The Tuna is one of the most useful and utilized resource of the ocean. It is the most heavily commercially fished species at this time. They are a very community oriented fish, making them easy to catch in large numbers, and the meat they provide is extremely nutritious and tasty. The most common sub-species is the Atlantic Tuna
The Atlantic Tuna varies greatly in size, from the skipjack and blackfin, smaller species that rarely exceed three feet, to the northern bluefin, which can grow up to over 10 feet and half a ton in weight (also the world's largest living bony fish). The largest bluefin ever caught on a rod and reel weighed in at 1,496 pounds. The common range is somewhere between 15 in and 6 feet in length. Albacore, a common species of tuna used for food, generally don't grow to be longer than 4 feet.
Methods of Catch
The majority of tuna are harvested using one of 3 methods: purse seining, longlining, and pole and line. The method varies depending on location and species. The pole and line fishing from baitboats is the technique used for over 40% of the world's catch. Longlining, as the name hints towards, involves setting a line at the surface that can stretch for up to 80 miles. Numerous baited hooks are suspended from the line at intervals from 180-500 feet down. Purse seines are huge nets that are set around a school of fish. They are closed first at the bottom, then drawn out of the water. They can be up to 1 mile long.
Reproduction and Longevity
The age of tuna at sexual maturity varies depending on species from about 3 to 5 years. A female can spawn as many as 100,000 eggs per kilogram of body weight. The eggs are ready to hatch after only about 30 hrs, but very few survive to adulthood. Tuna grow very rapidly, and have a long lifespan. For example, Albacore have been estimated to live approximately 9 years, and bluefin are thought to reach an age of over 30.