Lake Chad

Lake Chad sits at the southern lip of the Sahara, a shallow sheet of fresh water spread across the corner where Niger, Chad, Cameroon and Nigeria meet. Almost all of it arrives down two rivers — the Chari and the Logone — out of the wetter highlands far to the south, and almost all of it leaves again as vapour into the dry Sahelian air. Because the lakebed is nearly flat, a small shift in that balance moves the shoreline by tens of kilometres. In 1965 the lake covered about 25,0 mi²; by 1973 it had fallen to roughly 6,000, and by 2001 to under 2,500. The fishes that built one of West Africa's great inland fisheries have been living through that collapse, and through the human conflict it helped set off.

Geography & hydrology

Lake Chad is an endorheic lake — a closed basin with no outlet to the sea — lying at the heart of the Chad depression on the southern edge of the Sahara. FEOW places it as Ecoregion 520, classed among the world's xeric freshwaters and endorheic basins, bounded to the north by the Aïr and Tibesti massifs, to the east by the Ennedi and Jebel Marra, and to the west by the Jos Plateau. The lake straddles Niger, Chad, Cameroon and Nigeria, with the wider basin reaching into the Central African Republic and Sudan. What makes it unlike a deep rift lake is its shallowness and its flatness: the bed is so nearly level that a modest change in the water budget translates into an enormous change in surface area, both within a year and between years (FEOW Ecoregion 520; Carmouze, Durand & Lévêque 1983).

Nearly all the water comes from the south. The Chari, fed in turn by the Logone, drains the northern highlands of the Central African Republic and the Adamawa Plateau, and together these two rivers supply about 95% of the lake's inflow — the Chari alone delivering roughly half of the annual input in the flood months of October and November. The Yobe in the northwest and the seasonal El Beid riverbed contribute the small remainder. The Logone and Chari flood from September into December and the El Beid from November into January, so the lake breathes on an annual rhythm set hundreds of kilometres upstream. In big floods, water can spill from the Logone floodplains southward through the Mayo Kebbi system toward the Benue and the Niger, a connection that mattered for how the fauna assembled (FEOW Ecoregion 520; Olivry et al. 1996).

The lake's recent history is one of dramatic contraction. Carmouze and colleagues recorded about 25,0 mi² of open water in 1965, when the lake stood high; by 1973, after the Sahel droughts had set in, it had shrunk to around 6,0 mi², and a 2001 NASA assessment put it below 2,311 mi² as upstream abstraction compounded the drying. Hydrologists distinguish a 'Normal Chad' state — a single large lake — from a 'Lesser Chad' state in which the water retreats into the deeper southern pool and the northern basin goes dry. A submerged ridge called the Grand Barrier divides the lake into north and south basins; the better-fed south is usually the larger, and a southeastern zone of sandy islands forms a third distinct sector. During a Normal Chad period the lakescape is roughly 38% open water, 23% archipelago and 39% reed belt, a mosaic that the fishes track as it expands and shrinks (FEOW Ecoregion 520; Carmouze, Durand & Lévêque 1983; NASA 2001).

Water & habitat

For a lake at the desert's edge, Lake Chad is curiously fresh. Evaporation is fierce — driven by the Harmattan and the dry-season heat it can reach 2,12 in a year, often equalling or exceeding the inflow — and in a closed basin that loss would normally concentrate salts until the water turned brackish or saline. It does not, and the reason is a slow hydrochemical regulation that few shallow lakes manage. Fresh water entering from the Chari in the south is lighter than the saltier water to the north; it pushes the denser water toward the northern shore, where salts are lost partly to sedimentation and partly by seepage into a subterranean groundwater system. The result is a salinity gradient that rises from the Chari delta northward, but a lake that stays, on the whole, drinkable (Dejoux 1983; FEOW Ecoregion 520).

The water is shallow, warm and almost always turbid. Wind keeps the polymictic lake mixed top to bottom, stirring sediment off the bed, so transparency is low and tied to lake level: a mean Secchi depth around 3 ft in 1965 when the lake was high, dropping to about 0 ft in 1973 at the depth of the drought. Over a thousand species of algae have been described from these waters, and the phytoplankton they support, together with zooplankton blooms on the flooded margins, drive the lake's biological output. Submerged plants — hornwort, pondweed, eelgrass — grow where light reaches the bed, while the shoreline and the great reed belts are built from papyrus, Phragmites and Typha, with the more saline north favouring different stands than the fresher south (Carmouze & Lemoalle 1983; Iltis & Lemoalle 1983).

The habitat that matters most for fish is not the open lake but its floodplains. The Yaéré plain between the Chari and Logone in Cameroon floods across more than 5,0 mi², and estimates of the total inundated area south of the lake in the rainy season run as high as 90,0 mi². To the northwest, the Hadejia-Nguru wetlands draining toward the Yobe add another 6,0 mi² of seasonal water. As the rivers rise, fish move out of the lake and up onto these plains to feed and spawn in warm, plankton-rich, vegetated shallows, then retreat as the water falls. That flood pulse — connecting lake, river and floodplain on an annual cycle — is the organizing rhythm of the whole system, and it is exactly what the lake's contraction and the upstream dams and irrigation schemes have weakened (FEOW Ecoregion 520; Lowe-McConnell 1985; Bénech, Durand & Quensière 1983).

