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Losing a Lake

Lake Victoria is in danger of becoming the world's largest pool of dead water. Already half its native fish are extinct, and the 30 million people who eke out a living from its troubled waters are facing calamity.

By Yvonne Baskin
Mar 1, 1994 6:00 AMNov 12, 2019 4:50 AM


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The sun is halfway up over Kusa Bay, where the brown waters of Lake Victoria lap at the parched Kenyan savanna. A Luo fisherman poles his plank canoe into an opening hacked through the reedy, papyrus-clogged shallows. Six of his comrades grab the bowline and begin a rhythmic chant as they drag the vessel to shore. "Harambee, harambee, harambee, ayaaah," they sing out as they lean into the task, "together, together, together." The women on the bank laugh, awaiting the catch, their baskets and bright plastic tubs bobbing on their heads.

Yet a casual glance into the dozen canoes beached on the mud reveals hardly any fish at all. Moving among them, Peter Ochumba inspects the meager catch stacked on the floor of each boat. Two dozen ten-inch Nile tilapia. A few Nile perch that aren't much larger. A bucket of haplochromine cichlids--little fish, two to four inches long, that used to dominate these waters. One labeo, or ningu as it's known locally, a small carplike delicacy whose abundance formerly made this village prosperous.

Ochumba is a limnologist--a freshwater specialist--with the Kenya Marine Fisheries Research Institute (KMFRI). He understands better than most why his fellow Luo and tens of thousands of other fishermen around the lake have so little to show for their night's labors. From the bottom of a boat he picks up the most publicized suspect, a Nile perch. Had it not been caught as a foot-long juvenile, this fish might have grown to a six-foot, 200-pound giant, mostly by gobbling up the smaller fish that are these fishermen's livelihood.

No other freshwater fish has received as much bad press as the Nile perch--Lates niloticus in the language of taxonomy, "voracious alien predator" or "fish of doom" in the language of the British tabloids. Since its introduction by British colonials in the mid-1950s, the perch has exploded in number, apparently wiping out fully half the 400 species of haplochromine once native to the lake. These little fish not only form part of the food chain for millions of Africans around the lake, they are also one of the natural wonders of the world--a case of evolution in such frenzied overdrive that they've appeared on the prestigious cover of Nature. Western scientists have long flocked to Victoria to study the haplochromines' legendary diversity. One of them, Les Kaufman, chief scientist for the New England Aquarium's Edgerton Research Laboratory, has termed the haplochromine loss "the greatest vertebrate mass extinction in recorded history."

But there's mounting evidence that the Nile perch may only have rendered the coup de grace. The whole lake is dying, and humans more than perch are the culprits.

No rock celebrity has yet hosted a concert for a tropical lake. In the African tropics, however, lakes are as imperiled as forests, and the one in deepest peril is Lake Victoria. At its greatest extent this huge body of inland water--the largest in Africa, surpassed in the world only by Lake Superior--is 255 miles long by 155 miles wide. Its murky waters stretch all the way from the vast savannas of Tanzania's Serengeti in the south, to Kenya's Masai Mara in the east, to the lush equatorial jungles of Uganda in the north and west.

But Lake Victoria is not only murky, it's disastrously algae- choked and oxygen-depleted. The lake has probably been deteriorating throughout the century, but the problem went largely unrecognized amid the wrenching social upheavals of East Africa. Now, at the eleventh hour, Victoria has become an international cause célèbre. At research stations in the three countries around the lake--Mwanza in Tanzania, Kisumu in Kenya, Jinja in Uganda--the acronyms of the developed world abound. The KMFRI Land Rover that Ochumba uses, for example, was put back in service after years in disrepair by the Lake Victoria Research Team, which is funded by U.S. agencies such as the National Science Foundation (NSF) and the Environmental Protection Agency (EPA) as well as by private groups such as the Pew Charitable Trust. The goal of this international effort is to find out what went wrong with the lake, try to save at least some of its legendary biodiversity, and provide a secure source of protein and work for the 30 million people on its shores.

"This is what everybody's talking about when they say biodiversity is important," says Kaufman, who heads the research team. "Biodiversity affects people. In this case, an ecosystem is losing its ability to feed those living around it." The story of Lake Victoria, he notes, "has become a kind of ballad, warning of the dangers of meddling with nature."

