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.
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hour by hour
slide your finger or mouse over the chart to see each hoursee hour-by-hour table
why this index at —?
choose the day
the fishing month at a glance
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.
everything about the piavuçu
how to recognize it
Large, broad head for a piau, small mouth with incisor teeth. Greenish-to-olive back, yellowish flanks. Juveniles with dark vertical bands. The piapara is more silvery and has three dark spots on the flank. The piau-três-pintas is smaller and has three well-marked black spots.
Also called: piavuçu, piauçu, piau-açu, piavussu, boga
don't confuse with:
where found
open on the large mapWhere to look: Backwaters, bank edges, bays and reservoirs; sand or mud bottom near submerged timber.
Native to the Pantanal (Paraguay, Cuiabá, Miranda, Aquidauana, Taquari). Introduced to upper Paraná reservoirs (Grande, Paranaíba, Tietê, Paranapanema, Ivaí) and present in pay lakes.
native to the basins
introduced in
states
Mato Grosso do Sul, Mato Grosso, São Paulo, Paraná, Goiás, Minas Gerais
when to fish
best season
Warm months are best. In winter chum takes longer to draw fish in.
best time of day
Daytime, with peaks at dawn and dusk. Feeds by day, best in the morning and late afternoon. On chum, it responds at any hour.
what affects the piavuçu
cold and cold fronts
A cold front knocks out the chum for 1 to 2 days.
atmospheric pressure
Stable weather is better.
moon
Small effect.
rain
Light rain doesn't matter.
water level
In reservoirs, stable level. In rivers, falling water concentrates fish in backwaters.
noise
Wary over shallow chum; keep the boat away.
wind
A light chop helps hide the line.
depth
Bottom, 2 to 6 m, near the chum.
how to fish
natural baits
- green or boiled corn
- cornmeal dough (fubá)
- minhocuçu
- boiled soybean
tip from an angler
Chum the spot with corn for a day or two. Set the hook on the first firm pull, without waiting for the second.
- rod
- 6' to 7', medium action, 10 to 25 lb
- spinning / baitcasting reel
- spinning reel 2500 to 4000
- line
- monofilament 0.30 to 0.40 mm or braided line 20 lb
- leader
- fluorocarbon 25 to 30 lb
- hook
- 1/0 to 2/0, short, chinu type
accessories
- corn chum
- alicate
catch and release
Hold it by the belly and caudal peduncle, remove the hook with pliers and return it to the water.
rules for the piavuçu
Rules change; before keeping or transporting fish, check with the state environmental agency.
MS: minimum 38 cm
38 cmMS details
Minimum size for piavuçu in MS. Counts as the only native fish in the recreational bag limit.
Source: Decreto estadual MS nº 15.375/2020 (amends Decreto nº 15.166/2019), art. 9º - Semadesc/Imasul
MT: minimum 38 cm
38 cmMT details
Minimum size in the Paraguay basin in MT. Recreational anglers may keep fish only for on-site consumption.
Source: Lei estadual MT nº 9.096/2009, art. 28 and Annex I (Paraguay Basin) - Sema-MT
Paraná basin: 40 cm by common name
40 cmSPPRMGGO details
IN Ibama 26/2009 uses "piavuçu" as one of the names of the piapara/piau-verdadeiro group, with 40 cm. In the Paraná basin, respect 40 cm.
Source: Instrução Normativa Ibama nº 26/2009 (fishing rules for the Paraná River basin), Annex
other rules that mention the piavuçu (3)
Minimum size: 38 cm
MS details
Source: Decreto estadual MS nº 15.166/2019, art. 9º (as amended by Decreto nº 15.375/2020)
Minimum size: 38 cm
MT details
Minimum size: 40 cm
SPPRMGGOMSDF details
piracema and closed seasons
Each bar is the period when fishing is prohibited or restricted. The green line is today. Tap the name to see what is still allowed.
Spawning closure (piracema) in the Pantanal of Mato Grosso do Sul
Allowed: Subsistence fishing by riverside residents and authorized scientific fishing. Decree 15.166/2019 (art. 11, §5) allows catch and release only in February and only in the channels of the Paraguay and Paraná rivers. For the rest of the period, not even catch and release is allowed. Check the Imasul portaria for each season.
Source: Decreto estadual MS nº 15.166/2019, art. 11; IN IBAMA nº 201/2008
Spawning closure (piracema) in Mato Grosso (all basins)
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.
Conservation: In the Paraná basin it is an alien species.
how much it weighs without taking it out of the water
estimated weight
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how we calculate
Length-weight relationship W = a·Lb (a = 0.01096, b = 3.19; FishBase). It's an average: a fat or lean fish can vary by 10% to 20%.
more about the piavuçu
A large, big-headed piau native to the Paraguay basin. It eats seeds, fruit, leaves, insects and mollusks. It was widely used in fish farming and escaped into upper Paraná reservoirs, where it formed large populations. There it is alien, not native. Caught on chum with corn, dough and minhocuçu (giant earthworm), it nibbles the bait before taking it: whoever waits too long to set the hook loses the fish. It fights well, with strong runs to the bottom. Outside the chum, look for backwaters and banks with sandy bottoms. In MS and MT the minimum size is 38 cm.
Family: Anostomidae · omnivore
fun facts
- The scientific name macrocephalus means large head.
- It was one of the first native species raised on a large scale in Center-South fish farming.
in the kitchen
Good flesh, with bones; fried in thin steaks or baked.
similar species
sources and references (6)
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 — Megaleporinus macrocephalus (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 — Megaleporinus macrocephalus (avaliação global: Pouco Preocupante, LC, 07/11/2018)Global assessment. Link given on the FishBase entry (Red List, version 2025-2).
- scientific Ramirez, J. L.; Birindelli, J. L. O.; Galetti Jr., P. M. (2017). A new genus of Anostomidae (Ostariophysi: Characiformes): diversity, phylogeny and biogeography based on cytogenetic, molecular and morphological data. Molecular Phylogenetics and Evolution 107: 308–323.Creates the genus Megaleporinus (formerly Leporinus).
- scientific Britski, H. A.; Silimon, K. Z. S.; Lopes, B. S. (2007). Peixes do Pantanal: manual de identificação. 2ª ed. Brasília: Embrapa Informação Tecnológica. 227 p.Treats the species as Leporinus macrocephalus (old genus). Print work; the URL is the bibliographic record in FishBase, which cites this work for the species.
- scientific Ota, R. R.; Deprá, G. C.; Graça, W. J.; Pavanelli, C. S. (2018). Peixes da planície de inundação do alto rio Paraná e áreas adjacentes: revised, annotated and updated. Neotropical Ichthyology 16(2): e170094.Annotated list of species of the upper Paraná River, indicating native and non-native ones. Open access; species name checked in the text.
how we calculatewhere 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: