Shortfin mako shark

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Shortfin mako shark
Conservation status
Scientific classification
Kingdom: Animalia
Class: Chondrichthyes
Order: Lamniformes
Family: Lamnidae
Genus: Isurus
Species: I. oxyrinchus
Binomial name
Isurus oxyrinchus
Rafinesque, 1810

The shortfin mako shark (Isurus oxyrinchus—meaning "sharp nose"), or blue pointer, is a large mackerel shark. It is commonly referred to as the mako shark together with the longfin mako shark (Isurus paucus).

Etymology

In 1809, Constantine Rafinesque first described the shortfin mako and coined the name Isurus oxyrinchus (Isurus means "the same tail", oxyrinchus means "pointy snout"). "Mako" comes from the Māori language,[2] meaning either the shark or a shark tooth. It may have originated in 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,[3] mangō in other Māori dialects,[3] "mago" in Samoan, 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".[4][5] 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".[6]

Description

The Shortfin Mako is a fairly large species of shark. An average adult specimen will measure around 3.2 m (10 ft) in length and weigh from 60–135 kg (132–298 lb). Females are larger than males. The largest shortfin mako shark taken on hook-and-line was 600 kg (1,300 lb), caught off the coast of California on June 3, 2013. Larger specimens are known, with a few large, mature females exceeding a length of 3.8 m (12 ft) and a weight of 570 kg (1,260 lb).[7] The longest verified length for a Shortfin Mako caught off France in September 1973, was 4.45 m (14.6 ft). A specimen caught off Italy, and examined in an Italian fish market in 1881, was reported to weigh an extraordinary 1,000 kg (2,200 lb) at a length of 4 m (13 ft).[8] Growth rates appear to be somewhat more accelerated in the Shortfin Mako than they are in other species in the lamnid family.[7]

The Shortfin Mako is cylindrical in shape, with a vertically-elongated tail that assists its highly hydrodynamic lifestyle. This species' color is brilliant metallic blue dorsally and white ventrally, although coloration varies as the shark ages and increases in size. The line of demarcation between blue and white on the body is distinct. The underside of the snout and the area around the mouth are white. Larger specimens tend to possess darker coloration that extends onto parts of the body that would be white in smaller individuals. The juvenile mako differs in that it has a clear blackish stain on the tip of the snout. The Longfin mako shark very much resembles the Shortfin, but has larger pectoral fins, dark rather than pale coloration around the mouth and larger eyes. The presence of only one lateral keel on the tail and the lack of lateral cusps on the teeth distinguish the makos from the closely related porbeagle sharks of the genus Lamna.[7]

Ecology

Range and habitat

The shortfin mako inhabits 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), normally far from land though occasionally closer to shore, around islands or inlets.[9] One of only four known endothermic sharks, it is seldom found in waters colder than 16 °C (61 °F).[10]

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 neither abundant nor rare. Swordfish are a good indication of shortfin makos as the former is a source of food and prefers similar environmental conditions.[11]

Shortfin makos travel long distances to seek prey or mates. In December 1998, a female tagged off California was captured in the central Pacific by a Japanese research vessel, meaning this fish traveled over 1,725 miles (2,776 km). Another swam 1,322 miles (2,128 km) in 37 days, averaging 36 miles (58 km) a day.[12]

Feeding

The head of a mako shark.

The shortfin mako feeds mainly upon cephalopods, bony fishes including mackerels, tunas, bonitos, and swordfish, but it may also eat other sharks, porpoises, sea turtles, and seabirds. They hunt by lunging vertically up and tearing off chunks of their preys' flanks and fins. Makos swim below their prey, so they can see what is above and have a high probability of reaching prey before it notices. Biting the caudal peduncle (near the tail) can immobilize the prey. In Ganzirri and Isola Lipari, Sicily, shortfin makos have been found with amputated swordfish bills impaled into their head and gills, suggesting that swordfish seriously injure and likely kill makos. In addition, this location, and the late spring and early summer timing, corresponding to the swordfish's spawning cycle, suggests that these makos hunt while the swordfish are most vulnerable, typical of many predators.[9]

Shortfins consume 3% of their weight each day and take about 1.5–2 days to digest an average-sized meal. By comparison, the sandbar shark, an inactive species, consumes 0.6% of its weight a day and takes 3 to 4 days to digest it. An analysis of the stomach contents of 399 male and female mako sharks ranging from 67–328 centimetres (26–129 in) suggest makos from Cape Hatteras to the Grand Banks prefer bluefish, constituting 77.5% of the diet by volume. The average capacity of the stomach was 10% of the total weight. Shortfin makos consumed 4.3% to 14.5% of the available bluefish between Cape Hatteras and Georges Bank.[13]

Shortfin over 3 m (9.8 ft) have interior teeth considerably wider and flatter than smaller makos, which enables them to prey effectively upon dolphins, swordfish, and other sharks.[12] An amateur videotape, taken in Pacific waters, shows a moribund spotted dolphin whose tail was almost completely severed, with a very large shortfin mako circling the dying dolphin. Makos also tend to scavenge long-lined and netted fish.[14]

