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Master Thesis

Effet du changement climatique sur la condition corporelle et le sex-ratio des populations de poissons méditerranéennes

Abstract : Within the Mediterranean sea, the Gulf of Lion (GOL) is one of the most affected areas by global warming. This environmental upheaval can have effects on body condition and sex ratio of Mediterranean fish populations. To test this hypothesis, time series of body condition, sex ratio, abundance, and environmental variables (SST, WeMOI) are extracted from the MEDITS database and analyzed one by one. Then, a Dynamic Factor Analysis (DFA) was applied to these time series in order to look for common trends between species. Afterwards, the behavior of some series was modeled,to test whether or not the sex ratio of body condition could impact the stock dynamics. To this end, we fitted a Multivariate Autoregressive Model of first order to the time series of abundance, body condition and sex ratio of European hake Merluccius merluccius, together with environmental covariates. This is to describe how the different variables influence the population dynamics of hake (GOL, GSA7), and to understand the links between these dynamics and environmental covariates in a context of global changes. The DFA sex-ratio series reveals a lack of trend over time. The results of the model show that the sex ratio is not affected by temperature variations, and has no influence on the population dynamics of hake. Regarding body condition, the DFA highlights two main trends: A group of fish whose body condition decreases over time, and another one with an increasing body condition over time. The proposed MAR(1) indicates that the body condition of hake has no impact on the population dynamics and is not influenced by environmental conditions. However, the internal dynamics of the hake population remain strongly related to environmental conditions (SST, WeMOI). This study should now be extended to several species, to provide further insights on the stocks dynamics in the context of the ecosystem approach to fisheries management.
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Master Thesis
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Submitted on : Wednesday, November 13, 2019 - 3:06:22 PM
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Meriem Cyria Bensebaini. Effet du changement climatique sur la condition corporelle et le sex-ratio des populations de poissons méditerranéennes. Sciences du Vivant [q-bio]. 2019. ⟨dumas-02361713⟩

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