Tuna Fishing

Tuna fishing as a major industry did not exist before the 20th century, although there were some catches of “giant” mackerel off areas such as the British Isles that may have been bluefin tuna. Industrial tuna fishing began in the United States in 1903, when tuna was seen as a possible replacement for dwindling sardine catches, but the industry really took off during World War II, when canned tuna became an important source of protein. Tuna have been caught with driftnets, purse seine nets, long lines, and traps. The United States and Japan are currently the two largest consumers of tuna, accounting for 31 percent and 36 percent of the world catch, respectively. In 2000, an estimated 3.6 million tons of tuna were caught, 66 percent from the Pacific Ocean, 20.7 percent from the Indian Ocean, 12.5 percent from the Atlantic, and 0.8 percent from the Mediterranean and Black Seas.

Tuna belong to the teleost family Scombridae. Major target species include bluefin, albacore, skipjack, bigeye, and yellowfin. The largest of these are bluefin tuna (Thunnus thynnus), which typically grow to 20 feet (6 meters) and 1,102 pounds (500 kilograms), but some specimens have weighed over 1,499 pounds (680 kilograms). Bluefin in the south Pacific are estimated to be at 15–20 percent of their historic stock size due to overfishing. Moreover, recent research suggests that bluefin quotas in the Atlantic have been set too high, and due to the wide-ranging migration patterns of these fish, individuals from depleted populations may move to areas of high fishing pressure. Bluefin tuna are primarily traded with Japan and sold for consumption as sushi and sashimi.

Albacore tuna (Thunnus alalunga) are subtropical and have distinctive long pectoral fins but are much smaller than bluefin, at two feet (0.7 meter) in length and 22–44 pounds (10–20 kilograms), although they can grow up to five feet (1.4 meters) long and weigh 132 pounds (60 kilograms). This species was depleted by driftnet fisheries but may now be recovering with the introduction of largescale driftnet bans. This species is frequently targeted for the canned tuna industry.

The main target species for canned tuna are the smaller skipjack (Katsuwonus pelamis), which are typically one foot (35 centimeters) long and about seven pounds (three kilograms) but can grow up to 40 pounds (18 kilograms), and the bigeye (Thunnus obesus). Bigeye tuna typically grow to about three feet (0.9 meter) and 33–44 pounds (15–20 kilograms) but have been caught at weights of up to 734 pounds (333 kilograms). This species dwells in deep, cool water and has a thick fat layer for insulation, making it a favorite of the sashimi market.

Yellowfin tuna (Thunnus albacares) are found in tropical and subtropical waters, growing up to eight feet (2.4 meters) and 441 pounds (200 kilograms). Yellowfin in the eastern tropical Pacific (ETP) are typically found swimming underneath schools of spinner (Stenella longirostris) and spotted dolphins (S. attenuata).