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
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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 dogtooth characin
how to recognize it
Elongated, compressed, silver body with a keeled belly. Large oblique mouth, turned upward, with canine teeth. Long pectoral fins and a very long anal fin; pectoral, pelvic and anal fins yellowish; dorsal and caudal fins translucent. The cachorra (Hydrolycus armatus) has a much taller body and enormous fangs; the dorado is golden and has differently shaped scales.
Also called: cachorra-facão, peixe-cachorro, dourado-cachorro, chafalote, ripa, cachorrão, saranha
don't confuse with:
where found
open on the large mapWhere to look: Mid-water and surface of large rivers, bays, corixo mouths and reservoirs; follows schools of lambaris and sardines.
Amazon, Tocantins-Araguaia, Paraguay, Paraná and Uruguay basins: large rivers, Pantanal bays and reservoirs.
native to the basins
states
Amazonas, Pará, Amapá, Acre, Rondônia, Mato Grosso, Mato Grosso do Sul, Tocantins, Goiás, Minas Gerais, São Paulo, Paraná, Santa Catarina, Rio Grande do Sul
famous destinations
when to fish
best season
Good from March to May and August to October; at the peak of the cold, in the South and the Pantanal, it drops sharply.
best time of day
Daytime, with peaks at dawn and dusk. Hunts by day, with peaks at dawn and in the late afternoon.
what affects the dogtooth characin
cold and cold fronts
A cold front shuts down activity for one or two days.
atmospheric pressure
Stable pressure helps; before a front there is often a peak.
moon
Little effect.
rain
Very muddy water hinders visual hunting.
water level
A falling river concentrates the bait schools, with predators behind them.
noise
Moderately sensitive.
wind
Light chop helps surface fishing.
depth
Mid-water, 0.5 to 4 m.
how to fish
lures
- wobbling spoon
- feather jig
- jerkbait 9 to 11 cm
- mid-water plug
natural baits
- live lambari
- tuvira
tip from an angler
Fast retrieve and a tough leader: the fangs cut thin line.
- rod
- 6' to 6'6", fast action, 12 to 25 lb
- spinning / baitcasting reel
- 2500 to 3000 spinning reel or low-profile baitcasting reel
- line
- braid 20 to 30 lb
- leader
- fluorocarbon 40 to 50 lb or fine wire leader
- hook
- treble hooks #2 to 2/0
accessories
- long-nose pliers
- boga-grip
catch and release
Use pliers and a boga: the teeth cut. Release quickly; the fish loses scales easily.
rules for the dogtooth characin
Rules change; before keeping or transporting fish, check with the state environmental agency.
GO: between 35 and 50 cm
35 cmGO details
In Goiás the cachorra-facão may only be killed between 35 and 50 cm, in the Araguaia-Tocantins and Paranaíba basins, and only for consumption on site.
Source: IN Semad-GO nº 17/2026, Annex I (in force May 28, 2026; on-site consumption only, zero transport)
GO: maximum 50 cm
50 cmGO details
Above 50 cm the cachorra-facão must be returned to the water in Goiás.
Source: IN Semad-GO nº 17/2026, Annex I (in force May 28, 2026; on-site consumption only, zero transport)
TO: minimum 40 cm
40 cmTO details
In Tocantins the cachorra-facão 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
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 Paraná River basin
Allowed: Recreational fishing only for non-native species and hybrids (peacock bass, tilapia, black bass, carp, croaker, etc.; piauçu remains prohibited), with handline, simple pole, or rod with spinning or baitcasting reel, up to 10 kg + 1 fish. In rivers, from shore only; in reservoirs, from a boat or from shore. Prohibited: floodplain lakes, aquatic-animal bait, within 1,500 m of dams and waterfalls, and within 500 m of confluences. Tournaments only in reservoirs and only with non-native species.
Source: IN IBAMA nº 25/2009
Spawning closure (piracema) in Minas Gerais (state rule)
Allowed: Only exotic or hybrid species, 3 kg + 1 fish per day, with handline, rod, simple pole, or spinning or baitcasting reel. Nets prohibited. Keep the minimum distances from dams and reservoirs.
Source: Portarias IEF nº 154/2011 (São Francisco), 155/2011 (East) and 156/2011 (Grande/Paranaíba)
Closed season in Goiás (state rule)
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 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.
Spawning closure (piracema) in the Araguaia River basin
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
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)
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
Spawning closure (piracema) in the Uruguay River basin
Allowed: Recreational fishing from shore, or from a boat without motor. Only handline or rod, line and hook, one gear per angler, up to 5 kg. Prohibited in floodplain lakes, within 1,500 m of dams, within 500 m of confluences, and in stretches listed in the rule (e.g., Turvo River).
Source: IN IBAMA nº 193/2008
Closed season in the rivers of Marajó Island (PA)
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
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
Border rivers MT/RO and MT/PA
Allowed: See the exceptions in Portaria 48/2007 and the state rules for each bank.
Source: Portaria IBAMA nº 48/2007
Conservation: Not on the national list (Portaria GM/MMA 1.667/2026).
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 = 0.00389, b = 3.15; FishBase). It's an average: a fat or lean fish can vary by 10% to 20%.
more about the dogtooth characin
A relative of the cachorra (Hydrolycus), the cachorra-facão has a very long, thin body like a machete and a large upturned mouth with canine teeth. It preys on small fish, chasing them in mid-water and at the surface of large rivers, bays and reservoirs. It occurs from the Orinoco and the Amazon to the Plata basin, and is common in the Pantanal and the rivers of the Paraná. For sport anglers, it is the catch that shows up when working spoons and jigs for dorado: it jumps, shakes its head and cuts thin line with its teeth.
Family: Cynodontidae · predator
fun facts
- Vulpinus comes from fox, for its long face.
- In many places it is called dourado-cachorro (dog dorado), although it is not related to the dorado.
in the kitchen
White meat with many fine bones; fried in thin steaks.
similar species
sources and references (8)
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 — Rhaphiodon vulpinus (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).
- official ICMBio/SALVE — Ficha de Rhaphiodon vulpinus (avaliação nacional do risco de extinção)National assessment by ICMBio, published in 2024. DOI verified on Crossref.
- scientific IUCN Red List — Rhaphiodon vulpinus (avaliação global: Pouco Preocupante, LC, 14/07/2020)Global assessment. Link given on the FishBase entry (Red List, version 2025-2).
- 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.Printed work; the URL is the bibliographic record on FishBase, which cites this work for the species.
- scientific Zaniboni Filho, E.; Meurer, S.; Shibatta, O. A.; Nuñer, A. P. O. (2004). Catálogo ilustrado de peixes do alto rio Uruguai. Florianópolis: Editora da UFSC; Tractebel Energia. 128 p.Printed work; the URL is the bibliographic record on 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.
- scientific Sousa, W. T. Z.; Severi, W. (2002). Desenvolvimento inicial de larvas de Rhaphiodon vulpinus Agassiz (Characiformes, Cynodontidae). Revista Brasileira de Zoologia 19(1): 85–94.DOI checked in Crossref.
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: