Tuna (: tunas or tuna) are saltwater fish belonging to the tribe Thunnini, a subgrouping of the Scombridae (mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary from the bullet tuna (max length: , weight: ) to the Atlantic bluefin tuna (max length: , weight: ), which averages and is believed to live up to 50 years.
Tuna, opah, and mackerel sharks are the only species of fish that can maintain a body temperature higher than that of the surrounding water. An active and agile predator, the tuna has a sleek, streamlined body, and is among the fastest-swimming pelagic fish — the yellowfin tuna, for example, is capable of speeds of up to .
Found in warmer seas, the tuna is commercially fished extensively as a food fish, and is popular as a bluewater game fish. As a result of overfishing, some tuna species, such as the southern bluefin tuna, are threatened with extinction.
Etymology The term "tuna" comes from Spanish atún < Andalusian Arabic at-tūn, assimilated from al-tūn [Modern Arabic ]: 'tuna fish' < Middle Latin thunnus. is derived from used for the Atlantic bluefin tuna, that name in turn is ultimately derived from thýnō to rush, dart along'..
A dated alternative term is "tunny".
In English, tuna has been referred to as Chicken of the Sea. This name persists today in Japan, where tuna as a food can be called 'sea chicken'.
Description
Tunas are sleek, elongated and streamlined fish, adapted for speed. They have two closely spaced but separated dorsal fins on its back; The first fin is "depressible" – it can be laid down, flush, in a groove that runs along its back, and is supported by spines. Seven to ten yellow finlets run from the dorsal fins to the tail, which is lunate – curved like a crescent moon – and tapered to pointy tips. A tuna's pelvic fins are located below the base of the pectoral fins. Both dorsal and pelvic fins retract when the fish is swimming fast.
The tuna's body is countershaded to camouflage itself in deeper water when seen from above, its dorsal side is generally a metallic dark blue while the ventral or under side is silvery, often with an iridescent shine. The caudal peduncle, to which the tail is attached, is quite thin, with three stabilizing horizontal keels on each side.
Physiology Thunnus are widely but sparsely distributed throughout the oceans of the world, generally in tropical and temperate waters at latitudes ranging between about 45° north and south of the equator. All tunas are able to maintain the temperature of certain parts of their body above the temperature of ambient seawater. For example, bluefin can maintain a core body temperature of , in water as cold as . Unlike other endothermic creatures such as mammals and birds, tuna do not maintain temperature within a relatively narrow range.
Tunas achieve endothermy by conserving the heat generated through normal metabolism. In all tunas, the heart operates at ambient temperature, as it receives cooled blood, and coronary circulation is directly from the gills. The rete mirabile, the intertwining of veins and arteries in the body's periphery, allows nearly all of the metabolic heat from venous blood to be "re-claimed" and transferred to the arterial blood via a counter-current exchange system, thus mitigating the effects of surface cooling. This allows the tuna to elevate the temperatures of the highly-aerobic tissues of the skeletal muscles, eyes and brain, which supports faster swimming speeds and reduced energy expenditure, and which enables them to survive in cooler waters over a wider range of ocean environments than those of other fish.
Also unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red myotomal muscles derive their color from myoglobin, an oxygen-binding molecule, which tuna express in quantities far higher than most other fish. The oxygen-rich blood further enables energy delivery to their muscles.
For powerful swimming animals like dolphins and tuna, cavitation may be detrimental, because it limits their maximum swimming speed. Even if they have the power to swim faster, dolphins may have to restrict their speed, because collapsing cavitation bubbles on their tail are too painful. Cavitation also slows tuna, but for a different reason. Unlike dolphins, these fish do not feel the bubbles, because they have bony fins without nerve endings. Nevertheless, they cannot swim faster because the cavitation bubbles create a vapor film around their fins that limits their speed. Lesions have been found on tuna that are consistent with cavitation damage.
Taxonomy The Thunnini tribe is a monophyletic clade comprising 15 species in five genera: family Scombridae tribe Thunnini: tunas genus Allothunnus: slender tunas genus Auxis: frigate tunas genus Euthynnus: little tunas genus Katsuwonus: skipjack tunas genus Thunnus: albacores and true tunas subgenus Thunnus (Thunnus): bluefin group subgenus Thunnus (Neothunnus): yellowfin group
The following cladogram is based on a 2026 genetic analysis of Scombridae using Bayesian inference, and separates the tunas both through evolutionary and ecological developments:
The following cladogram is based on a 2004 phylogenetic analysis, and illustrates the relationship between the tunas and other tribes of the family Scombridae. For example, it shows that the skipjack tunas are more closely related to the true tunas than are the slender tunas (the most primitive of the tunas), and that the next nearest relatives of the tunas are the bonitos of the tribe Sardini.
True species The "true" tunas are those that belong to the genus Thunnus. 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, B.B. Collette established that based on both molecular and morphological considerations, they are in fact distinct species.
The genus Thunnus is further divided into two subgenera: Thunnus (Thunnus) (the bluefin group), and Thunnus (Neothunnus) (the yellowfin group).
