Kenya Marine and Fisheries Research Institute (KEMFRI) have termed the mysterious deaths of fish in Lake Victoria as a periodical normal occurrence.
Assistant Director Fresh Water Aquaculture Dr. Paul Orina said the same phenomenon was witnessed five years ago, only that it lasted a week, unlike the current situation that has lasted for almost a month resulting into a greater impact.
Photos posted on social media show dozens of lifeless fish washed up ashore at Lake Victoria, as well as Lake Kyoga and River Nile.
Lake Victoria is a vital resource shared by Uganda, Kenya and Tanzania.
Aquaculture research scientist attributed the deaths to disturbance of the structure and conditions of the lake through mixing of the top, middle and the bottom layers of water mainly due to winds, floods, inflow and outflow of water causing a drop in oxygen levels.
“This affects the levels of oxygen and chemicals thus affecting the fish which have different adherence to different levels of oxygen,” he said.
He explained that Nile Perch (locally known as Mbuta) of all sizes were the most affected in the temporal lake occurrence owing to their high oxygen demand as is currently been witnessed in the counties along the lake with Siaya reporting the highest number of deaths.
He also cited Burbus (Othatho) and Labeo (Ningu) as species with high oxygen demand but their deaths were lower because their numbers were few due to declining fisheries in the lake.
He said Tilapia (Ngege), Catfish (Mumi) and lungfish (Kamongo) are resilient species which are not easily affected by the lake’s seasonal occurrence which could also be due to climate change.
However, Dr, Orina noted that one way of ensuring that oxygen levels of the lake did not vary with a big margin at different density levels was by maintaining a clean ecosystem adding it was key in ensuring the over five million people that depend on the lake continued to access clean water as per the Sustainable Development Goals (Global Goals).
“This calls for fast implementation of the water quality regulation whose objective is to prohibit the discharge of effluent into the environment in a bid to preserve the aquaculture industry and wild fisheries which are critical in ensuring food security in the country,” said Dr. Orina.