Creature Feature: Bigeye Tuna

bigeye tunaBigeye tuna range worldwide in warmer seas; they are only occasional visitors to Southern California. When they appear, bigeye tuna may be found on the California tuna grounds from June until November. They prefer water temperatures in excess of 70° F, but significant catches have occurred in water as cool as 65° F.

Distinguishing Characteristics

  • Dark, metallic brownish-blue on the back becoming gray or whitish below
  • Often has a bluish stripe on the side
  • Body tapered at both ends (cigar-shaped)
  • Head pointed, eyes relatively large
  • Pectoral fins extend past insertion of anal fin
  • Bigeye tuna can be distinguished from albacore or yellowfin tuna by comparing livers upon cleaning; bigeye tuna liver is lightly striated (covered with blood vessels) along the edges

Life History & Other Notes
The diet of bigeye tuna includes fishes, squid, and crustaceans. Like most other tunas, they feed on whatever is most abundant wherever they happen to be.

Bigeye tuna do not spawn off California. A bigeye tuna weighing 159 lb. will produce over three million eggs per year. The young are fast growing and weigh about 45 lb. at maturity.

Bigeye tuna travel at great depths during the day, only rarely coming to the surface to feed, which makes them a challenging target for anglers. Try trolling marlin lures in an area where bigeye tuna are known to occur. Most bigeye tuna taken off California weigh under 200 lb.

Bigeye Tuna Quick Facts

Scientific Name: Thunnus obesus

Other Common Names: gorilla tuna, patudo, BET

Range & Habitat: Statewide, but usually off central and Southern California

Length & Weight: To 7 ft. and 435 lb.

Life Span: To 9 years

Diet & Suggested Bait/Lures: Feeds on fishes, squid, and crustaceans. Try trolling marlin lures.

Excerpt from the California Finfish and Shellfish Identification Book.

Single copies of the book are available to California residents free of charge by emailing a request to