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Giant oarfish
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Lampriformes
Family: Regalecidae
United States Navy SEALS holding a 23-foot (7.0 m) giant oarfish, found washed up on the shore near San Diego, California, in September 1996

Oarfish are large, greatly elongated, pelagic lampriform fish belonging to the small family Regalecidae.[1] Found in all temperate to tropical oceans yet rarely seen, the oarfish family contains three species in two genera. One of these, the giant oarfish (Regalecus glesne), is the longest bony fish alive, growing up to 8 m (26 ft) in length.

The common name oarfish is thought to be in reference either to their highly compressed and elongated bodies, or to the now discredited belief that the fish "row" themselves through the water with their pelvic fins.[2] The family name Regalecidae is derived from the Latin regalis, meaning "royal". The occasional beachings of oarfish after storms, and their habit of lingering at the surface when sick or dying, make oarfish a probable source of many sea serpent tales.

Although the larger species are considered game fish and are fished commercially to a minor extent, oarfish are rarely caught alive; their flesh is not well regarded for eating due to its gelatinous consistency.[3]

Anatomy and morphology[edit]

The dorsal fin originates from above the (relatively large) eyes and runs the entire length of the fish. Of the approximately 400 dorsal fin rays, the first 10 to 13 are elongated to varying degrees, forming a trailing crest embellished with reddish spots and flaps of skin at the ray tips. The pelvic fins are similarly elongated and adorned, reduced to one to five rays each. The pectoral fins are greatly reduced and situated low on the body. The anal fin is completely absent and the caudal fin may be reduced or absent, as well, with the body tapering to a fine point. All fins lack true spines. At least one account, from researchers in New Zealand, described the oarfish as giving off "electric shocks" when touched.[2]

Like other members of its order, the oarfish has a small yet highly protrusible oblique mouth with no visible teeth. The body is scaleless and the skin is covered with easily abraded, silvery ganoine. In the streamer fish (Agrostichthys parkeri), the skin is clad with hard tubercles. All species lack gas bladders and the number of gill rakers is variable.

Oarfish coloration is also variable; the flanks are commonly covered with irregular bluish to blackish streaks, black dots, and squiggles. These markings quickly fade following death. It is probable that these markings are bioluminescent in the deep sea.

Oarfish that washed ashore on a Bermuda beach in 1860: The fish was 16 ft (4.9 m) long and was originally described as a sea serpent.

The giant oarfish is by far the largest member of the family at a published total length of 8 m (26 ft)—with unconfirmed reports of 11 m (36 ft) and 17 m (56 ft)[4][5][6] specimens—and 270 kg (600 lb) in weight.[7] The streamer fish is known to reach 3 m (10 ft) in length,[8] while the largest recorded specimen of Regalecus russelii measured 5.4 m (18 ft).[9]

Oarfish are the longest known living species of bony fish.[10]

In some oarfishes found, end of tails may appear stump-like; this is likely the consequence of self-amputation that is thought to be a defense mechanism against predators.[11]


The oarfish is thought to inhabit the epipelagic to mesopelagic ocean layers, ranging from 200 meters (660 ft) to 1,000 meters (3,300 ft) and is rarely seen on the surface. A few have been found still barely alive, but usually if one floats to the surface, it dies. At the depths the oarfish live, there are few or no currents. As a result, they build little muscle mass and they cannot survive in shallower turbulent water.[12]


The members of the family are known to have a worldwide range. They have wide, tropical, subtropical, and warm temperate distributions.[13] However, human encounters with live oarfish are rare, and distribution information is collated from records of oarfish caught or washed ashore.[2]

Ecology and life history[edit]

Oarfish were first described in 1772.[14] Rare encounters with divers and accidental catches have supplied what little is known of oarfish ethology (behavior) and ecology. Oarfish are solitary animals and may frequent significant depths up to 1,000 m (3,300 ft).

