Breeding the Mottled Bichir (Polypterus weeksii)

Polypterus weeksii is a Congo Basin bichir reaching about 54 cm; reproduction follows the genus pattern of anal-fin fertilisation and is rarely bred in captivity.

Overview

The Mottled Bichir (Polypterus weeksii) is a polypterid of the middle Congo River basin in the Republic of Congo and the Democratic Republic of the Congo, reaching about 54 cm TL. It is a freshwater, demersal, facultative air-breather and is listed Least Concern by the IUCN; its colouration is olive-green to grey above with yellowish underparts and 7-8 dark bars that bifurcate low on the flanks (FishBase). Captive breeding is rare across the genus (Wikipedia).

Sexing

Mature males are recognised by a broader, thicker anal fin that forms a cup during fertilisation - the standard external sex cue across Polypterus (genus account, Wikipedia).

Conditioning

Bichir reproduction is tied to the rainy season and changes in temperature and water chemistry. Adults are heavily fed, then exposed to simulated seasonal change in a large, well-filtered system before any spawning attempt.

Spawning Behavior & Trigger

A ripe male cups his anal fin beneath the female to catch and fertilise eggs as they are released (genus account, Wikipedia). Spawning is triggered by imitating the rains: large changes with soft, cool water that lower conductivity, followed by a temperature rise.

Egg & Fry Care

Eggs are slightly adhesive and stick to vegetation. Polypterid larvae hatch with branched external gills resembling those of salamander larvae, which are lost as the fish grows (genus account, Wikipedia). Bichirs generally show no parental care, so spawn must be protected from the adults.

Common Challenges

Large volumes, reliable pairing, recreation of the seasonal flood cue and predation of eggs and fry by the parents are the chief obstacles; documented home success is scarce.