There are eight tuna species in the Thunnus genus:
- Albacore, Thunnus alalunga (Bonnaterre, 1788).
- Yellowfin tuna, Thunnus albacares (Bonnaterre, 1788).
- Blackfin tuna, Thunnus atlanticus (Lesson, 1831).
- Southern bluefin tuna, Thunnus maccoyii (Castelnau, 1872).
- Bigeye tuna, Thunnus obesus (Lowe, 1839).
- Pacific bluefin tuna, Thunnus orientalis (Temminck & Schlegel, 1844).
- Northern bluefin tuna, Thunnus thynnus (Linnaeus, 1758).
- Longtail tuna, Thunnus tonggol (Bleeker, 1851).
Species of several other genera (all in the family Scombridae) have common names containing "tuna" and are part of the tribe Thunnini:
- Skipjack tuna Katsuwonus pelamis (Linnaeus, 1758)
- Slender tuna Allothunnus fallai (Serventy, 1948)
- Bullet tuna Auxis rochei rochei
- Frigate tuna Auxis thazard thazard
- Kawakawa (little tunafish or mackerel tunafish) Euthynnus affinis (Cantor, 1849)
- Little tunny (little tunafish) Euthynnus alletteratus
Two others outside the tribe Thunnini are sometimes considered tunas:
- Butterfly kingfish (Butterfly mackerel) Gasterochisma melampus (Richardson, 1845)
- Dogtooth tuna Gymnosarda unicolor (Rüppell, 1836)
Commercial importanceTuna cut in half for processing at the Tsukiji fish market in Tokyo, JapanA grilled tuna steak served in a French bistro
Tuna has been an important commercial fish for centuries. It was first canned in 1903 and is now probably the most popular fish for canning. The best known tunas for canning are the albacore, bluefin, and yellowfin, with the high-fat albacore also having the lightest color flesh and being the only tuna whose meat can be called "white," although it is actually white with a hint of pink. Yellowfin tunas have a slightly stronger flavor than albacore and have pale pink flesh (labeled "light" not "white"). In bluefin tunas, the largest tunas, the young have a lighter and less strongly flavored flesh than the adults, whose flesh is dark red (Herbst 2001).
In addition to its major use for canning, tuna is sold as steaks, fillets to be cooked, and for consumption uncooked. The northern bluefin tuna is an important food fish used almost exclusively as raw meat for sashimi and sushi. Canned tuna is precooked, and packed in either water or oil, and sold in the three grades of flaked or grated (bits and pieces), chunk (small pieces), and solid or fancy (large pieces) (Herbst 2001).
Tuna is a good source of lean protein, vitamins, minerals, and omega-3 fatty acids (USTF 2006), and can lower blood pressure and cholesterol. Omega-3 fatty acids have been shown to lower the risk of heart disease, ease the pain of arthritis, and reduce asthma complications (USTF 2006).
According to Foodmarket Exchange, the total tuna catch in 2000 stood at 3,605,000 tons, down about 5.7 percent from 3,823,000 tons in 1999. The main tuna catching nations are concentrated in Asia, with Japan and Taiwan as the main producers. Other important tuna catching nations in Asia are Indonesia and South Korea. Spain and France also are important tuna fishing countries, mainly catching in the Mediterranean Sea and the Indian Ocean.
Japan remains the main nation fishing for tuna in the Pacific. In 2000, total tuna caught by Japanese vessels stood at 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 total tuna 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.
Increasing quantities of high-grade tuna are entering the market from operations that fatten tuna in net pens by feeding them such baitfish species as sardines, mackerel, herrings, and squid, often caught in fisheries far removed from the fish farming sites. The southern bluefin tuna, Thunnus maccoyii, is farmed in Australia, while its close relative, the northern bluefin tuna, Thunnus thynnus, is being fattened in farms in the Mediterranean Sea, the Gulf of Mexico, and coastal waters of Japan and Australia.
