Oarfish

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Oarfish
Regalecus glesne
Regalecus glesne, King of herrings
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Lampridiformes
Family: Regalecidae
Genus and species

Regalecus glesne (Ascanius 1772)


With its extremely long and ribbon-like body, the oarfish (Regalecus glesne) is considered by some to be the most spectacular of all fish. Certainly it is the longest of all true bony fish (Osteichthyes). Whales are longer, but they are mammals; the whale shark may also be longer, but it is a shark and not a bony fish. Reports vary considerably, but lengths up to 6 meters have been documented, and longer lengths to 17 meters have been reported but unconfirmed.

The oarfish is as enigmatic as it is remarkable; it is the largest fish in the world, yet almost nothing is known of its biology, it occurs in all the world's oceans and seas, yet remains one of the most rarely seen of all fishes. Coupled with its snake-like appearance, the oarfish is sometimes mistaken for the fabled serpent, which it is not. On the other hand, the sight of an oarfish swimming on the surface is sure to draw cries of “sea serpent” and inevitably evoke attention.

Fish biologists maintain that the oarfish derives its popular name from flattened surfaces on its pelvic fins that were once thought used for oars. Popular suggestion is that oarfish were named for their long and laterally compressed body, which was thought to resemble an oar. The genus name, Regalecus, is from the Latin regalis and means “royal.” This may reference another common name accorded this species, “King of the Herrings,” possibly because its slim and silvery body resembles that of a greatly enlarged herring. The “royal” nature accorded the oarfish may also result from the crimson or brilliant red markings that adorn the fins of this fish.

Contents

Physical description/appearance

The oarfish body is ribbon-like or snake-like, elongate and tapering towards the tail. The snout is short and the eyes are smallish, although inevitably portrayed as large and glaring. A long dorsal fin supported by four hundred or more fin rays starts just above the eyes and runs nearly the length of the body. The 10-12 anterior rays of the dorsal fin are greatly elongated into a plume-like complex sometimes called a cockscomb. They, like the remainder of the dorsal fin are bright red in color. The paired pelvic fins consist of two rays, a smaller and splint-like ray and a long and thin and also reddish to scarlet in color. The distal ends are flattened and expanded like the blades of an oar, from which the oarfish may derive its name. The caudal fin is small and its rays terminate in thin spinules that project laterally. There is no anal fin.

Coloration is mostly bluish silver hue likened to a shimmering or polished silver coloration caused by small crystals of guanine deposited in the upper layers of the skin. Flanks and undersides may be variously speckled or marked with deeper blues and blacks.

Most measured specimens are in the 2-4 meter range, but specimens of 8 meters or more have been reported and there are reports of specimens many times larger. If the oarfish is, in fact, the source of the fabled sea serpent, then it is capable of considerably great lengths. Weight of average oarfish specimens is in the 100 kilogram range, with large specimens possibly reaching 300 kilograms.

The oarfish and its close relative, the streamer fish (Agrostichthys parkeri), both of which are members of the Regalecidea family, lack scales, anal fins, teeth, and swim bladder. The eyes are small, but the vertebrae are numerous, numbering to 170 in oarfish, along with the large number (to 412) fin rays. Both genera have 43 gill rakers and display the long, reddish anterior dorsal rays and long and slender pelvic fins composed of a single ray. All fins lack true spines.

Taxonomy and relationships

Taxonomically, the oarfish is one of the 55,000 species of vertebrates (Subphylum Vertebrata) and one of the 28,000 species of bony fish (Osteichthyes) that belong to the Class Actinopterygii (ray-finned fish), which constitutes the largest group of fish and also the largest class of vertebrates. Within this class, the oarfish are placed in the order Lampridiformes, which contains 41 recognized species of marine fish. The Lampridiformes is comprised of a number of morphologically spectacular marine forms such as the crestfishes, tapertails, ribbon fish, ink-eye, tubefish, and unicorn fish and, of course, the oarfish.

Both morphological and molecular evidence confirms that the order is a natural assemblage of fishes that diverged and evolved from a velifer ancestor sometime towards the end of the Mesozoic into the Eocene of the Cenozoic. Systematically, the group is of great interest because it represents the most primitive sister taxon to all higher groups of teloist fishes. From its origin to its subsequent evolution, the group underwent a distributional transition from shallow water and coastal forms to pelagic and mostly deep water fish, accompanied by a morphological transition from deep bodied fish to elongate forms exemplified most obviously by the icons of the group, the oarfish and its close relative, the ribbon fish.

Regardless of their diversity of shapes and sizes, the oarfish and its ordinal relatives share several characteristics in common. All have a large nasal cartilage that is inserted into a groove in the skull and partly supports the maxillae. This coupled with the lack of ligaments that connect the maxillary bones of the upper jaw to the cheekbones permit distension and protrusion of the jaws far forward and downward. This modification is important during feeding in which the enormous expansion of the mouth cavity enhances capture and swallowing of plankton, which forms the dietary staple of the oarfish and many of its kin.

The oarfish is placed in the family Regalecidea, which is one of six families in this order. It includes two monotypic genera, the oarfish and a single species of streamer fish (Agrostichthys parkeri). Currently, a single species of oarfish is recognized although some authorities suggest that several forms may represent valid species.

Life history and ecology

Distribution. Oarfish are cosmopolitan or nearly so and have been recorded in all of the world’s oceans and seas, excepting possibly the polar seas. Most recent sightings of oarfish are in shallow tropical and subtropical waters and may possibly represent diseased or disoriented individuals.

The oarfish is a solitary fish that is primarily an open ocean species, occurring in the epipelagic or upper ocean waters ranging from the surface or nearly so to depths of 1,000 meters or more, and possibly extending its activity into mesopelagic depths.

