FaunaHub

Tuna

FishMarineOpen Ocean

A yellowfin tuna (Thunnus albacares) swimming in open water.

Yellowfin tuna (Thunnus albacares).

Image: OAR/National Undersea Research Program (NURP), Public domain, via Wikimedia Commons (NOAA).

Overview

Tuna are large, fast-swimming fish of the mackerel family (Scombridae), including the bluefin, yellowfin, albacore, and skipjack. This page is a group-level overview; the bluefin and yellowfin tunas are used as references. Tuna are built for life in the open ocean — streamlined, powerful, and capable of long, high-speed migrations. Several species are among the most commercially valuable fish in the world.

Habitat & Range

Tuna are pelagic fish of the open ocean, ranging widely through warm and temperate seas around the world. Many undertake long migrations across entire ocean basins, following prey and water temperature. They are rarely tied to one place, which makes their management an international matter. Range and depth vary by species.

Diet

Tuna are powerful predators that feed on smaller fish, squid, and crustaceans, hunting actively in open water. Their high-speed lifestyle demands a lot of energy, supported by an efficient, warm-bodied physiology. Diet varies by species and size; this page describes general feeding ecology.

Behavior

Tuna are remarkable athletes. Unusually among fish, several tuna can keep parts of their bodies warmer than the surrounding water, which helps power sustained fast swimming. Many travel in schools and cover vast distances on migration. They must keep moving to pass water over their gills. Behaviour and schooling vary among the tuna species.

Human Interaction & Conservation

Tuna are hugely important as food and support major global fisheries, which has put intense pressure on some species. Certain populations — notably some bluefin stocks — have been seriously depleted by overfishing, while others are more stable, and management efforts aim to rebuild stocks. Because status differs sharply by species and population and changes over time, it should be verified against current IUCN Red List and government (such as NOAA Fisheries) sources rather than assumed.

Appearance & Recognition

Tuna have a sleek, torpedo-shaped body built for speed, with a crescent-shaped tail, a row of small finlets along the rear of the body, and fins that can fold into grooves to reduce drag. They are typically dark blue above and silvery below — countershading suited to open water. Sizes range from the modest skipjack to the massive Atlantic bluefin, one of the largest bony fishes.

Similar Animals

Tuna belong to the mackerel family and are open-ocean predators like some of the sharks covered on FaunaHub, though tuna are bony fish rather than cartilaginous. They share pelagic waters with other fast-swimming hunters and with marine mammals such as dolphins.

More photos of the tuna

Atlantic bluefin tuna swimming together underwater.

Atlantic bluefin tuna (Thunnus thynnus).

Image: The Great Mule of Eupatoria, CC BY-SA 4.0, via Wikimedia Commons.

Frequently Asked Questions — Tuna

Are tuna warm-blooded?
Not in the way mammals are, but several tuna species are unusual among fish in being able to keep parts of their body — such as swimming muscles — warmer than the surrounding water. This regional warming helps power their sustained, high-speed swimming.
Why must tuna keep swimming?
Tuna rely largely on forward motion to pass oxygen-rich water over their gills (ram ventilation), so they keep swimming to breathe. This continuous movement also suits their migratory, open-ocean way of life.
Are tuna overfished?
Some tuna populations, particularly certain bluefin stocks, have been heavily depleted by fishing, while others are more stable, and management efforts aim to rebuild stocks. Status varies by species and population and changes over time, so check current IUCN and government sources.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.