Browsing by Subject "fisheries management"

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    Management strategy evaluation for Greenland halibut (Reinhardtius hippoglossoides) in NAFO Subarea 2 and Divisions 3LKMNO
    (2008) Miller, David C M; Shelton, Peter A; Healey, Brian P; Brodie, William B; Morgan, Joanne M; Butterworth, Doug S; Alpoim, Ricardo; González, Diana; González, Fernando; Fernandez, Carmen; Ianelli, James; Mahé, JeanClaude; Mosqueira, Iago; Scott, Robert; Vazquez, Antonio
    A rebuilding plan for the 2+3KLMNO Greenland halibut stock developed by NAFO Fisheries Commission has been in effect since 2004. Under the plan, ad hoc TAC reduction steps were specified to 2007. The most recent assessment of this stock indicates that the rebuilding plan has been ineffective in initiating any recovery. Fishing mortality is still at high levels and spawner biomass has remained at very low levels. Management Strategy Evaluation provides a way of examining the performance of candidate management strategies with respect to rebuilding the stock. In particular, it allows the robustness of these strategies to be considered relative to alternative operating models of the “real world”, for example the nature of the stock-recruit function for this stock. A preliminary MSE presented at the 2007 NAFO Scientific Council meeting has been updated following the NAFO SC Study Group on Rebuilding Strategies for Greenland Halibut meeting held in Vigo in February 2008. The analysis is carried out in FLR (Fisheries Libraries in R) environment, an open source framework for the development and evaluation of management strategies. A reference set of 20 possible operating models is presented, four of which are examined further. Results are presented in detail for five potential management strategies tested on these four operating models. A suite of performance statistics for this stock are used to assess these management strategies. The results of this MSE exercise are evaluated in the context of the NAFO approach to fisheries management and the potential for further progress with regard to the application of MSE on this stock in general is considered.
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    Modelling human wellbeing for fisheries management: Science, extraction and a politics of nature in the Walvis Bay, Namibia
    (2018) Draper, Kelsey; Green, Lesley; Paterson, Barbara
    Based in Walvis Bay, an industrial fishing town in Namibia on the west coast of southern Africa, this thesis argues that via the logic of neoliberalism, relations between scientific knowledge production, historical labour practices, and political decision-making emerge as a way of managing people and nature in uneven ways. Scientific modelling practices in the form of stock assessments, maintain traction as the technological solution for managing natural resource extraction in Namibia. As such, the dissertation explores the efficacy of computer models in the industrial fishing sector and considers how breakdowns between the scientific, social, and political knowledge worlds can be usefully brought into the conceptual model of the fishery for management. With a shift towards a more inclusive management framework that considers the policy issues as well as translating broad goals into measurable objectives, comes a shift in the logic of what fisheries management is meant to mediate and achieve. The logic is no longer as straightforward as producing an estimate of the amount of fishable biomass, but now must account for market conditions, changing technologies for fishing, and a changing climate and ecology. The human dimension is framed around the concept of wellbeing which in fisheries management emerges as an umbrella term for the social world that is reduced through the logic of neoliberalism to the measurable, enumerable, and indexable social and political implications of the use of Namibia’s natural resources. As one of few ethnographies of Namibia and the only one thus far to address the fisheries sector as a site of study, this dissertation investigates the increased dependence on scientific models in the Namibian hake fishery despite declining fish stocks and increased urban poverty and inequalities. The research contributes to the limited studies done on the political economy of Namibia and the rise of fish as national resource in the postcolony. It investigates the relations at risk in everyday life in Walvis Bay and re-imagines the framing of humans and nature for transformative practices of environmental and economic justice.
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    A spatial- and age-structured assessment model to estimate the impact of illegal fishing and ecosystem change on the South African abalone Haliotis midae resource
    (National Inquiry Services Centre, 2010) Plagányi, Éva E; Butterworth, Doug S; ;
    The management of abalone stocks worldwide is complicated by factors such as illegal fishing combined with the difficulties of assessing a sedentary (but not immobile) resource that is often patchily distributed. The South African abalone Haliotis midaefishery is faced with an additional problem in the form of a relatively recent movement of rock lobsters Jasus lalandii into much of the range of the abalone. The lobsters have heavily reduced sea urchin Parechinus angulosus populations, thereby indirectly negatively impacting juvenile abalone which rely on the urchins for shelter. A model is developed for abalone that is an extension of more standard age-structured assessment models because it explicitly takes spatial effects into account, incorporates the ecosystem change effect described above and estimates the magnitude of substantial illegal (‘poached’) catches. The model is simultaneously fitted to catch per unit effort and Fishery-Independent Abalone Survey abundance data, as well as to several years of catch-at-age (cohort-sliced from catch-at-size) data for the various components of the fishery and different spatial strata. It constitutes the first quantitative approach applied to the management of this commercially valuable resource in South Africa and has provided a basis for management advice over recent years by projecting abundance trends under alternative future catch levels.