Revealing Tuna Secrets

The Northern bluefin tuna (Thunnus thynnus in the Atlantic and Thunnus orientalis in the Pacific) is among the most remarkable fishes in the ocean. Atlantic bluefins can grow to more than 12 feet in length, weigh in excess of 1,500 pounds and live for 25 to 30 years; Pacific bluefins are somewhat smaller. They are capable of swimming at speeds approaching 25 miles per hour, and are warm blooded—able to maintain a body temperature above that of the water in which they swim. They are capable of trans-oceanic migrations in 21 days.

Our demand for tuna threatens bluefins

Bluefin tuna are also the basis of an incredibly lucrative commercial fishery, one that in some regions has led to steep declines over the past three decades because of growing pressure to catch these valuable giants. A single giant Atlantic bluefin tuna can sell for $100,000 or more in Japan. Tuna fisheries worldwide generate billions of dollars annually, making them among the most valuable fisheries on Earth. The growing demand for bluefin tunas increasingly is a cause for concern throughout the global oceans.

To conserve tunas, we need to know more about them

To conserve tunas, we need to learn more about them and put our knowledge into action—so fishermen can continue to fish, and tunas can continue to thrive.

Since 1994, staff at the Tuna Research and Conservation Center — between the aquarium and Stanford University—has been tagging giant bluefin tunas in the wild and studying tunas at the TRCC facility in Pacific Grove, next door to the aquarium.

a collaboration They currently have computerized tags in 550 giant Atlantic bluefin and 100 Pacific tuna. The devices collect data about tuna migrations across ocean basins, their internal body temperature and diving patterns. Data coming back from the tags is helping shape management policies for bluefin fisheries in the Atlantic, where mature bluefin tuna populations in the Western Atlantic have plummeted since the 1970s because of increased fishing pressure.

TRCC tagging in the western Atlantic has revealed that bluefin tunas are mixing on their feeding grounds but potentially sorting to independent breeding grounds in the Mediterranean and the Gulf of Mexico, a pattern not accounted for in current fisheries management policies. Some fish have carried tags and stored nearly four years of data before they were caught and the tag information recovered.

Now TRCC researchers have embarked on a four-year effort to tag 1,000 Pacific bluefin tunas as part of the larger Tagging of Pacific Predators initiative that will document the migrations of tunas, sharks, squid and other open ocean species in the eastern Pacific.