Wild Hammerhead Shark Conservation: Behaviour, Threats, and Marine Welfare

Hammerhead sharks are among the ocean's most distinctive and ecologically important predators, yet face severe population declines from targeted fishing, finning, and bycatch. Their welfare as sentient animals deserves consideration alongside their conservation status.

Key Facts

Nine hammerhead species exist (family Sphyrnidae), ranging from the great hammerhead (Sphyrna mokarran, reaching 6m) to the small winghead shark; all are characterised by their distinctive cephalofoil (flattened, hammer-shaped head) that enhances sensory function
Great and scalloped hammerheads (S. lewini) are classified as Critically Endangered on the IUCN Red List; smooth hammerheads (S. zygaena) are Vulnerable — across the family, population declines of 50-98% have been documented
Hammerhead fins are among the most valuable in the shark fin trade; their large, distinctive fins command premium prices in Asian markets, making them disproportionately targeted by the finning industry
Bycatch in tuna longline fisheries is a major additional mortality source — hammerheads, like many sharks, have very high post-release mortality when caught on longlines due to physiological stress during long capture periods
The expanded cephalofoil contains an extraordinarily dense array of electroreceptors (ampullae of Lorenzini) that enable detection of the electrical fields of buried prey — a sensory capability with no parallel in other vertebrates
Hammerheads are highly social: scalloped hammerheads form enormous daytime aggregations of hundreds to thousands of individuals at seamounts, a behaviour with likely social and thermoregulatory functions
Shark finning — removing fins and discarding the body at sea — has been banned in many countries but continues illegally; whole-shark fishing with fins attached is a more enforceable alternative to outright finning bans
Marine protected areas (MPAs) at key aggregation sites (Cocos Island, Galápagos, Malpelo) provide refuge from fishing pressure and have been associated with local population recovery

Welfare Considerations

Hammerhead welfare considerations include both the mode of death in fisheries and the treatment of animals prior to death. Shark finning — cutting off fins while the shark is alive and discarding the body — causes drowning and blood loss in an air-exposed, immobile animal: a prolonged and inhumane death. Bycatch on longlines involves hours of struggling against hooks, exhaustion, and hypoxia before the animal is retrieved — post-release mortality even for released animals is high because the physiological stress of capture exceeds sharks' capacity for recovery. As cartilaginous fish, sharks have nervous systems capable of nociception and stress responses consistent with pain and fear experiences. The welfare case for reducing shark mortality in fisheries is therefore not purely ecological but includes individual welfare dimensions. Rapid, humane killing methods for commercially harvested sharks exist and should be required standards — the current norm of sharks slowly asphyxiating on deck is inhumane and unnecessary.

What You Can Do

Avoid shark fin soup and shark fin products — consumer choice directly reduces demand for the fins that drive targeted hammerhead fishing
Support Shark Allies, WildAid, and WWF's shark conservation programmes working on finning bans, trade legislation, and fisheries reform
Choose MSC-certified seafood and ask restaurants about their shark and ray bycatch reduction policies — consumer pressure on seafood supply chains drives fisheries management improvements
Support MPAs at known hammerhead aggregation sites — locations like the Galápagos and Cocos Island Marine Reserve provide critical refuge for recovering populations
Advocate for CITES Appendix II listings for additional hammerhead species — this requires countries to demonstrate sustainable trade in shark products before export permits are issued
Support research into bycatch reduction devices (BRDs) and hook types that reduce hammerhead and other elasmobranch capture in longline and gillnet fisheries