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a close up of a fish

Hammerhead shark
(Sphyrna zygaena)

All hammerhead shark species are quite bizarre-looking and therefore easy to identify. In most species, the snout is extremely widened giving their head a T-shape, resembling that of a hammer. The eyes are positioned on either tips of the T, allowing the animals full 360-degree vision.

The snout also contains highly sensitive sensory pores which act as one single sensory organ, capable of registering electric impulses. This enables hammerheads to efficiently detect the electric fields of their prey.

Hammerheads circle close to the bottom of the sea and with the help of these sensors, they can find prey-fish hiding – particularly at night – in the substrate. Hammerheads mostly live in groups (schools), which is highly unusual for a shark species.

Even though based on their size, they are considered dangerous to humans, attacks are still very rare. In the waters of Madeira, we have occasionally observed hammerheads resting on the surface. They are usually very shy and quickly dive away.

General information

Further names:  Tuberão martelo

Size of adult animals: 250 – 350 cm

Prey: They feed on small sharks and rays, fish, shrimps, crabs, cephalopods.

Life cycle and behaviour: These animals reach sexual maturity at a length of about 300 cm. Females give birth to approx. 30 to 40 live pups which are sustained in the womb by a placenta-like structure that develops from the yolk sac. This means that hammerheads belong to the group of viviparous fish, all of which give birth to live young. 

Habitat and range: Occurring globally in tropical and subtropical seas, both in coastal areas and in the open ocean. They usually swim in a depth of 0 to 20 m but can also dive deeper, to about 200 m.

Distinctive features: Characteristically wide head; olive-grey or dark grey back; white belly; the fins have a darker or black tip.

Taxonomy: Class: Chondrichthyes (Cartilaginous fish); Subclass: Elasmobranchii (Sharks and rays); Family: Sphyrnidae (Hammerhead sharks)

Threats: These sharks often die in fishing nets and are even actively hunted in some countries (for shark-fin soup). Their meat is considered a local delicacy, their liver is rich in oil, and their skin is processed into sanding materials. Some body parts are also used in traditional Chinese medicine.

Threats: Naval sonar exercises, pollution, bycatch and hunting amongst other. classified as Data Deficient by IUCN.

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