A slender shark with a translucent snout, migrating between southern Brazil and Argentina. Critically Endangered in Brazil. In Argentina it is the cazón, with mandatory release in sport fishing.
Also called: cação-bico-doce, cação-bico-de-cristal, bico-de-cristal, tubarão-vitamínico, cazón
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.
location
Sample location: choose yours to see the forecast for where you fish.
period
Reading the weather across 3 global models and 31 simulations…
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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
tap or drag on the chart to read each hour · on a keyboard, arrow keys
see hour-by-hour table
why this index at —?
next 7 days
choose the day
chart: bar height = day's index · line = variation between models · striped = trend · fainter = less confidence
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 school shark
overview
who is the school shark
The cação-bico-doce, also called bico-de-cristal, lives in temperate waters around the world, from the coast to the shelf. In the South Atlantic it forms a single population that moves between southern Brazil, Uruguay and Argentina, where pregnant females appear in coastal bays. It grows slowly, can live more than 50 years, and females have pups only every few years. It was heavily fished in the 20th century, including for its vitamin A-rich liver oil, and local fisheries nearly disappeared. Today it is Critically Endangered in Brazil and worldwide. In Argentina, the cazón is fished from the beach and from boats, always with mandatory release.
fun facts
The name 'tiburón vitamínico' (vitamin shark) comes from fishing for its liver oil, rich in vitamin A, in the mid-20th century.
It can live past 50 years.
In the South Atlantic it is a single population, which migrates between Brazil, Uruguay and Argentina.
how to recognize it
identification
Slender body, blue-gray to brown on the back and white on the belly, without spots. Long, pointed, translucent snout, large oval eyes. Small second dorsal fin, about the size of the anal fin. Its hallmark is the tail: the upper lobe ends in a large, distinct lobe, almost a second tail. The cação-malhado (Mustelus) has two dorsal fins of nearly equal size; the name "bico-doce" is also used for Mustelus sharks and for the blue shark.
In Brazil, from the south to São Paulo, mainly in Rio Grande do Sul. In the southwestern South Atlantic, a single population between southern Brazil, Uruguay and Argentina (Buenos Aires coast, Anegada Bay, northern Patagonian gulfs). Also in the Pacific, in Chile, Peru, Ecuador and Mexico.
Habitat: Continental shelf and coastal waters, close to the bottom; shallow bays during the birthing season.
coast
Southeast CoastSouth Coastcoastalshelf
states
São Paulo, Paraná, Santa Catarina, Rio Grande do Sul
calendar and clock
when to fish
best season
time of yearbest: Nov–Feb
JanFebSeaAprMayJunJulAugSepOctNovDec
Estimate: in Argentina it appears close to shore in spring and summer; in southern Brazil it is more present in the cold months, following the population's migration. Biological information: in Brazil, catch is prohibited year-round.
best time of day
Night and twilight. From the beach, the cazón bites more in late afternoon and at night.
weather, water and behavior
what affects the school shark
sensitivity The little bars show how much each factor affects this species. Five full: it feels it a lot.
cold and cold fronts
A temperate and cold-water species; migrates with temperature.
atmospheric pressure
Cold fronts bring rough seas that end beach fishing.
moon
Dark nights often produce more from the beach.
rain
Not very relevant.
water level
Not applicable at sea.
noise
Not well known.
wind
Rough seas prevent beach fishing.
tide
A rising tide at night is the classic beach combination.
depth
Usually from 2 to about 470 m; close to shore in the Argentine summer.
monofilament of at least 0.70 mm (required in Buenos Aires for sharks)
leader
wire leader 50 cm to 1 m
hook
circle hook 12/0 to 14/0 with the barb flattened (required in Buenos Aires); single hook only
natural baits
fillet or cut of fish (pescadilla, mullet, mackerel), where catch and release is permitted
accessories
stopper float 25 cm above the hook
cutting pliers
long hook remover
tip from an angler
In Brazil, catch is prohibited. In Argentina, release is mandatory: the cazón is delicate, so release it quickly, without taking it out of the water.
what the law says
rules for the school shark
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: Catch prohibited throughout Brazil. Global: Critically Endangered (IUCN, February 14, 2020).
