A simple approach for dealing with dynamics and uncertainty in fisheries with heterogeneous resource and effort distribution

2004 ◽  
Vol 55 (3) ◽  
pp. 249 ◽  
Author(s):  
J. C. Seijo ◽  
E. P. Pérez ◽  
J. F. Caddy
Keyword(s):  
Risk Aversion ◽  
Negative Binomial ◽  
Management Strategies ◽  
Spatial Allocation ◽  
Surf Clam ◽  
Spatially Distributed ◽  
Imperfect Knowledge ◽  
States Of Nature ◽  
Allocation Decisions ◽  
Different Levels

Most fisheries models are based on dynamic pool assumptions. For sedentary and sessile species, these assumptions are inadequate, because they are spatially distributed in patches that vary in size, density and age structure. A simple bioeconomic model, negative binomial (NEGBIN), is proposed; this model relaxes the dynamic pool assumption without entering into the complexities of a geographically structured model. NEGBIN assumes a probability density function (the negative binomial), to describe heterogeneity in the density distribution over the population range. The model incorporates decision theory and different levels of risk aversion in resource management. The uncertainty associated with alternative fishing strategies, given imperfect knowledge about virgin stock biomass, is also included in the analysis. The model is applied to the Mesodesma donacium (surf clam) fishery in the central northern zone of Chile (South America). Alternative management strategies are evaluated with different levels of risk aversion. In the fisheries literature to date, this approach to evaluating the uncertainty associated with spatial allocation decisions has been rare. It is suggested that this kind of analysis, whether accompanied by quantitative probabilities of alternative states of nature or not, is an alternative way of dealing with risk and uncertainty in spatial allocation decisions.

A model to account for the consequences of host nutrition on the outcome of gastrointestinal parasitism in sheep: model evaluation

Parasitology ◽  
2007 ◽  
Vol 134 (9) ◽  
pp. 1279-1289 ◽  
Author(s):  
D. VAGENAS ◽  
S. C. BISHOP ◽  
I. KYRIAZAKIS
Keyword(s):  
Mathematical Model ◽  
Worm Burden ◽  
Management Strategies ◽  
Sensitivity Analyses ◽  
Sheep Model ◽  
Host Nutrition ◽  
Gastrointestinal Parasitism ◽  
Different Characteristics ◽  
Nutritional Strategies ◽  
Different Levels

SUMMARYThis paper describes sensitivity analyses and expectations obtained from a mathematical model developed to account for the effects of host nutrition on the consequences of gastrointestinal parasitism in sheep. The scenarios explored included different levels of parasitic challenge at different planes of nutrition, for hosts differing only in their characteristics for growth. The model was able to predict the consequences of host nutrition on the outcome of parasitism, in terms of worm burden, number of eggs excreted per gram faeces and animal performance. The model outputs predict that conclusions on the ability of hosts of different characteristics for growth to cope with parasitism (i.e. resistance) depend on the plane of nutrition. Furthermore, differences in the growth rate of sheep, on their own, are not sufficient to account for differences in the observed resistance of animals. The model forms the basis for evaluating the consequences of differing management strategies and environments, such as breeding for certain traits associated with resistance and nutritional strategies, on the consequences of gastrointestinal parasitism on sheep.

Zapatista and counter-Zapatista protests

2012 ◽  
Vol 49 (3) ◽  
pp. 459-472 ◽  
Author(s):  
María Inclán
Keyword(s):  
Negative Binomial ◽  
Empirical Test ◽  
Party Competition ◽  
Public Works ◽  
Social Programs ◽  
Reciprocal Effect ◽  
Systematic Analysis ◽  
Binomial Models ◽  
Different Levels ◽  
Protest Activity

This study represents the first systematic analysis of the interactions between pro-Zapatista and counter-Zapatista protestors in Chiapas, Mexico, and the first empirical test of movement–countermovement theories in a transitional democracy. Three claims are tested: (1) movement protests trigger countermovement protest activity; (2) different political parties at different levels of government trigger movement–countermovement protest activity; and (3) victories won by one side of a conflict, viewed as procedural concessions, trigger further pro- and countermovement protest activity. These hypotheses are tested using negative binomial models and data on Zapatista-related protest activity between 1994 and 2003. The results show that: (1) movement and countermovement protests have a positive, reciprocal effect on both groups' future protest activity; (2) movement and countermovement protesting groups use the dominant political party as a target of protest. The characteristics of the electoral cycle and rise of multi-party competition at all levels of government do not have a consistent effect on protest activity; (3) granting procedural concessions to pro-movement actors generates more protest activity among both groups. However, granting procedural concessions via social programs and public works to the population irrespective of its sympathy to either side of the movement–countermovement conflict decreases movement protests and increases countermovement protests.

scholarly journals FALSE CONSCIOUSNESS IN FINANCIAL MARKETS: OR IS IT IN IVORY TOWERS?

