Evaluation of a class of possible simple interim management procedures for the Namibian hake fishery

During 1997, considerable scientific differences arose about the status of the Namibian hake (Merluccius capensis and M. paradoxus) resource, and as to whether the hake Total Allowable Catch (TAC) should be substantially decreased or increased. These differences revolved primarily around whether or not abundance estimates from the swept-area trawl surveys by the Norwegian research vessel Dr Fridtjof Nansen should be considered as reliable measures of biomass in absolute (as distinct from relative) terms. The paper relates the computations underlying the Interim Management Procedure (IMP) approach that was put forward at that time as a basis to resolve this impasse. The anticipated performance, in terms of catch and risk of resource depletion, of a number of simple candidate IMPs for the Namibian hake resource is evaluated. The IMPs depend on two parameters, whose values are to be chosen by decision-makers, and adjust the TAC up or down from one year to the next according to whether trends in recent commercial catch rate and survey indices of abundance are positive or negative. Performances are evaluated across the then current wide range argued for resource abundance and status. Trade-offs in performance across the candidates considered are discussed. One of the candidates was subsequently selected by a joint meeting of scientists, industry and Ministry officials in February 1998 and served as the basis for scientific recommendations for the TAC for the hake resource for the following three years. Keywords: abundance, Cape hake, Management Procedure, Namibia, performance, surveys, trade-offAfrican Journal of Marine Science 2001, 23: 357–37

Effective fisheries management with few data: A management procedure approach

Includes bibliographical references.Complex stock assessments which typically rely on a comprehensive set of age or length data are traditionally seen as an essential requirement for sound fisheries management. An alternative process less commonly adopted for the provision of reliable on-going management advice is called the Management Procedure (MP) approach. This approach is pro-active and strategic rather than reactive and tactical, and lends itself well to forecasting and long-term fisheries management. This thesis investigates the application of the MP approach to data-poor as well as data-rich stocks. The majority of fish stocks worldwide are not managed using quantitative analysis as there are not sufficient data on which to base a resource assessment. Often these stocks are relatively "low-value", which renders dedicated scientific management too costly, and a generic approach applicable across a range of stocks is therefore desirable. The aim of the first line of analysis in this thesis is to illustrate the design and testing of some very simple "off-the-shelf" management procedures (MPs) that could be applied to groups of data-poor stocks which share similar key characteristics in terms of demographic parameters. For this initial investigation, a selection of empirical MPs is simulation tested over a wide range of Bayes-like operating models (OMs) representing the underlying dynamics of resources classified as "depleted", in order to ascertain how well these different MPs perform. The moderately data-poor MPs (based on an index of abundance such as provided by a survey or reliable CPUE) perform somewhat better than the extremely data-poor ones (based on the mean length of catch data) as would be expected. Nevertheless the very data-poor MPs perform surprisingly well across the wide range of uncertainty considered for key parameters. The second line of analysis in this thesis focuses on high-value data-rich marine resources: which of the two management paradigms is more suitable where sufficient data for annual stock assessments are readily available? This question is addressed through a retrospective study of management performance over the last twenty years for four North Atlantic fish stocks. The actual assessment advice for these stocks was provided on the basis of complex assessment methods making use of age data. The outcomes are compared to what could have been achieved with much simpler MPs based upon age-aggregated survey indices alone. Even for some of these stocks whose assessments exhibit retrospective patterns, these MPs can achieve virtually equivalent catch and risk performance, with much less inter-annual TAC variability, compared to what actually occurred over the past twenty years. Despite the simplicity of the harvest control rules simulation tested in this thesis, these MPs could well provide the basis to develop generic MPs to manage data-poor stocks, ensuring if not optimal, at least relatively stable sustainable future catches. Moreover, these initial results suggest that simple empirical MPs could provide a defensible, simpler and less costly alternative approach to the provision of scientific management advice for high-value data-rich resources. The advantages of adopting a procedural paradigm for fisheries management purposes are highlighted and rationale is offered as to why it may be prudent (better aligned with the precautionary approach) to adopt an MP approach, even in circumstances where reliable data, expertise and financial support are readily available to perform annual assessments

Torpedo Swimrun Cape Town: understanding athletes, evaluation of race rules and assessing predictors of performance of a novel sport

