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A novel infill sampling criterion is proposed for efficient estimation of the global robust optimum of expensive computer simulation based problems. The algorithm is especially geared towards addressing problems that are affected by uncertainties in design variablesandproblem parameters. The method is based on constructing metamodels using Kriging and adaptively sampling the response surface via a principle of expected improvement adapted for robust optimization. Several numerical examples and an engineering case study are used to demonstrate the ability of the algorithm to estimate the global robust optimum using a limited number of expensive function evaluations. [ABSTRACT FROM AUTHOR]

Forecast errors in budgetary variables are frequent. When systematic, they are a source of concern, as they signal misconduct in fiscal policymaking, undermine the government’s credibility and compromise long-term fiscal sustainability. This paper analyses the characteristics of fiscal forecasting and implementation errors in Italy using real-time data over the period 1998–2009. Several empirical methods are applied in order to identify the features of policymakers’ behaviour in preparing and implementing annual fiscal policy and to discover potential determinants in the formation of the implementation errors. Our results show that implemented budgetary plans systematically fall short one year ahead of ambitious planned adjustments for the main public finance aggregates. Fiscal illusion dominates revenue and GDP forecasting, and preliminary data releases are severely biased estimators of the final data, especially for expenditures. The role of the parliamentary session in driving a severe expenditure drift is confirmed. [ABSTRACT FROM PUBLISHER]

Abstract: The use of drifting fish aggregating devices (FADs) has become the dominant practice in tropical tuna purse seine fishing. However, just as FADs can increase fishing efficiency, their use has been associated with several negative ecosystem impacts, and moves are being made to manage the use of FADs. In the evaluation of potential management options it is important to consider how fishers will respond to the introduction of control measures, which first requires an understanding of fishery and fleet dynamics. This paper addresses this need by characterising the past and present use of FADs in the Indian Ocean tropical tuna purse seine fishery. The paper describes historical trends in fishing practices, summarises spatiotemporal patterns in the use of FADs and establishes and attributes variation in FAD fishing strategies within the fleet. It also provides an overview of current FAD management policies in the Indian Ocean and examines the observed effects of existing measures on the behaviour of the purse seine fleet. Using this comprehensive understanding, the potential impact on the purse seine fleet of a number of plausible FAD management options are discussed and inferences are drawn for the future sustainability of tropical tuna purse seine fishing in the Indian Ocean. [Copyright &y& Elsevier]

The problem of minimizing a quadratic objective function subject to one or two quadratic constraints is known to have a hidden convexity property, even when the quadratic forms are indefinite. The equivalent convex problem is a semidefinite one, and the equivalence is based on the celebrated S-lemma. In this paper, we show that when the quadratic forms are simultaneously diagonalizable (SD), it is possible to derive an equivalent convex problem, which is a conic quadratic (CQ) one, and as such is significantly more tractable than a semidefinite problem. The SD condition holds for free for many problems arising in applications, in particular, when deriving robust counterparts of quadratic, or conic quadratic, constraints affected by implementation error. The proof of the hidden CQ property is constructive and does not rely on the S-lemma. This fact may be significant in discovering hidden convexity in some nonquadratic problems. [ABSTRACT FROM AUTHOR]

The red octopus (Octopus maya) is an endemic species of the Yucatán Peninsula and its fishery is one of the most important along the Atlantic coast of Mexico. Commercial exploitation started in 1949. Since 2002 an index of abundance has been estimated, and this index was used to perform a stock assessment and decision analysis using the Schaefer model. A Bayesian approach was applied to estimate the model parameters and to project the species population under two management scenarios with a constant harvest rate and a positive implementation error. Results suggest that in 1995 the biomass corresponded to 23% of the population carrying capacity (K) and that the current stock is only 14% of K. The population may be depleted and a rebuilding plan might be necessary. In the decision analysis, when the implementation error was included, the Markov Chain Monte Carlo simulations suggested that the current level of exploitation (50% harvest rate) could produce a decreasing trend with the most probable biomass of 9679 t and an expected catch of 7920 t in 2018, and an expected probability of 0.82 of the population being less than 40% of K. On the contrary, a 30% harvest rate would raise the expected catch in 2018 (12,058 t), also reducing the probability of the population being smaller than 40% of K. The inclusion of the implementation error provides a more realistic scenario and represents a more conservative option; therefore, using this type of auxiliary data within a Bayesian framework is recommended for the decision making process. If adopted by Mexican fisheries managers, the approach used in this study could help improve the management of this resource and keep exploitation at sustainable levels.

A special class of recurrent neural network termed Zhang neural network (ZNN) depicted in the implicit dynamics has recently been introduced for online solution of time-varying convex quadratic programming (QP) problems. Global exponential convergence of such a ZNN model is achieved theoretically in an error-free situation. This paper investigates the performance analysis of the perturbed ZNN model using a special type of activation functions (namely, power-sum activation functions) when solving the time-varying QP problems. Robustness analysis and simulation results demonstrate the superior characteristics of using power-sum activation functions in the context of large ZNN-implementation errors, compared with the case of using linear activation functions. Furthermore, the application to inverse kinematic control of a redundant robot arm also verifies the feasibility and effectiveness of the ZNN model for time-varying QP problems solving. [ABSTRACT FROM AUTHOR]

