Despite local measures to combat pollution and overfishing, stocks of the once bountiful Nile perch have fallen by at least three-quarters.
On the main roundabout in Mwanza, Tanzania’s second most populous city, there stands a large grey statue. The monument doesn’t commemorate a great post-independence leader, nor a European explorer who – after years of searching for the source of the Nile – alighted on the great lake on which Mwanza sits, but a fish.
With good reason. Fishing is Mwanza’s lifeblood and, for the past 40 years, the Nile perch, a strong, fast-swimming predator that can grow to the size of a man, has been at the heart of the industry. Around Lake Victoria, millions of Tanzanians, Ugandans and Kenyans depend on the fish for their survival. In the 1980s and 1990s, there was a Nile perch boom, with fishermen from all over Africa descending on the continent’s largest lake to join the gold rush. They sold their catch to processing factories around the lakeshore, and the factories exported it to customers in Europe, the Middle East and Asia.
In the mid-1990s, fishermen in the Tanzanian half of Lake Victoria alone were catching two hundred thousand tons of Nile perch each year – 30 times the total annual tonnage of fish caught in North America’s Great Lakes. So important was the perch to livelihoods in what had until then been one of the poorest parts of East Africa that it came to be known as “the saviour fish”.
These days, however, the mood is less buoyant. In Mwanza’s Mwaloni market, the waterside hub at which fishing boats from the islands that dot the lake offload their catch, a trader is counting off sacks of dried Nile perch as young men load them onto a truck bound for Congo. He tells me that the price of the fish has tripled in the past five years. “Supply is down,” he says, “but demand is still high”. Another trader stands beside a tray of smoked lungfish, their blackened eel-like bodies curled into loops for display. The fish are not from Lake Victoria, the vendor says, but from the Tabora region, over 300km away in central Tanzania. “In the past there were lungfish in the lake,” he explains, “but now there are very few”.
It is not only Nile perch and lungfish whose numbers have reduced. Hundreds of Lake Victoria’s fish species have gone extinct in the past three decades as a perfect storm of overfishing, deforestation, and pollution has laid waste to what was once one of the most biodiverse environments on Earth. The price of Nile tilapia, another popular fish for eating, has quintupled in five years despite increased competition from fish farms in Asia. “You have to work hard to catch just one tilapia nowadays,” a fisherman on Ukerewe, the lake’s largest island, tells me. “They are very difficult to find.”
Nile perch was introduced to Lake Victoria in the 1950s by East Africa’s British colonisers, who wanted to turn the lake’s native species into something of economic value. The perch, the theory went, would be more likely to generate cash for the colonial economy than the smaller, unpalatable fish on which it would feed. Ecologists’ warnings about the negative effects an alien species might have on a complex tropical ecosystem went unheeded, but even the scientists didn’t foresee the upheaval the perch would cause.
For the intruder didn’t just eat the native fish and outcompete them for food. The opportunity to make money by catching, processing, and exporting it also triggered a boom in the human population around the lake. Trees were felled to build houses, supply charcoal for cooking, clear the land for farming, and smoke the oily perch. New industries descended on the region, with breweries, tanneries and paper factories joining the fish processing factories and farms. Deforestation loosened the soil and made it easier for the pollution spewed by all these new arrivals to infiltrate the lake. Sewage, pesticides, fertilisers, and industrial chemicals starved its waters of oxygen, causing mass die-offs of fish and hastening the extinction of native species.
Overfishing has also taken a heavy toll. At the peak of the boom, 2,000 new fishing boats were launched onto the lake every year, using ever more efficient technologies. Despite measures adopted by governments of the lakeshore countries such as banning trawlers and clamping down on other illegal fishing methods, Nile perch stocks have fallen by at least three-quarters. The average weight of a caught perch has shrunk from 50kg in the 1980s to less than 10kg today. Although the fish factories persuaded the Tanzanian government to slash the legal minimum size at which a perch can be harvested, many of the specimens on sale in the market in Mwanza are smaller even than the new threshold. A number of the factories have closed or are operating at reduced capacity.
The 25 million people who rely on the lake’s munificence are finding it difficult to make ends meet. Unemployment and underemployment are rife, and many are leaving the lake region to seek work in Dar es Salaam, Nairobi or overseas. In a market on Ukerewe, the number of stalls selling potions for use in witchcraft has mushroomed as islanders turn to the occult for solutions to their plight. Other market traders are struggling. “We depend here on fishing,” a woman who has a sundry goods stall tells me. “When there are no fish, there is no money in circulation. And when there is no money, we have no business.”
Mark Weston is the author of The Saviour Fish: Life and Death on Africa’s Greatest Lake (Earth Books, April 2022).