The cichlid fauna

Lake Chad belongs to the Nilo-Sudan bioregion — the broad, low-diversity but wide-ranging freshwater fauna that stretches across Sahelian and Sudanian Africa from the Senegal and Niger east to the Nile. That history shows in its fishes. During the Pleistocene the Chad basin was at times linked to the Niger, the Nile and probably the Congo, so its species are mostly shared with neighbouring systems rather than peculiar to the lake. The basin holds on the order of 135 fish species (a 2018 UN figure), but it has produced essentially no aquatic endemics — a striking absence for so large and historically vast a lake, which Lévêque and Dumont attribute to its recent isolation and the violent swings in water level that periodically wipe the slate clean (FEOW Ecoregion 520; Lévêque 1997; Dumont 1992).

The cichlids here are the workhorses of the Sudanian fauna, and several are the backbone of the fishery. Sarotherodon galilaeus, the mango or Galilee tilapia, is a maternal-to-biparental mouthbrooder of the open lake and floodplains and one of the most important food fishes across the whole Nilo-Sudan belt. Alongside it swim two Oreochromis tilapias — the Nile tilapia Oreochromis niloticus, the same species that anchors aquaculture worldwide, and the blue tilapia Oreochromis aureus, a hardier, more salt- and cold-tolerant mouthbrooder well suited to a fluctuating Sahelian lake. Coptodon dageti (long treated under Tilapia) is a smaller substrate-spawning tilapiine of the rivers and floodplain pools. These are not aquarium novelties so much as the protein that the basin's millions have eaten for generations.

The rest of the roster fills out the river-and-floodplain guilds. Three jewel cichlids of the genus Hemichromis bring the predators: the banded jewelfish Hemichromis fasciatus, a robust, fish-eating pair-bonder of vegetated margins found across Sudanian Africa; Hemichromis letourneuxi, a smaller jewel cichlid of the same wide northern range; and Hemichromis camerounensis, one of the five-spot jewel cichlids of West African creeks and lakes toward the Cameroon side of the basin. Rounding out the list is Tylochromis sudanensis, a sandy-bottom cichlid of the wider Nilo-Sudanic and upper-Niger drainages — a maternal mouthbrooder that grubs over soft substrates for invertebrates and plant matter, and a reminder that the Chad fauna grades continuously into that of the neighbouring Niger and Benue. The Gauthiot Falls on the Mayo Kebbi acted as a one-way filter on that exchange: species such as Citharidium ansorgii, Arius gigas, Synodontis ocellifer and Cromeria nilotica live in the Benue but never crossed into the Chad basin, which is why the lake's species list reads as a subset of the broader Sudanian pool rather than a fauna of its own making (FEOW Ecoregion 520; Lévêque 1997).

Conservation

The lake's contraction is the story everything else hangs on. Between the early 1960s and 1990 Lake Chad lost roughly 90% of its surface area — a sheet of water that had ranked among the largest lakes on the planet falling to a fraction of itself. The drivers were two, working together: a long decline in rainfall over the Chari-Logone headwaters in the Central African Republic, tied to the Sahel droughts and a drying climate, and a steady rise in water taken upstream for irrigation. The lake has stabilized at a 'Lesser Chad' state since around 1990 rather than vanishing outright, but the damage to the wider system — the floodplains, the flood pulse, the fish — was done in those three decades and has not reversed (World Bank 2023; FEOW Ecoregion 520).

The fishery tracked the water down. Landings climbed from about 20,000 tonnes in the early 1960s past 100,000 by 1971 and peaked near 220,000 tonnes in 1974, as the lake's retreat briefly concentrated fish and drew migrant fishers from across the region. Then it crashed: by the later 1970s catch had fallen back toward 20,000 tonnes and stayed there. Fishers on the Nigerian shore blame drought, the loss of breeding and feeding habitat as the lake and its floodplains shrank, and unregulated overfishing in which most of the catch became undersized juveniles taken between spawning and feeding grounds. The Lake Chad Basin Commission, set up to coordinate the four riparian states, has struggled to enforce shared rules while members keep drawing water for irrigation (MDPI, Fishes 2023; FAO 2012).

The ecological crisis and the human one are now inseparable. Some 30 million people across the basin depend on fishing, farming and herding, and as the lake shrank and those livelihoods failed, the region became fertile ground for Boko Haram and its offshoots. The insurgency has killed an estimated several hundred thousand people and displaced well over two million across the four countries, with armed groups taxing the very fish and cattle trade they helped collapse — at one point controlling much of the fish commerce around Baga on the Nigerian shore. Against that backdrop the region's governments have revived an old idea: Transaqua, a scheme first drafted by the Italian firm Bonifica in 1982 to divert water from the northern tributaries of the Congo basin through a canal roughly 2,249 mi long to the headwaters of the Chari, recharging the lake and generating power along the way. After the 2018 International Conference on Lake Chad in Abuja the Lake Chad Basin Commission backed a feasibility study, but the plan — variously costed around USD 50 billion (≈ €46 billion) — carries enormous engineering, financial and ecological risk, including moving water, sediment and species between two of Africa's great basins. For the lake's tilapias and jewelfishes, the near-term future depends less on grand canals than on whether enough flood reaches the floodplains each year, and whether the violence eases enough for any fishery management to function at all (Refugees International 2023; MDPI, Fishes 2023; water-alternatives.org 2020).

Where these cichlids live

Geography & hydrology

Water & habitat

The cichlid fauna

Conservation

Sources

Cichlids recorded here

Coptodon · 1

Hemichromis · 2

Oreochromis · 2

Rubricatochromis · 1

Sarotherodon · 1

Tylochromis · 1