Northern Upper Guinea

Northern Upper Guinea is the wet northwestern shoulder of West Africa's cichlid country: a band of short, steep Atlantic rivers that spill off the Fouta Djallon highlands of Guinea and run down through Guinea-Bissau, Sierra Leone, and a corner of Liberia to the sea. The Fouta Djallon is the 'water tower of West Africa,' the sandstone massif where the Niger, Senegal, and Gambia all rise, and the rivers that stay inside this ecoregion — the Konkouré, Kolenté, Kogon, Coliba — tumble off it on torrential, rock-bottomed courses before fanning into mangrove estuaries. The fish here are an old, distinctive Upper Guinean fauna, heavy on tilapiines, jewelfish, and dwarf cichlids, and now squeezed between bauxite mines and a string of new dams.

Geography & hydrology

The Northern Upper Guinea ecoregion (FEOW Ecoregion 511) covers the western flank of the Guinean range, running from the foothills of the Fouta Djallon in Guinea southeast to the southern border of Sierra Leone, with slivers reaching into Guinea-Bissau and Liberia. It is defined not by one big basin but by a row of medium and small rivers that drain straight to the Atlantic. The largest are the Coliba (about 17,497 mi² and 253 mi long), the Konkouré (around 17,0 mi² over 86 mi), the Kogon (7,179 mi²), the Kolenté or Great Scarcies (5,106 mi²), the Kaba, the Tinguilinta, the Fatala, and the Mongo. Together with Southern Upper Guinea, the Fouta Djallon, and Mount Nimba, the ecoregion belongs to the Upper Guinean bioregion, a province with its own fish fauna distinct from the Niger and the Congo to the east (FEOW Ecoregion 511; FAO inland fishery source book, Guinea).

What ties these rivers together is where they start. The Fouta Djallon is a sandstone-and-granite massif rising to nearly 1,1640 ft, drenched by the West African monsoon and drained on every side by rivers that supply much of the dry-season flow across the western Sahel. It is the headwater of the Niger, the Senegal, and the Gambia, which leave the region eastward and northward — but the rivers that define Ecoregion 511 are the ones that take the short, steep road west to the ocean. The Konkouré, for instance, begins around 2953 ft in the highlands and falls roughly 227 mi to the coast; the Kolenté drops about 149 mi to its estuary in Sierra Leone. Because the gradient is so abrupt and the bedrock so hard, almost all of these coastal rivers have what the FEOW description bluntly calls a torrential flow regime, with rocky beds, rapids, and waterfalls in their upper and middle reaches (FEOW Ecoregion 511; Britannica, Konkouré).

The regime is strongly seasonal. The coast of Guinea is one of the wettest stretches in West Africa, and the rivers swell through a single rainy season — the Kolenté, for example, floods from roughly July to October — before shrinking back hard in the dry months. Near the sea the picture changes completely: the fast highland rivers slacken, spread into floodplains, and end in broad estuaries fringed by mangroves and swamp forest, where Atlantic tides push salt and brackish water far inland. A single river therefore runs the full gradient in a short distance, from cool, oxygen-rich cascades over Fouta Djallon rock to warm tidal channels among the mangroves — and the fish sort themselves out along that gradient.

Water & habitat

The upper and middle courses are highland streams in the literal sense: shallow, fast, broken into riffles and pools over boulders, cobbles, and bedrock, shaded in places by gallery forest and cool by West African standards. A survey of the Konkouré recorded water temperatures of about 66–77 °F in the upper reaches against 77–84 °F lower down, with pH around 5.9–6.2 — soft, faintly acidic water draining the impermeable sandstone and granite of the Fouta Djallon, which stores little and sheds quickly. The Kolenté runs closer to neutral, around pH 7.1 with conductivity near 60 µS/cm. None of this is mineral-rich water; the highlands hold almost no soluble rock, so dissolved loads stay low and the chemistry is set mostly by season and by how much each tributary has touched lateritic or mangrove soils downstream (FAO inland fishery source book, Guinea).