Movement and motion. Swimming oarfish have been photographed and their motion through the water documented. (See spectacular photography of swimming oarfish taken by U.S. Navy divers in the Bahamas at (http://www.nmfs.noaa.gov/species/fish_page/fish82a.html)

Oarfish swimming on or near the water surface move with an undulating motion reminiscent of a sea serpent with humps, showing against the natural waves and motion of the water. Forward movement is generated by rhythmical undulations that run the length of the dorsal fin, propel the creature forward. This locomotion pattern is called amiiform movement.

During feeding and possibly for some movements, the body orientation is vertical or nearly so with the head upwards and the long pelvic fins extended outwards, as opposed to nearly horizontal body posture as in other fish. It has been suggested that this posture illuminates prey against the lighter upper water.

Food and feeding. The oarfish is a planktonic feeder that consumes small fishes, crustaceans, and other plankton in the water column, which they strain from the water with their gill rakers. Some documented food groups include cnidarian medusa and hydroids, small squid, and fishes as well as planktonic krill. The stomach of a single oarfish about three meters in length contained about 10,000 euphausid krill.

Reproduction. The oarfish is a broadcast spawner, depositing unguarded buoyant eggs in the epipelagic or mesopelagic depths of the open ocean. The eggs so cast become part of the plankton and drift on or near the surface during a three week incubation. The eggs are large and cylindrical, averaging 2-6 millimeters in size and bright orange, pink, or red in chorion color, with several to numerous oil droplets. Eggs hatch in about three weeks and larvae resemble miniature adults with pigmented eyes, dorsal and pelvic fins, and rudimentary mouth and digestive tract. They become part of the plankton and drift just beneath the water surface, feeding almost immediately on smaller forms of plankton, which they encounter within the water column.

Courtship and mating has not been observed, but a dead female found stranded on the Floridian coast in March along with several male oarfish contained 140,000 eggs. Other reports suggest that the oarfish spawns in tropical and subtropical waters off Mexico from July to December.

Human interest and human use

Despite its rarity, the oarfish is not ICUN listed as an endangered species. Although of great curiosity to icthyologists, naturalists, cryptozoologists, and wildlife enthusiasts, the oarfish is not protected by any country at the present time.

Due to its rarity, the oarfish is neither commercially useful nor valued, although some consider it a game fish because of its great size. In any case, oarfish flesh is said to be gelatinous and unpalatable.

Recent sightings

For unknown reasons, a number of oarfish have beached themselves on shore, rather like the behavior of certain species of whales that run up on shore to beach themselves. On May 7, 1996, three observers watched an oarfish swimming on the surface waters in the eastern cove located on the west side of Isla San Francisco, located along the southern part of the Sea of Cortez. They reported that the large, eel-like creature with red tassles and a long red fin, later identified as an oarfish, swam on the surface in large circles. As the men waded ankle deep in the water, the creature suddenly swam rapidly towards them. They reacted by crushing the head with a rock.

Another sighting was from Coronado Island just off San Diego, where in 1996 a team in Navy SEAL school (Bud/S class 2008, basic underwater demolition) found during training exercises a dead, giant oarfish washed up on the beach, about a mile south of the base. It was 7.3 meters long and a third of a meter in width and weighed 136 kilograms.

For unknown reasons, many oarfish wash up along Australia’s long coastline. An article in the UnderwaterTimes.com shows three people holding an oarfish at least three meters in length, which they had found washed up at City Beach in Perth, Australia on June 29, 2004. The article noted that this was but one of at least six oarfish that had been reported along the western Australian coast in recent months.

A sea serpent connection?

Tales of marine sea serpents come from all parts of the globe, in all oceans and seas. Sea serpents were well known to ancient mariners who feared such beasts, although there is no record of sea serpents ever doing any harm. Despite frequent sightings that occurred over many centuries, neither identification nor biology of the legendary sea serpent was ever resolved.

Perhaps tales of the fabled sea serpent can finally be laid to rest at the oarfish door. The small, horse-like head, large eyes, serpent-like body, and undulating motion of an oarfish swimming on the surface must surely account for some of the many sea serpent tales. Of equal interest is the fact that to some observers the oarfish body form and bright red dorsal fin rays suggest a fearsome sea dragon instead. The oarfish connection to the fabled sea serpent remains plausible but unconfirmed.

References

  • Bauchot, M. L. 1995. Regalecidae. Reyes de arenque. In W. Fischer, F. Krupp, W. Schneider, C. Sommer, K. E. Carpenter, and V. Niem, (eds.), Guia FAO para Identification de Especies para lo fines de la Pesca. Pacifico Centro-Oriental. 3 volumes. Rome: FAO. p. 1418.
  • May, J. L., and J. G. H. Maxwell. 1986. Trawl Fish from Temperate Waters of Australia. CSIRO Division of Fisheries Research.
  • Moyle, P. B., and J. J. Cech, Jr. Fishes. An introduction to Icthyology. Upper Saddle River, NJ: Prentice-Hall, Inc.
  • Trunov, I. A. 1982. Species of the family Regalecidae (Lampridiformes) from the southeastern Atlantic Ocean. J. Icthyology 22: 1-6.

Links

Australian Oarfish Page. (http://www.amonoline.net.au/fishes/fishfacts/fish/rglene.htm)


Credits

This article began as an original work prepared for New World Encyclopedia by Dr. Dwight Smith and is provided to the public according to the terms of the New World Encyclopedia:Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Any changes made to the original text since then create a derivative work which is also CC-by-sa licensed. To cite this article click here for a list of acceptable citing formats.

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