Browsing by Subject "life history"

Now showing 1 - 3 of 3
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    Life history traits that predispose South African linefishes to overexploitation
    (2018) Haupt, Meghan; Kerwath, Sven; Parker, Denham; Winker, Henning
    Globally, the status of many fish stocks remains unknown, of which the majority fall under data-limited small-scale fisheries. Management decisions in most of these fisheries are difficult due conflicting objectives and views from fisheries managers and scientists. In South Africa, the traditional boat-based ‘linefishery’ provides such an example of a small-scale, multi-species fishery with a long history. The historical de facto open access nature of this fishery resulted in continuous declines in catches of many linefish species, and in 2000 the fishery was declared to be in a state of emergency. This led to a reduction of up to 70% within the fishery, among other measures, such as introductions of size and bag limits. Assessing the status of linefish species is difficult due to a lack of reliable long-term data for the majority of species. The aims of this study were therefore: (1) to quantify the stock status for all linefish species with available life history and size composition information, (2) compare current and historical stock levels to ascertain if the reduction in effort facilitated any recovery in linefish species and (3) correlate the current stock status estimates to life history traits to identify simple indicators of resilience to exploitation. For this purpose, length frequency data from 1988-1990 and 2008-2010 and biological parameters sourced from literature were used to conduct per-recruit analysis to estimate spawner biomass depletion (SBD) for both time periods. The majority of the 26 species analyzed, (68%) showed improvements in spawner biomass between the two time periods, with 12 species undergoing a change in stock status (i.e. improving from collapsed or overexploited). Specifically, increases in length-at-capture (Lc) as well decreases in fishing mortality (F) facilitated recovery for many species. Asymptotic length (L∞), as well as the ratio between Lc / L∞ and Lc / Lopt (where Lopt is the optimum length) were found to be significantly correlated to spawner biomass depletion. Kruskal Wallis analyses revealed that only movement pattern had a significant relationship to SBD, more specifically, migratory species were significantly more depleted than resident ones. This study identifies simple indicators that, in the absence of conventional stock assessments, provide fisheries managers with a fundamental understanding of a species’ susceptibility to overexploitation – offering another decision making tool for use in data poor fisheries such as the South African linefishery.
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    Survivors narratives of intimate partner violence in Cape Town, South Africa: A life history approach
    (2019) Chikwira, Rene; Boonzaier, Floretta; van Niekerk, Taryn
    Intimate partner violence (IPV) is a problem that is present and pervasive globally and in South Africa. In the South African context, IPV exists within a larger context of high levels of interpersonal violence and violence against women. Understanding the context in which IPV occurs from the perspective of survivors is important for informing effective intervention and prevention programs to counteract its effects. This study explores the life histories of South African women who have experienced IPV. Framed through the lens of intersectionality, it gauges the broader context within which IPV emerges and is sustained, and explores how experiences of IPV are shaped at the intersection of women’s identity markers of race, class and gender. This study is one of a few studies that have used life history methods with women to explore their life contexts and experiences of IPV. Purposive sampling was used to recruit a sample of 11 women based in a Cape Town women’s shelter for abused women and children. Two semi-structured qualitative life history interviews were conducted with each participant. The interviews were transcribed and analysed through thematic narrative analysis, where four noteworthy narrative themes emerged, namely An unsteady and violent beginning, No place called home: A search for belonging and survival, IPV: The unanticipated cost of love and belonging, and Normalisation of IPV experiences: The effects of withdrawal from support. The findings and their relation to existing literature as well as recommendations for future IPV research are discussed. One of the key findings of the study was that the childhood context of the participants was the first point of identifying intersectional oppression and marginalisation that may have shaped a vulnerability to the women’s later experiences of IPV. Another key finding was recognising the value that women place on love and belonging in the context of a difficult, violent and low socioeconomic childhood background, and how this could have an impact on the vulnerability of women to IPV. The use of a life history approach framed by intersectionality thus demonstrated significant benefits in tracking the contextual experiences of women who have experienced IPV. These benefits are of significance because they made it possible to identify points of intervention and prevention of IPV amongst marginalised South African women.
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    The Evolutionary Ecology of Sprouting in Woody Plants
    (2003) Bond, William J; Midgley, Jeremy J
    Woody plants may be killed by severe disturbance or resprout from vegetative tissue. Sprouters can persist at a site through several generations of nonsprouters. Differences in sprouting behavior are therefore important for understanding vegetation dynamics, extinction risks, and woody plant management. Although sprouting appears not to be uniquely correlated with many other intrinsic attributes, such as specific leaf area or breeding systems, a clear correlate is reduced seedling aboveground growth rates from sprouters allocating more to belowground structures. Consequently, sprouters tend to have low seedling recruitment rates, and saplings take longer to reach maturity. Sprouters also tend to have lower seed output than nonsprouters, but comparative studies have seldom taken other trait differences such as plant size into account. Added to these trade-offs between persistence and recruitment, sprouters are often multi stemmed and shorter than related nonsprouters and may be outcompeted by them when disturbances are rare. Since sprouters tend to have long generation times, damped demographic trends, and gene flow across generations, it has been suggested that their speciation rates would be low. The available data, primarily from fire-prone Gondwanan shrublands in South Africa, show no strong differences in speciation rates of related sprouters versus seeders. This indicates that ecological factors are important determinants of the evolution of fire life