Atlantic bluefin tuna
Atlantic bluefin tuna | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Actinopterygii |
Order: | Scombriformes |
Family: | Scombridae |
Genus: | Thunnus |
Subgenus: | Thunnus |
Species: | T. thynnus
|
Binomial name | |
Thunnus thynnus | |
Synonyms[2] | |
Scomber thynnus Linnaeus, 1758 |
The Atlantic bluefin tuna (Thunnus thynnus) is a species of tuna in the family Scombridae. It is variously known as the northern bluefin tuna (mainly when including Pacific bluefin as a subspecies), giant bluefin tuna [for individuals exceeding 150 kg (330 lb)], and formerly as the tunny.
Atlantic bluefins are native to both the western and eastern Atlantic Ocean, as well as the Mediterranean Sea. They have become extinct in the Black 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 have been recorded at up to 680 kg (1,500 lb) in weight, and rival the
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 affirmed in October 2009 that Atlantic bluefin tuna stocks had declined dramatically over the last 40 years, by 72% in the Eastern Atlantic, and by 82% in the Western Atlantic.[3] On 16 October 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.[4] However, a UN proposal to protect the species from international trade was voted down (68 against, 20 for, 30 abstaining).
Most bluefins are captured commercially by professional fishermen using
Taxonomy
The Atlantic bluefin tuna was one of the many fish species originally described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae, where it was given the binomial name Scomber thynnus.[8]
It is most closely related to the Pacific bluefin tuna (T. orientalis) and the southern bluefin tuna (T. maccoyii), and more distantly to the other large tunas of the genus This is also true in New Zealand and Fiji.
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 atún, 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 red color of the bluefin's meat is included in its name, as in atún rojo (Spanish) and tonno rosso (Italian), amongst others.
Description
The body of the Atlantic bluefin tuna is rhomboidal in profile and robust. The head is conical and the mouth rather large. The head contains a
Fully mature adult specimens average 2–2.5 m (6.6–8.2 ft) long and weigh around 225–250 kg (496–551 lb).[13][14] The largest recorded specimen taken under International Game Fish Association rules was caught off Nova Scotia, an area renowned for huge Atlantic bluefin, and weighed 679 kg (1,497 lb) and was 3.84 m (12.6 ft) long.[15][16] The longest contest between man and tuna fish occurred near Liverpool, Nova Scotia in 1934, when six men taking turns fought a 164–363 kilograms (361–800 lb) tuna for 62 hours.[17] Both the Smithsonian Institution and the U. S. National Marine Fisheries Service have accepted that this species can weigh up to 910 kg (2,010 lb), though further details are lacking.[14][18] Atlantic bluefin tuna reach maturity relatively quickly. In a survey that included specimens up to 2.55 m (8.4 ft) in length and 247 kg (545 lb) in weight, none was believed to be older than 15 years.[19] However, very large specimens may be up to 50 years old.[19]
The bluefin possesses enormous muscular strength, which it channels through a pair of tendons to its lunate-shaped caudal fin for propulsion. In contrast to many other fish, the body stays rigid while the tail flicks back and forth, increasing stroke efficiency.[20] It also has a very efficient circulatory system. It possesses one of the highest blood-hemoglobin concentrations among fish, which allows it to efficiently deliver oxygen to its tissues; this is combined with an exceptionally thin blood-water barrier to ensure rapid oxygen uptake.[21]
To keep its core muscles warm, which are used for power and steady swimming, the Atlantic bluefin uses
Biology and ecology
Bluefins dive to depths of 1,006 m (3,301 ft).[22][23] The Atlantic bluefin tuna typically hunts small fish such as sardines, herring, mackerel, and eels, and invertebrates such as squid and crustaceans.[24] They exhibit opportunistic hunting in schools of fish organised by size. Their white skeletal muscle allows for large contractions which aids burst swimming to ensure prey capture.
