Bluefin Tuna Research

Current Issues in Bluefin Biology and Conservation
Research Methods
Biology of the Bluefin Tuna
Recent Publications

Biology of the Bluefin Tuna

General Information:
Giant bluefin tuna are the largest living species of tuna, reaching up to 10 feet in length and weighing up to 1,400 pounds. A bluefin's lifespan is believed to be longer than 20 years. Bluefin are the largest bony fish inthe world and are considered by many to be the strongest. Their torpedo-shaped bodies and ability to retracttheir pectoral fins and eyes enable them to move the water with reduced friction, reaching up to 25 mph in short spurts. Bluefin can migrate up to 5,000 miles of open ocean --the length of the entire sea -- in just 50days, most likely in search of food.

Bluefin tuna are found in all of the world's oceans. In the western Atlantic, their range extends from Labrador to Brazil; in the eastern Atlantic, from the Lofoten Islands off Norway to northern west Africa. In the eastern Pacific, bluefin tuna have been known to migrate as far north as the Gulf of Alaska. Generally, they are found in the waters off Baja California and southern California. In the western Pacific, depending on the time of year, they are found in concentrations around Japan and the northern Philippines.

A Valuable Commodity:

Just one these animals can net from $5,000 to $30,000 at the dock, although typical prices in the late 1990's range from $3-$12 per pound. Fishermen use rod and reel, hand-thrown harpoon, or purse seine techniques to catch the fish. Aquarium researchers and the East Coast Tuna Association have worked with spotter pilots from 1993-1997 to help develop a more accurate assessment of the size of New England's bluefin tuna population.

Population Background:
Concern for the status of their population has helped make bluefin tuna a research priority. Believed by many to be fast becoming a depleted resource, bluefin tuna have been at the center of a heated debate. The International Council for the Conservation of Atlantic Tuna ( ICCAT ), the body responsible for tuna regulationglobally, has been recommending increasingly stringent fishing limits. According to ICCAT, the bluefin population has declined by more than 70-80% during the last 20 years. Fishermen, however, claim they see morebluefin tuna in a single day than regulators have said exist in the entire North Atlantic. Today, bluefin are subject to strict international quotas in the Western Atlantic, and the National Marine Fisheries Service considers them a depleted resource.

To ensure that tuna stocks are not overfished, regulators need to know exactly where bluefin tuna spend their time and where they reproduce. A highly migratory species, bluefin tuna spend much of their time foraging off the continental shelf, and then disperse to spawning areas, believed to be in the Mediterranean, the Gulf of Mexico. Recent findings suggest that there may be other spawning areas for Altantic bluefin, but this remains inconclusive. Their travels are not well understood or documented.

Since 1982, ICCAT has made decisions based on the assumption that there are two distinct eastern andwestern populations of bluefin tuna in the North Atlantic. But in 1994, the U.S. National Academy of Science indicated that there may actually be just one interbreeding populatio he Aquarium's research program is a multi-year, multi disciplinary study to determine what's actually happening out there.