Thunnus
| True tunas | |
|---|---|
| File:Yellowfin tuna nurp.jpg | |
| Yellowfin tuna | |
| Scientific classification Edit this classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Scombriformes |
| Family: | Scombridae |
| Tribe: | Thunnini |
| Genus: | Thunnus South, 1845 |
| Type species | |
| Scomber thynnus Linnaeus, 1758
| |
| Subgenus | |
| |
| Synonyms | |
| |
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
[edit | edit source]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 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:
- 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)
| The true tunas of the genus Thunnus, within the family Scombridae |
|
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| 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] |
| Alternative evolutionary tree for Thunnus |
|
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| An alternative phylogenetic reconstruction for the genus Thunnus, based on nuclear DNA sequence data, which modifies the traditionally recognized bluefin and yellowfin clades by placing Thunnus obesus within the yellowfin clade instead of in the bluefin clade.[8] |
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Species
[edit | edit source]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]
Thunnus, the true tunas Image Common name Scientific name Maximum
lengthCommon
lengthMaximum
weightMaximum
ageTrophic
levelSource IUCN status Thunnus (Thunnus) – the bluefin group File:Thunnus alalunga Ford.jpg Albacore tuna T. alalunga
(Bonnaterre, 1788)Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 9–13 yrs 4.31 [13][14] LC IUCN 3 1.svg Least Concern[14] File:Thmac u0.gif Southern bluefin tuna T. maccoyii
(Castelnau, 1872)Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 20–40 yrs 3.93 [15][16] EN IUCN 3 1.svg Endangered[16] File:Thunnus obesus.png Bigeye tuna T. obesus
(Lowe, 1839)Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 5–16 yrs 4.49 [17][18] VU IUCN 3 1.svg Vulnerable[18] File:Bluefin tuna.jpg Pacific bluefin tuna T. orientalis
(Temminck & Schlegel, 1844)Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 15–26 yrs 4.21 [19][20] NT IUCN 3 1.svg Near Threatened[20] File:Bluefin-big.jpg Atlantic bluefin tuna T. thynnus
(Linnaeus, 1758)Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 35–50 yrs 4.43 [21][22] LC IUCN 3 1.svg Least Concern[22] Thunnus (Neothunnus) – the yellowfin group File:Blackfin tuna, Duane Raver Jr.jpg Blackfin tuna T. atlanticus
(Lesson, 1831)Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 4.13 [23] LC IUCN 3 1.svg Least concern[24] File:Thunnus tonggol.jpg Longtail tuna,
northern bluefin tuna,
tongol tunaT. tonggol
(Bleeker, 1851)Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 18 years 4.50 [25][26] DD IUCN 3 1.svg Data deficient[26] File:Thunnus albacares.png Yellowfin tuna T. albacares
(Bonnaterre, 1788)Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. Lua error: Internal error: The interpreter exited with status 1. 5–9 yrs 4.34 [27][28] LC IUCN 3 1.svg Least Concern[28]
Overfishing
[edit | edit source]The worldwide demand for sushi and sashimi, coupled with increasing population growth, has resulted in global stocks of the species being overfished[29] and bluefin is the most endangered and considered "a serious conservation concern".[30] 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.[31] Though this fish has been farmed in captivity by the Japanese and by the Australians with the help of the Japanese,[32] yields are lower than other farmed fish due to the slow growth rate of bluefin tuna, therefore keeping prices high.[31] On December 30, 2012, a Lua error: Internal error: The interpreter exited with status 1. 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).[33]
References
[edit | edit source]- ^ a b Lua error: Internal error: The interpreter exited with status 1.
- ^ Lua error: Internal error: The interpreter exited with status 1.
- ^ Lua error: Internal error: The interpreter exited with status 1.
- ^ Hogan, C. Michael, Overfishing. Encyclopedia of Earth. eds. Sidney Draggan and Cutler Cleveland. National council for Science and the Environment, Washington DC
- ^ Lua error: Internal error: The interpreter exited with status 1. 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.
- ^ Lua error: Internal error: The interpreter exited with status 1. in Liddell and Scott.
- ^ Lua error: Internal error: The interpreter exited with status 1.
- ^ a b c Lua error: Internal error: The interpreter exited with status 1.
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- ^ a b Lua error: Internal error: The interpreter exited with status 1.
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- ^ Lua error: Internal error: The interpreter exited with status 1.
- ^ Lua error: Internal error: The interpreter exited with status 1.
- ^ a b Lua error: Internal error: The interpreter exited with status 1.
- ^ Thunnus orientalis#Farming
- ^ Lua error: Internal error: The interpreter exited with status 1.
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Further reading
[edit | edit source]- Charles Clover. 2004. The End of the Line: How Overfishing Is Changing the World and What We Eat. Ebury Press, London. Lua error: Internal error: The interpreter exited with status 1.
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External links
[edit | edit source]Lua error: Internal error: The interpreter exited with status 1.
- Lua error: Internal error: The interpreter exited with status 1.
- Nutritional benefits of tuna Lua error: Internal error: The interpreter exited with status 1.
- The International Commission for the Conservation of Atlantic Tunas
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