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Pollution blamed for mass fish deaths in L. Victoria

The incessant contamination of Lake Victoria due to anthropogenic (human-related) activities is continuously denying the country revenues estimated to be over Sh40 billion annually.

Kenya Marine and Fisheries Research Institute (KMFRI) Fresh Water Research Director, Christopher Aura revealed that the loss is attributed to pollution, high population density, and increased fishing pressure.

Aura reiterated that over 60 per cent of fish production in Kenya and 1 per cent of captured fish globally come from Lake Victoria, with aquaculture and marine posting 14 per cent and 17 per cent respectively.

The world’s second-largest freshwater body has the potential for an estimated annual production of 300,000 metric tons.

“The lake currently produces 115,000 metric tonnes valued at Sh12 billion on a declining trend annually compared to the year 2002, when it produced 200,000 metric tonnes. In terms of individual fish size production, Omena (sardines) is now leading at over 50 per cent, Nile Perch at 22 per cent, and Tilapia at 03 per cent,” said Aura.

“But on export value, Nile Perch is 4 per cent and Omena is 3 per cent,” said Aura who was speaking during a virtual presentation to over 20 journalists drawn from the Media for Environment, Science, Health, and Agriculture (MESHA) Kisumu Chapter at the Dunga Beach boardwalk.

KMFRI’s reconstructed data for April 2022 indicates an increasing trend of fishers’ efforts into the lake, estimated at over 40,000, out of whom over 1,000 are women, 15,000 boats (crafts), over 5,000 cages, and illegal nets from 2014. This, however, has seen a decline in how much each fisherman brings home (Annual Catch Per Unit Effort).

On the fish kill phenomenon, Aura noted that it is due to eutrophication, which is the nutrient enrichment, contamination, or contamination which is coming from outside and inside the lake.

“Some of the cage farmers are not undertaking the Base Management Practices, like the wrong location of cages, the types of feeds used, feeding fish when they are stressed, overstocking, overcrowding, uncleaning, or unchanging of the nets. The low oxygen levels contribute to fish deaths mostly in cases of high temperatures (upwelling),” he explained.

Further, he explained that the change in lake water to various colours is due to algae formation which are microscopic plants found in water. “When you see green algae, which is called chlorophyta, and red algae, which is rodophyta, it is due to Algal Blooms as a result of increased nutrient enrichment,” Aura observed.

Aura further said that concentrations of toxins in the fish are below the threshold of lead and mercury, and if they go beyond that threshold, the fish become unsuitable for human consumption. But he assured that fish from Lake Victoria are safe for consumption.

“Our role is to conduct research, do capacity building, and advise the relevant bodies to take action, but we don’t go to the management aspect for implementation. We provide data and information on the population structure of fish and their maximum sustainable needs. Similarly, we do enforcement on fisheries and feedback,” Aura clarified.

This further entails the collection of data on oxygen, temperature, chemistry, living and non-living organisms, and monitoring from field surveys and satellites to compare with climate conditions within the lake.

Sustainable lake use resource looks at estimated annual production, e.g., capture, how much the lake can sustain in a utilisable manner (carrying capacity), and develops suitability scenarios on By-Order Aspect (living and non-living organisms within the lake, quality and quantity of natural resources, socio-economic and human-related activities around the lake).

This leads to climate risk factors like high temperatures, precipitation, rainfall, flooding, and prolonged dry seasons, which need best management practices when exerting pressure on the lake.

Kisumu Water and Sewerage Company (KIWASCO) Managing Director Tom Odongo informed that its two treatment plants next to the River Kisat and Nyalenda Estate are able to handle both domestic and industrial waste to the required standards.

“They are not sewer treatment plants but Water Resource Recovery Centres where we recover the wastewater, treat it, make it environmentally friendly, and release it back to the water bodies. On domestic waste,  all of them go to the sewer lines and end up for treatment,” Odongo said.

“Our treatment plants face challenges from phosphates and nitrates. The soap we use is a major source of phosphorus, and we need to campaign against its use on soaps,” he clarified.

Odongo further emphasised that most industries around Kisumu City have good pre-treatment waste facilities in line with the Environmental Management and Coordination Act (ENCA).

Kisumu County Fisheries Director Susan Adhiambo decried the increasing number of Beach Management Units (BMUs), wrong placement of the fish cages and insecurity after fish losses due to unemployment.

“There are 35 BMUs in the county, and we control illegal fishing and nets. We managed to stimulate the fisher folks after incurring massive losses of close to Sh1 billion from their invested cages. In Ogal Beach, we procured 2000 fish and 2000 bags of feed for 91 cages,’’ Adhiambo pointed out.

She further elaborated that they have helped the fish farmers stay afloat through the Aqua Reach Initiative and by partnering them with a local bank.

Magnum Environmental Network Chairman, Michael Nyaguti called for the constant testing of water coloration along industrial sources. A position affirmed by Kichinjio BMU Vice Chair Salim Abdallah, who called for a speedy solution to the incessant fish kills and low catch in his area.

Based on KMFRI’s calculated maximum lake sustainable needs, it is proposing a reduction in fishermen’s effort by 36–45 per cent, demarcation of fish breeding grounds (lake maternities), and surface area, which are mainly found in the river mouth where the river enters the lake and bays.

They are proposing blue economic use of water hyacinth on biogas and electricity productions and manual removal, and they have introduced spatial planning on cage culture, where they have mapped out cages in suitable areas and over 40 per cent in unsuitable areas, breeding grounds, and water hyacinth.

“We have divided the lake into offshore and inshore (cage culture). Offshore are cages placed deeper at a depth of 10 to 40 m, made with strong steel, and recommended to house 407 square kilometers (11 per cent) of the lake. The other suitability is 782 which is 21 per cent of the lake can be used for cages with lower dimensions. Inshore suitability are cages with low dimensions 2m by 2m, 3m by 3m recommended carrying capacity area is 291,” Aura said.

Control of river, sewage, or industrial discharges by ensuring they must not discharge the wastes into the lake untreated by using pre-treatment points or tanks within their locality and checking on the Biological Oxygen Demand.

KMFRI has advised the county government on water supply and sanitation, better habits, and cleaner riparian cities, to reduce lake pollution. In this way, Aura observed, lake sanitation will promote tourism culture and sports, support fisheries tourism, and build on conference tourism.

Lake Victoria Tourism Association Chairman Robinson Ayah insisted on a multi-sectoral approach to promote the lake’s attraction sites, gastronomy (cuisine tourism), and conservation of the aqua system.

By Rolex Omondi

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