Thunnus

True tunas Temporal range: Tertiary–holocene PreЄ Є O S D C P T J K Pg N [1][2]
Yellowfin tuna
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Scombridae
Tribe:	Thunnini
Genus:	Thunnus South, 1845
Subgenus
T. (Thunnus) (bluefin group) T. (Neothunnus) (yellowfin group)

Thunnus is a genus of ocean-dwelling ray-finned bony fish from the Scombridae (Mackerel) family. More specifically, Thunnus is one of five genera which comprise the Thunnini tribe – a tribe that is collectively (and famously) known as the tunas. Also called the true tunas or real tunas, Thunnus consists of eight species of tuna (more than half of the overall tribe), divided into two subgenera. The word Thunnus is the Middle Latin form of the Ancient Greek: θύννος (thýnnos) “tunny-fish” – which is in turn derived from θύνω (thynō), "to rush; to dart".^[3] The first written use of the word was by Homer.^{[citation needed]}

Their coloring, metallic blue on top and shimmering silver-white on the bottom, helps camouflage them from above and below. They can grow to 15 feet long and weigh over 1,000 pounds, and can swim up to 50 miles per hour when pursuing prey. Atlantic bluefin tunas are warm-blooded, which is a rare trait among fish, and are comfortable in the cold waters. Bluefin fish are found in Newfoundland and Iceland, as well as the tropical waters of the Gulf of Mexico and the Mediterranean Sea, where they go each year to spawn.

Due to overfishing the genus range has been significantly reduced, being effectively removed from the Black Sea, for example.^[4]

Taxonomy

Fossil specimen

This genus has eight species in two subgenera:

• Subgenus Thunnus (Thunnus):
  • Albacore, T. alalunga (Bonnaterre, 1788).
  • Southern bluefin tuna, T. maccoyii (Castelnau, 1872).
  • Bigeye tuna, T. obesus (Lowe, 1839).
  • Pacific bluefin tuna, T. orientalis (Temminck & Schlegel, 1844).
  • Atlantic bluefin tuna, T. thynnus (Linnaeus, 1758).
• Subgenus Thunnus (Neothunnus):
  • Yellowfin tuna, T. albacares (Bonnaterre, 1788).
  • Blackfin tuna, T. atlanticus (Lesson, 1831).
  • Longtail tuna, T. tonggol (Bleeker, 1851).

Relative sizes of various tunas, with the Atlantic bluefin tuna (top) at about 8 ft (2.4 m) in this sample

Maximum reported sizes of Thunnus species.

Genus membership

Until recently, it was thought that there were seven Thunnus species, and that Atlantic bluefin tuna and Pacific bluefin tuna were subspecies of a single species. In 1999 Collette established that based on both molecular and morphological considerations, they are in fact distinct species.^[5][6]

The genus Thunnus is further classified into two subgenera: Thunnus (Thunnus) (the bluefin group), and Thunnus (Neothunnus) (the yellowfin group).

Thunnus, the true tunas
Common name	Scientific name	Maximum length	Common length	Maximum weight	Maximum age	Trophic level	Source	IUCN status
Thunnus (Thunnus) – the bluefin group
Albacore tuna	T. alalunga (Bonnaterre, 1788)	1.4 m (4.6 ft)	1.0 m (3.3 ft)	60.3 kg (133 lb)	9–13 yrs	4.31	[7][8]	Near threatened[8]
Southern bluefin tuna	T. maccoyii (Castelnau, 1872)	2.45 m (8.0 ft)	1.6 m (5.2 ft)	260 kg (570 lb)	20–40 yrs	3.93	[9][10]	Critically endangered[10]
Bigeye tuna	T. obesus (Lowe, 1839)	2.5 m (8.2 ft)	1.8 m (5.9 ft)	210 kg (460 lb)	5–16 yrs	4.49	[11][12]	Vulnerable[12]
Pacific bluefin tuna	T. orientalis (Temminck & Schlegel, 1844)	3.0 m (9.8 ft)	2.0 m (6.6 ft)	450 kg (990 lb)	15–26 yrs	4.21	[13][14]	Least concern[14]
Atlantic bluefin tuna	T. thynnus (Linnaeus, 1758)	4.6 m (15 ft)	2.0 m (6.6 ft)	684 kg (1,508 lb)	35–50 yrs	4.43	[15][16]	Endangered[16]
Thunnus (Neothunnus) – the yellowfin group
Blackfin tuna	T. atlanticus (Lesson, 1831)	1.1 m (3.6 ft)	0.7 m (2.3 ft)	22.4 kg (49 lb)		4.13	[17]	Least concern[18]
Longtail tuna	T. tonggol (Bleeker, 1851)	1.45 m (4.8 ft)	0.7 m (2.3 ft)	35.9 kg (79 lb)	18 years	4.50	[19][20]	Data deficient[20]
Yellowfin tuna	T. albacares (Bonnaterre, 1788)	2.4 m (7.9 ft)	1.5 m (4.9 ft)	200 kg (440 lb)	5–9 yrs	4.34	[21][22]	Near threatened[22]

Overfishing

The worldwide demand for sushi and sashimi, coupled with increasing population growth, has resulted in global stocks of the species being overfished^[23] and bluefin is the most endangered and considered "a serious conservation concern".^[24] Complicating the efforts for sustainable management of bluefin fish stocks within national exclusive economic zones (EEZ) is bluefin migrate long distances and hunt in the mid ocean that isn't part of any country's EEZ and therefore have been vulnerable to overfishing by multiple countries' fishing fleets. International agreements and conventions are good faith agreements and are difficult to monitor or enforce.^[25] Though this fish has been farmed in captivity by the Japanese and by the Australians with the help of the Japanese,^[26] yields are lower than other farmed fish due to the slow growth rate of Bluefin tuna, therefore keeping prices high.^[25] On December 30, 2012, a 489-pound (222 kg) bluefin tuna caught off northeastern Japan, was sold at the Tsukiji fish market in Tokyo for a record 155.4 million yen ($1.76 million) – a unit price of JP¥ 1.274 million/kg (US$ 3,600/lb).^[27]

References

Further reading

• Charles Clover. 2004. The End of the Line: How Overfishing Is Changing the World and What We Eat. Ebury Press, London. ISBN 0-09-189780-7
• Newlands, Nathaniel K.; Molly E. Lutcavage, Tony J. Pitcher (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): 177–195. doi:10.1007/s10641-006-9069-5. ISSN 0378-1909.  Cite uses deprecated parameters (help)

External links

Wikimedia Commons has media related to Thunnus.

• Froese, Rainer, and Daniel Pauly, eds. (2006). Species of Thunnus in FishBase. January 2006 version.
• Nutritional benefits of tuna
• The International Commission for the Conservation of Atlantic Tunas

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