Due to their high position in the food chain and the natural accumulation of heavy metals up the food chain, some of the larger species of tuna, such as bluefin and albacore, can have relatively high levels of mercury. As a result, in March 2004, the United States Food and Drug Administration (FDA) issued guidelines recommending that pregnant women, nursing mothers, and children limit their intake of tuna and other types of predatory fish (USDHHS 2004). They noted, for example, that albacore ("white") tuna has more mercury than canned light tuna. Most canned light tuna is skipjack tuna, which is lower in mercury. The eastern little tuna (Euthynnus affinis) has recently come to market as a low-mercury, less expensive substitute for canned albacore.
Management and conservation
Some varieties of tuna, such as the bluefin and bigeye tuna, Thunnus obesus, are threatened by overfishing, which has dramatically affected tuna populations in the Atlantic and northwestern Pacific Oceans. The fisheries of some other populations, such as the central and western Pacific skipjack tuna, Katsuwonus pelamis, seem to remain healthy.
There is mounting evidence that the accumulation of excess harvesting capacity threatens tuna fisheries worldwide. Furthermore, international agreement regulations in catch limits and size of nets (no larger than 2.4 kilometers or 1.5 miles) are not always observed. The Australian Government alleged in 2006, for example, that Japan had illegally overfished southern bluefin for years. At a meeting of the Commission for the Conservation of Southern Bluefin Tuna in 2006, the Japanese delegation admitted that its catch of southern bluefin tuna for 2005 was some 1,800 tons more than its 6,065-ton quota for that year and agreed to a halving of its quota to 3,000 tons per year for the five years beginning in 2007.1
The bluefin tuna of all three species-northern, southern, and Pacific-are overfished throughout the world. They are hooked on longlines or illegally netted everywhere they swim, and many young bluefins are captured before they reproduce and placed inside a fish farm enclosure where they are fattened for harvest. Creating effective fishing policies for bluefin tuna is difficult since they are highly mobile and swim through the territorial waters of many different nations.
Use of drift nets also captures seals, dolphins, whales, and birds. Many tuna species, such as yellowfin tuna, associate with dolphins, swimming along side them, with dolphins being caught by fishermen seeking tuna. Tuna species that do not normally associate with dolphins include albacore and skipjack. Methods of fishing tuna have become more "dolphin friendly," becoming less prone to entangle, injure, or kill dolphins. However, there is no universal independent inspection program or verification of "dolphin safeness" to show that dolphins are not harmed during tuna fishing. According to the Consumers Union, this gives the claims such as "dolphin safe" little credibility.
There are five main tuna fishery management bodies. The five are the Western Central Pacific Ocean Fisheries Commission, the Inter-American Tropical Tuna Commission, the Indian Ocean Tuna Commission, the International Commission for the Conservation of Atlantic Tunas, and the Commission for the Conservation of Southern Bluefin Tuna.
- ↑ "Japan Admits to Overfishing Southern Bluefin Tuna," Kyodo News (October 16, 2006). Available online from NoWhaling.com, by Francisco G. F. F. Gonçalves. Retrieved July 31, 2007.
- Clover, C. 2004. The End of the Line: How Overfishing is Changing the World and What We Eat. London: Ebury Press. ISBN 0091897807.
- Collette, B. B., and C. E. Nauen. 1983. Scombrids of the World: An Annotated and Illustrated Catalogue of Tunas, Mackerels, Bonitos, and Related Species Known to Date. FAO species catalogue, v. 2. Rome: United Nations Development Programme. ISBN 9251013810.
- Herbst, S. T. 2001. The New Food Lover's Companion: Comprehensive Definitions of Nearly 6,000 Food, Drink, and Culinary Terms. Barron's Cooking Guide. Hauppauge, NY: Barron's Educational Series. ISBN 0764112589.
- Nelson, J. S. 1994. Fishes of the World, 3rd ed. New York: John Wiley & Sons. ISBN 0471547131.
- U.S. Department of Health and Human Services and the U.S. Environmental Protection Agency (USDHHS). 2004. What you need to know about mercury in fish and shellfish. EPA-823-R-04-005. Retrieved August 9, 2007.
- U.S. Tuna Foundation (USTF). 2006. Health benefits of tuna. U.S. Tuna Foundation. Retrieved August 9, 2007.
All links retrieved December 21, 2015.
- Sushi Items - Maguro (Tuna).