Bluefin tuna

Common name of one of three species of tuna (genus **): the 888888

Pacific bluefin tuna
Conservation status
200px Vulnerable (IUCN)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Perciformes Family: Scombridae Genus: Thunnus Species: T. orientalis
Binomial name
Thunnus orientalis (Temminck and Schlegel, 1844)

Pacific bluefin tuna, Thunnus orientalis are some of the biggest and fastest fish in the Pacific Ocean. They possess streamlined bodies to reduce water resistance and conserve energy for trans-Pacific migrations. Retractable fins also allow a freer flow of water when navigation does not require their use.

Physiology

Thermoregulation

Most fish are cold-blooded (ectothermic). However, tuna and mackerel sharks are warm-blooded: they can regulate their body temperature. Warm-blooded fish possess organs near their muscles called retia mirabilia that consist of a series of minute parallel veins and arteries that supply and drain the muscles. As the warmer blood in the veins returns to the gills for fresh oxygen it comes into close contact with cold, newly oxygenated blood in the arteries. The system acts as a counter-current heat exchanger and the heat from the blood in the veins is given up to the colder arterial blood rather than being lost at the gills. The net effect is an increase in temperature. Fish from warmer water elevate their temperature a few degrees whereas those from cold water may raise it as much as Template:Convert/C-change warmer than the surrounding sea.

The tuna's ability to maintain body temperature has several definite advantages over other sea life. It need not limit its range according to water temperature, nor is it dominated by climactic changes. The additional heat supplied to the muscles is also advantageous because of the resulting extra power and speed. Bluefin tuna have been clocked in excess of 30 miles per hour (48 km/h) during 10 to 20 second sprints, enabling it to hunt squid, herring, mackerel, etc., that slower predators cannot capture.

Distribution

Pacific bluefin tuna spawn in the Western Pacific between Okinawa and the Philippines and probably the Sea of Japan. They migrate over 6,000 nautical miles (11,000 km) to the Eastern Pacific, eventually returning to their birth waters to spawn again.

Life history

Bluefin tuna mature slowly, reaching sexual maturity at about 5 years of age, with a maximum lifespan believed to be about 25 years. Pacific bluefin tuna have been recorded to reach Template:F to m in fork length and can weigh over 1,000 pounds (454 kg). They eat smaller fish, krill, pelagic red crab, mackerel and squid.

Conservation status

Pacific Bluefin Tuna are overfished throughout their range. They are hooked on long lines or illegally netted where they swim, and many young bluefin are captured before they reproduce.^{[citation needed]} Creating effective fishing policies is difficult because they are migratory, swimming through the territorial waters of many different nations. Data about their movements and high levels of international cooperation are needed to ensure sustainable populations.

It is estimated by some that from 1976 to 2006 worldwide stocks of Bluefin Tuna plummeted by 90%.^{[citation needed]} Most seafood sustainability guides recommend consumers choose alternatives to bluefin tuna.

In 2010, Greenpeace International added this population to its seafood red list, saying:

"The Greenpeace International seafood red list is 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."

Environmental issues

The blue fin tuna industry has been on the rise since the 1950s, and during the 1970s it hit a rapid increase in demand. This increase in demand for tuna has led to an equally rapid decline in their population. The number of tuna has hit such an alarmingly low number that they have been put on various endangered species lists. There has been a movement by Monaco to encourage the UN Convention on International Trade in Endangered Species (CITES) to officially put bluefin tuna on the Annex List of Threatened Species.

• What Monaco’s goal would change: This would grant the fish the highest level of international protection. Tuna would be limited to domestic markets only, and absolutely no international trade of the fish or their parts. Since the commercial fishing habits began for bluefin tuna in the 1950s their populations have been estimated to have dropped by anywhere from 75% to as high as 97%. Some conservation groups have predicted their extinction within the next 12 years if current fishing levels don’t diminish. This becomes a problem for a few reasons, one is the fact of extinction, but also what that means for the health and well being of the ocean. Tuna are one of the larger predators found in southern parts of the ocean, and their extinction could mean an overpopulation of many smaller species such as crustaceans, squid, and eels (National Geographic, 2010).

