scholarly journals “Satisficing” and trade-offs: evaluating rebuilding strategies for Greenland halibut off the east coast of Canada

2010 ◽  
Vol 67 (9) ◽  
pp. 1896-1902 ◽  
Author(s):  
David C. M. Miller ◽  
Peter A. Shelton

Abstract Miller, D. C. M., and Shelton, P. A. 2010. “Satisficing” and trade-offs: evaluating rebuilding strategies for Greenland halibut off the east coast of Canada. – ICES Journal of Marine Science, 67: 1896–1902. To be effective, management strategy evaluation (MSE) requires a well-defined procedure for comparing the merits of candidate management strategies. We explore a two-step approach of “satisficing” followed by a trade-off analysis. “Satisficing” (a portmanteau of “satisfy” and “suffice”) is a decision-making procedure that attempts to meet criteria for adequacy, rather than identify an optimal solution. As a case study, we consider the results from a comprehensive MSE for Greenland halibut off the east coast of Canada, carried out under the auspices of the Northwest Atlantic Fisheries Organization. First, we apply satisficing to the results to determine which rebuilding strategies achieve pre-specified thresholds set for imperative performance statistics relating to resource conservation, yield, and stability of the fishery. Next, trade-offs among important, but not necessarily imperative, performance statistics are evaluated for those strategies that pass the satisficing step. For Greenland halibut, a management strategy containing a simple feedback harvest-control rule based on recent trends in survey estimates of abundance satisfices all imperative requirements and provides the best trade-off in other performance statistics. The approach necessitates translating objectives for stock rebuilding and sustainable fisheries into operationally explicit terms and incorporates a priori consideration of stakeholders' concerns.

2014 ◽  
Vol 18 (8) ◽  
pp. 3259-3277 ◽  
Author(s):  
A. P. Hurford ◽  
J. J. Harou

Abstract. Competition for water between key economic sectors and the environment means agreeing allocations is challenging. Managing releases from the three major dams in Kenya's Tana River basin with its 4.4 million inhabitants, 567 MW of installed hydropower capacity, 33 000 ha of irrigation and ecologically important wetlands and forests is a pertinent example. This research seeks firstly to identify and help decision-makers visualise reservoir management strategies which result in the best possible (Pareto-optimal) allocation of benefits between sectors. Secondly, it seeks to show how trade-offs between achievable benefits shift with the implementation of proposed new rice, cotton and biofuel irrigation projects. To approximate the Pareto-optimal trade-offs we link a water resources management simulation model to a multi-criteria search algorithm. The decisions or "levers" of the management problem are volume-dependent release rules for the three major dams and extent of investment in new irrigation schemes. These decisions are optimised for eight objectives covering the provision of water supply and irrigation, energy generation and maintenance of ecosystem services. Trade-off plots allow decision-makers to assess multi-reservoir rule-sets and irrigation investment options by visualising their impacts on different beneficiaries. Results quantify how economic gains from proposed irrigation schemes trade-off against the disturbance of ecosystems and local livelihoods that depend on them. Full implementation of the proposed schemes is shown to come at a high environmental and social cost. The clarity and comprehensiveness of "best-case" trade-off analysis is a useful vantage point from which to tackle the interdependence and complexity of "water-energy-food nexus" resource security issues.


2005 ◽  
Vol 62 (5) ◽  
pp. 841-846 ◽  
Author(s):  
T. Katsukawa

Abstract Spawning-per-recruit (SPR) and yield-per-recruit (YPR) analyses are widely used in stock assessments of exploited fish populations. In decision-making for fisheries management, the trade-off between fisheries production (YPR) and stock reproduction (SPR) is important. The general outputs of SPR and YPR analysis, such as single variate plots with contour lines or optimal harvest strategies estimated by numerical optimization, are inappropriate in obtaining an overview of the trade-off. This paper introduces a diagram that expresses graphically the bivariate trade-off between YPR and SPR. The method was applied to chub mackerel (Scomber japonicus) data, and two management scenarios were compared using the SPR–YPR diagram. Differences between YPR and revenue-per-recruit (RPR) were also considered. The results showed that: (i) current estimated fishing mortality is suggestive of growth-overfishing, and there is room for improving SPR and YPR simultaneously; (ii) increasing the age at first capture is more effective than effort control; (iii) management strategies that maximize landing weight or revenue are significantly different. The management strategy that maximizes landing weight, when considered from the viewpoint of maximizing revenue, results in growth-overfishing.


