Northern bluefin tuna (Thunnus thynnus)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



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.

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.

Global distribution



Thunnus thynnus is a pelagic species but seasonally comes close to shore.

Depth range


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

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).


  1. Collette, B.B. & Nauen, C.E., 1983. FAO species catalogue. Vol. 2. Scombrids of the World. An Annotated and Illustrated Catalogue of Tunas, Mackerels, Bonitos and Related Species Known to Date. Food and Agriculture Organization of the United Nations (FAO) Fisheries Synopsies, 125

  2. Frimodt, C., 1995. Multilingual illustrated guide to the world's commercial coldwater fish. Fishing News Books, Osney Mead, Oxford, England.

  3. Froese, R. & Pauly, D., 2007. Fishbase. A global information system on fishes. [On-line], 2008-02-18

  4. Howson, C.M. & Picton, B.E., 1997. The species directory of the marine fauna and flora of the British Isles and surrounding seas. Belfast: Ulster Museum. [Ulster Museum publication, no. 276.]

  5. Muus, B.J. & Nielsen, J.G. 1999. Sea Fish. Scandinavian Fishing Year Book. Hedehusene: Denmark

  6. Whitehead, P.J.P., Bauchot, M.-L., Hureau, J.-C., Nielson, J. & Tortonese, E. 1986. Fishes of the North-eastern Atlantic and the Mediterranean. Vol. I, II & III. Paris: United Nations Educational, Scientific and Cultural Organisation (UNESCO).


  1. NBN (National Biodiversity Network) Atlas. Available from:

  2. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. Accessed: 2024-07-21


This review can be cited as:

Barnes, M.K.S. 2008. Thunnus thynnus Northern bluefin tuna. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-07-2024]. Available from:

Last Updated: 25/03/2008