• The International Commission for the Conservation of Atlantic Tunas (ICCAT) and its influence: ICCAT is considered to be “the manager” of the bluefin tuna^{[citation needed]}. They have raised some concerns for conservation groups because ICCAT has set quotas that often double the levels recommended by scientists. At times fishing exceeds even these quota levels. This concern is also mentioned in Monaco’s application to CITES (Gronewold, 2009). The bluefin tuna industry is posing some serious threats to the tuna population through overfishing and opposition to stricter regulations. It also provides a significant income for some countries^{[citation needed]}.

• Players in the tuna industry: The biggest importer is Japan, claiming 90% of the global bluefin catch. Their imports in 2007 were about 32,356 tons of tuna^{[citation needed]}. Occasionally, an individual fish can sell in a Japanese fish market for prices greater than 100,000 USD, but the average price is closer to 10,000 USD. Like many other scarce resources, bluefin tuna’s prices have increased as their populations decrease. In 2002, tuna was the third most valuable export in the fishing business (globefish, org, 2008), giving little incentive for exporters to limit their catch. Some of the larger exporters of 2002 were Taiwan, Indonesia, and Japan. The tuna industry overall brings billions of dollars of revenue for various regions around the world, and while bluefin makes the smallest percentage of all the hunted species of tuna, it also makes the most money per pound.

• Effects of protection policies: Some individual countries have put regulations on the fishing of bluefin; the downside is unemployment of local fishermen^{[citation needed]}. There are concerns that arise from attempting to implement an umbrella policy such as Monaco is proposing: Tuna port countries, many of which are found in the southern hemisphere, are concerned for their fishermen, as well as their source of income^{[citation needed]}.

Farming

Japan is both the biggest consumer and the leader in over tuna farming research. Kinki University of Japan first successfully farmed already-hatched bluefin tuna in 1979. In 2002, they succeeded in breeding them, and in 2007, the process was repeated for a third generation. This farm-raised tuna is now known as Kindai tuna. Kindai is a contraction of Kinki University (Kinki daigaku). In 2009, Clean Seas, an Australian company with assistance from Kinki University managed to breed Southern Bluefin Tuna in captivity, leading Time Magazine to award it second place in World’s Best Invention of 2009.

Northern bluefin tuna
Conservation status
Critically endangered (IUCN)
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Actinopterygii Order: Perciformes Family: Scombridae Genus: Thunnus Species: T. thynnus
Binomial name
Thunnus thynnus (Linnaeus, 1758)

The Northern bluefin tuna (Thunnus thynnus) is a species of tuna in the Scombridae family. It is variously known as the Atlantic bluefin tuna, giant bluefin tuna (for individuals exceeding 150 kilograms or around 330 pounds) and formerly as the tunny. Atlantic bluefin are native to both the western and eastern Atlantic Ocean, as well as the Mediterranean Sea. Atlantic bluefin have become extinct in the Black Sea and Caspian Sea. The Atlantic bluefin tuna is a close relative of the other two bluefin tuna species—the Pacific bluefin tuna and the southern bluefin tuna.

Atlantic bluefin tuna are capable of reaching well over Template:Kg to lb in weight, and rival the black marlin and blue marlin as the largest bony fish. Throughout recorded history, the Atlantic bluefin tuna has been highly prized as a food fish. Bluefin have been a valuable commercial catch from the time of the ancient Greeks and Phoenicians to the modern era. Besides their commercial value as food, their great size and the speed and power they display as apex predators has attracted the admiration and respect of both ancient and modern fishermen, as well as writers, sport anglers and scientists.

The Atlantic bluefin tuna has been the foundation of one of the world's most lucrative commercial fisheries. Medium-sized and large individuals are heavily targeted for the Japanese raw fish market, where all bluefin species are highly prized for sushi and sashimi. This commercial importance has led to severe overfishing. The International Commission for the Conservation of Atlantic Tunas (ICCAT) affirmed in October 2009 that Atlantic bluefin tuna stocks are declining dramatically, by 72% in the Eastern Atlantic, and by 82% in the Western Atlantic. On October 16, 2009 Monaco formally recommended Endangered Atlantic bluefin tuna for an Appendix I CITES listing and international trade ban. In early 2010, European officials, led by the French ecology minister, increased pressure to ban the commercial fishing of bluefin tuna internationally. European Union nations, who are responsible for most bluefin tuna overfishing, later abstained from voting to protect the species from international trade.

Bluefin are captured for the commercial market by professional fishermen using purse seine gear, assorted hook-and-line gear, most importantly the longline, and in certain areas by harpooners. Atlantic bluefin are also taken commercially by heavy rod and reel gear. Since the 1930s the bluefin tuna has long been one of the most important big-game species sought by sports fishermen, particularly in the United States but also in Canada, Spain, France and Italy.

