| dc.description.abstract | The disappearance of haplochromines in Lake Victoria has been attributed to. among other
factors, predation by the introduced Nile perch, Lates niloticus (Linnaeus, 1758). Lake Sare a
satellite lake with an open direct dispersal corridor to Lake Victoria exhibits a unique
phenomenon of coexistence of Nile perch and haplochromines. Other satellite lakes:
Kanyaboli and Namboyo of Lake Victoria are home to several endemic haplochromines but
are free from Nile perch invasion. This study has investigated the current size structure of
Lake Sare Nile perch to establish their impact on the haplochromine population and the role
of resource partitioning between the two fishes in order to determine the factors that control
their co-existence. Surveys were conducted and a total of 1317 fish specimens obtained
including 375 haplochromines, 315 Nile perch and 627 specimens comprising mainly of
Brycinus spp., Mormyrids, Synodontis spp., Gambusia sp. and tilapiines. Species diversity
Shannon-Wiener Index (H'= 1.8429), species richness (d =1.2529) and evenness (J =0.8004)
were relatively low. The Nile perch population was predominantly immature (85.7%); in
contrast, the haplochromine population comprised about 60% mature stages. There was
minimal dietary overlap between Nile perch and haplochromines as shown by similarity
index of shared food categories; plant materials (0.6090) where intake in Nile perch was of
insignificant quantity and probably resulted from incidental intake rather than deliberate
feeding, insects (0.2102) and Molluscs (0.1238). Although haplochromines of Lake Sare do
not have an absolute size refuge from Nile perch, most of the haplochromines' body depth
measurements fall within the same range as most mouth gape measurements of Nile perch
(range 12 mm to 45 mm) thus according partial size refuge to the former, leading to their
coexistence. Generally, the physico-chemical parameters were uniform throughout the lake.
However, secchi disc transparency was highest in the open water portion of the lake, whereas
turbidity was highest where River Yala enters the lake. Lake Sare haplochromines could
potentially be a source of seeds of resurgence in Lake Victoria as there is an open direct
dispersal corridor between the two lakes. | en_US |
