Minimum size in Tocantins
10 cmTOTocantins-Araguaia
In Tocantins the black piranha may only be kept if it is 10 cm or longer.
Source: Portaria NATURATINS/GABIN nº 47/2026 (annexes amended by Portaria nº 105/2026)
fishing forecast
black piranha
Serrasalmus rhombeus · Serrasalmidae · predator
Freshwater
The largest piranha in the Amazon, with red eyes and a very powerful bite. It steals bait, cuts line and fights hard for its size.
Also called: piranha-preta, piranha-de-olho-vermelho
- common size
- 20–35 cm
- maximum
- 50 cm
- common weight
- 0.5–1.5 kg
- record/max.
- 3.8 kg
- depth
- 0.5–8 m
- ideal water
- 26–31 °C
fishing forecast
the right time
the right time
to be on the water
Choose the place and the species. The index, from 0 to 100, combines weather, sun, moon and tide with each fish's habits. Up to 28 days, with each day's confidence.
Reading the weather across 3 global models and 31 simulations…
0—
index Score from 0 to 100 for the fishing conditions of each hour. It reads weather, sun, moon, tide and the species' habits. It doesn't promise fish: it tells you when the water is on your side. 0–24 poor · 25–44 fair · 45–64 good · 65–84 very good · 85–100 excellent.
today
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confidence —
confidence How much you can trust the weather forecast for the day. It drops with distance and when the models disagree. It is not the chance of catching fish.
models and trend Up to 16 days, three global weather models (the European ECMWF, the American GFS and a high-resolution blend) read hour by hour; when they disagree, the light band on the chart widens. Beyond that it's a trend: 31 runs of the American GEFS model. Confirm when it's 1 week out.
window Consecutive hours with the index near the day's peak and no danger alert. It is the time to have the bait in the water.
hour by hour
slide your finger or mouse over the chart to see each hoursee hour-by-hour table
why this index at —?
next 7 days
chart: bar height = day's index · line = variation between models · striped = trend · fainter = less confidencechoose the day
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.
4-week calendar
the fishing month at a glance
plan a trip
what's the best window for the crew?
Choose how many fishing days. We compare each stretch by its average index, discount days with a warning or closed season, and show the 3 best.
trend for the coming weeks
Line: the middle value of 31 simulations of the American GEFS model. Band: where 8 out of 10 fall. Narrow, firm trend; wide, high uncertainty.
the species
everything about the black piranha
overview
who is the black piranha
The black piranha is the largest piranha and lives in clear- and blackwater rivers and lakes of the Amazon and Araguaia-Tocantins. Adults usually travel alone or in small groups, unlike the red piranha, which forms schools. It eats fish, fin pieces and scales, and quickly attacks any bait with the smell of blood. It has the strongest bite ever measured in fish relative to body size. For peacock bass anglers it is a nuisance, because it destroys silicone lures and cuts line; for those seeking action, it guarantees a strong fight and jumps. It requires a steel leader.
fun facts
- Studies measured a bite force in adults of about 30 times the fish's own body weight.
- It replaces its teeth in blocks, one side of the mouth at a time, and is never left toothless.
how to recognize it
identification
Tall, diamond-shaped body, silver-grey to nearly black in large fish. Ruby-red eye. Protruding lower jaw with sharp triangular teeth. Serrated keel on the belly and tail with a dark band. The red piranha has a red belly and a shorter, rounder snout. The young pirapitinga has a red chest but molar teeth.
distribution
open on the large map where found
Rivers and lakes of the Amazon and Araguaia-Tocantins basins, most abundant in clear- and blackwater.
Habitat: Backwaters, beaches, rocky stretches, shorelines, lake mouths and pools; also in rapids.
native to the basins
AmazonTocantins-Araguaia
states
Amazonas, Pará, Amapá, Acre, Rondônia, Roraima, Mato Grosso, Tocantins, Goiás, Maranhão
when to fish
best season
time of yearbest: Jun–Nov
JanFebSeaAprMayJunJulAugSepOctNovDec
Bites all year; in the dry season it concentrates more and is more aggressive.
best time of day
Daytime. Active all day, with more strikes early and late in the afternoon.
what affects the black piranha
sensitivity The little bars show how much each factor affects this species. Five full: it feels it a lot.
sensitivity The little bars show how much each factor affects this species. Five full: it feels it a lot.
cold and cold fronts
A cold snap (friagem) reduces activity.
atmospheric pressure
Little effect.
moon
Little effect.
rain
Little effect.
water level
Dry season concentrates them and makes them more aggressive.
noise
Almost indifferent; splashing on the water may even attract them.
wind
Little effect.
depth
From surface to bottom; follows the lure.
how to fish
- rod
- 5'6'' to 6'0'', medium action, 10 to 20 lb
- spinning / baitcasting reel
- spinning reel 2500 to 3000 or baitcasting reel 100
- line
- braid 20 to 30 lb
- leader
- wire leader 20 to 40 lb, 15 to 20 cm (essential)
- hook
- long-shank hook 1/0 to 3/0
lures
- colher
- small mid-water lure
- feather jig
natural baits
- piece of fish
- beef heart or beef
- guts
accessories
- long-nose pliers
- small boga-grip
tip from an angler
Use a long-shank hook and a short steel leader. Set the hook quickly: it strips the bait in seconds.
rules for the black piranha
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).
piracema closures in the basins where the species lives
Closed season in Goiás (state rule)
01/11 to 28/02GO
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.
