Elasmobranchs - North Sea, Skagerrak, and Eastern English Channel|
Fact Sheet Title Fact Sheet |
| | Elasmobranchs - North Sea, Skagerrak, and Eastern English Channel |
Demersal elasmobranchs in the North Sea, Skagerrak, and Eastern Channel |
| Data Ownership | This document provided, maintained and owned by International Council for the Exploration of the Sea (ICES) , is part of ICES Advice data collection. |
| Monitoring Range Max2008. Monitoring Evolution: Blonde ray - Southern North Sea and Eastern English Channel ; Thornback ray - North Sea, Skagerrak and Kattegat and Eastern English Channel ; Small-eyed ray - English Channel ; Spotted ray - North Sea, Skagerrak, Kattegat, and Eastern English Channel ; Undulate ray - English Channel ; Cuckoo ray - North Sea, Skagerrak and Kattegat ; Common skate - North Sea, Skagerrak and Kattegat ; Starry ray - Norwegian Sea, North Sea, Skagerrak and Kattegat ; Other rays and skates - North Sea, Skagerrak, Kattegat and Eastern English Channel . ident Block | ident Block | | Species List: | Species Ref: en - Rays, stingrays, mantas nei, fr - Raies, pastenagues, mantes nca, es - Rayas, pastinacas, mantas nep, ru - Скатообразные (скаты, хвостоколы, манты) |
Species Ref: en - Dogfish sharks, etc. nei, fr - Squaliformes nca, es - Squaliformes nep |
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| ident Block Elasmobranchs - North Sea, Skagerrak, and Eastern English Channel
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fao Div |
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27.3.a | Skagerrak and Kattegat (Division 27.3.a) |
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27.4.a | Northern North Sea (Division 27.4.a) |
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27.4.b | Central North Sea (Division 27.4.b) |
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27.4.c | Southern North Sea (Division 27.4.c) |
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27.7.d | Eastern English Channel (Division 27.7.d) |
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| Aq Res | Biological Stock: Yes
Value: Sub-Regional Management unit: No
Reference year: 2008
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Considered a management unit: An aquatic resource or fishery is
declared as [Fishery] Management Unit if it is
effectively the focus for the application of selected
management methods and measures, within the broader
framework of a management system. According to the FAO
Glossary for Responsible Fishing, "a Fishery Management
Unit (FMU) is a fishery or a portion of a fishery
identified in a Fishery Management Plan (FMP) relevant
to the FMP's management objectives." FMU's may be
organised around fisheries biological, geographic,
economic, technical, social or ecological dimensions ,
and the makeup and attribute of a fishery management
unit depends mainly on the FMP's management
objectives. |
Jurisdictional distribution: Jurisdictional qualifier (e.g.
"shared", "shared - highly migratory") of the aquatic
resource related with its spatial distribution. |
Environmental group: Classification of the aquatic
resource according to the environmental group (e.g.
pelagic invertebrate, or demersal fish) to which the
species belong. |
Reference Year: The Reference Year is the last year considered in the stock assessment and/or fishery status. |
| | | | Aq Res State Trend
In the absence of defined reference points, the status of the stocks of demersal skates and rays (members of the family Rajidae) and demersal sharks (of the genera Scyliorhinus
,
Mustelus, and Squatina) cannot be evaluated. The following provides a qualitative summary of the general status of the major species based on surveys and landings:
Species
Scientific name
Area
State of stock
Common skate
Dipturus
batis
IVa (likely merging with VIa & IIa)
Depleted
Thornback ray
Raja
clavata
IVc, VIId
Stable/increasing
IVa,b
Uncertain
Spotted ray
Raja
montagui
IVb,c
Stable/increasing
Starry ray
Amblyraja
radiata
IVa,b, IIa
Stable
Cuckoo ray
Leucoraja
naevus
IVa,b
Stable
Blonde ray
Raja
brachyura
IVc, VIId (patchy occurrence)
Uncertain
Undulate ray
Raja
undulata
VIId, merges with VIIe
Uncertain, reasons for concern
Lesser-spotted dogfish
Scyliorhinus
canicula
IVa,b,c, VIId
Increasing
Smooth hound & Starry smooth hound
Mustelus
mustelus & Mustelus
asterias
IVa,b,c, VIId
Increasing
Angel shark
Squatina
squatina
IVa,b,c, VIId
Extirpated
Skates and rays (
Rajidae
)
Common skate –
is depleted. It was formerly widely distributed over much of the North Sea but is now found only rarely, and only in the northern North Sea. The distribution extends into the west of Scotland and the Norwegian Sea.