An oarfish measuring 3.3 m (11 ft) and 63.5 kg (140 lb) was reported to have been caught in February 2003 using a fishing rod baited with squid at Skinningrove, United Kingdom.[15]

A photograph on display in bars, restaurants, guesthouses and markets around Laos and Thailand captioned "Queen of Nāgas seized by the American Army at Mekhong River, Laos Military Base, on June 27, 1973, with the length of 7.80 metres [25.6 ft]" is, as far as the caption goes, a hoax. The photograph itself is real, however, and was taken by Dr. Leo Smith of the Field Museum, of an oarfish found in September 1996 by United States Navy SEAL trainees on the coast of Coronado, California, USA.[16][17]


In 2001, an oarfish was filmed alive in situ: the 1.5-metre (4.9-foot) fish was spotted by a group of U.S. Navy personnel during the inspection of a buoy in the Bahamas.[18] The oarfish was observed to propel itself by an amiiform mode of swimming; that is, rhythmically undulating the dorsal fin while keeping the body itself straight. Perhaps indicating a feeding posture, oarfish have been observed swimming in a vertical orientation, with their long axis perpendicular to the ocean surface. In this posture, the downstreaming light would silhouette the oarfishes' prey, making them easier to spot.

In July 2008, scientists captured footage of the rare fish swimming in its natural habitat in the mesopelagic zone in the Gulf of Mexico. It is the first ever confirmed sighting of an oarfish at depth, as most specimens are discovered dying at the sea surface or washed ashore. The fish was estimated to be between five and ten metres (16 and 33 ft) in length.[19]

As part of the SERPENT Project, five observations of apparently healthy oarfish Regalecus glesne by remotely operated vehicles were reported from the northern Gulf of Mexico between 2008 and 2011 at depths within the epipelagic and mesopelagic zones.[20] These observations include the deepest verified record of R. glesne (463–492 m or 1,519–1,614 ft).[21] In the 2011 sighting, an oarfish has been observed to switch from swimming with a vertical posture to swimming laterally, using lateral undulations of its entire body.[22] Oarfish were found to have late or slow flight responses towards approaching remotely operated vehicles, supporting the hypothesis that oarfish have few natural predators.[22]

From December 2009 to March 2010, unusual numbers of the slender oarfish Regalecus russelii[9] (宮の使い “Ryūgū-No-Tsukai”,) known in Japanese folklore as the Messenger from the Sea God's Palace, appeared in the waters and on the beaches of Japan, the appearance of which is said to portend earthquakes.[23] After the 2011 Fukushima earthquake and tsunami which killed over 20,000 people, many pointed to the oarfish from 2009–⁠2010 to build up this myth.[24]

In 2016, Animal Planet aired an episode of the television series River Monsters named "Deep Sea Demon" in which Jeremy Wade was filmed during an encounter with a live oarfish while diving. The oarfish at this location seemed to be using a buoy anchor chain as a guide to ascend to the surface. On his second diving attempt, he was able to film two live oarfish as they ascended relatively close to the surface. This is the only known footage of human interaction with a healthy oarfish in its own environment. Wade was even able to touch one of the oarfish with his hand. The oarfish were propelling themselves by an amiiform mode of swimming as noted by other sightings.[25]

In January 2019 two oarfish were found alive in the nets of fisherman on the Japanese island of Okinawa.[24]

Feeding ecology[edit]

Oarfish feed primarily on zooplankton, selectively straining tiny euphausiids, shrimp, and other crustaceans from the water. Small fish, jellyfish, and squid are also taken.[26] Large open-ocean carnivores are all likely predators of oarfish.

