Thunnus

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Main article: Tuna
True tunas
Temporal range: Tertiary–holocene
[1][2]
Yellowfin tuna nurp.jpg
Yellowfin tuna
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Scombridae
Tribe: Thunnini
Genus: Thunnus
South, 1845
Subgenus

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[edit]

Fossil specimen

This genus has eight species in two subgenera:

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[edit]

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] NT IUCN 3 1.svg 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] CR IUCN 3 1.svg 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] VU IUCN 3 1.svg 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] LC IUCN 3 1.svg 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] EN IUCN 3 1.svg 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] LC IUCN 3 1.svg 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] DD IUCN 3 1.svg 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] NT IUCN 3 1.svg Near threatened[22]

Overfishing[edit]

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[edit]

  1. ^ a b 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: p.560. Retrieved 2008-01-08. 
  3. ^ Liddell, H.G.; Scott, R.; Whiton, J.M. (1887). A lexicon abridged from Liddell and Scott's Greek-English lexicon (17th ed.). Ginn & Co. 
  4. ^ Hogan, C. Michael, Overfishing. Encyclopedia of Earth. eds. Sidney Draggan and Cutler Cleveland. National council for Science and the Environment, Washington DC
  5. ^ Collette, B.B. (1999). Séret, B.; Sire, J.Y., ed. "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.  |chapter= ignored (help)
  6. ^ Tanaka, Y.; Satoh, K.; Iwahashi, M.; Yamada, H. (2006). "Growth-dependent recruitment of Pacific bluefin tuna Thunnus orientalis in the northwestern Pacific Ocean". Marine Ecology Progress Series 319: 225–235. doi:10.3354/meps319225. 
  7. ^ Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus alalunga" in FishBase. January 2012 version.
  8. ^ a b Collette B and 35 others (2011). "Thunnus alalunga". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 October 2012. 
  9. ^ Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus maccoyii" in FishBase. January 2012 version.
  10. ^ a b Collette B and 8 others (2011). "Thunnus maccoyii". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 October 2012. 
  11. ^ Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus obesus" in FishBase. January 2012 version.
  12. ^ a b Collette B and 31 others (2011). "Thunnus obesus". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 October 2012. 
  13. ^ Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus orientalis" in FishBase. January 2012 version.
  14. ^ a b Collette B and 35 others (2011). "Thunnus orientalis". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 October 2012. 
  15. ^ Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus thynnus" in FishBase. January 2012 version.
  16. ^ a b Collette B and 23 others (2011). "Thunnus thynnus". IUCN Red List of Threatened Species. Version 2012.2. International Union for Conservation of Nature. Retrieved 18 October 2012. 
  17. ^ Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus atlanticus" in FishBase. January 2012 version.
  18. ^ Collette B and 18 others (2011). "Thunnus atlanticus". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. Retrieved 18 September 2012. 
  19. ^ Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus tonggol" in FishBase. January 2012 version.
  20. ^ a b Collette B and 7 others (2011). "Thunnus tonggol". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. Retrieved 18 September 2012. 
  21. ^ Froese, Rainer and Pauly, Daniel, eds. (2012). "Thunnus albacares" in FishBase. January 2012 version.
  22. ^ a b Collette B and 35 others (2011). "Thunnus albacares". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. Retrieved 18 September 2012. 
  23. ^ George Karleskint, Richard Turner, James Small (2009). Introduction to Marine Biology. Cengage Learning. p. 522. ISBN 0-495-56197-5. 
  24. ^ "Tuna, Bluefin". 
  25. ^ a b "Managed to death". The Economist. 2008-10-30. 
  26. ^ Thunnus orientalis#Farming
  27. ^ "A bluefin tuna sells for record $1.76M in Tokyo". USA Today. 4 January 2013. Retrieved 5 January 2013. 

Further reading[edit]

External links[edit]