Animal Diversity Web

Geographic Range

Common in warmer parts of all oceans.Western Mediterranean and Atlantic from the North Sea southwards (Unesco 1989).

• Biogeographic Regions
• indian ocean
  • native
• atlantic ocean
  • native
• pacific ocean
  • native

Habitat

The Remora is a pelagic marine fish that is usually found in the warmer parts of most oceans clinging on to large sharks, sea turtles, bony fishes and other marine mammals (Marshall 1965).

Physical Description

Remora remora is a short, thick-set sucking fish (Marshall 1965).The Remora has 28-37 long slender gillrakers, 21-27 dorsal fin rays, 20-24 anal fin rays, and 25-32 pectoral fin ray (Unesco 1989). The dorsal and anal fins lack spines (Nelson 1984). The Remora has no swim bladder and uses a sucking disc on the top of its head to obtain rides from other animals such as large sharks, and sea turtles. The sucking disk, developed from a transformed spinous dorsal fin, contains 16-20 transverse movable lamina which create a partial vaccuum permitting the Remora to obtain rides on larger animals (Nelson 1984). The head is rather long and flattened, 26-29% of the standard length, with the disc being 34-42% of the standard length. The lower jaw projects past the upper jaw and the teeth, located in jaws and vomer in a villiform patch, are sharply pointed and recurved slightly inward. The scales are small and cycloid (Unesco 1989, Nelson 1984), and the color, nearly uniform above and below, is blackish or brownish (Marshall 1965). The Remora grows to about 18 inches (Marshall 1965).

• Other Physical Features
• bilateral symmetry

Reproduction

Near nothing is known about the Remora's breeding habits or larval development.Specimens as small as an inch have been noted to resemble adults in all aspects except size, but nothing is known about how or where they spawn (McClane 1998).

Behavior

The Remora is most often found offshore in the warmer parts of all oceans attached to sharks and other marine fishes and mammals (Unesco 1989). Based on observations of the species in captivity, Remora remora requires a swift passage of water over the gills and cannot survive in still waters (Bohlke and Chaplin 1993).The Remora is not considered to be a parasite, despite its being attached to the host. Instead they are considered to have a commensal relationship with their host, since they do not hurt the host and are just along for the ride. It has been suggested that the relationship is symbiotic since the Remora can obtain its food acting as a cleaner fish and removing parasites from the host, thus benefitting both. It is not known whether the sharks tolerate the Remora's presence or are just unable to catch them, but no Remoras have ever been found in a sharks stomach. Instead, some small specimens have been found in the inside of sharks mouths, clinging to the roof (McClane 1998).

• Key Behaviors
• natatorial
• motile

Communication and Perception

• Perception Channels
• tactile
• chemical

Food Habits

The Remora clings to a host, such as large sharks, sea turtles, bony fishes, rays, and marine mammals.The Remora has long been thought to detach itself from its host and dart around feeding on its scraps (Herald 1962). It was later felt that ectoparasites on the host's body or gill chambers formed an important part of their diet. Recently it was shown that both of these are utilized as food sources and that planktonic organisms and fish may also be part of the Remora's diet (Bohlke and Chaplin 1993).

Economic Importance for Humans: Positive

The remora is of unique value to humans. The fish itself is not generally eaten, but is instead used as a means of catching large fish and sea turtles. Fishermen in countries around the world use them by attaching a line to their tails and then releasing them. The remora will then swim off and attach itself to a large fish or turtle, which can then be pulled in by a careful fisherman. The remora is not held in high esteem as a food fish, although the Australian aborigines are said to eat them after using them on fishing trips. On the other hand, aborigines from the West Indies never ate their "hunting fish" and instead sang songs of praise and reverence to them. (McClane, 1998)

Economic Importance for Humans: Negative

No known negative impacts

Conservation Status

• IUCN Red List

  No special status

• US Federal List

  No special status

• CITES

  No special status

Other Comments

The ancient Greeks and Romans had written widely about Remoras and had ascribed to them many magical powers such as the ability to cause an abortion if handled in a certain way. Shamans in Madagascar to this day attach portions of the Remora's suction disk to the necks of wives to assure faithfulness in their husbands absence.

The ancient Romans actually attributed the death of Emperor Caligula to Remoras. They were believed to be fastened onto his ship, holding it back and allowing the enemy ships to overtake it.The Latin name Remora actually means "holding back" (McClane 1998).

Contributors

Mark Leao (author), SUNY College of Environmental Science and Forestry, Kimberly Schulz (editor), SUNY College of Environmental Science and Forestry.

References

Bohlke, J., C. Chaplin. 1993. Fishes of the Bahamas and adjacent tropical waters. Wynewood, PA: First University of Texas Press.

Herald, E. 1962. Living Fishes of the World. Garden City, NY: Doubleday and Co. inc..

Marshall, T. 1965. Fishes of the Great Barrier Reef and Coastal Waters of Queensland. Sydney, Australia: Livingston publishing Co..

McClane, J. 1998. McClanes New Standard Fishing Encyclopedia and International Fishing Guide. New York, NY: Gramercy Books.

Nelson, J. 1984. Fishes of the World. Wiley- Interscience Publishers.

United Nations Educational, Scientific, and Cultural Organization (Unesco), 1989. Fishes of the North Eastern Atlantic and Mediterranean. Fontenoy, Paris: Chaucer press.