Pacific Bluefin Tuna

Physical Description

Pacific bluefin tuna adults can reach a maximum length of 10 feet and 1200 pounds, and are generally smaller than their cousins in the Atlantic. 

Bluefin tuna are built like torpedoes. Not only do they have a hydrodynamic shape, their pectoral (side) fins can be retracted and, unlike other fish, their eyes are set flush to their body. This means their bodies create little drag as they swim through water.  A warm body temperature also helps these fish swim fast, as does a stiff body that channels muscle energy directly to a highly efficient, crescent-shaped tail.

Pacific bluefin tuna’s diet consists of fish, krill and squid.
© Brandon D. Cole / WWF-US

Habitat and Distribution

In the eastern Pacific, bluefin tuna have been spotted from Baja California as far north as the Gulf of Alaska, though they rarely venture further north than Oregon.   In the western Pacific, bluefin tuna can be found as far north as Russia’s Sakhalin Island and as far south as New Zealand.

Diet

Pacific bluefin tuna’s diet consists of fish, krill and squid.

Reproduction

Pacific bluefin tuna spawn between Japan and the Philippines, in April and August.  They reach reproductive maturity at around 5 years and 60kg.

Threats

Threats to the Pacific bluefin tuna include overfishing, a growing bluefin ranching industry in Mexico, and the depletion of Atlantic and Southern bluefin.

Policy

Bluefin tuna are largely unregulated in the Pacific beyond a gentlemen’s agreement among fishing nations not to increase fishing effort beyond recent levels.