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.
Mystery surrounds the ragfish’s evolutionary history. Discover what we know.
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.
Young ragfish differ significantly from adults and were originally described as separate species. Find out more about this fish’s unusual development.
Juvenile ragfish are often sighted in association with jellyfish, find out more.
Ragfish are fast swimmers and rarely caught by fishermen. It is unlikely they are endangered.
Get more reference material for Icosteus aenigmaticus.
Icosteus aenigmaticus (Lockington, 1880), 95mm large juvenile specimen (UW 041565).
Icosteus aenigmaticus,(Lockington, 1880), 95mm large juvenile specimen (UW 041565).
Adult ragfish caught in ca. 870 metres.
Drawings of an adult ragfish Icosteus aenigmaticus© Goode and Bean 1895
Drawings of a juvenile ragfish Icosteus aenigmaticus.© Goode and Bean 1895
Icosteus aenigmaticus, drawing from a specimen collected by H.M.S. Challenger.© Allen, G. H. 2001
Specimen and observational data for Icosteus aenigmaticus
Ph.D. student, Department of Zoology.
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.