2019 ◽  
Vol 109 (5) ◽  
pp. 1729-1737
Author(s):  
Yuanyuan Fang ◽  
Ying Zhou ◽  
Zhenxing Yao

Abstract In geophysical applications, solutions to ill‐posed inverse problems Ax=b are often obtained by analyzing the trade‐off between data residue ‖Ax−b‖2 and model norm ‖x‖2. In this study, we show that the traditional L‐curve analysis does not lead to solutions closest to the true models because the maximum curvature (or the corner of the L‐curve) depends on the relative scaling between data residue and model norm. A Bayes approach based on empirical risk function minimization using training datasets may be designed to find a statistically optimal solution, but its success depends on the true realization of the model. To overcome this limitation, we construct training models using eigenvectors of matrix ATA as well as spectral coefficients calculated from the correlation between observations and eigenvector projected data. This approach accounts for data noise level but does not require it as a priori knowledge. Using global tomography as an example, we show that the solutions are closest to true models.


FACETS ◽  
2018 ◽  
Vol 3 (1) ◽  
pp. 338-357 ◽  
Author(s):  
Douglas W. Morris ◽  
Sundararaj Vijayan

Prey individuals possess four basic strategies to manage predation risk while foraging: time allocation, space use, apprehension, and foraging tenacity. But there are no direct tests of theory detailing how spatial strategies change and covary from fine to coarse scales of environmental variability. We address this shortcoming with experiments that estimated space use and vigilance of snowshoe hares while we measured foraging tenacity in artificial resource patches placed in risky open versus safe alder habitat. Hares employed only two of eight a priori options to manage risk. Hares increased vigilance and reduced foraging in open areas as the distance from cover increased. Hares did not differentiate between open and alder habitats, increase vigilance at the coarse-grained scale, or reduce vigilance and foraging tenacity under supplemental cover. Hares were more vigilant in the putatively safe alder than in the purportedly risky open habitat. These apparently paradoxical results appear to reflect a trade-off between the benefit of alder as escape habitat and the cost of obscured sight lines that reduce predator detection. The trade-off also appears to equalize safety between habitats at small scales and suggests that common-sense predictions detailing how prey reduce risk may make no sense at all.


Policy Papers ◽  
2017 ◽  
Vol 2017 (44) ◽  
Author(s):  

