- sleek and streamlined, adapted for speed
- two closely spaced dorsal fins on its back; The first is “depressible” – it can be laid down, flush, in a groove that runs along its back
- Seven to 10 yellow finlets run from the dorsal fins to the tail, which is lunate – curved like a crescent moon – and tapered to pointy tips
- The caudal peduncle, to which the tail is attached, is quite thin, with three stabilizing horizontal keels on each side
- dorsal side is generally a metallic dark blue, while the ventral side, or underside, is silvery or whitish
- unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red
Tunas are widely but sparsely distributed throughout the oceans of the world, generally in tropical and temperate waters at latitudes ranging between about 45° north and south of the equator.
- Their circulatory and respiratory systems are almost unique among fish, enabling them to maintain a body temperature higher than that of the surrounding water.
- Larger specimens are notorious for putting up a fight while hooked, and have been known to injure people who try to catch them, as well as damage their equipment.
- Tuna schools are believed to associate themselves with dolphins for protection against sharks, which are tuna predators.
- among the fastest-swimming pelagic fish – the yellowfin tuna, for example, is capable of speeds of up to 75 km/h (47 mph).
240 lb Yellowfin, caught near Key West in 2002