High fish death rates in Lake Victoria explained; problem areas detailed
Thursday, November 13, 2003
The Nation (Nairobi,Kenya) by Allan Odhiambo
Excessive nutrient flow into Lake Victoria owing to misuse of fertiliser in neighbouring farmlands has been blamed for the rising cases of fish deaths.
The nutrients are said to cause eutrophication (excessive richness in nutrients) and algae bloom that eats up respiratory oxygen in the lake water, according to a report by Nyanza provincial director of environment, Mr Maurice Nyunja.
Only four main fish species remain in the lake today compared to more than 300 species registered in the 1970s due to over-fishing, according to the document. Lates nilotica, oreochromis nilotica, orewochromis leucosicus and tilapia zilli species are dominant in the lake.
The official said the introduction of Nile perch in the lake had led to extinction of some fish species and blamed it on lack of prior environmental impact assessment before being released into the water mass.
"Environmental impact assessment as a concept had not emerged then and no meaningful analysis was done before introducing the specie that is now eating up the rest." He said.
Mr Nyunja descried the increasing threats to lake wetlands owing to reclamation for agriculture and settlement as well as deforestation that he said had led to erosion and siltation of swamps.
Yala, Nyando and Kisii valley were named as most endangered wetlands due to reclamation, the official said, but warned that the latter further faced threats from brick making activities owing to its high quality soils especially on the Sironga stretch.
The official also took issue with Kisumu and Homa Bay municipal councils for threatening the lake biodiversity by spewing raw sewer from their broken down conventional sewerage systems.
The report was presented yesterday during the on-going international seminar on community based small scale activities within the lake region, and the impact on environment in Kisumu. It is organised by the Community Based Impact Assessment Network for Eastern Africa (CIANEA) and brings together environmental experts from Eastern Africa.