The Northern bluefin tuna is one of the most remarkable fishes in the ocean, growing to more than 12 feet, weighing 1,500 pounds and living for up to 35 years. It can swim as fast as 25 miles per hour and cross the ocean in 21 days.
Bluefins Under Siege
Bluefin tuna are also the target of an incredibly lucrative fishery—a single giant Atlantic bluefin can sell for $100,000 or more in Japan. This has led to precipitous declines in tuna populations in recent decades.
To conserve tuna, we need to know more about them—so fishermen can continue to fish, and tuna can thrive. Since 1994, staff at the Tuna Research and Conservation Center (TRCC)—a partnership between the Aquarium and Stanford University—has been tagging giant bluefin tuna in the wild and studying tuna at the TRCC facility next door to the Aquarium. It's the only place in the U.S. where live tuna are kept for research. Four tanks from 5,000 to 86,000 gallons, each with its own life-support system, hold fast-swimming tuna that can grow to hundreds of pounds.
Our unique mix of laboratory and field research is helping inform ecosystem-based management policies that will ensure that these animals thrive. The team studies molecular, biochemical and physiological characteristics, and has developed electronic tracking devices that provide detailed records of the migrations and behaviors of bluefin tuna.
Tuna is the second most popular seafood worldwide. But since the 1960s, the abundance of tuna and other top ocean predators have decreased globally by up to 90 percent.
Experts warn that without concerted efforts to reduce overfishing and restore depleted stocks, tuna stocks will continue to decline. Bluefin tuna in particular are prized by sushi chefs and the high demand for these fish has taken its toll in the Atlantic, Pacific and Southern Oceans.
Bluefin tuna are slow to mature and many fisheries are catching young bluefin tuna that haven't had a chance to reproduce. Bluefin are also highly migratory, which means many nations, including the U.S. and Japan, need to cooperate on management plans to maintain global populations. Unfortunately, this hasn't happened, though there were signs of progress for Pacific bluefin in late 2010, based on an agreement by the Western and Central Pacific Fisheries Commission. In the Atlantic, the bluefin tuna fishery is managed through the International Commission for the Conservation of Atlantic Tunas.
In addition, bluefin are often caught with longlines that are up to three miles long, with thousands of hooks. These result in large bycatch, including threatened or endangered sea turtles, contributing heavily to the decline of some of these species.
Bluefin tuna ranching is also becoming common, where small bluefin are brought from the wild and fattened in open net pens. This further depletes bluefin stocks, and uses large quantities of fish as feed. Closed lifecycle aquaculture is also being developed, where bluefin are raised from egg to adult in captivity. But this has many of the same issues as ranching, notably the large amount of forage fish required as feed. All types of bluefin are on the Seafood Watch "Avoid" list.
The Monterey Bay Aquarium and the Tuna Research and Conservation Center—neighbors in Pacific Grove, California—are cooperating on a wide range of research initiatives to learn more about bluefin tuna and help inform conservation efforts for this iconic species.
Tuna are challenging to display and research because of their incredible size, strength and speed. We're pioneering techniques for collecting, handling, transporting, caring for and displaying tuna. At any given time dozens of tunas representing three species are swimming in the tanks at the Aquarium and TRCC. Captive tuna allow biologists and aquarists to improve husbandry and veterinary techniques, learn from these amazing animals and develop electronic tagging techniques prior to use in the field.
Tunas are remarkable athletes. They travel vast distances at amazing speeds, made possible by unique adaptations. In recent years researchers have studied the cardiac physiology of tunas to understand exactly how these extraordinary hearts deliver this performance over a range of temperatures, providing clues about why bluefin tuna routinely migrate and dive into much colder waters than yellowfin tuna.
Gene Expression Research
Recently, researchers have used gene markers to help assess the condition of captive tuna in response to tank size, feeding and longevity in captivity. This leads to better techniques for assessing the quality and condition of captive tuna. Gene markers can also provide information on the growth, health and vigor of cultivated tuna stocks, promising breakthroughs for health and reproduction.