Life history[edit]

The oceanodromous Regalecus glesne is recorded as spawning off Mexico from July to December; all species are presumed to not guard their eggs, and release brightly coloured, buoyant eggs, up to six millimetres (0.24 in) across, which are incorporated into the zooplankton.[2] Based on their reproductive morphology, oarfish are thought to batch spawn. Within each breeding season that may last one or two months, individuals spawn once or multiple times in discrete spawning events before their gonads enter a long, regressive stage of reproductive development.[27]

The eggs hatch after about three weeks into highly active larvae that feed on other zooplankton. The larvae have little resemblance to the adults, with long dorsal and pelvic fins and extensible mouths.[2] Larvae and juveniles have been observed drifting just below the surface. In contrast, adult oarfish are rarely seen at the surface when not sick or injured. It is probable that the fishes go deeper as they mature.

From January to February, 2019, researchers tested and recorded the first successful instance of artificial insemination and hatching of the oarfish (Regalecus russellii) using gonads from two washed-up specimens. Compared to adults, the body structure of newly hatched oarfish larvae look more compressed. The larvae often swam using mainly their pectoral fins, facing downward, with their mouths constantly open. They did not eat, so they had died four days after they hatched.[28]

See also[edit]


  • Froese, Rainer, and Daniel Pauly, eds. (2005). "Regalecidae" in FishBase. February 2005 version.
  • Pete Thomas, Blue Demons, The Los Angeles Times, August 26, 2006.
  • Fishes: An Introduction to ichthyology. Peter B. Moyle and Joseph J. Cech, Jr; p. 338. Printed in 2004. Prentice-Hall, Inc.; Upper Saddle River, New Jersey. ISBN 0-13-100847-1


