Tuna

Tuna
Bigeye tuna , Thunnus obesus
Systematics
Acanthomorphata Spinefish (Acanthopterygii) Perch relatives (Percomorphaceae) Order : Scombriformes Family : Mackerel and tuna (Scombridae) Genre : Tuna
Scientific name
Thunnus
South , 1845

Tuna ( Thunnus , from ancient Greek θύννος thynnos ' tuna ', derived from θύνω thyno , I hurry, I rush, I shoot along' because of the fast movement of the fish) (also tuna ) denote a genus of large predatory fish, which in all tropical, subtropical and temperate seas. They are among the most important edible fish and are of great importance for the fishing industry. Some of the eight species are now threatened by overfishing .

features

Tuna have an elongated, spindle-shaped body that is only slightly flattened on the sides, the focus of which is in the front part of the trunk. They reach body lengths of about 1 m to 4.5 m and can weigh between 20 kg and 700 kg. The body is covered with very small scales, the front body is surrounded by a corset of larger scales. The head is pointed. The mouth is terminal, deeply split and cannot be pushed forward. The small, conical teeth sit in a row in each jaw. On the first gill arch there are 19 to 43  gill rakes . The two relatively small dorsal fins are close together. The longer first is supported by 11 to 14 fin spines, the shorter second by 12 to 16 soft rays. In the first dorsal fin, the first fin spines are much higher than the last, so that the upper edge of the fin is concave, the second crescent-shaped and as high as the first or higher. Between the second dorsal fin and the caudal fin are 7 to 10 rafts. The anal fin is almost symmetrically opposite the second dorsal fin and has the same shape as this. It is supported by 11 to 16 fin rays. The anal fin is followed by 7 to 10 fleas. The species vary in the length of the pectoral fins. With 30 to 36 fin rays in the pectoral fins, they have more than all other genera of the Scombridae. A two-part Interpelvic outgrowth is found in the pelvic fins. The tail stalk is slender and has a strong, bony side keel between two smaller keels for stabilization. The tail fin of the tuna is sickle-shaped. The first dorsal fin, the pelvic fins and the anal fin can be placed in channel-shaped depressions when swimming quickly. Most species have a swim bladder , the volume of which can be greatly changed and is still very small in juvenile fish. The number of vertebrae is 39. Tuna are generally bluish in color, gray or silvery on the belly and show no dark spots on the sides of the body. The back is dark blue and without the striped pattern typical of many other Scombrids. The rafts behind the dorsal and anal fin are mostly yellow and in some species have black edges.

Tuna have a very high metabolic rate and, along with swordfish ( Xiphias gladius ) and god salmon (examined on Lampris guttatus ), are among the few known bony fish with an at least partially endothermic metabolism. A blood vessel system ( rete mirabile ) connected to the trunk muscles and working in the countercurrent principle dissipates the heat generated by the activity of the large muscle mass inside the body, so that the internal body temperature and the temperature of the brain and eyes ( retina and optic nerve ) 9 to 12 ° C above the temperature of the water. The intensive gas exchange via the gills, which is indispensable for their high metabolism, is achieved through continuous swimming and the fast swimming style of the tuna. The ability to increase the body temperature, increases with the size and the albacore tuna , the yellowfin tuna and the bigeye tuna very good and the bluefin tuna most developed.

Jumping yellowfin tuna

Surname

The name tuna is derived from the ancient Greek θύννο? (thynnos) = tuna, which in turn goes back to θύνω (thyno) = I hurry, storm. The name refers to the rapid movement of the fish.

Way of life

Hike, diet

Tuna are found in all tropical, subtropical and temperate seas, mostly at depths of up to 500 meters, but are absent in the polar seas . They live in schools or swarms, undertake long migrations across the open ocean, including diurnal vertical migrations, and can maintain high speeds over long periods of time. They primarily hike after their prey, which in turn strive for regions with a high density of plankton . The groups always consist of individuals of the same size; small tunas form larger schools than groups of large animals. Very large specimens can also live as solitary animals.

