Oxydoras niger
The largest of the armored catfish: over 1 m and 10 kg. Roots through the mud bottom for larvae and detritus and fights hard.
Also called: cuiú-cuiú, cuiu-cuiu, bacu, abotoado, cujuba, peixe-carneiro
Giant doradid, with a row of sharp bony plates along the flank. Travels in schools over mud bottoms in rivers and lakes and feeds on detritus, insect larvae and crustaceans that it sucks from the bottom. It is caught mainly by artisanal fishers and has a lower market value than the big leather catfish, but it often shows up on the line of anglers bottom fishing with natural bait for pirarara and jaú. When hooked, it pulls hard toward the bottom and tires the arm. The serrated spines of the pectoral and dorsal fins need care when handling.
Tall body behind the head, tapering to the tail, dark grey to nearly black. A row of hooked bony plates along the middle of the flank. Long snout and small mouth, facing down, with short barbels. Strong serrated spines on the dorsal and pectoral fins. The armado (Pterodoras granulosus) is smaller and has a shorter, rounder head.
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Each card shows the day's index (0 to 100) and, below it, a strip with the index for each hour, from 0h to 23h. from poor to excellent.
Rivers and lakes across the Amazon and Tocantins-Araguaia basins. FishBase also records the São Francisco basin.
Habitat: Mud and sand bottom in rivers, channels and lakes; deep holes in the dry season.
native to the basins
states
Amazonas, Pará, Amapá, Acre, Rondônia, Roraima, Mato Grosso, Tocantins
Best in falling water and the dry season, with the fish concentrated in holes and channels.
Night and twilight. Most active at night and at dusk, rooting along the bottom.
Cold snaps leave the fish still on the bottom.
Little known effect.
Dark nights often produce more in bottom fishing.
Little effect.
A falling river concentrates the fish in holes.
Not very sensitive on the bottom.
Little effect.
Bottom, 3 to 12 m.
natural baits
accessories
Bait resting on the bottom of a hole, and patience. When landing it, watch out for the serrated spines.
Summary of the regulations we found, with the source for each. Rules change; before keeping or transporting fish, check with the state environmental agency.
Conservation: Not on the national list (Portaria GM/MMA 1.667/2026).
In Tocantins the cuiú-cuiú may only be kept at 40 cm or more. In TO anglers may not transport fish until Feb 28, 2029, except 1 native fish; they may consume up to 3 kg on site (Naturatins Ordinance 44/2026).
Source: Portaria Naturatins nº 47/2026, Annex I, as amended by Portaria nº 105/2026
Allowed: Sport and guided fishing only in reservoirs, catch and release with barbless hooks (no keeping, transporting or eating). Subsistence: up to 5 kg per day, for household consumption only.
Allowed: All fishing modalities are prohibited in rivers, including catch and release (Law 9.096/2009, art. 19-A). Exceptions: subsistence fishing from shore (3 kg or 1 fish, no transport or sale) and scientific fishing. Law 13.159/2025 now allows licensed sport fishing in UHE/PCH hydropower reservoirs, natural lakes and border rivers, subject to a scientific study and a license from the environmental agency. We have not confirmed whether these licenses are already being issued.
Allowed: Recreational fishing only in reservoirs, with handline, rod, or spinning or baitcasting reel. Fish may only be eaten on site, not transported. Competitions prohibited. Subsistence: 3 kg + 1 fish. State rules (GO and TO) may be stricter.
Allowed: Recreational fishing only in reservoirs, with on-site consumption. Subsistence: 5 kg + 1 fish. State rules may be stricter.
Allowed: In 2025/26: catch and release with barbless hooks and recreational fishing card; subsistence fishing on foot or from a rowboat, with simple pole or handline.
Source: Portaria Naturatins nº 244/2025 (2025/26 season); INIs MPA/MMA nº 12 and 13/2011
Allowed: The same recreational-angler exceptions as in Portaria 48/2007 apply (handline or rod, 5 kg + 1 fish), unless a stricter state rule applies.
Source: Portaria IBAMA nº 48/2007
Allowed: Recreational anglers with handline or rod, line and hook are outside the Annex II prohibitions, with a bag limit of 5 kg + 1 fish, unless a stricter state rule applies.
Source: Portaria IBAMA nº 48/2007
Allowed: Subsistence fishing only.
Source: Portaria IBAMA nº 48/2007
Allowed: See the exceptions in Portaria 48/2007 and the state rules for each bank.
Source: Portaria IBAMA nº 48/2007
Hold it by the base of the spines with a glove or pliers, without putting your fingers on the plates, and release it facing the current.
Dark, fatty meat, less valued than that of the leather catfish; good in caldeirada and moqueca.
Length-weight relationship W = a·Lb (a = 0.0166, b = 2.99; FishBase). It's an average: a fat or lean fish can vary by 10% to 20%.
estimated weight
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The season weights (months), the time of day and the sensitivities (cold, pressure, moon, wind, rain, tide, strong light, murky water and noise) are the app's editorial estimates, based on the literature below and on the field experience of anglers and guides. They are not official data nor a measurement made for this species, and they may vary by region and year. Closed seasons and legal rules appear in the rules section, with the norm and a link.
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