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Chary, K., Fiandrino, A., Covès, D., Aubin, J., Falguière, J. - C., & Callier, M. D. (2019). Modeling sea cage outputs for data-scarce areas: application to red drum (Sciaenops ocellatus) aquaculture in Mayotte, Indian Ocean. Aquacult Int, .
Résumé: Robust and accurate prediction of fish farm waste is a first and crucial step in managing the cause–effect chain that leads to local environmental impacts of aquaculture. Since aquatic production is diversifying with new fish species and extending to new areas for which data can be scarce, it is important to develop parsimonious approaches with fewer data requirements and less scientific complexity. We developed the Farm productIon and Nutrient emiSsions (FINS) model, which simulates fish farm operation and estimates fish biomass, feed inputs, and waste emissions from sea cages using simple modeling approaches and a variety of data sources. We applied FINS to red drum (Sciaenops ocellatus) culture in Mayotte by collecting relevant input data (growth, digestibility) from experimental trials. Three explorative farming scenarios—small, medium, and large—were defined from field survey data to examine and compare emissions of a range of potential commercial culture conditions and production scales (23, 299, and 2079 t year−1, respectively). Comparison of the three scenarios showed that waste emissions per ton of fish harvested during routine operations, and thus environmental impacts, were higher for longer culture cycles (medium farm) because of lower feed conversion efficiency. The FINS model is a simple alternative tool to assess and compare environmental impacts of different farming systems and practices for new aquaculture species and regions. It provides important drivers to assess local environmental impacts of fish farms and can therefore facilitate the process of licensing new farming systems for decision-makers.
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Dalleau, M., Kramer-Schadt, S., Gangat, Y., Bourjea, J., Lajoie, G., & Grimm, V. (2019). Modeling the emergence of migratory corridors and foraging hot spots of the green sea turtle. Ecol. Evol., .
Résumé: Environmental factors shape the spatial distribution and dynamics of populations. Understanding how these factors interact with movement behavior is critical for efficient conservation, in particular for migratory species. Adult female green sea turtles, Chelonia mydas, migrate between foraging and nesting sites that are generally separated by thousands of kilometers. As an emblematic endangered species, green turtles have been intensively studied, with a focus on nesting, migration, and foraging. Nevertheless, few attempts integrated these behaviors and their trade-offs by considering the spatial configurations of foraging and nesting grounds as well as environmental heterogeneity like oceanic currents and food distribution. We developed an individual-based model to investigate the impact of local environmental conditions on emerging migratory corridors and reproductive output and to thereby identify conservation priority sites. The model integrates movement, nesting, and foraging behavior. Despite being largely conceptual, the model captured realistic movement patterns which confirm field studies. The spatial distribution of migratory corridors and foraging hot spots was mostly constrained by features of the regional landscape, such as nesting site locations, distribution of feeding patches, and oceanic currents. These constraints also explained the mixing patterns in regional forager communities. By implementing alternative decision strategies of the turtles, we found that foraging site fidelity and nesting investment, two characteristics of green turtles' biology, are favorable strategies under unpredictable environmental conditions affecting their habitats. Based on our results, we propose specific guidelines for the regional conservation of green turtles as well as future research suggestions advancing spatial ecology of sea turtles. Being implemented in an easy to learn open-source software, our model can coevolve with the collection and analysis of new data on energy budget and movement into a generic tool for sea turtle research and conservation. Our modeling approach could also be useful for supporting the conservation of other migratory marine animals.
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Drouineau, H., Lobry, J., Bez, N., Travers-Trolet, M., Vermard, Y., & Gascuel, D. (2016). The need for a protean fisheries science to address the degradation of exploited aquatic ecosystems. Aquat. Living Resour., 29(2), Unsp-E201.
Résumé: In this introductory paper we highlight key questions that were discussed during the symposium on “Status, functioning and shifts in marine ecosystems” organized by the Association Francaise d'Halieutique (French Association for Fisheries Sciences, Montpellier, France, July 2015). This symposium illustrated that fisheries science is now working at multiple scales and on all dimensions of socio-ecosystems (ecological, political, sociological, and economic), with a great diversity of approaches and taking into account different levels of complexity while acknowledging diverse sources of uncertainty. We argue that we should go one step further and call for a protean fisheries science to address the deteriorated states of aquatic ecosystems caused by anthropogenic pressures. Protean science is constantly evolving to meet emerging issues, while improving its coherence and integration capacity in its complexity. This science must be nourished by multiple approaches and be capable of addressing all organizational scales, from individual fish or fishermen up to the entire ecosystem, include society, its economy and the services it derives from aquatic systems. Such a protean science is required to address the complexity of ecosystem functioning and of the impacts of anthropogenic pressures.
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Duboz, R., Versmisse, D., Travers, M., Ramat, E., & Shin, Y. - J. (2010). Application of an evolutionary algorithm to the inverse parameter estimation of an individual-based model. Ecological Modelling, 221, 840–849.
Résumé: Inverse parameter estimation of individual-based models (IBMs) is a research area which is still in its infancy, in a context where conventional statistical methods are not well suited to confront this type of models with data. In this paper, we propose an original evolutionary algorithm which is designed for the calibration of complex IBMs, i.e. characterized by high stochasticity, parameter uncertainty and numerous non-linear interactions between parameters and model output. Our algorithm corresponds to a variant of the population-based incremental learning (PBIL) genetic algorithm, with a specific “optimal individual” operator. The method is presented in detail and applied to the individual-based model OSMOSE. The performance of the algorithm is evaluated and estimated parameters are compared with an independent manual calibration. The results show that automated and convergent methods for inverse parameter estimation are a significant improvement to existing ad hoc methods for the calibration of IBMs.
Mots-Clés: algorithms; and; calibration; ecosystem; estimation; Evolutionary; genetic; Individual-based; marine; model; Parameter
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Yemane, D., Shin, Y. - J., & Field, J. G. (2009). Exploring the effect of Marine Protected Areas on the dynamics of fish communities in the southern Benguela : an individual-based modelling approach. Ices Journal of Marine Science, 66(2), 378–387.
Résumé: Marine Protected Areas (MPAs) have been suggested as a tool that can achieve some of the goals of an Ecosystem Approach to Fisheries (EAF), e.g. prevention of overexploitation, biodiversity conservation, recovery of overexploited population, but the consequences of their establishment on the dynamics of protected components are often unclear. Spatial and multispecies models can be used to investigate the effects of their introduction. An individual-based, spatially explicit, size-structured, multispecies model (known as OSMOSE) is used to investigate the likely consequences of the introduction of three MPAs off the coast of South Africa, individually or in combination. The simultaneous introduction of the MPAs affected varying proportions of the distribution of the modelled species (5-17%) and 12% of the distribution of the whole community. In general, the introduction of the MPAs in the different scenarios resulted in a relative increase in the biomass of large predatory fish and a decrease in the biomass of small pelagic fish. The simulation demonstrates that consideration of trophic interactions is necessary when introducing MPAs, with indirect effects that may be detrimental to some (mainly smaller prey) species.
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