This article is about the genus. For the subgenus, see Thunnus (Thunnus).
Main article: Tuna
True tunas
Fossil range[1][2]
TaxonThunnus
AuthoritySouth, 1845
Type speciesScomber thynnus
Type species authorityLinnaeus, 1758
Subdivision ranksSubgenera
Subdivision
Synonyms
  • Albacora Jordan, 1888
  • Germo Jordan, 1888
  • Thynnus Aguilera, 2020
  • Kishinoella Jordan & Hubbs, 1925
  • Neothunnus Kishinouye, 1923
  • Orcynus Cuvier, 1816
  • Parathunnus Kishinouye, 1923
  • Semathunnus Fowler, 1933

Thunnus is a genus of ocean-dwelling, ray-finned bony fish from the mackerel family, Scombridae. More specifically, Thunnus is one of five genera which make up the tribe Thunnini – 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.

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, muscular 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 and to dive to deeper depths.[3] 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 extirpated from the Black Sea, for example.[4]

Taxonomy

The word Thunnus is the Middle Latin form of the Greek thýnnos (θύννος, "tuna, tunny") – which is in turn derived from thynō (θύνω, "to rush; to dart").[5][6] The first known written use of the word was by Homer.[citation needed]

Based on morphology and short-length mitochondrial DNA sequence data,[7] the genus Thunnus is currently classified into two subgenera: Thunnus (Thunnus) (the bluefin group), and Thunnus (Neothunnus) (the yellowfin group). However this classification has been questioned by a recent phylogenetic analysis of nuclear DNA sequence data, which resolved different relationships among species and did not support the traditional definition of the bluefin and yellowfin groups.[8][9] Specifically, these analyses substantiated the division of Pacific and Atlantic Tuna in two separate species and suggested that Bigeye Tuna were actually a member of subgenus Neothunnus, not subgenus Thunnus.[8] Earlier nuclear ribosomal DNA phylogenetic reconstructions also showed similar results.[10]

This genus has eight species in two subgenera:

Species

Until recently, seven Thunnus species were thought to exist, and 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.[11][12]

|}

Overfishing

The worldwide demand for sushi and sashimi, coupled with increasing population growth, has resulted in global stocks of the species being overfished[13] and bluefin is the most endangered and considered "a serious conservation concern".[14] 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 midocean that is not part of any country's EEZ, so 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.[15] Though this fish has been farmed in captivity by the Japanese and by the Australians with the help of the Japanese,[16] yields are lower than other farmed fish due to the slow growth rate of bluefin tuna, therefore keeping prices high.[15] On December 30, 2012, a 222-kilogram (489-pound) 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).[17]

References

  1. ^ Graham, Jeffrey B. & Dickson, Kathryn A. (2004). "Tuna Comparative Physiology". The Journal of Experimental Biology. 207 (23): 4015–4024. Bibcode:2004JExpB.207.4015G. doi:10.1242/jeb.01267. PMID 15498947
  2. ^ Sepkoski, Jack (2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology. 364: 560. Archived from the original on 2011-07-23. Retrieved 2008-01-08.
  3. ^ Bernal, Diego; Brill, Richard W.; Dickson, Kathryn A.; Shiels, Holly A. (2017-12-01). "Sharing the water column: physiological mechanisms underlying species-specific habitat use in tunas". Reviews in Fish Biology and Fisheries. 27 (4): 843–880. Bibcode:2017RFBF...27..843B. doi:10.1007/s11160-017-9497-7. ISSN 1573-5184. S2CID 20554689. Archived 2020-06-17 at the Wayback Machine. Retrieved 2019-12-01.
  4. ^ Hogan, C. Michael, Overfishing. Encyclopedia of Earth. eds. Sidney Draggan and Cutler Cleveland. National council for Science and the Environment, Washington DC
  5. ^
  6. ^ .
  7. ^ Alvarado Bremer, J.R.; Naseri, I.; Ely, B. (2016). "ROrthodox and unorthodox phylogenetic relationships among tunas revealed by the nucleotide sequence analysis of the mitochondrial DNA control region". Journal of Fish Biology. 50 (3): 540–554. doi:10.1111/j.1095-8649.1997.tb01948.x
  8. ^ Díaz-Arce, Natalia; Arrizabalaga, Haritz; Murua, Hilario; Irigoien, Xabier; Rodríguez-Ezpelata, Naiara (2016). "RAD-seq derived genome-wide nuclear markers resolve the phylogeny of tunas". Molecular Phylogenetics and Evolution. 102: 202–207. Bibcode:2016MolPE.102..202D. doi:10.1016/j.ympev.2016.06.002. hdl:10754/612968. PMID 27286653
  9. ^ Ciezarek, Adam G.; Osborne, Owen G.; Shipley, Oliver N.; Brooks, Edward J.; Tracey, Sean R.; McAllister, Jaime D.; Gardner, Luke D.; Sternberg, Michael J. E.; Block, Barbara; Savolainen, Vincent (2019-01-01). "Phylotranscriptomic Insights into the Diversification of Endothermic Thunnus Tunas". Molecular Biology and Evolution. 36 (1): 84–96. doi:10.1093/molbev/msy198. ISSN 0737-4038. PMC 6340463. PMID 30364966
  10. ^ Chow, S.; Nakagawa, T.; Suzuki, N.; Takeyama, H.; Matsunaga, T. (2006). "Phylogenetic relationships among Thunnus species inferred from rDNA ITS1 sequence". Journal of Fish Biology. 68 (A): 24–35. Bibcode:2006JFBio..68...24C. doi:10.1111/j.0022-1112.2006.00945.x
  11. ^ Collette, B.B. (1999). Mackerels, molecules, and morphology. 5th Indo-Pacific Fish Conference: Nouméa, New Caledonia, 3–8 November 1997. Séret, B. & Sire, J.Y. (eds.). Paris: Société Française d'Ichtyologie [u.a.] pp. 149–164. ISBN 978-2-9507330-5-4. Archived 2023-11-30 at the Wayback Machine. Retrieved 2017-09-16.
  12. ^ 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. Bibcode:2006MEPS..319..225T. doi:10.3354/meps319225
  13. ^ George Karleskint; Richard Turner; James Small (2009). Introduction to Marine Biology. Cengage Learning. p. 522. ISBN 978-0-495-56197-2.
  14. ^ "Tuna, Bluefin". Archived from the original on 2011-07-22.
  15. ^ "Managed to death". The Economist. 2008-10-30. Archived 2011-02-11 at the Wayback Machine. Retrieved 2011-01-08.
  16. ^ Thunnus orientalis#Farming
  17. ^ "A bluefin tuna sells for record $1.76M in Tokyo". USA Today. 4 January 2013. Archived 28 July 2018 at the Wayback Machine. Retrieved 5 January 2013.

Further reading