Key-words:macroinvertebrates, communities, macrophyte habitats, tropical lake An ecological study was done on Lake Taabo with the main objective of characterising macroinvertebrate communities associated with the microhabitats created mainly by Eichhornia crassipes and other littoral native macrophytes. We sampled organisms in patches of those aquatic macrophytes. Also, some abiotic variables (temperature, transparency, turbidity, pH, TDS, conductivity, dissolved oxygen, NH 2 ) were measured. Overall, forty-three taxa of macroinvertebrates were identified. Ten of them were exclusively associated with water hyacinth while five were only associated with littoral macrophytes. Macroinvertebrate taxa with some of the highest family richness were Gastropoda, Coleoptera, Heteroptera, Odonata and Diptera. The taxon with highest density in both microhabitats was Chironomidae. Although higher values of taxonomic richness (Rs), the Shannon index (H ) and evenness (J) were obtained with the water hyacinth habitat, significant differences between the two microhabitats were not observed. Canonical Correspondence Analysis revealed that samples of E. crassipes collected in the dry season were characterised by Gastropoda and Odonata, as well as higher values of transparency and ammonia-nitrogen. Baetidae, Hydrophilidae, Chironomidae, Ceratopogonidae, Coenagrionidae, Naucoridae and Ostracoda were most abundant in both E. crassipes and littoral macrophyte habitats during the rainy season. This season was characterised by higher levels of nitrates and conductivity. été mesurées. Au total, quarante-trois taxa de macroinvertébrés ont été identifiés. Dix d'entre eux étaient exclusivement associés à la jacinthe d'eau tandis que cinq étaient seulement associés à la végétation indigène. Les taxa de macroinvertébrés ayant les richesses les plus élevées en terme de famille sont les gastéropodes, coléoptères, hétéroptères, odonates et diptères. Le taxon avec la densité la plus élevée dans les deux microhabitats était la famille des Chironomidae. Bien que les valeurs les plus grandes de richesse taxonomique (Rs), d'indice de Shannon (H ) et d'équitabilité (J) soient obtenues au sein de la jacinthe d'eau, aucune différence significative entre les deux microhabitats n'a été observée. L'analyse canonique des correspondances a révélé que les échantillons de E. crassipes collectés en saison sèche étaient caractérisés par les gastéropodes et les odonates, aussi bien que les valeurs les plus élevées de transparence et d'ammonium. Les Baetidae, Hydrophilidae, Chironomidae, Ceratopogonidae, Coenagrionidae, Naucoridae et Ostracodes sont les plus abondants dans les deux habitats pendant la saison pluvieuse. Cette saison est caractérisée par des valeurs élevées des nitrates et de la conductivité. RÉSUMÉ

2010) Aquatic macroinvertebrate assemblages associated with root masses of water hyacinths, Eichhornia crassipes (Mart.) Solms-Laubach, 1883 (Commelinales:We examined aquatic macroinvertebrates associated with Eichhornia crassipes roots at five sampling sites in Taabo Lake. An average density of 1644 individuals (ind.)/m 2 was recorded. In total, 68 macroinvertebrate taxa belonging to 34 families and 14 orders were identified. Among these, Insecta was predominant (77.94%). The highest densities were recorded at Taabo cité during both rainy and dry seasons. Taxon diversity differences were not observed among all stations according to a Kruskal-Wallis test. High densities of predators were recorded. Next most prevalent in the trophic structure were detritivores. Indicator taxa analysis, using the Indval method, showed that stations upstream of the lake were characterized by eight taxa, while 11 appeared as indicators of the station near the dyke. Predators and herbivores dominated within those indicators. Sites near bays were distinguished by 18 indicator taxa with a predominance of predators and detritivores. Conductivity, NH 4 + , temperature, PO 4 3− , turbidity and dissolved oxygen were parameters that strongly influenced the macroinvertebrate community.

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The growth of Brycinus longipinnis caught at Aghien Lagoon was studied between June 2014 and May 2015 through growth type, condition factor and growth parameters according to the Von Bertalanffy model. Sampling was conducted using experimental fisheries. Growth type was determined from the length-weight relationship and growth parameters according to the Von Bertalanffy model from the FiSAT software. The growth was of negative allometric type (b = 2.59). The Brycinus longipinnis population grows faster towards the asymptotic length ((L∞ = 92.40 mm SL) with a growth coefficient K of 0.36 year-1. It is also a long-lived fish species with maximum longevity (tmax) of 8.32 years.