The species is host to over 70
Atlantic bluefin tuna are eaten by a wide variety of predators. When they are newly hatched, they are eaten by other fishes that specialize on eating plankton. At that life stage, their numbers are reduced dramatically. Those that survive face a steady increase in the size of their predators. Adult Atlantic Bluefin are not eaten by anything other than the very largest billfishes, toothed whales, and some open ocean shark species.[26]
Life history
Bluefin tuna are oviparous, congregating together in large groups to spawn. Over several days, a female releases large numbers of eggs into the water where they are fertilized externally by male sperm. Female bluefins have been estimated to produce a mean of 128.5 eggs per gram of body weight, or up to 40 million eggs at a time. Eggs hatch into larvae two days after fertilization and become cannibalistic quarter-inch long fish by the end of a week. About 40% of larvae survive their first week, and about 0.1% the first year. Surviving bluefin tend to group together in schools according to size.[27]
Atlantic bluefin tuna were traditionally known to spawn in two widely separated areas. Pop-up satellite tracking results generally confirm the belief held by many scientists and fishermen that although bluefin that were spawned in each area may forage widely across the Atlantic, the vast majority return to their natal area to spawn.[28] The Eastern stock of Atlantic bluefins' spawning ground exists in the western
In 2016, researchers suggested that a third spawning area exists in the Slope Sea, an area to the north and west of the Northeastern United States Continental Shelf. Subsequent research indicates that comparable concentrations of bluefin larvae are found in the Slope Sea and in the Gulf of Mexico.[30][31]
A number of behavioral differences have been observed between the eastern and western populations, some of which may reflect environmental conditions. For example, bluefin in the Gulf of Mexico spawn between mid-April and mid-June, when the surface water temperature is between 75 °F (24 °C) and 85 °F (29 °C), while bluefin in the Mediterranean spawn between June and August, when water is between 65 °F (18 °C) and 70 °F (21 °C).[32] In the Gulf of Mexico bluefin appear to correct for higher surface temperatures by diving, going deeper than 500 metres (1,600 ft) when entering the Gulf and staying deeper than 200 metres (660 ft) to spawn.[33]
The western and eastern populations have been thought to mature at different ages. Bluefins born in the east are thought to reach maturity a year or two earlier than those spawned in the west.[34][23] It has also been suggested that these apparent differences may reflect not-well-understood complexities of migration patterns[35] and additional spawning areas such as the Slope Sea.[34]
Human interaction
Ancient fishery
According to Longo, "by the turn of the first millennium CE, a sophisticated bluefin tuna trap fishery [had] emerged. ... This trap fishery, called tonnara in Italian, madrague in French, almadraba in Spanish, and armação in Portuguese, forms an elaborate maze of nets that capture and corral bluefin tuna during their spawning season. Active for more than a thousand years, the traditional/artisanal bluefin tuna trap fishery has experienced a collapse in the Mediterranean and has struggled where it is still practiced."[36]
Commercial fishery
After World War II, Japanese fishermen needed more tuna to eat and to export for European and U.S. canning industries. They expanded their fishing range and perfected industrial long-line fishing, a practice that employs thousands of baited hooks on miles-long lines. In the 1970s, Japanese manufacturers developed lightweight, high-strength polymers that were spun into
The initial target was yellowfin tuna. Japanese did not value bluefin before the 1960s. By the late 1960s,
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 damaged 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 bluefins, taking out several entire-year classes. Mediterranean fisheries have historically been poorly regulated and catches under-reported, with French, Spanish, and Italian fishermen competing with North African nations for a diminishing population.[citation needed] The fish's migratory habits complicate the task of regulating the fishery, because they spend time in the national waters of multiple countries, as well as the open ocean outside of any national jurisdiction.[12]
Aquaculture
Tuna ranching 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. Ranching enables ranchers to exploit the unpredictable supply of wild-caught fish. Ranches across the Mediterranean and off South Australia grow bluefins offshore. According to OECD statistics, 35 thousand tons have been produced in 2018 with Japan accounting for about 50% of it, followed by Australia, Mexico, Spain and Turkey with smaller amounts.[37] Large proportions of juvenile and young Mediterranean fish are taken to be grown on tuna farms. Because the tuna are taken from the wild to the pens before they are old enough to reproduce, ranching 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% since the 1970s.[38]
In Europe and Australia, scientists have used light-manipulation technology and time-release hormone implants to bring about the first large-scale captive spawning of Atlantic and southern bluefins.[12] The technology involves implanting gonadotropin-releasing hormone in the fish to stimulate fertile egg production and may push the fish to reach sexual maturity at younger ages.[39]
However, since bluefins require so much food per unit of weight gained - up to 10 times that of salmon - if bluefins were to be farmed at the same scale as 21st-century salmon farming, many of their prey species might become depleted if farmed bluefin were fed the same diet as their wild counterparts. As of 2010, 30 million tons of small forage fish were removed from the oceans yearly, the majority to feed farmed fish.[12]
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] The Atlantic bluefin is endangered.