Jaw

Its endothermic constitution partly accounts for its relatively great speed.[15]

Like other lamnid sharks, the shortfin mako has a heat exchange circulatory system that allows the shark to be 7–10°F (4–7°C) warmer than the surrounding water. This system enables makos to maintain a stable, very high level of activity,[16] giving it an advantage over its cold-blooded prey.[17]

Behavior

The Shortfin Mako is the fastest species of shark.[7] Its speed has been recorded at 50 kilometres per hour (31 mph) with bursts of up to 74 kilometres per hour (46 mph).[18] Though scientists are still in debate over exactly how fast the shortfin mako shark can swim, some suggest that they can reach 100 kilometres per hour (62 mph). This high-leaping fish - they can leap approximately 9 metres (30 ft) high or higher in the air - is a highly sought-after game fish worldwide. There are cases when an angry mako jumped into a boat after having been hooked.[19]

This shark is highly migratory.[citation needed]

Life history

Reproduction

The shortfin mako shark is a yolk-sac ovoviviparous shark, giving birth to live young. Developing embryos feed on unfertilized eggs within the uterus during the 15 to 18 month gestation period - this is called (oophagy) (i.e. egg-eating). Shortfins do not engage in sibling cannibalism unlike 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 centimetres (28 in). It is believed that females may rest for 18 months after birth before mating again. Last and Stevens (2009) report shortfin makos bear young on average every 3 years.[20]

Lifespan

Shortfin makos, as with most other sharks, are aged by sectioning vertebrae — one of the few bony structures in sharks — and counting growth bands. The age of shortfin mako, and therefore important parameters, such as age at sexual maturity and longevity, were severely underestimated until 2006 (e.g. claims of sexual maturity at 4–6 years, claims of longevity as low as 11 years), because of a poorly-supported belief that shortfin mako sharks deposited two growth bands per year in their vertebrae. This belief was overturned by a landmark study by Natanson et al. (2006), which proved that shortfin mako sharks only deposit one band in their vertebrae per year, as well as providing validated ages for numerous specimens.[21] Natanson et al. (2006) aged 258 shortfin mako specimens and recorded:

  • Maximum age of 29 years in males (260 cm fork length (FL))
  • Maximum age of 32 years in females (335 cm FL)
  • 50% sexual maturity at 8 years in males (185 cm FL)
  • 50% sexual maturity at 18 years in females (275 cm FL)

Bishop et al. (2006) made similar, validated age findings (median age at maturity in males 7–9 years, median age at maturity in females 19–21 years, longevity estimates 29 years and 28 years respectively) in New Zealand waters.[22]

The seriousness of this ageing error cannot be understated. It means that fishery management models and ecological risk assessment models in use around the world were underestimating both the longevity and the age at sexual maturity in shortfin mako sharks, particularly in females, by two thirds or more (i.e. 6 years versus 18+ years), and some of these inccurate models remain in use.

Relation to humans

Unsustainable consumption

In 2010, Greenpeace International added the shortfin mako shark (Isurus oxyrinchus or mackerel shark) to its seafood red list, "a list of fish that are commonly sold in supermarkets around the world, and which have a very high risk of being sourced from unsustainable fisheries."[23]

In 2010, the Convention on Migratory Species (CMS) also added the shortfin mako shark to Annex I of its Migratory Sharks MoU. This Memorandum of Understanding, currently in effect, serves to increase international understanding and coordination for the protection of certain migratory sharks.[24]

Captivity

Of all recorded attempts to keep pelagic shark species in captivity, the shortfin 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 on arrival but had trouble negotiating the walls of the aquarium, refused to feed, quickly weakened and died.[25]

Attacks on humans

ISAF statistics records forty-two shortfin attacks on humans between 1980 and 2010, three of which were fatal, along with twenty boat attacks.[26] The mako is regularly blamed for attacks on humans and, due to its speed, power and size, it is certainly capable of injuring and killing people. However, this species will not generally attack humans and does not seem to treat them as prey. Most modern attacks involving mako sharks are considered to have been provoked due to harassment or the shark being caught on a fishing line.[27] Sharks can be attracted to spear fishermen carrying a stuck fish, and may slap them with cavitation bubbles from a swift tail flick. Divers who have encountered shortfin makos note that, prior to an attack, they will swim in a figure eight pattern and approach with mouths open.[27]

World record

On June 3, 2013, Jason Johnston from Mesquite, Texas caught an 11-foot-long (3.35 m), 8-foot (2.44 m) circumference Shortfin mako shark, weighing 1,323 pounds (600 kg), off Huntington Beach, California. A certified weigh master called it a world record.[28]

See also

For a topical guide to this subject, see Outline of sharks.

