While spawning, a single female may release several million eggs, increasing the likelihood that some will be fertilized and that at least one hatched larva will grow to reach adulthood.
Though almost all fishes are cold blooded, swordfish have a specialized blood vessel structure — called a countercurrent exchanger — that allows them to warm their brains and eyes. This adaptation provides them with a major advantage when hunting in cold, deep water, by allowing them to think more quickly and see more clearly. The swordfish is a highly prized food fish and is fished heavily throughout its range. Generally, scientists believe that these fisheries are managed fairly well, and the species is not considered overfished.
However, there are some populations that are fished more heavily than others, and populations seem to be decreasing in many places around the world. It is, therefore, important to continue to monitor fishing activities in order to ensure that humans do not threaten this iconic, powerful species. As the swordfish is at the top of the open ocean food web, the muscle tissue can accumulate dangerously high amounts of mercury and other toxins, so it is important to limit the amount that you eat to no more than one serving per week.
Click here or below to download hands-on marine science activities for kids. It was like a death of a thousand cuts. Fishers no longer were making very much money because they were forced to operate in a small window. Chugey Sepulveda. It all just sort of faded away.
Yet there is still a big appetite for swordfish: Americans eat almost 20 million pounds of swordfish a year. But for The Nature Conservancy and its partners, it seemed as if there might be a way to solve many problems at once. To find a better way, a slew of scientists and fishers would need to study the behavior of swordfish and develop and test a new type of fishing gear. If they succeeded, they could make California-caught swordfish both sustainable and profitable.
And even more important, they could export this system to countries where swordfishing has a disproportionate impact on other marine life caught up in drift nets. Illustrated below--numbers correspond to numbers on the illustration. A flag acts like a bobber, visually indicating when a fish has been caught. This is where swordfish are likely to be caught during the day, and where the baits will attract fewer other fish or marine mammals.
The main line is outfitted with a weight to keep it steady in the ocean currents and reduce entanglement with other animals. It also has a small strobe light, believed to either attract swordfish or mimic the bioluminescence of squid. Baited hooks are attached to the main line. In California, harpooning was the sole technique for catching swordfish until the late s. By the early s, many fishers had abandoned the labor-intensive, low-yield practice of harpooning and begun using drift gillnets—mile-long nets that hang as deep as feet and are left to float in the water overnight.
Sperm whales, classified as endangered under the Endangered Species Act, can be as much as 60 feet long, weigh 60 tons and dive to over 10, feet. Humpback whales eat up to a ton of krill and small fish per day, and migrate up to 5, miles. The population that breeds in Mexico but feeds in the Pacific from California to Alaska is listed as threatened under the Endangered Species Act.
Pacific leatherback sea turtles—the largest turtles in the world—can migrate some 7, miles each year from Indonesia, Papua New Guinea and the Solomon Islands to their foraging grounds on the U.
West Coast and back. Its distinctive blunt head is often scarred by the beaks and tentacles of its prey. West Coast. Regulators began closing off more and more of the ocean to protect turtles and marine mammals. In , for instance, the federal government prohibited drift gillnet fishing in , square miles of ocean off the California coast for three months each year to protect Pacific leatherback turtles, which are classified as endangered under the U.
Endangered Species Act and whose Pacific populations have precipitously declined over recent decades. Larval swordfish feed on zooplankton including other fish larvae.
Juveniles eat squid, fishes, and pelagic crustaceans. Reproduction Swordfish have been observed spawning in the Atlantic Ocean, in water less than ft. 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. 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 elongate, 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 cm , only the large lobe remains of the first dorsal fin.
Predators Predators of adult swordfish include marine mammals such as killer whales. Young adults and juveniles are eaten by a variety of sharks and other large predatory fish including blue marlin Makaira nigricans , black marlin Makaira indica , sailfish Istiophorus platypterus , yellowfin tuna Thunnus albacares , and the dolphinfish Coryphaena hippurus.
Parasites Swordfish are hosts to 49 species of parasites including cestodes tapeworms in the stomach and intestines, nematodes roundworms in the stomach, tremodes flukes on the gills, and copepods attached to the surface of the body. One such copepod is the Pennella filosa , a parasite that inserts itself into the flesh of the swordfish. Sea lampreys are also ectoparasites on swordfish. They leave behind longitudinal scratch marks indicating that swordfish are skilled at ridding themselves of the lamprey.
Other parasites include digenea flukes , didymozoidea tissue flukes , monogenea gillworms , cestoda tapeworms , nematoda roundworms , acanthocephala spiny-headed worms , copepods, barnacles, and isopods. Ectoparasitic fish include the cookiecutter shark Isistius brasiliensis , pilotfish Naucrates ductor , sea lamprey Petromyzon marinus , spearfish remora Remora brachyptera , and marlin sucker Remora osteochir.
Linnaeus first described the swordfish in , providing the name still in use today, Xiphias gladius. Other scientific names that have been used to refer to the swordfish include Xiphias imperator Bloch and Schneider , Xiphias rondeletti Leach , Phaethonichthys tuberculatus Nichols , Xiphias estara Phillips, , Tetrapterus imperator Rohl , and Xiphias thermaicus Serbetis Discover Fishes Xiphias gladius.
Swordfish Swordfish. Photo courtesy Virginia Institute of Marine Science Xiphias gladius This migratory billfish can grow to inches long, from the tip of its slender bill to the end of its crescent caudal tail fin. Order — Perciformes Family — Xiphiidae Genus — Xiphias Species — gladius Common Names English language common names include swordfish, broadbill, broadbill swordfish, and sword fish.
Importance to Humans Historic swordfish catch.
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