Swordfish
Essay Preview: Swordfish
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Tina Valler
Period 5/6
The swordfish was first described in 1758 by Linnaeus. It was given the name Xiphias gladius which is still used in present day. The Family of this fish is Xiphiidae, Order is Perciformes, and the Class is Actinopterygii. When it is translated into English, the Latin term gladius means “sword”, referring to the long sword-like bill the fish possesses. Some of the English common names include broadbill, broadbill swordfish, and many others. The swordfish is named for its sharp, broad, elongated upper jaw, which it uses to flail and pierce its prey of smaller fish, rising beneath a school to kill and then devour them.
This fish is unlike any other species in the ocean and doesnt resemble any other billfish. The color varies from black to grayish blue, brown, metallic purple, or bronze. The sides are dusky, and it is long and flat. This fish lacks scales, teeth, and pelvic fins. It has single keel on each side of the body in front of the tail. The first dorsal fin is high and the fish possesses very large eyes.
The swordfish is found specific yet diverse areas including tropical, temperate, and in some cases cold waters, with a latitudinal range of approximately 60oN to 45oS. This fish migrates frequently, often moving to warmer waters in the winter and cooler waters in the summer. It is present in frontal zones, areas where ocean currents collide and the productivity is high. This fish can be found worldwide, it can vary from oceans like the Atlantic, Pacific, and Indian Oceans. Studies have shown a few swordfish make substantial seasonal migration. In the Pacific, swordfish appear to move northward from Baja California in the spring to California in the summer and fall, then move off-shore to spawn. Swordfish in the eastern Pacific generally stay inshore near the bottom during the day. At dusk, they head seaward. After sunset, they feed near the surface and return to inshore areas at sunrise.
Swordfish are a commercially important species, for which harvesting greatly depends on the size structure of the population. Swordfish reach a maximum size of 177 inches total length and a maximum weight of 1,400 lbs. Surprisingly, females are larger than males of the same age, and mostly all swordfish over 300 pounds are female. They also seem to grow faster and are proportionally heavier at the same length .Pacific swordfish grow to be the largest, while western Atlantic adults grow to be an astounding 700 pounds, and Mediterranean adults are rarely over 500 pounds.. Swordfish reach sexual maturity between the ages of five and six and have a total lifespan of only nine years. One year old swordfish are about 51-61 cm long . Fish caught on the commercial fisheries are predominately 4-5 years old. Maximum age is thought to be 9 years. There is some evidence swordfish in the Pacific may have a slower growth rate and smaller maximum size than fish in the Atlantic.
Adult swordfish are opportunistic feeders on squid, pelagic and crustaceans. They may utilize their bill to kill their prey – rising from beneath a school of fish, swinging the sword from side to side, then consuming the fish that were killed. Larvae swordfish feed primarily on fish larvae and zooplankton. Juveniles feed on squid and small fishes. Swordfish larvae, and presumably juveniles, are a common food of other fishes, including larger swordfish. Adult swordfish have few natural enemies, some known predators include sperm and killer whales and large sharks. According to their stomach contents, swordfish feed at the surface as well as the bottom of their depth range.
Swordfish have been observed spawning in the Atlantic Ocean in waters that are less than 250 feet deep. Females may carry as many as one million to twenty-nine million eggs in their gonads. During spawning season, solitary males and females pair up with each other. Spawning occurs in the Gulf of Mexico, the Florida coast,