Information about Swordfish

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

Swordfish (Xiphias gladius) are large, highly migratory, predatory fish characterized by a long, flat bill. They are a popular sport fish, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood. The International Game Fish Association's all-tackle angling record for a swordfish was a 1,182 lb (535.15 kg) specimen taken off Chile in 1953.

They are the sole member of their family Xiphiidae.

Physiology

The swordfish is named after its sharp bill, resembling a sword (Latin gladius), which together with its streamlined physique allows it to cut through the water with great ease and agility. Contrary to belief the "sword" is not used to spear, but instead may be used to slash at its prey in order to injure the prey animal, to make for an easier catch. Mainly the swordfish relies on its great speed and agility in the water to catch its prey. One possible defensive use for the sword-like bill is 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.

Females grow larger than males, with males over 300 lb (135 kg) being 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 are thought to have few predators as adults although juveniles are vulnerable to predation by large pelagic fish.

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, and tuna.

Reproduction

Swordfish have also 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.

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.

Harvest

Swordfish were harvested by a variety of methods at small scale until the global expansion of longline fisheries in the 1950-60s. Today in the United States, swordfish are caught by harpoons, handlines, and trawling but the vast majority of catches are on pelagic longlines. In 2003, sport fishermen in the US caught 48.3mt of swordfish, approximately 4.3 percent of the longline catch.

Longline gear can be targeted to a variety of fish, but bycatch remains a significant problem.

Are swordfish endangered?

Swordfish is not listed as an endangered species. [1]

In 1998, the Natural Resources Defense Council and SeaWeb hired Fenton Communications to conduct an advertising campaign to promote their assertion that the swordfish population was in danger due to its popularity as a restaurant entree. [2]

The resulting "Give Swordfish a Break" promotion was wildly successful, with 750 prominent U.S. chefs agreeing to remove North Atlantic swordfish from their menus, and also persuaded many supermarkets and consumers across the country.

The advertising campaign was repeated by the national media in hundreds of print and broadcast stories, as well as extensive regional coverage. It earned the Silver Anvil award from the Public Relations Society of America as well as Time magazine's award for the top five environmental stories of 1998.

Subsequently, the National Marine Fisheries Service proposed a swordfish protection plan that incorporated the campaign's policy suggestions. Then-President Clinton called for a ban on the sale and import of swordfish and in a landmark decision by the federal government, 132,670 square miles of the Atlantic ocean were placed off-limits to fishing as recommended by the sponsors.

Currently:

In the North Atlantic, the swordfish stock is nearly rebuilt, but biomass remains slightly below that at which Maximum sustainable yield is produced, and abundance is increasing. This stock is considered a moderate conservation concern until the stock is fully rebuilt. There are no robust stock assessments for swordfish in the northwestern Pacific or South Atlantic, and there is a paucity of data concerning stock status in these regions. These stocks are considered unknown and a moderate conservation concern. The southwestern Pacific stock is a moderate concern due to model uncertainty, increasing catches, and declining CPUEs (catch per unit effort). Overfishing is likely occurring in the Indian Ocean, and fishing mortality exceeds the maximum recommended level in the Mediterranean, thus these stocks are considered of high conservation concern. [3]

Recreational Importance

Recreational swordfishing throughout the world, and especially in South Florida, has gained tremendous popularity. With the ban on longlining along parts of the eastern seashore, swordfish populations are showing signs of recovery. The recovery is far from complete and is not a fraction of what it was in the 70's when recreational swordfish was discovered off of the coast of South Florida and led by anglers such as Habana Joe.

To catch a swordfish off of Florida, most anglers such as the infamous Habana Joe drift live or dead baits in the Gulfstream. Boats drift beam to sea, which is why center consoles are so popular for this type of fishing. From Miami's Government Cut, Haulover Inlet or Port Everglades, the run to the swordfish grounds is less than 20 miles. Given the speed of the Gulfstream though, and fishing the majority of the night, you may end up as far as 40 to 50 miles from your homeport. From talking to longliners who used to fish in our waters, swordfish can be found in various parts of the Gulfstream, but the majority of recreational anglers fish a corridor of water that is 3 to 4 miles wide, but starts in the upper Keys and ends in Palm Beach. The reason that this area is so popular is due to the bottom terrain. In this lane there are a series of rises and falls in the depth contour which provides upwelling and seems to hold bait better than open expanses of flat bottom.^[3]

Trivia

• The swordfish is often mistaken for the sailfish, with which it shares a striking resemblance.
• In the CSI: NY episode "Dancing With the Fishes," Danny Messer and Sheldon Hawkes investigate the death of a man killed by a swordfish.
• In season 4, episode 84 of Murder, She Wrote (Just Another Fish Story) the co-owner of a restaurant is stabbed to death with a frozen swordfish

References

• Michael Hopkin (2005): Swordfish heat their eyes for better vision. Nature, 10 January 2005
• Fritsches, Kerstin A., Brill, Richard W., and Warrant, Eric J. (2005): Warm Eyes Provide Superior Vision in Swordfishes. Current Biology 15, 55−58
• FDA Consumer:Mercury In Fish:Cause For Concern?
• "Xiphias gladius". FishBase. Ed. Ranier Froese and Daniel Pauly. 10 2005 version. N.p.: FishBase, 2005.

External links

• http://www.flmnh.ufl.edu/fish/Gallery/Descript/Swordfish/Swordfish.html
• More info on FDA Mercury Advice from Oceana
• http://www.fenton.com/pages/3_ourwork/4_casestudies/environment/swordfish.htm
• http://www.mbayaq.org/cr/cr_seafoodwatch/content/media/MBA_SeafoodWatch_SwordfishReport.pdf

Gallery

Xiphias gladius