Spawning closure (piracema) in Mato Grosso (all basins)
01/10 to 31/01MT
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.
Spawning closure (piracema) in the Araguaia River basin
01/11 to 28/02GOTOPAMT
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.
Spawning closure (piracema) in the Tocantins and Gurupi river basins
01/11 to 28/02TOPAMAGO
Allowed: Recreational fishing only in reservoirs, with on-site consumption. Subsistence: 5 kg + 1 fish. State rules may be stricter.
Spawning closure (piracema) in Tocantins (state rule)
01/11 to 28/02TO
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
Closed season in the rivers of Marajó Island (PA)
01/01 to 30/04PA
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
Closed season in the Amazon basin in Amapá
15/11 to 15/03AP
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
Closed season in Roraima
01/03 to 30/06RR
Allowed: Subsistence fishing only.
Source: Portaria IBAMA nº 48/2007
Border rivers MT/RO and MT/PA
05/11 to 28/02MTROPA
Allowed: See the exceptions in Portaria 48/2007 and the state rules for each bank.
Source: Portaria IBAMA nº 48/2007
catch and release
catch and release Releasing the fish alive, quickly and with a wet hand. During a closed season it isn't always allowed: what the regulation says applies.
catch and release Releasing the fish alive, quickly and with a wet hand. During a closed season it isn't always allowed: what the regulation says applies.
Never put your fingers near the mouth. Hold it firmly behind the head or with a boga-grip, and remove the hook with pliers.
in the kitchen
White, tasty flesh with bones. Piranha broth is traditional in the Pantanal and the Amazon; fried is also good.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.01288, b = 3.19; FishBase (bayesiano, espécie + gênero)). It's an average: a fat or lean fish can vary by 10% to 20%.
estimated weight
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sources and references
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.
- scientific FishBase — Serrasalmus rhombeus (ficha da espécie)Names, distribution, biology, length-weight relationship and references. Page checked on October 13, 2026.
- official Portaria GM/MMA nº 1.667, de 27 de abril de 2026 — Lista Nacional Oficial de Espécies da Fauna Ameaçadas de Extinção (peixes e invertebrados aquáticos)Most recent national list. The species is not on it (search by scientific name in the text published in the DOU, checked on October 13, 2026).
- scientific IUCN Red List — Serrasalmus rhombeus (avaliação global: Pouco Preocupante, LC, 22/12/2020)Global assessment. Link given on the FishBase entry (Red List, version 2025-2).
- scientific Jégu, M. (2003). Serrasalminae (pacus and piranhas). In: Reis, R. E.; Kullander, S. O.; Ferraris Jr., C. J. (orgs.). Check List of the Freshwater Fishes of South and Central America. Porto Alegre: EDIPUCRS, p. 182–196.Printed book chapter; the URL is the bibliographic record on FishBase, which cites the chapter for the species.
- scientific Goulding, M. (1980). The fishes and the forest: explorations in Amazonian natural history. Berkeley: University of California Press. 280 p.Printed work; the URL is the bibliographic record on FishBase, which cites this work for the species.
similar species
how we calculate
where each number comes from
The weather comes from three independent global models, cross-checked hour by hour: when they agree, confidence goes up; when they diverge, the band between them shows on the chart. Beyond 16 days, we use the GEFS ensemble of 31 simulations: if 20 of the 31 predict rain, the chance of rain is 65%. Sun and moon are calculated astronomically, with no uncertainty.
The index adds up, weighted for each species: time of day (species curve anchored to real sunrise and sunset), moon (transits, rise and set, phase), pressure (3 h trend and 24 h swing), water temperature (in rivers, estimated from air temperature; at sea, estimated by an ocean model), wind, rain, clouds, tide and the month in the species' cycle.
sources for this lookup
how accurate the forecast is
Accuracy measured in the reference project (4 regions, 93 days, forecast vs. observed): maximum temperature is off by 0.6 °C on average the next day and 1.7 °C at 7 days; rain of 5 mm or more is detected 76% of the time the next day and 57% at 7 days. Detection isn't everything: the false alarm rate isn't published here yet, and 93 days in 4 regions is still a small sample. We now also measure every day, at the app's destinations: