Le régime alimentaire de Schilbe multitaeniatus (Pellegrin, 1913) (Siluriforme, Schilbeidae) de la rivière Rembo Bongo au Gabon (Afrique Centrale)

S. multitaeniatus est un Schilbeidae tres capture et apprecie des eaux  douces du Gabon. Sa bioecologie peu etudiee a fait lfobjet dfune attention particuliere dans lfoptique de gerer durablement, de proteger et  entreprendre des essais de domestication en elevage de lfespece. De juin 2010 a decembre 2011, une etude experimentale de son regime  alimentaire a ete faite dans la riviere Rembo Bongo par lfanalyse de 292estomacs de poissons peches aux filets dormants de mailles 10, 15, 20, 25 30, 35, 40 et 50 mm. Les resultats ont montre que son alimentation est variee et constituee dfinsectes (Io = 36,5%; Iab= 29,29%), de poissons (Io= 24,31%; Iab = 18,18%), de debris dfanimaux (Io =  12,16%; Iab = 9,1%), de crustaces (Io = 4,06%; Iab = 5,05%), dfarachnides (Io = 1,35%; Iab = 1,01%), de fruits (Io = 13,51%; Iab = 28,28%) et de debris de vegetaux (Io = 6,76%; Iab = 6,06%). Cette alimentation differe entre jeunes-adultes (α = 0) dfune part et entresaisons de pluies et saison seche (α = -20) dfautre part. Globalement, lfespece a un regime omnivore a tendance ichtyophage, toutefois, avec une preference dfinsectes au stade jeune et de poissons au stade adulte.c 2013 International Formulae Group. All rights reserved.Mots cles : Cours dfeau, Siluriforme, Schilbe multitaeniatus, alimentatio

Landscape control on the spatial and temporal variability of chromophoric dissolved organic matter and dissolved organic carbon in large African rivers

© 2015, Springer Science+Business Media New York. The characteristics of colored dissolved organic matter (CDOM) as well as the concentrations and stable isotope composition (δ13C) of dissolved organic carbon (DOC) were characterized in several large rivers of Africa including the Congo, Niger, Zambezi, and Ogooué basins. We compared the spatial and temporal patterns of dissolved organic matter (DOM) quantity and quality along with various environmental gradients, including hydrology, river size, catchment vegetation, and connectivity to land. The optical proxies used include the absorption coefficient at 350 nm, the specific ultra-violet absorbance, and the spectral slope ratio (SR = 275–295-nm slope divided by 350–400-nm slope). Our results show that land cover plays a primary role in controlling both DOC concentration and optical properties of DOM in tropical freshwaters. A higher cover of dense forest in the catchment leads to a higher quantity of highly aromatic DOM in the river network, whereas an increasing savannah cover results in lower DOC concentrations and less absorptive DOM. In addition to land cover, the watershed morphology (expressed by the average slope) exerts a strong control on DOC and CDOM in tropical rivers. Our results also show that the percentage of C3 and C4 vegetation cover is not an accurate predictor for DOM and CDOM quality in rivers due to the importance of the spatial distribution of land cover within the drainage network. The comparison of our results with previously published CDOM data in temperate and high-latitude rivers highlights that DOM in tropical freshwaters is generally more aromatic, and shows a higher capacity for absorbing sunlight irradiance.status: publishe