usa | world | animals | vocabulary | health | science | math | history


Swordfish are large, highly migratory, predatory fish characterized by a long, flat bill in contrast to the smooth, round bill of the marlins. Swordfish are elongate, round-bodied, and lack teeth and scales as adults. They reach a maximum size of 14 ft (4.3 m) and 1,190 lb (540 kg).


 


The Gladiator: The swordfish is known as The Gladiator (gladius) because of the sharp, sword-like bill it wields as a weapon—to spear prey as well as for protection from its few natural predators. The mako shark is one of the rare sea creatures big enough and fast enough to chase down and kill an adult swordfish.


Everywhere you look: Swordfish are distributed throughout the world's marine ecosystem, in tropical, subtropical and temperate waters, between approximately 45° north and 45° south. They tend to concentrate where major ocean currents meet, and along temperature fronts. They inhabit the mixed surface waters where temperatures are greater than 15 °C but also can move and hunt in water as cool as 5 °C for short periods aided by specially adapted heat exchange organs which are able to increase the temperature of their brain and eyes by 10–15 °C.

A Visit to the Islands: Areas of greater apparent abundance occur north of Hawaii along the North Pacific transition zone, along the west coasts of the U.S. and Mexico and in the western Pacific, east of Japan. Migration patterns have not been described although tag release and recapture data indicate an eastward movement from the central Pacific, north of Hawaii, toward the U.S. West Coast. Acoustic tracking indicates some diel movement from deeper depths during the daytime and moving into the mixed surface water at night. At times they appear to follow the deep scattering layer, and small prey, as they undertake these vertical movements.

Matriarchs: Females grow larger than males, as males over 300 lb (135 kg) are rare. Females mature at 4-5 years of age in northwest Pacific while males mature first at about 3 to 4 years. In the North Pacific, batch spawning occurs in water warmer than 24 °C from March to July and year round in the equatorial Pacific. Adult swordfish forage includes pelagic fish including small tuna, dorado, barracuda, flying fish, mackerel, as well as benthic species of hake and rockfish. Squid are important when available. Swordfish likely have few predators as adults although juveniles are vulnerable to predation by large pelagic fish.

Space Heaters:
While swordfish are cold-blooded animals, they have special organs next to their eyes to heat their eyes and also their brain. Temperatures of 10 to 15 C° above the surrounding water temperature have been measured. The heating of the eyes greatly improves the vision, and subsequently improves their ability to catch prey. Out of the 25 000+ species of bony fish, only about 22 are known to have the ability to heat selected body parts above the temperature of the surrounding water. These include the swordfish, marlin, tuna and some sharks.


Deep Sea Divers: Swordfish have been observed spawning in the Atlantic Ocean, in water less than 250 ft. (75 m) deep. Estimates vary considerably, but females may carry from 1 million to 29 million eggs in their gonads. Solitary males and females appear to pair up during the spawning season. Spawning occurs year-round in the Caribbean Sea, Gulf of Mexico, the Florida coast and other warm equatorial waters, while it occurs in the spring and summer in cooler regions.


Spawn:
The most recognized spawning site is in the Mediterranean, off the coast of Italy. The height of this well-known spawning season is in July and August, when males are often observed chasing females. The pelagic eggs are buoyant, measuring 1.6-1.8mm in diameter. Embryonic development occurs during the 2 ½ days following fertilization. As the only member of its family, the swordfish has unique-looking larvae. The pelagic larvae are 4 mm long at hatching and live near the surface. At this stage, body is only lightly pigmented. The snout is relatively short and the body has many distinct, prickly scales. With growth, the body narrows.

By the time the larvae reach half an inch long (12 mm), the bill is notably elongate, but both the upper and lower portions are equal in length. The dorsal fin runs the length of the body. As growth continues, the upper portion of the bill grows proportionately faster than the lower bill, eventually producing the characteristic prolonged upper bill. Specimens up to approximately 9 inches (23 cm) in length have a dorsal fin that extends the entire length of the body. With further growth, the fin develops a single large lobe, followed by a short portion that still reaches to the caudal peduncle. By approximately 20 inches (52 cm), the second dorsal fin has developed, and at approximately 60 inches (150 cm), only the large lobe remains of the first dorsal fin.

All text is available under the terms of the GNU Free Documentation License

   
 


 Kingdom: Animalia

 Phylum: Chordata

 Class: Actinopterygii

 Order: Perciformes

 Family: Xiphiidae

 Genus: Xiphias

 Species: Gladius