Swordfish (Xiphias gladius; from Greek ξίφος: sword, and Latin gladius: sword), also known as broadbill in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a popular sport fish of the billfish category, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood. These fish are found widely in tropical and temperate parts of the Atlantic, Pacific and Indian oceans, and can typically be found from near the surface to a depth of 550 m (1,800 ft). They commonly reach 3 m (9.8 ft) in length, and the maximum reported is 4.55 m (14.9 ft) in length and 650 kg (1,400 lb) in weight.They commonly reach 3 m (9.8 ft) in length, and the maximum reported is 4.55 m (14.9 ft) in length and 650 kg (1,400 lb) in weight. The International Game Fish Association's all-tackle angling record for a swordfish was a 1,182 lb (536 kg) specimen taken off Chile in 1953. Females are larger than males, and Pacific swordfish reach a greater size than northwest Atlantic and Mediterranean swordfish. They reach maturity at 4–5 years of age and the maximum age is believed to be at least 9 years.
Swordfish are ectothermic animals; however, swordfish, along with some species of shark, have special organs next to their eyes to heat their eyes and brain. Temperatures of 10 to 15 °C above the surrounding water temperature have been measured. The heating of the eyes greatly improves their vision, and consequently improves their ability to catch prey. Out of the 25,000+ fish species, only 22 are known to have a mechanism to conserve heat. These include the swordfish, marlin, tuna and some sharks.
From : http://en.wikipedia.org/wiki/Swordfish