Aims: The first aim was to describe the characteristics and demands of the Torpedo SwimRun Cape 2019 race. The second aim was to determine predictors of race performance, by using entry, result and questionnaire data. Objectives: The first objective was to explore distributions of age (y), sex, 1km pool swimming time (mm:ss), 5km road running time (mm:ss), competency level (Likert scale), estimated race finishing time (hh:mm), training habits (min/week and sessions/week), background sport (type), equipment used (type), wave selection (athletes select if they want to start in a slow, medium or fast wave)(type), total and segment race times (mm:ss) and questionnaire scores of race participants. The second objective was to analyze segment and race result times, 5km run times, 1km swim times and ocean knowledge questionnaire results. Results: In total, there were 99 participants (288 athletes took part in the race) of which 36% were female and 64% were male. Each team in the Torpedo SwimRun Cape must consist of two athletes. Of the athletes, 53% were entered in male teams, 30% in mixed teams (a male and a female per team) and 17% entered in female teams. The median age was 41 years with an interquartile range (IQR) of 19 years. The mean race time was 174:15 mm:ss (± 29:51 mm:ss). Athletes trained on average 7 sessions/week (IQR 7 sessions/week), and 435 min/week (IQR 345 min/week). The median ocean knowledge score (OKQ) was 9 (IQR 4). Athletes' self-reported current 5km road running time was on average 25:00 mm:ss (IQR 07:41 mm:ss) and their current 1km pool swimming time was 18:00 mm:ss (IQR 07:02 mm:ss). Total race time was significantly associated with current 5km road running time ( = 0.488, p = 0.001), current 1km pool swimming time ( = 0.607, p = 0.001) and OKQ score ( = -0.349, p = 0.003). These three variables were also used to predict total race time. The over-all linear regression model was found to be significant (R2 = 0.514, p = 0.001). Conclusion: The athletes that participated in the Torpedo SwimRun Cape 2019 display a large variance in their training habits, particularly their training loads. It was found that the performance in this SwimRun race was not only dependent on how trained athletes were, but 4 also their ocean knowledge. Ocean knowledge is a learned skill and not necessarily attained by swimming in the ocean more (training open-water swimming was not associated with OKQ score). The OKQ questionnaire showed that better scores were associated with faster total racing time. The model used to predict performance accounted for approximately half of the variation seen in total race time. There is a clear need to further understand how performance is affected in SwimRun races. Repeat studies should be done to investigate different training strategies (also taking an athlete's team partner into account), the effect of various environmental exposures and how different equipment influence racing

Isobuttersäure aus Citrabibrombrenzweinsäure

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Effective fisheries management with few data: a management procedure approach

Complex stock assessments which typically rely on a comprehensive set of age or length data are traditionally seen as an essential requirement for sound fisheries management. An alternative process less commonly adopted for the provision of reliable on-going management advice is called the Management Procedure (MP) approach. This approach is pro-active and strategic rather than reactive and tactical, and lends itself well to forecasting and long-term fisheries management. This thesis investigates the application of the MP approach to data-poor as well as data-rich stocks. The majority of fish stocks worldwide are not managed using quantitative analysis as there are not sufficient data on which to base a resource assessment. Often these stocks are relatively ―low-value‖, which renders dedicated scientific management too costly, and a generic approach applicable across a range of stocks is therefore desirable. The aim of the first line of analysis in this thesis is to illustrate the design and testing of some very simple ―off-the-shelf‖ management procedures (MPs) that could be applied to groups of data-poor stocks which share similar key characteristics in terms of demographic parameters. For this initial investigation, a selection of empirical MPs is simulation tested over a wide range of Bayes-like operating models (OMs) representing the underlying dynamics of resources classified as ―depleted‖, in order to ascertain how well these different MPs perform. The moderately data-poor MPs (based on an index of abundance such as provided by a survey or reliable CPUE) perform somewhat better than the extremely data-poor ones (based on the mean length of catch data) as would be expected. Nevertheless the very data-poor MPs perform surprisingly well across the wide range of uncertainty considered for key parameters. The second line of analysis in this thesis focuses on high-value data-rich marine resources: which of the two management paradigms is more suitable where sufficient data for annual stock assessments are readily available? This question is addressed through a retrospective study of management performance over the last twenty years for four North Atlantic fish stocks. The actual assessment advice for these stocks was provided on the basis of complex assessment methods making use of age data. The outcomes are compared to what could have been achieved with much simpler MPs based upon age-aggregated survey indices alone. Even for some of these stocks whose assessments exhibit retrospective patterns, these MPs can achieve virtually equivalent catch and risk performance, with much less inter-annual TAC variability, compared to what actually occurred over the past twenty years. Despite the simplicity of the harvest control rules simulation tested in this thesis, these MPs could well provide the basis to develop generic MPs to manage data-poor stocks, ensuring if not optimal, at least relatively stable sustainable future catches. Moreover, these initial results suggest that simple empirical MPs could provide a defensible, simpler and less costly alternative approach to the provision of scientific management advice for high-value data-rich resources. The advantages of adopting a procedural paradigm for fisheries management purposes are highlighted and rationale is offered as to why it may be prudent (better aligned with the precautionary approach) to adopt an MP approach, even in circumstances where reliable data, expertise and financial support are readily available to perform annual assessments

