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Distribution spatiale de poissons grégaires dans un réseau de structures artificielles : le cas de la baie de Saint-Paul à l’Île de la Réunion

Abstract : The main objective of this work is to improve our understanding of the eco-ethological processes that govern marine resources associated with coastal artificial habitats. To understand this system, we have first presented a synthesis of the aggregation processes of fish found in association with artificial habitats.We described the reasoning approach shared by the two main types of fishery tools that are the Artificial Reefs and Fish Aggregation Device (FAD). Our Work was then focused on the analysis of fish distribution in a network of coastal FADs, moored in St. Paul's bay. This analysis, based on acoustic surveys, has shown that the intensity of association varied depending on the fish community (benthic or pelagic), the diel period and the development stage of the fish (adult or juvenile). In particular, it has been pointed out that whatever the fish community the aggregations of juveniles were more extensive than the adults.We then described the tagging experiments performed on two representative species: the Selar crumenophthalmus (pelagic) and Lutjanus kasmira (benthic). The results of these experiments have allowed specifying the fish dependence on FAD.Concerning the associative behaviour of adult pelagic fish, the analyses have confirmed the meeting point hypothesis, suggesting that fish used the FADs to form larger schools. This reinforces the idea that these fish optimize their survival by focusing on social interaction with conspecific.The study of the benthic species has shown a strong association of the fish to the structures and has validated the hypothesis of an increasing trophic activity by night out of the FAD.From these observations, an estimate of the entire FAD network influence has been performed and then input, firstly into the geostatistical analysis of the biomass distribution in the bay, and secondly into the distribution analysis of the biomass as influenced or not by the FAD. This work showed a significant linear relationship between FAD associated and free biomass.We then explored the contribution of the association behaviour and the environmental factors (turbidity and bottom slope), integrating both into a generalized additive model. This study showed that the FAD effect is not always a prior factor influencing the biomass in the bay. We, therefore, hypothesized that the FAD is a habitat that would enrich the bay by providing new conditions for fish in search of optimal living conditions for their survival or comfort. In general, it will be important to deepen the impact of the two major factors influencing the ecological dynamics of aggregation around FADs namely trophic conditions and predation. In prospect, we could apply our methodology on drifting FADs and also use our results for improvement and restoration of natural habitats.
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  • HAL Id : tel-01176171, version 1


Gaël Potin. Distribution spatiale de poissons grégaires dans un réseau de structures artificielles : le cas de la baie de Saint-Paul à l’Île de la Réunion. Biodiversité et Ecologie. Université de la Réunion, 2009. Français. ⟨NNT : ⟩. ⟨tel-01176171⟩



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