This report to the Boards of the International Monetary Fund (IMF) and the World Bank (WB) is the third in a series regarding the evolution of the Medium-Term Debt Management Strategy (MTDS) framework and the associated capacity building efforts. In 2007 the two Boards endorsed the development of the MTDS and ancillary tools, and mandated a program of technical assistance to help countries build capacity in this area. This endorsement and mandate reflect a recognition that sound debt management is critical both to macroeconomic stability and to the development and functioning of the financial sector. The IMF and the WB have collaborated to deliver a large volume of MTDS-based technical assistance to numerous, diverse countries, with a focus on middle- and lower-income countries. Donors have recognized the importance of this work and have been generous in their support. The assistance has taken many forms, including country visits by staff and experts, the delivery of regional training events, and the organization of forums. As documented here, modes of delivery have evolved, with greater emphasis on tailoring to country circumstances, ownership, and coordination within and across agencies in the recipient countries. The report and accompanying annexes describe how capacity building on MTDS has been adapted to keep abreast of country needs. An increasing number of countries have market access (such as through the issuance of Eurobonds or local currency bonds), and face the potential realization of contingent claims, which requires that the MTDS framework consider additional risk factors; more diverse scenarios and market risk metrics; and a wider range of strategies. In many countries, effective capacity building in MTDS was complemented by efforts to strengthen institutions and governance arrangements; debt recording; and government cash management. Linkages with the formulation of annual borrowing plans (ABP) and debt sustainability analysis (DSA) have been strengthened, but more work is needed. Providing a sustained stream of support, rather than one-off missions, often produced better results. Country ownership, often reflected in commitments under IMF- or WB-supported programs, has proven critical to the sustained enhancement of debt management capacity. The value and effectiveness of these capacity building efforts are documented in the report using qualitative and quantitative metrics. The responses from national authorities to a questionnaire on their experience with MTDS technical assistance and the evolution of various quantitative indicators suggest that there were benefits and these were generally sustained. In particular, the majority of countries that had received technical assistance indicated that it helped them to introduce a structured and coherent approach to designing a debt management strategy (DMS) and raise awareness of risks among senior officials and broader stakeholders. Countries also appreciated advice on institutional and governance reforms and integrating debt management into macroeconomic policy formulation and implementation. The observations are supported by case studies detailing how technical assistance was successfully tailored to country needs. It is shown that many recipient countries are now better able to integrate debt management into overall economic policy formulation and adapt their debt management strategies to changing countries’ circumstances. For some, risk exposure indicators have improved even as debt levels have increased. Looking forward, the report suggests that the MTDS framework and modes of delivery should continue to be updated and refined, while maintaining core functions. Some countries will need more sophisticated techniques both to analyze cost-risk trade-offs and to implement their chosen strategy. Others are still in the process of building a solid foundation for debt management. In addition to hands-on trainings, greater use of on-line learning may further enhance effectiveness and efficiency. Building institutional capacity in debt management is a long-term endeavor, often times requiring a more “programmatic” approach, and sustained client ownership. Such an approach would involve diagnosis followed by an actionable reform plan supported by tailored technical assistance. The Boards are asked for their views on priorities in a strategy for future development of capacity building in this area, and how best to ensure that improvements in debt management are sustained.


Author(s):  
Madhusudhan Venkadesan ◽  
Francisco J Valero-Cuevas

We present a numerical exploration of contact transitions with the fingertip. When picking up objects our fingertips must make contact at specific locations, and—upon contact—maintain posture while producing well-directed force vectors. However, the joint torques for moving the fingertip towards a surface ( τ m ) are different from those for producing static force vectors ( τ f ). We previously described the neural control of such abrupt transitions in humans, and found that unavoidable errors arise because sensorimotor time delays and lags prevent an instantaneous switch between different torques. Here, we use numerical optimization on a finger model to reveal physical bounds for controlling such rapid contact transitions. Resembling human data, it is necessary to anticipatorily switch joint torques to τ f at about 30 ms before contact to minimize the initial misdirection of the fingertip force vector. This anticipatory strategy arises in our deterministic model from neuromuscular lags, and not from optimizing for robustness to noise/uncertainties. Importantly, the optimal solution also leads to a trade-off between the speed of force magnitude increase versus the accuracy of initial force direction. This is an alternative to prevailing theories that propose multiplicative noise in muscles as the driver of speed–accuracy trade-offs. We instead find that the speed–accuracy trade-off arises solely from neuromuscular lags. Finally, because our model intentionally uses idealized assumptions, its agreement with human data suggests that the biological system is controlled in a way that approaches the physical boundaries of performance.


2014 ◽  
Vol 11 (1) ◽  
pp. 1343-1388 ◽  
Author(s):  
A. P. Hurford ◽  
J. J. Harou

Abstract. Competition for water between key economic sectors and the environment means agreeing on allocation is challenging. Managing releases from the three major dams in Kenya's Tana River basin with its 4.4 million inhabitants, 567 MW of installed hydropower capacity, 33 000 ha of irrigation and ecologically important wetlands and forests is a pertinent example. This research seeks to identify and help decision-makers visualise reservoir management strategies which result in the best possible (Pareto-optimal) allocation of benefits between sectors. Secondly we seek to show how trade-offs between achievable benefits shift with the implementation of new proposed rice, cotton and biofuel irrigation projects. To identify the Pareto-optimal trade-offs we link a water resources management model to a multi-criteria search algorithm. The decisions or "levers" of the management problem are volume dependent release rules for the three major dams and extent of investment in new irrigation schemes. These decisions are optimised for objectives covering provision of water supply and irrigation, energy generation and maintenance of ecosystem services which underpin tourism and local livelihoods. Visual analytic plots allow decision makers to assess multi-reservoir rule-sets by understanding their impacts on different beneficiaries. Results quantify how economic gains from proposed irrigation schemes trade-off against disturbance of the flow regime which supports ecosystem services. Full implementation of the proposed schemes is shown to be Pareto-optimal, but at high environmental and social cost. The clarity and comprehensiveness of "best-case" trade-off analysis is a useful vantage point from which to tackle the interdependence and complexity of water-energy-food "nexus" challenges.


