Integrating habitat concerns into Gordon-Schaefer model

In the Gordon-Schaefer model (G-S model), widely used to design fisheries management policy, only resource stock dynamic is considered and carrying capacity is constant. We propose an extension to the G-S model that incorporates the dynamics of carrying capacity as an indicator of dynamics of the marine habitats. The study yields two main findings. First, we demonstrate that habitats matter, by showing that the main outcomes of the G-S model are dramatically modified if habitats are included in the analysis. Second, through a heuristic model and simulations, we show, for the first time, that our extended model provides an appropriate framework to analyse the putative contribution of MPAs and ARs. The model presented in this article opens the way to a better understanding of the benefits of MPAs and ARs, as well as other habitat protection policies.Bioeconomics, Gordon-Schaefer model, Marine habitats, Artificial reefs

A TEST OF CHEAP TALK IN DIFFERENT HYPOTHETICAL CONTEXTS: THE CASE OF AIR POLLUTION

We explore the influence of a neutral cheap talk script in three typical scenarios used in the CV literature devoted to the valuation of air pollution effects. We show that cheap talk has a differentiated effect depending on the scenario implemented. It decreases protest responses with no effect on WTP values in the scenario based on a new drug. When a move to a less polluted city is involved, it has no effect on protest responses but decreases WTP values. Surprisingly, cheap talk increases protest responses but decreases WTP values when new regional air pollution regulations are at stake.Willingness to pay ; contingent valuation ; cheap talk ; context ; field experiment ; air pollution

ET SI CE QUE J'AI FAIT HIER INFLUAIT SUR MON PROFIT AUJOURD'HUI? Un modèle bio-économique de libre accès où les agents apprennent seuls.

Dans cette étude, nous soulignons l'importance d'un facteur s'avérant significatif dans les problèmes des dilemmes sociaux. Il s'agit de la perception par les usagers d'une ressource renouvelable commune de leurs actions passées et de leur rôle dans la formation du profit. La dynamique d'apprentissage a alors un impact sur les profits actuels. Pour ce faire, nous travaillons dans un cadre dynamique qui permet de modéliser l'impact des actions passée des usagers sur l'état de la ressource et, donc, sur leurs profits. Nous analysons les équilibres de la ressource renouvelable commune en fonction des trois modèles d'apprentissage adaptés du modèle de Roth-Erev qui décrit les différentes perceptions de ce problème. Certaines recommandations sont fournies en rapport avec les résultats des simulations. Les paramètres du modèle dynamique utilisé sont calibrés pour le cas de la pêche à Marseill

Willingness to Pay of Committed Citizens: A Field Experiment

In this paper, we propose a behavioural approach to determine the extent to which the consumer/citizen distinction affects interpretations of monetary values. We perform a field experiment dealing with air pollution, where some (randomly selected) subjects are given the opportunity to behave politically by signing a petition for environmental protection prior to stating their private preferences in a standard contingent valuation exercise. We show that the petition has the potential to influence respondents' willingness to pay and that whether the effect is negative or positive depends on the degree of (dis)similarity between the petition and the scenario in which willingness to pay are elicited. We interpret the results using the theory of commitment borrowed from social psychology.Field Experiment, Citizen, Consumer, Contingent Valuation, Willingness to pay, Commitment, Air Pollution

ET SI CE QUE J'AI FAIT HIER INFLUAIT SUR MON PROFIT AUJOURD'HUI? Un modèle bio-économique de libre accès où les agents apprennent seuls.

Dans cette étude, nous soulignons l'importance d'un facteur s'avérant significatif dans les problèmes des dilemmes sociaux. Il s'agit de la perception par les usagers d'une ressource renouvelable commune de leurs actions passées et de leur rôle dans la formation du profit. La dynamique d'apprentissage a alors un impact sur les profits actuels. Pour ce faire, nous travaillons dans un cadre dynamique qui permet de modéliser l'impact des actions passée des usagers sur l'état de la ressource et, donc, sur leurs profits. Nous analysons les équilibres de la ressource renouvelable commune en fonction des trois modèles d'apprentissage adaptés du modèle de Roth-Erev qui décrit les différentes perceptions de ce problème. Certaines recommandations sont fournies en rapport avec les résultats des simulations. Les paramètres du modèle dynamique utilisé sont calibrés pour le cas de la pêche à MarseilleModèle bioéconomique de pêcherie ; simulation agents ; ressource renouvelables ; libre accès ; tragédie des communs

A TEST OF CHEAP TALK IN DIFFERENT HYPOTHETICAL CONTEXTS: THE CASE OF AIR POLLUTION

We explore the influence of a neutral cheap talk script in three typical scenarios used in the CV literature devoted to the valuation of air pollution effects. We show that cheap talk has a differentiated effect depending on the scenario implemented. It decreases protest responses with no effect on WTP values in the scenario based on a new drug. When a move to a less polluted city is involved, it has no effect on protest responses but decreases WTP values. Surprisingly, cheap talk increases protest responses but decreases WTP values when new regional air pollution regulations are at stake

