Although it does penetrate the lower basins of rivers, particularly the Amazon where it has been collected from the rio Xingu several hundred kilometres from its mouth, this species is predominantly an inhabitant of mangrove swamps, estuaries, and other such saline habitats.

It is particularly common in tidal channels, shallow inshore lagoons, and the lower reaches of rivers.

C. carsevennensis has formerly been synonymised with C. arnoldi but was considered separate by Zarske (2011) using the following combination characters: absence (vs. presence) of a silvery-white to white patch in the centre of some of the flank scales in males, particularly in the lower half of the body; absence (vs. presence) of a horizontal dark body bar in nuptial males; absence (vs. presence) of thin black margins in the dorsal, ventral and anal fins; eggs deposited among submerged vegetation (vs. eg…

It’s known by various vernacular names including ‘Pirá-pacu’, ‘Pira-pucu’ or ‘Diente de cao’ (central Amazon), ‘Bicuda’ or ‘Uena’ (rio Tocantins), ‘Bicuda’ (rio Tapajós), ‘Aguejeta’ or ‘Picua’ (Venezuela), and ‘Moruwi’ or ‘Pirapoko’ (Guyana).

The entire dorsal-fin base is located anteriorly to a vertical through the anal-fin origin and this character distinguishes it from all other ctenolucids except B. lucius and B. xyrekes.

This species was described from Suriname but no specific locality was given.

It’s currently accepted to occur throughout much of the Amazon river system in Brazil, Peru and Bolivia with additional records from coastal drainages of Guyana, Suriname and French Guiana plus the island of Trinidad (Trinidad and Tobago).

Type locality is ‘Tukeit, Guyana’, and this species is known from various river drainages of Venezuela, Guyana, Suriname and French Guiana including the Orinoco, Essequibo, and upper Courantyne (aka Corantijn) basins.

Additional records exist from the upper Amazon basin in Guyana, these presumably corresponding to the Takutu river basin, itself part of the upper rio Branco.

This species appears endemic to and abundant within the upper Suriname River system, Suriname.

Type locality is given as ‘little tributaries of Gran Rio between Ligolio and Awaradam Falls’, this corresponding to a section of the Suriname River, which is known as ‘Gran Río’ in parts of its upper basin, upstream of Brokopondo reservoir and not…

This rich feeding ground is exploited until the sea water returns, at which point the catfishes begin to migrate upstream in massive numbers, moving up the Amazon and its tributaries. Sexually mature individuals are not normally recorded during these events so they’re thought related to feeding and dispersal rather than spawning. The fish are subject to intensive capture by commercial and artisanal fishing operations during this upstream movement.

Study of B. rousseauxii has revealed that sexually mature adults are found only in the western Amazon, with no mature individual ever recorded east of Manaus despite the intensive commercial fishery operating there. The total distance covered by some populations during migration from the delta was as much as 5500 km, making it the longest known in any freshwater fish species.

Apparently this species is polymorphic with body patterning varying significantly depending on locality. Individuals collected from black water habitats tend to be noticeably darker in overall colouration, for example, with this being particularly evident among populations from the Guiana Shield.

The genus Ageneiosus was at one point classified in…