Swordfish
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| Xiphias gladius Linnaeus, 1758 |
Swordfish is hte common name for a large, highly migratory, predatory marine fish, Xiphias gladius, characterized by a long, flat bill, the lack of pelvic fins, and an absence of scales and teeth in adults. They are the sole member of their family Xiphiidae.
They reach a maximum size of 177 in. (455 cm) and 1,400 lb (650kg). The International Game Fish Association's all-tackle angling record for a swordfish was a 1,182 lb (536.15 kg) specimen taken off Chile in 1953.
Note: Sailfish is the common name for any of the large marine fish comprising the genus Istiophorus in the Istiophoridae family of the Perciformes order, characterized by a dorsal fin that is very long, sail shaped, and taller than body depth and by an elongated premaxillary bill resembling that of the swordfish and other billfish.
They are the sole member of their family Xiphiidae.
Description
Suborder and family placement and characteristics
Sailfish are part of the suborder Scombroidei. The suborder includes species that likely are the fastest swimming fish in the world, including bluefin tuna, swordfish, and sailfish (Nelson 1994, p. 424). Other members of the suborder include barracudas, mackerels, and snake mackerels. Members of the suborder are characterized by an upper jaw that is not protrusible, with the premaxilla fixed (an adaptation to feeding on larger prey) (Nelson 1994, p. 424).
Traditionally, sailfish were placed together with sailfishes, marlins, and spearfishes in the family Xiphiidae (Nelson 1994). That is, all the fish known as billfishes were placed together in this one family, with four extant genera with 12 species in the family. As a comprehensive billfish family, Xiphiidae was characterized by adults having an elongate, premaxillary bill (or rostum), as well as an inferior mouth, the dorsal fin beginning over the back of the head, and the dorsal fin lacking any true spines and from 37 to 55 rays (Nelson 1994, p. 428). The billfishes also lack finlets behind the dorsal and anal fins, have two anal rays, the pectoral fins are inserted low on the body, the pelvic fins are reduced (one spine and two rays or absent), and the gill membranes are free from the isthmus (Nelson 1994, p. 428).
However, currently there is a tendency to divide the various billfishes into two families, the Xiphidae and Istiophoridae, with the swordfish (Xiphias gladius) the only extant member of Xiphiidae, and the other billfishes placed within three genera within Istiophoridae (ITIS 2004; Agbayani 2008a). That is, the former subfamily Xiphiinae (swordfishes) is raised to the family level as Xiphiidae, and the former subfamily Istiophorinae, with the other billfishes, is raised to the level of the family Istiophoridae.
Istiophoridae (which is considered as the subfamily Istiophorinae by Nelson 1994) and thus sailfishes, are characterized by a rounded bill, elongate pelvic fins, scales (the swordfish in family Xiphiidae lacks scales in adult), jaws with teeth (the swordfish lacks teeth in the adult), a lateral line throughout life, and 24 vertebrae (the swordfish has 26 vertebrae) (Nelson 1994, p. 428). Most prominent of the Istiophoridae is the dorsal fin, which has a very long base, which is sail-like in some species, and is depressible into groove (Nelson 1994, p. 428). The three genera placed in this group are Istiophorus (sailfishes), Tetrapturus (spearfishes), and Makaira (marlins) (Nelson 1994; ITIS 2004).
A notable characteristic of the billfishes is the remarkable ability to practice a form of endothermy, a type of warm-bloodedness where an elevated body temperature is maintained through internal means. Billfish exhibit a type of endothermy known as cranial endothermy whereby only the brain and eyes are warmed (Nelson 1994; Block et al. 1993). They remain "cold-blooded" (specifically poikilothermic) in that they do not maintain constant internal temperatures and the temperature often mirrors the ambient temperature. But by being able to raise the temperature of their brains and eyes, they can have faster eye movements when hunting, which is valued when diving deep into the ocean where the water is very cold.
Sailfish distinguishing characteristics
What distinguishes the What distinguishes the swordfish ..
Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood.
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. Swordfish are not schooling fish. They swim alone or in very loose aggregations, separated by as much as 10 meters from a neighboring swordfish. They are frequently found basking at the surface, airing their first dorsal fin. Boaters report this to be a beautiful sight, as is the powerful jumping for which the species is known. This jumping, also called breaching, is thought by some researchers to be an effort to dislodge pests, such as remora or lampreys. It could also be a way of surface feeding by stunning small fish as they jump out of the water, making the fish more easily captured for food.
Swordfish feed daily, most often at night when they rise to surface and near-surface waters in search of smaller fish. They have been observed moving through schools of fish, thrashing their swords to kill or stun their prey and then quickly turning to consume their catch. In the western North Atlantic, squid is the most popular food item consumed. But fish, such as menhaden, mackerel, bluefish, silver hake, butterfish, and herring also contribute to the swordfish diet.
Swordfish are vigorous, powerful fighters. When hooked or harpooned, they have been known to dive so quickly that they have impaled their swords into the ocean bottom up to their eyes. Although there are no reports of unprovoked attacks on humans, swordfish can be very dangerous when harpooned. They have run their swords through the planking of small boats when hurt.
The adults have few natural enemies, with the exception of large sharks and sperm and killer whales. They are easily frightened by small boats, yet paradoxically, large craft are often able to draw very near without scaring them. This makes swordfish easy to harpoon.
The swordfish is often mistaken for the sailfish, with which it shares a striking resemblance. However the Swordfish would only be mistaken as a sailfish by a novice angler. Sailfish are relatively weak with a huge dorsal fin and can be caught on light tackle. Swordfish have a tiny dorsal and most anglers will tell you that pound for pound they are the strongest fish in the sea.
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, the 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.
Harvest
Swordfish were harvested by a variety of methods at small scale until the global expansion of long-line fishing. Longline gear can be targeted to a variety of fish, but bycatch remains a significant problem.
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[3]. 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. (See mercury poisoning for more details.)
Conservation status
Swordfish is not listed as an endangered species. [3]
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. [4]
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. [5]
Recreational Importance
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| game fishing |
| big game |
| swordfish |
| marlin |
| bass |
| sharks |
| salmon run |
| sport fish |
| fly fish |
| IGFA |
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| angling |
| recreational |
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| I N D E X |
{{#invoke:Message box|ambox}} 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 the coast of South Florida.
To catch a swordfish off Florida, most anglers 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. Swordfishing can also be done during the day.
In Popular Culture
- In the video-game Donkey Kong Country (and in many other Donkey Kong games) a swordish named Enguarde can be ridden in underwater stages and helps the player to defeat enemies.
- 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.
Notes
- ↑ J. Sepkoski, "A compendium of fossil marine animal genera," Bulletins of American Paleontology 364 (2002): 560. Retrieved May 22, 2008.
- ↑ Safina 1996. [1]. 2006 IUCN Red List of Threatened Species., World Conservation Union. Retrieved on 12 May 2006.
- ↑ [2] "What you need to know about mercury in fish and shellfish."
ReferencesISBN links support NWE through referral fees
- 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?
- Template:FishBase species
- Integrated Taxonomic Information System (ITIS). 2004a. Xiphiidae ITIS Taxonomic Serial No.: 172480. Retrieved June 1, 2008.
- Integrated Taxonomic Information System (ITIS). 2004b. Istiophoridae ITIS Taxonomic Serial No.: 172486. Retrieved June 1, 2008.
- Nelson, J. S. 1994. Fishes of the World, 3rd ed. New York: John Wiley & Sons. ISBN 0471547131.
- Sepkoski, J. 2002. A compendium of fossil marine animal genera Bulletins of American Paleontology 364: 560. Retrieved May 22, 2008.
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
- http://www.state.mi.us/mdoc/asp/otis2profile.asp?mdocNumber=914751
Gallery
Xiphias gladius
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