por He swordfish (Xiphias gladius) It is a marine species that is part of the Xiphiidae family. Its main characteristic is its long and flattened beak, shaped like a sword. This is formed by the fusion and extension of the bones that make up the jaw.
Contrary to what one might believe, the sharp beak is not used to attack the prey, but to stun it. This species could use it to ram a school of fish, and then consume those that are injured or disturbed. A defensive use has also been attributed to it, as protection against its natural predators.
Other relevant aspects are the presence of a large first dorsal fin and the absence of pelvic fins. In addition, it does not have teeth and its skin lacks scales. Their body is elongated and they measure approximately 4 meters. The fishing record for this species was caught in Chile in 1953. This specimen weighed 536.15 kilograms.
This species is ectothermic, so it does not have the ability to regulate its internal temperature. This is why it has special organs next to the eyes, which heat the brain and the eyeballs, thus improving their vision.
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Conservation
In some regions, such as the Mediterranean, the swordfish population is declining. However, this species is generally stable. This is why the IUCN has categorized the Xiphias gladius as of least concern about extinction.
However, the international protectionist organization indicates that, if actions are not taken that contribute to solving the problems that afflict it, it could be seriously threatened.
threats
Swordfish are threatened by hunting, whether accidentally, for sporting purposes or for food. It is a species sensitive to overfishing, since, among other things, the young are captured, preventing the species from recovering from overexploitation.
meat marketing
Regarding the use of its meat, it is highly valued in the market, for being compact and aromatic. In addition to this, it is highly nutritious, as it contains vitamins and minerals.
Among other of its benefits is its low caloric level, occupying the seventh position among the most nutritious fish, with only 110 kilocalories. Likewise, the liver of this fish is used in the pharmaceutical industry, due to the large amount of vitamin A it contains.
Harpoons, fishing nets, driftnets and longlines are used to capture it. The use of these constitutes a danger for sharks, birds and sea turtles. This is because they get caught in the nets and die.
Hunt
In general, the capture of this species is incidental, since it remains entangled in the lines of longline hooks, used in the tuna fishery.
Regarding recreational and sport fishing, these are practiced mainly off the coasts of Ecuador, California, Peru and northern Chile.
Characteristics
Physiology
Swordfish is an ectothermic animal, since it does not have the ability to constantly maintain its internal temperature. This will depend on the water conditions where you live. However, they have special organs on either side of their eyes, which help regulate temperature.
These heat the brain and the eyes, being able to raise their temperatures from 10°C to 15°C above that of the water where they live. The fact that the eyes stay warm helps improve their vision, thus making it easier for them to chase and catch their prey.
The fact that both organic structures can maintain their highest temperature on the outside allows swordfish to explore broader thermal niches. Likewise, it can hunt in deep and cold waters.
On the other hand, like the rest of the large pelagic animals, the anatomy of the Xiphias gladius It is specialized for fast swimming. However, this fish has a low percentage of white muscle, which allows it to make a sudden start. As an adult, it could swim at 25 meters per second.
Beak
The most relevant characteristic of the swordfish is the elongation of its upper jaw. Thus it is flattened, pointed and sharp, similar to a sword. Its size is almost a third of the total length of the animal.
Due to this particularity, this fish is known as the gladiator. However, its beak is not used as a spear to catch fish. Thus, it is not used to impale the prey, but to hurt or hit the large ones.
Also, it can ram schools of fish, stunning them for easy capture. Likewise, the researchers point out that swordfish possibly use their beaks as protection, against threats from their natural predators.
In this sense, there have been confrontations between this fish and the short-finned shark (Isurus oxyrinchus), where he is attacked in the stomach, causing his death.
Body
Its body is robust and has a cylindrical and elongated shape. The vertebral column is made up of 26 vertebrae, 15 precaudal and 11 caudal. Likewise, it is slightly flattened on the sides, deeper in the posterior part of the gill openings and thinner in the caudal part.
At birth, this species has its body covered in scales, however, they usually lose them progressively. Once he is an adult, he lacks these completely.
fins
This species has two dorsal fins that, in the juvenile stage, are arranged continuously. When it reaches adulthood, these structures are separated, the first being larger than the second. Thus, the first dorsal, which originates on the gill openings, has between 34 and 49 rays and the second dorsal, 4 to 6 rays.
