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 make up the Thunnini tribe – a tribe that is collectively 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][4] The first written use of the word was by Homer.

Their coloring, metallic blue on top and shimmering silver-white on the bottom, helps camouflage them from above and below. Atlantic bluefin tuna, the largest member of this genus, can grow to 15 feet (4.6 m) long and weigh up to 1,500 pounds (680 kg). All tunas are extremely strong swimmers, and the Yellowfin tuna is known to reach speeds of up to 50 miles per hour (80 km/h) when pursuing prey. As with all tunas, members of this genus are warm-blooded, which is a rare trait among fish; this enables them to tolerate cold waters. Bluefin tunas, for example, are found in Newfoundland and Iceland, and also in the tropical waters of the Gulf of Mexico and the Mediterranean Sea, where some individuals go each year to spawn.

Due to overfishing, the range of this genus has declined significantly, having been effectively removed from the Black Sea, for example.^[5]

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

The True Tunas of the genus Thunnus, within the Family Scombridae

family Scombridae   subfamily Gasterochismatinae   Butterfly kingfishes (1 genus)  subfamily Scombrinae tribe Scombrini   Mackerels (2 genera) tribe Scomberomorini   Spanish Mackerels (3 genera) tribe Sardini   Bonitos (4 genera)  tribe Thunnini Tunas   Allothunnus, slender tunas  Auxis, frigate tunas  Euthynnus, little tunas  Katsuwonus, skipjack tunas  Thunnus, true tunas   subgenus Thunnus  bluefin group  subgenus Neohunnus  yellowfin group

Cladogram: Thunnus (bottom-right in image above) is one of five genera that make up the Thunnini tribe.  Known as the true tunas, it comprises 8 of the 15 extant tuna species.[1]

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.^[6][7]

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	[8][9]	Near threatened[9]
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	[10][11]	Critically endangered[11]
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	[12][13]	Vulnerable[13]
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	[14][15]	Vulnerable[15]
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	[16][17]	Endangered[17]
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	[18]	Least concern[19]
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	[20][21]	Data deficient[21]
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	[22][23]	Near threatened[23]

Overfishing

The worldwide demand for sushi and sashimi, coupled with increasing population growth, has resulted in global stocks of the species being overfished^[24] and bluefin is the most endangered and considered "a serious conservation concern".^[25] 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.^[26] Though this fish has been farmed in captivity by the Japanese and by the Australians with the help of the Japanese,^[27] yields are lower than other farmed fish due to the slow growth rate of Bluefin tuna, therefore keeping prices high.^[26] On December 30, 2012, a 222-kilogram (489 lb) 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).^[28]

References

1. Graham, Jeffrey B.; Dickson, Kathryn A. (2004). "Tuna Comparative Physiology" (PDF). The Journal of Experimental Biology 207: 4015–4024. doi:10.1242/jeb.01267. Retrieved 20 September 2012.
2. Sepkoski, Jack (2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology 364: 560. Retrieved 2008-01-08.
3. θύννος in Liddell, Henry George; Scott, Robert (1940) A Greek–English Lexicon, revised and augmented throughout by Jones, Sir Henry Stuart, with the assistance of McKenzie, Roderick. Oxford: Clarendon Press. In the Perseus Digital Library, Tufts University.
4. θύνω in Liddell and Scott.
5. Hogan, C. Michael, Overfishing. Encyclopedia of Earth. eds. Sidney Draggan and Cutler Cleveland. National council for Science and the Environment, Washington DC
6. Collette, B.B. (1999). "Mackerels, molecules, and morphology". In Séret, B.; Sire, J.Y. Proceedings. 5th Indo-Pacific Fish Conference: Nouméa, New Caledonia, 3–8 November 1997. Paris: Société Française d'Ichtyologie [u.a.] pp. 149–164. ISBN 978-2-9507330-5-4.
7. Tanaka, Y.; Satoh, K.; Iwahashi, M.; Yamada, H. (2006). "Growth-dependent recruitment of Pacific bluefin tuna Thunnus orientalis in the northwestern Pacific Ocean" (PDF). Marine Ecology Progress Series 319: 225–235. doi:10.3354/meps319225.
8. Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus alalunga" in FishBase. January 2012 version.
9. Collette B and 35 others (2011). "Thunnus alalunga". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 January 2015.
10. Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus maccoyii" in FishBase. January 2012 version.
11. Collette B and 8 others (2011). "Thunnus maccoyii". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 January 2015. "This species has been intensively fished since the early 1950s. Its generation length is conservatively estimated to be 12 years. Estimated spawning stock biomass has declined approximately 85% over the past 36 years (1973–2009) and there is no sign that the spawning stock is rebuilding. It is therefore listed as Critically Endangered. Implementation of effective conservation and management measures are urgently needed."
12. Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus obesus" in FishBase. January 2012 version.
13. Collette B and 31 others (2011). "Thunnus obesus". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 January 2015.
14. Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus orientalis" in FishBase. January 2012 version.
15. Collette B and 6 others (2014). "Thunnus orientalis". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 January 2015.
16. Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus thynnus" in FishBase. January 2012 version.
17. Collette B and 23 others (2011). "Thunnus thynnus". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 January 2015.
18. Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus atlanticus" in FishBase. January 2012 version.
19. Collette B and 18 others (2011). "Thunnus atlanticus". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 January 2015.
20. Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus tonggol" in FishBase. January 2012 version.
21. Collette B and 7 others (2011). "Thunnus tonggol". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 January 2015.
22. Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus albacares" in FishBase. January 2012 version.
23. Collette B and 35 others (2011). "Thunnus albacares". IUCN Red List of Threatened Species. Version 2014.3. International Union for Conservation of Nature. Retrieved 9 January 2015.
24. George Karleskint, Richard Turner, James Small (2009). Introduction to Marine Biology. Cengage Learning. p. 522. ISBN 0-495-56197-5.
25. "Tuna, Bluefin".
26. "Managed to death". The Economist. 2008-10-30.
27. Thunnus orientalis#Farming
28. "A bluefin tuna sells for record $1.76M in Tokyo". USA Today. 4 January 2013. Retrieved 5 January 2013.

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.

External links

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