Browsing by Author "Mauff, Katya"

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    Behavioural ecology of white sharks carcharodon carcharias in False Bay, South Africa: towards improved management and conservation of a threatened apex predator
    (2014) Kock, Alison Ann; O'Riain, Justin; Griffiths, Charles L; Mauff, Katya
    The coastal waters off South Africa support a significant proportion of the global white shark population, with at least four well-established coastal aggregation sites. How critical these sites are to the southern African and hence global white shark population depends to a large extent, on their levels of residency a nd site fidelity, in relation to potential threats. Here, I attempt to provide such data by studying the annual and seasonal presence of white sharks in False Bay. From 1 April 2004 - 31 December 2007, a total of 68 (46 female, 22 male) sharks, ranging in length from 1.7 to 5 m, were tagged with acoustic transmitters and monitored on an array of 30 receivers, distributed along the Inshore region of False Bay and at Seal Island, for a maximum of 1349 days. I used generalized linear mixed effects models to investigate the effects of season, habitat type, sex, size and time of day on shark presence. Most tagged sharks were immature animals, some of which were detected in the Bay in all months and across all years. In autumn and winter, males and females aggregated around Seal Island, where they fed predominantly on young-of-the-year seals. Sharks, regardless of sex or size, over-dispersed on the South side of the Island at sunrise, where the probability of encountering predator-naïve seals was highest. Shark presence at Seal Island mirrored the spatial distribution of predation around the Island, which was highest on the South side within 400 m of the Island, and at sunrise. In spring and summer, there was marked sexual segregation in presence, with females frequenting the Inshore areas and males seldom being detected in the Bay . Within the Inshore region, female white sharks showed a preference for beach, compared to rocky, mixed and harbour habitats. The preference for beach habitat likely reflects a combination of high prey availability, in addition to an open habitat suitable for detecting and securing prey. Overall, the results confirm False Bay as a critical area for white shark conservation as both sexes, across a range of sizes, show high levels of fidelity to the Bay.
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    Five years of antimalarial resistance marker surveillance in Gaza Province, Mozambique, following artemisinin-based combination therapy roll out
    (Public Library of Science, 2011) Raman, Jaishree; Mauff, Katya; Muianga, Pedro; Mussa, Abdul; Maharaj, Rajendra; Barnes, Karen I
    Antimalarial drug resistance is a major obstacle to malaria control and eventual elimination. The routine surveillance for molecular marker of resistance is an efficient way to assess drug efficacy, which remains feasible in areas where malaria control interventions have succeeded in substantially reducing malaria transmission. Community based asexual parasite prevalence surveys were conducted annually in sentinel sites in Gaza Province, Mozambique from 2006 until 2010, before, during and after antimalarial policy changes to artesunate plus sulfadoxine-pyrimethamine in 2006 and to artemether-lumefantrine in 2008. Genetic analysis of dhfr , dhps , crt , and mdr1 resistant genes was conducted on 3 331 (14.4%) Plasmodium falciparum PCR positive samples collected over the study period from 23 229 children aged 2 to 15 years. The quintuple dhfr/dhps mutation associated with sulfadoxine-pyrimethamine resistance increased from 56.2% at baseline to 75.8% by 2010. At baseline the crt 76T and mdr1 86Y mutants were approaching fixation, 96.1% and 74.7%, respectively. Following the deployment of artemisinin-based combination therapy, prevalence of both these chloroquine-resistance markers began declining, reaching 32.4% and 30.9%, respectively, by 2010. All samples analysed over the 5-year period possessed a single copy of the mdr1 gene. The high and increasing prevalence of the quintuple mutation supports the change in drug policy from artesunate plus sulfadoxine-pyrimethamine to artemether-lumefantrine in Mozambique. As chloroquine related drug pressure decreased in the region, so did the molecular markers associated with chloroquine resistance ( crt 76T and mdr1 86Y). However, this reversion to the wild-type mdr186N predisposes parasites towards developing lumefantrine resistance. Close monitoring of artemether-lumefantrine efficacy is therefore essential, particularly given the high drug pressure within the region where most countries now use artemether-lumefantrine as first line treatment.
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    Multivariate muti-level non-linear mixed-effect models and their application to the modeling of drug-concentration time curves
    (2011) Mauff, Katya; Little, Francesca; Barnes, Karen
    This thesis discusses the techniques involved in the fitting of nonlinear mixed effect (NLME) models. In particular, it looks at the application of these techniques to the analysis of concentration-time data for the aforementioned antimalarial compounds, and details the necessary extensions to the basic modeling process that were required in order to accommodate multiple responses and multiple observation phases (pregnant and postpartum).
