Oarfish, Regalecus russelii

Oarfish, Regalecus russelii. Fish photographed in the surf of Isla Colorado, Baja California Sur, February 2025. Photograph courtesy of Captain Servando Davis, Loreto.

Oarfish, Regalecus russelii. Photographs courtesy of Chris Wheaton, Fullerton, California.

Oarfish, Regalecus russelii. Fish collect from coastal water off Coronado Island, San Diego, California, September 1996. Length: 7.0 m (23 feet). Weight: 140 kg (300 pounds).

The Oarfish, Regalecus russelii, is a member of the Regalecidae Family of Oarfish. There are two global members of the family, both in the Genus Regalecus, one found in the Atlantic Ocean and one in the Pacific Ocean. They are also known as the Pacific Oarfish, the King of Herrings, and the Ribbonfish and in Mexico as Pez Remo and Rey de Los Arenques. With their physical characteristics and undulating mode they believe to be the source of man Sea Serpent sightings. It’s common name “King of Herrings” is a nickname is derived from its crownlike appendage and being sighted near shoals of herrings. It’s common name Oarfish is attributed to the shape of the pelvic fins or the long slender shape of the fish itself. They are also known as “Earthquake Fish” because they are popularly believed to surface before and after an earthquake. With their physical characteristics and undulating mode they believe to be the source of man Sea Serpent sightings.

The Oarfish is the world’s longest ray-finned fish that has a moderately deep fusiform latterly compressed ribbon-like body with a depth that is 27% to 31% of standard length with convex upper and lower body profiles. They have a bluish or blackish head transitioning to a bright silver body with oblique black dashes or bars, or spot over all parts of the body. The dorsal and pelvic fins are crimson red. They have two head crests up to 1 meter long, the first with 3 to 6 rays and the second with 1 highly elongated ray. Their mouth is protrusible and opens at the front with a slightly projecting lower jaw that is equipped with minute teeth on both jaws.  hey have a pair of large eyes just above the mouth. They do not have an anal fin. Juveniles have deeply forked caudal fins with 3 or 4 rays with the middle one being robust; the adults do not have a caudal fin. Their dorsal fin is very long with 333 to 371 rays; their pelvic fins have one very elongated ray that reaches the anus; their pectoral fins are stubby while the pelvic fins are long, single-rayed, and reminiscent of an oar in shape, widening at the tip. The snout to vent length is 31% to 35% of standard length. They have 47 to 60 gill rakers. They do not have a swim bladder. They lack scales and the body has six or seven rows of tubercles of various sizes. The lateral line extends from above the eye and descends to the lower body extending to the caudal tip.

The Oarfish is a pelagic-oceanic species that is found as solitary individuals that is found in the epipelagic and mesopelagic zones of the open ocean and found at depths up to 1,000 m (3,280 feet) with an oceanodromous lifestyle. They reach a maximum length of 800 cm (26 feet) and weigh up to 272 kg (600 pounds).

The Oarfish swim by means of undulating its dorsal fin, and also swimming in a vertical position using undulatory movements of both its body and dorsal fin. They have a unique adaptation of self-amputation (autotomy) of the posterior part of the body past the vent which may involve only the caudal fin (or one to a few small adjacent vertebrae) or as far anterior as just before the abdomen that apparently occurs several times during its lifetime (serial autotomy) but do not damage any vital organs which are concentrated in the front portion of the body. These amputations are noted to occur several times throughout the lifetime of the fish and all fish over 1.5 m long have bodies shortened by this and most exhibit a healed-over stump or “terminus”. It is unclear why these amputations occur, as oarfish have no documented natural predators, so it is unlikely to be a predation response. They feed on deepsea planktonic crustaceans, small fishes, krill, shrimp and squids. They do not have a swim bladder. The lateral line extends from above the eye and decends to the lower body extending to the caudal tip.

They are known to harbor large quantities of different parasites. Reproduction occurs via broadcast spawning with female brood size numbers in the millions with reproduction occurring via broadcast spawning with eggs being large (2.5 mm in diameter), red in color and free-floating; there is no parental care provided for the young; their larvae have elongated bodies and can measure up to 10.4 cm (4.1 inches) in length. The Oarfish is poorly studied with very limited information available about their lifestyle and behavioral patterns including specific details on age, growth, longevity, movement patterns, diet, habitat use, and reproduction.

The Oarfish is very similar to the Glesne Oarfish, Regalecus glesne (5-11 rays in the second dorsal fin crest) from the Atlantic Ocean.

The Oarfish is a resident of all Mexican waters of the Pacific Ocean with the exception that they are absent from the northern half of the Sea of Cortez.

From a conservation perspective the Oarfish is currently considered to be of Least Concern with stable, widely distributed populations. Formerly considered rare, the species is now suspected to be relatively common, although sightings of healthy specimens in their natural habitat are unusual. They are found occasionally cast up on beaches. They are reputed to be unpalatable because the flesh is tasteless or otherwise unappetizing.