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This paper develops a theoretical framework to assess resources management procedures from a sustainability perspective, when re-source dynamics is marked by uncertainty. Using stochastic viability, management procedures are ranked according to their probability to achieve economic and ecological constraints over time. This frame-work is applied to...
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... first application consists in computing the viability probability of two specific management procedures: a CES λ = 0 . 2 and a CQS at level Y = 1 . 2 millions of tons, just about the current quota level in this fishery. Following the framework of Sect. 3.1, these probabilities are computed for each couple ( p, y min ) ∈ [0 , 0 . 4] × [1 , 1 . 5] of biological and economic thresholds. We thus obtain 3D graphics in Figure 3 (left: CQS; right:CES). Let us illustrate how these graphics make different types of comparisons possible. A preliminary visual comparison shows that, for moderate economic thresholds between 1 . 1 and 1 . 2 millions of tons and low biological thresholds, the CQS provides a higher viability probability than the CES. Our second application consists of identifying the best strategy within each family of policy types, namely, either CES or CQS. We will define the best strategy as the one which gives the higher viability probability within its policy family. For each couple ( p, y min ) ∈ [0 , 0 . 4] × [1 , 1 . 5] of biological and economic thresholds, we compute the highest viability probability for ...
Context 2
... kind of policy. Then, we obtain two 3D graphics (one for each type of strategies) as can be seen in Figure 4. By introducing flexibility within each policy family, that is that we can change the level of the constant policy, we observe that a larger range of combinations of biological and economic thresholds become “viable”, with a strictly positive probability (compare Figure 3 and Figure 4) Our third application consists of, after identifying the best strategy within each CES or CQS family, comparing these optima between families. The results produced in the preceding sections are useful to identify cir- cumstances under which each strategy is likely to be preferable. Indeed, this comparison can be obtained from Figure 4: the 2D graphic of Figure 5 exhibits, for each couple ( p, y min ) ∈ [0 , 0 . 4] × [1 , 1 . 5] of biological and economic thresholds, for which family is the maximum of the two surfaces is achieved. However, due to confidence interval, we in fact represent the domain where one strategy strictly dominates the other, that is one for which the resulting probability interval lies strictly above the other one. The best policy type is identified by a specific given color: the dark (blue) area identifies the biological and economic thresholds ( p, y min ) where the best constant quota strategy has higher probability than the best constant effort strategy, the light (yellow) area has exactly the opposite meaning, and the intermediary area identifies the thresholds for which both policy types have equal probability (that is, the confidence intervals ...
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This paper develops a theoretical framework to assess resources management procedures from a sustainability perspective, when resource dynamics is marked by uncertainty. Using stochastic viability, management procedures are ranked according to their probability to achieve economic and ecological constraints over time. This framework is applied to a...
Citations
... The use of constant yield harvesting method can be risky as it does not consider stock fluctuations and can cause population decline (Roughgarden & Smith 1996) especially in small populations (Stephens et al. 2002). Second, the method of constant-effort harvesting could be more appropriate because of its natural adaptation to the state of the resource (Roughgarden & Smith 1996;Martinet et al. 2010). It is thus less dependent on yearly scientific assessments used to track stock fluctuations and reduces the risks of uncertainty (e.g., bearded pig Sus barbutus, Lee et al. 2011;Martinet et al. 2010). ...
... Second, the method of constant-effort harvesting could be more appropriate because of its natural adaptation to the state of the resource (Roughgarden & Smith 1996;Martinet et al. 2010). It is thus less dependent on yearly scientific assessments used to track stock fluctuations and reduces the risks of uncertainty (e.g., bearded pig Sus barbutus, Lee et al. 2011;Martinet et al. 2010). For fisheries, Shepherd (2003) proposes the number of days spent in the sea per boat as the most practicable measure of fishing effort and a comprehensive satellite surveillance system as the control method. ...
Trophy hunting, which is a form of recreational hunting with the main objective of collecting a trophy of interest, is a controversial subject. This activity could potentially generate an anthropogenic Allee effect (AAE). This demographic process states that the valuation of rarity could drive rare species exploitation and even lead to their extinction. Our project aims at testing the potential for an AEE in trophy hunting. We demonstrate that rare species have a high financial value, regardless of the trophy size, indicating that there is a high demand for those species. We also show that the number of trophies traded internationally and the number of recorded trophies by the Safari Club International (one of the largest clubs for international trophy hunters in the USA) rises as the degree of rarity (as measured by a rarity index) increases. Trophy hunting of rare species has been proposed as a tool to fund their conservation. However, our results indicate that there is a risk of an AAE for rare species. Furthermore, the combined effects of trophy hunting, illegal hunting, corruption as well as the lack of population knowledge and of management controls have potential to result in the unsustainable exploitation of rare species of high financial value. Nonetheless, trophy hunting has potential to generate strong financial incentives that are necessary for wildlife preservation. Such incentives are only likely to be effective if strict measures are required and enforced to prevent overexploitation of rare trophy species
