Scalloped Hammerhead Sharks: Galápagos Refuge, Migratory Threats, and New International Protection

During a March 2026 research expedition to the Darwin and Wolf islands, marine biologists from the Charles Darwin Foundation used freediving and spear-mounted skin samplers to collect biopsies from dozens of scalloped hammerhead sharks that congregate in the marine reserve. At peak season the sharks can reach densities of roughly 150 individuals per hectare, creating a “bubble frozen in time” where the species appears abundant despite its global decline.

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Scalloped hammerhead sharks are classified as critically endangered, having fallen by at least 80 % worldwide, primarily because of overfishing. The Galápagos aggregation is a seasonal stop-over; satellite tags reveal that eight out of ten tagged sharks leave the archipelago for Panama, traveling 800 mi to coastal mangrove nurseries where they give birth after a nine-month gestation. After birthing, females head westward another 1 200 mi to the Pacific equatorial front, a region of high productivity that also attracts industrial fishing fleets.

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• Carlos Robalino – junior researcher, Charles Darwin Foundation, collects skin samples via freediving.

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• Simon McKinley – ecologist with the dive team, notes shark sensitivity.

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• Pelayo Salinas de León – senior marine ecologist, Charles Darwin Foundation; leads tagging and long-line monitoring.

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• Charles Darwin Foundation – coordinates research, camera surveys, and policy outreach.

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• Peak density: ~150 lion-sized sharks per hectare.

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• Tagging success: dozens of sharks tagged since 2023; 80 % migrated to Panama.

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• Migration distances: 800 mi to Panama, followed by a further 1 800 mi westward.

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• Biopsy analysis provides diet composition without invasive stomach extraction.

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At the Convention on the Conservation of Migratory Species (CMS) meeting in Brazil, signatories voted to list scalloped hammerhead sharks in Appendix I, the convention’s highest protection tier, obligating member states to enact protective legislation within their waters. Panama has recently banned international shark trade, though artisanal fishing remains permitted. The Charles Darwin Foundation is now working with Panamanian authorities to strengthen local protections for the species’ mangrove nurseries.

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Researchers observed multiple illegal longlines inside the Galápagos reserve, including one tangled around the research vessel and another hooked to Darwin’s Arch, ensnaring green turtles. “There is a free-for-all,” warned Salinas de León, highlighting the persistence of illegal and semi-industrial fishing along migration corridors. In Panama, “baby hammerheads, and even females when they go to give birth, are being caught … sold and consumed as ceviche,” underscoring continued mortality despite trade bans.

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Divers reported that while the protected aggregation offers temporary safety, sharks quickly encounter fishing gear once they depart. The team released a hammerhead caught on an artisanal longline inside the reserve and documented the high-density aggregations using underwater cameras.

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The CMS Appendix I listing mandates protection, yet enforcement varies across the extensive migration route, leaving gaps in the high seas where industrial fleets operate. No quantitative data on shark mortality rates in Panama’s artisanal fisheries were provided, indicating a need for further monitoring.

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• “Scalloped hammerheads are super-sensitive, very nervous,” — Simon McKinley, Ecologist, dive team

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• “Our science has shown that these are highly migratory sharks, their migrations are periodical, cyclical and predictable,” — Pelayo Salinas de León, Senior Marine Ecologist, Charles Darwin Foundation

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• “There is a free-for-all,” — Pelayo Salinas de León

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• “Baby hammerheads, and even females when they go to give birth, are being caught,” — Pelayo Salinas de León

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• “It is vital to implement additional management there to reduce the catch of baby sharks and migrating females.” — Pelayo Salinas de León

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• “You can have a false impression of security when you dive in Darwin and Wolf, and you see hundreds of [scalloped] hammerheads, but that’s one aggregation site that has been protected from industrial fishing since 1998,” — Pelayo Salinas de León

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The team plans to extend tagging to the Pacific equatorial front to assess whether seasonal closures or gear modifications could mitigate industrial catch. Continued collaboration with Panamanian officials aims to close protection gaps along migration corridors, while long-term monitoring will track the effectiveness of the CMS Appendix I listing and emerging management actions.

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