Swordfish

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This article is about a type of fish.. For other uses, see Swordfish (disambiguation).

Swordfish

Conservation status

Data deficient (IUCN) ^[1]

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Xiphiidae
Genus:	Xiphias
Species:	X. gladius

Binomial name

Xiphias gladius
Linnaeus, 1758

Range map

They are the sole member of their family Xiphiidae.

1 Physiology
2 Distribution
3 Reproduction
4 Swordfish in cooking
5 Swordfish endangered
6 References
7 External links
8 Gallery

[edit] Physiology

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 shortfin mako shark is one of the rare sea creatures big enough and fast enough to chase down and kill an adult swordfish, but they don't always win. Sometimes in the struggle with a shark a swordfish can kill it by ramming it in the gills or belly^{[citation needed]}.

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.

Swordfish skeleton at the National Museum of Natural History, Washington, DC

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.

[edit] Distribution

[edit] Reproduction

Swordfish testing 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. 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 elongated, 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.

[edit] Swordfish in cooking

Marinated swordfish

Swordfish is a particularly popular fish for cooking. Since swordfish are large animals, meat is usually sold as steaks, which are often grilled. The color of the flesh varies by diet, with fish caught on the east coast of North America often being rosier.

However, many sources including the United States Food and Drug Administration warn about potential toxicity from high levels of methylmercury in swordfish^[2]. The FDA recommends that women who are pregnant or who may become pregnant should eat no more than one seven-ounce serving a month; others should eat no more than one serving a week.

[edit] Swordfish endangered

Due to commercial fishing, the average swordfish has dropped from 260 pounds in 1960 to 90 pounds in 1996^[3]. The numbers of North Atlantic swordfish have dropped to less than 50% of what they were just 20 years ago and U.S. commercial fisherman account for about a third of the worldwide catch. This alarming decline is largely due to the popularity of this species by seafood lovers. A major part of the problem is related to over-fishing, general absence of regulations regarding fish harvest during critical periods, no minimum fish size, and lack of protection for spawning and nursery areas.^[4] This fish has been included on many endangered fish lists including the Audubon Society and others.

[edit] References

^ Safina (1996). Xiphias gladius. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 12 May 2006.
^ [1] "What you need to know about mercury in fish and shellfish."
^ [2] "Lines of Death: Longlining and bycatch."
^ Clover, Charles. 2004. The End of the Line: How overfishing is changing the world and what we eat. Ebury Press, London. ISBN 0-09-189780-7