In addition, the two anal fins that it possesses are distant from each other and one is larger than the other. The first anal fin has between 13 and 14 rays and the other has 3 or 4 rays. The second anal fin is positioned a little further forward than the second dorsal. The anus is located near the origin of these two fins.
As for the pectoral fins, they are somewhat rigid, long and narrow. They have between 16 and 18 rays and are located in the lower part of the body. The caudal fin is short but very wide and lunate in shape.
Likewise, it has a caudal peduncle, with a prominent keel on each side and a cut on the ventral and dorsal surface. On the other hand, this fish lacks ventral fins.
Color
The upper part of the body can vary between shades of blackish brown, purple, dark blue and even black. These dark colors fade until they reach the ventral area, which can be whitish, with flashes of silver. As for the fins, they can be brown or dark brown.
Head
Xiphias gladius it has a short head, with a pointed lower jaw. The mouth is wide and the eyes are blue.
Size
Swordfish can reach 4.45 meters in length and weigh up to 540 kilograms. Generally, females are larger than males, so fish that weigh more than 140 kilograms are probably female.
In the Mediterranean, an adult usually weighs 230 kilograms, while in the western Atlantic it weighs up to 320 kilograms and those in the southeastern Pacific weigh almost 536 kilograms.
taxonomy
Animal Kingdom.
Subkingdom Bilateria.
Phylum Cordate.
Vertebrate subphylum.
Superclass Actinopterygii.
Teleostei class.
Superorder Acanthopterygii.
Order Perciformes.
Suborder Xiphioidei.
Family Xiphiidae.
Genus Xiphias.
Species Xiphias gladius.
Habitat and distribution
Swordfish are distributed in the temperate, tropical, and sometimes cold waters of the Pacific, Atlantic, and Indian Oceans, between 60° North and 45° South latitudes. In addition, it lives in the Sea of Marmara, in the Mediterranean Sea, the Azov Sea and in the Black Sea.
Thus, it is found on both sides of the Atlantic Ocean, north of Norway, in some areas of the Gulf of St. Lawrence, on the south coast of Newfoundland and the Grand Banks.
It can also be found in the Mediterranean and the Red Sea; over the Cape of Good Hope. In relation to the Indian Ocean, it inhabits in a generalized way. In the eastern Pacific Ocean, it ranges from the Gulf of California and southern California to Chile, including offshore islands.
Swordfish are an oceanic animal, however they may occasionally be found in coastal waters. Thus, it can be located on the coasts located to the west of Mexico and the United States, because they are temperate and very deep.
Likewise, they are usually in the areas near the island of Hawaii, in Norway, Japan and east of South Africa.
Habitat
This species is epipelagic and mesopelagic, usually inhabiting surface waters, at temperatures above 13 °C. The optimum range for full development is between 18 and 22 °C.
Its distribution in the northwestern Pacific varies from the surface to 550 meters deep. However, it could drop occasionally to temperatures between 5 and 10°C and to a depth of 650 meters.
Although it prefers warm waters, it may migrate to cooler or warmer waters during the summer to feed, and return in winter to spawn.
Investigations carried out on populations living in the tropical Atlantic Ocean and the Mediterranean indicate that there is a genetic differentiation between them. Thus, the possibility of some genetic exchange between these two groups of swordfish could be considered.
Breathing
The breath in the Xiphias gladius it is gill. This fish takes dissolved oxygen in the water. At the level of the pharynx, swordfish have lateral openings, known as gill slits. In these develop the gills.
These structures have four gill arches, which are located dorsoventrally between the gill slits, on either side of the head. In each arch there are two rows of filaments, arranged in a V shape. Each of these has longitudinal folds, called lamellae.
It is in these lamellae where gas exchange occurs, since they are highly vascularized and made up of a thin wall of tissue. Thus, the oxygenated water that enters through the mouth flows through the gills from the oral cavity to the opercular cavity.
The blood flows through the gills in the opposite direction, in order to capture as much oxygen as possible. Consequently, the countercurrent respiratory exchange allows the release of carbon dioxide and oxygenation of the cells.
Characteristics of the gills
Gill design and characteristics are related to gill flow and high gas transfer rates. All this influences the maintenance of continuous and fast swimming.
The gill areas of the swordfish, although smaller than that of the tuna, are much larger than in the rest of the teleosts. This is related to its high energy demand, motivated by its migrations and the great depths in which it moves when swimming.
Regarding the morphometric characteristics, specialists have identified an increase in…