The shortfin mako (Isurus oxyrinchus) is
believed to be the fastest-swimming of all sharks, thought to be
capable of attaining bursts of speed of up to 35 kilometres per hour,
and famed for making spectacular leaps of up to six metres out of the
water. The shortfin makos’ high tail produces maximum thrust to propel
the shark rapidly forward, both in extreme bursts of speed, and for
sustained, long-distance travel. The shortfin mako also has a heat
exchange circulatory system that enables the body to be warmer than
surrounding water, and thus maintain a high level of activity. This
large, stream-lined shark has a distinctively crescent-shaped caudal
fin, a long, conical snout, large black eyes and razor-sharp, blade-like
teeth. The upper body is a brilliant metallic blue, while the underside
is snow-white, with older, larger specimens tending to be darker with
reduced white areas. Juveniles are therefore generally paler than
adults, and also differ by possessing a clear black mark on the tip of
their snout. The shortfin mako can be distinguished from the only other
mako shark, the longfin mako (Isurus paucus), not only by having shorter
pectoral fins, but also by the white colouration on the underside of
the snout and around the mouth, which is darkly pigmented in the longfin
mako.
Given this shark’s relative notoriety, particularly among
anglers, surprisingly little is known of its biology. Reproductive
knowledge of the solitary shortfin mako is sparse, largely because
pregnant females usually abort embryos upon capture, making study
difficult. Reproduction is ovoviviparous, with embryos being nourished
in the uterus by a yolk sac rather than placenta. Once the young have
hatched, uterine cannibalism known as oophagy occurs, in which the
growing young feed on unfertilised or less-developed eggs. Litters of
between 4 and 25 live young are born in the late winter and early
spring, after a 15 to 18 month gestation period. This is followed by an
initial relatively fast growth rate. Females are believed to rest for 18
months after birth before conceiving again. Females appear to become
sexually mature at around 17 to 19 years of age and males mature around 7
to 9 years. The maximum known age of a shortfin mako is 32 years.
The
shortfin mako primarily feeds on a wide variety of fishes, such as
swordfish, tuna, mackerel, cod, sea bass, and even other sharks,
including blue sharks (Prionace glauca), grey sharks (Carcharhinus
species) and hammerheads (Sphyrna species). However, squid, sea turtle
heads, and a ‘porpoise’ (probably a pelagic dolphin) have also been
found in the stomachs of these sharks.
This is a wide-ranging
shark found in tropical and temperate waters throughout the world’s
oceans. In the Western Atlantic, the shortfin mako occurs from the Gulf
of Maine to southern Brazil, including the Gulf of Mexico and the
Caribbean. In the Eastern Atlantic, the distribution ranges from Norway,
down past the British Isles, the Mediterranean, the Ivory Coast and
Ghana to South Africa. In the Indo-Pacific, the shortfin mako shark is
found from East Africa and the Red Sea to Hawaii, including waters
around Pakistan, India, Korea, Japan, Indonesia, Australia, Tasmania,
and New Zealand. In the Eastern Pacific, the range includes waters south
of the Aleutian Islands and from Southern California, USA, to Chile.
The shortfin mako is usually pelagic, but can sometimes be found close inshore. Although normally occupying surface waters down to around 150 metres, this shark has been recorded at depths of up to 740 metres. There is evidence to suggest that this species migrates seasonally to warmer waters.
The shortfin mako is usually pelagic, but can sometimes be found close inshore. Although normally occupying surface waters down to around 150 metres, this shark has been recorded at depths of up to 740 metres. There is evidence to suggest that this species migrates seasonally to warmer waters.
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