AY Honors/Species Account/Isurus oxyrinchus

The shortfin mako shark, Isurus oxyrinchus ("sharp nose"), is a large mackerel shark. Along with the closely related longfin mako (Isurus paucus) it is commonly referred to as "mako shark".

Anatomy and appearance

This species grows to an average full-grown length of 1.82–3.2 m (6–10 ft) and to a weight of approximately 60–400 kg (135-880 lb). The largest reported mako was said to be 1,000 kg (2,200 lb) and 4 m (13.2 ft), although the largest confirmed size is 3.96 m (13 ft) and 794 kg (1,750 lb). It has a bluish back and white underside. Although the sexes grow at about the same rate, females are thought to have a longer life span, and grow larger and weigh more than the males. Shortfin makos are renowned for their speed and their ability to leap out of the water. In fact, there are cases when an angry mako will jump out of the water and into the boat after it has been caught on the hook. Mako sharks have a better hydrodynamic shape than all other sharks other than the salmon shark, and this, combined with the lamnidae's typical high aerobic muscle mass, reflects in the spectacular speed and agility of both the longfin and shortfin makos. Makos have placoid scales that covers the skin to reduce friction during swimming, which makes the skin very abrasive.

The shortfin mako shark is a sleek spindle-shaped shark with a long conical snout. This shark has short pectoral fins and a crescent shaped caudal (tail) fin. There is a distinct caudal keel on the caudal base. Its second dorsal fin is much smaller than the first. The apex of pectoral fin and first dorsal fin are rounded in younger makos. The teeth are slender and slightly curved with no lateral cusps and are visible even when the mouth is closed. There is marked countershading on this shark; dorsally it is a metallic indigo blue while ventrally it is white.

Naming

In 1809, Constantine Rafinesque was the first person who described shortfin mako in the scientific literature and coined the name Isurus oxyrinchus (Isurus means "the same tail", oxyrinchus means "pointy snout", both in Latin). The name "mako" comes from the Māori language, meaning either the mako shark or a shark tooth. It may simply have originated from a dialectal variation as it is similar to the common words for shark in a number of Polynesian languages - makō in the Kāi Tahu Māori dialect, mangō in other Māori dialects, ma'o in Tahitian, and mano in Hawaiian. The first written usage is in Lee & Kendall's Grammar and vocabulary of the language of New Zealand (1820), which simply states "Máko; A certain fish". Richard Taylor's A leaf from the natural history of New Zealand (1848) is more elaborate: "Mako, the shark which has the tooth so highly prized by the Maoris".

Diet

The head of a mako shark.

The shortfin mako feeds mainly upon cephalopods, bony fishes including mackerels, tunas, bonitos, swordfish, and sailfish, but it may also eat other sharks, porpoises, sea turtles, and seabirds. They hunt by sheer speed, swimming vertically up and take repeated bites on the preys flanks and fins, because the makos colouration are countershaded, so that the prey has less likely to be seen themselves. In Ganzirri and Isola Lipari, Sicily, shortfin makos have been found with amputated swordfish bills impaled into their head and gills, suggesting from the dangerous location of the wounds found on the Mako sharks that swordfish seriously injure and likely kill makos. In addition, this location, off the coast of Sicily and the timing, late spring and early summer, corresponding to the swordfish's spawning cycle suggests that these makos prey on swordfish while they are most vulnerable, typical of many predators.

An analysis of the stomach contents of 399 male and female mako sharks ranging from 67 to 328 cm suggest makos from Cape Hatteras to the Grand Banks prefer bluefish to any other food source. In the study, bluefish constituted 77.5% of the diet by volume. The average capacity of the stomach was 10% of the body weight. Shortfin makos consumed 4.3 to 14.5% of the available bluefish between Cape Hatteras and Georges Bank.

Shortfin makos over 3 m (10 ft.) have been found to have interior teeth considerably wider and flatter than smaller makos, which enables them to prey effectively upon dolphins, swordfish, and other sharks.

In recent years it has been suggested that adult makos infrequently attack free-swimming dolphins. This hypothesis appeared validated when an amateur video, taken in Pacific waters, emerged, showing a moribund spotted dolphin whose tail was almost completely severed, just after a shark attack. The video shows a very large shortfin mako circling the dying dolphin. Makos also have the tendency to scavenge on long-lined and netted fish.

Distribution

The shortfin mako is found in offshore temperate and tropical seas worldwide. The closely related longfin mako shark, Isurus paucus, is found in the Gulf Stream or warmer offshore waters.

