Standing at Gabba, a fish-landing site in Kampala, Uganda, a rising sun painted a swathe of yellow gold, dotted with dark silhouettes of boats and fishermen returning ashore after a night’s fishing expedition.

For generations men and women have fished the waters of the Lake Victoria and the River Nile for subsistence and recently for commercial export. The lake is the second largest freshwater lake in the world and boasts the world’s largest freshwater fishery. It is the source-feed of the world’s longest river, the Nile, supporting some estimated 30 million riparian populations.

The lake’s total fish production is estimated at one million tonnes, worth $650 million, according to a 2007 Lake Victoria Fisheries Organisation report.

In Uganda, the National Environment Management Authority estimates that “over two million people are directly or indirectly employed in the fishing industry… contributing 2.5 per cent of the country’s GDP”.

In 1992-2000, it contributed more than 93 per cent of the fish that landed annually in Kenya. In the last few decades, activities on the basin have increasingly come into conflict, with the result of making the Lake environmentally unstable. Experts warn that more than ever before, the lake basin is facing numerous threats.

An evening boat trip with a group of fishermen in Kisumu revealed the agonising reality of declining stocks on the lake. After four hours of trawling the lake, Joseph Otieno was a dejected man. The trawl had only harvested a handful daggas and Nile Perch fingerlings. Otieno has witnessed the constant decline in fish stock since his 2005 start as a fisherman. “In 2006 my brother took a loan to build a few boats. We were doing well, but nowadays it is very bad. I cannot make enough (money) to take my children to school.”

A walk along Kisumu’s Lwang’ni Beach on a Sunday afternoon reveals a car wash bonanza with vehicles parked right in the lake. Oil trucks, tuk tuks and boda bodas as well as small cars are pitting young boys in a stiff competition for the next vehicle. Jacob Otieno, 16, says that for “lack of job opportunities” this is what he has to do. “It is bad, I know, but what do people have?” He pauses, as he tears a detergent sachet between his teeth.

Caroline Adhiambo Omollo, the Safety, Health and Environment Manager at Kisumu Water and Sewerage Company (Kiwasco), explains that most soaps used in these illegal car washes contain phosphates and other chemicals that harm fish and water quality.

“The soap, together with the dirt and oil washed from the cars, flows into the storm drains which run directly into our lake; the phosphates from the soap can cause excess algae to grow.”

As towns in the basins have grown over the decades, so has the level of pollution that these settlements discharge into the local waterways. Local governments have been unable to adequately manage wastewater discharge.

UN Habitat reports that urbanisation is placing an enormous burden on most secondary towns in the lake region. “Urban areas are growing at rates of four to five per cent annually. These rates are projected to increase by 50 per cent by the year 2015.”

Omollo says that just a mere eight per cent of Kisumu city is connected to the company’s sewer grid, served by “a facility that was built in the 1950s for a smaller population. “Most residents use pit latrines or septic tanks, so if and when it rains, or when the septic tanks fill, it is very expensive for them to get exhausters to remove (the wastes). Most of the people will leave them to overflow. Another (issue) is the pit latrines: the water table of Kisumu is high, whatever soluble is in the pit latrines will end up in the lake.”

In Kendu Bay, one of the lake’s oldest fish landing sites and once an important docking port for ships and tourists, Peter Mwai, 39, and his younger brother are struggling to come ashore after a night’s fishing excursion. They had been cutting manually through a mat of hyacinth (Eichhornia crassipes) and lake weeds blocking the landing area of what used to be the Kendu Bay pier.

Across the pier over 30 fishing boats lay tightly pressed to the embankment, unable to go into the lake.

Mwai tells of a nightly tale “like no other” with the weed that tore his net. “We have spent a lot of strength, time… We were to reach here at seven, but now it is almost midday.” His wife has come to pick the little catch he says will fetch a meager Sh400.

At Kisumu’s only dumping site at Kachok lies a heap of solid waste from households and industries accumulated over the years, just less than three kilometres from the city centre.

