Researchers are warning that the over-exploitation of a small type of fish locally known as Fulu threatens the population of the Nile Perch in Lake Victoria.
The new report cautions that fishermen should avoid harvesting Fulu because it is the main prey for Nile Perch, and which essentially helps to sustain their population in the lake.
Fulu are smaller fish grouped scientifically as haplochromines (or haps) and are commonly found in most fresh water bodies in East Africa.
The study, titled “Prediction of Lake Victoria’s response to varied fishing regimes using the Atlantis ecosystem model” conducted by Uganda’s National Fisheries Research Institute, the Kenya Marine and Fisheries Research Institute (KMFRI) and the Marine Research Institute of Iceland, found that protecting the Fulu species will lead to an increase in the Nile Perch species, while at same time reducing water pollution in the lake.
Kisumu’s KMFRI director of inland fishing and limnology Chrispine Nyamweya said the Fulu species feed on the algae in the lake.
“The lake water has a high infestation of algae; the Fulu (haplochromines) feed on the algae therefore improving the water quality,” Dr Nyamweya said.
“With the introduction of the Nile Perch species in the lake in the 1980s to reduce the population of the Fulu, the lake started turning green because of the algae.”
He said if the government places a ban on the harvest of the Fulu species, this will provide enough feed for the Nile Perch, which has a high commercial demand.
“What helps is reducing fishing pressure on the prey species for Nile Perch.
"When we stop fishing them, then we have more Nile Perch in the lake because they have enough to feed on,” he said.
Fishing has continually increased since the Nile Perch boom in the 1980s, resulting in decline of the fish stocks.
Using Atlantis ecosystem model, the study said the Nile Perch population cannot be sustained without protection of the Fulu.
“Reducing the pressure on fishing Nile Perch does not help so much. The biomass will double up but shortly after they will collapse to exhaustion,” the study shows.