Sphyrna mokarran · Sphyrnidae · predator
The largest of the hammerheads, with a very tall first dorsal fin and an almost straight head. Critically Endangered in Brazil and worldwide: capture banned. If you hook one, release it right away without lifting it out of the water.
Also called: tubarão-martelo-grande, panã, cação-panã, tubarão-martelo, cação-martelo
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 great hammerhead is the largest hammerhead: it reaches 610 cm and nearly 450 kg. It lives in warm seas around the world, from the coast to islands and shelves, usually between 1 and 100 m. It prefers to hunt rays and other batoids, but also eats groupers, sea catfish, other fish, crabs, squid, lobsters and even other sharks. The female has 13 to 42 pups, of 50 to 70 cm, after about 11 months of gestation, and the animal does not mature until near 250 cm. Fishing, partly for its fins, which are highly prized in Asian trade, and bycatch have reduced the populations: it is Critically Endangered worldwide and in Brazil, and it is in Appendix II of CITES. For the angler, the job is to recognize it, not to harm it, and to release it.
Broad head, with an almost straight front edge in adults (slightly curved in juveniles) and a small notch in the middle. The first dorsal fin is very tall and curved, sickle-shaped; the second dorsal and the pelvic fins are also tall, with a deeply concave rear edge. Light grey or greyish-brown above and white below, with no marks on the fins. The scalloped hammerhead (S. lewini) has an arched front to its head, with a notch in the middle and two smaller ones on the sides; the smooth hammerhead (S. zygaena) lacks the central notch. All hammerheads are protected in Brazil.
The entire Brazilian coast, according to FishBase's latitude-based distribution. In the western Atlantic it ranges from North Carolina (USA) to Uruguay, including the Gulf of Mexico and the Caribbean; in the eastern Pacific, from southern Baja California to Peru. FishBase also cites the eastern Atlantic (the Mediterranean and from Morocco to Senegal), the Indian Ocean and the western Pacific. It is a migratory, coastal and semi-oceanic species.
Habitat: Coast and continental shelf, islands, passes and reef lagoons, usually between 1 and 100 m (can exceed 200 m). It tends to stay near the bottom and reefs between 1 and 80 m.
coast
Estimate: no known season for the Brazilian coast. FishBase treats the species as highly migratory. Legal information: capture is banned year-round in Brazil.
Any time. The daily rhythm on the Brazilian coast is poorly documented; FishBase does not indicate a preferred time.
Species of warm and subtropical waters; cold water keeps animals away from shallow areas. Effect little measured.
Not well known.
Not well known.
Not very relevant.
Not applicable at sea.
Not well known.
Rough seas prevent surf fishing and fishing from small boats.
Not well known.
From 1 to 300 m, usually down to 100 m (FishBase); near the bottom and reefs between 1 and 80 m.
accessories
If a hammerhead is hooked by chance, don't bring it out of the water: cut the line close to the mouth or remove the hook with pliers, release it right away and don't waste time on photos.
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 CR; capture banned throughout Brazil. IUCN global assessment: CR (A2bd), of 09/11/2018. Appendix II of CITES (FishBase). ICCAT prohibits retaining hammerhead sharks (except S. tiburo) in the fisheries it manages (Rec. 10-08). Hammerhead sharks of the genus Sphyrna were already protected by Portaria MMA 445/2014.
The national list (Portaria GM/MMA nº 1.667/2026) classifies the species as CR. Under Portaria GM/MMA nº 1.666/2026 (art. 3), VU, EN and CR species have full protection: catch, transport, storage, processing and trade 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
Finning is banned in Brazil (catching sharks and rays and keeping only the fins, discarding the rest of the body). The rule covers landing, transport and trade by fishing vessels: every shark or ray must arrive with its fins naturally attached to the body (partial cutting to fold them against the body is allowed); it is forbidden to carry on board an animal without fins or with loose fins, and to transfer sharks and rays between vessels. This does not authorize catching this species, which is prohibited.
