Thunnus

Last updated

True tunas
Temporal range: Tertiary–holocene
Yellowfin tuna nurp.jpg
Yellowfin tuna
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Scombriformes
Family: Scombridae
Tribe: Thunnini
Genus: Thunnus
South, 1845
Type species
Scomber thynnus
Linnaeus, 1758
Subgenus
Synonyms
  • Albacora Jordan, 1888
  • GermoJordan, 1888
  • KishinoellaJordan & Hubbs, 1925
  • NeothunnusKishinouye, 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. 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"). [3] [4] The first written use of the word was by Homer.[ citation needed ]

Contents

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 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 [5] . 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. [6]

Taxonomy

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]

Fossil specimen Thunnus spec 01.jpg
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 Tuna Relative Sizes.jpg
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
  Scombridae  
Gasterochismatinae  

  Butterfly kingfishes  (1 genus)

Scombrinae
  Scombrini  

  Mackerels  (2 genera)

  Scomberomorini  

  Spanish Mackerels  (3 genera)

  Sardini  

  Bonitos  (4 genera)

  Thunnini

  Allothunnus , slender tunas

  Auxis , frigate tunas

  Euthynnus , little tunas

  Katsuwonus , skipjack tunas

 Thunnus 
 subgenus Thunnus

 bluefin group

 subgenus Neothunnus

 yellowfin group

 (true tunas) 
(Tunas)
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

T. albacares

T. obesus

T. tonggol

T. atlanticus

T. maccoyii

T. thynnus

T. orientalis

T. alalunga

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]

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]

Thunnus, the true tunas
ImageCommon nameScientific nameMaximum
length
Common
length
Maximum
weight
Maximum
age
Trophic
level
Source IUCN status
Thunnus (Thunnus) – the bluefin group
Thunnus alalunga 2.jpg 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 yrs4.31 [13] [14] NT IUCN 3 1.svg Near threatened [14]
Thmac u0.gif 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 yrs3.93 [15] [16] CR IUCN 3 1.svg Critically endangered [16]
Thunnus obesus (bigeye tuna).jpg Bigeye tuna T. obesus
(Lowe, 1839)
2.5 m
(8.2 ft)
1.8 m
(5.9 ft)
210 kg
(460 lb)
5–16 yrs4.49 [17] [18] VU IUCN 3 1.svg Vulnerable [18]
Pacific bluefin tuna.jpg 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 yrs4.21 [19] [20] VU IUCN 3 1.svg Vulnerable [20]
Tuna 1.jpg 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 yrs4.43 [21] [22] EN IUCN 3 1.svg Endangered [22]
Thunnus (Neothunnus) – the yellowfin group
Thunnus atlanticus - pone.0010676.g186.png 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 [23] LC IUCN 3 1.svg Least concern [24]
Thunnus tonggol.jpg Longtail tuna,
northern bluefin tuna,
tongol tuna
T. tonggol
(Bleeker, 1851)
1.45 m
(4.8 ft)
0.7 m
(2.3 ft)
35.9 kg
(79 lb)
18 years4.50 [25] [26] DD IUCN 3 1.svg Data deficient [26]
Fish4499 - Flickr - NOAA Photo Library.jpg Yellowfin tuna T. albacares
(Bonnaterre, 1788)
2.4 m
(7.9 ft)
1.5 m
(4.9 ft)
200 kg
(440 lb)
5–9 yrs4.34 [27] [28] NT IUCN 3 1.svg Near threatened [28]
Maximum reported sizes of Thunnus species. Tuna sizes.svg
Maximum reported sizes of Thunnus species.

Overfishing

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 222-kilogram (489 lb) 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]

Related Research Articles

Tuna

A tuna is a saltwater fish that belongs to the tribe Thunnini, a subgrouping of the Scombridae (mackerel) family. The Thunnini comprise 15 species across five genera, the sizes of which vary greatly, ranging from the bullet tuna up to the Atlantic bluefin tuna. The Atlantic bluefin averages 2 m (6.6 ft), and is believed to live up to 50 years.