Tuna feed on smaller fish, including the mackerel that is related to them . Other prey animals are herrings , squids and pelagic crustaceans . For some species of tuna, deep diving has been demonstrated ( bigeye tuna up to 1839 meters [2.5 ° C] and bluefin tuna up to 1000 meters [3 ° C]), where they prey (fish, cephalopods and crustaceans) that dive to greater depths during the day ) to hunt. Because of their size, they have few predators, especially swordfish species , sharks and toothed whales .

Movement, reproduction

Tuna hardly move their torso when swimming, but only use the fast-swinging, very stiff, crescent-shaped tail fin to propel them, to which the torso muscles transfer their power by means of tendon plates. This thunniform way of swimming, probably developed with partial endothermia, is almost unique among bony fish and may only be found in swordfish.

Tropical tuna spawn all year round, while species living in temperate regions with more forage migrate to warmer regions during the spawning season. Eggs and larvae are pelagic . Large females can shed millions of eggs (up to 10 million in bluefin tuna).

Systematics

External system

Tuna belong to the family of mackerel and tuna (Scombridae) and form the monophyletic tribe Thunnini with four other, species-poor genera . The following cladogram shows the systematic position of the tuna within the Scombridae:

The real bonito ( Katsuwonus pelamis ) is the closest relative of the tuna.

Scombridae	Scombrinae     Thunnini     Tuna    Subgenus Thunnus      Subgenus Neothunnus      Katsuwonus      Euthynnus      Auxis      Allothunnus      Sardini (genus Sarda and relatives)      Scomberomorini ( Wahoo , genera Grammatorcynus & Scomberomorus )      Scombrini ( mackerel and relatives)   Gasterochismatinae    Large scale mackerel ( Gasterochisma melampus )

Internal system

There are eight species in two subgenus, Neothunnus , which consists of four mainly tropical species, and Thunnus , the four species of which also occur in temperate latitudes because of better heat retention.

Subgenus Thunnus South , 1845 - 4 species
German name	Scientific name	distribution	Hazard level Red List of IUCN	Maximum length and weight	image
White tuna or long fin tuna	Thunnus alalunga ( Bonnaterre , 1788)	In all tropical, subtropical and temperate seas, including the Mediterranean.	( Near Threatened - potentially at risk)	1.40 meters, 60.3 kg
Southern bluefin tuna	Thunnus maccoyii ( Castelnau , 1872)	In all seas of the southern hemisphere in temperate and cool areas.	( Critically Endangered )	2.45 meters, 260 kg
North Pacific Bluefin Tuna	Thunnus orientalis ( Temminck & Schlegel , 1844)	Mainly in the northern Pacific, but also south to New Zealand.	( Vulnerable - endangered)	3.00 meters, 450 kg
Bluefin tuna , even Big tuna, North Atlantic tuna or bluefin tuna	Thunnus thynnus ( Linnaeus , 1758)	In the tropical, subtropical and temperate Atlantic and Mediterranean.	( Endangered - endangered)	4.50 meters, 684 kg
Subgenus Neothunnus Kishinouye , 1923 - 4 species
German name	Scientific name	distribution	Risk level IUCN Red List	Maximum length and weight	image
Yellowfin Tuna	Thunnus albacares ( Bonnaterre , 1788)	In all tropical, subtropical and temperate seas, but not in the Mediterranean.	( Near Threatened - potentially at risk)	2.40 meters, 200 kg
Black fin tuna	Thunnus atlanticus ( Lesson , 1831)	In the tropical and subtropical western Atlantic.	( Least Concern - not at risk)	1.08 meters, 20.6 kg
Bigeye Tuna	Thunnus obesus ( Lowe , 1839)	In all tropical, subtropical and temperate seas, but not in the Mediterranean.	( Vulnerable - endangered)	2.50 meters, 210 kg
Long-tailed tuna	Thunnus tonggol ( Bleeker , 1851)	Tropical Indo-Pacific and Red Sea .	( Data Deficient - insufficient data)	1.45 meters, 35.9 kg

