Bigeye Tuna (Thunnus obesus)

Like other tuna, the bigeye is a member of the Scombridae family and a strong-fighting species that is equally revered for sport as for its flesh.

Other Names

bigeyed tuna, bigeye tunny; French: patudo, thon obèse; Hawaiian: ahi; Indonesian: taguw, tongkol; Italian: tonno obeso; Japanese: mebachi, mebuto; Portuguese: albacora bandolim, atum patudo, patudo; Spanish: albacora, atún ojo grande, patudo.

Identification

A stocky body and large eyes characterize this species. Generally, there are no special markings on the body, but some specimens may have vertical rows of whitish spots on the venter. The first dorsal fin is deep yellow.

The second dorsal fin and the anal fin are blackish brown or yellow and may be edged with black. The finlets are bright yellow with narrow black edges. The tail does not have a white trailing edge like that of the albacore.

The pectoral fins may reach to the second dorsal fin. The second dorsal fin and the anal fins never reach back as far as those of large yellowfin tuna. It has a total of 23 to 31 gill rakers on the first arch. The margin of the liver is striated.

The two dorsal fins are close-set, the first having 13 to 14 spines and the second 14 to 16 rays. The anal fin has 11 to 15 rays. On either side of the caudal peduncle is a strong lateral keel between two small keels that are located slightly farther back on the tail.

Size

Bigeyes are normally found from 16 to 67 inches in length but may attain 75 inches. The all-tackle world record is a 435-pound fish caught off Peru in 1957.

Spawning behavior

Bigeye tuna reach sexual maturity at about 40 to 50 inches in length and spawn at least twice a year. This occurs throughout the year in tropical waters, peaking during the summer months.

Tuna fishing guide

Food

The diet of bigeyes includes squid, crustaceans, mullet, sardines, small mackerel, and some deep-water species. They frequent the depths, particularly during the day, and, unlike other tuna, are rarely seen chasing baitfish at the surface.

Distribution/Habitat

Found in warm temperate waters of the Atlantic, Indian, and Pacific Oceans, this schooling, pelagic, seasonally migratory species is suspected of making rather extensive migrations. Schools of bigeye tuna generally run deep during the day, whereas schools of bluefin, yellowfin, and some other tuna are known to occasionally swim at the surface, especially in warm water.