  1. ^ Froese, Rainer, and Daniel Pauly, eds. (2007). "Regalecidae" in FishBase. March 2007 version.
  2. ^ a b c d e Olney, John E. (1998). Paxton, J.R.; Eschmeyer, W.N. (eds.). Encyclopedia of Fishes. San Diego: Academic Press. pp. 157–159. ISBN 978-0-12-547665-2.
  3. ^ Davis, Josh L. Rare "Sea Monster" Washes Ashore In New Zealand. IFLScience
  4. ^ McClain, Craig R.; Balk, Meghan A.; Benfield, Mark C.; Branch, Trevor A.; Chen, Catherine; Cosgrove, James; Dove, Alistair D.M.; Gaskins, Leo C.; Helm, Rebecca R. (2015-01-13). "Sizing ocean giants: patterns of intraspecific size variation in marine megafauna". PeerJ. 3: e715. doi:10.7717/peerj.715. ISSN 2167-8359. PMC 4304853. PMID 25649000.
  5. ^ Bourton, Jody. Giant bizarre deep sea fish filmed in Gulf of Mexico. BBC Earth News
  6. ^ Douglas Quenqua. Oarfish Offer Chance to Study an Elusive Animal Long Thought a Monster. New York Times. 2 November 2013
  7. ^ Burton, Maurice; Burton, Robert (2002). International Wildlife Encyclopedia (3rd ed.). New York: Marshall Cavendish. pp. 1767–1768. ISBN 978-0-7614-7279-7.
  8. ^ "Agrostichthys parkeri (Benham, 1904) Streamer fish". FishBase Consortium. Retrieved 2013-11-03.
  9. ^ a b "Regalecus russelii (Cuvier, 1816) species summary". FishBase Consortium. Retrieved 2013-11-03.
  10. ^ "5 Surprising Facts About the Oarfish That Has Been Washing Up on Beaches". 2013-10-22. Retrieved 2015-06-06.
  11. ^ "Regalecus russelii, Oarfifsh". www.fishbase.us. Retrieved 2020-10-30.
  12. ^ Powell, Daniel. "First-ever oarfish caught on rod and reel". San Diego Reader News. Retrieved 2015-06-30.
  13. ^ Roberts, T., R. (2012). Systematics, biology, and distribution of the species of the oceanic oarfish genus Regalecus (Teleostei, Lampridiformes, Regalecidae). Paris: French National Museum of Natural History. pp. 202, 1–266. ISBN 978-1247669526.
  14. ^ "National Geographic". 2013-10-22. Retrieved 30 April 2018.
  15. ^ Jenkins, Russell (21 February 2003). "Woman angler lands legendary sea monster". The Times, London. Retrieved 25 February 2010. The novice angler fishing off the rocks for mackerel thought that she must have hooked a big one. – Unfortunately the oarfish has been cut up into steaks for the pot.
  16. ^ Ranges, Trevor (2002–2006). "A Big Fish Tale". thailandroad.com. p. 2. We were on our morning physical fitness run when we came across this huge fish lying on the sand.
  17. ^ JOSN Jojm (April 1997). "SEALs and a serpent of the sea" (PDF). ALL HANDS. photos by LT DeeDee Van Wormer. Naval Media Center. pp. 20–21. Archived from the original (PDF) on 2006-04-16. The silvery serpent of the sea – an oarfish – was discovered last year by Basic Underwater Demolition/SEAL (BUD/S) Instructor Signalman 2nd Class (SEAL) Kevin Blake.
  18. ^ "Sustainability species Identification; Oarfish (Regalecus glesne Ascanius)". NOAA Fisheries service. Retrieved 28 September 2012.
  19. ^ Bourton, Jody (2010-02-08). "Giant bizarre deep sea fish filmed in Gulf of Mexico". BBC. Retrieved 2010-02-09.
  20. ^ "SERPENT Project | SERPENT Project".
  21. ^ Benfield, M.C. (5 June 2013). "Five in situ observations of live oarfish Regalecus glesne (Regalecidae) by remotely operated vehicles in the oceanic waters of the northern Gulf of Mexico". Journal of Fish Biology. 83 (1): 28–38. doi:10.1111/jfb.12144. PMID 23808690.
  22. ^ a b Benfield, M. C.; Cook, S.; Sharuga, S.; Valentine, M. M. (July 2013). "Five in situ observations of live oarfish Regalecus glesne (Regalecidae) by remotely operated vehicles in the oceanic waters of the northern Gulf of Mexico: in situ observations of regalecus glesne". Journal of Fish Biology. 83 (1): 28–38. doi:10.1111/jfb.12144. PMID 23808690.
  23. ^ Yamamoto, Daiki (4 Mar 2010). "Sea serpents' arrival puzzling, or portentous?". Kyodo News. Retrieved 6 Mar 2010. TOYAMA — A rarely seen deep-sea fish regarded as something of a mystery has been giving marine experts food for thought recently after showing up in large numbers along the Sea of Japan coast.
  24. ^ a b Alex Stambaugh and Junko Ogura. "Pair of rare oarfish discovered alive in Japan". CNN. Retrieved 2019-02-24.
  25. ^ http://animals.barcroft.tv/sea-serpent-river-monsters-jeremy-wade-rare-oar-fish
  26. ^ Roberts, Tyson R. (November 2017). "Anatomy and physiology of the digestive system of the oarfish Regalecus russellii (Lampridiformes: Regalecidae)". Ichthyological Research. 64 (4): 475–477. doi:10.1007/s10228-017-0574-7. ISSN 1341-8998. S2CID 207064546.
  27. ^ Forsgren, Kristy L.; Jamal, Homam; Barrios, Andrew; Paig‐Tran, E. W. Misty (2017). "Reproductive Morphology of Oarfish (Regalecus russellii)". The Anatomical Record. 300 (9): 1695–1704. doi:10.1002/ar.23605. ISSN 1932-8494. PMID 28390152.
  28. ^ Oka, Shin-ichiro; Nakamura, Masaru; Nozu, Ryo; Miyamoto, Kei (2020). "First observation of larval oarfish, Regalecus russelii, from fertilized eggs through hatching, following artificial insemination in captivity". Zoological Letters. 6 (1): 4. doi:10.1186/s40851-020-00156-6. ISSN 2056-306X. PMC 7140580. PMID 32292594.

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