Boaters report this to be a beautiful sight, as is the powerful jumping for which the species is known. They are frequently found basking at the surface, airing their first dorsal fin. They swim alone or in very loose aggregations, separated by as much as 10 m (35 ft) from a neighboring swordfish. Research on related marlin ( Istiophorus platypterus) suggest a maximum value of 36 km/h (22 mph) is more likely. It is no doubt among the fastest fish, but the basis for the frequently quoted speed of 100 km/h (60 mph) is unreliable. Mainly, the swordfish relies on its great speed and agility in the water to catch its prey. The use as an offensive spear in case of dangers against large sharks or animals is under review. Their nose is more likely used to slash at its prey to injure the prey animal, to make for an easier catch. The popular belief of the "sword" being used as a spear is misleading. Swordfish skeleton at the National Museum of Natural History, Washington, DC Movements and feeding These include the swordfish, marlin, tuna, and some sharks. Of over 25,000 fish species, only 22 are known to have a mechanism to conserve heat. The heating of the eyes greatly improves their vision, and consequently improves their ability to catch prey. Temperatures of 10 to 15 ☌ (18 to 27 ☏) above the surrounding water temperature have been measured. Swordfish are ectothermic animals however, along with some species of sharks, they have special organs next to their eyes to heat their eyes and brains. Swordfish ages are derived, with difficulty, from annual rings on fin rays rather than otoliths, since their otoliths are small in size. The oldest swordfish found in a recent study were a 16-year-old female and 12-year-old male. They reach maturity at 4–5 years of age and the maximum age is believed to be at least 9 years. Females are larger than males, and Pacific swordfish reach a greater size than northwest Atlantic and Mediterranean swordfish. The International Game Fish Association's all-tackle angling record for a swordfish was a 536 kg (1,182 lb) specimen taken off Chile in 1953. They commonly reach 3 m (10 ft) in length, and the maximum reported is 4.55 m (14 ft 11 in) in length and 650 kg (1,430 lb) in weight. Unlike modern taxa these have equally long lower jaws. Several extinct genera are known, such as a large sized Xiphiorhynchus and Aglyptorhynchus. This makes it superficially similar to other billfish such as marlin, but upon examination, their physiology is quite different and they are members of different families. The species name, Xiphias gladius, derives from Greek ξιφίας ( xiphias, "swordfish"), itself from ξίφος ( xiphos, "sword") and from Latin gladius ("sword"). The swordfish is named after its long pointed, flat bill, which resembles a sword. They are the sole member of their family, Xiphiidae. 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), and exceptionally up to depths of 2,234 m. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood. They are a popular sport fish of the billfish category, though elusive. Swordfish ( Xiphias gladius), also known as broadbills in some countries, are large, highly migratory predatory fish characterized by a long, flat, pointed bill.
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