Fossil record

Thunnus spec. from the clay pit Unterfeld ( Oligocene ) near Frauenweiler in the State Museum for Natural History Karlsruhe

The tuna probably separated from the other genera of the Thunnini in the Paleocene . The first tuna lived in the Tethys . The earliest fossils of tuna date from the Eocene . There are finds from North America, Africa and Europe, z. B. from the Italian Monte Bolca ( Thunnus lanceolatus ).

fishing

Worldwide catch of tuna in tons according to the FAO

Because of their red, fatty meat, tuna are among the most important food fish and are of great importance to the fishing industry. According to the FAO, the catch has increased from around 400,000 tons in 1955 to over 2 million tons annually since 1997. The largest catcher nations include Japan , where raw tuna meat is used for sushi and sashimi , the USA and South Korea . Tuna are caught with longlines , purse seine and drift nets . The latter is illegal in EU waters and many other areas because of the significant amount of unwanted bycatch of dolphins and sharks. In the Mediterranean, tuna are caught with very large anchored swimming traps called tonnaras. As early as the 18th century, salted tuna ( tonina ) prepared in Italy was offered by Tyrolean traders ("lemon men") along with other Mediterranean fish specialties on markets also north of the Alps. Tuna meat is marketed as fresh fish or frozen. The meat preserved in tuna cans comes mainly from bonitos .

Historic forms of tuna fishing are the Almadraba and Mattanza .

In some countries, e.g. B. Malta, tuna previously caught as juveniles are fattened in fish cages in the sea.

The management of global tuna stocks is in the hands of international and regional fisheries commissions: in the Atlantic and the Mediterranean, the International Commission for the Conservation of Atlantic Tuna (ICCAT) and the Inter-American Tropical Tuna Commission (IATTC ) for stocks in the Eastern Pacific. Further certification is provided by the Marine Stewardship Council (MSC).

Around ³ ⁄ _{4 of} the exports of tuna caught in the Mediterranean are currently going to Japan (as of 2020).

Pollution

Like other large predatory fish, tuna contains considerable amounts of mercury in the form of methylmercury, which is particularly harmful to health .

In May 2004 the EU Commission officially informed the member states that women who are or could become pregnant, as well as women who are breastfeeding and small children, should not consume more than two servings of 100 g tuna per week. The Federal Institute for Risk Assessment shares this assessment.

In the EU, a limit of 1 mg / kg mercury applies to large predatory fish. For other fish, the limit is reduced to 0.5 mg / kg. This value is often exceeded during border and market controls and the findings are communicated to the authorities across the EU as RASFF reports .

To ensure that tuna looks fresh and can be sold for as long as possible, carbon monoxide and nitrite are often used illegally .

swell

literature

• Bruce B. Collette, Cornelia E. Nauen: Scombrids of the world. An annotated and illustrated catalog of tunas, mackerels, bonitos and related species known to date (= FAO Species Catalog. Vol. 2 = FAO Fisheries Synopsis. No. 125, Vol. 2). United Nations Development Program et al., Rome 1983, ISBN 92-5-101381-0 .
• Kurt Fiedler: Fish (= textbook of special zoology. Vol. 2: Vertebrates. Part. 2). Gustav Fischer, Jena 1991, ISBN 3-334-00338-8 .
• Jeffrey B. Graham, Kathryn A. Dickson: Tuna comparative physiology. In: The Journal of Experimental Biology . 207, 2004, pp. 4015-4024, doi: 10.1242 / jeb.01267 .
• Bent J. Muus, Jørgen G. Nielsen: The marine fish of Europe in the North Sea, Baltic Sea and Atlantic. Kosmos, Stuttgart 1999, ISBN 3-440-07804-3 .

