Reduced dissolved oxygen content in parts of Lake Victoria has been identified as the cause of massive caged fish deaths at Dunga beach in Kisumu County.
A fact finding multi–disciplinary study led by Kenya Marine and Fisheries Research Institute (KMFRI) revealed that the fish died of suffocation due to lack of oxygen.
KMFRI head of Freshwater Directorate Dr. Christopher Aura said the low oxygen concentration was caused by urbanized pollution and climate change which has resulted in algae bloom in the lake.
Changes in weather variants between cool and hot conditions, he added, has led to rapid decomposition of the algae affecting oxygen levels in the lake.
“There exists increased algae concentrations at the affected cage site that are undergoing decomposition and utilizing oxygen in the water causing low levels of oxygen which suffocates the fish,” he said.
The fish kills, he said, were exacerbated by placement of the cages in shallow waters adding that clogged fish nettings also affected water circulation.
Dr. Aura said even though fish kills have been reported in deeper waters in the lake, they were more susceptible in shallow waters.
He asked cage fish farmers in the lake to be cautious of the locations and engage the relevant authorities before placing the cages to avert further losses.
Continued vigilance on the lake use and pollution sources, he added, was paramount to ensure that water quality remains within the set standards for the fish to flourish.
Dr. Aura further asked insurance companies to come up with special tailored products for the fish farmers to cushion them against losses.
According to the KMFRI survey, the first mortality was observed on Monday 10th April, 2023 when fish were seen coming to the surface of water to gulp for air. This was followed with massive kills later the next morning.
A total of 60 stocked cages in the area with a density of 5,000 fingerlings each were affected.
The disaster which comes barely five months after a similar occurrence at Ogal and Asat beaches in Kisumu West has left farmers counting losses worth millions of shillings.
By Chris Mahandara