
Scalloped hammerhead Sphyrna lewini
The sanctuary's flagship species. Malpelo is described as one of the world's important hammerhead breeding areas. Males mature at roughly 1.5–1.8 m, females near 2.5 m, and the species can reach about 4.3 m. The IUCN lists it as Critically Endangered, mainly from overfishing for fins.
Key marks: The head is flattened into a hammer with a scalloped front edge: a notch in the middle and a shallow scallop either side of it. Eyes at the very tips. Tall, strongly curved first dorsal fin and a small second dorsal. Bronze-grey above, pale below. In open water you usually get the silhouette from below before any colour, so go by the shape of the head.
At Malpelo: Present year-round and densest December to April. Reliability is very high, at 18–35 m. Schools of 200–500 have been reported at El Bajo del Monstruo. La Nevera is considered the best site, because of its cleaning stations. DAN reports four passes of 20 to 50 animals there at about 24 m, and hammerheads at El Bajón at about 30 m. Shallow cleaning-station visits are more likely in winter. In June, one diver saw schools of up to about 12, far off in the blue water and moving deeper as the water warmed (Interceptor121).
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