Breeding the Nile Bichir (Polypterus bichir)

Polypterus bichir spawns in weeds and reportedly guards the eggs and young; it reaches over 70 cm and is not a practical home-aquarium breeding subject.

Overview

The Nile Bichir (Polypterus bichir) is the largest commonly kept bichir, reaching about 74 cm TL and roughly 2.7 kg. It is an essentially piscivorous, facultative air-breathing fish; the nominal subspecies is known from the Chad basin, Nile River basin and Lake Turkana, the other from the Senegal, Gambia, Geba, Volta and Niger rivers (FishBase). Polypterids have rarely bred in captivity (Wikipedia), and the adult size of P. bichir makes it impractical for the home aquarium.

Sexing

As in other Polypterus, the clearest external difference is the anal fin: mature males develop a broader, thickened anal fin that forms a cup during fertilisation, while females are typically larger-bodied (Wikipedia).

Conditioning

Polypterid spawning is tied to the rainy season and changes in temperature and water chemistry. Conditioning means well-fed adults in a very large system, followed by simulated seasonal change; the conductivity is lowered with cooler, softer water before temperature is raised (genus accounts, Wikipedia).

Spawning Behavior & Trigger

Spawning in Polypterus involves the male cupping his anal fin beneath the female to catch and fertilise eggs as they are released (Wikipedia). The trigger is imitation of the rains - generous water changes with soft, cool water that drop conductivity, followed by a temperature increase.

Egg & Fry Care

FishBase reports that in P. bichir the eggs are deposited in weeds, where the adult fish guards the eggs and young - parental care that is unusual within the genus. Eggs are slightly adhesive and stick to vegetation; polypterid larvae hatch with branched external gills resembling those of salamander larvae, which are lost with growth (genus account, Wikipedia).

Common Challenges

The species' large size demands enormous volumes to house breeders and to simulate a flood cycle. Pair compatibility, the rarity of any home success, and the difficulty of recreating seasonal cues make this an advanced, essentially commercial project.