Threats
Global appetite for fish is the predominant threat to Atlantic bluefin. Overfishing continues despite repeated warnings of the current precipitous decline. Bluefin aquaculture, which arose in response to declining wild stocks, has yet to achieve a sustainability, in part because it predominantly relies on harvesting and ranching juveniles rather than captive breeding.
The 2010 Deepwater Horizon oil spill released an estimated 4.9 million barrels of crude oil into the Gulf of Mexico during the spawning season of the Atlantic bluefin tuna. The oil is estimated to have affected roughly 3.1 million square miles, including more than 5 percent of the tuna habitat in the U.S. Exclusive Economic Zone. The spill occurred at a peak time for the fertilization of eggs and the development of larval bluefin tuna. Resulting short and long-term impacts on populations of Atlantic bluefin tuna and other pelagic species are difficult to determine, in part due to limitations in monitoring ability.[40] [41][42] Nonetheless, a number of lethal and sublethal impacts have been documented, including pericardial edema, defective cardiac function and cardiac abnormalities.[43]
Conservation
Fisheries management organizations
In 2007, researchers from the International Commission for the Conservation of Atlantic Tunas (ICCAT) — the regulators of Atlantic bluefin fishing—recommended a global quota of 15,000 tonnes to maintain current stocks or 10,000 tonnes to allow the fisheries recovery. ICCAT then chose a quota of 36,000 tonnes, but surveys indicated that up to 60,000 tonnes were actually being taken (a third of the total remaining stocks) and the limit was reduced to 22,500 tonnes. Their scientists now say that 7,500 tonnes are the sustainable limit. In November 2009, ICCAT set the 2010 quota at 13,500 tonnes and said that if stocks were not rebuilt by 2022, it would consider closing some areas.[5]
On 18 March 2010, the United Nations rejected a U.S.-backed effort to impose a total ban on Atlantic bluefin tuna fishing and trading.
In 2011, the USA's
In November 2012, 48 countries meeting in Morocco for the International Commission for the Conservation of Atlantic Tunas voted to keep strict fishing limits, saying the species' population is still fragile. The quota will rise only slightly, from 12,900 metric tons a year to 13,500.[47] The decision was reviewed in November 2014, resulting in higher allowances listed below.