Notes

  1. ↑ "More oceanic sharks added to the IUCN Red List" (Press release). IUCN. 2007-02-22. Retrieved 2007-02-25. "The global threat status was heightened for shortfin mako, a favorite shark among commercial and recreational fishermen, from Near Threatened in 2000 to Vulnerable today." 
  2. ↑ "Maori language – a glossary of useful words from the language of the Maori New Zealand". Retrieved 2006-08-11. 
  3. ↑ 3.0 3.1 H. W. Williams (1971). Dictionary of the Maori Language (7th ed.). 
  4. ↑ Oxford: The Dictionary of New Zealand English: New Zealand words and their origins. 1997. 
  5. ↑ "Online Etymology Dictionary". Retrieved 2008-03-08. 
  6. ↑ Richard Taylor (1848). A leaf from the natural history of New Zealand. xiii. 
  7. ↑ 7.0 7.1 7.2 7.3 FLMNH Ichthyology Department: Shortfin Mako. Flmnh.ufl.edu. Retrieved on 2012-08-22.
  8. ↑ Kabasakal, H. and De Maddalena, A. (2011) A huge shortfin mako shark Isurus oxyrinchus Rafinesque, 1810 (Chondrichthyes: Lamnidae) from the waters of Marmaris, Turkey. Annales, Series Historia Naturalis, 21 (1): 21–24
  9. ↑ 9.0 9.1 "The Shark Gallery – Shortfin Mako Shark (Isurus oxyrinchus)". "The Shark Trust". Retrieved 2008-10-02. 
  10. ↑ "Shortfin Mako sharks(Isurus oxyrinchus)". Shark Foundation / Hai-Stiftung. 05/08/29. Retrieved 2008-11-18. 
  11. ↑ Campana, Steven; Warren Joyce,Zoey Zahorodny (2 October 2008). "Shortfin Mako". The Canadian Shark Research Laboratory. Retrieved 2008-11-16. 
  12. ↑ 12.0 12.1 R. Aidan Martin (2003). "Open Ocean: the Blue DesertShortfin Mako". ReefQuest Centre for Shark Research. Retrieved 2008-11-14. 
  13. ↑ Stillwell, C.E.; Kohler, N.E. (1982). "Food, Feeding Habits, and Estimates of Daily Ration of the Shortfin Mako (Isurus oxyrinchus ) in the Northwest Atlantic.". Canadian Journal of Fisheries and Aquatic Sciences 39 (3): 407–414. doi:10.1139/f82-058. Retrieved 2008-11-04. 
  14. ↑ Fergusson, Ian. "Shortfin Mako Shark (Isurus oxyrinchus)". Retrieved 2008-11-18. 
  15. ↑ Passarelli, Nancy; Craig Knickle and Kristy DiVittorio. "SHORTFIN MAKO". Florida Museum of Natural History. Retrieved 2008-10-06. 
  16. ↑ "Shortfin Mako". Australian Museum. May 2007. Retrieved 2008-11-15. 
  17. ↑ "Shortfin Mako Shark". 2008 Discovery Communications, LLC. October 30, 2007. Retrieved 2008-11-04. 
  18. ↑ R. Aidan Martin. "Biology of the Shortfin Mako". ReefQuest Centre for Shark Research. Retrieved 2006-08-12. 
  19. ↑ Grimble, Sir Arthur (1952). "A Pattern of Islands; Ch. 5 Lagoon Days". Early New Zealand Books (NZETC). Retrieved 16 Oct 2011. 
  20. ↑ Last, PR; & Stevens JD (2012). Sharks and Rays of Australia — Second Edition. Australia: CSIRO (Commonwealth Scientific and Industrial Research Organisation). ISBN 978-0-643-09457-4. 
  21. ↑ Natanson, L.J.; Kohler, N.E., Ardizzone, D., Cailliet, G.M., Wintner, S.P. and Mollet, H.F. (2006). "Validated age and growth estimates for the shortfin mako, Isurus oxyrhinchus, in the North Atlantic Ocean.". Environmental Biology of Fishes 77 (3–4): 367–383. doi:10.1007/s10641-006-9127-z. 
  22. ↑ Bishop, S.D.H.; Francis, M.P., Duffy, C. and Montgomery, J.C. (2006). "Age, growth, maturity, longevity and natural mortality of the shortfin mako shark (Isurus oxyrinchus) in New Zealand waters". Marine and Freshwater Research 57: 143–154. doi:10.1071/MF05077. 
  23. ↑ Greenpeace International Seafood Red list. greenpeace.org
  24. ↑ MEMORANDUM OF UNDERSTANDING ON THE CONSERVATION OF MIGRATORY SHARKS. cms.int
  25. ↑ Elasmobranch Research around Monterey Bay
  26. ↑ ISAF Statistics on Attacking Species of Shark. Flmnh.ufl.edu (2012-01-30). Retrieved on 2012-08-22.
  27. ↑ 27.0 27.1 Isurus oxyrinchus Shortfin Mako Shark.marinebio.org
  28. ↑ "1,323-pound shark caught off coast of Huntington Beach". KABC TV. Retrieved 6 June 2013. 

References

Wikispecies has information related to: Isurus oxyrinchus

External links

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