Fish diversity and assemblages according to distance from source along a coastal river gradient (Ehania River south-east of Ivory Coast)

Fish assemblage was investigated during the study of longitudinal profile of the Ehania River Basin in south-eastern Côte d’Ivoire. This area is subjected to intense human activities with many plantations (palm tree, banana, pineapple, coffee, rubber and cocoa). Samples were collected, with gillnets of different mesh sizes, through 6 sampling surveys during dry and rainy seasons from February 2010 to December 2010 at 6 sampling sites. A total of 70 fish species belonging to 48 genera, 28 families and 10 orders were recorded. The temporal variation of diversity index is less marked than spatial variation. The upstream, with 35 species, was less rich in species than the medium area and downstream areas (respectively 46 and 68). The upstream and downstream areas gathered 35 species. Thirty three species were common to the upper and middle areas and 46 species appeared both in the lower courses and the middle area. The 21 species restricted to the lower part of the river are mainly estuarine/marine origin. The beta diversity value revealed low similarity between the lower and upper course of Ehania River. The lowest values of Shannon’s diversity index and equitability index were observed in the middle part of the River which characterized by high population density and intense agricultural activity with many plantations

Variations altitudinale et saisonnière de l’abondance de deux crevettes Atyidae dans les cours d’eau du mont Simandou (Guinée)

Les crevettes Caridinopsis chevalieri Bouvier, 1912 et Caridina africana Kingsley, 1883 sont les plus rencontrées dans les cours d’eau du mont Simandou (Guinée). Les variations altitudinale et saisonnière de leur abondance sont discutées dans la présente étude. Deux campagnes d’échantillonnage (saisons sèche et pluvieuse) ont été effectuées sur 27 sites en 2011. Des paramètres physico-chimiques ont été mesurés avant l’échantillonnage des crevettes en vue de la caractérisation du milieu. Au total, 323 individus de crevettes dont 57% de C. chevalieri et 43% de C. africana ont été collectés. En basse altitude (< 650m), la population est dominée par C. africana (79%). Par contre, en haute altitude (> 650m), C. chevalieri est le plus abondant (71%). C. chevalieri est plus rencontré en saison sèche alors que C. africana prédomine la population en saison des pluies. La conductivité, la température, le pH, la vitesse du courant et le type d’habitat sont les principaux paramètres du milieu qui influencent la distribution spatio-temporelle de l’abondance des deux espèces étudiées. Cette étude présente les données préliminaires sur les crevettes du mont Simandou et constitue une base importante pour des études futures sur la diversité et l’écologie de faune de crustacés de cette zone.Mots clés: Crevette, Caridina africana, Caridinopsis chevalieri, abondance, Mont SimandouEnglish Title: Altitudinal and seasonal variations in the abundance of two Atyidae shrimps in the streams of Mount Simandou (Guinea)English AbstractThe shrimp Caridinopsis chevalieri Bouvier, 1912 and Caridina africana Kingsley, 1883 are the most encountered in the rivers of the Simandou Mountain (Guinea). The altitudinal and seasonal variations in abundance of both species are discussed in this study. Two sampling campaigns (dry and rainy season) were conducted at 27 sites during year 2011. Some physical and chemical parameters were measured before sampling shrimp in order to the characterization of the environment. A total of 323 individuals of shrimp comprising 57% of C. chevalieri and 43% C. africana were collected. In low altitude (<650m), the population is dominated by C. africana. (79%). On the other hand, at high altitude (> 650m), C. chevalieri is the most abundant (71%). C. chevalieri is most sampled during the dry season while C. africana dominates shrimp population in the rainy season. The conductivity, temperature, pH, dissolved oxygen and the type of habitat are the main environmental parameters that influence the spatial and temporal distribution of the abundance of the two studied species. This research presents preliminary data on shrimp from Simandou Mountain and is an important basis for future studies on diversity and ecology of crustacean from this area.Keywords: Shrimp, Caridina africana, Caridinopsis chevalieri, abundance, Simandou Mountai

Freshwater snail distribution related to environmental factors in Banco National Park, an urban reserve in the Ivory Coast (West Africa)

Freshwater snails and environmental variables were studied at seven stations along the Banco River (Ivory Coast;West Africa) from March to October 2008. Two species (Physa marmorata (Physidae) and Bulinus forskalii (Planorbidae) were recorded only at one sampling site. This station which received domestic sewage from the neighbouring cities was characterized by the highest conductivity and pH and the lowest values of dissolved oxygen. Multiple stepwise regression analysis showed that snail densities were probably influenced by conductivity, dissolved oxygen, pH, and canopy cover. Also, snail dynamics showed a seasonal pattern, with peak population densities and recruitment of young generations during rainy periods. This study highlighted the impacts of sewage on snail diversity and distribution in the Banco River. Overall, this paper strengthens the viewpoint that the Banco River management should be implemented to lessen the impact of anthropogenic activities on the ecology of the Banco National Park.Key words: freshwater snails, dynamic, Banco River, Ivory Coast