Bluefin tuna (Thunnus spp.) are a temperate water fish comprised of 3 species, North Atlantic bluefin (Thunnus thynnus thynnus), Pacific bluefin (Thunnus orientalis), and southern bluefin tuna (Thunnus maccoyii), with the widest geographical distribution of the tunas. The are four bluefin stocks assessed and managed by the RFMOs: Western Atlantic, Eastern Atlantic (including the Mediterranean), Pacific and Southern hemisphere.
Bluefin are the largest of the tunas. Atlantic bluefin can reach 3 m in length.
In the drawings to the right you can see the differences between Southern (top) and Atlantic (bottom) bluefin tunas.