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NATURAL HISTORY

ATLANTIC BLUEFIN TUNA } Thunnus thynnus
FAMILY: Scombridae

DESCRIPTION: Sleek giants with blue and gray coloring, bluefin tuna are one of the largest fish in the ocean and can grow to weigh more than 1,000 pounds. Their bodies are muscular, and they have short pectoral fins compared to other tunas.

HABITAT: Northern bluefin tuna are found throughout the North Atlantic Ocean. They can sustain cold and warm temperatures and frequently dive to depths of 500 to 1,000 meters. Spawning habitat for the western population is in the Gulf of Mexico, while the eastern population spawns in the Mediterranean Sea.

RANGE: Atlantic bluefin tuna have historically ranged throughout the Atlantic Ocean, but now exist primarily in the North Atlantic Ocean and associated seas, such as the Mediterranean Sea.

MIGRATION: Atlantic bluefin tuna are highly migratory and they swim across the great Atlantic at speeds up to 55 miles per hour. However, bluefin tuna also have strong homing instincts and faithfully return to the same areas to spawn.

BREEDING: Spawning only once per year, western Atlantic bluefin tuna spawn in the Gulf of Mexico, while the eastern population spawns in the Mediterranean Sea.

LIFE CYCLE: Atlantic bluefin tuna live for about 40 years.

FEEDING: Juvenile and adult bluefin tuna are opportunistic feeders (as are most predators), and their diet can include jellyfish and salps, as well as demersal and sessile species such as octopus, crabs, and sponges. However, in general juveniles feed on crustaceans, fish, and cephalopods, while adults primarily feed on fish like herring, anchovy, sand lance, sardine, sprat, bluefish, and mackerel.

THREATS: Commercial fishing has decimated the Atlantic bluefin tuna population and continues to drive the tuna toward extinction.

POPULATION TREND: The Atlantic bluefin tuna has declined by at least 60 percent in the past 10 years in the eastern Atlantic stock, and by at least 82 percent since 1970 in the western Atlantic stock; both stocks are below 15 percent of their baseline populations.

 

Bluefin tuna photo © Paul Colley