Overview

Brief Summary

Taxonomy

The ragfish became known to science in 1880, when Lockington obtained two juvenile specimens from a fish market in San Francisco. The two specimens were unfortunately lost in a fire caused by an earthquake that devastated California in 1906.Lockington described the ragfish as being nearly scaleless (only spinous scales on the lateral line) with bony prickles on the fin rays of each fin. Purple spots and blotches are distributed over a yellowish-brown ground colour, a round caudal fin, and small pelvic fins.Seven years later Tartelton H. Bean received a large fish (approximately 182cm) from Mr. Charles Willoughby that was beached in Damon, in the State of Washington. Bean recognised the close resemblance to the ragfish. However because of some differences to the ragfish, Bean described it as Acrotus willoughbyi, in honour of its finder, in 1888.73 years later Clemens and Wilby realised that Icosteus aenigmaticus and Acrotus willoughbyi represent the juveniles and adults of the same species.Still the relationship of the ragfish to other fish remains enigmatic. Many systematics researchers have placed the ragfish close to the butterfishes and their relatives (Stromateoidei), which it resembles superficially.However morphologically the ragfish is a mixture between the whalefishes and their relatives
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Introduction

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.
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Comprehensive Description

Biology

Adults occur near bottom; juveniles in shallow water or offshore near the surface (Ref. 50277). Feeds on jellyfish (Ref. 50277), fishes and squids (Ref. 2850), as well as octopuses (Ref. 4525).
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Biology

Juvenile ragfish differ remarkably from adults.Juveniles are light brown in colour and sprinkled with dark spots. They have a rounded caudal fin and pelvic fins below the pectoral fins.During development the colour changes to a dark chocolate brown, the pelvics disappear and the caudal fin changes to a forked appearance.It is believed that juvenile ragfish feed on medusa and jellyfish. Stomach contents of adult ragfish revealed additionally cephalopods, salps, and small fishes such as eel pouts (Zoarcidae).
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Distribution

National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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North Pacific: Japan to southeastern Alaska and to Point Loma, southern California, USA.
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Distribution habitat

The ragfish’ home is the North Pacific - north of Baja California, northwards to the Bering Sea, and eastwards to Japan.Juveniles are found on the surface, taking shelter under jellyfish, while adults are found in the bathypelagic, down to 1400 metres, and always close to the bottom.
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North Pacific: Bering Sea to southern California, Okhotsk Sea, and Pacific coast of southern Honshu, Japan.
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Physical Description

Morphology

Dorsal spines (total): 0; Dorsal soft rays (total): 52 - 55; Analspines: 0; Analsoft rays: 34 - 40
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Size

Maximum size: 2130 mm TL
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Max. size

213 cm TL (male/unsexed; (Ref. 2850))
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Diagnostic Description

Pectorals rounded, pedunculate (Ref. 6885). Generally of a chocolate color (Ref. 6885). Young more robust, with an expanded and rounded caudal fin, 5 pelvic rays, and a brown and yellow irregularly blotched with faint purple color, dusky on fins (Ref. 6885).
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Type Information

Type for Icosteus aenigmaticus
Catalog Number: USNM 27398
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Fishes
Collector(s): D. Jordan
Year Collected: 1880
Locality: Point Reyes, California, Marin County, California, United States, Pacific
  • Type: Lockington, W. N. 1880. Proceedings of the United States National Museum. 3 (123): 63.
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Type for Icosteus aenigmaticus
Catalog Number: USNM 39340
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Fishes
Preparation: Illustration
Collector(s): C. Willoughby
Year Collected: 1887
Locality: Quinaielt Indian Agency, Damon, Wash. Terr., Washington, United States, Pacific
  • Type:
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Ecology

Habitat

Habitat Type: Marine

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Known from seamounts and knolls
  • Stocks, K. 2009. Seamounts Online: an online information system for seamount biology. Version 2009-1. World Wide Web electronic publication.
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Environment

bathypelagic; marine; depth range 0 - 1420 m (Ref. 50550), usually 18 - 732 m (Ref. 2850)
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Depth range based on 5 specimens in 1 taxon.
Water temperature and chemistry ranges based on 2 samples.

