Feeding ecology of Marcusenius senegalensis (Pisces: Osteoglossiformes: Mormyridae; Steindachner, 1870) from Niger River in Northern Benin

Abstract

Also known as bulldog fish, Marcusenius senegalensis is the dominant Mormyrid in Niger River in Northern Benin where the species is intensively exploited for sale and subsistence. The current research investigated the trophic ecology of this electric fish in order to document resource exploitation and feeding habits. Marcusenius senegalensis individuals were sampled monthly and stomach contents of the 2019 individuals collected were analyzed. The results indicated that Marcusenius senegalensis is an invertivore consuming a wide spectrum of food resources dominated by aquatic insects (74.38%), detritus (8.98%), sand particles (8.19%), crustaceans (3.92%), mollusks (2.51%) and phytoplankton (1.13%). Diet breadths were high and varied between 2.22 and 4.98, leading to a trophic plasticity behavior of the species. Diet overlaps between size classes were greater and averaged (Øjk)= 0.88. In Niger River, feeding grounds are now being severely degraded. Sustainable exploitation of Marcusenius senegalensis requires a community-based approach of habitat protection and conservation of this valuable Mormyrid.