How Much Do Bluefin Tuna Weigh

The Atlantic bluefin tuna is one of the largest, fastest, and most gorgeously colored of all the world’s fishes. Their torpedo-shaped, streamlined bodies are built for speed and endurance. Their coloring—metallic blue on top and shimmering silver-white on the bottom—helps camouflage them from above and below. And their voracious appetite and varied diet pushes their average size to a whopping 6.5 feet in length and 550 pounds, although much larger specimens are not uncommon.

The Atlantic bluefin tuna is a large marine fish and the largest in the “tuna” family. At the age of 30, it can reach 3 meters and exceed 600 kg! Its size and weight at maturity differ according to the geographical area. In the Mediterranean, it is adult at the age of 4 years (i.e. 30 kg for a length of approximately 120 cm) whereas it takes 9 years in the West Atlantic (i.e. 150 kg for approximately 190 cm). The Atlantic bluefin tuna (Thunnus thynnus) is a species of tuna in the Scombridae family. It is variously known as the northern bluefin tuna (mainly when including Pacific bluefin as a subspecies), giant bluefin tuna (for individuals exceeding 150 kilograms or around 330 pounds) and formerly as the tunny.

Bluefin Tuna are known to be highly migratory, with individuals making long migrations every year. These migrations correspond with their spawning behavior and with their food needs. This species reproduces via broadcast spawning, where several females and several males release millions of eggs and sperm into the water column at the same time. This method increases the likelihood that the eggs will be fertilized and decreases the chances that they will be eaten by egg predators. There are at least two known populations of Atlantic bluefin tuna, one that reproduces in the Gulf of Mexico and one that reproduces in the Mediterranean Sea. Some researchers believe that the Mediterranean population actually represents two populations (one in the west and one in the east plus the Black Sea). This further division has some implications for fisheries management, because the fish in the eastern Mediterranean are generally considered more of a conservation concern than those in the western Mediterranean.

General Features Of  A Bluefin Tuna

The body of the Atlantic bluefin tuna is rhomboidal in profile and robust. The head is conical and the mouth rather large. The head contains a “pineal window” that allows the fish to navigate over its multiple thousands of mile range. The color is dark blue above and gray below with a gold coruscation covering the body and bright yellow caudal finlets. Bluefin tuna can be distinguished from other family members by the relatively short length of their pectoral fins. Their livers have a unique characteristic in that they are covered with blood vessels (striated). In other tunas with short pectoral fins, such vessels are either not present or present in small numbers along the edges.

1. Atlantic bluefin tuna are the largest tuna species. The western Atlantic stock reaches a maximum length of 13 (4 m) feet and weight of 2,000 pounds (907 kg),1 while the eastern Atlantic stock reaches a maximum length of 15 feet (4.6 m).2

2. Atlantic bluefin tuna can live for 35 years, possibly longer.2

3. Female Atlantic bluefin tuna produce up to 10 million eggs a year. Eggs hatch 2 days after being fertilized.

4. Atlantic bluefin tuna are top predators, feeding on fish such as herring and mackerel as adults.

5. Atlantic bluefin tuna are characteristically torpedo-shaped with short pectoral fins and a dark red dorsal fin.1

Fight and Speed Of  A Bluefin Tuna

They are prized among sport fishers for their fight and speed, shooting through the water with their powerful, crescent-shaped tails up to 43 miles per hour. They can retract their dorsal and pectoral fins into slots to reduce drag. And some scientists think the series of “finlets” on their tails may even serve to reduce water turbulence.

Diet Of  A Bluefin Tuna

Bluefins attain their enormous size by gorging themselves almost constantly on smaller fish, crustaceans, squid, and eels. They will also filter-feed on zooplankton and other small organisms and have even been observed eating kelp. The largest tuna ever recorded was an Atlantic bluefin caught off Nova Scotia that weighed 1,496 pounds.

How Big Can Atlantic Bluefin Tuna Get?

To put it in one word: huge. And that word might even be an understatement in this context. Atlantic bluefin tuna are some of the largest fish species in the world, reaching an average length of 6.5 feet and an average weight of 550 pounds. 

How Much Do Bluefin Tuna Weigh

Fully mature adult specimens average 2–2.5 m (6.6–8.2 ft) long and weigh around 225–250 kg (500–550 lb). The species can reach a maximum length of almost 4.6 m (15 ft). The largest recorded specimen taken under International Game Fish Association rules was caught off Nova Scotia, an area renowned for huge Atlantic bluefin, and weighed 679 kg (1,500 lb). The longest contest between man and tuna fish occurred near Liverpool, Nova Scotia in 1934, when six men taking turns fought a 361 kg (800 lb) tuna for sixty-two hours. Both the Smithsonian Institute and the National Marine Fish Service in North America have accepted that this species can weigh up to 910 kg (2,000 lb), though further details are lacking.

Atlantic bluefin tuna reach maturity relatively quickly. In a survey that included specimens up to 2.55 m (8.4 ft) in length and 247 kg (540 lb) in weight, none was believed to be older than 15 years.[15] However, very large specimens may be up to 50 years old.

Why Are Bluefin Tuna So Big?

Bluefin tuna have insatiable appetites and a wide-ranging diet, meaning they consume nearly everything they come into contact with. A bluefin’s habitat is the ocean, so naturally, they feed on smaller fish, crustaceans, squids, eels and a multitude of other sea creatures. 

So varied is a bluefin tuna’s food palate, in fact, that it is even considered to be an apex, or alpha predator. In other words, they have no one above them on the food chain. Considering what they eat and how much, it’s not surprising that bluefin tuna are as colossal as they can be in many instances.

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