Use and limits of three methods for assessing fish size spectra and fish abundance in two tropical man-made lakes

Use and limits of three methods for assessing fish size spectra and fish abundance in two tropical man-made lakes Coll Céline auteur aut IRD Tito de Morais Luis auteur aut IRD Laë Raymond auteur aut IRD Lebourges-Dhaussy Anne auteur aut IRD Simier Monique auteur aut IRD Guillard J. auteur aut IRD Josse Erwan auteur aut IRD Ecoutin Jean-Marc auteur aut IRD Albaret Jean-Jacques auteur aut IRD Raffray Jean auteur aut IRD Kantoussan Justin auteur aut IRD text journalArticle eng text/pdf born digital access 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 (Selingue 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 Selingue). 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 Selingue reservoir than in Manantali, because of the much higher fishing pressure in Selingue. 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). specialized fish sampling artisanal fisheries hydroacoustic abundance estimate size distribution shallow waters West Africa 040 Fisheries Research 83 2-3 306-318 2007 0165-7836 https://www.documentation.ird.fr/hor/fdi:010037817 10.1016/j.fishres.2006.10.005 0165-7836 [F A010037817] https://www.documentation.ird.fr/hor/fdi:010037817 https://www.documentation.ird.fr/intranet/publi/2007/03/010037817.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2007-03-30 2017-08-23 fdi:010037817 fre