Overview

Comprehensive Description

Biology

A rare species (Ref. 26346) found on outer continental shelves and upper slopes (Ref. 247). Probably feeds on deepwater bottom fishes and invertebrates (Ref. 247). Ovoviviparous (Ref. 205), length at birth 21-28 cm TL (Ref. 26346). Utilized as fishmeal and possibly as food fish (Ref. 247).
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Distribution

Range Description

The distribution of this species is poorly defined because there are few definite records anywhere (L.J.V. Compagno pers. comm. 2007).

Northwest Atlantic:
There are two records of this species from the northwest coast of Cuba (L.J.V. Compagno pers. comm. 2007).

Northeast Atlantic:
Madeira, Canary Islands, Portugal, France and in the Mediterranean Sea from Catalan Sea, Spain, France; Ligurian Sea off northern Italy; Sicily; Israel (L.J.V. Compagno pers. comm. 2007).
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Northeast Atlantic: Madeira, France, and western Mediterranean.
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Mediterranean Sea, Atlantic.
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Physical Description

Morphology

Dorsal spines (total): 0; Analspines: 0; Analsoft rays: 0
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Size

Maximum size: 1430 mm TL
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Max. size

143 cm TL (male/unsexed; (Ref. 26346))
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Diagnostic Description

Diagnosis: Somniosus rostratus is distinguished from S. longus in having overall length of second dorsal shorter than first dorsal fin 76-88% (vs. almost equal 91-100%); horizontal diameter of eye less than 37% (mean 33%) of length from snout tip to eye (vs. >37, mean 46%); number of tooth rows in upper jaw 53 (vs. 56-57); and spiral valve counts 23 (vs. 26-27) (Ref. 50224).Description: Grey or brown in color (Ref. 26346). Short, rounded snout; equal-sized dorsal fins, first dorsal fin on back closer to pectorals than pelvic fins; long ventral caudal lobe; short keels on base of caudal fin (Ref. 247).
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Ecology

Habitat

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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Habitat and Ecology

Habitat and Ecology
Bathydemersal deep water species reported at depths of 180–2,220 m (Barrull and Mate 2002, Compagno et al. 2005). Found on on or near the sea bottom, over sandy mud substrate on the outer continental shelves and upper slopes (Compagno in prep.). Serena (20005) reports that it appears to prefer bathyal grounds deeper than 1,000 m in the western Mediterranean basin.

Attains a maximum size of about 140 cm total length (TL); size at birth is between 21 and 28 cm TL; males are mature at 71 cm TL and females at 80 cm (Compagno et al. 2005). Reproduction is aplacental viviparous, with 8–17 pups per litter (Tortonese 1956, Barrull and Mate 2002, Compagno in prep.). Reproductive age, periodicity, gestation time, rate of population increase and natural mortality are unknown.

This species feeds on mesobathyal cephalopods such as Histiotheuthis spp. and Todarodes sagittatus (J. Guallart pers. obs. 2007). Although specimens of this species are usually captured with bottom fishing gears, the finding of these highly-mobile cephalopods in the stomach contents may be interpreted as an indicator that S. rostratus moves throughout the deeper reaches of the water column, a propensity that may partially explain the scarcity of captures in deep demersal fisheries.

Systems
  • Marine
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Environment

bathydemersal; marine; depth range 200 - 1000 m (Ref. 247)
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Depth range based on 1 specimen in 1 taxon.

Environmental ranges
  Depth range (m): 683 - 683
 
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Depth: 200 - 1000m.
From 200 to 1000 meters.

Habitat: bathydemersal.
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Life History and Behavior

Life Cycle

Ovoviviparous (Ref. 247). Young born at 21-28 cm (Ref. 26346). Distinct pairing with embrace (Ref. 205).
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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Somniosus rostratus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 2
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
DD
Data Deficient

Red List Criteria

Version
3.1

Year Assessed
2009

Assessor/s
Séret, B., Guallart, J., Vacchi, M., Mancusi, C. & McCormack, C.

