|THE ROBINSON LIBRARY|
|The Robinson Library >> Science >> Zoology >> Fishes >> Class Chondrichthyes|
|Great Hammerhead Shark
The great hammerhead can be distinguished from other hammerheads by the shape of its "hammer," which is wide with an almost straight front margin, and by its tall, sickle-shaped first dorsal fin. Another distinguishing characteristic of the great hammerhead is the curved rear margins on the pelvic fins. Juveniles have slightly curved heads at the front margin that become nearly straight as they reach adulthood.
The dorsal side of the great hammerhead is dark brown to light grey or even olive in color, fading to white on the underside. The fins lack markings in adults, while the apex of the second dorsal fin may appear dusky in juveniles.
The largest member of the hammerhead family averages over 500 pounds and can reach a length of up to 20 feet.
Distribution and Habitat
The great hammerhead inhabits tropical waters around the world, between the latitudes of 40°N and 37°S. They can be found from inshore waters less than 3.3 feet deep, to a depth of 230 feet offshore. They favor coral reefs, but also inhabit continental shelves, island terraces, lagoons, and deep water near land. The great hammerhead migrates seasonally, moving poleward to cooler waters during the summer months.
Great hamerheads are active predators, preying upon a wide variety of marine organisms, from invertebrates to bony fishes and sharks. Invertebrate prey include crabs, squid, octopus, and lobsters, while commonly consumed bony fish are groupers, catfishes, jacks, grunts, and flatfishes. A favorite prey item is the stingray. Great hammerheads have also been reported as cannibalistic. It feeds primarily at dusk along the seafloor as well as near the surface using its complex electro-sensory system to locate prey.
In contrast to most other species of sharks that reportedly mate at or near the bottom, the great hammerhead has been observed mating near the surface of the water.
Following a gestation period of approximately 11 months, live birth occurs during the spring or summer in the Northern Hemisphere. The resulting litters range in size from 6 to 42 young, with the pups measuring between 20 and 30 inches in length.
The great hammerhead is listed as endangered throughout its range, due primarily to accidental capture by commercial fishing vessels.
|The Robinson Library
>> Zoology >> Fishes >> Class Chondrichthyes
This page was last updated on June 23, 2017.