Hammerhead shark (Introduction – biology – threats) – Video


Video credit: Hani Elmalky (USA)  – Review: Abdel Rahman El Gamal

This video was taken in the Monterey Bay Aquarium during June 2012 showing the hammerhead shark cruising amongst a large population of Pacific sardines and other fish species.  The review focuses on the leading species in this exhibition which is the hammerhead shark.

Introduction: The hammerhead sharks belong to the genus Sphyrna in the family Sphyrnidae. The small and medium size species are known to form schools of more than 100 during the day while they become solitary in the evening. The average life span in the wild is 20 to 30 years and depending on the species, their size can reach up to 6 m in length and about 450 kg in weight. Because the liver of a Hammerhead shark is rich with oil which has a lower density than water, the fish tend to float in the water rather than swim.

Hammerheads are found worldwide in warm tropical and subtropical waters along coastlines and continental shelves. Most hammerhead species are considered harmless to humans.

Description: The shape of the head is a distinct feature of hammerhead sharks. Their name is based on the lateral projections on both sides of their heads giving them a hammer-like shape. The shape of the head helps them make sharper turns without losing stability than other sharks.

The eyes being located on the sides of the shark’s distinctive hammer would allow better stereoscopic (360-degree) vision. Also, the broad sharp of the head provides a larger sensor area which would enable the shark’s sensing organs, to scan the ocean and detect the electrical fields created by prey animals even if buried under the sand in the sea bottom.

Reproduction behavior: The hammerheads reproduce once a year. They exhibit a viviparous mode of reproduction with females giving birth to live young. The fertilization is internal in which the male transfers its sperm inside the female’s body and so the embryos are nourished from their mother through a yolk sac placenta until baby sharks about 12-15 baby sharks are born after a gestation period of 10-12 months. Newly born sharks develop on their own with no parental care of any sort.

Feeding behavior: Hammerhead sharks are carnivores and are known to eat a large range of items including fish, squid, octopus, crustaceans, and other hammerhead sharks. The hammerhead shark uses its unique head to pin down stingrays; their favorite prey.

Hammerheads are characterized by the slow pass of their food through the intestines as reflected in their low feed frequency which explains their slow growth rate.

Threats: Commercial fisheries catch hammerheads is done for their fins (for fin soup), oil (for vitamin), meat, skin (for leather), and offal (for fish meal). Also, hammerheads are caught accidentally by longlining crews fishing for swordfish and tuna. The schooling pattern of hammerheads make them easy target for fishermen.  

References: National Geographic, Fast facts, Aquatic Community, Wikipedia



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