Use and limits of three assessment methods of fish size spectra and abundance in two tropical man-made lakes
2007
Coll, Céline | Tito de Morais, Luis | Laë, Raymond | Lebourges-Dhaussy, Anne | Simier, Monique | Guillard, Jean | Josse, Erwan | Ecoutin, Jean-Marc | Albaret, Jean-Jacques | Raffray, Jean | Kantoussan, Justin | Réponses adaptatives des populations et des peuplements de poissons aux pressions de l'environnement (RAP) | Institut de Recherche pour le Développement (IRD) | Hydro-acoustique appliquée à l'halieutique, à l'écologie et à l'éthologie aquatiques (US Acoustique Halieutique) ; Institut de Recherche pour le Développement (IRD [France-Ouest])-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER) | Ecosystèmes Marins Exploités (UMR EME) ; Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Montpellier (UM) | Centre Alpin de Recherche sur les Réseaux Trophiques et Ecosystèmes Limniques (CARRTEL) ; Institut National de la Recherche Agronomique (INRA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])
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Показать больше [+] Меньше [-]Английский. A comparative study, combining three different assessment methods (fish gillnet sampling, artisanal fisheries surveys and hydroacoustics) was conducted in Mali where two man-made reservoirs (Sélingué and Manantali) are particularly suited for investigating the impact of fishing effort on the fish assemblage. These two ecosystems have relatively similar areas, edaphic and environmental properties but are subjected to different levels of fishing exploitation (low at Manantali, high at Sélingué). The comparison is based on two indicator parameters: the abundance indices and the size spectra distributions, obtained by the three methods at two contrasting hydrological seasons (April and October). The results were compared first between the two seasons, and then between the two lakes. The present work is based on two main hypotheses: (1) that there is a higher fish abundance in October associated with smaller overall sizes, after spawning; (2) a lower abundance and smaller sizes in the Sélingué reservoir than in Manantali, because of the much higher fishing pressure in Sélingué. The relevance of each method to the selected indicators is discussed. On the one hand, the three methodologies on the whole gave similar conclusions and they also complement each other. On the other hand, some results do not match the hypotheses because of biases due to difficulties and technical limitations of each method in such ecosystems (shallow water with vegetation and stumps of former forests)
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