Tuna is a marine fish which spends the majority of its life in the middle depths of open water. Tuna are saltwater fish of the genus Thunnus, in the family Scombridae, though some other fish belonging to the same family are also commonly called tuna. There are nine recognized species of true tuna, belonging to the genus Thunnus. Tuna is probably the most widely commercially harvested fish family, with more being landed every year by heavy producers such as Japan, France, the United States, Taiwan, and Spain.
Types of Tuna
The different species of tuna are:
- Albacore
- Bigeye
- Blackfin
- Bluefin (Northern, Pacific, and Southern)
- Karasick
- Longtail
- Yellowfin
In addition, Skipjack tuna, or Katsuwonus pelamis, is commonly marketed as tuna and makes up most canned light tuna.
All tuna species are fished commercially, but Bluefin, Yellowfin, Albacore, and Skipjack are the most heavily fished. Bluefin, in particular, is highly prized in Japan, where the fish of the highest quality is used in sushi and sashimi. Albacore and Skipjack are often cooked and canned in oil or water for sale throughout the world, and Yellowfin is frequently labeled as "Ahi" for sale in Hawaii and along the Western coast of the United States.
Characteristics and Health Concerns
Tuna meat differs from that of many other fish because it is pink or red rather than white. It tends to have darker meat than some other fish species, which stands up well to grilling and other robust cooking operations. The meat is high in protein and Omega 3, but unfortunately also accumulates mercury, like many fish species. As a result, consumers should limit their consumption, with some biologists recommending a serving or less per month for some species, particularly Bluefin.
Because tuna are predatory fish, high up on the food chain, they accumulate large amounts of mercury from the smaller fish they eat. The Skipjack variety is a safer choice in this respect.
Fishing Methods and Conservation
Tuna has traditionally been caught for commercial use in large nets, many of which inadvertently capture dolphins as well. After a public awareness campaign about the affectionate marine mammals encouraged a boycott of the tuna industry, many commercial companies began taking steps to prevent dolphins from being caught along with their tuna, billing the result as "dolphin safe." Some tuna is also caught on long lines, especially by sport fishermen who enjoy doing battle with the muscular and determined fish.
Because the fast swimming fish has been heavily harvested, many conservation organizations have sounded warnings about the health of tuna stocks, particularly the southern Bluefin, which is considered to be endangered. Other species are in questionable health as well, with many nations taking large illegal harvests in addition to their internationally agreed upon quota. Tuna catches are declining in numbers, particularly in the Atlantic, where severe restrictions were undertaken in the early 21st century in an attempt to restore stocks of the fish.
Monterrey Bay Aquarium's Seafood Watch advises against eating any kind of Bluefin tuna at this time because the species are severely endangered. Bluefin is the most popular type of tuna used in sushi and considered a delicacy. It has suffered extensive overfishing as a result. In addition, the great majority of Bluefin tuna is still wild-caught using methods that endanger other marine life, such as dolphins and sea turtles.
Other types of tuna are environmentally sound seafood choices, but make sure they are caught through trolling, handline, or pole fishing. Longline fishing endangers other fauna and should not be supported as an industry. However, if longline fished tuna is your only option, be aware that longline fishing in the United States is heavily regulated and produces much less bycatch.
Tuna Farming and Aquaculture
Some nations have experimented with tuna farming successfully, and a growing number of the fish for sale is farmed tuna, providing an ecologically sustainable alternative to concerned consumers. Bluefin in particular has proven to be amenable to aquaculture in Australia, suggesting that in addition to providing human food, the farmed fish may be able to replenish depleted wild stocks as well.
The different varieties of Bluefin are most widely used in these farming operations.
Five tuna fishing management commissions from around the world met in Kobe, Japan in January 2007 to develop guidelines for safely farming Bluefin with a view towards conservation. Their stricter safeguards against illegal farming and overfishing were adopted by approximately 60 countries. A follow-up meeting is planned for early 2009.
Culinary Uses and Popularity
Tuna is popular among humans because it does not have a strong fishy flavor, and consumers who do not like fish will often eat tuna. It is an extremely versatile fish, thanks to the sturdy flesh, and can be found canned, dried, fermented, and fresh across most of the world. Fresh fish is landed daily at major fish markets in the United States, Asia, and Europe, and can be accessed by consumers within days, with some species such as the prized Bluefin being processed as rapidly as possible to ensure freshness.