Abstract: A discrete choice model is applied to determine how fishing effort is allocated spatially and temporally by the English and Welsh North Sea beam trawl fleet. Individual vessels can fish in five distinct areas, and the utility of fishing in an area depends on expected revenue measured as previous success (value per unit effort) and experience (past fishing effort allocation), as well as perceived costs (measured as distance to landing port weighted by fuel price). The model predicts fisher location choice, and the predictions are evaluated using iterative partial cross validation by fitting the model over a series of separate time-periods (nine separate time-periods). Results show the relative importance of the different drivers that change over time. They indicate that there are three main drivers throughout the study, past annual effort, past monthly effort in the year of fishing, and fuel price, largely reflecting the fact that previous practices where success was gained are learned (i.e. experience) and become habitual, and that seasonal variations also dominate behaviour in terms of the strong monthly trends and variable costs. In order to provide an indication of the model''s predictive capabilities, a simulated closure of one of the study areas was undertaken (an area that mapped reasonably well with the North Sea cod 2001 partial closure of the North Sea for 10 weeks of that year). The predicted reallocation of effort was compared against realized/observed reallocation of effort, and there was good correlation at the trip level, with a maximum 10% misallocation of predicted effort for that year. [Copyright &y& Elsevier]

The article discusses on spatial closures, like marine protected areas(MPAs), which are prominent tools for ecosystem-based management in fisheries. It states that the adaptive behavior of fishermen, upset the balance of fishing impacts across species. The weakest stock often dominates management attention. It mentions that there is a need to anticipate the behavioral adaptations of fishermen across multiple species in reserve design or to design management systems for adaptations.

The red octopus (Octopus maya) is an endemic species of the Yucatán Peninsula and its fishery is one of the most important along the Atlantic coast of Mexico. Commercial exploitation started in 1949. Since 2002 an index of abundance has been estimated, and this index was used to perform a stock assessment and decision analysis using the Schaefer model. A Bayesian approach was applied to estimate the model parameters and to project the species population under two management scenarios with a constant harvest rate and a positive implementation error. Results suggest that in 1995 the biomass corresponded to 23% of the population carrying capacity (K) and that the current stock is only 14% of K. The population may be depleted and a rebuilding plan might be necessary. In the decision analysis, when the implementation error was included, the Markov Chain Monte Carlo simulations suggested that the current level of exploitation (50% harvest rate) could produce a decreasing trend with the most probable biomass of 9679 t and an expected catch of 7920 t in 2018, and an expected probability of 0.82 of the population being less than 40% of K. On the contrary, a 30% harvest rate would raise the expected catch in 2018 (12,058 t), also reducing the probability of the population being smaller than 40% of K. The inclusion of the implementation error provides a more realistic scenario and represents a more conservative option; therefore, using this type of auxiliary data within a Bayesian framework is recommended for the decision making process. If adopted by Mexican fisheries managers, the approach used in this study could help improve the management of this resource and keep exploitation at sustainable levels. [ABSTRACT FROM AUTHOR]

Powers, J. E., and Brooks, E. N. 2008. Penalties and rewards for over- and underages of catch allocations. – ICES Journal of Marine Science, 65: 1541–1551.Many fisheries are managed using a total allowable catch (TAC) that is subsequently sub-allocated to different fisheries sectors. These allocations are then monitored separately to ensure the adherence of each fishery to its particular allocation quota and to the overall TAC. In some management arenas, there are systems of “payback” where over- and underages are punished or rewarded using particular decision rules. Differences between fishing gear, the sizes and ages of fish being targeted by those gears, and the spatio-temporal distribution of the fishers using those gears can lead to different precision, accuracy, and cost of monitoring the allocation, affecting the probability that an overall management objective is reached. Weaknesses in monitoring may be exploited by user groups in their competition for larger catches and, subsequently, bigger allocations, so differential monitoring precision and accuracy can lead to both short- and long-term reallocations, i.e. a new set of winners and losers. Simulations in a management strategy evaluation framework were used to demonstrate the implications of alternative decision rules regarding payback on conservation and sustainability objectives and rebuilding time frames. The efficacy of the rules under alternative monitoring systems was also examined. Decision rules allowing payback prolong rebuilding (compared with perfect implementation or more precautionary TACs), especially if monitoring is biased (catches misreported) or imprecise. When precision of reported catches was increased and/or bias decreased, better yields and stock abundance resulted. When overages were penalized and underages not rewarded, recovery was achieved earlier. Conversely, policies in which transgressions were ignored and underages rewarded did not perform well. Underreporting by one nation may result in stocks that are well below the stock size conservation standards, yet produce substantial gains in yield for that nation, unless other nations retaliate by underreporting. [ABSTRACT FROM PUBLISHER]

• Large catch uncertainties narrow management possibilities. • This may hinder stock rebuilding, as required management actions become more severe. • Reducing catch uncertainty can be the best means to improve management effectiveness. • Management Strategy Evaluation can explicitly demonstrate the trade-offs. • The process may help identify and boost projects to tackle catch uncertainty. The northern spawning contingent of Western Atlantic mackerel is currently at low biomass and catches are largely underestimated. Catch statistics for Canada are incomplete, and the amount of northern contingent fish caught in the US mackerel fishery is unclear. Our goal was to assess the impact of missing catch on quota management effectiveness and to provide advice for stock rebuilding in the face of large catch uncertainty. As part of a management strategy evaluation (MSE), we assessed how simple harvest control rules (HCRs) performed under different assumptions of catch uncertainty. Results showed that, at present low biomass levels, reducing missing catch was generally more important than the choice among certain HCRs. Canadian undeclared catch would need to be reduced markedly to achieve even short-term rebuilding objectives. To reach long-term rebuilding objectives, the proportion of northern contingent fish caught in the US fishery would also need to be accounted for. We demonstated how an MSE can help inform all involved parties of the trade-off between missing catch and quota magnitude and effectiveness, and provided directions for future developments in management and science. [ABSTRACT FROM AUTHOR]