Taxonomy & naming
Hassar gabiru was described by Birindelli, Fayal & Wosiacki in 2011, part of a taxonomic revision that clarified the boundaries of the genus Hassar within the thorny catfish family Doradidae. Doradids have historically been shuffled among several old generic names, and species now placed in Hassar were at times confused with other doradids before the genus was properly circumscribed; Birindelli and colleagues distinguished Hassar species using swim-bladder shape and the morphology of the midlateral row of bony scutes that runs the length of the body.
The genus sits within Doradidae, the thorny or 'talking' catfishes, a large South American family known for locking pectoral spines and for producing audible sounds. The Catalog of Fishes treats Hassar gabiru as the currently valid name, with no synonymy to report from the cache.
Morphology
Hassar gabiru reaches a maximum recorded size of about 11 in total length, a real adult size that should be planned for from the outset — this is not a fish that stays pocket-sized. Like other doradids it has no scales in the conventional sense; instead a row of bony, often hook-bearing scutes runs along each flank, and the rest of the skin is naked. That scaleless, plated skin makes it sensitive to copper and to many standard fish medications, so any treatment should be dosed conservatively, as with loaches, puffers and true eels.
The genus carries stiff, serrated pectoral and dorsal spines that lock into place. In Hassar and other doradids these spines are used defensively and can be rasped to produce sound (the 'talking catfish' trait of the family), and they readily snag in aquarium nets and can jab a careless hand — this fish should be moved in a container rather than netted.
Habitat
The species is endemic to the middle and upper Xingu River basin above the Volta Grande rapids near Altamira, Brazil, with a known range roughly between 4°S–14°S and 52°W–55°W. The Xingu at this reach is an oligotrophic clearwater river — low in dissolved nutrients and suspended sediment (on the order of 5–20 mg/L), with high water transparency — very different from the sediment-laden whitewater of the main Amazon channel.
Hassar gabiru is associated with swift-flowing sections of the river over fine sand substrate, and is typically collected at night, consistent with a nocturnal, benthic lifestyle. As an upper-basin Xingu endemic restricted to a single, well-defined stretch of river, its habitat requirements are narrow even though the water chemistry itself is unremarkable soft, clear river water rather than anything extreme.
Feeding
This is a nocturnal, benthic micro-predator and detritivore in the pattern typical of doradid catfishes, foraging over the sandy riverbed mainly after dark for small invertebrates and organic detritus. It is not documented as a plant-grazer or specialist feeder.
In the aquarium it should be offered sinking pellets, frozen foods and other prepared foods after lights-out, when it is most active and not out-competed by diurnal tankmates. Cover and shaded feeding areas help it settle into a regular feeding routine.
Mating
No spawning behaviour has been documented for Hassar gabiru in the cache, and this genus has no track record of home breeding in the aquarium hobby. Doradid courtship and spawning biology varies across the family, and without direct observation for this species it would be speculative to describe a mating sequence here.
Breeding
Hassar gabiru is not known to have been bred in captivity; every specimen in the trade is wild-caught. This matches the pattern for the great majority of Doradidae outside the handful of armored callichthyid relatives (a different family) that build bubble nests — most thornycats, including Hassar, are simply not reproduced by hobbyists or commercial farms. Prospective keepers should treat this as a wild-collection-only species rather than plan around captive breeding.
In the aquarium
Plan for the real adult size of around 11 in total length — aquarium reports for the genus Hassar more commonly run 6–10 in, but a tank sized for the larger figure avoids the classic catfish size trap. This species is reported as difficult to acclimate if it arrives from import in poor condition, though it settles well once established; it does best with dense vegetation or other cover for security, and smaller individuals can be shy around larger tankmates despite not being aggressive itself.
Because it is scaleless with bony plating rather than true scales, dose copper-based and other medications conservatively. Its stiff, locking pectoral and dorsal spines should be respected at every handling step — move it in a net-free container rather than risk a snagged net or a jabbed hand. Being nocturnal, it appreciates shaded retreats by day and is best fed after the lights go out. Water should reflect its native Xingu River conditions: soft, clear and not heavily mineralized, rather than hard or alkaline.
Conservation
The IUCN Red List assesses Hassar gabiru as Least Concern, as of a 2018 assessment. It is endemic to a specific reach of the Xingu River, a system that has undergone major hydrological change from the Belo Monte dam complex near Altamira, immediately downstream of Volta Grande — the LC rating should be read against that backdrop of ongoing basin-scale disturbance rather than as a guarantee of a stable future.
As with most Doradidae in the trade, aquarium supply relies entirely on wild collection rather than captive breeding, so demand translates directly into pressure on the wild Xingu population.