Threatened species (CR): catch prohibited in Brazil
catching, transport, holding and trade prohibited
The cação-bico-doce (Galeorhinus galeus) is on the national list as Critically Endangered (CR) (it was already on the previous list, Portaria MMA 148/2022). Ministerial Ordinance GM/MMA 1.666/2026 (art. 3) prohibits catch, transport, storage, possession, processing and trade throughout Brazil. Anyone who hooks one by chance must release it alive immediately (art. 3, § 4). The rule does not authorize targeted fishing, even with release: in Brazil, do not seek this species.
Finning prohibited: shark only whole, with its fins
fins naturally attached to the body
In Brazil, finning is prohibited (cutting off the fins and discarding the body). Every shark or ray landed must arrive with its fins attached to the body; it is prohibited to carry on board an animal without fins or with loose fins, and to transfer sharks between vessels. It applies to any shark that may be kept.
Buenos Aires (AR): mandatory release of large coastal sharks
mandatory release; killing prohibited
On the Buenos Aires Province coast (and in the Plata, Bahía Blanca and Mar Chiquita estuaries), escalandrún, bacota, gatopardo, cazón and hammerheads are "reserved directed fishing": release is mandatory, and killing is prohibited even for incidental catch. Gear rules: one rod per angler on a boat and two from shore; single-hook rigs only (tandem rigs prohibited); circle or biodegradable hook 12/0 to 14/0 with the barb flattened; a stopper float 25 cm above the hook is recommended on bottom lines, along with nylon line of at least 0.70 mm. Gaffs are prohibited. Remove the hook only if there is no risk; otherwise cut the line close to the hook, avoiding lifting the shark out of the water. From Pehuén-Có to the mouth of the Río Negro (including the Bahía Blanca estuary, Anegada Bay and San Blas), a permanent closed season also applies to artisanal and commercial fishing for escalandrún, bacota, gatopardo and cazón (Disposition 55/2008).
Río Negro (AR): mandatory release (Law 5.706/2023)
mandatory release; killing prohibited
In Río Negro Province marine sport fishing (San Matías Gulf, El Cóndor, Bahía Creek), the cazón (Galeorhinus galeus) is under a special protection regime: killing during capture is prohibited and release is mandatory. In boat fishing targeting sharks: one hook per line (tandem rigs and tartuna-type galvanized hooks prohibited), a "J" hook with the barb filed or flattened, or a circle hook. A specimen on board only with scientific authorization.
1 specimen per angler per day (counts as 5 against the quota of 10)
In recreational sport fishing in Mexican saltwaters, the limit for sharks is one specimen per angler per day, which counts as five toward the total limit of ten fish. Fish caught in sport fishing may not be sold. Catch and release does not count toward the limit: prefer releasing.
North CoastNortheast CoastSoutheast CoastSouth Coast
Many sharks and rays are on the national list (CR, EN or VU), with catching, keeping and transport prohibited, including those listed here. Species added to the list only in 2026 follow the 180-day deadline (until about Oct 25, 2026). If unsure of the species, release it.
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.
In Brazil, only release of incidental catch. Where release is mandatory: leave it in the water, cut the line close to the hook if it does not come out easily, and release it within a few minutes, without touching the gills.
in the kitchen
Catch and trade prohibited in Brazil; in Argentina, killing is prohibited in sport fishing.
calculator
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.00479, b = 2.99; FishBase (estimativa bayesiana para a espécie, comprimento total)). 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 seasonal weights (months), time of day and 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 field experience of anglers and guides. The months indicate the time of year when the angler usually finds the species near the coast, not a catch season. They are not official data or measurements made for this species and may vary by region and year. Legal rules appear in the rules section, with the regulation and link.
officialPortaria GM/MMA nº 1.666, de 27 de abril de 2026 — regras de proteção das espécies ameaçadas da lista nacionalArt. 3: full protection for VU, EN and CR species; § 4: incidental catch with immediate release of the live animal. The 180-day transition rule for species newly added to the list was verified from official summaries (Fiperj) and technical sources; the DOU (Brazil's Official Gazette) page did not open during verification.
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.
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:
where are you going fishing?
Your location is saved only on this device and feeds the forecast, the map and the "today" on the home page.