But well-meaning attempts to meddle with other nations' problems can be touchy. Many powerful people in local government and business, for example, consider the Nile perch a savior, not a spoiler. An ecological disaster, yes, but for the moment, ironically, the lake is producing record numbers of perch that are bringing in sorely needed export dollars.

On the open lake, where local fishermen cannot pole their canoes, large boats are hauling out Nile perch by the uncounted and unregulated ton. The fish are then sold to dozens of processing plants built along the Kenyan and Ugandan shores by investors from Asia, Europe, and Australia. Within hours the thick white fillets have been cut from the fish, flash frozen, boxed, and loaded on trucks headed for the port of Mombasa, Kenya, where they are shipped to the tables of Europe and the Middle East.

Kaufman wryly recalls a 1992 visit to KMFRI's headquarters in Kisumu, Kenya's largest lakeshore city, that was interrupted by a government official who was brandishing a foreign newspaper. "He was angry," says Kaufman, "because scientists were quoted as saying the lake was dying. I could just see my research permit going into his fireplace. But we had a long talk, and we came to a resolution: the lake is not dying; there just happens to be less and less oxygen in the lake, and lack of oxygen is incompatible with life." That same summer Kaufman was approached by "a guy from Iceland who wanted to know how good his profits would be" if he opened yet another perch-processing plant on the shore.

The business boom is taking a toll on humans as well as fish. Traditional ways of life along the shore are crumbling. As Ochumba drives from Kusa Bay back to Kisumu, he stops on Kisumu's outskirts to talk with women frying perch scraps over charcoal fires. These women from nearby fishing communities once bought native tilapia, labeo, and haplochromines to dry in the sun and sell. As these species dwindled, the women migrated to squatter camps near the perch-processing plants, where they buy the carcasses after filleting. The fleshy heads and tails are fried and sold from roadside pole stands; they are the only fish most local people can afford.

Back at KMFRI, James Ogari, a biologist and deputy director for inland waters, includes himself among the locals: "It's even difficult for me to afford fish at my meals the way I did four or five years ago," he says. "The main role of fisheries should be to provide protein for the community first, then to provide foreign exchange. But the trend now is the reverse. I don't know what the poor man is going to eat."

In fact, if the lake continues to deteriorate and the overfished perch population crashes, it's not clear what anyone who depends on Victoria will eat.

The one sentiment binding all the lake's constituencies--local fishermen, ecologists, commercial boat owners, and processors--is uncertainty over Victoria's future. To reduce that uncertainty, scientists must first piece together what went wrong in the past. Some of the keys to this complex story are to be found about 100 miles from Kisumu in Jinja, Uganda. For most of this century, Jinja was not only the headquarters for managing the entire lake's fish but also its center for research.

From the air, as you fly along the equator from Kenya to Uganda, Lake Victoria still looks much as it must have in 1858, when the British explorer John Speke stumbled onto its southern shore and proclaimed he'd discovered the fabled source of the Nile. The fractal fingers of Victoria's shoreline shelter hundreds of bays and inlets like Kusa, and islands dot the open waters. The lake is shallow--270 feet at its deepest. Rivers flowing in and out are so languid that Victoria takes a century to flush and replace her waters.

In 1875 another British adventurer, Henry Stanley, circumnavigated Lake Victoria to confirm Speke's claim and spent two weeks spinning tales of God and England to curry favor with Mtesa, king of Buganda and ruler of the northern lake region. Then Stanley sent word back to England, calling for missionaries. They came with soldiers and traders. Within 20 years England had taken charge of what became Uganda and Kenya (Germany got Tanzania), and by 1902 the colonial government had pushed through a railroad from Mombasa to the lake.

Europeans soon denuded vast tracts of forest in Lake Victoria's watershed to plant tea, coffee, sugar, tobacco, and cotton. The human population exploded, and people increasingly turned to the lake not for subsistence but to satisfy a market for fish--especially the tasty tilapia called ngege--in the growing urban centers.

