''Thunnus'' is a genus of ocean-dwelling,

ray-finned Actinopterygii (; ), members of which are known as ray-finned fishes, is a class of bony fish. They comprise over 50% of living vertebrate species. The ray-finned fishes are so called because their fins are webs of skin supported by bony or hor ...

bony fish Osteichthyes (), popularly referred to as the bony fish, is a diverse superclass of fish that have skeletons primarily composed of bone tissue. They can be contrasted with the Chondrichthyes, which have skeletons primarily composed of cartilag ...

from the mackerel family,

Scombridae The mackerel, tuna, and bonito family, Scombridae, includes many of the most important and familiar food fishes. The family consists of 51 species in 15 genera and two subfamilies. All species are in the subfamily Scombrinae, except the butterfly ...

. More specifically, ''Thunnus'' is one of five

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

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 In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between t ...

. The word is the

Middle Latin Medieval Latin was the form of Literary Latin used in Roman Catholic Church, Roman Catholic Western Europe during the Middle Ages. In this region it served as the primary written language, though local languages were also written to varying deg ...

form of the Greek (, "tuna, ") – which is in turn derived from (, "to rush; to dart"). 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 long and weigh up to . All tunas are extremely strong swimmers, and the yellowfin tuna is known to reach speeds of up to 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. Bluefin tunas, for example, are found in

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

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 Overfishing is the removal of a species of fish (i.e. fishing) from a body of water at a rate greater than that the species can replenish its population naturally (i.e. the overexploitation of the fishery's existing fish stock), resulting in th ...

, the range of this genus has declined significantly, having been effectively extirpated from the Black Sea, for example.

Taxonomy

Based on morphology and short-length

mitochondrial DNA Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial D ...

sequence data, the genus ''Thunnus'' is currently classified into two

: ''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. 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''. Earlier nuclear ribosomal DNA phylogenetic reconstructions also showed similar results. Thunnus spec 01

This genus has eight species in two

: * Subgenus ''Thunnus (

Thunnus ''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 ...

)'': ** Albacore, ''T. alalunga'' ( Bonnaterre, 1788) ** Southern bluefin tuna, ''T. maccoyii'' ( Castelnau, 1872) ** Bigeye tuna, ''T. obesus'' (Lowe, 1839) **

Pacific bluefin tuna The Pacific bluefin tuna (''Thunnus orientalis'') is a predatory species of tuna found widely in the northern Pacific Ocean, but it is migratory and also recorded as a visitor to the south Pacific. In the past it was often included in '' T. thyn ...

, ''T. orientalis'' ( Temminck & Schlegel, 1844) ** Atlantic bluefin tuna, ''T. thynnus'' ( Linnaeus,

1758 Events January–March * January 1 – Swedish biologist Carl Linnaeus (Carl von Linné) publishes in Stockholm the first volume (''Animalia'') of the 10th edition of Systema Naturae, 10th edition of ''Systema Naturae'', the sta ...

) * Subgenus ''Thunnus (

Neothunnus ''Thunnus (Neothunnus)'' is a subgenus of ray-finned bony fishes in the Thunnini, or tuna, tribe. More specifically, ''Neothunnus'' is a subgenus of the genus ''Thunnus'', also known as the "true tunas". ''Neothunnus'' is sometimes referred t ...

)'': ** Yellowfin tuna, ''T. albacares'' ( Bonnaterre, 1788) **

Blackfin tuna The blackfin tuna (''Thunnus atlanticus'') is a species of tuna in the family Scombridae. It is occasionally referred to as the bermuda tuna, blackfinned albacore, or deep bodied tunny. They are the smallest tuna species in the genus ''Thunnus'', ...

, ''T. atlanticus'' ( Lesson, 1831) ** Longtail tuna, ''T. tonggol'' (

Bleeker Bleeker is a Dutch occupational surname. Bleeker is an old spelling of ''(linnen)bleker'' ("linen bleacher").

Species

Until recently, seven ''Thunnus'' species were thought to exist, and Atlantic bluefin tuna and Pacific bluefin tuna were

subspecies In biological classification, subspecies is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (morphology), but that can successfully interbreed. Not all species ...

of a single species. In 1999, Collette established that based on both molecular and morphological considerations, they are, in fact, distinct species. Tuna sizes

Overfishing

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

References

External links

*
Nutritional benefits of tuna

The International Commission for the Conservation of Atlantic Tunas
{{Authority control Marine fish genera Extant Cenozoic first appearances

Taxonomy

Species

Overfishing

References

Further reading

External links