Fish Kills Devastate Aquaculture in Mulukoba and Rudacho: Urgent Calls for Action

Fish Kills Devastate Aquaculture in Mulukoba and Rudacho: Urgent Calls for Action

The vibrant aquaculture industry along the shores of Lake Victoria has been rocked by a tragic incident, as fish kills at Mulukoba and Rudacho beaches have left local farmers and investors grappling with devastating losses. Reports indicate that up to 200 million Kenya shillings in agribusiness investments have been lost, putting not only fish farmers but also numerous workers, fish off-takers, and local consumers at risk.

Hon. Raphael Wanjala, the area representative, took to social media to express his deep concern, stating, “I have learnt with regret the devastating loss our fish cage farmers and investors have suffered, occasioned probably by the lake upwelling and oxygen deficiency.” He emphasized the extensive repercussions of the incident, highlighting how it disrupts the entire value chain—from production to local consumption—and calls for immediate action.

What Really Happened?

Fish farmers along the shores of Lake Victoria have been dealing with the aftermath of widespread fish deaths, with several attributing the losses to a sudden and mysterious change in water quality. Many recalled noticing a shift in the color of the lake’s water and a foul odor, with floating fish in their cages becoming a frequent sight.

One local farmer reported a gradual but troubling increase in fish deaths, estimating a loss of 50 tonnes, valued at around 5 million shillings. "We began seeing fish gasping for breath and floating on the surface, and by the end of the week, nearly all of them were dead." The incident has affected hundreds of cages across the beaches, leaving fish farmers devastated and unsure of how to salvage their businesses. Several cold storage facilities, set up for emergencies, were ill-prepared to handle the volume of dead fish, exacerbating the problem.

Farmers speculated on various causes, including possible oxygen deficiency or pollution, as they watched helplessly while their fish died. Some had spotted early warning signs through surveillance systems, noting floating fish in the cages days before the mass deaths. They reached out to the Kenya Marine and Fisheries Research Institute (KMFRI) for assistance, but initial tests suggested the water was safe, leaving many questions unanswered.

Experts, however, suspected that the fish kills were linked to a well-known environmental phenomenon in Lake Victoria—seasonal upwelling. This natural process involves the replacement of warmer surface waters with cold, oxygen-depleted waters from the lake's depths. As the colder water rises, it carries with it decomposed organic matter, which depletes oxygen levels and suffocates the fish, particularly those confined in cages. The phenomenon has historically affected Lake Victoria, particularly during the critical months of September to November and May to July.

KMFRI officials further explained that poor cage management practices, such as overcrowding and insufficient spacing between cages, had exacerbated the situation. The close proximity of the cages likely worsened water quality, increasing the risk of mass fish mortalities. It was observed that the affected areas had placed up to 160 cages in a limited space, hindering proper water circulation and contributing to the deaths.

KMFRI Findings Highlight Environmental Concerns

Following the fish kills, the Kenya Marine and Fisheries Research Institute (KMFRI) conducted an in-depth assessment that offered critical insights into the environmental factors contributing to the incident. Although the temperature and conductivity in Lake Victoria were deemed suitable for fish survival, dissolved oxygen levels at both Mulukoba and Rudacho beaches were alarmingly low, falling below global standards for aquatic life.

KMFRI’s historical data indicated that Lake Victoria experiences seasonal cycles of low-oxygen waters, a phenomenon known as upwelling. These cycles typically occur from September to November and again from May to July, aligning with the timeline of the recent fish deaths. During upwelling, cold, oxygen-depleted waters from the lake's depths replace the warmer surface water, creating anoxic conditions that are deadly for fish confined in cages. Without the ability to escape, the caged fish were the most vulnerable.

The assessment also revealed visible signs of deteriorating water quality. The affected areas reported blackish water and large quantities of floating mollusc shells—both strong indicators of poor water quality resulting from upwelling. In addition, the ongoing decomposition of organic matter in the lake had further depleted oxygen levels, exacerbating the crisis, especially in the shallow waters where most of the fish cages are located.

In response to these findings, KMFRI emphasized that localized upwelling of deoxygenated water was likely the primary cause of the mass fish deaths. They recommended several urgent measures to prevent similar incidents in the future. Proper spacing of fish cages is essential, with a recommended buffer of at least 10 meters between assemblies to improve water circulation and reduce the risk of fish mortality. Farmers were also advised to follow best aquaculture practices, such as selecting deeper waters for cage placement, which can mitigate, though not eliminate, the effects of upwelling.

KMFRI further highlighted the critical need for infrastructure development, particularly the creation of functional cold storage facilities to help farmers preserve fish during emergencies. In addition, farmers were urged to be especially vigilant during the high-risk months of September to November and May to July, monitoring the water for signs of upwelling, such as changes in color, turbidity, and oxygen levels. Simple tools, such as oxygen meters, could be instrumental in preventing future losses.

As the community grapples with the fallout from this environmental disaster, the call for collective responsibility has never been clearer. The recent fish kills should not deter investment in aquaculture; rather, they should motivate stakeholders to engage in a more sustainable and collaborative approach. The people of Mulukoba and Rudacho now look towards their leaders and the scientific community for answers, hoping that proactive measures will restore the vibrancy of their fishing industry and safeguard the health of Lake Victoria.

To prevent such disasters in the future, there is an urgent need for collective action. As AquaMnara, we remain committed to promoting sustainable aquaculture practices and supporting local farmers in adopting innovative solutions. We call on both public and private stakeholders to invest in proper fish cage management, infrastructure development, particularly cold storage facilities, and continuous monitoring systems. If we work together, we will protect Lake Victoria’s ecosystem and the livelihoods it supports. AquaMnara stands ready to lead the way in restoring the lake’s vitality.

Photo Credit: Standard Media