“It was horrific,” Alan Ochieng says of the catastrophe that struck Lake Victoria fish farmers late final 12 months.
Hundreds of fish died when Africa’s largest lake witnessed a pure and recurring phenomenon generally known as backside water rising to the floor.
This happens when deep water mixes with floor water, inflicting a sudden depletion of dissolved oxygen within the water, killing fish.
Some farmers consider excessive algae ranges or air pollution might have performed a task.
Mr Ochieng misplaced all of his 120,000 tilapia, virtually half of which have been prepared for harvest. Many different farmers suffered related losses.
The businessman, with three companions, owns 24 cages, close to Ugal Seashore on the Kenyan coast, which price them round $100,000 (£80,000). They spent one other $185,000 on child tilapia, feed and start.
“Cage farming carries large dangers, but it surely may also be very worthwhile,” says Mr Ochieng, who is set to proceed.
Because the identify suggests, cage aquaculture includes elevating fish in a mesh cage. It has develop into one of many quickest rising meals sectors in sub-Saharan Africa, as wild fish shares have declined and demand for fish has risen.
The variety of cages elevated from 9 in 2006 to greater than 20,000 in 2019, based on a current report. Study published in Nature Food.
In East Africa, between 2017 and 2021, the dimensions of the trade tripled, based on Gatsby Africa Report.
Yalelo Zambia is the most important tilapia producer in sub-Saharan Africa, producing a mixed 25,000 tonnes of the fish at its services situated on Lake Kariba in Zambia and on the Ugandan facet of Lake Victoria.
It’s an more and more high-tech firm, says the corporate’s CEO, Ulrike Daniel.
The chief govt informed the BBC: “Whereas we’re coping with a product we can’t see, as soon as it’s underwater we have now to rely closely on expertise to measure what is definitely occurring under the floor.” He provides that cage farming is extra data-rich than the poultry trade, for instance.
He says all this information may assist mitigate agricultural disasters like final 12 months’s.
“Backside water upwelling can occur immediately, however some indicators can predict its incidence,” says Daniel. “So, each day we measure dissolved oxygen, pH values and ammonia content material within the water.”
“As soon as we see the primary indicators of rising backside water, we are able to scale back the variety of fish within the cage to forestall mortality.”
Victory Farms, the most important producer of caged fish in Kenya, additionally collects a whole lot of information.
“We measure a number of depths and areas to evaluate underwater exercise and biology, assess algae within the lake as an indicator of backside water rise, and if dissolved oxygen ranges are low, we look at water currents in addition to the extent of algal buildup on the floor of the water,” says CEO Joseph Rahman. .
“With a seven-year historical past of knowledge, we are able to now sometimes predict whether or not there’s a excessive, medium or low danger of backside upwelling. If there’s a excessive danger, we alter stocking densities, scale back feeding, and sluggish or cease fish dealing with. “Each to scale back stress.”
Victory Farms has additionally developed expertise to scale back losses whereas transporting stay eggs to the hatchery.
They’ve developed a cell incubation system, which retains the eggs transferring in oxygenated water.
The expertise arose from a mission to construct hatchery ponds on plots of land within the neighboring neighborhood.
In return, members are paid for the harvested fish eggs, that are then transported to Al-Nasr Farms’ ponds.
Such improvements are past the attain of the rising variety of smallholder farmers who’ve ventured into cage farming.
“Though it is very important measure oxygen ranges in cages, most smallholders don’t do it as a result of they can’t afford the required gear, which prices greater than $1,000,” says Dave Okesh, president of the Kenya Cage Fish Farmers Affiliation.
One other drawback, based on Mr. Okesh, is the lack of understanding amongst many new farmers. “In consequence, some place their cages in water that’s too shallow, which might result in water air pollution, and may result in a excessive mortality charge if backside water rises to the floor.
“Some entrepreneurs additionally use low-quality feed that sinks, which negatively impacts the ecosystem and causes losses, as tilapia feed on floating pellets,” Mr. Okesh provides.
He believes extra exact feeding will result in more healthy fish and save farmers cash.
His firm AquaRech is at the moment engaged on a system to watch water temperature in cages.
That is a necessary piece of knowledge, he says, as a result of chilly temperatures make it troublesome for tilapia to digest what they eat.
Armed with this data, his system can advise farmers on precisely how a lot feed to make use of.
“We want this sort of innovation to professionalize the sector and make it extra productive and helpful for its members,” the Kenyan businessman provides.
Nonetheless, some are involved concerning the trade’s fast development. There may be concern concerning the great amount of uneaten feed and fish feces that accumulate below cages, and its impression on water high quality.
“The presence of those environmental points underscores the significance of inserting fish cages responsibly, in deep sufficient water with adequate water circulation,” says Chrisven Nyamuya, a analysis scientist on the Kenya Marine and Fisheries Analysis Institute.
Joe Rehman of Victory Farms says his firm and authorities officers often check water circumstances.
“To date, we have not had any issues with the capability to carry fish,” he says.
He factors out that overfishing has led to the depletion of untamed fish in Lake Victoria.
“If Victory Farms right this moment has 3,000 tons of biomass, we’re including to the nutrient load, however inside the pure carrying capability that existed earlier than human-driven overfishing depleted the lake.”