In Uganda's heyday as the "pearl of Africa," Entebbe Airport on the northwestern edge of the lake served as a symbol of progress. Today, Ungaro and Chanel perfume posters hang incongruously on the stained, bullet-pocked walls of its terminal. Although the airport is being refurbished, there are still signs of the debris left by the 1976 Israeli commando raid to free hostages from a plane held by Idi Amin. Amin, the dictator who brutalized this nation from 1971 to 1979, looms large in Victoria's tale, for it was on his watch, while researchers were forbidden to study the lake, that it changed most dramatically.

Two hours east along the shoreline road from Entebbe lies Jinja, where the Nile begins its 4,000-mile journey to the Mediterranean. Jinja was a prosperous Indian trading town until 1972, when Amin ordered 80,000 Asians out of Uganda and confiscated their big stucco homes and rows of tin-roofed commercial buildings. One aging stucco complex by the lake is home to Uganda's Fisheries Research Institute. It is here that biologists have traditionally come to study Victoria's great haplochromine explosion: as many as 400 species, all apparently evolved from a couple of ancestors in the past 14,000 years or so. Each species has a subtly different jaw anatomy adapted for its feeding strategy. Some haplochromines eat crabs or prawns, some prefer insects, some consume fish eggs or babies (those known as "snout-engulfing paedophages" literally suck babies from the jaws of female haplochromines who brood their young in their mouths). Others graze on algae or detritus, or crush snails and other shell mollusks. Ichthyologists and evolutionary biologists have painstakingly cataloged the species, giving them colorful nicknames like "flameback," "pink flush," "Kisumu frogmouth," and "Mbita red anal."

But the main job at Jinja has traditionally been managing the fishery. Fishing pressure on the lake began to intensify in 1905 when the British introduced flax gill nets, which soon replaced the local villagers' papyrus nets and fish traps. With overfishing, catch sizes began to drop; fishermen turned to nets with ever-smaller mesh sizes and thus decimated both the breeding adults and young of many native species. By the 1950s the ngege was commercially extinct and the labeo was not far behind. To compensate, British officials decided to stock the lake with new fish. The first nonnative species that prospered was the Nile tilapia, Oreochromis niloticus, which feeds on the minute forms of plant and animal life called plankton. (This tilapia has been introduced in rivers and lakes throughout the world, including North America, where it is often, confusingly, called a Nile perch.)

Despite such changes, the haplochromines appeared to be thriving in the 1950s. In fact, they appeared so robust that some colonial administrators favored introducing a big predator like the Nile perch to eat what they considered bony little "trash" fish and "convert the haplochromine biomass" into something more suitable for the restaurant table. Ecologists, fearing the worst for local species, strongly opposed the predator. But in 1954 illicit Nile perch began appearing in commercial catches anyway. Since the dirty deed was done, officials actively stocked the lake with perch in the early 1960s. (Ogari suspects perch were first slipped into the lake by colonial sportsmen, just as homesick British anglers put trout into highland streams throughout eastern and southern Africa.) Still, for the next decade or so, the alien perch population remained small. A United Nations-sponsored survey completed in 1971 found that haplochromines still made up the traditional 80 percent of the lake's fish biomass.

Then came what Pereti Basasibwaki, a Fisheries Research Institute biologist, calls the dark period, the years between 1974 and 1979 when Amin cut off access to the lake. For a time Basasibwaki tried to run the fishery from Jinja, its time-honored headquarters. He continued to send staff on routine assignments to Kisumu and Mwanza, substations in Kenya and Tanzania that Jinja had overseen since colonial days. Accused of "helping people flee the country," Basasibwaki was imprisoned by Amin's troops, and work at the fishery wound down.

It wasn't until 1979 that the Kenyan government took over the idle Kisumu facility and work resumed under KMFRI's auspices. Pilot surveys suggested the lake's fish biomass was unchanged: it still appeared to consist of 80 percent haplochromines and less than 2 percent Nile perch. But in 1980 an abrupt change showed up in Kenyan waters, and within two years it appeared in Ugandan and Tanzanian waters too. Nile perch suddenly jumped to 80 percent of the biomass, and haplochromines dropped to 1 percent. Ngege, already rare, virtually disappeared. Clearly something had been building during the unmonitored 1970s to cause such a massive explosion of perch. As for the haplochromines, the leading theory is that they simply provided the predator's fodder.

