Icosteus aenigmaticus

The ragfish, Icosteus aenigmaticus is a large species that occurs only in the Northern Pacific. Although ragfish can reach up to 2 metres long, it was unknown to science until 1880.

The common name and the genus name of the mysterious ragfish, Icosteus aenigmaticus, refer to its flabby appearance and its weakly-ossified skeleton. The species name refers to its unknown relationship with other fish.

Adult ragfish are yellowy-brown in colour with purple spots and blotches. They have few scales and bony prickles on the fin rays.

Juveniles and adults of the species differ significantly and for a long time were considered separate species.

Species detail

  • Icosteus aenigmaticus
    Taxonomy

    Mystery surrounds the ragfish’s evolutionary history. Discover what we know.

  • Specimen and observational data for Icosteus aenigmaticus
    Distribution and habitat

    Icosteus aenigmaticus lives in the North Pacific Ocean. Young ragfish swim close to the surface, whereas adults are found up to 1400 metres deep. Find out more.

  • Icosteus aenigmaticus
    Biology

    Young ragfish differ significantly from adults and were originally described as separate species. Find out more about this fish’s unusual development.

  • Icosteus aenigmaticus
    Behaviour

    Juvenile ragfish are often sighted in association with jellyfish, find out more.

  • Adult ragfish caught in ca. 870 metres.
    Conservation

    Ragfish are fast swimmers and rarely caught by fishermen. It is unlikely they are endangered.

  • Icosteus aenigmaticus
    References

    Get more reference material for Icosteus aenigmaticus.

Images

Icosteus aenigmaticus
Icosteus aenigmaticus (Lockington, 1880), 112mm large juvenile specimen (UW 041565).
Icosteus aenigmaticus

Icosteus aenigmaticus (Lockington, 1880), 95mm large juvenile specimen (UW 041565).

Icosteus aenigmaticus

Icosteus aenigmaticus,(Lockington, 1880), 95mm large juvenile specimen (UW 041565).

Adult ragfish caught in ca. 870 metres

Adult ragfish caught in ca. 870 metres.

Icosteus aenigmaticus

 Drawings of an adult ragfish Icosteus aenigmaticus

© Goode and Bean 1895
Icosteus aenigmaticus

Drawings of a juvenile ragfish Icosteus aenigmaticus.

© Goode and Bean 1895
Icosteus aenigmaticus

Icosteus aenigmaticus, drawing from a specimen collected by H.M.S. Challenger.

© Allen, G. H. 2001
Icosteus aenigmaticus

Specimen and observational data for Icosteus aenigmaticus 

Author

Peter Konstantinidis

Ph.D. student, Department of Zoology.

A word from the author

I started a small project on this unusual and enigmatic fish because I was fascinated by its strange appearance. I was surprised how little is known about this mysterious fish, which can reach 2 metres in length.

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