Tuna.

Tuna are several species of ocean-dwelling carnivorous fish in the family Scombridae, mostly in the genus Thunnus. Tunas are very fast swimmers—they have been clocked at 70 km/h (45 mph)—and include several species that are warm-blooded. Unlike most fish species, which have white flesh, tuna have flesh that is pink to dark red.

The red coloring comes from tuna muscle tissue's greater quantities of myoglobin, an oxygen-binding molecule. Some of the larger tuna species, such as the bluefin tuna, can raise their blood temperature above that of the water through muscular activity. This ability enables them to live in cooler waters and to survive in a wide range of ocean environments.

While the fishing of many stocks of tuna is sustainable, it is widely accepted that bluefin tuna have been severely overfished, with some stocks at risk of collapse.

The Eastern Pacific Ocean bigeye is also in need of better management in order to maintain sustainability and, in fact, the world's major tuna canneries involved with the International Seafood Sustainability Foundation (ISSF) have agreed to not source from that stock if meaningful conservation measures are not put in place by September 1, 2009.

Commercial fishing

Tuna is an important commercial fish. Some varieties of tuna, such as the bluefin and bigeye tuna, Thunnus obesus, are threatened by overfishing, which dramatically affects tuna populations in the Atlantic and northwestern Pacific Oceans. Other areas seem to support fairly healthy populations of some of the over 48 different species of tuna —for example, the central and western Pacific skipjack tuna, Katsuwonus pelamis—but there is mounting evidence that overexploitation threatens tuna populations worldwide.

The Australian government alleged in 2006 that Japan had illegally overfished southern bluefin by taking 12,000 to 20,000 tonnes per year instead of the their agreed 6,000 tonnes; the value of such overfishing would be as much as USD $2 billion. Such overfishing has resulted in severe damage to stocks. According to the WWF, "Japan's huge appetite for tuna will take the most sought-after stocks to the brink of commercial extinction unless fisheries agree on more rigid quotas".

Increasing quantities of high-grade tuna are entering the market from operations that rear tuna in net pens and feed them a variety of bait fish. In Australia the southern bluefin tuna, Thunnus maccoyii, is one of two species of bluefin tunas that are kept in tuna farms by former fishermen. Its close relative, the northern bluefin tuna, Thunnus thynnus, is being used to develop tuna farming industries in the Mediterranean, North America and Japan.

According to the Foodmarket Exchange, the total tuna catch was 3,605,000 tons in 2000, down about 5.7 percent from 3,823,000 tons in 1999. The main tuna fishing nations are concentrated in Asia, with Japan and Taiwan floating the main fleets. Other important tuna fishing nations in Asia are Indonesia and South Korea. Spain and France are also important tuna fishing countries, with their ships fishing primarily in the Indian Ocean. In southeast Asia, the southern Philippines is an important tuna-producing area, particularly General Santos City and Davao.

Japan remains the main tuna fishing nation fishing in the Pacific. In 2000, total tuna caught by Japanese vessels was 633,000 tons, about 17 percent of the world tuna catch. Taiwan was the second biggest tuna producer at 435,000 tons, or about 12 percent of the world's total catch. Spain supplies most of the yellowfin to European canneries, accounting for 5.9 percent of the total tuna catch, while Ecuador and Mexico dominate the Eastern Pacific Ocean.

Recreational fishing

In the 1950s through 1970s, bluefin tuna were abundant in the waters of Cuba, Bimini and Cat Cay just a few miles off the Florida coast, and were targeted by such fishermen as Ernest Hemingway and Habana Joe aboard his 1938 40-foot Wheeler named Pilar. Word spread quickly among fishermen around the world about the exciting new sport of big-game fishing. Despite the growing popularity of the sport, however, the boats of the day were hardly ideal for the challenges of fighting the prized fish. Most boats used at the time were converted cabin cruisers, which were relatively slow and hard to maneuver.

The Rybovich family of South Florida eventually constructed a boat in 1946 that catapulted the sport and gave birth to a new industry. This boat, the Miss Chevy II, was the first sportfishing boat the world had ever seen.
Merritt gained particular notoriety during the 1950s through the 1970s with its 37- and 43-foot custom sport fishing boats, which together with boats like those being built by Rybovich gave birth to a new category of fishing yachts and helped fuel the growth of big game tuna fishing in the United States and around the world.