At first, official concern focused on problems the perch created on shore. Fishermen needed bigger gear to deal with a fish that could grow to a hefty six feet. Villagers didn't know how to fillet or cook the big oily thing and couldn't dry it in the sun. There were no markets for the monster, prices were low, and most perch were left on the beach to rot. With UN funds, a KMFRI team toured lakeside villages and Nairobi hotels, demonstrating how to fillet, freeze, smoke, and cook the fish. Foreign-aid groups and investors moved in with processing plants and refrigerated trucks. With the benefit of hindsight, it's tempting to say the effort was too successful. Today few people who live by the lake can match the price hotels and foreign customers are willing to pay for perch--so much so that the specter of protein malnutrition is being raised in a region exporting 200,000 tons of fish a year. No part of the perch goes to waste. A poster at KMFRI offices shows shoes, belts, and purses made by a Mombasa company from tanned perch hide. In Nairobi's newspapers front-page ads offer up to six dollars a pound for dried perch swim bladders, which are sent to England for filtering beer and wine and to the Orient for making soup stock.

In the early 1980s, however, few government officials in Africa viewed the shift in Lake Victoria's fish fauna as a disaster. After all, U.S. fishery managers have introduced exotic species into most waters in North America, largely to please sport fishermen. Threats to native fish are a recent concern, and fish don't rate the emotional response accorded to pandas and elephants. "Just try to quit stocking Pacific salmon in Lake Ontario to restore its native pike, cisco, and walleye," comments Bob Hecky, a Lake Victoria Research Team member and a limnologist at the Freshwater Institute of the Canadian Department of Fisheries and Oceans.

But the perch's ascendance turned out to be a visible symptom of a much graver problem. In the late 1980s Ochumba, Hecky, and other colleagues studying the lake's environment found changes so disturbing that even government ministers were alarmed. The bottom waters of the lake appeared to be a dead zone, devoid of oxygen and fish life. On the other hand, the lake was chock-full of algae--five to ten times more than in the early 1960s. That suggested massive eutrophication, an oxygen-depleted condition caused by high levels of nutrients that encourage the rapid growth of plankton, especially plant plankton such as algae. The decay of plankton in turn depletes water of oxygen.

In December 1990, hoping to get to the bottom of things, Hecky lowered a core sampler over the side of a boat and gently drew up plugs of sediment from the soft ooze on the lake bed. One six-inch core, drawn up from water 180 feet deep, contained 200 years of continuous water history in the form of dead algal cells, hard silica shells of diatoms (another type of plant plankton), and plant nutrients such as nitrogen and phosphorus.

From such data, Hecky and his colleagues have begun to piece together the complex web of interactions between lake, people, fish, and climate that led to ecological upheaval. "Our analysis shows the lake was rather stable through precolonial days," Hecky says. "But about 1900, long before the perch, we begin to see things change." As European settlers arrived--first razing land for plantations, later establishing industries in the area--sewage and runoffs of fertilizers, pesticides, and industrial wastes began to pour into the lake. Hecky's cores show that by the 1920s increased levels of nitrogen and phosphorus from some of these man-made sources had already caused a change in Victoria's plankton composition in favor of blue-green algae--familiar to most of us as pond scum. By the 1960s the situation had deteriorated dramatically. The big losers in the plankton community turned out to be diatoms, because there was no corresponding increase in silica, which diatoms require for their shells.

This might explain why ngege, the lake's native tilapia, were the first fish casualty. Ngege were diatom eaters, and diatoms were already almost gone by the 1950s. Overfished and deprived of their favorite food, ngege apparently languished until, in 1980 or so, Nile perch completely extinguished them in the lake. The alien Nile tilapia, introduced to replace the ngege, eats a much more varied diet so it didn't miss the diatoms. It also seems more adept at coexisting with the Nile perch.