It is a pelagic species that can be found from the surface down to depths of 150 m (490 ft.). The shortfin mako is found in blue waters, normally far from land though occasionally closer to shore, particularly around islands or inlets. One of only four known endothermic sharks, it is seldom found in waters colder than 16° C (61° F).

In the western Atlantic it can be found from Argentina and the Gulf of Mexico to Browns Bank off of Nova Scotia. In Canadian waters these sharks are not abundant as they prefer warm waters, but neither are they rare. Shortfin makos are often found in the same waters as swordfish as they are a source of food and both fish prefer similar environmental conditions.

It is suggested shortfin makos travel long distances to seek adequate prey or fitting mates. In December 1998, a female shortfin mako tagged off California was captured in the central Pacific by a Japanese research vessel, meaning this fish traveled over 1,725 miles (2,780 kilometers).

Behavior

The shortfin mako's speed has been recorded at 50 km/h (31 mph), and there are reports that it can achieve bursts of up to 74 km/h (46 mph). It can jump up to 9 m (28 ft.) in the air. Due to its speed and agility, this high-leaping fish is sought as game worldwide. This shark is highly migratory. Its endothermic constitution partly accounts for its relatively great speed.

There is still some uncertainty about its lifespan, but it is suspected to reach ages of between 11 to 23 years.

Like other lamnid sharks, the shortfin mako has a heat exchange circulatory system that allows the shark to be seven to ten degrees warmer than the surrounding water. This system enables the shortfin to maintain a high level of activity. This could be the reason for their great hunting abilities. The higher body temperature give the sharks an advantage over its cold-blooded prey.

Reproduction

The shortfin mako shark is a yolk-sac ovoviviparous shark, meaning it gives birth to live young. Developing embryos feed on unfertilized eggs produced by the mother in the uterus during the gestation period of 15 to 18 months. This is called (oophagy) (i.e. egg-eating). In fact, there is no evidence of sibling cannibalism in short-fin mako as there is in the sand tiger shark (Carcharias taurus). The 4 to 18 surviving young are born live in the late winter and early spring at a length of about 70 cm. It is believed that females may rest for 18 months after birth before the next batch of eggs are fertilized.

Male shortfin makos reach sexual maturity within 4 years. The oldest ever found "Caroline" is at the walka aquarium.

One study conducted by NOAA in 1997, showed times at liberty ranged from 13 days to 12.8 years. This phenomenal 12.8 year recapture was in 1997 the longest time at liberty for any mako. Along with the shark itself a piece of the backbone was collected to confirm the age estimates. The recapture of this shark proved that shortfin makos can in fact live at least 13 years. This information can in turn be used to better manage the species.

Distinguishing characteristics

• Teeth are visible even when the mouth is closed
• Teeth are long and slender with smooth-edged cusps
• Distinct countershading, dorsally blue and ventrally white
• Moderately short pectoral fins
• Underside of the snout is white

Captivity

Of all recorded attempts to keep pelagic shark species in captivity, the short-fin mako has fared the poorest; even more so than the oceanic whitetip shark, the blue shark and the great white shark. The current record is held by a specimen that, in 2001, was kept at the New Jersey Aquarium for only five days. Like past attempts at keeping Isurus in captivity, the animal appeared strong upon arrival but had trouble negotiating the walls of the aquarium, refused to feed, quickly weakened and expired.

Attacks on humans

The shortfin mako has a formidable and foreboding appearance. The ISAF statistics on attacking species of sharks purports that between 1580 and 2007, the shortfin mako has had eight recorded unprovoked attacks on humans with two ending in fatality and twenty boat attacks. In New Zealand Mako sharks are often encountered in the waters of the North Island. Sharks can be attracted to caught fish with accounts of spear fishermen being approached by curious sharks and even being "slapped" with cavitation bubbles from a swift tail flick.

Short fin mako sharks in popular culture

• A mako shark appeared in Ernest Hemingway's novella, The Old Man and the Sea.
• Three short-fin mako sharks appear as the antagonists of the film Deep Blue Sea. Shown using animatronics and CGI, the three sharks are genetically engineered to be super smart, and in one case, extremely large. They proceed to destroy the facility they are housed in, and eat most of the scientists studying them, before they are eventually killed (each is killed as an homage to the deaths of the sharks in the Jaws series). There is also a 'tiger shark' seen early in the film, but its appearance is really that of a mako shark with stripes.

See also

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References

• Template:IUCN2006 Database entry includes justification for why this species is near threatened
• Template:ITIS
• Template:FishBase species

External links

• ARKive - images and movies of the shortfin mako (Isurus oxyrinchus)
• CANADA: Record Mako Shark Caught
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• Shortfin mako sharks can shoot through the ocean at up to 50 miles per hour, New Scientist, 7 November 2008