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.<\/p>\n
Carlos Robalino, a marine biologist from the Gal\u00e1pagos Islands<\/a>, trained as a shark researcher in Mexico but is now back home and working as a junior researcher at the Charles Darwin Foundation<\/a>. When we meet in March, he is one of the divers on the foundation\u2019s research expedition to Darwin and Wolf, the most northerly islands in the Gal\u00e1pagos marine reserve.<\/p>\n 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.<\/p>\n \u201cScalloped hammerheads are super-sensitive, very nervous,\u201d says Simon McKinley, an ecologist with the dive team. \u201cThe trick is to wait for the shark to pass by under me to the point where they can\u2019t possibly see me above them. Then I can dive down.\u201d<\/p>\n The plug of skin from the tip of Robalino\u2019s spear is added to a decade\u2019s worth of biopsies collected from scalloped hammerhead sharks, which visit the islands in huge numbers. The species is critically endangered, having declined by at least 80% globally, largely due to overfishing, although you would not guess it diving at Darwin and Wolf.<\/p>\n Carlos Robalino freedives with his pole-spear to take a skin sample from one of the shiver of sharks below. Photograph: Jordi Chias<\/p>\n On most dives during the 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.<\/p>\n At its peak, about 150 lion-sized scalloped hammerheads roam each hectare of sea \u2013 roughly the area of London\u2019s Trafalgar Square. There can be so many they blot out the sun.<\/p>\n Biologists using a baited camera, known as BRUVS, at Darwin Island. This remote surveying has revealed the key role of Pacific marine reserves as sharks\u2019 refuges. Photograph: P Salinas de Le\u00f3n<\/p>\n Despite their local abundance, studying scalloped hammerheads in Gal\u00e1pagos is not easy. Researchers cannot catch these sensitive sharks because the stress of being handled could kill them.<\/p>\n double quotation markBaby hammerheads, and even females when they go to give birth, are being caught \u2026 sold and consumed as ceviche Pelayo Salinas de Le\u00f3n<\/p>\n 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.<\/p>\n From twice-yearly visits to Darwin and Wolf, the team is building a long-term picture of the sharks\u2019 lives and how they are responding to changing conditions, including the heatwaves linked to El Ni\u00f1o, such as the big one forecast for 2026<\/a>.<\/p>\n More immediately, the team is tracking where these sharks go after leaving Gal\u00e1pagos. Scalloped hammerheads are not resident here but set off on long migrations<\/a>, and to learn about this part of their lives requires another diving technique.<\/p>\n Pelayo Salinas de Le\u00f3n uses a stereo-video camera to monitor fish around Darwin and Wolf Islands, which have the largest global shark biomass yet seen. Photograph: Jordi Chias<\/p>\n Away from the freedivers at Wolf Island, Pelayo Salinas de Le\u00f3n waits silently on the seabed. He 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. Like Robalino and McKinley, he uses a spear, but at the end of his is a satellite transmitter tag worth close to $2,000 (\u00a31,500).<\/p>\n Working as a senior marine ecologist at the Charles Darwin Foundation for the past 14 years, Salinas de Le\u00f3n has experimented with different methods to perfect the trick of using rebreathers to sneak up on sharks while they are swimming freely.<\/p>\n This was how he deployed a satellite tag in 2023<\/a> that tracked, for the first time, a scalloped hammerhead swimming all the way from the Gal\u00e1pagos Islands to the coast of Panama \u2013 an 800-mile (1,300km) journey \u2013 then embarking on a westerly migration of a farther 1,800 miles.<\/p>\n A researcher using a rebreather so as not to alarm the shark prepares to attach a satellite transmitter to a hammerhead visiting a reef fish cleaning station. Photograph: Mark Wong<\/p>\n Since then, he has tagged dozens more scalloped hammerheads in the archipelago. Eight out of 10 have swum to Panama<\/a>. Judging by their bulging bellies, most are probably pregnant females nearing the end of their nine-month gestation. They give birth in the sheltered waters of mangrove forests, which are in shorter supply along the mostly rocky shores of the Gal\u00e1pagos.<\/p>\n Uncovering these birthing migrations is proving crucial for conserving the species. Signals from the satellite tags deployed on the latest expedition show some of the sharks had already left Gal\u00e1pagos and were on their way to Panama at the same time that measures to protect the species were dialled up.<\/p>\n In March, Salinas de Le\u00f3n took his findings to a meeting of the Convention on the Conservation<\/a> of Migratory Species (CMS) in Brazil, where a vote was taken to decide whether to recategorise scalloped hammerhead sharks into Appendix I, giving them the highest level of protection under the convention.<\/p>\n \u201cOur science has shown that these are highly migratory sharks, their migrations are periodical, cyclical and predictable,\u201d he says, which ticks all the boxes for an endangered species getting an Appendix I listing on CMS. The vote went through and now signatory countries have to introduce laws within their waters to fully protect the species.<\/p>\n double quotation markGal\u00e1pagos represents this bubble frozen in time \u2026 the ocean of the past, where sharks are common [But] they\u2019re still dyingPelayo Salinas de Le\u00f3n<\/p>\n