Sphyrna zygaena
Hammerhead with a broad, curved head and no notch in the middle, from temperate and warm waters. Critically Endangered in Brazil (Vulnerable worldwide): capture banned. In Argentina and Ecuador, release is mandatory.
Also called: tubarão-martelo-liso, tubarão-martelo, cação-martelo, cação-cambeba, cação-cornudo, pata
The smooth hammerhead is a large hammerhead from temperate to warm seas around the world, from the coast to the open sea, and usually stays in the top 20 m. It migrates north in summer, and juveniles gather in schools of hundreds of animals. It eats small sharks and rays, bony fish, shrimp, crabs, barnacles and cephalopods. The female has 20 to 50 pups, of 50 to 60 cm, after 10 to 11 months of gestation. In Ecuador, 90.53% of artisanal landings were newborn and juvenile animals, which harms population renewal. It is Vulnerable worldwide (IUCN, 2018), but Critically Endangered in Brazil, and it is in Appendix II of CITES. For the angler, the job is to recognize it and release it.
Broad head, curved at the front, without the central notch of the scalloped hammerhead (or the great hammerhead), but with marked side indentations. Short snout and a wide, arched mouth. The first dorsal is moderately tall; the second dorsal and pelvic fins are low. Olive-grey or dark grey above, white below, with the underside of the pectoral tips darkened. The scalloped hammerhead has three notches on the front; the great hammerhead has a very tall first dorsal. All hammerheads are protected in Brazil.
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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.
The entire Brazilian coast, according to FishBase's latitude-based distribution. FishBase describes the species as circumglobal, from temperate to tropical seas. In Latin America it ranges from the Caribbean and the Gulf of Mexico to Uruguay and Argentina in the Atlantic, and from Mexico to Chile in the Pacific.
Habitat: Coast and open sea, over continental and island shelves. It usually swims in the top 20 m, often associated with the bottom between 1 and 139 m; juveniles form large groups.
coast
Estimate: no known season for fishing. FishBase says the species migrates north in summer; in Brazil there is no season, because capture is banned all year.
Any time. The daily rhythm is poorly documented; juveniles stay in large groups, with no time indicated by FishBase.
Species of temperate to warm waters; tolerates colder water than the great hammerhead, but migrates with the temperature. 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 0 to 200 m, usually down to 20 m (FishBase); juveniles near the coast.
accessories
If a hammerhead bites by accident, do not lift it out of the water: cut the line flush with the mouth or remove the hook with pliers, release it right away and do not waste time on photos. In Argentina and Ecuador, where release is mandatory, the same applies: hammerheads die easily after a long fight.
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: VU (A2bd), of 08/11/2018. Appendices II of CITES and CMS (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.
On the sea coast of Buenos Aires Province (and in the Río de la Plata, Bahía Blanca and Mar Chiquita estuaries), large coastal sharks, including hammerheads (Sphyrna sp.), are 'targeted fishing with restrictions': release is mandatory and killing is banned, including as incidental catch (arts. 6º, 14). Gear: one rod per angler on a boat and two from shore, single-hook rig (tandem hooks are banned), a curved hook such as Mustad 39960 BL or a degradable Mustad 3406 in 12/0 or 14/0 (or similar), with the barb flattened; the Mustad Tartuna is banned (art. 14). A stop float 25 cm above the hook on bottom lines and nylon line of at least 0.70 mm are recommended (art. 15). A gaff is banned (art. 7º). If there is no risk, remove the hook from the mouth; otherwise cut the line near the hook, avoiding taking the shark out of the water (art. 19). Selling sport-caught fish is banned (art. 24).
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 smooth hammerhead is Vulnerable 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.
Ministerial Agreement 116/2013 (art. 1º, b) bans, on sport and recreational fishing vessels, retaining on board, transshipping, landing, storing and selling the hammerhead sharks 'cachuda roja' (S. lewini) and 'cachuda blanca' (S. zygaena), whole or in parts. When they reach the side of the vessel, they must be released immediately and, as far as possible, unharmed. The text has been in force since its signing in Manta on 26/08/2013; its current validity was not rechecked.
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. Hammerheads suffer greatly in a long fight: end it as soon as possible, leave the animal in the water, cut the line near the mouth and do not hold it for a photo.
Capture and trade banned in Brazil. FishBase records use of the meat (fresh, dried and perhaps smoked), the liver oil, the leather and the fins, and that the species is used in Chinese medicine; FishBase also says it can cause poisoning.
Length-weight relationship W = a·Lb (a = 0.00398, b = 3.09; 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.
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