Taxonomy & naming
Polypterus bichir was described by Bernard Germain de Lacépède in 1803 and is the type species of the genus Polypterus, family Polypteridae, order Polypteriformes. The Polypteridae — the bichirs and the reedfish — form the most basal living lineage of the ray-finned fishes (Actinopterygii), a branch that split from all the others deep in the fossil record; they are genuine "living fossils," carrying a suite of primitive features the rest of the ray-finned fishes lost long ago.
The nominate subspecies, Polypterus bichir bichir, has been documented with 13 to 18 separate dorsal finlets and 11 to 13 pelvic fin rays, a higher finlet count than many of its relatives and a useful field character for telling bichir species apart; a population study from far-northern Cameroon has confirmed the subspecies in the western part of its range. FishBase lists the species under the common name "Nile bichir," but its own epithet, bichir, is itself the older name — a Latinised form of the vernacular word used for the fish along the Nile — from which the whole family and the English common name "bichir" ultimately derive.
Morphology
Polypterus bichir has the classic bichir silhouette: a long, cylindrical, faintly flattened body wrapped in thick, glossy, interlocking ganoid scales — rhombic plates of bone capped with a hard, enamel-like layer — that form a flexible suit of armour. In place of a single dorsal fin it carries a row of separate finlets, 13 to 18 in the nominate subspecies, each a short spine trailing a membrane flag, running from mid-back toward the tail; the paired pectoral fins sit on fleshy, muscular lobes that let the fish prop itself up and crawl along the bottom.
A few features help distinguish it from its relatives: the lower jaw is slightly longer than the upper, and the pectoral fin, when laid back, reaches as far as the first dorsal finlet. It is also one of the largest bichirs in the genus — FishBase records wild individuals up to 29.1 in in total length, well beyond the size most aquarium bichirs ever reach.
Behind the gills lies a pair of primitive, sac-like lungs, and P. bichir is a facultative air-breather that favours shallow water and habitually basks near the surface to gulp air. Its eyesight is poor, and like other bichirs it hunts chiefly by smell.
Habitat
Polypterus bichir has one of the broadest ranges of any bichir, recorded across the Nile River basin, the Lake Chad basin, and the Senegal, Gambia, Geba, Volta and Niger river systems — a span running from the Atlantic coast of West Africa in the west to the Nile drainage in the east. A population study from far-northern Cameroon, within the Chad basin, has confirmed the western edge of that range, and distribution mapping shows verified records stretching continuously from the Gambia and Senegal through to the Nile.
Within that range it favours shallow water, where its habit of basking near the surface to gulp air puts its facultative lungs to direct use. These Sudano-Sahelian floodplain rivers run warm and can turn slow, turbid and short of dissolved oxygen in the dry season — exactly the conditions in which an air-breathing fish has the advantage over gill-only competitors.
Feeding
Like other bichirs, Polypterus bichir is a nocturnal, scent-hunting ambush predator of the bottom rather than a sight-hunter; its poor eyesight is compensated by a keen sense of smell that lets it locate prey in murky water or after dark. In the wild it is an opportunistic carnivore, taking aquatic insect larvae, worms, crustaceans, molluscs and any fish small enough to swallow.
In the aquarium it takes meaty foods readily — earthworms, prawn, mussel, squid, bloodworm and, once settled, sinking pellets. Given its large adult size it needs a substantial, consistent meaty diet, but like other bichirs it is a slow, deliberate feeder that can be outcompeted by faster tankmates, so food is often best offered after dark or placed close to where the fish is resting.
Mating
Bichir courtship is built around external fertilisation with an unusual delivery system. A male follows and nudges a ready female, and the pair swim together among cover; the male then cups his thickened, muscular anal and pelvic fins into a shallow pouch, into which the female releases a few eggs at a time. The male fertilises the eggs in this cradle, and the small, adhesive eggs are scattered onto plants and the substrate — a sequence repeated many times over the course of a spawning bout.
As in other Polypterus, the sexes are told apart chiefly by this spawning equipment: mature males have a noticeably broader, thicker anal fin than females, most pronounced in breeding condition.
Breeding
Polypterus bichir is an egg-scatterer with no parental care: the adhesive eggs are simply left among plants and on the substrate, and adults will eat both eggs and fry if given the opportunity. As in other bichirs, the eggs hatch within a few days into larvae bearing feathery external gills behind the head — much like a newt's tadpole — which are absorbed as the young mature.
Deliberate spawning is rarely achieved in home aquaria for any bichir, and this species is no exception; it typically needs seasonal or flood-like triggers that are hard to reproduce in a tank. Unlike the Senegal bichir, which is now farm-bred in quantity, most Polypterus bichir in the trade are still wild-caught.
In the aquarium
Its adult size — up to 29.1 in in the wild — puts Polypterus bichir among the larger bichirs kept in the hobby, and care guides for the bigger species in the genus recommend a long tank on the order of 6 by 2 feet of floor space, furnished with a fine sand substrate and plenty of hiding spots such as driftwood, PVC pipe or clay pots, under dim lighting suited to a nocturnal hunter. General bichir husbandry parameters apply well: warm water around 79–82 °F, a pH of roughly 6.5 to 7.5, and moderate hardness of about 5 to 15 dGH.
Two cautions matter as much as any water parameter. The tank must be fully and tightly covered — bichirs, this species included, are determined escape artists that exploit the smallest gap — while still leaving an air gap at the surface for the fish to breathe. And because this is a predator that will swallow any tankmate small enough to fit in its mouth, companions need to be both too large to eat and too calm to harass it. Its ganoid armour makes it a hardy fish, generally more tolerant of medications than scaleless catfishes, but keepers should expect a wild-caught animal that may need time and quarantine to settle in.
Conservation
Polypterus bichir is assessed as Least Concern on the IUCN Red List, an assessment reflected in FishBase's own listing dated January 2020. It is one of the most widely distributed bichirs in Africa, ranging continuously from West African coastal rivers to the Nile, and it faces no species-wide threat.
The cached sources for this account do not document specific population trends or localised threats to P. bichir. As with other fish of the Sudano-Sahelian floodplains, regional pressures such as wetland drainage, damming and drought could affect local populations in parts of its range, but the species' broad distribution and tolerance of varied conditions leave it in a secure position overall.