KMFRI warns of potential risk of mass fish deaths in Lake Victoria

The Kenya Marine and Fisheries Research Institute (KMFRI) has issued an advisory to cage fish farmers in Lake Victoria to either reduce or suspend feeding their fish to avert losses stemming from the mass death of fish.

In a notice released on Thursday, KMFRI Assistant Director Chrisphine Nyamweya indicated that an early warning system installed at Dunga Beach showed that oxygen levels had fallen below 2 mg/l over the last several days, a condition that will likely cause mass death of fish in the lake.

“The onset of heavy rainfall around Lake Victoria in the past week has triggered significant disturbances in the lake’s water column. The dropping of oxygen levels below the minimum threshold is lethal for cultured fish species, including **tilapia,” said Dr. Nyamweya.

The system also recorded fluctuations in the lake’s pH levels, which may interfere with gill function, reduce feeding, and increase the risk of the fish contracting diseases.

KMFRI also sounded the alarm on the flip side of routine feeding and its impact on the overall health of fish.

“Uneaten feed and fish excretion consume dissolved oxygen during decomposition. Cutting feeding reduces the biological oxygen demand in and around cages.”

The research institute has also advised cage farmers in the Winam Gulf in Kisumu County, Siaya County, Busia County, Homa Bay County, and Migori County to partially harvest fish that have reached near-marketable size to reduce stocking density and minimize potential losses.

Cage fish farmers lost an estimated one billion shillings’ worth of fish in 2024 and 2025 following the massive sudden death of fish in cages due to suffocation.

Farmers have also been advised to move their cages into areas with better water circulation and to report any fish mortalities to KMFRI, the Kenya Fisheries Service, the State Department for the Blue Economy and Fisheries, Beach Management Units (BMUs), or their respective county fisheries officers.