Fish Facts » Bluefin Tuna
Description
The bluefin tuna is one of the largest of the tunas. The body is deepest near the insertion of the pelvic fins, and tapers significantly to the caudal peduncle. Compared to other tunas, the head is long and somewhat pointed, and the eye is small. Two dorsal fins are present, with a small space separating them. The second dorsal fin is taller than the first, and is followed by 7 to 10 finlets. The anal fin begins well behind the insertion of the second dorsal fin. The pectoral fins are short compared to other members of the genus Thunnus, although the relative length changes with age. The pectoral fins never reach as far back as the space between the dorsal fins. Three keels are present on the caudal peduncle. The body is a metallic deep blue above and the lower sides and belly are silvery white. In fresh specimens, alternating colorless lines and rows of dots can be seen along the lower sides. The first dorsal fin is yellow or blue, the second is red or brown. The anal fin and finlets are yellow, edged with black. The central caudal keel is black.
Habitat
This tuna is epipelagic and oceanic, coming near shore seasonally. It can tolerate a considerable range of temperatures and has been observed both above and below the thermocline, down to depths of greater than 3000 feet (9,850 m). Bluefin tuna exhibit strong schooling behavior while they are young. While schooling is believed to be sight oriented, schools have been observed at night. Therefore, other senses (particularly the lateral line) appear to be involved in this behavior. Schools of bluefin seasonally migrate northward during the summer months along the coast of Japan and and the Pacific coast of North America. Tagged adult fish have made trans-Pacific migrations: some eastward, and some westward. Other tagging studies have shown that a bluefin can cross the Atlantic in less than 60 days. They can swim at speeds up to 45 mph (72.5 kph).
Diet
Bluefin exhibit different feeding strategies, dependent upon their targeted prey. A quick, energetic pursuit is used in obtaining smaller schooling fishes, particularly anchovies, while "modified filter feeding" is used to catch small, slow moving organisms. Bluefin feeding near shore have been recorded to eat starfish, kelp, and smaller shallow water fishes. Bluefin are less likely to feed during the spawning season, when the majority of their activity must be dedicated to spawning activities. Their major competitors for food are marine mammals and other large fish, notably other scombrids and billfishes.
Fishery
The bluefin is highly valued as a food fish around the world. It is sold fresh or frozen. Quality fish are especially favored in Japan, where they can fetch a high price in the raw seafood market. A single fish can sell for $45,000 USD. The bluefin tuna is also a popular game fish, especially in the USA, where it is caught by hook and line. In some areas, it is reported that bluefin do not readily take bait. Instead, they will bite only when in mixed schools including albacore or yellowfin. Scientists speculate that the intense feeding activity of these other species may stimulate a feeding response in bluefin tuna.
Size
The maximum length reported is 180 inches (458.0 cm) total length and the maximum weight reported is 1,506 lbs. (684 kg). Bluefin commonly attain a size of 78 inches (200 cm). The International Game Fish Association (IGFA) all-tackle record is 1496 lb. (679 kg). This tuna has a life span of approximately 15 years.
Range
The bluefin tuna is distributed throughout the Atlantic and Pacific Oceans in subtropical and temperate waters. In the western Atlantic Ocean, it is found from Labrador, Canada, to northern Brazil, including the Gulf of Mexico. In the eastern Atlantic Ocean, it is found from Norway to the Canary Islands. In the western Pacific Ocean, it is distributed from Japan to the Philippines. In the eastern Pacific Ocean, it is distributed from the southern coast of Alaska, USA to Baja California, Mexico.
Source(s)
Florida Museum of Natural History
Source(s) on the web
http://www.flmnh.ufl.edu/fish/gallery/descript/bluefintuna/bluefintuna.html