Smooth hammerhead shark - Sphyrna zygaena
Body structure, features & anatomy
The smooth hammerhead shark Sphyrna zygaena is a large hammerhead with a broad head expanded sideways. WoRMS lists the name as accepted; on Haitauchen it sits within Selachii, Galeomorphi, Carcharhiniformes, Sphyrnidae and the genus Sphyrna.
Shark-References records the original description by Linnaeus in 1758 and the common names. The key field mark is the evenly curved, smooth front edge of the head: unlike the scalloped hammerhead, it lacks a central notch, while the body is large, streamlined and gray to olive-brown above.
Smooth head, large outline
Adults can reach several meters and belong among the large hammerheads. The eyes sit at the outer ends of the head, the mouth is underneath, and the first dorsal fin is distinctly falcate. For photographs, head outline, body size, dorsal-fin shape and locality should be read together.
Distribution & habitat
FishBase describes the smooth hammerhead as an inshore to offshore shark over continental and insular shelves. It is coastal-pelagic to semi-oceanic, can also be bottom associated, and young animals may form large regional aggregations while seasonal movements often follow temperature and currents.
The range is unusually broad: the species occurs in tropical, subtropical and temperate seas, reaching cooler latitudes more than many other hammerheads. Records involve coasts, shelf edges, island slopes, open water and occasionally very shallow bays or estuarine areas.
Coasts, shelves and open water
For divers this is not a simple target species. Encounters depend strongly on region, season and local migrations; young animals may appear in shallower coastal areas, while large adults are often more mobile and less site-faithful. No range map was inserted into the detail page.
Life history, diet & reproduction
The ICCAT profile describes Sphyrna zygaena as a semipelagic species recorded from the surface to 200 m, with age-class segregation and important coastal areas for young animals. Adults are powerful migrants, while juveniles may use more sheltered areas or regional groups.
Diet includes bony fishes, cephalopods, crustaceans and other cartilaginous fishes. The NOAA Fisheries Bulletin paper from northern Peru shows that local prey composition and shark size matter: smooth hammerheads can hunt opportunistically and may hold a high trophic role in some areas.
Hunting, migration and young
The species is live-bearing. Females produce relatively large litters after a long gestation; about 20 to 50 pups are often reported. Newborns are active small hammerheads, but their coastal nursery use makes them especially exposed to nets and local fishing pressure.
Threats & conservation status
The IUCN Red List assesses Sphyrna zygaena globally as Vulnerable. Bycatch and directed catch in coastal and offshore fisheries, catch statistics that mix hammerhead species, and strong demand for large fins are central concerns.
CITES places the smooth hammerhead under international Appendix-II shark trade rules. That is not an automatic catch ban, but trade must be traceable and supported by non-detriment findings. Without reliable species identification, those rules are weak in practice.
Fisheries and trade
Conservation therefore needs several layers: less bycatch in longlines, gillnets and trawls, no removal from important juvenile habitats, better species-level reporting and stronger control of the fin trade. A wide-ranging species can otherwise slip between national responsibilities.
Smooth hammerhead shark & humans
The Florida Museum describes the smooth hammerhead as a large, seasonally migrating coastal shark that may also use very shallow areas. It is not a typical problem shark for people, but its size, strength and possible curiosity mean encounters should stay calm and spacious.
The NOAA Fisheries report summarizes how the species appears in many fisheries as target catch or bycatch. For people, fishing pressure matters more than direct risk in the water: longlines, nets, beach-protection gear and fin trade shape the species’ future.
Respectful encounters
When diving, do not chase, circle or support baited photo setups. Anyone who sees a smooth hammerhead should record place, date, depth and behavior, because reliable sightings help with a shark that migrates widely and is often grouped with other hammerheads in catch data.
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