Isurus oxyrinchus

Author: Rafinesque, 1809

Field Marks:
Spindle-shaped body, long, acutely conical snout, large bladelike teeth without cusplets or serrations, pectoral fins rather narrow-tipped and with anterior margins less than head length, large first dorsal fin and minute, pivoting second dorsal and anal fins, strong keels on caudal peduncle, no secondary keels on caudal base, crescentic caudal fin, ventral surface of body white.

Diagnostic Features:
Body moderately slender. Snout acutely conical; eye moderately large; cusps of first upper anterior teeth with incomplete cutting edges, in young and small adults, tips of anterior teeth strongly reflexed, cusps narrower and more oblique. Pectoral fins moderately long and broad, shorter than head. Colour: underside of snout white.

Geographical Distribution:
Coastal and oceanic, temperate and tropical. Western Atlantic: Gulf of Maine to southern Brazil and ? northern Argentina, including Gulf of Mexico and Caribbean. Eastern Atlantic: Norway, British Isles and Mediterranean to Ivory Coast, Ghana, and South Africa. Indo-West Pacific: South Africa and Red Sea to Pakistan, India, Indonesia, the Koreas, Japan, USSR (Primorsk Kray), Australia (Queensland, Tasmania, South and western Australia, Victoria, New South Wales), New Zealand, New Caledonia, Fiji. Central Pacific: From south of Aleutian Islands to Society Islands, including Hawaiian Islands. Eastern Pacific: Southern California and exceptionally Washington (USA) to central Chile.

Habitat and Biology:
The shortfin make is a common, extremely active, offshore Oittoral and epipelagic species found in tropical and warm temperate seas but seldom occurring in waters below 16 C. This shark occurs from the surface down to at least 152 m. The peregrine falcon of the shark world, the shortfin mako may be the fastest shark and one of the swiftest and most active fishes. It is famed as a jumper, leaping several times its length from the water, and is capable of extreme bursts of speed when hooked and in pursuit of prey. For a shark of such a great fame, particularly in the angling literature, knowledge of its biology is surprisingly sketchy.

The shortfin mako, in the extreme northern and southern parts of its range, has a tendency to follow movements of warm water masses poleward in the summer. General movements of this shark are not well known.

This species is ovoviviparous and a uterine cannibal, with 4 to 16 young in a litter.

The shortfin mako is primarily an eater of other fishes, with a wide variety of prey including mackerels, tunas, bonitos, and other scombrids, anchovies, herrings, grunts, lancetfishes, cod, ling, whiting and other gadids, Australian salmon (Arripis), yellowtails and other carangids, sea basses, porgies, swordfish, and other sharks (blue sharks, Prionace, grey sharks, Carcharhinus, and hammerheads Sphyrna), but also sea turtle heads, a 'porpoise' (probably a pelagic dolphin), and also squids, salps, and occasionally detritus. Surprisingly, marine mammals (in the form of pelagic dolphins) are rarely reported in the diet of the shortfin mako, but they may be expected particularly in large individuals of the species. Very large shortfin makos over 3 m long have very broad, more flattened and triangular upper teeth, perhaps more suitable for dismembering large prey than the awl-shaped teeth of smaller makos.

Attacks on divers and swimmers by this shark are relatively rare and few are reliably reported, but these have occurred and suggest that this shark should be regarded as definitely dangerous. The offshore habitat of this species probably prevents it from coming in contact with many swimmers. Its speed, power, huge and wicked teeth, and aggressivenenss when a feeding stimulus (like speared fish) is present should be cause for divers, especially spearfishers, to treat this shark with extreme caution. The shortfin mako tends to respond vigorously when hooked or harassed, and it should NOT be speared or provoked underwater; a counterattack by this animate torpedo may be far too quick for anti-shark weapons to be effective. A number of attacks by the mako on boats are known, and these are second in number only to those perpetrated by the white shark. Most of these attacks probably have occurred while makos were being played by anglers. The angling and popular literature is rife with 'mako stories', in which these sharks bite, jump into, or even smash right through the boats of their assailants; anglers who suddenly find themselves sharing a boat with an aroused mako have been known to leap into the water!

Size:
Maximum total length about 394 cm, possibly to 4 m, males maturing at about 195 cm and reaching at least 284 cm; females maturing at about 280 cm and reaching at least 394 cm; size at birth between 60 and 70 cm. Two recently published exponential length-weight curves are at slight variance:
WT = 4.832 x 10-6 TL3.10 (Stevens, 1983, N = 80, TL = 58-343 cm, Australia).

WT = 1.193 x 10-6 TL3.46 (Guitart Manday, 1975, N = 23, TL = 160-260 cm, Cuba).

A log curve, log WT = -4.608 + 2.925 log TL (cm), was published by Strasburg (1958) for this species using central Pacific specimens.

Interest to Fisheries:
This is an important species for longline fisheries where it occurs, because of its highquality meat, and also is a prime game fish prized by sport anglers. Considerable fisheries for shortfin mako occur in the Mediterranean (landed in Italy), off West Africa, off Cuba, in the Gulf of Mexico and Caribbean, off southern California, and in the western and central Pacific. The meat is utilized fresh, frozen, smoked and dried salted for human consumption; the oil is extracted for vitamins; the fins used for shark-fin soup; the hides processed into leather and the jaws and teeth used for ornaments. This shark is caught in gillnets as well as on pelagic longlines and hook-and-line.

Remarks:
The synonymy of this species follows Garrick (1967).

Type material:
Holotype: Unknown. Type Locality: Sicily, Mediterranean Sea.

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