2009 ◽  
Vol 276 (1664) ◽  
pp. 2093-2101 ◽  
Author(s):  
C. Alonso-Alvarez ◽  
Lorenzo Pérez-Rodríguez ◽  
Jesus T. Garcia ◽  
Javier Viñuela

The immunocompetence handicap hypothesis proposes that testosterone mediates a trade-off between sexual signalling and immunocompetence in males. Such a trade-off could favour the reliability of sexual signals on the basis that testosterone required for signal expression also promotes immunosuppression. However, the immunosuppressive activity of testosterone has not been convincingly demonstrated. We propose that the optimal solution to the testosterone-mediated trade-off should change with age, explaining ambiguous results in the past. Testosterone and ageing would promote two simultaneous immunosuppressive challenges unaffordable for low-quality males. Oxidative stress, as intimately related to ageing and immunosenescence, could contribute to enhance signal reliability. In this context, traits coloured by carotenoids (yellow–red traits) could play a crucial role due to the immunostimulatory and antioxidant properties of these pigments. Here, old and middle-aged male red-legged partridges were treated with testosterone or manipulated as controls. In the presence of high-testosterone levels, middle-aged males increased both circulating carotenoid levels and colour expression, whereas their cell-mediated immunity was not significantly altered. However, in old males, neither circulating carotenoids nor sexual signalling increased when treated with testosterone, but immunosuppression was detected. The link between testosterone and carotenoids could favour the reliability of sexual signals throughout the life.


2012 ◽  
Vol 11 (3) ◽  
pp. 118-126 ◽  
Author(s):  
Olive Emil Wetter ◽  
Jürgen Wegge ◽  
Klaus Jonas ◽  
Klaus-Helmut Schmidt

In most work contexts, several performance goals coexist, and conflicts between them and trade-offs can occur. Our paper is the first to contrast a dual goal for speed and accuracy with a single goal for speed on the same task. The Sternberg paradigm (Experiment 1, n = 57) and the d2 test (Experiment 2, n = 19) were used as performance tasks. Speed measures and errors revealed in both experiments that dual as well as single goals increase performance by enhancing memory scanning. However, the single speed goal triggered a speed-accuracy trade-off, favoring speed over accuracy, whereas this was not the case with the dual goal. In difficult trials, dual goals slowed down scanning processes again so that errors could be prevented. This new finding is particularly relevant for security domains, where both aspects have to be managed simultaneously.


2019 ◽  
Author(s):  
Anna Katharina Spälti ◽  
Mark John Brandt ◽  
Marcel Zeelenberg

People often have to make trade-offs. We study three types of trade-offs: 1) "secular trade-offs" where no moral or sacred values are at stake, 2) "taboo trade-offs" where sacred values are pitted against financial gain, and 3) "tragic trade-offs" where sacred values are pitted against other sacred values. Previous research (Critcher et al., 2011; Tetlock et al., 2000) demonstrated that tragic and taboo trade-offs are not only evaluated by their outcomes, but are also evaluated based on the time it took to make the choice. We investigate two outstanding questions: 1) whether the effect of decision time differs for evaluations of decisions compared to decision makers and 2) whether moral contexts are unique in their ability to influence character evaluations through decision process information. In two experiments (total N = 1434) we find that decision time affects character evaluations, but not evaluations of the decision itself. There were no significant differences between tragic trade-offs and secular trade-offs, suggesting that the decisions structure may be more important in evaluations than moral context. Additionally, the magnitude of the effect of decision time shows us that decision time, may be of less practical use than expected. We thus urge, to take a closer examination of the processes underlying decision time and its perception.


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