The defining feature is the wet-season pulse. Rain falls in a concentrated block from roughly May or June through October, and discharge climbs steeply, drowning the rapids, spilling rivers across their floodplains, and connecting channels and seasonal pools that sit isolated the rest of the year. When the rain stops the rivers fall fast, the rapids re-emerge, and the floodplain pools shrink and warm. That cycle is the engine of reproduction for much of the fauna. A striking quarter of the ecoregion's endemic fish are rivulines — killifish such as Aphyosemion and Epiplatys — and some of them are true annuals: they spawn in the soil of temporary floodplain pools, the adults die as the pools dry, and the eggs sit out the dry season in the mud, hatching when the floods return. The fishes here are built around water that appears and vanishes on a schedule (FEOW Ecoregion 511).

Lower down, the habitat flips to estuary. The big Guinean rivers open into some of the most extensive mangrove forests in West Africa — Guinea alone held on the order of 3,000–4,0 mi² of mangrove in recent decades — where the substrate turns to mud, the water turns brackish and tidal, and salinity swings with the seasons. This is a different world for fish: euryhaline and estuarine species, tilapiines that tolerate salt, and predators that move up and down with the tide and the flood. So the ecoregion stacks three habitats end to end — cool rocky highland streams, warmer middle-river rapids and floodplains, and tidal mangrove estuaries — and a river-fish community that partitions itself accordingly. The mangrove belt is also the most heavily damaged: it shrank by roughly half over forty years, at a clip the FEOW profile puts near 4.2% a year (FEOW Ecoregion 511).

The cichlid fauna

The Konkouré is one of the richest of the Atlantic basins, holding around 88 fish species, and about a fifth of them are shared with no other Upper Guinean river — a level of local endemism that marks this as its own faunal province rather than a watered-down version of the Niger. Cichlids are a large part of the picture. The tilapiines have diversified strongly across Upper Guinea, with roughly nine species, most of them endemic to the region, and the family runs from open-water grazers down to small, secretive cave-spawners (FEOW Ecoregion 511).

The atlas roster for Northern Upper Guinea is built from that fauna. The largest cichlids are the sand-sifting Tylochromis, deep-bodied lower-river and estuary fish with thick lips and a habit of grubbing through soft bottoms; the region holds three on the roster — Tylochromis leonensis, Tylochromis jentinki, and Tylochromis intermedius — part of a West African coastal group whose members range across the rivers from the Gambia south toward Ghana, favoring the slower, deeper, lower reaches. The zebra tilapia Heterotilapia buettikoferi (long known as Tilapia buettikoferi) is the other heavyweight, a boldly black-and-pale-barred cichlid of the lower coastal rivers from Guinea-Bissau to western Liberia, where it keeps to rocky-bottomed deeper water rather than small creeks; it was lifted out of Tilapia into its own genus in 2013.

The predators are the jewelfish. Hemichromis fasciatus, the banded jewelfish, is a stocky, five-spotted piscivore that hunts other fish through West African rivers and floodplains and grows to better than 10 in. Hemichromis bimaculatus, the red jewel cichlid familiar to aquarists, is a smaller, blood-red, blue-flecked fish of streams and overgrown margins, most at home where forest vegetation overhangs the water. Both are pair-bonding substrate spawners that guard their young hard, which is exactly the behavior that made the genus a hobby staple. The roster's dwarf cichlid is the yellow krib, listed here as Pelvicachromis humilis but now placed in the genus Wallaceochromis (Lamboj, Trummer & Metscher, 2016): an unusually large 'krib' that ranges from Guinea through Sierra Leone into Liberia, including the Kolenté basin, living in small shaded forest streams and oxygen-rich tributaries and spawning in caves and crevices.