2013 ◽  
Vol 4 (1) ◽  
pp. 19-30
Author(s):  
Adi Schnytzer ◽  
Sara Westreich
Keyword(s):  
Risk Aversion ◽  
Financial Markets ◽  
Risk Index ◽  
Recent Model ◽  
Economic Index ◽  
Expected Returns ◽  
False Consciousness ◽  
Risk Averse ◽  
Different Levels ◽  
Negative Expectations

In general, models in finance assume that investors are risk averse. An example of such a recent model is the pioneering work of Aumann and Serrano, which presents an economic index of riskiness of gambles which is independent of wealth and holds (as might be understood from the adjective “economic”) for exclusively risk averse investors. In their paper, they discuss gambles with positive expected returns which will be accepted or rejected by agents which different levels of risk aversion. The question never asked by the authors (and in most of the finance literature) is: Who is offering these attractive gambles? To arrive at an answer, we extend the Aumann-Serrano risk index in such a way that it accommodates gambles with either positive or negative expectations and is thus suitable for both the risk averse and risk lovers.  Once we allow for the existence of risk lovers, it may be shown that in financial markets, many gambles with negative expectations are taken either knowingly or unknowingly so that there are always people that act as if they are risk lovers. The paper concludes with a brief discussion of the implications of our result, in particular that gambling is by no means restricted to the casino or the track.

scholarly journals Economic value of ecological information in ecosystem-based natural resource management depends on exploitation history

2018 ◽  
Vol 115 (7) ◽  
pp. 1658-1663 ◽  
Author(s):  
Timothy E. Essington ◽  
James N. Sanchirico ◽  
Marissa L. Baskett
Keyword(s):  
Resource Management ◽  
Natural Resource Management ◽  
Natural Resource ◽  
Net Present Value ◽  
Initial Conditions ◽  
Management Strategies ◽  
Ecosystem Approach ◽  
Economic Benefits ◽  
Ecological Knowledge ◽  
Imperfect Knowledge

Ecosystem approaches to natural resource management are seen as a way to provide better outcomes for ecosystems and for people, yet the nature and strength of interactions among ecosystem components is usually unknown. Here we characterize the economic benefits of ecological knowledge through a simple model of fisheries that target a predator (piscivore) and its prey. We solve for the management (harvest) trajectory that maximizes net present value (NPV) for different ecological interactions and initial conditions that represent different levels of exploitation history. Optimal management trajectories generally approached similar harvest levels, but the pathways toward those levels varied considerably by ecological scenario. Application of the wrong harvest trajectory, which would happen if one type of ecological interaction were assumed but in fact another were occurring, generally led to only modest reductions in NPV. However, the risks were not equal across fleets: risks of incurring large losses of NPV and missing management targets were much higher in the fishery targeting piscivores, especially when piscivores were heavily depleted. Our findings suggest that the ecosystem approach might provide the greatest benefits when used to identify system states where management performs poorly with imperfect knowledge of system linkages so that management strategies can be adopted to avoid those states.

Examining Safety on Two-Lane and Multilane Highways in Consideration of Access Spacing

2019 ◽  
Vol 2673 (11) ◽  
pp. 388-397
Author(s):  
Raha Hamzeie ◽  
Megat-Usamah Megat-Johari ◽  
Iftin Thompson ◽  
Timothy P. Barrette ◽  
Trevor Kirsch ◽  
...  
Keyword(s):  
Negative Binomial ◽  
Random Effect ◽  
Management Strategies ◽  
Negative Binomial Regression ◽  
Access Point ◽  
Management Policy ◽  
Crash Risk ◽  
Access Management ◽  
Crash Data ◽  
Crash Rates

