Biodiversity & Conservation

Northern bluefin tuna - Thunnus thynnus

Northern bluefin tuna

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Distribution map

Thunnus thynnus recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

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  • UK_BAP
  • OSPAR
Taxonomy icon Taxonomy Taxon English term
Phylum Chordata Sea squirts, fish, reptiles, birds and mammals
Class Actinopterygii Ray-finned fish, e.g. sturgeon, eels, fin fish, gobies, blennies, and seahorses
Authority (Linnaeus, 1758)
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Generally an oceanic species, it may be found off the Scottish coast to eastern, southern and south-western coasts of the British Isles and western Ireland.
Habitat information icon Habitat information Thunnus thynnus is a pelagic species but seasonally comes close to shore.
Text page icon Description One of the largest bony fish in the world, the northern bluefin tuna has a very streamlined and powerful body. It can reach up to 300 cm in length and weigh over 450 kg. The body is deepest near the middle of the first dorsal fin and tapers to a pointed snout. The upper body is dark blue in colour while the lower half is silvery white. Thunnus thynnus has a large and crescent-shaped tail and its dorsal and anal fins are yellowish in colour. Bluefin tuna are known for the finlets that run down the dorsal and ventral sides towards the anal fin.
Identifying features
  • Large streamline fish, up to 300 cm in length.
  • The body is deepest near the middle of the first dorsal fin.
  • The second dorsal fin is higher than the first.
  • The pectoral fins are very short, less than 80% of head length.
  • The tail is crescent shaped.
  • Lower sides and ventral area are silvery white with colorless transverse lines alternated with rows of colorless dots.
  • Dark blue dorsal colouring.
Additional information icon Additional information Northern bluefin tuna school by size, sometimes together with other species. It preys on small schooling fishes or on squids and red crabs. They are commercially cultured although not in the UK or Ireland (Frimodt, 1995), and have become rare elsewhere because of substantial overfishing (Muus & Nielsen, 1999).

This review can be cited as follows:

Morvan Barnes 2008. Thunnus thynnus. Northern bluefin tuna. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 04/02/2012]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=4473>