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Scalloped Hammerhead Shark
Threat Level: low
Scientific name.......Sphyrna Lewini
Other common names......Kidney Hammerhead shark and Bronze Hammerhead shark.
The Scalloped Hammerhead, belongs to a family of eight sharks with a unique specialization, the front of the skull expands laterally like a hammer to form a head structure called a cephalofoil. This serves many biological functions. Its wide, flattened shape adds lift during swimming, improving hydrodynamic efficiency. The increased surface area allows for the expansion of many sensory systems important for feeding. The eyes and nares are at the tips of the head; the electroreceptor's and lateral line are are over a wider area. Thus these fast, active sharks can capture large or elusive prey. Scalloped hammerheads can be distinguished by the broad leading edge on the head, which is arched toward the back. There is a prominent indentation in the center with two smaller lobes on either side, giving a scalloped look. They have elongated rounded slender bodies with two dorsal fins, the first of which is high and pointed, second dorsal and pelvic fins low. They have five gill slits. There tails cresent-shaped.
The maximum length these sharks can reach is 13.7 feet. Males mature at 4.6 to 5.4 feet and females mature at 7 feet. Pups are born at a length of 17 to 22 inches.
They are a light gray or bronzy above, and white below, with a dusky or black-tipped pectoral fins, with a dark blotch on lower caudal fin lobe.
There diet consists of bony fishes, sharks, rays, and invertebrates.
These sharks display a high degree of complex intraspecific behaviours, and seen by divers interacting, chasing, thrusting, shaking their heads, and biting each other. This behaviour needs further study, but may be for social reasons, migration to feeding areas, or reproduction. Adults can be found solitary, in pairs or schools, young are found in large schools.
They are found world-wide, in warm temperate and tropical seas. These sharks occur in coastal areas above continental and island shelves, and in adjacent offshore waters to depths of near 1,000 feet. They enter shallow bays and estuaries, and aggregate around seamounts. Juveniles mainly inshore, reducing the chances that larger sharks will feed on them.
Viviparous, bearing 15 to 30 pups per litter measuring 17 to 22 inches. Pregnancy last 9 to 10 months.
Considered potentially dangerous to people but usually unaggressive and shy when approached by divers.
Scalloped hammerheads are the most common of all the hammerheads. Lack of data on population trends makes it difficult to assess whether the high level of catches of this species at all life stages is having an effect on stocks, but some declines are reported.
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