Fish Identification Photos: Bluefin Tuna, Bluefin, Giant Tuna, Thunnus thynnus: The Bluefin Tuna is characterized by its massive “tuna-like” body, widest at the pelvic fins, deep metallic blue back, silvery white lower sides and belly, rather small eye, and a long pointed head. The Bluefin Tuna has alternating colorless lines and rows of dots along its lower sides.

Its first dorsal fin is either yellow or blue; its second dorsal (which is taller than the first dorsal fin) is either red or brown; its anal fin and seven to ten finlets are yellow, edged in black; the caudal keel is black. The Bluefin Tuna has short pectoral fins and the anal fin begins behind the second dorsal fin. The Bluefin Tuna might be confused with the Bigeye Tuna, Thunnus obesus (large eye and deep body), or the Yellowfin Tuna, Thunnus albacares (long anal and second dorsal fins that are yellow, and yellow finlets).

The Bluefin Tuna is a member of the Scombridae or Tuna, Bonito, and Mackerel Family. The Bluefin Tuna is the largest of the tunas that maintain a body temperature well above the temperature of the surrounding sea. It is a seasonal oceanic pelagic schooling species that undergoes an annual northerly summer migration. The Bluefin Tuna is found only along the Pacific coast of the Baja California peninsula, and appears to be absent from other Mexican waters. It is found at all levels within the water column and even up to depths of 3,000 feet. The Bluefin Tuna has been known to be travel at speeds of up to 45 m.p.h. and has crossed the Atlantic Ocean in 60 days. The largest known Bluefin Tuna was 15 feet in length and weighed 1,506 pounds (the IFGA all tackle record is 1,496 pounds); however, the Bluefin Tuna is more common around 6 feet in length. This species is initially caught via trolled feathers or jigs and then the bite is maintained on live anchovies or sardines with ample chum being used to keep the school in residence. They are viewed by locals to be a prized game fish that provides great bragging rights and excellent table fare.

Bluefin Tuna, Bluefin, Giant Tuna, Thunnus thynnus: Photo courtesy John W. Mykkanen.