A northern bluefin tuna at the Osaka Aquarium Kaiyukan, Japan

Taxonomy

The Atlantic bluefin tuna is most closely related to the Pacific bluefin tuna (Thunnus orientalis) and the southern bluefin tuna (Thunnus maccoyii), and more distantly to the other large tunas of the genus Thunnus - the bigeye tuna (Thunnus obesus) and the yellowfin tuna (Thunnus albacares). For many years the Pacific and Atlantic bluefin tuna species were considered to be the same, or subspecies, and referred to as the 'northern bluefin tuna'. This name occasionally gives rise to some confusion as the longtail tuna Thunnus tonggol can in Australia be legally sold as canned tuna under the name "northern bluefin tuna". This is also true in New Zealand and Fiji, although canned tuna is less common there.

Bluefin tuna were often referred to as the common tunny, especially in the UK, Australia and New Zealand. The name 'tuna', a derivative of the Spanish 'atun' was widely adopted in California in the early 1900s and has since become accepted for all tunas, including the bluefin, throughout the English-speaking world. In some languages the bluefin's name refers to its red meat - atun roja (Spanish); and tonno rosso (Italian), amongst others.

Description

The body of the northern bluefin tuna is rhomboidal in profile and robust. The head is conical and the mouth rather large. The color is dark blue above and gray below with a gold coruscation covering the body and bright yellow caudal finlets. Bluefin tuna can be distinguished from other family members by the relatively short length of their pectoral fins. Their livers have a unique characteristic in that they are covered with blood vessels (striated). In other tunas with short pectoral fins, such vessels are either not present or present in small numbers along the edges.

Atlantic bluefin tuna can live for 30 years, but due to heavy fishing mortality, few known specimens grow to a mature age.

Fully mature adult specimens average 2–2.5 meters (6.6–8.2 ft) long and around 350 kilograms (770 lb) in weight. The species can reach a maximum length of about 4.3 meters (14 ft). The largest recorded specimen taken under International Game Fish Association rules was caught off Nova Scotia, an area renowned for huge Atlantic bluefin, by Ken Fraser and weighed Template:Kg to lb. According to Gordon Johnston's 'It Happened in Canada' the longest contest between man and tuna fish occurred near Liverpool, Nova Scotia in 1934, when 6 men, taking turns, fought the 795-lb tuna in a terrific battle that lasted sixty-two hours.

The bluefin possesses enormous muscular strength which it channels through a pair of tendons to the sickle shaped tail. In contrast to many other fish, the body stays rigid while the tail flicks back and forth, increasing stroke efficiency.

Thermoregulation

To keep its core muscles warm (used for power and steady swimming), the northern bluefin uses countercurrent exchange to prevent heat from being lost to the surrounding water. The heat in the arterial blood transfers to the venous blood. This keeps the core muscles warm so they can function efficiently.

All members of the tuna family have the ability to thermoregulate. This ability, however, is more highly developed in bluefin tuna than in any other fish, allowing them to seek food in the chilly waters of the north Atlantic

Circulation

Bluefin tuna have a very efficient circulatory system. It possesses one of the highest blood hemoglobin concentrations among fish, which allows them to efficiently deliver oxygen to their tissues; this is combined with their exceptionally thin blood-water barrier to ensure rapid oxygen uptake.

Behavior

Bluefin dive to depths of 1,000 meters (550 fathoms)

Diet and foraging

The northern bluefin tuna typically hunts small fish and invertebrates such as sardines, herring, mackerel, squid and crustaceans.

Parasites

The tetraphyllidean tapeworm Pelichnibothrium speciosum parasitizes this species (Scholz et al. 1998). As the tapeworm's definite host is the blue shark which does not generally seem to feed on tuna^{[citation needed]}, it is likely that the northern bluefin tuna is a dead-end host for P. speciosum.

Reproduction

Female bluefin are thought to produce up to 30 million eggs.

Atlantic bluefin tuna spawn in two widely separated areas. One spawning ground exists in the western Mediterranean, particularly in the area of the Balearic Islands. The other important spawning ground of the Atlantic bluefin is the Gulf of Mexico. Pop-up satellite tracking results appear to confirm in large measure the belief held by many scientists and fishermen that although bluefin that were spawned in each area may forage widely across the Atlantic, they return to the same area to spawn.

