Daily variations in the diet of the freshwater oyster Etheria elliptica (Lamarck, 1807) in the Pendjari River (Benin)

Abstract

Variations in the diet of the oyster Etheria elliptica were studied over a daily cycle at the Pendjari River. Stomach content items were identified. Diet composition was analyzed using the point alloted method. The oyster fed mainly of phytoplankton (99.55%) and zooplankton (0.41%). The Diatoms Coscinodiscus rudolfii (31.73%) and Eunotia bilunaris (23.93%) constitute the preferential foods, while the Cyanophytes (Microcoleus lacustris, 14.15%) and the Chlorophytes Stigeoclonium aestivale (10.64%) and Gonatozygon monotaenium (9.13%) are the secondary foods. The other are additional food items. On the daily cycle, the trophic activity is intense almost all day with a preference for the night hours between 6 p.m -12 a.m. The diet compositions showed significant variations between the hours of the day (9 a.m. to 6 p.m.) and night (9 p.m. to 6 a.m.). Etheria elliptica is a phytophagous with a varied trophic activity, feeding mainly on diatoms. The trophic activity intensifies during the night hours.