Other species The Thunnini tribe also includes seven additional species of tuna across four genera. They are:
{| class="wikitable" |- ! colspan="9" | Other tuna species |- ! style="width:10em" | Common name ! style="width:11em" | Scientific name ! Maximumlength ! Commonlength ! Maximumweight ! Maximumage ! Trophiclevel ! Source ! style="width:11em" |IUCN status |- | Slender tuna | Allothunnus fallai(Serventy, 1948) | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:center;" | 3.74 | style="text-align:center;" | | Least concern |- | Bullet tuna | Auxis rochei(Risso, 1810) | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | 5 years | style="text-align:center;" | 4.13 | style="text-align:center;" | | Least concern |- | Frigate tuna | Auxis thazard(Lacépède, 1800) | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | 5 years | style="text-align:center;" | 4.34 | style="text-align:center;" | | Least concern |- | Mackerel tuna,Kawakawa | Euthynnus affinis(Cantor, 1849) | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | 6 years | style="text-align:center;" | 4.50 | style="text-align:center;" | | Least concern |- | Little tunny | Euthynnus alletteratus(Rafinesque, 1810) | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | 10 years | style="text-align:center;" | 4.13 | style="text-align:center;" | | Least concern |- | Black skipjack tuna | Euthynnus lineatus(Kishinouye, 1920) | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:center;" | 3.83 | style="text-align:center;" | | Least concern |- | Skipjack tuna | Katsuwonus pelamis(Linnaeus, 1758) | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | | style="text-align:right;" | 6–12 yrs | style="text-align:center;" | 3.75 | style="text-align:center;" | | Least concern
Fishing
Commerce Tuna is an important commercial fish. The International Seafood Sustainability Foundation (ISSF) compiled a detailed scientific report on the state of global tuna stocks in 2009. According to the ISSF, the most important species for commercial and recreational tuna fisheries are yellowfin (Thunnus albacares), bigeye (T. obesus), bluefin (T. thynnus, T. orientalis, and T. macoyii), albacore (T. alalunga), and skipjack (Katsuwonus pelamis).
Based on catches from 2007, the report states:
The Australian government alleged in 2006 that Japan had illegally overfished southern bluefin by taking 12,000 to 20,000 tonnes per year instead of the agreed-upon 6,000 tonnes; the value of such overfishing would be as much as US$2 billion. Such overfishing has severely damaged bluefin stocks. According to the WWF, "Japan's huge appetite for tuna will take the most sought-after stocks to the brink of commercial extinction unless fisheries agree on more rigid quotas". Japan's Fisheries Research Agency counters that Australian and New Zealand tuna fishing companies under-report their total catches of southern bluefin tuna and ignore internationally mandated total allowable catch totals.
In recent years, opening day fish auctions at Tokyo's Tsukiji fish market and Toyosu Market have seen record-setting prices for bluefin tuna, reflecting market demand. In each of 2010, 2011, 2012, 2013 and 2019, new record prices have been set for a single fish – the current record is 333.6 million japanese yen (US$3.1 million) for a bluefin, or a unit price of JP¥ 1,200,000/kg (US$5,057/lb). The opening auction price for 2014 plummeted to less than 5% of the previous year's price, which had drawn complaints for climbing "way out of line". A summary of record-setting auctions are shown in the following table (highlighted values indicate new world records):
Record bluefin tuna auctions at Tokyo's Tsukiji fish market and Toyosu Market (Highlighted field indicates new record price for a single fish) Year Totalweight Total sale Unit price Source (JP ¥) (US $) (¥ / kg) ($ / lb) 2001 ¥20.2 million $173,600 ¥100,000 / kg $386 / lb 2010 ¥16.28 million $175,000 ¥70,172 / kg $343 / lb 2011 ¥32.49 million $396,000 ¥95,000 / kg $528 / lb 2012 ¥56.49 million $736,000 ¥210,000 / kg $1,247 / lb 2013 ¥155.4 million $1.76 million ¥703,167 / kg $3,603 / lb 2019 ¥333.6 million $3.1 million ¥1,200,000 / kg $5,057 / lb
In November 2011, a different record was set when a fisherman in Massachusetts caught an tuna. It was captured inadvertently using a dragnet. Due to the laws and restrictions on tuna fishing in the United States, federal authorities impounded the fish because it was not caught with a rod and reel. Because of the tuna's deteriorated condition as a result of the trawl net, the fish sold for just under $5,000.
Methods
Besides for eating, many tuna species are caught frequently as game, often for recreation or for contests in which money is awarded based on weight. Larger specimens are notorious for putting up a fight while hooked, and have been known to injure people who try to catch them, as well as damage their equipment.
Phoenician technique for trapping and catching Atlantic bluefin tuna called Almadraba, still used today in Portugal, Spain, Morocco and Italy which uses a maze of nets. In Sicily, the same method is called Tonnara. Fish farming (cage system) Tuna ranching Longline fishing Purse seines Pole and line Harpoon gun Big game fishing Fish aggregating device
Association with whaling