Environmental ranges
  Depth range (m): 456.585 - 50000
  Temperature range (°C): 3.480 - 3.603
  Nitrate (umol/L): 34.816 - 43.838
  Salinity (PPS): 33.972 - 34.393
  Oxygen (ml/l): 0.370 - 1.669
  Phosphate (umol/l): 2.817 - 3.347
  Silicate (umol/l): 99.499 - 125.314

Graphical representation

Depth range (m): 456.585 - 50000

Temperature range (°C): 3.480 - 3.603

Nitrate (umol/L): 34.816 - 43.838

Salinity (PPS): 33.972 - 34.393

Oxygen (ml/l): 0.370 - 1.669

Phosphate (umol/l): 2.817 - 3.347

Silicate (umol/l): 99.499 - 125.314
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Depth: 18 - 732m.
From 18 to 732 meters.

Habitat: benthopelagic. Found offshore. Feeds on fishes and squids. Eaten by sperm whales. Spawns in the summer and winter (Ref. 6885). A 136 cm SL female probably produces about 435, 000 light amber coloured eggs (Ref. 6885).
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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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Life History and Behavior

Behavior

Behaviour

Juvenile ragfish are often sighted in association with jellyfish, which they use for shelter in the open ocean. The adults are probably strong swimming ‘cruisers’, searching for food close to the bottom.
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Icosteus aenigmaticus

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 2 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

CCTATATCTAGTATTTGGTGCATGAGCCGGTATAGTGGGTACAGCCTTAAGCCTACTCATCCGAGCTGAACTAAGCCAACCAGGCGCCCTTCTTGGGGACGACCAGATCTACAATGTAATTGTTACGGCACATGCCTTCGTAATAATTTTCTTTATAGTAATACCAATTATGATCGGGGGGTTTGGAAACTGACTCATTCCTCTAATAATTGGAGCCCCAGACATAGCATTCCCTCGAATAAATAACATAAGCTTTTGACTCCTCCCACCCTCCTTCCTTCTGCTCCTGGCCTCTTCCGGGGTTGAAGCCGGCGCTGGAACTGGCTGAACAGTATACCCACCCCTATCCGGGAATCTAGCCCACGCCGGAGCATCTGTTGACTTAACCATTTTTTCCCTACACTTAGCAGGAGTCTCCTCAATCCTTGGGGCCATTAACTTCATTACAACAATTATTAATATAAAACCTGCAGCCATCTCCCAATATCAAACACCCCTATTTGTGTGATCCGTCCTAATTACAGCCGTACTTCTTCTACTATCTCTGCCAGTCCTCGCTGCTGGTATTACTATGCTTCTTACAGACCGAAACCTAAATACAACCTTTTTTGACCCTGCAGGAGGGGGAGATCCAATCCTTTACCAACACTTA
-- end --

Download FASTA File
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Statistics of barcoding coverage: Icosteus aenigmaticus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNR - Unranked

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NatureServe Conservation Status

Rounded Global Status Rank: GNR - Not Yet Ranked

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Conservation

The ragfish is not thought to be threatened – it is not an important food fish and is rarely caught as bycatch. This is also the reason why only scarce data are available.Ragfish can probably outswim trawl nets towed at 2 to 3 knots, and therefore are unlikely to be an endangered
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Threats

Not Evaluated
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Wikipedia

Ragfish

The ragfish, Icosteus aenigmaticus, is a ray-finned fish of the northern Pacific Ocean; although a perciform, its skeleton is mostly cartilage, and the larvae have pelvic fins that disappear as they mature. It is the sole member of the family Icosteidae, and some authorities place it into its own order Icosteiformes.

The ragfish body is scaleless and limp, because of its cartilaginous skeleton and its flabby muscles. None of the fins have any spines. The dorsal and anal fins extend much of the length of the body, while the pelvic fins are absent. The coloration is generally a dark brown, and maximum known length is 2 m.

Ragfishes are found on the bottom from near the surface in the case of juveniles to 732 m (2,402 ft), occasionally down to 1,420 m (4,660 ft), for the adults. They are said to eat jellyfishes, other fish, squid, and octopus,[1] although recent catches show no squid beaks but large numbers of jellyfish.

The larvae make a remarkable transformation as they mature; the caudal fin shrinks, and the pelvic fins disappear.

Formerly, adult ragfishes were considered to be a different species, known then as Acrotus willoughbyi.[2]

References[edit]

  1. ^ Froese, Rainer and Pauly, Daniel, eds. (2013). "Icosteus aenigmaticus" in FishBase. August 2013 version.
  2. ^ http://www.photolib.noaa.gov/htmls/figb0639.htm
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