Access management strategies, such as the introduction of minimum access point spacing criteria and turning movement restrictions, have been shown to be important elements in optimizing the operational and safety performance of roadway segments. The relationship between safety and these types of access policies is a complex issue, and the impacts of such features on traffic crashes is critical to the development of appropriate access management strategies. The purpose of this study was to provide a quantitative evaluation of how crash risk on multilane and two-lane highways varies with respect to access spacing in support of the development of a revised access management policy. Data were obtained for approximately 1,247 and 5,795 mi of segments across multilane and two-lane highways, respectively. Crash data were obtained for a five-year period from 2012 to 2016 and a series of random effect negative binomial regression models were estimated for each facility to examine the association between crash frequency, access point spacing, and traffic volume. For both facility types, crashes were found to increase consistently as the average spacing of access points along road segments decreased. Crash rates were highest when consecutive accesses were within 150 ft of one another and the frequency of crashes decreased substantively as spacing was increased to 300 ft and, particularly, 600 ft. With spacing beyond 600 ft, crash rates continued to decrease, although these improvements were less pronounced than at the lower range of values. These findings were generally consistent on multilane and two-lane highways.

Perception of climate change and adaptation strategies in Vietnam

2017 ◽  
Vol 9 (4) ◽  
pp. 501-516 ◽  
Author(s):  
Ashok K. Mishra ◽  
Valerian O. Pede
Keyword(s):  
Climate Change ◽  
Negative Binomial ◽  
Management Strategies ◽  
Mekong Delta ◽  
Climatic Changes ◽  
Adaptation Strategies ◽  
Content Type ◽  
Climatic Stress ◽  
Financial Strategies ◽  
The Impact

Purpose The purpose of this study is to first examine the factors affecting the intra-household perception of climate change. Second, the study investigates the impact of the perception of climatic stress on the operators’ and spouses’ intra-household adaptation strategies (farm and household financial strategies). Design/methodology/approach The study uses household survey data from Vietnam’s Mekong Delta. The study uses probit and negative binomial count data approaches to evaluate the empirical model. Findings Results confirm the existence of intra-household gender differences in the adaptation strategies. The authors found that although spouses perceive climatic stress, they are less likely to adapt to such stresses when it comes farming enterprise, but more likely to adapt to household financial strategies. In contrast, farm operators, in the presence of climatic stresses, undertake both farm and household finance adaptation strategies. Practical implications Investment in climate smart agriculture can help households in managing climatic stresses. Originality/value A farmer in Asia, and Vietnam in particular, faces significant risks from climatic changes. In Vietnam, agriculture is easily affected by natural disasters and climatic changes. This study provides insights into the perception of climatic changes by operators and spouses in Vietnam’s Mekong Delta. Perceived changes in the climate have a greater impact on women because they typically lack the necessary tools to adapt to climate change. The current findings could be useful in managing climatic risk in Vietnam’s Mekong Delta and be helpful to policymakers in designing risk management strategies in response to climatic changes.

Leaching losses of N under grazed irrigated and non-irrigated pastures

2004 ◽  
Vol 142 (5) ◽  
pp. 503-516 ◽  
Author(s):  
N. PAKROU ◽  
P. J. DILLON
Keyword(s):  
Negative Binomial ◽  
Root Zone ◽  
Management Strategies ◽  
South Australia ◽  
Dairy Farm ◽  
Spatial And Temporal Variability ◽  
Pasture Management ◽  
Grazed Pasture ◽  
Nitrate Concentrations ◽  
Current Transition

High spatial and temporal variability of nitrogen application via livestock urine on grazed pasture make meaningful measurement of leaching of nitrate very difficult. The present study was aimed at estimating the mean annual nitrogen loadings and concentrations leached to an underlying aquifer beneath unfertilized irrigated and non-irrigated paddocks of a dairy farm at OB Flat 10 km south of the city of Mount Gambier (37°50′S, 140°40′E), South Australia. Urine was collected in the milking shed and applied to 1 m deep monolith lysimeters in three separate seasons in 1992. Some lysimeters received two applications. Drainage and N fluxes and concentrations were recorded 1 year before urine application and for 3 years following urine applications. A negative binomial function was used to specify the appropriate proportions of pasture subject to 0, 1 or 2 loadings in a year, and the lysimeter drainage measurements were then scaled across seasons and paddock area to estimate mean annual leaching under the whole of each paddock. It was found that the timing of urine application had a profound effect on the leaching of nitrogen. Results indicated that the nitrate flux leaching from the root zone in the irrigated paddock was 26–33 kg N/ha/year at 13–17 mg N/litre and in the non-irrigated paddock, 10–13 kg N/ha/year at 9–11 mg N/litre. These estimates are not inconsistent with nitrate concentrations measured in groundwater but cannot be independently verified. The current transition from non-irrigated to irrigated pastures is likely to double nitrogen loads to the aquifer and cause nitrate concentrations in groundwater to exceed drinking water guidelines, unless alternative pasture management strategies are developed.

