Thunnus thynnus
Atlantic bluefin tuna
(Also: atún; bluefin tuna; horse mackerel; northern bluefin tuna; thon rouge)

Bluefin tuna are distributed throughout the Atlantic and Pacific Oceans in subtropical and temperate waters. In the western Atlantic Ocean, they are found from Labrador, in Canada, to northern Brazil, including the Gulf of Mexico. In the eastern Atlantic Ocean, they are found from Norway to the Canary Islands. In the western Pacific Ocean, they are found from Japan to the Philippines. In the eastern Pacific Ocean, they are found from the southern coast of Alaska to Baja California, Mexico. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

Bluefin tuna are marine fishes, they occupy both coastal and pelagic waters. They occupy depths from the surface to 1000 meters. They live in tropical, subtropical, and temperate waters. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Jeffries, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

Bluefin tuna are the largest of the tunas. They have a long pointed head and small eyes. Bluefin tuna have two dorsal fins with a small space between them and short pectorial fins. Their anal fin begins far behind the second dorsal fin and they have three keels on their caudal peduncle. Bluefin tuna have a metallic blue color on the top half of their bodies and silver from the middle of their sides down to the bottom. Their first dorsal fin is yellow or blue and their second is red or brown. Their anal fin and finlets are yellow edged with black. Their central caudal keel is black. Bluefin tuna are usually between .5 and 2.0 meters in length. They weigh on average between 136 kg and 680 kg (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Jeffries, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

Bluefin tuna larvae hatch at 3.0 mm and have large heads, large jaws, and lack body pigmentation. They do have dorsal tail pigment. After hatching they grow 1 mm per day. The young are on average 5.80 mm after 10 days, 10.62 mm by 20 days, and 35.74 mm by 30 days after hatching. Growth is especially accelerated after 20 days after hatching, up to 2.10 mm/day. Young begin schooling with other species of tuna based on size. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Jeffries, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

In the wild bluefin tuna are expected to live about 15 years. It is estimated that the longest lifespan known in the wild is between 20 and 30 years. Tuna caught and placed in captivity have short life spans because they are kept for a short period of time while they are fattened before harvesting. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Jeffries, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

Bluefin tuna display schooling behavior based on size not species. It is not uncommon to see many different species of similarly sized tuna in a school together. Schools migrate north during summer months along the coast of Japan and the west coast of the United States. Trans Pacific migrations have been observed. Bluefin tuna have been known to cross the Atlantic Ocean in 60 days. Recent tagging data has shown that individual bluefin tuna frequently make several migrations from the eastern Atlantic to the western Atlantic and back again during the course of a year. Bluefin tuna can swim up to 72.5 kph. Because they are capable of high speeds, they are very powerful predators. They form feeding aggregations throughout the Atlantic and Pacific when it is not spawning season. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Jeffries, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

Home Range

The home rane of bluefin tuna is usually only limited to either the Atlantic Ocean or the Pacific Ocean. Individuals frequently migrate throughout the ocean in which they occur. For example, bluefin tuna have been observed to make several trips from the North American Atlantic coast to the European Atlantic coast and back again in a single year. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997)

Bluefin tuna perceive their enviroment and communicate through visual and chemical cues. They also have a well-developed lateral line system. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Scott, 1997)

Bluefin tuna chase down their prey using their ability to swim at very high speeds. They can also use modified filter feeding to catch small, slow moving organisms. They have also been known to eat kelp. They form feeding aggregations throughout the Atlantic and Pacific outside of the spawning season. Very little feeding occurs during spawning season. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Gardieff, 2005; Jeffries, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

Larvae feed on small organisms such as brine shrimp, other fish larvae, and rotifers. Juveniles also feed on small organisms until they become large enough to start feeding on small fish. The prey of adults include smaller fish, squid, eels, and crustaceans.

Predators of bluefin tuna include sharks, large predatory fishes, humans, marine mammals, including killer whales and pilot whales. Their anti-predator behaviors are schooling and the ability to make a fast escape. Their countershaded coloration makes them camouflaged in aquatic environments, their blue coloration dorsally makes them less visible from above and their light ventral coloration makes them less visible when seen from below. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997)

Bluefin tuna are predators in their ecosystem and they are also a source of food for larger predators, including humans. They act as hosts for at least 72 parasites. These include: Euryphorus brachypterus, found in branchial cavities, Brachiella thynni, found on the fins, Pennella filosa, which inserts itself into the flesh of the fish, Pseudocycnus appendiculatus, found on the gill filaments, and Caligus bonito and C. productus which are found on the surface of the body and the wall of the branchial cavities.

They are also mutualists with other tuna species because tunas school in groups of similar sizes and mixed species, rather than groups of the same species. (Gardieff, 2005; Marinebio.org, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

Tuna fishing practices often result in harm to other species, including dolphins and sea turtles. There are potential health risks to humans that come from consuming large amounts of tuna due to mercury contamination in their flesh. Mercury contamination can result in damage to the nervous system, digestive system, respiratory system and kidneys. It can also have damaging effects on the male reproductive system and on developing fetuses. Mercury contamination is usually the result of bioaccumulation of toxins in water as a result of human activities. (Hightower and Rider, 2005; Jeantheau, 2004; Marinebio.org, 2005; Shwartz and Peterson, 2005)

Bluefin tuna are a popular sport fish. A very large and profitable industry has developed around bluefin tuna. They are a popular food item worldwide. (Agustin, Sampang, and Luna, 2005; Miyashita et al., 2001; Scott, 1997; Tudela, 2001)

Many are concerned that bluefin tuna could easily become endangered due to high demand as a food source and resultant overfishing. Because bluefin tuna are migratory, they are often fished in international waters which caused the International Commission for the Conservation of Atlantic Tunas to be created in 1966. The ICCAT proposes management methods, conservation methods, and conducts reseach. Also in 2001 helicopter spotting was banned in the Mediterranean to try to control the amount harvested. Bluefin tuna cannot be breed in captivity. Bluefin tuna farms are not real farms. Tuna are instead caught and fattened rapidly, then processed. (Agustin, Sampang, and Luna, 2005; Figaro, 2005; Miyashita et al., 2001; Scott, 1997)