Scalloped hammerhead shark - Sphyrna lewini


Illustration © Marc Dando

A hammerhead shark with a large body and a broadly arched, narrow-bladed head with a central notch and two smaller lateral indentations.

Light grey or bronzy above, white below, with dusky or black-tipped pectoral fins, with a dark blotch on their lower caudal fin lobe.

At birth, the shark is 1.4 to 1.8 ft [42 to 55 cm]. Males mature at 4.6 to 5.4 ft [140 to 165 cm], and females mature at approximately 7 ft [212 cm]. Its maximum length is to 12 to 13.8 ft [3.7 to 4.2 m].

These sharks prefer to be over continental and insular shelves, adjacent to deep water. They can range from the surface to more than 902.2 ft [275 m] deep, but are often close inshore and in enclosed bays and estuaries. Juveniles mainly stay inshore.

Scalloped hammerhead sharks are found world-wide in warm temperate and tropical seas. They are a migratory, schooling, coastal-pelagic, semi-oceanic species that travel within the EEZ of many coastal nations. These sharks aggregate in huge numbers, making them extremely vulnerable to commercial and illegal fishing. Many scientists believe, like the passenger pigeons, scalloped hammerhead sharks may only breed when they form large aggregations.


  • Prey – Bony fishes, sharks, rays, and invertebrates.

  • Reproduction – Scalloped hammerhead sharks have long gestation periods (8 to 12 months), and bear litters of only 14 to 26 pups.

They are seasonally migratory, and also are schooling sharks. They are a coastal-pelagic and semi-oceanic shark as well.

Scalloped Hammerheads are Endangered globally. In the Southwest Atlantic, they have declined by up to 90 percent, and those in Northwest Atlantic have declined up to 98 percent according to fisheries surveys. No regional fisheries management organization monitors take of this species, and management of international trade of scalloped hammerhead products is virtually non-existent.

In 2010, at CITES CoP15, Palau and the United States proposed three hammerhead species for Appendix II: Scalloped hammerhead - Sphyrna lewini, Great hammerhead shark - Sphyrna mokarran, and Smooth hammerhead - Sphyrna zygaena. (The three species comprise about 6 percent of identifiable fins entering Hong Kong yearly – which leads scientists to estimate that 1.3 million to 2.7 million scalloped and smooth hammerhead sharks are slaughtered annually.) Prior to CoP15, the United Nations Food and Agriculture Organization (FAO) also determined that the Scalloped hammerhead shark met the criteria for an Appendix II listing but the proposal was defeated. At CITES CoP16, the species was finally listed on Appendix II.

Like all species of sharks, approximately 10 percent of the population are adults; the remaining 90 percent are juveniles.