Scalloped Hammerhead

About the Scalloped Hammerhead

The scalloped hammerhead is a critically endangered pelagic shark found in warm temperate and tropical seas around the world. They are usually found from the surface to around 275 m (902 ft), although they have been recorded at depths of up to 1043 m (3422 ft). Scalloped hammerheads are named after their head, which is arched and has seven indentations or notches, like a scallop.

Biology

Mature scalloped hammerheads can exceed 3 meters (9.8 ft) in length. The largest recorded specimen was 4.3 meters long. They are viviparous, meaning that embryos develop inside the uterus and are nourished through a placenta. Females give birth to between 12 and 41 live young after a gestation period of approximately 8 to 12 months. Pups are about 31–57 cm (12.2–22.4 in) long at the time of birth. Males mature at 10 years of age, and females mature at around 13–15 years and can live up to 35 years. Females return to shallow coastal nursery grounds to give birth, making these habitats particularly important for the survival of young sharks.

Behaviour

Scalloped hammerheads are migratory and move to cooler temperatures during summer. They can form very large schools of up to 700 individuals, but they often separate into smaller groups or hunt alone at night. Larger adults tend to be solitary. Their diet consists mostly of fish and cephalopods, and crustaceans, to a lesser degree. Scalloped hammerheads are not aggressive and generally shy when approached by divers.

Conservation

Despite being classified as critically endangered by the IUCN and listed in CITES Appendix II, scalloped hammerheads are often caught for meat, fins, and hides. Their fins, like those of all hammerheads, have a high fin ray count, which makes them more valuable in the shark fin trade. Young sharks are caught in great numbers during their summer migration. Despite having several pups in every litter, hammerheads are vulnerable to overfishing because they grow slowly, often taking up to 15 years to produce their first litter. Global populations have severely declined, with estimated reductions of 76.9–97.3% over 72 years. Some populations are considred extinct.

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Scalloped Hammerhead Gallery