A shark with visible teeth and a fierce look, but slow and not very aggressive. Critically Endangered in Brazil: catch prohibited. In Argentina it is the escalandrún, caught only with release at San Blas.
Also called: mangona, cação-mangona, magonga, mangonga, cação-de-areia, escalandrún
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
slide your finger or mouse over the chart to see each hour
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 sand tiger shark
overview
who is the sand tiger shark
The mangona, the escalandrún of Argentines, is a coastal shark of temperate and warm waters, with a bulky body and long, slender teeth always showing. It swims slowly near the bottom, over beaches, bays, rocky shores and shipwrecks, and hunts fish, rays and squid, mostly at night. In the South Atlantic it migrates between southern Brazil, Uruguay and northern Patagonia in Argentina, where it mates in summer, in Anegada Bay and at San Blas. It has one of the lowest reproductive rates of any shark: only two pups per pregnancy. Fishing has reduced its populations, and it is now Critically Endangered in Brazil and worldwide. In Buenos Aires Province and Río Negro it is a sport fish with mandatory release.
fun facts
It gulps air at the surface and stores it in its stomach to float motionless in midwater.
The first embryo to develop in each uterus eats the others: only two pups are born per pregnancy.
Despite its frightening teeth, it is slow and calm around divers.
how to recognize it
identification
Thick, bulky body, gray-brown to bronze, with reddish or dark spots scattered over the rear half, pale belly. Conical, flattened snout, long slender teeth like nails, visible with the mouth closed. The two dorsal fins are nearly the same size, and the first sits well behind the pectoral fins. Tail with a short lower lobe. The Portuguese name "tubarão-touro" is used for this one and for the bull shark; check the scientific name.
In Brazil, from the Southeast to the South, now rare. In the southwestern South Atlantic it migrates between southern Brazil, Uruguay and northern Patagonia in Argentina (Anegada Bay and San Blas Bay in Buenos Aires Province, and San Matías Gulf in Río Negro). In the western Atlantic it ranges from the Gulf of Maine to Argentina.
Habitat: Beaches, bays, rocky shores, shoals and shipwrecks, near the bottom; tidal channels in the bays of northern Patagonia.
coast
Southeast CoastSouth Coastcoastalshelf
states
Rio de Janeiro, São Paulo, Paraná, Santa Catarina, Rio Grande do Sul
calendar and clock
when to fish
best season
time of yearbest: Dec–Mar
JanFebSeaAprMayJunJulAugSepOctNovDec
Estimate: in northern Argentine Patagonia (San Blas, Anegada Bay) the escalandrún appears in summer, from December to March, the mating season. In Brazil it is rare, with no well-defined season for anglers.
best time of day
Night and twilight. Most active at night and at dusk; by day it stays still near the bottom, in groups.
weather, water and behavior
what affects the sand tiger shark
sensitivity The little bars show how much each factor affects this species. Five full: it feels it a lot.
cold and cold fronts
Tolerates temperate water; follows warmer water during migrations.
atmospheric pressure
Cold fronts bring rough seas and cool the shallow water.
moon
Spring tides move the channels of the Patagonian bays.
rain
Not very relevant.
water level
Not applicable at sea.
noise
Slow and not very aggressive, but it moves away from constant noise.
wind
Strong wind and rough seas prevent fishing from the beach and from boats.
tide
In the San Blas bays, fishing is productive with the tide running through the channels.
depth
From the shallows of the beaches to about 200 m; usually found between 15 and 25 m.
beach: 13' to 15' for heavy casting; boat: 6' to 7', 50 to 80 lb
spinning / baitcasting reel
large casting spinning reel or 4/0 to 6/0 baitcaster with plenty of line
line
monofilament of at least 0.70 mm (required in Buenos Aires) or 80 lb braided line with a monofilament leader
leader
1 to 1.5 m wire leader plus 2 to 3 m of heavy monofilament
hook
circle hook 12/0 to 14/0 with the barb flattened; single hook only, no tandem rigs
natural baits
cut bait or half a fish (mullet, pescadilla, mackerel) on the bottom, where catch and release is permitted
accessories
stopper float 25 cm above the hook so it can't be swallowed
cutting pliers for steel cable
long hook remover
luvas
tip from an angler
In Brazil, catch is prohibited: if hooked by chance, release it in the water. At San Blas and San Matías Gulf, release is mandatory: use a stopper float, don't let the shark swallow the bait, keep the fight short, and release it in shallow water without dragging it across the sand.
what the law says
rules for the sand tiger 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, December 7, 2020).
Threatened species (CR): catch prohibited in Brazil
catching, transport, holding and trade prohibited
The mangona (Carcharias taurus) 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 escalandrún (Carcharias taurus) 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.
commercial or sport extraction not permittedconfirm with the agency
In 2021 Colombia stopped considering sharks and marine rays a fishery resource and began treating them as a hydrobiological resource; the recitals of Decree 281/2021 state that they may not be extracted for commercial or sport purposes, and the decree created an environmental protection plan. Later AUNAP rules dealt with incidental catch in artisanal fishing; we did not check the consolidated text. When in doubt, release it into the water.
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 (Buenos Aires, Río Negro): leave the shark in the water or at the shore, head pointing to sea, remove the hook with a dehooker or cut the line close to the mouth, don't touch the gills, and release it within a few minutes.
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 = 0.00741, b = 2.99; FishBase (estimativa bayesiana para a família e o formato do corpo, 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.
