Galápagos Marine Reserve: A Haven for Critically Endangered Scalloped Hammerhead Sharks

The Galápagos: A Shark Sanctuary Under Threat

The unmistakable fluted T-shape of a scalloped hammerhead shark slides by, followed by a diver holding his breath and a metal spear like an extra-long snooker cue. The spear hits the fish behind its dorsal fin and the 2-metre shark darts away, disgruntled but otherwise unharmed. This scene, captured by researchers from the Charles Darwin Foundation, represents one of the most important conservation efforts for a species that has declined by at least 80% globally due to overfishing.

Innovative Research Methods in Shark Conservation

Carlos Robalino, a marine biologist from the Galápagos Islands, is part of the foundation's research expedition to Darwin and Wolf, the most northerly islands in the Galápagos marine reserve. For three or four hours each morning and afternoon, Robalino is in the sea, honing his freediving skills so he can get close enough to the sharks to take samples of their skin. "Scalloped hammerheads are super-sensitive, very nervous," says Simon McKinley, an ecologist with the dive team. "The trick is to wait for the shark to pass by under me to the point where they can't possibly see me above them. Then I can dive down."

The Unprecedented Abundance of Hammerheads in Galápagos

Despite being critically endangered globally, the Galápagos hosts an extraordinary population of scalloped hammerheads. On most dives during the research trip, dozens of the sharks swim by. Later in the year, in the cold season when there is more food in the seas around Darwin and Wolf, more sharks migrate to the archipelago and the population quadruples. At its peak, about 150 lion-sized scalloped hammerheads roam each hectare of sea – roughly the area of London's Trafalgar Square. There can be so many they blot out the sun.

Challenges in Protecting a Globally Endangered Species

Despite their local abundance, studying scalloped hammerheads in Galápagos is not easy. Researchers cannot catch these sensitive sharks because the stress of being handled could kill them. The foundation team has developed less invasive techniques, including deploying underwater cameras to monitor shark numbers. Chemical analysis of skin biopsies shows, among other things, what the sharks are eating without needing to cut open their stomachs to see the contents. However, challenges remain: "Baby hammerheads, and even females when they go to give birth, are being caught... sold and consumed as ceviche," according to Pelayo Salinas de León.

Tracking Shark Migrations Across the Pacific

The research team is tracking where these sharks go after leaving Galápagos. Scalloped hammerheads are not resident here but set off on long migrations, and to learn about this part of their lives requires specialized diving techniques. Pelayo Salinas de León uses a closed-circuit rebreather, a device which recycles his exhalations, removes carbon dioxide and adds more oxygen as needed, so he can dive for hours in bubble-free tranquillity without scaring off the hammerheads. He attaches satellite transmitter tags worth close to $2,000 to track their movements across the Pacific Ocean.

Future Conservation Challenges in a Changing Climate

From twice-yearly visits to Darwin and Wolf, the team is building a long-term picture of the sharks' lives and how they are responding to changing conditions, including the heatwaves linked to El Niño, such as the big one forecast for 2026. These climate events could significantly impact the delicate marine ecosystem that supports the hammerhead population. The research being conducted in the Galápagos provides crucial data that will help conservationists develop strategies to protect these magnificent creatures both within the marine reserve and along their extensive migration routes.