Thornback ray –distribution area and abundance have decreased over the past century, with the stock concentrated in the southwestern North Sea where it is the main commercial skate species. Its distribution extends into the eastern Channel. Survey catch trends in Division IVc have been stable/increasing in recent years. The status of R.
clavata in Divisions IVa,b is uncertain.
Spotted
ray –
stable/increasing. The area occupied and abundance has fluctuated without trend.
Starry
ray – stable. Survey catch rates increased from the early 1970s to the early 1990s and have decreased slightly since then.
Cuckoo
ray –
uncertain. Since 1990 the area occupied has fluctuated without trend. Abundance has decreased since the early 1990s, but has been stable in recent years.
Blonde
ray – uncertain. This species has a patchy occurrence in the North Sea. It is at the edge of its distributional range in this area.
Undulate
ray – uncertain, reason for concern. Mainly limited to Division VIId where it merges with Division VIIe. Occasional vagrants in Division IVc. The biology of the species and recent disappearance from surveys give rise to concern. It has a patchy and localized distribution, possibly forming discrete stocks, which make the undulate ray sensitive to local depletion. Additionally, the species has disappeared from the English beam trawl survey in Division VIId in the last two years.
Demersal
sharks
Lesser spotted dogfish – abundance and area occupied are increasing.
Smooth hound and starry smooth hound
– abundance appears to have been increasing in recent years both in survey catches and in commercial and recreational fisheries, but the stock status is uncertain. Identification by species is considered unreliable in the surveys.
Angel
shark – is now extirpated in the North Sea. It may still occur in Division VIId.
Habitat Bio Depth Zone: Shelf (50 m - 200 m). Vertical Dist: Demersal/Benthic. Geo Dist Geo Dist: Shared between nations Water Area Overview Spatial Scale: Sub-Regional Water Area Overview | Water Area Overview Elasmobranchs - North Sea, Skagerrak, and Eastern English Channel
fao Div | 27.3.a: Skagerrak and Kattegat (Division 27.3.a) | 27.4.a: Northern North Sea (Division 27.4.a) | 27.4.b: Central North Sea (Division 27.4.b) | 27.4.c: Southern North Sea (Division 27.4.c) | 27.7.d: Eastern English Channel (Division 27.7.d) |
| | | | Water Area Overview |
Water Area OverviewElasmobranchs - North Sea, Skagerrak, and Eastern English Channel Aq Res Struct Biological Stock: Yes Exploit
Factors affecting the fisheries and the stock
The effects of regulations
In 1999 the EC introduced a TAC for skates and rays. This TAC was gradually decreased. Based on the level of recent landings it is obvious that the current TAC has become restrictive for some countries, which may increase discarding. Discard survivorship, however, is not known. There are no management measures in place for the demersal sharks ( Scyliorhinus
,
Mustelus
,
Squatina) in this ecoregion.
Bio Assess Assess Models Methodology
Scientific basis
Data and methods
Survey data are the basis for the advice of skates, rays, and demersal sharks in the North Sea (examples in Figure 6.4.26.2).
In most countries skates and rays are landed together, most often sorted in particular size categories, rather than by species. They are usually gutted, and sometimes only wings are landed. For assessment purposes, species-specific catch data are essential. Only some countries report (part of) the landings by species, e.g. Sweden and . As a result of market sampling programmes the species composition of the landings can now be estimated for some of the countries landing skates and rays. This should improve from 2008 onwards because the EC now requires species-specific landings data.
Uncertainties in assessment and forecast
The analysis of survey data is hampered by uncertainties about the proper identification of some species of skate, and starry ray may have been misidentified as thornback ray on some occasions. This leads to problems in the interpretation of some survey data.
Comparison with previous assessment and advice
In 1997 ICES gave an overview of the relative status of the main skate species in the North Sea. In 2005 ICES produced advice for these species for the first time. ICES previously recommended that the catches for skates and rays be set to zero if, and only if skates and rays were landed as a generic group. Since it is now required to report by species, ICES is now providing advice for the main species. The basis for the advice is the same as in 2006.
| Figure 6.4.26.1. Rays and skates in the North Sea, Skagerrak, and eastern English Channel. Landings (in t) of all species combined. Data for 2007 are incomplete. |
| Figure 6.4.26.2. Demersal elasmobranchs in the North Sea. Time-series of catch rates (number per hour) for thornback ray, spotted ray, starry ray, cuckoo ray, lesser spotted dogfish, and smooth hounds (smooth hound in black, starry smooth hound in white, and none determined data in grey). Data from the IBTS quarter 1 survey, roundfish sampling areas 1–7. |
Sci Advice
Single-stock exploitation boundaries
No fisheries Species where indicators show extirpation
Angel shark
This species is (nearly) extirpated in the North Sea and eastern English Channel and should receive the highest possible protection.