scholarly journals Managing the Cloud Continuum: Lessons Learnt from a Real Fog-to-Cloud Deployment

2021 ◽  
Author(s):  
Xavi Masip-Bruin ◽  
Eva Marín-Tordera ◽  
Sergi Sánchez-López ◽  
Jordi Garcia ◽  
Admela Jukan ◽  
...  
Keyword(s):  
Cloud Computing ◽  
Management Strategies ◽  
Edge Computing ◽  
Design And Development ◽  
Management Framework ◽  
Efficient Management ◽  
Research Challenges ◽  
Lessons Learnt ◽  
Development Processes ◽  
Different Levels

The wide adoption of the recently coined fog and edge computing paradigms alongside conventional cloud computing creates a novel scenario, known as the cloud continuum, where services may benefit from the overall set of resources to optimize their execution. To operate successfully, such a cloud continuum scenario demands for novel management strategies, enabling a coordinated and efficient management of the entire set of resources, from the edge up to the cloud, designed in particular to address key edge characteristics, such as mobility, heterogeneity and volatility. The design of such a management framework poses many research challenges and has already promoted many initiatives worldwide at different levels. In this paper we present the results of one of these experiences driven by an EU H2020 project, focusing on the lessons learnt from a real deployment of the proposed management solution in three different industrial scenarios. We think that such a description may help understand the benefits brought in by a holistic cloud continuum management and also may help other initiatives in their design and development processes.

scholarly journals Community Mobility and COVID-19 Dynamics in Jakarta, Indonesia

2021 ◽  
Author(s):  
Ratih Oktri Nanda ◽  
Aldilas Achmad Nursetyo ◽  
Aditya Lia Ramadona ◽  
Muhammad Ali Imron ◽  
Anis Fuad ◽  
...  
Keyword(s):  
Linear Regression ◽  
Multiple Linear Regression ◽  
Linear Model ◽  
Generalized Linear Model ◽  
Negative Binomial ◽  
Human Mobility ◽  
Management Strategies ◽  
Principal Component ◽  
Outbreak Management ◽  
Community Mobility

Background Human mobility could act as a vector to facilitate the spread of infectious diseases. In response to the COVID-19 pandemic, Google Community Mobility Reports (CMR) provide the necessary data to explore community mobility further. Therefore, we aimed to examine the relationship between community mobility on COVID-19 dynamics in Jakarta, Indonesia. Methods We utilized the mobility data from Google from February 15 to December 31, 2020. We explored several statistical models to estimate the COVID-19 dynamics in Jakarta. Model 1 was a Poisson Regression Generalized Linear Model (GLM), Model 2 was a Negative Binomial Regression Generalized Linear Model (GLM), and Model 3 was a Multiple Linear Regression (MLR). Results We found that Multiple Linear Regression (MLR) with some adjustments using Principal Component Analysis (PCA) was the best fit model. It explained 52% of COVID-19 cases in Jakarta (R-Square: 0.52, p<0.05). All mobility variables were significant predictors of COVID-19 cases (p<0.05). More precisely, about 1% change in grocery and pharmacy would contribute to a 4.12% increase of the COVID-19 cases in Jakarta. Retails and recreations, workplaces, transit stations, and parks would result in 3.11%, 2.56%, 2.26%, and 1.93% of more COVID-19 cases, respectively. Conclusion Our study indicates that increased mobility contributes to increased COVID-19 cases. This finding will be beneficial to assist policymakers to have better outbreak management strategies, to anticipate increased COVID-19 cases in the future at certain public places and during seasonal events such as annual religious holidays or other long holidays in particular.

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