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Great hammer in great danger!

Great hammerheads, picture by Peter Verhoog

Sphyrna mokarran is the largest of all hammerhead species of the family of Sphyrnidae, attaining a maximum length of 6.1 m (20 ft). It inhabits is tropical and warm temperate waters, ranging from coastal waters to the continental shelf.

The great hammerhead has a very wide ‘hammer’ (cephalofoil), that is almost straight and a larges tall, sickle-shaped first dorsal fin.  It is a large predator, mostly travelling on its own, feeding on a wide variety of prey, ranging from crustaceans and cephalopods, to bony fishes and to smaller sharks.

But why does the hammerhead have its hammer? It has been discovered, that sharks with wider heads have better binocular vision – all the better to track fast-moving prey like squid with far more accuracy than sharks with close-set eyes. Research also showed that hammerheads – among other sharks – have a 360-degree view of the world in the vertical plane, allowing them to simultaneously see prey above and below them. Observations of this species in the wild suggest that the cephalofoil functions to immobilize stingrays, a favored prey.

Hammer in close-up, picture by Peter Verhoog

Sadly, the great hammerhead is also in great danger. Its fins are very valuable in the fin trade. Great hammerhead populations are declining substantially worldwide, and the species has been assessed as Endangered on the Red List by the International Union for Conservation of Nature (IUCN).

Read more about the great hammerhead on Fishbase:

See a great hammerhead swim in a first peek at some of the footage made by Dutch Shark Society’s staff photographer Peter Verhoog ( for more pictures). More to come!


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