Tuesday, July 31, 2007

Tuna general fact sheet

Thunnus albacares | Yellowfin tuna

The yellowfin tuna can reach a maximum length of 3.2 m and a maximum weight of 190 kg. The yellowfin tuna can be identified at surface by the brilliant yellow colour of the second dorsal fin, which is more elongated than in other tuna species. They are migratory and pelagic and can be found in waters with depths of up to 800 m (although they pass the majority of their time in the upper 100 m of the water column). They may approach coastlines, but they are most often seen in open ocean and in the vicinity of seamounts. They are distributed throughout subtropical and tropical waters of the world, except in the Mediterranean. The time of spawning peaks during the summer months, with a single female releasing millions of eggs at a time (almost exclusively at night). This species is well known to gather with groups of dolphins during feeding frenzies. In the Azores, yellowfin tuna are normally seen between April and October. The local minimum catch limit is 3.2 kg. They feed on smaller pelagic fish, such as Atlantic chub mackerel, blue jack mackerel, boar fish and cephalopods (squid and octopus) in the Azores. Reproduction is oviparous with external fertilization (162,918 – 8,062,026 eggs per spawning) and they can live to be 8 years. Conservation status: Near Threatened. 

Thunnus thynnus | Bluefin tuna

The bluefin tuna reaches a length of 2 - 3 m (maximum 6.79 m) and weighs betweem 136 and 680 kg. The bluefin tuna is one of the most well adapted species of tuna in the world, and also the most appreciated by mankind. It's the largest species of tuna and can dive to about 914 m deep. It is estimated that bluefin tuna can reach speeds up to 50 km/h. This species is highly migratory and is homeothermic, meaning that it is capable of regulating its body temperatur relative to its enviroment. Bluefin tuna can be seen in more northern latitudes  than any other tuna species. During the reproductive period individuals group up in large schools, making them more vulnerable to overfishing. In the Azores, bluefin tuna occur year-round, but are more common from the end of March to the end of April, and occasionally from the end of September to the end of October. The individuals that occur in the Azores reproduce in the Mediterranean. Bluefin tuna feed on fish such as skipjack, Atlantic chub mackerel, herring, sea bass, flying fish, mullets, squid and eels. Reproduction is oviparous with external fertilization (spawning  up to 90 egg per gram of body weight (more then others in the genus Thunnus). They can live to be at least 35 years old but possibly up to 50 years (breeding age: Western Atlantic 8 - 12 years and Eastern Atlantic 3 - 5 years). Conservation: Endangered and declining.

Thunnus obesus | Bigeye tuna

The bigeye tuna can reach a maximum length of 2.39 m and weigh 30 – 130 (in the Azores) (maximum weight is 210 kg). The bigeye tuna has a metalic blue colouration on its dorsal and a white ventral. They can be distinguished from other tuna species by the presence of an irridescent blue longitudinal band and its eyes which are larger than in other tuna species. They occur in waters ranging from 13 - 29° C, with the ideal range 17 - 22° C, and can dive down to about 500 m deep. Bigeye tuna are distributed throughout the Atlantic, Pacific and Indian Oceans, but they do not occur in the Mediterranean. They prefer open ocean, but can also be in coastal waters, especially around oceanic banks and seamounts. Spawning can occur several months with a frequency of every day of second day. Bigeye tuna is highly valued  in the fishing industry and in the Azores it is the second most captured tuna species, after the skipjack tuna. In the Azores they may be found between April and October but are most abundant from mid April to mid June. Bigeye tuna feed on smaller pelagic fish, such as Atlantic chub mackerel, blue jack mackerel, boar fish and cephalopods (squid and octopus) in the Azores. Reproduction is oviparous with external fertilization (Average 2.9 – 6.3 million eggs/spawning). Longevity: Western pacific: 16 years, Indian Ocean: 8 years, Atlantic Ocean: 9 years, Eastern Pacific: 5 years. Conservation status: Vulnerable (population decreasing). 

Thunnus alalunga | Albacore

The albacore can reach a length of 1.2 – 1.4 m and weigh 40 – 60 kg. The albacore tuna, or simply albacore is characterised by having very long pectoral fins, leading to its name in portuguese "atum voador" which means "flying tuna". This species is known for its tireless fighting during the fishing season. They are found mostly in the upper 100 m of the water column, but can dive down to 800 m. Albacore inhabit tropical to subtropical regions with surface waters typically ranging from 15.6˚ C to 19.4˚ C, although they can tolerate temperatures as low as 9.5˚ C for short periods. This species is highly migratory, travelling in large groups/schools, typically more then 20 miles off the coastline. Albacore occur in the Azores during April and again from September to December, in coastal zones, open water and around seamounts. At the beginning of July they travel southwest to Spain, between July and August they travel to the Bay of Biscay and in the winter they migrate to the Caribbean. Albacore feed in the Azores on small pelagic fish, especially chub mackerel, blue jack mackerel, boar fish and cephalopods (squid and octopus). Albacore can live between 9 – 13 years. Conservation status: Near threatened.

In other languages (yellowfin | bluefin | bigeye | alabcore):
Portuguese: Atum-de-galha-à-ré | Atum-rabilho | Patudo |  Voador
Spanish: Atún de aleta amarilla | Atún azul | Atún patudo | Atún blanco
French:  Thon jaune | Thon rouge du Nord | Thon obèse germon/thon blanc
Italian: Tonno pinna gialla | Tonno rosso | Tonno obeso | Alalunga/alalonga
German: Gelbflossen-Thun Rote Thun | Großaugen-Thun | Weiße Thun/Langflossenthun
Dutch:  Geelvintonijn | Blauwvintonijn | Grootoogtonijn | Witte tonijn
Swedish: Gulfenad tonfisk | Röd tonfisk eller blåfenad tonfisk Storögd tonfisk | Långfenad tonfisk
Norwegian:  Gulfinnetun Makrellstørje Storøyd tunfisk | Albakor
Danish:  - | - | - | -
Finnish:  Keltaevätonnikala Tonnikala Isosilmätonnikala | Valkotonnikala
Polish: Tuńczyk żółtopłetwy Tuńczyk pospolity |  -  | Tuńczyk biały
Russian:  Желтопёрый тунец Обыкновенный тунец Большеглазый тунец | Длиннопёрый тунец

Yellowfin tuna

Yellowfin tuna

Yellowfin tuna

Bluefin tuna

Bluefin tuna

Bigeye tuna

Tuna sp. and a dolphin

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