Albacore are widely distributed throughout the world's marine ecosystems in tropical, sub-tropical, and temperate zones of the Pacific, Atlantic, and Indian Oceans. In the Pacific Ocean, it is generally believed that there exists two stocks of albacore, one in the North Pacific hemisphere and one in the South Pacific hemisphere. Available data indicate that the two stocks do not cross the equator and have separate spawning grounds and times.
The North Pacific albacore stock, which is the population that is primarily targeted by commercial and recreational fisheries associated with the U.S. Pacific coast, is centered around 35o N latitude in the Pacific Ocean. This stock's distribution extends from the central (west) coast of Mexico to the Gulf of Alaska in the eastern Pacific Ocean, and from the equator to the north (east) coast of Japan in the western Pacific Ocean. The actual boundaries of the stock's range depend largely on the season of the year and oceanic conditions (see below). Currently, fishery researchers are uncertain whether the population of albacore inhabiting the North Pacific Ocean is strictly a single stock or possibly, composed of two (or more) stocks. Results from some tagging experiments indicate that substocks of albacore may exist in the North Pacific Ocean, based on differences in migratory routes, growth and mortality rates, and size distributions of the commercial catches.
The two-stock hypothesis for the North Pacific albacore population defines a stock that migrates between the western and eastern Pacific Ocean north of approximately 40o N latitude, and a southern stock that enters the U.S. fisheries south of 40o N latitude and for the most part, does not travel back to western Pacific Ocean waters, but rather, stays in the central Pacific Ocean east of 180o. However, more information concerning albacore biology and genetics is needed before definitive conclusions can be drawn at this time regarding the stock structure of the North Pacific population of albacore. The South Pacific stock occurs from the equator to 40o S latitude in the central and western areas of the Pacific Ocean, and between 10o and 30o S latitude in waters between 150o E and 80o W longitude.