الفهرس 
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Abstract
Benthic organisms are those organisms which survive on
the bottom of the different aquatic habitats, either atta- ched or limited in their motility. They are usually adapted to the different environmental conditions prevailing at the bottom. According to water depth, there are two major habi- tats, namely; the littoral zone and the deeper localities.
Very little quantitative investigations on benthos have been carried out in the Nile system (C.F. Monakov, 1969 on the White Nile). According to Rzoska (1976), the shore fauna of the Nile system is rich where there is fringing vegetation as in Lake Victoria and along parts of the White Nile, while it is poor in the Blue Nile with partly steep shores and drastic changes of water level. In Lake Victoria, benthic animal were indirectly studied through observations that deal with emergencies of the adult insects whose larvae form a large part of benthos. About a dozen different chironomid species have been studied, but mostly identifica- tion denotes only generic or family names. Their quantitative distribution in the bottom sediments was further studied by MacDonald (1956). Mandahl-Barth (1954) listed 126 species of molluscs in Uganda and adjacent territories (86 gastropods and 40 bivalves). Of these, 65 species and subspecies, were also recorded in Lake Victoria.