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Oarfish

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Oarfish
King of herrings
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Actinopterygii
Order:
Lampriformes
Family:
Regalecidae
Genera

Agrostichthys
Regalecus

Oarfish are large, greatly elongated, pelagic Lampriform fishes comprising the small family Regalecidae.[1] Found in all temperate to tropical oceans yet rarely seen, the oarfish family contains four species in two genera. One of these, the king of herrings (Regalecus glesne), is listed in the Guinness Book of World Records as the longest bony fish alive, at up to 17 metres (56 ft) in length.[2][3]

The common name oarfish is presumably in reference to either their highly compressed and elongated bodies, or to the former (but now discredited) belief that the fish "row" themselves through the water with their pelvic fins.[4] 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 (to a minor extent) fished commercially, oarfish are rarely caught alive; their flesh is not well regarded due to its gelatinous consistency.

Anatomy and morphology

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

The tapering, ribbony silver bodies of oarfish—together with an impressive, pinkish to cardinal red dorsal fin—help explain the perception of majesty taken from rare encounters. The dorsal fin originates from above the (relatively small) eyes and runs the entire length of the fish. Of the approximately 400 dorsal fin rays, the first 10 to 12 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 1 to 5 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, describes the oarfish as giving off "electric shocks" when touched.[4]

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 covered with easily abraded, silvery guanine. 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. The king of herrings is by far the largest member of the family at a published total length of 11 metres (with unconfirmed reports of 15 metres or more) and 272 kilogrammes in weight. The streamer fish is known to reach 3 metres total length whilst the largest recorded specimen of Regalecus russelii measured just 540 centimetres standard length. It is probable that this little-known species can regularly reach a maximum length of at least 15.2 metres (50 ft).[citation needed]

Distribution

The members of the family are known to have a worldwide range. However, specific encounters with live individuals in situ are rare and distribution information is collated from records of oarfishes caught or washed ashore.[4]

Ecology and life history

Rare encounters with divers and accidental catches have supplied what little is known of oarfish behaviour and ecology. Apparently solitary animals, oarfish may frequent significant depths up to 1,000 metres (3,300 ft). A photograph on display in bars, restaurants, guesthouses and markets around Laos and Thailand that is captioned, "Queen of Nāgas seized by American Army at Mekhong River, Laos Military Base on June 27, 1973 with the length of 7.80 metres," is a hoax. The photograph was taken by Dr. Leo Smith of an oarfish found in late 1996 by US Navy SEAL trainees on the coast of Coronado, California, USA.[5][6]

An oarfish measuring 3.3 metres (11 ft 4 in) and 63.5kg (140 lb) was reported to have been caught on 17 February 2003 by Ms Val Fletcher using a fishing rod baited with squid, at Skinningrove, United Kingdom.[7]

Behaviour

In 2001 an oarfish was filmed alive and in situ: the 1.5 metre fish was spotted by a group of U.S. Navy personnel during the inspection of a buoy in the Bahamas [1]. The oarfish was observed to propel itself via an amiiform mode of swimming; that is, rhythmically undulating the dorsal fin whilst 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 off 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 5 m and 10 m in length.[8]

From December 2009 to March 2010, unusual numbers of the slender oarfish Regalecus russelii[9] (竜宮の使い “Ryūgū-No-Tsukai”,) known in Japanese folklore as the Messenger from the Sea God's Palace, have appeared in the waters and on the beaches of Japan; the appearance of which is said to portend earthquakes.[10]

Feeding ecology

Oarfish feed primarily on zooplankton, selectively straining tiny euphausiids, shrimp and other crustaceans from the water. Small fish, jellyfish and squid are also taken. Large open-ocean carnivores are all likely predators of oarfish, and include the Oceanic whitetip shark. Oarfish have no visible teeth.

Life history

The oceanodromous Regalecus glesne is recorded as spawning off Mexico from July to December; all species are presumed to be non-guarders and release brightly coloured, buoyant eggs, up to 6 millimetres (0.24 in) across, which are incorporated into the zooplankton. 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.[4] 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.

Etymology and taxonomic history

Juvenile Regalecus glesne

The oarfish family contains four species in two genera.

See also

Bibliography

  • Froese, Rainer; Pauly, Daniel (eds.). "Family Regalecidae". 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

References

  1. ^ Froese, Rainer; Pauly, Daniel (eds.). "Family Regalecidae". FishBase. March 2007 version.
  2. ^ Bourton, Jody. Giant bizarre deep sea fish filmed in Gulf of Mexico. BBC Earth News
  3. ^ Oarfish Information Page
  4. ^ a b c d Olney, John E. (1998). Paxton, J.R. & Eschmeyer, W.N. (ed.). Encyclopedia of Fishes. San Diego: Academic Press. pp. 157–159. ISBN 0-12-547665-5.{{cite book}}: CS1 maint: multiple names: editors list (link)
  5. ^ 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. {{cite web}}: Check date values in: |year= (help)CS1 maint: year (link)
  6. ^ "SEALs and a serpent of the sea" (PDF). ALL HANDS. Naval Media Center. 1997. pp. 20–21. 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. {{cite web}}: |first= missing |last= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  7. ^ 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.
  8. ^ Bourton, Jody (2010-02-08). "http://news.bbc.co.uk/earth/hi/earth_news/newsid_8501000/8501251.stm". BBC. Retrieved 2010-02-09. {{cite news}}: Cite has empty unknown parameter: |coauthors= (help); External link in |title= (help)
  9. ^ "Regalecus russelii (Cuvier, 1816) species summary". FishBase Consortium. Retrieved 23 Mar 2010.
  10. ^ Daiki Yamamoto (04 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. {{cite web}}: Check date values in: |date= (help)
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