Rhoda Obadha, Environment executive secretary at Kisumu County government, has come with her team to assess the dumpsite for an immediate course of action, in order to avoid any more “leachates”- soluble wastes that could be ending up in the lake. “This is the only dumpsite serving the whole municipality, up to about 300 tonnes of solid waste comes to Kachok every day.”

Environmental scientists such as Dr Fred Wanda, a Ugandan aquatic ecosystem health expert, explain that certain kind of waste seeping in the water is creating a fertile environment for the weeds and even for blue-green algae that are flourishing on the lake. It is the so-called eutrophication, an uncontrolled overgrowth of water vegetation.

In Uganda’s industrial town of Jinja, a leather factory is situated just less than 200 metres from the lake, “on the wetland”, Dr Wanda points out. “Industries aren’t supposed to be less than 200 metres near the lake, but no one seems to care.”

Some of the unchecked human activities in catchment areas are also harming the ecosystem, such as “clearing of marginal vegetation, especially wetlands whose function is to filter whatever water and dirt (that) comes from the land before it enters the lake.”

Off the beaches of Kisumu, Entebbe and Kampala, the water is visibly turbid as a result of “nutrient load from catchment farms and agrochemicals,” says Dr Wanda. “Traces of heavy metals such as lead and chromium are to be found on the lake from our sampling.”

Inside a laboratory at Kiwasco, George Odero, the water production manager, runs tests on raw lake water drawn from points off the bay of Kisumu. It is the rainy season and some samples off the shores of Kisumu registered an average 45 out of 100, after turbidity tests of four samples were carried out. “Not a bad indicator”, but it has been worse before.

A test of turbidity of the lake water at some points between Kenya and Uganda earlier revealed that “the distance at which a white disc is visible from the surface – a transparency index measuring algal abundance – has declined from five metres in the early 1930s to one metre or less for most of the year in the early 1990s,” just around the time water hyacinth was first spotted on the lake.

The lake, home to up to 200 species, many of them endemic to the area, is also under constant threat from introduced species, encroachment of breeding areas and over-fishing.

The introduction of Nile perch (Lates niloticus) as an exotic species some 30 years ago has also massively altered the food chain. A voracious predator growing to massive sizes, its arrival has lead to a recent increase in the fish export: an economic blessing for those with capital, but a curse to the subsistence fishermen employing primitive methods and inferior equipment such as fishing baskets.

A visit to Obunga slums in Kisumu reveals a smelly yard filled with fish bones and by-products from a nearby processing plant. Men and women, vultures and flies mill the yard for mgongo wazi, Swahili for “bare back”, in reference to the remains – fish head and bones sold there after filleting in the factory. “The Nile Perch has remained to be the main fish in the lake, and the pricing is very high… so what we’re remaining with is the by-product here,” says Richard Osiolo, a leader at the market.

A recent survey by the Lake Victoria Environmental Management Programme shows that pollutants have destroyed fish breeding grounds; coupled with illegal practices such as the use of seines and monofilament nets, some fish species could become extinct in 30 years. Poor governance and low compliance with regulations, weak enforcement, and corruption further aggravate the risks for over-exploitation.

At 6pm off Dunga Beach in Kisumu, a fisherman is setting up solar lamps on a boat as some other four men settled in position for the night. It is a fishing excursion like many others, but one thing stood out – the size of the fishing net – as a school of young tilapias, Nile perch and a myriad young cichlids are dancing their way into the fishermen’s plastic container. “They are illegally fishing out the young ones, including even the fish eggs,” a Kenya Marine and Fisheries Research Institute officer would lament two days later, on a dawn swoop that saw them confiscate more than 50 illegal fishing gears.

The health of the lake’s ecosystem remains on the balance, due to pollution and effects of climate change and other human activities, some experts fearing it could join the list of dying lakes. In urgent need of remedial actions, yet to be found, local fishermen are working harder and catching less, threatening food security. “They are in a predicament,” laments Dr Munyaho.