In recreational sport fishing in Mexican marine waters, the limit for sharks is one animal per angler per day, which counts as five toward the total limit of ten fish (no more than five of the same species). Animals over the quota may only be released alive, in good condition for survival (catch and release), and sport-caught fish may not be sold. Sport fishing also may not take place in closed areas or seasons or in natural protected areas without the proper permits. The great hammerhead is Critically Endangered worldwide: prefer to release it.
NOM-029 is the rule for commercial-scale shark and ray fishing: it applies to holders of permits for targeted fishing of these animals and to those who catch them by accident (item 1.2), and it covers commercial fishing vessels (item 4.2.1); sport fishing has its own rule, NOM-017. It bans using only shark fins (item 4.2.1) and provides for closed seasons and closed zones, set by notice in the DOF, for targeted fishing (items 4.2.3 and 4.3.4: no targeted fishing in closed seasons, within 5 km of coral reefs, in front of river mouths and lagoons, in front of turtle nesting beaches, and near sea lion colonies). The species is in Normative Appendix A (sharks of the Pacific, the Gulf of Mexico and the Caribbean Sea).
NOM-017 (item 4.10 a) prohibits recreational fishing in closed zones and seasons, and NOM-029 (item 4.2.3) requires the authority to set closed seasons for sharks and rays by notice in the DOF; the dates change and vary by coast. On Aug 1, 2025, the Secretaría de Agricultura and Conapesca announced, for the Pacific coast, the use of sharks and rays from August 1 to April 30 (May to July are excluded, our interpretation from the announcement) and, in Tabasco, Campeche, and Yucatán, a closed season from August 1 to 29. We did not find the official notice in force in 2026: confirm the dates with Conapesca before fishing.
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.
Executive Decree 43900-MAG-MINAE (La Gaceta nº 37, of 28/02/2023) bans capture, retention on board, transshipment, landing, storage and trade of the hammerhead sharks Sphyrna lewini, S. zygaena and S. mokarran and their products. Incidental catches must be released immediately and, if possible, unharmed. The decree does not mention sport fishing and, as far as is known, makes no exception for it; the full text was not read (we checked the official record and the press), so confirm with Incopesca before fishing.
Executive Decree 9/2026 (art. 19) bans, throughout the national territory and in sport, recreational, or tourism fishing, the catch, retention, handling for recreational purposes, use, and landing of sharks and rays (subclass Elasmobranchii). If one is hooked by accident, it must be released immediately, without taking it fully out of the water and without unnecessary handling. It is also prohibited to promote them as targets in tournaments (art. 19) and to sell the catch (art. 20). The decree takes effect six months after its promulgation on June 10, 2026 (art. 40), around Dec 10, 2026, and repeals Resuelto ADM/ARAP 002/2012 (art. 39). Confirm the date with ARAP.
The official fishing guide of the Bahamas states that shark fishing is not allowed, that sharks have been protected since a 2011 amendment, that they may only be taken under special permits for very specific purposes, and that a shark hooked in any fishing must be released unharmed. The page does not cite the number of the rule.
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.
Source: Portaria GM/MMA nº 1.666/2026 (art. 3º) and nº 1.667/2026 (Annex I)
This is not catch and release: it is release of accidental catch. The great hammerhead is very sensitive to a long fight, so end the fight as quickly as possible, leave the animal in the water, cut the line flush with the hook (or remove the hook only if there is no risk) and do not hold it for a photo.
Capture and trade banned in Brazil. FishBase records use of the meat (fresh, frozen, dried and smoked), the liver oil, the leather and the fins.
Length-weight relationship W = a·Lb (a = 0.00229, b = 3.1; 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
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The seasonal weights (months), the time of day, the sensitivities (cold, pressure, moon, wind, rain, tide, strong light, murky water and noise), the water temperature range and the common size range are the app's editorial estimates, supported by FishBase and by the literature cited below, with no measurements of our own for this species. The months show when an angler may find the species near the coast, not a catch season. They are not official data and 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.
