Hydrolycus armatus is a species of dogtooth characin found in freshwater of tropical South America. It is sometimes known as harm, or payara,[1] [2] [3] a name it shares with the related H. scomberoides.
This predatory fish occasionally makes its way into the aquarium trade, but it requires a very large tank.[1] [4] In its native range it is considered a major gamefish.[3] [4]
This species of fish is found in the Amazon, Orinoco and Essequibo basins in tropical South America.[5] They are found in several different freshwater habitats, but often in fast-flowing water.[3] [6] They are typically found in deeper waters during the day.[6] The species is locally common; in a major study of a Venezuelan floodplain river, of the collected fish were H. armatus, and the species was particularly common in creeks and lagoons.[7] At least some populations are migratory.[6]
Hydrolycus armatus are overall silvery. In adults the base of the tail and anal fin is pale yellowish, and the distal part is blackish, contrasting with a narrow white edge at the very tip (unique among Hydrolycus species).[1] [5] [8]
A typically reported maximum total length of this fish is, but records show specimens up to in Venezuela[2] and more than in Brazil.[3] It typically weighs up to, but can reach almost .[3] It has frequently been confused with the generally smaller H. scomberoides.[1] [5] H. armatus reaches maturity when at least long.[6] Like other dogtooth characins, it has very long pointed canine teeth. In H. armatus these can surpass in length in large individuals.[2] These are used for spearing their prey, usually other fish.[8]