![]() ![]() Several species also move vertically through the water column. Some geotagged bluefins have been tracked swimming from North American to European waters and back several times a year. They’re known for long migrations and are capable of traversing great distances. Tunas generally need to eat a lot and move a lot to sustain themselves. The pelagic zone is the largest habitat on Earth, with a volume of 330 million cubic miles. Tunas are pelagic fish, meaning they live beyond the continental shelf in the open sea-not near coral reefs, the sea floor, or shoreline. The bluefin tuna is comfortable in the cold waters off Newfoundland and Iceland, as well as the tropical waters of the Gulf of Mexico and the Mediterranean Sea, where it goes each year to spawn. While most fish are entirely cold-blooded and have body temperatures that match the water around them, some species of tunas have evolved the ability to warm up their swimming muscles temporarily, enabling them to swim at high speeds and migrate from warm to cold waters. They’re among the only partially warm-blooded fish on Earth. Tunas have crescent moon-shaped tails and two dorsal fins on their backs, one of which can be flattened to reduce resistance in the water. The Atlantic bluefin tuna, for example, can swim up to 43 miles per hour the yellowfin can swim even faster. Tunas are known for their sleek, torpedo-shaped bodies designed for speed and endurance. As a result of overfishing, some species, notably bluefin tuna, have been threatened by extinction. Tunas are fished extensively for food, and their speed and agility means that they are also prized by hunters as big game fish. Most eat fish, while some species prefer to feast on cephalopods like squid. Tunas are apex predators, which means they’re at the top of their food chain. They range in size from the four-pound, foot-long bullet tuna up to the Atlantic bluefin tuna, which weighs an average 550 pounds and measures 6.6 feet long on average. (Skipjack, one of the most popular species of canned tuna, aren’t “true tunas.”) Of those, eight are considered “true tunas”: five species of bluefins and three species of yellowfins, all which belong to the genus Thunnus. Tunas comprise fifteen species in the Thunnini family of saltwater fish. ![]()
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