Abstract:
Aquatic ecosystem health assessment is critical for early detection of disturbances and water
habitat degradation. This study assessed the ecological status of two urban rivers as well a
wastewater sedimentation pond in Kisumu City, Kenya using physico-chemical water quality
parameters and the African catfish, Clarias gariepinus somatic indices. Site association of somatic
indices was derived from Principal Component Analysis (PCA) whereas the relationship between
water quality parameters was examined by Redundancy Ordination Analysis (RDA). PCA results
revealed an increase in Gill Somatic Index (GSI) in the wastewater sedimentation ponds while
Fulton’s Condition Factor (CF) increased in the midstream of Auji river and Kisat river mouth.
Similarly, RDA showed that dissolved oxygen, temperature, total phosphorus, alkalinity and total
nitrogen influenced the condition indices upstream of Kisat river and up-stream and midstream of
Auji river. However more impact on somatic indices were recorded in the wastewater
sedimentation pond. Although specific pollutants other than the physico-chemical parameters were
not identified, application of somatic indices in the African catfish demonstrated that the two rivers
as well as the wastewater sedimentation pond were contaminated by pollutants that can
compromise the ecological health of the aquatic systems. The results of this study emphasized the
negative impacts of anthropogenic activities on the environment.