Generic MPs for data-poor fisheries: Southern hemisphere collaboration.

The focus of the Southern Hemisphere Collaboration amongst Australia, New Zealand and South Africa is the Management Procedure approach, also known as Management Strategy Evaluation (MSE), as a better basis to manage fisheries. The primary aim of the Collaboration is basic research into the design, development and evaluation of a set of generic Management Procedures (MPs) for data-poor fisheries, for which fishery-specific MPs would be too costly and time-consuming to develop, so as to set the management of such fisheries on a sounder and sustainable basis

Initial investigation of generic management procedures for data-poor fisheries

The vast majority of fish stocks in South Africa are not managed quantitatively as there is not sufficient data (such as an index of abundance) on which to base a resource assessment. In addition, these stocks are relatively “low-value”, which renders dedicated scientific management too costly, and a generic approach is therefore required. The aim of this work is to design and test some very simple “off-the-shelf” management procedures (MPs) that can be applied to groups of data-poor fisheries that share some key characteristics in terms of demographic parameters. For this initial investigation, a selection of empirical MPs is simulation tested on a wide range of operating models (OMs) representing the underlying dynamics of the resource in order to ascertain how well the different MPs perform. While the data-rich MPs perform somewhat better than the data-poor ones, as would be expected, it seems that the very simple data-poor MPs are surprisingly robust to a wide range of uncertainty for key parameters and could well be candidates to manage the South African data-poor stocks, ensuring perhaps not optimum, but at least relatively stable sustainable future catches

Preliminary assessment of the western and south-western Cape Carpenter resource using an age-structured production model

An age-structured production model (ASPM) is used to assess the Carpenter resource off the south western coast of South Africa. The model is fitted to standardized CPUE and length frequency linefish data. Problems encountered when attempting to fit the model to these data are explored. Reasons may include conflicting data, or complexities in the resource dynamics that are not incorporated in the simple density-dependent ASPM dynamics. Plausible parameter estimates are only achieved when fixing or imposing penalty functions for key parameters. However, this leads to deterioration in the fit to the data with systematic trends in the residuals which render results suspect and management advice based on such assessments dubious. Indeed, a management procedure approach may be better suited to circumstances when a “best assessment” is problematic, as seems to be the case here

Complex assessments or simple management procedures for efficient fisheries management: a comparative study

Complex stock assessment methods are data- and expertise-hungry, with the annual updates of catch-at-age data and models typically seen as an essential requirement for sound management. But are the heavy commitments of resources required for this level of annual intervention really necessary to achieve efficient long-term fishery management? This question is addressed through a retrospective analysis of management performance over the last 20 years for four North Atlantic fish stocks. The assessments for two of these stocks have exhibited fairly strong retrospective patterns. The actual assessment advice for these stocks was provided based on complex assessment methods making use of age data. The outcomes are compared with what could have been achieved with much simpler catch control rules based upon age-aggregated survey indices alone. Even for the stocks whose assessments exhibit retrospective patterns, these simple rules can achieve virtually equivalent catch and risk performance, with much less interannual TAC variability, compared with what actually occurred over the past 20 years