TUNA, PACIFIC BLUEFIN
The Pacific bluefin tuna is a predatory species of tuna found widely in the northern Pacific Ocean, but it is migratory and also recorded as a visitor to the south Pacific. In the past it was often included in T. thynnus, the 'combined' species then known as the northern bluefin tuna (when treated as separate, T. thynnus is called the Bluefin Tuna or Atlantic Bluefin Tuna). It may reach as much as 3 m (9.8 ft) in length and 450 kg (990 lb) in weight.
Like the closely related Bluefin Tuna (or Atlantic bluefin) and Southern Bluefin, the Pacific bluefin is a commercially valuable species and several thousand tonnes are caught each year, but unlike its relatives it does not appear to be threatened overall, despite beingoverfished. Monterey Bay Aquarium's Seafood Watch program have placed all Bluefin Tunas on the "Avoid" list, and they are also placed on Greenpeace's "Red List".
Pacific bluefin tuna are generally smaller than their Atlantic cousins, reaching a maximum length of 3m and a maximum weight of 540kg. 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.
The majority of Pacific bluefin are captured by east Asian fleets using purse seines. During recent years, most of the catches have been transported to holding pens, where the fish are held for fattening and later sale to markets. Lesser amounts of Bluefin are caught via trolling, gillnet, trap, pole-and-line and longline gear.
The Pacific bluefin tuna is primarily found in the North Pacific, ranging from the East Asian coast to the western coast of North America. It is mainly a pelagic species found in temperate oceans, but it also ranges into the tropics and more coastal regions. It typically occurs from the surface to 200 m (660 ft), but has been recorded as deep as 550 m (1,800 ft).
It spawns in the northwestern Philippine Sea (e.g., off Honshu, Okinawa and Taiwan) and in the Sea of Japan. A proportion of these migrate to the East Pacific and return to the spawning grounds after a few years. It has been recorded more locally as a visitor to the Southern Hemisphere, including off Australia, New Zealand, Gulf of Papua and French Polynesia.