Brown ragfish and fantail ragfish
Brown ragfish and fantail ragfish are two species of fish belonging to the family Icosteidae, found in the cold waters of the northern Pacific Ocean, ranging from southern California to Alaska and extending westward to Japan. These unique fish are notable for their flexible cartilage skeletons, which give them a soft, ragged appearance reminiscent of a bundle of rags. The brown ragfish can grow significantly larger, reaching lengths of up to seven feet and weighing close to 340 pounds, while the smaller fantail ragfish measures about one and a half feet long. Both species possess dorsal, pectoral, anal, and caudal fins but lack pelvic fins in adulthood.
Their diet primarily consists of fish and squid, and they are believed to be preyed upon by larger predators, including sperm whales. The mating season for ragfish is thought to occur year-round, with females capable of laying up to 430,000 eggs in a single spawning event. While the lifespan of ragfish is estimated at around eight years, their conservation status remains unknown. Overall, these enigmatic fish continue to intrigue researchers due to their unique biology and limited understanding.
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Brown ragfish and fantail ragfish
Ragfish receive their name because it has been said they look like a bundle of rags dropped on the floor. Very little is known about these fish which have skeletons of flexible cartilage and very few bones.
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Icosteidae
Genus: Icosteus
Species: Aenigmaticus
The cold waters of the northern Pacific Ocean are home to the two species of ragfish. These fish may be found in waters between southern California and Alaska and westward to Japan at depths of 270 to 1,200 feet (eighty to 365 meters). Both species survive on a diet of fish and squid. In turn, it is believed that sperm whales may eat brown ragfish, since brown ragfish remains have been found inside sperm whales. The exact position in the ocean's food chain of the fantail ragfish is not known, but it is likely eaten by other larger predatory creatures.
The appearance of both species has been described as a bundle of rags dropped on the floor. These soft-bodied fish have very few bones in their bodies and have skeletons mostly of cartilage. This feature is the origin of the ragfish's name. Cartilage is flexible tissue which is softer than bones but still firmer than skin or other similar tissue. People have cartilage in their ears, noses, and within other parts of their bodies, such as around joints.
The bodies of ragfish are flattened from side-to-side so that they look thin when viewed from the front or back. The adult fantail ragfish has a deep body when measured from its back down its side to its belly. It does not have scales but does have small spines on its back and in its fins. A full-grown fantail ragfish measures around one and a half feet (forty-five centimeters) long. The brown ragfish is much larger and may reach a length of seven feet (two meters) and a weight close to 340 pounds (155 kilograms). Its body is more elliptical, or oval-shaped. Like the fantail ragfish, it does not have scales, but it also lacks spines. Both species have dorsal (back), pectoral (side), anal (rear), and caudal (tail) fins, but they lose their pelvic (belly) fins when they become adults. The snouts of both fantail and brown ragfish are blunt. As juveniles, ragfish have brown or yellow skin, and they become dark brown as adults.
The ragfish's mating season is thought to be year-round. Ragfish are oviparous. A single female ragfish can lay up to 430,000 free-floating eggs in a single mating season. After the female has released her eggs, the male swims over them and fertilizes them. This process is called spawning.
The lifespan of ragfish about eight years. Their conservation status is unknown.
Bibliography
“Icosteus Aenigmaticus.” FishBase, fishbase.mnhn.fr/summary/3929. Accessed 9 Apr. 2024.
Myers, P., et al. “Icosteus Aenigmaticus.” Animal Diversity Web, 2024, animaldiversity.org/accounts/Icosteus‗aenigmaticus/classification/. Accessed 9 Apr. 2024.
NOAA. “Perciformes Icosteidae.” National Ocean Service Website, Jun. 2021, apps-afsc.fisheries.noaa.gov/ichthyo/LHDataLH.php?GSID=Icosteus!aenigmaticus. Accessed 9 Apr. 2024.