Food and Feeding Habits of Clarias gariepinus and Oreochromis niloticus from Merowe Lake Reservoir, Sudan

Information on dietary composition and feeding patterns of economically important freshwater fish in Merowe Reservoir remains limited, particularly regarding temporal and spatial variation. This study examined the stomach contents of Oreochromis niloticus and Clarias gariepinus, with emphasis on monthly and location-related differences. A total of 398 specimens of each species were collected with gillnets and traditional local nets between September 2021 and August 2022. Stomach contents were examined visually and microscopically, and food items were assessed using frequency of occurrence and percentage abundance. For O. niloticus, plant material was the most prominent recorded food category (53.1%), followed by sand/mud (43.4%), blue-green algae (36.6%), green algae (24.8%), zooplankton (21.4%) and unidentified food (17.2%). For C. gariepinus, the reported categories included sand/mud (approximately 79%), insect parts (69.7%), zooplankton (54.9%) and fish remains (32.6%). The recorded food categories varied among months and sampling locations. At Sad, unidentified food reached 60% of the location-specific values for O. niloticus, while zooplankton reached 45.2% at Bearty and green algae reached 44.4% at Shery. For C. gariepinus, fish remains reached 38.6% at Shery. The observations indicate that both species consumed diverse food categories and exhibited temporal and spatial differences in recorded stomach contents. These findings provide descriptive baseline information for future assessments of feeding ecology in the reservoir.