Omena vendors at Litare beach in Rusinga Island, Homa Bay county. [Collins Oduor, Standard]
Cage fish farming is slowly taking over Lake Victoria. Already, there are more than 5,000 cages in the lake in Siaya, Migori, Kisumu, Busia, and Homa Bay counties.
The technology involves the growing of fish in existing water resources while enclosed in a net cage. Like all technologies, it has its downside.
Reports show that the cages are choking fish species like omena (silver cyprinid, dagaa).
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According to marine experts, competition between wild-capture fishing and cage aquaculture has caught omena in the middle. Omena serves as human food and as a component in making animal feed.
Dr Christopher Aura, Director of Fresh Water Systems at Kenya Marine and Fisheries Research Institute (Kemfri), says the placement of cages in sensitive areas has disrupted the breeding of dagaa.
And because of that, dagaa numbers have dropped significantly pushing up prices.
Alice Aluoch, a resident of Bondo town, says switched to vegetables after tilapia and omena became expensive.
Cage fish farming in Luanda Kotieno beach in Rarieda sub-county. [Isaiah Gwengi, Standard]
“The price of omena has gone up because of its demand in making animal feeds,” says Aluoch. She says a 2kg tin which was retailing at Sh100 three years ago now costs between Sh180 and Sh200.
While cage fish farming is popular, Dr Aura adds that it presents significant environmental challenges.
“In cage aquaculture systems, high densities of fish in cages means high production of waste in the form of unused feed, chemicals, pathogens, faeces and dissolved metabolic waste from the fish,” explains Aura.
He further explains that the escapement of non-native fish from cage culture poses an additional ecological risk, as tilapia are notorious for escapement.
“Additionally, the spread of diseases among cages too tightly spaced together, or from caged fish to wild fish, poses a serious threat to Lake Victoria,” he tells Smart Harvest.
Divisibility and affordability
According to nutritionists, omena has the advantage of divisibility and affordability. It is popular because of its low cost, nutritive value and unit quantity that can be purchased at a given time.
Virginia Wanjiku, a nutritionist at Kenyatta National Hospital says dagaa is high in protein and calcium, making it a great food source for poor communities.
Martha Akoth, a regular consumer of omena, says ten years ago, she would buy a 500 grammes tin of the fish at Sh25. The same now retails at between Sh50 and Sh70, depending on the season.
“This commodity was a saviour during dry spells when agricultural production is low, or has failed,” says Akoth.
While fish farmers appreciate the cage culture, critics accuse the county governments of promoting farmed fishing over the other.
“Not everyone can afford cage fish farming. The government should find a way of promoting other methods of fishing,” says Martin Omondi, a fisherman in Bondo sub-county.
Siaya County Executive for Agriculture, Livestock and Fisheries Dr Elizabeth Odhiambo says fish cage farming was embraced to expand wealth creation avenues as well as create jobs.
According to the Lake Victoria hydro-acoustic survey conducted between October and November 2020, omena production on Lake Victoria showed a steady rise in volume from 418,590 to 674,616 tonnes between 2010 and 2015.
The report established that Uganda and Tanzania were exporters of omena while Kenya was an importer.
Another survey carried out by Uganda’s National Fisheries Resources Research Institute (NaFIRRI), Kenya’s Marine and Fisheries Research Institute (KMFRI), and the Tanzania Fisheries Research Institute revealed that stocks of silverfish have continued to decline in the past four years.
The survey estimates silverfish numbers to stand at 0.7 million tonnes, down from 1.39 million tonnes in 2015, representing a 50 per cent decline in two years.
Tanzania recorded the biggest decline at 62 per cent (from 0.86 million tonnes to 0.32 million tonnes) followed by Uganda 34 per cent (from 0.43 million tonnes to 0.28 million tonnes).