One roster entry needs a caveat. Sarotherodon steinbachi is, in current usage, a cichlid endemic to Lake Barombi Mbo, a crater lake in Cameroon far to the east — not a fish of the Guinean coastal rivers. The genus Sarotherodon is genuinely present in this ecoregion's estuaries, but as the blackchin tilapia S. melanotheron and its subspecies, which range through the mangrove rivers of Guinea and Sierra Leone; the roster's species name does not match a Northern Upper Guinea population. Set against the well-placed Tylochromis, Heterotilapia, Hemichromis, and Wallaceochromis, the cichlids here read as a classic Upper Guinean assemblage: a few big bottom-feeders and estuary tilapias, hard-fighting jewelfish predators, and a regional dwarf cichlid, spread along the same highland-to-mangrove gradient as the rivers.

Conservation

Two pressures dominate this ecoregion, and both come straight out of the Fouta Djallon. The first is bauxite. Guinea sits on some of the largest bauxite reserves on Earth and is now among the world's top producers, and the mining heartland — the Boké region and the highland zone behind it — drains into exactly these rivers. Open-pit extraction strips vegetation wholesale; one accounting from Boké put the cleared area at over 5,000 hectares, including more than 3,000 hectares of forest, in roughly six decades of operation. The water-quality signature of the mines is unmistakable: studies in the Boké region describe river and stream water running brownish to reddish-orange, with low pH, high conductivity, and elevated sulfate, iron, and heavy metals from acid drainage and leaching of spoil. For fish that evolved in soft, clear, low-conductivity highland water, that is a direct assault on water chemistry, and the sediment load smothers the rocky interstices that rheophilic species depend on (bauxite mining impacts, Boké region, EJOSDR; Mongabay).

The second pressure is dams, and the Konkouré has caught the worst of it. The river already carried the Garafiri dam (built 1995–1999) and the Kaléta plant, and the much larger Souapiti hydropower scheme filled its reservoir from 2019 and went into operation in 2021, flooding villages and a long stretch of valley. A before-and-after fish survey on the Konkouré around Tondon recorded the cost: 34 species in 12 families before the dam, with cichlids the best-represented family at 7 species, dropping to 16 species in 7 families afterward, the river-loving and migratory groups (including Osteoglossidae and others) thinning out while a few reservoir-tolerant cyprinids and claroteid catfish increased. Catches fell in both wet and dry seasons. A run-of-the-highland river converted to a still reservoir loses precisely the fast, oxygenated, rocky habitat that distinguishes this fauna, and replaces a seasonal flood pulse with a managed one (Souapiti ichthyofauna study, Konkouré at Tondon; Souapiti displacement, Human Rights Watch).

Underneath both lies the slow degradation of the Fouta Djallon itself. The 'water tower' is losing its forest and its sponge: deforestation, burning, and erosion on the highlands reduce dry-season flow and load the rivers with sediment, and analyses have questioned whether the massif can keep regulating West Africa's water as it once did. Downstream, the mangrove estuaries — nursery and habitat for the Tylochromis and the salt-tolerant tilapias — have been cut back by roughly half in forty years for rice, fuelwood, and salt-making. None of the roster cichlids is currently assessed as globally threatened (the yellow krib, as Wallaceochromis humilis, is rated Least Concern), but the trajectory of the habitat is the warning sign. A stripped highland water tower, mining chemistry in the headwaters, and dams converting torrents to reservoirs are all hitting an Upper Guinean fauna whose whole character is built on cool, clean, fast, seasonally pulsing water (Fouta Djallon Highland Water Atlas, World Bank; FEOW Ecoregion 511).

Where these cichlids live

Geography & hydrology

Water & habitat

The cichlid fauna

Conservation

Sources

Cichlids recorded here

Anomalochromis · 1

Coelotilapia · 1

Enigmatochromis · 1

Hemichromis · 1

Heterotilapia · 1

Pelvicachromis · 1

Rubricatochromis · 1

Sarotherodon · 1

Tylochromis · 3

Wallaceochromis · 2