Description: A very large fish, with a dark blue back and upper sides, and silvery white belly and lower sides. The second dorsal fin is red-brown in colour and is larger than the first, which is yellow to blue It has very short pectoral fins. It has a crescent-shaped tail.

Habitat: This species is normally pelagic but will occasionally come in closer to shore.

Distribution: This is a migratory species and can be seen off the west coast of Ireland and north coast of Northern Ireland.

Similar Species: Unlikely to be confused with any other species found in this region.

Key Identification Features:

• Dark blue back and sides, with silvery white belly.
• Crescent-shaped tail.
• Second dorsal fin is red-brown.

Distribution Map from NBN: Thunnus thynnus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Thunnus thynnus at iNaturalist World Species Observations database.

GBIF data for Thunnus thynnus

WoRMS: Thunnus thynnus at World Register of Marine Species. Accepted name: Thunnus thynnus (Linnaeus, 1758). AphiaID: 127029.

Classification: Biota; Animalia; Chordata; Vertebrata; Gnathostomata; Osteichthyes; Actinopterygii; Actinopteri; Teleostei; Scombriformes; Scombroidei; Scombridae; Scombrinae; Thunnus