shark (Triakis megalopterus) with the use of f luorochrome injection and tagging of captive and wild sharks over a 21-year period. Growth and mortality rates of T. megalopterus were also estimated and a demographic analysis of the species was conducted. Of the 23 OTC (oxytetracycline) -marked vertebrae examined (12 from captive and 11 from wild sharks), seven vertebrae (three from captive and four from wild sharks) exhibited chelation of the OTC and f luoresced under ultraviolet light. It was concluded that a single opaque and translucent band pair was deposited annually up to at least 25 years of age, the maximum age recorded. Reader precision was assessed by using an index of average percent error calculated at 5%. No significant differences were found between male and female growth patterns (P>0.05), and von Bertalanffy growth model parameters for combined sexes were estimated to be L∞=1711.07 mm TL, k=0.11/yr and t0= -2.43 yr (n=86). Natural mortality was estimated at 0.17/yr. Age at maturity was estimated at 11 years for males and 15 years for females. Results of the demographic analysis showed that the population, in the absence of fishing mortality, was stable and not significantly different from zero and particularly sensitive to overfishing. At the current age at first capture and natural mortality rate, the fishing mortality rate required to result in negative population growth was low at F>0.004/ yr. Elasticity analysis revealed that juvenile survival was the principal factor in explaining variability in population growth rate.

Hoppe-Speer S.C.L.,Nelson Mandela Metropolitan University | Adams J.B.,Nelson Mandela Metropolitan University | Rajkaran A.,Nelson Mandela Metropolitan University | Bailey D.,Port Elizabeth Museum
Aquatic Botany | Year: 2011

Salinity and water level fluctuations are important factors that influence mangrove species distribution, zonation patterns and succession. Increases in salinity and prolonged inundation are predicted along the south eastern African coast associated with sea level rise due to climate change. This study investigated the response of red mangrove seedlings (Rhizophora mucronata Lam.) to these factors in controlled laboratory experiments. Seedlings were exposed to five salinity treatments (0, 8, 18, 35 and 45. PSU) and a semi-diurnal tidal cycle in an experimental tank set-up. In a separate experiment the effects of different inundation treatments: no inundation, 3, 6, 9. h tidal cycles and continuous inundation (24. h) were investigated. Both morphological and physiological responses of R. mucronata seedlings were measured. There was a decrease in growth (plant height, biomass and leaf production) with increasing salinity. Seedlings in the seawater, hypersaline and no inundation treatments showed symptoms of stress such as increased leaf necrosis ('burn marks'). The highest seedling growth occurred in the low salinity (8. PSU) treatment, but the highest photosynthetic performance and stomatal conductance occurred in the freshwater treatment (0. PSU). The typical response of stem elongation with increasing inundation was observed in the 24. h inundation treatment. Seedlings in the no inundation treatment had significantly lower seedling height compared to the other treatments. © 2011 Elsevier B.V.

Daly R.,Rhodes University | Froneman P.W.,Rhodes University | Smale M.J.,Port Elizabeth Museum | Smale M.J.,Nelson Mandela Metropolitan University
PLoS ONE | Year: 2013

As apex predators, sharks play an important role shaping their respective marine communities through predation and associated risk effects. Understanding the predatory dynamics of sharks within communities is, therefore, necessary to establish effective ecologically based conservation strategies. We employed non-lethal sampling methods to investigate the feeding ecology of bull sharks (Carcharhinus leucas) using stable isotope analysis within a subtropical marine community in the southwest Indian Ocean. The main objectives of this study were to investigate and compare the predatory role that sub-adult and adult bull sharks play within a top predatory teleost fish community. Bull sharks had significantly broader niche widths compared to top predatory teleost assemblages with a wide and relatively enriched range of δ13C values relative to the local marine community. This suggests that bull sharks forage from a more diverse range of δ13C sources over a wider geographical range than the predatory teleost community. Adult bull sharks appeared to exhibit a shift towards consistently higher trophic level prey from an expanded foraging range compared to sub-adults, possibly due to increased mobility linked with size. Although predatory teleost fish are also capable of substantial migrations, bull sharks may have the ability to exploit a more diverse range of habitats and appeared to prey on a wider diversity of larger prey. This suggests that bull sharks play an important predatory role within their respective marine communities and adult sharks in particular may shape and link ecological processes of a variety of marine communities over a broad range. © 2013 Daly et al.

Dicken M.,Rhodes University | Smale M.,Port Elizabeth Museum | Smale M.,Nelson Mandela Metropolitan University | Booth A.,Rhodes University
African Journal of Marine Science | Year: 2013

We present the first quantitative study of the occurrence, size and sex of white sharks Carcharodon carcharias at Bird Island, Algoa Bay. Twenty-two boat trips were made to Bird Island between November 2009 and October 2011 to chum for sharks. A total of 53 sharks was observed over the study period, ranging in size from 1.5 to 4.5 m total length (TL) and with the majority (60.3%) being <3 m TL. The sex ratio of sharks for which sex could be determined was not significantly different from unity. In both study years, sharks were present only in the winter between April and November with a maximum of 1.2 sharks sighted per hour. A zero-altered model, comprising a logistic regression to model presence/absence and a log-normal generalised linear model for abundance, showed that season explained the presence of sharks, peaking in mid-July, with abundance being significantly higher with higher barometric pressure. This study identified Bird Island as an important white shark aggregation site on the east coast of South Africa. These data are crucial not only to improve our understanding of white shark seasonal distribution and biology, but also for the long-term management and conservation of the species in South Africa. © 2013 Copyright NISC (Pty) Ltd.

Daly R.,Rhodes University | Smale M.,Port Elizabeth Museum | Smale M.,Nelson Mandela Metropolitan University
African Journal of Marine Science | Year: 2013

This study evaluated the use of a novel underwater biopsy probe designed to collect muscle and dermal tissue samples from large (170-220 cm total length), free-swimming bull sharks Carcharhinus leucas. The biopsy probe tissue retention rate was 87% after 23 trials, and the mean size of retained tissue was 310 mg (SD 78). Biopsy sampling provided a method t o obtain tissue samples without having to capture or restrain the shark. In all cases retained tissue samples were large enough to conduct stable isotope or genetic analysis. Biopsy sampling used in conjunction with other fishery independent and non-lethal methods may become an increasingly useful tool to investigate shark populations where researchers encounter logistical or conservation-related constraints. © 2013 Copyright NISC (Pty) Ltd.

Conradie W.,Port Elizabeth Museum | Conradie W.,South African Institute For Aquatic Biodiversity
Zootaxa | Year: 2014

Phylogenetic reconstruction using the mitochondrial 16S marker shows the presence of a cryptic species of Cacosternum (Anura: Pyxicephalidae) from the eastern Great Escarpment of South Africa, supporting the Greater Maputaland-Pondola-nd-Albany region of vertebrate endemism. Bioacoustic and morphological characteristics, in conjunction with colouration differences, allow the description of this cryptic species. Tadpoles and details of life history are described. Copyright © 2014 Magnolia Press.

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