The Kenya Marine and Fisheries Research Institute (KMFRI) has developed a map to guide the installation of fish cages in Lake Victoria, following significant fish kills that have resulted in millions of shillings in losses for farmers in Kisumu and Busia counties. To address this issue, KMFRI has pinpointed optimal locations for cage fish farming, focusing on maximizing production while mitigating risks.
Christopher Aura, the Freshwater Systems Research Director at KMFRI, explained that the identified areas were determined through thorough research and economic considerations. “Research has informed mapping by considering factors such as water quality, depth, security, and proximity to landing sites,” he stated.
The mapping process also took into account fish breeding grounds and the lake’s currents, which can lead to upwelling—a natural phenomenon that causes deep, cold water to rise to the surface. Recent massive fish kills in Busia have been linked to this upwelling. “When upwelling occurs and the deep waters come to the surface, it leads to fish kills because the water lacks sufficient oxygen due to the decomposition of organic matter, depleting oxygen levels,” Aura explained.
This phenomenon, documented in Lake Victoria since 1990, typically occurs in May, June, September, and October. “It is not new, and it occurs even in the natural environment. The reason we are seeing massive fish kills in cages during upwelling is that the fish cannot escape when there is oxygen deficiency,” he noted.
The suitability map indicates that farmers should avoid placing cages in shallow water, as depths of six to ten meters, although suitable, are vulnerable to the negative impacts of upwelling. Aura urged farmers to collaborate and install cages at the locations identified by KMFRI to reap the benefits of the venture. “Locations in deep waters are the most suitable. However, building the cages and ensuring security requires significant resources,” he added.
He also encouraged farmers to invest in oxygen meters to regularly monitor oxygen levels in the cages, emphasizing the importance of maintaining fish stocks. “Farmers must invest in cold storage facilities to harvest and store their fish in case of emergencies. Additionally, they should routinely check water quality and make informed decisions to avoid losses,” Aura advised.
According to KMFRI, Lake Victoria has an estimated carrying capacity of 25,427 cages. Currently, the lake hosts around 6,000 fish cages covering 62,132 square meters, with an annual production capacity exceeding 10,000 tonnes, primarily consisting of Nile perch and tilapia.
