Abstract:

Prior to the introduction and establishment of Nile perch Lates niloticus, haplochromine
cichlids were the most abundant and speciose group of fishes in lakes Victoria, Kyoga and
Nabugabo. They occupied virtually all trophic levels and played an important role in the
flow of organic matter in these ecosystems. Following the establishment of Nile perch,
stocks of haplochromines declined rapidly, and some species completely disappeared. This
was accompanied by drastic changes in biological and physico-chemical conditions in Lake
Victoria. Recent studies on fish stocks of Lake Victoria have been confined to offshore
waters. Ln this study, the distribution, relative abundance and food of surviving
haplochromine cichlids in littoral areas of Lake Victoria were examined to find out the
species diversity in the zone and specifically the food of the haplochromines. The data
were compared with historical data to see whether the distribution, relative abundance,
and diet of the haplochromines have changed and what role the surviving haplochromine
species were playing in the trophic ecology of the lake. The study was based in the
Napoleon gulf of Lake Victoria.
Twelve fish taxa were recorded. Numerically, the Nile perch Lates niloticus, dominated
the catch (42.3%) followed by haplochromines (30.7%), Oreochromis niloticus (12.2%),
Tilapia zillii (8.9%), Synodontis afrofischeri (2.3%), Brycinus sadleri (1.9%), Mormyrus
kannume (0.5%), Oreochromis leucostictus (0.4%), Synodontis victoriae (0.4%), Clarias
gariepinus(Q.2%), Oreochromis variabilis (0.1%), and Protopterus aethiopicus (0.1%).
Fish diversity and abundance decreased with increasing distance from the shoreline and
varied between stations. It was highest at Rwamafuta (1.12), followed by Kikondo (1.1),
Kiryowa (1.07), Kirinya (0.74) and Cliff (0.61).
Twenty three haplochromine species were recorded. These were, in order of numerical
abundance, Astatoreochromis alluaudi (17.9%), Astatotilapia "unicuspid" (14.8%),
Prognathochromis paraguiarti (12.7%), Paralabidochromis "yellowbody" (10.6%),
Paralabidochromis "goldchest" (9.8%), Harpagochromis guiarti (7.5%), Astatotilapia
nubila (6.5%), Astatotilapia "bicuspid" (4.2%), Neochromis "scraperteeth" (3.2%),
Neochromis nigricans (2.8%), Paralabidochromis crassilabris (1.6%), Paralabidochromis