Fermentation of Arabinoxylan-Oligosaccharides, Oligofructose and their Monomeric Sugars by Hindgut Bacteria from Siberian Sturgeon and African Catfish in Batch Culture in vitro

The in vitro fermentation of two Non-Digestible Oligosaccharide (NDO) preparations, Arabinoxylan- Oligosaccharides (AXOS) and Oligofructose (OF), and their respective monomeric sugars, xylose and fructose, were investigated by hindgut microbiota of two major aquaculture fish species, Siberian sturgeon (Acipenser baerii) and African catfish (Clarias gariepinus). Inocula from the hindgut of both fish species were incubated for 48 h in bottles containing 1.0% of one of four substrates, i.e. AXOS, OF, xylose or fructose. Amounts and profiles of produced Short-Chain Fatty Acids (SCFAs) differed between the two fish species and substrates. The hindgut microbiota of Siberian sturgeon has a higher fermentation capacity than the microbiota from African catfish. Xylose was much easier fermented than AXOS by microbiota from Siberian sturgeon whereas OF was quicker fermented than fructose with African catfish inoculum. The SCFAs were dominated by acetic acid for both fish species and for all substrates. Fermentation of OF and fructose by hindgut microbiota of Siberian sturgeon also yielded high amounts of butyric and branched-chain fatty acids after 48 h incubation. Results of this study suggest that AXOS, OF, and their monomeric sugars have an impact on microbial fermentation activity of hindgut microbiota from Siberian sturgeon and African catfish in a substrate and species dependent manner

Food habits and trophic resource partitioning among three mormyrid fishes from man-made Lake Ayame, Ivory Coast

Feeding habits and trophic relationships among three mormyrid species  (Petrocephalus bovei, Marcusenius ussheri and Marcusenius furcidens) were assessed in the man-made Lake Ayame in Ivory Coast. The index of preponderance combining the occurrence and weight percentages of the identified prey items  showed that these three mormyrid species mainly feed on invertebrates, especially aquatic insects. Petrocephalus bovei mainly feeds on chaoborid larvae, whereas both Marcusenius species preferentially feed on chironomid larvae. This segregation of food items associated with the relative  abundance of chironomid larvae may reduce interspecific competition between these three fish species, and may therefore allow their  coexistence. Horn’s food overlap index revealed highly significant similarities in the trophic spectrum between both   Marcusenius species, and for the dry as well as the rainy season.Key words: Mormyridae, feeding, competition, man-made lake, Ivory Coast, West Africa

Influence des facteurs environnementaux sur la répartition spatiale des crevettes dans un petit bassin ouest africain – rivière Boubo- Côte d'Ivoire

Environnemental Control of Shrimps Communities Structure along a Small West African Basin- Boubo River- Ivory Coast. The relationship between shrimps species and environmental variables were studied in Boubo River, a costal river in Ivory Coast. The river is submitted to the impact of human activities (dam construction and oils factory). This survey achieved for the first time in the Boubo River permitted to put in evidence nine freshwater shrimps species [Atya africana (Bouvier 1904), Caridina africana (Kingsley, 1882), Caridina nilotica (P. Roux 1833), Desmocaris trispinosa (Aurivillius 1898), Macrobrachium vollenhovenii (Herklots 1851), Macrobrachium macrobrachion (Herklots 1851), Macrobrachium felicinum (Holthuis 1949), Macrobrachium dux (Lenz 1910) and Macrobrachium sollaudii (De Man 1912)] belonging to two families (Atyidae and Palaemonidae) and four genera (Atya, Caridina, Desmocaris and Macrobrachium) were captured. Significant correlation between habitat characteristics and presence or absence of shrimps species suggest that rocky, leaves and death-woods substrates, canopy closure, width, depth and transparency were the main environmental variables influencing shrimps distribution