The latest stock assessment for Atlantic bluefin tuna reflected an improvement in the status for both western and eastern Atlantic/Mediterranean stocks. The Commission adopted new management measures that are within the range of scientific advice, are consistent with the respective rebuilding plans, and allow for continued stock growth. For the western stock, the TAC of 2,000 mt annually for 2015 and 2016 will provide for continued growth in spawning stock biomass and allow the strong 2003 year-class to continue to enhance the productivity of the stock. The TAC for the eastern Atlantic/Mediterranean stock was set at 16,142 t for 2015; 19,296 t for 2016; and 23,155 t for 2017.[48]
In 2020, the UK government recognised the increasing incidence of bluefin tuna in UK waters in recent years and is funding ongoing research to understand the ecology of the species and devise an approach to its management.[49][50]
Other organizations
In 2010,
In the summer of 2011, the Sea Shepherd Conservation Society led a campaign against supposedly illegal bluefin tuna fishing off the coast of Libya, which was under Muammar Gaddafi's regime at the time. The fishermen retaliated against Sea Shepherd's intervention by throwing various, small metal pieces at the crew. Nobody was injured due to the other side's actions during the conflict.[53]
In November 2011, food critic Eric Asimov of The New York Times criticized the top-ranked New York City restaurant Sushi Yasuda for offering bluefin tuna on their menu, arguing that drawing from such a threatened fishery constituted an unjustifiable risk to bluefins, and to the future of culinary traditions that depend on the species.[54]
The bluefin species are listed by the Monterey Bay Aquarium on its Seafood Watch list and pocket guides as fish to avoid due to overfishing.[55]
Cuisine
Atlantic bluefin tuna is one of the most highly prized fish used in Japanese raw fish dishes. About 80% of the caught Atlantic and Pacific bluefin tunas are consumed in Japan.[56] Bluefin tuna sashimi is a particular delicacy in Japan. For example, an Atlantic bluefin caught off eastern United States sold for US$247,000 at the Tsukiji fish market in Tokyo in 2008.[57] This high price is considerably less than the highest prices paid for Pacific bluefin.[56][57] Prices were highest in the late 1970s and 1980s.[citation needed]
Japanese began eating tuna sushi in the 1840s, when a large catch came into Edo [old Tokyo] one season. A chef marinated a few pieces in soy sauce and served it as nigiri sushi. At that time, these fish were nicknamed shibi — "four days" — because chefs would bury them for four days to mellow their bloody taste.[12]
Originally, fish with red flesh were looked down on in Japan as a low-class food, and white fish were much preferred. ... Fish with red flesh tended to spoil quickly and develop a noticeable stench, so in the days before refrigeration, the Japanese aristocracy despised them, and this attitude was adopted by the citizens of Edo. – Michiyo Murata[12]
By the 1930s, tuna sushi was commonplace in Japan.
See also
References
- . Retrieved 19 November 2021.
- ^ "Thunnus thynnus (Linnaeus, 1758)". Integrated Taxonomic Information System. Retrieved 9 December 2012.
- ^ "Endangered Atlantic bluefin tuna formally recommended for international trade ban". October 2009. Retrieved 17 October 2009.
- ^ Jolly, David (3 February 2010). "Europe Leans Toward Bluefin Trade Ban". The New York Times.
- ^ a b c Jolly, David; Broder, John M. (18 March 2010). "U.N. Rejects Export Ban on Atlantic Bluefin Tuna". New York Times. Retrieved 19 March 2010.
- ^ Collette, B.B.; Wells, D. & Abad-Uribarren, A. (2015). "Thunnus thynnus (Gulf of Mexico assessment)". IUCN Red List of Threatened Species. 2015: e.T21860A76599358. Retrieved 23 August 2023.
- ^ "Tuna species recovering despite growing pressures on marine life - IUCN Red List". IUCN. 4 September 2021. Retrieved 6 June 2022.
- ^ Linnaeus, Carl (1758). Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis (in Latin). Vol. I (10th revised ed.). Holmiae: (Laurentii Salvii). p. 297.
- ^ a b Collette, B.B. (1999). Mackerels, molecules, and morphology. In: Proceedings of the 5th Indo-Pacific Fish Conference, Noumea. pp. 149–164
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- ^ a b c d e f g h i Greenberg, Paul (27 June 2010). "Tuna's End". The New York Times. p. 28.
- ^ The Atlantic Bluefin Tuna Archived 1 June 2012 at the Wayback Machine. Outdoor.se (31 July 1926). Retrieved on 2013-05-04.
- ^ a b Atlantic Bluefin Tuna (Thunnus thynnus). Nmfs.noaa.gov. Retrieved on 4 May 2013.
