black prochilodus

The Black Prochilodus has a fusiform and laterally compressed body, typical of active bottom swimmers, reaching a maximum standard length of about 48.5 cm (up to 52.5 cm in females) and a weight of up to 3 kg. Its most distinctive feature is its protractile mouth located on the underside of the head, adapted for scraping the substrate.

The lips are thick and horny, forming a kind of adhesive disk that allows it to cling to the current and feed on the bottom. The general coloration is dark, ranging from dark grey to blackish on the back and sides, with a lighter belly, hence its common name. The fins are usually dark, without distinct bright markings, although variations may exist among populations and seasons.

The Black Prochilodus is a potamodromous species, undertaking long migrations within freshwater systems in response to hydrological cycles. Its behavior is rhythmically tied to flood events: during the rainy season, adults migrate laterally from peripheral habitats (lagoons, flooded forests, blackwater tributaries) to the main white-water rivers to spawn.

After spawning, they return to feeding areas to replenish their energy reserves. A major behavioral trait is the formation of large schools during recruitment migrations (upstream juvenile movements) and spawning.

These massive movements, locally known as "mijano" in Ecuador, can involve thousands of individuals moving over hundreds of kilometers. The species is also known for its local daily relocation movements, moving to shallow areas at dusk to feed and returning to the main channel or deeper waters during the day to avoid predators.

The Black Prochilodus is a specialized detritivore. It primarily feeds on decomposing organic matter (detritus), benthic algae, biofilm, and fine sediments which it scrapes from river bottoms, rocks, and muddy substrates using its horny lips.

This benthic feeding plays a crucial ecological role in stirring up sediments and recycling nutrients in the water column. During periods of intense migration (breeding or juvenile upstream movements), feeding activity almost ceases, as evidenced by the high proportion of empty stomachs observed in migrating individuals.

Reproduction in the Black Prochilodus is closely synchronized with the flood cycle of the Amazon rivers. Spawning typically occurs during the rising water season (March-April in the Ecuadorian and Peruvian Amazon), when adults migrate to the main rivers with turbid and well-oxygenated waters.

Unlike some fish species that build nests, P. nigricans spawns in open water. The eggs are semi-pelagic and slightly sticky. Fertilization is external. A female can produce a large quantity of eggs (estimated between 200,000 and 500,000 depending on size).

After hatching, larvae passively drift over very long distances (up to several hundred kilometers) to downstream floodplains, which serve as rich nursery areas. Juveniles grow in these floodplains for 6 to 18 months before actively migrating upstream to join the adults. Sexual maturity is reached at around 2 years for males and 3 years for females. No parental care is provided after spawning.