Reviewer/s
Cavanagh, R.D., Valenti, S.V., Compagno, L.J.V. & Fowler, S.L. (Shark Red List Authority)

Contributor/s

Justification
The Little Sleeper Shark (Somniosus rostratus) is a rare, moderate sized (to 143 cm TL) deepwater shark known from a few records on the outer continental shelf and upper slope in the northeast Atlantic and western Mediterranean Sea, at depths of 180–2,220 m. Also recorded from Israel in the eastern Mediterranean and Cuba in the northwest Atlantic. Occasionally taken as bycatch in deep bottom trawl and bottom longlines fisheries and sometimes landed under the same commercial category as the other sleeper sharks although usually discarded. Very little is known of the popualtion of this species. The scarcity of captures could be related to a natural low-density of the population. It is also possible that the species' bathymetric distribution extends deeper than the depths currently surveyed. The species may occur throughout the deeper reaches of the water column, beyond the depth of many demersal fisheries. The ban on bottom trawling below depths of 1,000 m in the Mediterranean Sea probably affords the species some protection in this region, although it is still vulnerable to capture in the upper half of its depth range there, and by intense deepsea fisheries operating in areas of the northeast Atlantic. The relatively small range of this species, compared to most other sleeper sharks, and rarity in an area which has been subject to very heavy fishing pressure for a long period are cause for concern. Furthermore the species may have limiting life-history characteristics, like other deepwater squaloids, and therefore may not be sufficiently fecund to withstand heavy fishing pressure. Given these concerns and in the absence of any information on trends, this species is assessed as Data Deficient at present. Bycatch levels should be quantified and monitored to provide information to make a full evaluation of this species status.
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Population

Population
An apparently rare, poorly known species (Compagno in prep, L.J.V. Compagno pers. comm. 2007). No information exists on the relationship between the northeast Atlantic and Mediterranean populations. Mostly known from single records and a few specimens in the scientific literature (L.J.V. Compagno pers. comm. 2007). This species has not been recorded during the MEDITS (at depths of 10–800 m) scientific trawl surveys conducted throughout the Mediterranean Sea.

Population Trend
Unknown
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Threats

Major Threats
Occasionally taken as by-catch on longlines and with bottom trawls in the eastern Atlantic (Compagno in prep.), but often recorded under the general category “sleeper sharks" or simply “sharks”. In the Mediterranean coast of Spain it is regularly discarded at sea and not landed although post-discard survival is likely very low (J. Guallart pers. obs. 2007). No species-specific catch estimates are available.

Intense deepwater fisheries operate in areas of the northeast Atlantic. For example, a target fishery for deep-water squaloid sharks operated off Portugal at depths of 800–1,400 m since 1992 (DELASS 2003). Catches decreased rapidly and, by 1996, only one longliner was engaged in it at full time. Most of the catch consists of Centrophorus granulosus, though other deep-water species such C. squamosus and C. coelolepis are also caught in small quantities (DELASS 2003).

This species is also a bycatch of the general demersal and black scabbardfish fisheries in the Azores, although species-specific data are not available (DELASS 2003). A recent ban on bottom trawling below 1,000 m in the Mediterranean Sea (see Conservation Measures) may afford this species some protection, particularly if it is mainly distributed at greater depths. However, the species is still vulnerable to capture in fisheries in the upper half of its bathymetric range.

This species may be slow growing and slow to mature, like other deepwater Squaloid sharks, making it vulnerable to population depletion in fisheries. The relatively small range of this species, compared to most other sleeper sharks, and rarity in an area, which has been subject to very heavy fishing pressure for a long period, is of concern (L.J.V. Compagno pers. comm. 2007).
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Data deficient (DD)
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Management

Conservation Actions

Conservation Actions
No species-specific management or conservation measures are currently in place.

The General Fisheries Commission for the Mediterranean (GFCM) banned bottom trawling below depths of 1,000 m in the Mediterranean in February 2005 and this came into force in September 2005. The measure was adopted by consensus by all members of the GFCM, which include: Albania, Algeria, Bulgaria, Croatia, Cyprus, EC, Egypt, France, Greece, Israel, Italy, Japan, Lebanon, Libya, Malta, Morocco, Romania, Slovenia, Serbia and Montenegro, Spain, Syria, Tunisia, and Turkey.

Like many deeper water species more information on biology, ecology and population trends are required to fully assess the status of this species and any future conservation needs.

The development and implementation of management plans (national and/or regional e.g., under the FAO International Plan of Action for the Conservation and Management of Sharks: IPOA-Sharks) are required to facilitate the conservation and management of all chondrichthyan species in the region.
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Relevance to Humans and Ecosystems

Benefits

Importance

fisheries: minor commercial; price category: unknown; price reliability:
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Wikipedia

Little sleeper shark

The little sleeper shark, Somniosus rostratus, is a sleeper shark of the family Somniosidae found in the northeast Atlantic, western Mediterranean, and western Pacific around New Zealand, at depths of between 200 and 1,000 m. Its length is up to 1.43 m.

References[edit]

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