Atlantic bluefin group together in large concentrations to spawn, and at such times are highly vulnerable to commercial fishing. This is particularly so in the Mediterranean where the groups of spawning bluefin can be spotted from the air by light aircraft and purse seines directed to set around the schools.

The western and eastern populations of Atlantic bluefin tuna are thought to mature at different ages. It is thought that bluefin born in the east reach maturity a year or two earlier than those spawned in the west.

Threats

The bluefin species is listed by the Monterey Bay Aquarium on its Seafood Watch list and pocket guides as a fish to avoid due to overfishing.

This tuna is one of the most highly-prized fish used in Japanese raw fish dishes. Bluefin tuna sashimi is a particular delicacy in Japan where at one auction, a single giant tuna sold for more than $100,000 (£80,000) on the Tsukiji fish market in Tokyo. The bluefin tuna (including Pacific and Southern fisheries) supports a $7.2 billion industry. In January 2009, a 440 pounds (200 kg) bluefin sold for $173,000. In January 2010, a 232 kilograms (510 lb) bluefin sold for nearly $180,000 at auction in Tokyo, Japan. In January 2011 the 754 pound tuna sold on the Tsukiji fish market in Tokyo for US$396,700 - the highest price for a single fish since records began in 1999. The highest prices in the Japanese market tend to be for Pacific bluefin tuna caught in Japanese waters, but high-grade Atlantic bluefin, particularly from Canada and Boston, also fetch high prices. Prices were highest in the late 1970s and 1980s. Market entry by many North African Mediterranean countries, such as Tunisia and Libya in the 1990s, along with the increasingly widespread practice of tuna farming in the Mediterranean and other areas such as southern Australia (for southern bluefin tuna) depressed prices. One result is that fishermen must now catch up to twice as many fish to maintain their revenues.^{[citation needed]}

Prior to the 1960s, Atlantic bluefin fisheries were relatively small scale, and populations remained stable. Although some local stocks, such as those in the North Sea, were decimated by unrestricted commercial fishing, other populations were not at risk. However, in the 1960s purse seiners catching fish for the canned tuna market in United States coastal waters removed huge numbers of juvenile and young Western Atlantic bluefin, taking out several entire year classes. Mediterranean fisheries have historically been poorly regulated and catches under-reported, with French, Spanish, Italian fishermen competing with North African nations for a diminishing population.^{[citation needed]}

Tuna farming began as early as the 1970s. Canadian fishermen in St Mary's Bay captured young fish and raised them in pens. In captivity, they grow to reach hundreds of kilos, eventually fetching premium prices in Japan. Farming enables farmers to exploit the unpredictable supply of wild-caught fish. Ranches across the Mediterranean and off South Australia grow bluefin offshore. Annual revenues are $220 million. A large proportion of juvenile and young Mediterranean fish are taken to be grown on tuna farms. Because the tuna are taken before they are old enough to reproduce, farming is one of the most serious threats to the species.^{[citation needed]} The bluefin's slow growth and late sexual maturity compound its problems. The Atlantic population has declined by nearly 90 percent since the 1970s.

The 2010 Gulf of Mexico oil spill may threaten the spawning grounds of the bluefin tuna.

Conservation

Overfishing continues despite repeated warnings. In 2007, researchers from the International Commission for the Conservation of Atlantic Tunas (ICCAT)—the regulators of Northern bluefin fishing—recommended a global quota of 15,000 tonnes (15,000 LT/17,000 ST). ICCAT then chose twice that number, later dropping it to 22,500 tonnes (22,100 LT/24,800 ST). Their scientists now say that 7,500 tonnes (7,400 LT/8,300 ST) is the sustainable limit. In November, 2009 ICCAT set the 2010 quota at 13,500 tonnes (13,300 LT/14,900 ST) and said that if stocks were not rebuilt by 2022 it would consider closing some areas. The fishing industry continues to harvest 60,000 tonnes (59,000 LT/66,000 ST) tons yearly.

In 2010, Greenpeace International has added the northern bluefin tuna to its seafood red list. "The Greenpeace International seafood red list is 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."

On March 18, 2010 the United Nations rejected a US-backed effort to impose a total ban on Atlantic Bluefin tuna fishing and trading. The Convention on International Trade in Endangered Species (CITES) vote was 68 to 20 with 30 European abstentions. The leading opponent, Japan, claimed that ICCAT was the proper regulatory body.