By the 1970s the heavy nutrient load in the lake was fueling massive algal blooms. As the algae died and fell to the bottom, they were decomposed by bacteria, which used up increasing amounts of oxygen to do their work, leaving the deeper waters too poor in oxygen for fish. Consequently fish were jammed into the shallow inshore waters and bays where they are more likely to fall prey to Nile perch or human fishermen. Even the shallows, however, may not provide an oxygen-rich environment for much longer. In 1990 another alien, the South American water hyacinth, apparently entered the lake from one of its feeder rivers. This decorative but destructive plant seems to be spreading rapidly, forming dense mats and adding to the rotting biomass that lowers oxygen levels in the waters below.

What Kaufman finds remarkable is that Lake Victoria's ecosystem didn't collapse earlier. He believes the credit should go to its little haplochromine cichlids. The vast majority feed on algae or rotting detritus in the deep lake. In gobbling up the haplochromines, the Nile perch appears to have annihilated the lake's self-cleaning system. Now the perch has been forced to turn to new food sources, primarily scooping up mouthfuls of tiny native shrimp or cannibalizing its young, which further jeopardizes its own survival.

Just to complicate the situation, the lake may be a victim of regional, perhaps even global, warming. Normally, during the rainy season Victoria tends to stratify, with warm water on top and denser, cooler water on the bottom. Mixing occurs later in the year when seasonal winds churn the water and send oxygen down to the lake's bottom. In recent years, though, higher-than-normal surface temperatures have meant that the mixing is much harder to accomplish. Victoria's stratification hasn't been helped by the massive blooms of algae that absorb sunlight for photosynthesis and give off energy as heat; they, too, may keep the surface waters warm and buoyant. During the 1980s, when oxygen-depleted bottom waters finally did surface, they often caused huge fish kills.

What can African governments do to slow down Victoria's disastrous degradation? Should they order livestock operations and sugar refineries to clean up effluents? Should they enforce strict quotas on fish catches to preserve both native and commercial species? Should they tax fish exports to foreign countries to fund remedial efforts? Do they stop spraying pesticides when locusts swarm over crops in the lake basin? Do they tell people in the highlands who have never set eyes on the lake to stop fertilizing their tiny plots of maize? Should they reintroduce algae- grazing fish to replace the lost haplochromines?

All those things might help, but few are feasible in nations with widespread poverty and some of the fastest-growing populations in the world. "Governments are going to need an extraordinarily strong case before they'll make any of these changes," Hecky says. He and others see Lake Victoria as a test case, not just for Africa but for tropical lakes everywhere. Victoria reached crisis before the others, he says, because "it's the shallowest of the great lakes and it has the highest density of humans in its watershed, so it has less capacity to dilute all these problems."

Already researchers like Kaufman, Ochumba, and Basasibwaki are working on projects to help both people and native fish, regardless of what happens to the lake itself. Breeding stocks of 40 haplochromine species-- selected to represent most of the different feeding strategies that evolved in the lake--as well as the native ngege are safe in exile at 30 aquariums in the United States and Europe under a World Conservation Union program led by Kaufman. Both Kenya and Uganda are expanding their fish-farming efforts, collecting founder stocks of haplochromines and other native fishes and considering plans to introduce them into smaller lakes and ponds in the region. If the decline of Lake Victoria itself can be halted, isolated bays and inlets may one day be cordoned off with nets as "fish parks" or as farms for valuable commercial species.

These efforts--admittedly more akin to salvage than conservation or restoration--have drawn plenty of critics. Kaufman notes that some Western colleagues and organizations think Lake Victoria is too far gone and should be written off. Conservationists are right to focus their limited resources on preserving untouched wild places, he believes, but he pleads the case for "salvaging orphaned pieces of ecosystems that can never again be precisely as they were."

And what if the world does write off Lake Victoria? What would it mean for the lake to die? "Nature doesn't die dead," Kaufman responds. "The best examples of real dead lakes are the hundreds of acidified lakes in the Adirondacks. Microorganisms survive, but no fish. They're just pretty boring."

But boring doesn't begin to describe the situation that would result if Lake Victoria no longer provided food or employment for the people who live around it. For the fishermen of Kusa Bay, the women selling perch scraps in Kisumu, and all the rest of the 30 million people whose fate is tied to the lake, there is no place to turn. Even in Africa, where epic sagas of famine and upheaval are all too common, the death of Lake Victoria would bring unparalleled suffering.

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