Mackerel

Mackerel is a common name applied to a number of different species of pelagic fish, mostly from the family Scombridae. They are found in both temperate and tropical seas, mostly living along the coast or offshore in the oceanic environment.

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 kingfish, which is the sole member of subfamily Gasterochismatinae.

Albacore

The albacore, known also as the longfin tuna, is a species of tuna of the order Perciformes. It is found in temperate and tropical waters across the globe in the epipelagic and mesopelagic zones. There are six distinct stocks known globally in the Atlantic, Pacific, and Indian oceans, as well as the Mediterranean Sea. The albacore has an elongate, fusiform body with a conical snout, large eyes, and remarkably long pectoral fins. Its body is a deep blue dorsally and shades of silvery white ventrally. Individuals can reach up to 1.4 m in length.

Atlantic bluefin tuna

The Atlantic bluefin tuna is a species of tuna in the family Scombridae. It is variously known as the northern bluefin tuna, giant bluefin tuna [for individuals exceeding 150 kg (330 lb)], and formerly as the tunny.

Yellowfin tuna

The yellowfin tuna is a species of tuna found in pelagic waters of tropical and subtropical oceans worldwide.

Billfish

The term billfish refers to a group of predatory fish characterised by prominent bills, or rostra, and by their large size; some are longer than 4 m (13 ft). Billfish include sailfish and marlin, which make up the family Istiophoridae, and swordfish, sole member of the family Xiphiidae. They are apex predators which feed on a wide variety of smaller fish, crustaceans, and cephalopods. These two families are sometimes classified as belonging to the order Istiophoriformes, a group with origins in the Late Cretaceous around 71 million years ago with the two families diverging from one and another in the Late Miocene around 15 million years ago. However, they are also classified as being closely related to the mackerels and tuna within the suborder Scombroidei of the order Perciformes. However, the 5th edition of the Fishes of the World does recognise the Istiophoriformes as a valid order, albeit including the Sphyraenidae, the barracudas.

Bigeye tuna Species of fish

The Bigeye tuna is a species of true tuna of the genus Thunnus, belonging to the wider mackerel family Scombridae.

<i>Fistularia tabacaria</i>

Fistularia tabacaria, the cornetfish, bluespotted cornetfish, tobacco trumpetfish or unarmed trumpetfish, is a species of cornetfish found along the Atlantic coasts of the Americas and in the central Atlantic off west Africa and the Macaronesian Islands. This species is of minor importance in commercial fisheries.

Southern bluefin tuna Species of fish

The southern bluefin tuna is a tuna of the family Scombridae found in open southern Hemisphere waters of all the world's oceans mainly between 30°S and 50°S, to nearly 60°S. At up to 2.5 metres (8.2 ft) and weighing up to 260 kilograms (570 lb), it is among the larger bony fishes.

Blackfin tuna

The blackfin tuna is the smallest tuna species in the genus Thunnus, generally growing to a maximum of 100 cm (39 in) in length and weighing 21 kg.

Pacific bluefin tuna

The Pacific bluefin tuna 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.

<i>Euthynnus affinis</i>

Euthynnus affinis, the kawakawa or mackerel tuna, is a species of ray-finned bony fish in the family Scombridae, or mackerel family. It belongs to the tribe Thunnini, better known as the tunas. This is an Indo-Pacific species which is found from the Red Sea to French Polynesia.

<i>Euthynnus</i>

Euthynnus is a genus of ray-finned bony fish in the family Scombridae, or mackerel family, and in the tribe Thunnini, more commonly known as the tunas.

<i>Thunnus tonggol</i>

Thunnus tonggol is a species of tuna of tropical Indo-West Pacific waters.

Several fish species are known as northern bluefin tuna including:

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 to as the yellowfin group, and comprises three species:

<i>Thunnus</i> (subgenus)

Thunnus (Thunnus) is a subgenus of ray-finned bony fishes in the Thunnini, or tuna, tribe. More specifically, Thunnus (Thunnus) is a subgenus of the genus Thunnus, also known as the "true tunas". Thunnus (Thunnus) is sometimes referred to as the bluefin group, and comprises five species:

References

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Further reading