Alopias superciliosus · Alopiidae · predator
Shark with huge eyes that point upward and a whip-like tail nearly as long as its body, which rises to the surface at night and spends the day hundreds of metres deep. Endangered (EN) in Brazil: capture banned.
Also called: tubarão-raposa-de-olho-grande, cação-raposa-de-olho-grande
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…
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.
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.
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 bigeye thresher is a circumglobal pelagic shark of open sea and slope, which also reaches the shelf and sometimes comes close to the coast. The upper tail lobe, almost as long as the rest of the body, is used to stun fish and squid. Satellite tags on two individuals (Gulf of Mexico and Hawaii) showed a marked daily rhythm: the Gulf of Mexico animal spent 84% of the day between 300 and 500 m and 80% of the night between 10 and 100 m. That is why the species appears on shallow night longlines. The female has 2 to 4 pups per litter (usually 2). It is Endangered (EN) on the national list; globally the IUCN considers it Vulnerable (VU). Do not seek out the species.
Huge eyes that point upward, a sunken forehead with grooves on top of the head. Tail with a ribbon-shaped upper lobe, almost as long as the rest of the body. Curved pectoral fins with broad tips; the first dorsal fin sits farther back than in other threshers. Greyish-purple back, cream belly, without the white patch that extends onto the pectorals of the common thresher. The pelagic thresher has smaller eyes, a rounded forehead and straight pectoral fins with broad tips.
Circumglobal in tropical and temperate seas (FishBase: 46°N to 40°S), in open sea and at the shelf edge. In Brazil it may appear along the coast, farther from land. Among Latin American countries, FishBase records it from Mexico and the Caribbean to Chile and Uruguay.
Habitat: Open sea and slope, from the surface to more than 700 m; at night it rises near the surface and sometimes reaches shallow water close to the coast.
coast
Estimate: no well-documented season in Brazil; the weights are neutral and the species is in open sea year-round. Capture is banned all year.
Nighttime. It rises near the surface at night (10 to 100 m) and stays deep by day (300 to 500 m), according to two satellite-tagged individuals (Weng and Block, 2004).
It spends the day in cold water (6 to 12 °C) and rises at night to water of 20 to 26 °C.
Little known effect.
No known effect; the daily rhythm seems guided by light.
Not very relevant.
Not applicable at sea.
Little known; the species is not often seen up close.
Rough seas end trips offshore.
No relevant tide in the ocean; currents and temperature fronts matter.
Deep by day (300 to 500 m) and shallow at night (10 to 100 m).
accessories
If a thresher shark bites by accident at night, release it beside the boat, in the water, cutting the line flush with the hook. Watch the tail: it is long and strong.
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: On the national list of threatened species as EN (already on the previous list). Global: Vulnerable (VU, assessed 06/11/2018 by the IUCN). Since 2017 all thresher sharks have been in Appendix II of CITES.
The national list (Portaria GM/MMA nº 1.667/2026) classifies the species as EN. Under Portaria GM/MMA nº 1.666/2026 (art. 3), species listed as VU, EN and CR have full protection: capture, transport, storage, processing and sale are banned. If you hook one by accident, release it right away, with minimal handling.
Source: Portaria GM/MMA nº 1.666/2026, art. 3º, and Portaria GM/MMA nº 1.667/2026
In Brazil, finning is banned: cutting off the fins and discarding the rest of the body. The rule covers landing, transport, and trade by fishing vessels: every shark or ray must arrive whole, with its fins naturally attached to the body (partially folding them against the body is allowed); carrying an animal aboard without fins or with loose fins, and transferring sharks and rays between vessels, is prohibited. This does not authorize catching this species, which is banned.
ICCAT Recommendation 09-07 requires member countries to prohibit, in any fishery, retaining on board, transshipping, landing, storing, selling or offering for sale the bigeye thresher (Alopias superciliosus), whole or in parts. The recommendation makes an exception for an artisanal coastal fishery in Mexico, catching fewer than 110 fish. It is an obligation for countries, not a rule for the angler: how each country applies it to sport fishing varies, and we did not check each country's domestic rules or the current ICCAT compendium. When in doubt, release it in the water.
Source: ICCAT Recommendation 09-07 (International Commission for the Conservation of Atlantic Tunas)
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.
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.
Law 9 of 2006 bans finning in Panama's jurisdictional waters. The law's definition of shark fishing covers directed or incidental catch by artisanal, commercial, industrial and sport vessels. The fine for artisanal fishing reaches 1,000 balboas, without prejudice to criminal liability. In the sources we checked, we did not find a specific Panamanian rule on retention or release for sport anglers.
Law 20.525 (2011) added art. 5 bis to the General Law on Fisheries and Aquaculture: it is forbidden to cut the fins of any shark on board fishing vessels or during transshipment, and landing must be done with the fins fully or partially attached to the body. A loose fin without the corresponding trunk on board is presumed to be an offense. The fine for the vessel owner ranges from 50 to 500 UTM. We did not verify a specific Chilean rule on shark retention in marine recreational fishing.
This is not catch and release: it is release of accidental catch. Do not bring the shark aboard; keep it beside the boat, in the water, and cut the line as close to the hook as possible. Do not hold it by the long tail and do not take photos.
Capture and trade banned in Brazil. In other countries the meat is sold fresh, salted and dried, and the liver oil and leather are used (FishBase), but the species is threatened: release it.
Length-weight relationship W = a·Lb (a = 0.01122, b = 2.91; FishBase (relação peso-comprimento bayesiana, estimativa da própria espécie)). It's an average: a fat or lean fish can vary by 10% to 20%.
estimated weight
—
The seasonal 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 field experience from anglers and guides. The water temperature range and the common size range are also editorial estimates, supported by FishBase. The months show when an angler usually finds the species, not a catch season. They are not official data or measurements made for this species, and they may vary by region and year. Legal rules appear in the rules section, with the norm and a link.
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:
Your location is saved only on this device and feeds the forecast, the map and the "today" on the home page.