- ^ "Tuna, bluefin (Thunnus thynnus) - All-Tackle World Records". igfa.org. Retrieved 5 January 2023.
- ^ Collette, Bruce B.; Nauen, Cornelia E. (1983). Fao Species Catalogue. Vol. 2 Scombrids of the World: An Annotated and Illustrated Catalogue of Tunas, Mackerels, Bonitos, and Related Species Known to Date (PDF). Rome: UNDP/FAO. p. 92.
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- ^ "Thunnus thynnus (Horse mackerel)". Animal Diversity Web.
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- ^ "Atlantic Bluefin Tuna". Oceana. Retrieved 27 March 2023.
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- ^ Woods Hole Oceanographic Institution (4 March 2022). "Evidence bolsters classification of a major spawning ground for Atlantic bluefin tuna off the northeast U.S." phys.org. Retrieved 7 June 2022.
- ^ "Searching for Atlantic bluefin tuna larvae and more in the Slope Sea". Field Fresh. 15 June 2017. Retrieved 7 June 2022.
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- ^ Shwartz, Mark; Peterson, Ken (25 April 2005). "Migration study concludes that sweeping management changes are needed to protect Atlantic bluefin tuna". Stanford News Release. Retrieved 7 June 2022.
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- ^ "Breeding the Overfished Bluefin Tuna". LiveScience. 17 March 2008. Retrieved 13 February 2012.
- ^ "Deepwater Horizon oil spill impacted bluefin tuna spawning habitat in Gulf of Mexico, Stanford and NOAA researchers find". Stanford News. 30 September 2016. Retrieved 6 June 2022.
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- ^ Black, Richard (18 March 2010). "Bluefin tuna ban proposal meets rejection". BBC News. Archived from the original on 25 March 2010. Retrieved 13 April 2010.
- ^ Harris, Richard (27 May 2011). "Sorry, Charlie! Better Luck Next Time Getting Endangered Species Status". NPR. Retrieved 30 May 2011.
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- ^ "Bluefin tuna quotas remain in place". 3 News NZ. 20 November 2012.
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- ^ a b Washington Post (5 January 2011). Swank sushi: Bluefin tuna nets $736,000 at Tokyo auction, easily beating old record.[dead link] Accessed 6 January 2011
- ^ a b NBC News (1 January 2009). Premium tuna fetches $100,000 at auction. Accessed 6 January 2011
Further reading
- Clover, Charles (2004). ISBN 0-09-189780-7
- Hogan, C. Michael. (2010). "Overfishing". Encyclopedia of Earth. National Council for Science and the Environment. eds. Sidney Draggan & C. Cleveland. Washington DC.
- 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,
- Newlands, N. K.; Lutcavage, M. & Pitcher, T. (October 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. 77 (2).
- Newlands, N. K.; Lutcavage, M. & Pitcher, T. (December 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. 80 (4): 405–420.
- Newlands, Nathaniel K.; Lutcavage, Molly E. & Pitcher, Tony J. (April 2004). "Analysis of foraging movements of Atlantic bluefin tuna (Thunnus thynnus): individuals switch between two modes of search behaviour". Population Ecology. 46 (1): 39–53.
- 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. 91 (1): 42–55.
- Safina, C. (1993). "Bluefin Tuna in the West Atlantic: Negligent Management, and the Making of an Endangered Species". Conservation Biology. 7: 229–234.
- Safina, C. (1998). Song For The Blue Ocean. Henry Holt Co. New York.
- Safina, C. & Klinger, D. (2008). "Collapse of Bluefin Tuna in the Western Atlantic". Conservation Biology. 22: 243–246.
- Froese, Rainer; Pauly, Daniel (eds.) (2006). "Thunnus thynnus" in FishBase. January 2006 version.
External links
- Media related to Thunnus thynnus at Wikimedia Commons
- Bye bye bluefin: Managed to death The Economist. 30 October 2008. Retrieved 2009-02-06.
- 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