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    Residency, habitat use and sexual segregation of white sharks, Carcharodon carcharias in False Bay, South Africa
    (Public Library of Science, 2013) Kock, Alison; O'Riain, M Justin; Mauff, Katya; Meÿer, Michael; Kotze, Deon; Griffiths, Charles
    White sharks ( Carcharodon carcharias ) are threatened apex predators and identification of their critical habitats and how these are used are essential to ensuring improved local and ultimately global white shark protection. In this study we investigated habitat use by white sharks in False Bay, South Africa, using acoustic telemetry. 56 sharks (39 female, 17 male), ranging in size from 1.7-5 m TL, were tagged with acoustic transmitters and monitored on an array of 30 receivers for 975 days. To investigate the effects of season, sex and size on habitat use we used a generalized linear mixed effects model. Tagged sharks were detected in the Bay in all months and across all years, but their use of the Bay varied significantly with the season and the sex of the shark. In autumn and winter males and females aggregated around the Cape fur seal colony at Seal Island, where they fed predominantly on young of the year seals. In spring and summer there was marked sexual segregation, with females frequenting the Inshore areas and males seldom being detected. The shift from the Island in autumn and winter to the Inshore region in spring and summer by females mirrors the seasonal peak in abundance of juvenile seals and of migratory teleost and elasmobranch species respectively. This study provides the first evidence of sexual segregation at a fine spatial scale and demonstrates that sexual segregation in white sharks is not restricted to adults, but is apparent for juveniles and sub-adults too. Overall, the results confirm False Bay as a critical area for white shark conservation as both sexes, across a range of sizes, frequent the Bay on an annual basis. The finding that female sharks aggregate in the Inshore regions when recreational use peaks highlights the need for ongoing shark-human conflict mitigation strategies.
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    Spare the rod and save the child: Assessing the impact of parenting on child behaviour and mental health
    (2015) Ward, Catherine L; Gould, Chandré; Kelly, Jane; Mauff, Katya
    Parenting has a considerable impact on children’s behaviour and mental health. Improving child health and behaviour requires an understanding of the relationship between parenting practices; contexual factors such as parental mental health, intimate partner violence, substance abuse and poverty; and children’s behaviour. In this article the authors report the findings of a survey of parenting and child behaviour in a small rural South African community. The findings show that corporal punishment, the stress of parenting and parental mental health are significantly associated with both children’s internalising (depression and anxiety) and externalising (rulebreaking and aggression) symptoms. Intimate partner violence in the home was also associated with children’s externalising symptoms. These findings imply that parent support and training, and an increase in services to address intimate partner violence and mental health problems, should be prioritised as part of a national violence reduction strategy.
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    Summer at the beach: spatio-temporal patterns of white shark occurrence along the inshore areas of False Bay, South Africa
    (BioMed Central, 2018-05-22) Kock, Alison A; Photopoulou, Theoni; Durbach, Ian; Mauff, Katya; Meÿer, Michael; Kotze, Deon; Griffiths, Charles L; O’Riain, M Justin
    Background Understanding white shark (Carcharodon carcharias) habitat use in coastal areas adjacent to large cities, is an important step when formulating potential solutions to the conservation conflict that exists between humans and large predatory sharks. In this study, we present the findings of a 2.5-year study of white shark occurrence and movement patterns adjacent to the City of Cape Town in False Bay, South Africa, with a focus on spring and summer months. Fifty-one white sharks were monitored annually at three offshore and twelve inshore sites by VR2 acoustic receivers, over 975 days from 1 May 2005 to 31 December 2007. Results Occurrence patterns at inshore sites during spring and summer were analysed using a generalized additive mixed model (GAMM) with a spatial term (longitude, latitude), time of day and year included as explanatory variables for site use. We found that sharks occurred more frequently at inshore sites along the northern and northwestern shores, compared to the rest of the bay, and they transitioned most frequently between four adjacent beach sites that encompass the most popular recreational water use areas in Cape Town. There was significant diel variation, with higher shark occurrence around midday, and a peak in shark occurrence in 2005, when human-shark interactions also peaked. However, we found no effect of shark size on occurrence patterns at inshore sites. Conclusions White sharks showed the highest levels of occurrence at specific inshore sites between Muizenberg and Strandfontein beach, and thus inclusion of these sites within False Bay’s marine protected area (MPA) network or recognition as Ecological or Biological Significant Areas (EBSAs) should be a future consideration. These insights into white shark habitat use at inshore sites in False Bay are important for successfully applying the principles of marine spatial planning (MSP) and for making science-based policy decisions. Furthermore, this information can be used to reduce potential shark-human conflict by incorporating it into future shark safety education campaigns.