Captive breeding

In 2009, aquaculturists succeeded in breeding bluefin in captivity and keeping them alive through their development from larvae to fingerlings to young juveniles.

Culture

The northern bluefin tuna is depicted on the reverse of the Croatian 2 kuna coin, minted since 1993.

References

ISBN links support NWE through referral fees

• Clover, Charles. 2004. The End of the Line: How overfishing is changing the world and what we eat. Ebury Press, London. ISBN 0-09-189780-7
• Hogan, C.Michael. 2010. Overfishing. Encyclopedia of Earth. National Council for Science and the Environment. eds. Sidney Draggan and C.Cleveland. Washington DC.</ref>
• Newlands, Nathaniel K. 2002. Shoaling dynamics and abundance estimation : Atlantic bluefin tuna (Thunnus thynnus). PhD thesis, Resource Management and Environmental Studies/Fisheries Centre, University of British Columbia, Vancouver, Canada. 602pp, https://dspace.library.ubc.ca/handle/2429/13501
• Newlands, N.K., Lutcavage, M. and Pitcher, T. 2006. Atlantic Bluefin Tuna in the Gulf of Maine, I: Estimation of Seasonal Abundance Accounting for Movement, School and School-Aggregation Behaviour. Environmental Biology of Fishes, Volume 77, Number 2 / October, 2006, http://www.springerlink.com/content/v8417th6pnh7k176/
• Newlands, N.K., Lutcavage, M. and Pitcher, T. 2007. Atlantic bluefin tuna in the Gulf of Maine, II: precision of sampling designs in estimating seasonal abundance accounting for tuna behaviour. Environmental Biology of Fishes, Volume 80, Number 4 / December, 2007, 405-420, http://www.springerlink.com/content/33l5754335260608/
• Nathaniel K. Newlands1 , Molly E. Lutcavage2 and Tony J. Pitcher (2004) Analysis of foraging movements of Atlantic bluefin tuna ( Thunnus thynnus): individuals switch between two modes of search behaviour. Population Ecology, Volume 46, Number 1 / April, 2004,39-53, http://www.springerlink.com/content/mhywt3radfc9qlcb/
• Newlands, Nathaniel K., Porcelli Tracy A. (2008) Measurement of the size, shape and structure of Atlantic bluefin tuna schools in the open ocean. Fisheries Research, 2008, vol. 91, no1, pp. 42-55. http://cat.inist.fr/?aModele=afficheN&cpsidt=20301569
• Safina, C. 1993. Bluefin Tuna in the West Atlantic: Negligent Management, and the Making of an Endangered Species. Conservation Biology 7:229-234.
• Safina 1996. [1]. 2006 IUCN Red List of Threatened Species., World Conservation Union. Retrieved on 12 May 2006.
• Safina, C. 1998. "Song For The Blue Ocean." Henry Holt Co. New York.
• Safina, C and D. Klinger. 2008. Collapse of Bluefin Tuna in the Western Atlantic. Conservation Biology 22: 243–246.
• Template:FishBase species
• Scholz, Tomáš; Euzet, Louis & Moravec, František (1998): Taxonomic status of Pelichnibothrium speciosum Monticelli, 1889 (Cestoda: Tetraphyllidea), a mysterious parasite of Alepisaurus ferox Lowe (Teleostei: Alepisauridae) and Prionace glauca (L.) (Euselachii: Carcharinidae). Systematic Parasitology 41(1): 1–8. Digital object identifier (DOI): 10.1023/A:1006091102174 (HTML abstract)

External links

Wikispecies has information related to:

Northern bluefin tuna

• Bye bye bluefin: Managed to death The Economist. 30 October 2008. Retrieved 6 February 2009.
• Template:IUCNlink
• Bluefin Tuna at Seafood Watch
• Tuna at Greenpeace
• MarineBio article on tuna at MarineBio
• Bluefin tuna and Sushi
• brochure on bluefin tuna tagging at Tag-a-Giant Foundation

External links

Wikispecies has information related to:

Thunnus orientalis

• Bye bye bluefin: Managed to death The Economist. 30 October 2008. Retrieved 6 February 2009.
• TOPP, Tagging of Pacific Predators, a research group that tags and tracks the amazing Pacific bluefin tuna to learn more about it. The site features information, photos, blog posts and multimedia stories about the bluefin tuna.

Template:Commercial fish topics

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