No target fisheriesSpecies where indicators show depletion
Common skate
Undulate ray
Target fisheries for these species should not be permitted and measures should be taken to minimize bycatch.
Status quo
catch
Species where indicators show stability or increase
Spotted ray
Starry ray
Cuckoo ray
Thornback ray in Division IVc
Fishing mortality should not increase and the fishery should be closely monitored. Measures to deter fisheries that target spawning concentrations of thornback ray in Division IVc should be considered because this is the most vital part of the thornback ray spawning in the southwestern North Sea.
Smooth hound &
Starry smooth hound
These species have a relatively higher productivity than similar elasmobranchs and can probably sustain fisheries. Management measures should prevent overexploitation. Fisheries should only expand when accompanying measures lead to improved data collection and biological studies to ensure its sustainable harvest.
Lesser spotted dogfish
The stock shows a general increase in abundance and they have a high discard survival. The current exploitation rates on this species appear to be sustainable. As there are no apparent detrimental impacts on the stock from current commercial fisheries, no management actions are required for this species at this time.
No advice
Species where indicators are unknown
Blonde ray
Thornback ray in Division IVa,b
Because these species have a tendency to form aggregations, they may be prone to localized depletion.
Conclusion on exploitation boundaries
Subject to the individual recording of landed species, combined catches for demersal skates and rays should be set on the basis of the recent average landings (2002–2006). Targeted fisheries of the most threatened species (common skate and undulate ray) should not be permitted, and measures should be taken to minimize bycatch.
Angel shark should not be landed and, as inshore species, are likely to have a reasonable discard survival (depending on capture method).
Year
ICES Advice
Single-stock exploitation boundaries
Predicted catch corresponding to advice
Predicted catch corresponding to single-stock exploitation boundaries
Agreed
TAC (1)
ICES landings
1992
No advice
5.8
1993
No advice
5.8
1994
No advice
6.4
1995
No advice
6.3
1996
No advice
6.4
1997
No advice
4.6
1998
No advice
4.6
1999
No advice
6.1
3.4
2000
No advice
6.1
4.0
2001
No advice
4.8
4.0
2002
Reduce exploitation
4.8
3.6
2003
No advice
4.1
3.8
2004
No advice
3.5
2.5
2005
No advice
3.2
3.0
2006
Zero catch
F=0
0
2.7
2.8
2007
Zero catch
F=0
0
2.2
(1.1) (2)
2008
Zero catch
F=0
0
1.6
2009
Combined catches of recent average landings (2002–2006)
NA
3.1 (3)
NA
2010
Same advice as 2009
NA
3.1 (3)
Weights in ‘000 t.
(1) EU only.
(2) Preliminary data.
(3) Subject to the individual recording of landed species, no targeted fisheries and minimal bycatch of common skate and undulate ray, and no landings of angel shark.
Management Management unit: No Objectives
Management objectives have not been adopted. An EC Action Plan on elasmobranchs is under development in 2008.
Advice
Management considerations
North Sea demersal elasmobranchs are landed as a bycatch in demersal fisheries. A few inshore vessels target skates and rays. They have usually been landed and reported in mixed categories such as “skates and rays” and “sharks”. For assessment purposes species-specific landings data are essential. Since 2008 countries are obliged to report landings for the major skate species separately. On the basis of a longer track record on a species basis (at least five years) it will be possible in future to advise on species-specific catches.
From 2005 to 2008 the TAC for North Sea skates and rays has been reduced by approximately 50%, and is now significantly lower than average recent landings. TACs only regulate the landings, and a low TAC on a low-value bycatch species could induce more discards. Because the elasmobranch species are caught as a bycatch in demersal fisheries, they would benefit from a reduction in the overall demersal fishing effort.
Elasmobranchs are typically slow growing, have a high age-at-maturity and a low reproductive capacity. Measures to afford protection to the largest individuals should be considered. A Maximum Landing Length (MLL) of 100 cm for all skates and rays would be beneficial for common skate while not influencing most other species.
Landings of demersal sharks are not effectively restricted in the North Sea. Although lesser spotted dogfish are generally discarded, markets have developed for smoothhounds. Appropriate species-specific landings (for Scyliorhinus spp.) and genus-specific landings (for Mustelus spp.) are required before the level of a status quo catch could be advised on.
Sources ICES. 2008. Report of the ICES Advisory Committee, 2008. ICES Advice, 2008. |
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