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.
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
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
The great hammerhead is listed
as endangered throughout its range, due primarily
to accidental capture by commercial fishing
genus & species Sphyrna mokarran
Florida Museum of Natural History
MarineBio Conservation Society http://marinebio.org/species.asp?id=87
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