Willingness to Pay of Committed Citizens: A Field Experiment

In this paper, we propose a behavioural approach to determine the extent to which the consumer/citizen distinction affects interpretations of monetary values. We perform a field experiment dealing with air pollution, where some (randomly selected) subjects are given the opportunity to behave politically by signing a petition for environmental protection prior to stating their private preferences in a standard contingent valuation exercise. We show that the petition has the potential to influence respondents' willingness to pay and that whether the effect is negative or positive depends on the degree of (dis)similarity between the petition and the scenario in which willingness to pay are elicited. We interpret the results using the theory of commitment borrowed from social psychology

Incorporating Habitat Dynamics into Bioeconomic Model of Fishery. Application to Artificial Reefs

In this paper the emphasis is put on an important aspect of renewable resource use that was disregarded until now. It is the evolution of environmental carrying capacity which is traditionally interpreted as a maximal population level that can be supported by the environment (or by habitats of which it consists). Hence we adapt the Gordon-Schaefer model with constant carrying capacity by incorporating time-dependent carrying capacity that determines the state of habitats. They are subject to some biological processes (habitat rehabilitation) as well as to human aggressions (in particular habitat degradation due to fishing). Based on the developed model, we reassess the recommendations considered as a benchmark for resource managers until recently. Under simple hypotheses on the form of habitat (carrying capacity) dynamics, the current study has shown the importance of the latter for the design of management tools. When dynamic patterns of habitats are not taken into account, fishery recommendations based on Gordon-Schaefer model can be aberrant and lead to the collapse of the fishery. The presented model allows not only to enrich the design of management tools but also to assess the performance of artificial reefs, a promising ecosystem-based tool widely used in some coastal areas. The economic benefits of artificial reefs are still not well studied and represent a challenge to take up. Since artificial reefs are conceived as replacement for natural habitats, they assume the same role as these latter. Therefore the structure of our model seems appropriate to evaluate this particular management tool.Keywords: Modeling and Economic Theory, Fisheries Modeling, Fisheries Economic

Is Fishing Compatible with Environmental Conservation: A Stochastic Model with an Element of Self-Protection

The optimal economic exploitation of renewable resources has been a subject of great interest in the last few decades. Nevertheless many fish stocks have been damaged in such a way that economical exploitation is jeopardized or even interrupted. Consequently, an increasing number of fisheries are collapsing. Causes that are frequently put forward include fishery overcapitalization, habitat destruction and excessive harvest. In the present work, we study the impact of fishing activity on the marine ecosystem and on stock variability. We define fishing not only through annual harvest, but also through a second component, called the degree of protection of the fishery environment. This characterizes the environmental impact of fishing. A stochastic dynamic programming problem is presented in infinite horizon, where a sole owner seeks to maximize a discounted expected profit. We assume a stochastic stock-recruitment relationship where both components of the fishing activity have an impact on the probability law of the state of the fishery environment. We characterize the optimal fishing policy and we compare it with standard models. We find that the optimal policy is not a constant escapement policy and indicates an element of self-protection by the fishery manager. Finally, we are able to analyse the influence of the degree of protection of the fishery environment on environmental conservation (in terms of resource sustainability) and on economic activity

Rectal Carriage of Extended-Spectrum Beta-Lactamase-Producing Gram-Negative Bacilli in Community Settings in Madagascar

BACKGROUND: Extended-spectrum ß-lactamase-producing Enterobacteria (ESBL-PE) emerged at the end of the 1980s, causing nosocomial outbreaks and/or hyperendemic situations in hospitals and long-term care facilities. In recent years, community-acquired infections due to ESBL-PE have spread worldwide, especially across developing countries including Madagascar. OBJECTIVES: This study aimed to determine the prevalence and risk factors of intestinal carriage of ESBL-PE in the community of Antananarivo. METHODS: Non-hospitalized patients were recruited in three health centers in different socio economic settings. Fresh stool collected were immediately plated on Drigalski agar containing 3 mg/liter of ceftriaxone. Gram-negative bacilli species were identified and ESBL production was tested by a double disk diffusion (cefotaxime and ceftazidime +/- clavulanate) assay. Characterization of ESBLs were perfomed by PCR and direct sequencing . Molecular epidemiology was analysed by Rep-PCR and ERIC-PCR. RESULTS: 484 patients were screened (sex ratio  = 1.03, median age 28 years). 53 ESBL-PE were isolated from 49 patients (carrier rate 10.1%). The isolates included Escherichia coli (31), Klebsiella pneumoniae (14), Enterobacter cloacae (3), Citrobacter freundii (3), Kluyvera spp. (1) and Pantoae sp.(1). In multivariate analysis, only the socioeconomic status of the head of household was independently associated with ESBL-PE carriage, poverty being the predominant risk factor. CONCLUSIONS: The prevalence of carriage of ESBL in the community of Antananarivo is one of the highest reported worldwide. This alarming spread of resistance genes should be stopped urgently by improving hygiene and streamlining the distribution and consumption of antibiotics