Biodiversity and Distribution of Bivalve Molluscs in three Areas of the Ebrié Lagoon (Côte d'Ivoire)
KOUAKOU Kouassi Fidèle
*
Animal Production Laboratory, Institut National Polytechnique Félix HOUPHOUET-BOIGNY, Yamoussoukro, Ivory Coast.
QUENUM Crespin Luc
Animal Production Laboratory, Institut National Polytechnique Félix HOUPHOUET-BOIGNY, Yamoussoukro, Ivory Coast.
ALLA Eby Yoboué Gnamma Honorine
Animal Production Laboratory, Nangui Abrogoua University, Abidjan, Ivory Coast.
*Author to whom correspondence should be addressed.
Abstract
Lagoon environments are ecosystems that change continuously according to environmental and especially climatic conditions. This instability that characterizes these very particular biotopes has a direct impact on the biocenosis that colonizes them and, in particular, the benthic fauna composed mainly of sedentary species. The present study was carried out to assess the biodiversity of bivalve molluscs in the Ebrié lagoon has identified six species (Crassostrea gasar, Mytilus edulis, Dendrostea frons, Crassostrea cucullata, Mytilus lineatus and Senelia senelis). The animals were caught during experimental fishing carried out in sectors II, III and IV of the Ébrié lagoon. However, of all the species sampled, Crassostrea gasar was found to be the majority at all three sites and on all sampling substrates. The identification is based on the morphology of the gills for the classification of the bivalve into four Orders (Prosobranch, Filibranch, Eulamellibranch and Septibranch). It is also based on morphomeric criteria, which are the number of teeth at the hinge, the number of adductor muscles, the position of the line and the pallial sinus of the shells. The degree of bivalve population organization at the sampled sites was analyzed through the Shannon (H) and Equitability (E) diversity indices. Both qualitative and quantitative differences were found between the species sampled at the different sites. In Moossou, there was one rare species, one commune and four frequent. At Bimbresso, there were two accidental species and three frequent ones. In Lokodjro, one common species and three frequent species. The indices do not vary significantly from one site to another. However, the maximum values of the diversity and equitability index are obtained in Moossou (1.22 and 0.78). Overall, the samples collected are dominated mainly by one family (Ostreidea). Specifically, it is C. gasar that dominates on all sampled sites and in all seasons. The Shannon index is higher during the flood season in Moossou and Lokodjro. This could be explained by the fact that these two sites are closer to the sea than the third and fed by coastal canals and rivers. The Ostreidea family dominates the samples with three species. However, Crassostrea gasar is the majority species at the three sampling sites.
Keywords: Biodiversity, bivalves, ebrié lagoon, Ivory Coast