Tuna Identification Guide
How to identify tuna and separate the main species by finlets, fins, and markings.
Read the full Tuna encyclopedia entry →
Tuna are powerful, fast-swimming members of the mackerel family built for the open ocean. Several species are lumped under the name.
Key identification features
- Torpedo-shaped, streamlined body built for speed.
- A row of small finlets running from the second dorsal and anal fins to the tail — a family hallmark.
- A stiff, crescent (lunate) tail.
- Metallic blue-black backs with silvery sides.
Telling species apart
- Bluefin: very stout, short pectoral fins, deep blue back — the largest tunas.
- Yellowfin: long, sickle-shaped yellow second dorsal and anal fins; yellow finlets.
- Albacore: extremely long pectoral fins reaching past the anal fin.
- Skipjack: dark horizontal stripes along the lower belly.
Where you'll see one
Tuna roam warm and temperate open seas worldwide. The torpedo body, finlets before the tail, and crescent tail identify a tuna; fin length and markings pin down the species.
Frequently asked questions
What are the little fins near a tuna's tail?
They are finlets, a series of small non-retractable fins characteristic of tuna and their relatives in the mackerel family.
How do I tell a Yellowfin from a Bluefin Tuna?
Yellowfin have long, sickle-shaped yellow dorsal and anal fins, while Bluefin are stouter with short pectoral fins and a deep blue back.