Food and feeding habits of Gnathonemus petersii (Osteichthyes: Mormyridae) in Anambra River, Nigeria

The food and feeding habits of Gnathonemus petersii (Osteichthyes: Mormyridae) were investigated for a period of 18 months in the Anambra river. Fish samples were collected monthly at Otuocha and Ogurugu river ports along the Anambra River using multiple fishing gears. The most dominant food group was Insecta (IFS = 48.23) followed by detritus (IFS = 31.07) while the least was Arachnida (IFS = 0.20). Variation in the stomach fullness condition showed that 64 (19.10%) of the studied stomach were empty, 71 (21.19%) were full, while 200 (59.70%) were partially (1/2, 1/4 and 3/4) filled. Stomachs were generally full during the rains when feeding intensity was high while partially filled stomachs predominated in the dry season. Whereas the IFS of five (5) food categories were higher in females, only three (3) were higher in the males (t-test, P < 0.05 in all cases). Other food categories were not sex dependent. Food richness and diet breadth showed no significant difference between the sexes but not seasons. The trophic variations in G. petersii in relationship with the physiochemical parameters of the river are discussed.