There is not one individual fish called “tuna” – there are more than a dozen species of tuna worldwide.

Many tuna companies, in fact, now track and label their canned tuna products to identify the specific type of tuna, the ocean where it was caught, and more.

Unique Tuna Characteristics

We’re highlighting the seven major commercial tuna species on this page, six in the genus Thunnus and one in the genus Katsuwonus. “Minor” or less economically important tunas, not covered here, include bullet tuna, blackfin tuna, and tonggol.

Tuna species share some distinctive characteristics.

  • Due to the physiology of their respiratory system, tunas are obligate ram ventilators — that is, they need to swim constantly to make water pass through their gills.
  • Because they swim constantly to oxygenate their blood, their muscular metabolism continuously generates heat, which gives them a unique feature among all bony fishes — the ability to regulate their body temperatures. Their thermoregulation capacity enables them to tolerate a wide range of water temperatures.

Tuna are highly migratory. They are widely distributed throughout all oceans in the world between equatorial and subpolar latitudes of both hemispheres. However, some tuna stocks are more abundant — or less heavily fished — than others.

Tuna Stock Status

Each year in our “Status of the Stocks” report, we evaluate 23 tuna stocks based on abundance, exploitation/management (fishing mortality), and environmental impact (bycatch).

Stock Status Tool

Use our interactive data-visualization tool to create and then download or share graphics on tuna stock status.

You can visualize data on 23 commercial tuna stocks (by species and ocean area) share of total catch and trends in stock health.