Scalloped hammerhead

How do you identify a scalloped hammerhead?

Like all hammerheads, it has a very flat head widened into a hammer, with the eyes at the tips. The front edge of the hammer is scalloped, and that scalloped edge gives the species its name. Medium to large, it can reach 4.30 meters and weigh over 150 kg. The back is pale gray to brown, sometimes greenish, and the belly yellow or off-white. The lower lobe of the tail and the underside of the pectoral fins are marked with black, at least in juveniles. The first dorsal fin is tall and triangular.

How does the scalloped hammerhead live?

Found in all tropical and warm temperate seas, it is the most abundant hammerhead in coastal waters, but it is also pelagic and ranges as far as river mouths. Some populations stay put, others migrate. Juveniles often form schools of more than a hundred; adults live alone or in pairs. Potentially dangerous to humans, it is in fact rarely aggressive with divers, and rather shy. The species is listed as Critically Endangered and in Appendix II of CITES.

Where and when can you dive with scalloped hammerheads?

In the Red Sea, the hammerhead schools are one of the big reasons to take a liveaboard in the south. At Daedalus, they hold in the blue off the north point from May to July. They come back from September to November, closer to the surface. At the Brothers and Elphinstone, they rise in the blue in summer, early in the morning. In the north, you will see them at Jackson Reef, in the Strait of Tiran, from June to August.

In the Pacific, Cocos Island, in Costa Rica, is their great meeting place. At Bajo Alcyone, they pass by the hundreds over the cleaning stations, with a peak from August to October. At Dirty Rock and Manuelita, the big schools rise to the cleaning stations from June to November. In Mexico, at Roca Partida, they school in the blue from November to May. To see them, move away from the walls.

In the Maldives, residents live in the Rasdhoo Madivaru channel. They school off the wall between 5:30 and 7:30 a.m., mostly from December to April. In the Philippines, a school passes off Kimud Shoal, near Malapascua, in February and March. For the biggest schools, aim for Cocos Island, from June to November.

How do you dive with scalloped hammerheads?

Hammerheads have to be earned. Go down early, settle on the edge of the plateau at 25 or 30 meters, and wait, still, watching the blue and breathing slowly. The schools come close to a calm group and move off as soon as a diver fins toward them. No flash, no chasing, and an ascent in open water under an SMB, away from the reef. The marine park boats require Advanced and fifty dives for these sites, for good reason.