Individual evidence

1. ^ BB Collette, CE Nauen: Scombrids of the world. 1983, pp. 21 and 80.
2. ^ Fiedler: Fish. 1991, p. 389.
3. ↑ ^{a b} B. B. Collette, CE Nauen: Scombrids of the world. 1983, p. 80.
4. ^ W. Pape, Greek-German Concise Dictionary . Vol. 1, p. 1225, Vieweg, Braunschweig 1908.
5. ^ ^{A b} J. B. Graham, KA Dickson: Tuna comparative physiology. In: The Journal of Experimental Biology. 207, 2004, pp. 4015-4024, here p. 4018.
6. ↑ Thunnus alalunga on Fishbase.org (English)
7. ↑ Thunnus alalunga in the endangered Red List species the IUCN 2011. Posted by: Collette et al, 2011. Retrieved on November 29, 2012..
8. ↑ Thunnus maccoyii on Fishbase.org (English)
9. ↑ Thunnus maccoyii in the endangered Red List species the IUCN 2011. Posted by: Collette et al, 2011. Retrieved on November 29, 2012..
10. ↑ Thunnus orientalis on Fishbase.org (English)
11. ↑ Thunnus orientalis in the endangered Red List species the IUCN 2014 Posted by: Collette et al, 2014. Accessed November 22, 2015..
12. ↑ Thunnus thynnus on Fishbase.org (English)
13. ↑ Thunnus thynnus in the endangered Red List species the IUCN 2011. Posted by: Collette et al, 2011. Retrieved on November 29, 2012..
14. ↑ Thunnus albacares on Fishbase.org (English)
15. ↑ Thunnus albacares in the endangered Red List species the IUCN 2011. Posted by: Collette et al, 2011. Retrieved on November 29, 2012..
16. ↑ Thunnus atlanticus on Fishbase.org (English)
17. ↑ Thunnus atlanticus in the endangered Red List species the IUCN 2011. Posted by: Collette et al, 2011. Retrieved on November 29, 2012..
18. ↑ Thunnus obesus on Fishbase.org (English)
19. ↑ Thunnus obesus in the endangered Red List species the IUCN 2011. Posted by: Collette et al, 2011. Retrieved on November 29, 2012..
20. ↑ Thunnus tonggol on Fishbase.org (English)
21. ↑ Thunnus tonggol in the endangered Red List species the IUCN 2011. Posted by: Collette et al, 2011. Retrieved on November 29, 2012..
22. ^ JB Graham, KA Dickson: Tuna comparative physiology. In: The Journal of Experimental Biology. 207, 2004, pp. 4015-4024, here pp. 4015-4016.
23. ^ Karl Albert Frickhinger: Fossil Atlas of Fishes. Mergus - Verlag für Natur- und Heimtierkunde Baensch, Melle 1991, ISBN 3-88244-018-X .
24. ↑ Hans-Peter Baum : On the southern goods range on the Würzburg market in 1725. In: Ulrich Wagner (Ed.): History of the city of Würzburg. 4 volumes; Volume 2: From the Peasants' War in 1525 to the transition to the Kingdom of Bavaria in 1814. Theiss, Stuttgart 2004, ISBN 3-8062-1477-8 , pp. 445–447, here: pp. 445 f.
25. ↑ Tuna - Save the King of the Seas! . Greenpeace. September 29, 2012. Retrieved October 4, 2017.
26. ↑ Questions and Answers about: Tuna. Marine Stewardship Council, accessed April 5, 2019 . 
27. ↑ EU Commission: Methylmercury in fish and fishery products
28. ↑ Federal Institute for Risk Assessment (BfR): Mercury and methyl mercury in fish and fish products - assessment by EFSA
29. ↑ Health Department of the Canton of Basel-Stadt: Illegal coloring of tuna meat. In: gd.bs.ch . May 28, 2019. Retrieved May 28, 2019 . 

Web links

Commons : Tuna ( Thunnus )  - Collection of images, videos and audio files

Wiktionary: Tuna  - explanations of meanings, word origins, synonyms, translations

• Thunnus on Fishbase.org (English)