Food and feeding relationships of fish in the Sudd swamps (River Nile, southern Sudan)

The gut contents of 37 species of R. Nile fish are described. Classification according to diet shows four species to be mud‐feeders, three to be microherbivores, two to be macroherbivores and five to be omnivores. The remaining majority (23) are categorized as carnivorous and comprise one neuston‐feeder, one zooplanktivore, six bottom‐feeders, seven browsers in vegetation and eight macropredators. Food webs are proposed for three major ecological zones, namely the open‐water and submerged vegetation of a river‐lake, the floating fringe of Eichhornia crassipes and the seasonally flooded grassland.