Aq Res State Trend
The stock boundaries for demersal elasmobranch species in Subareas VIII and IX are unknown.
Skates (
Rajidae
)
Reported landings of skates (the groups as a whole) in the area seem stable or slightly declining in recent years (Figure 7.4.12.1).
Analyses of lpue from the Basque trawl fleet since 1996 indicate that there has been a decrease in skate abundance (mainly cuckoo ray
Leucoraja
naevus and thornback ray
Raja
clavata) in Divisions VIIIa,b,d since the 1998 peak. Landings have also decreased since 1996, but have been more stable in recent years (Table 7.4.12.1).
In Division VIIIc, results obtained from groundfish surveys indicate an increase in thornback ray biomass since 1996. Survey data for the cuckoo ray seems to indicate an increasing trend in biomass although there is considerable year-to-year variability.
Surveys in Subarea IX were judged to be inadequate for estimating abundance trends. In this subarea, skate landings have been stable since 1996, averaging 1800 t year
−1.
The status of the less common skate species is unknown due to the lack of species information in landings and their low frequencies in surveys.
Lesser-spotted dogfish (
Scyliorhinus
canicula
)
Reported landings of lesser-spotted dogfish in the area seem stable or slightly decreasing in recent years (Figure 7.4.12.2).
Analyses of lpue from the Basque trawler fleet indicate that the lpue of lesser-spotted dogfish in Divisions VIIIa,b,d has increased from 1994 to 2006. In 2007 a slight decrease in lpue was observed (Table 9.4.12.2). Estimates from groundfish surveys indicate an increase in the biomass of this species in Division VIIIc since 2002. Overall the population of lesser-spotted dogfish in Subarea VIII appears to be stable or slightly increasing (Figure 7.4.12.3).
Landings from Subarea IX decreased since 2004 by more than a factor of two. However, in this area lesser-spotted dogfish is essentially a bycatch from other fisheries, so the decrease in landings during the last few years may be related to changes in the effort distribution targeting different species, and/or better species identification at Portuguese landing ports.
Other
demersal
elasmobranch
species
The state of other elasmobranch species (e.g. smooth hounds
Mustelus spp.) is unknown due to a lack of species differentiation in landings and the short and discontinuous nature of relative abundance indices.
The available landing data of smoothhounds showed that landings in Subarea VIII have increased sharply since 1996, from 151 t to a peak of 500 t in 2006. In Subarea IX
Mustelus spp. landings have declined since 1999.
Spawning biomass in relation to precautionary limits
Fishing mortality in relation to precautionary limits
Fishing mortality in relation to high long-term yield
Fishing mortality in relation to
agreed target
Comment
Unknown
Unknown
Unknown
N/a
Habitat Bio
Depth Zone: Shelf (50 m - 200 m). Vertical Dist: Demersal/Benthic.
Exploit
Factors affecting the fisheries and the stock
The effects of regulations
There are no TACs for demersal elasmobranchs.
Bio Assess
Assess Models
Methodology
Scientific basis
Data and methods
Survey data and commercial data are the basis for the qualitative assessments of the overall status of skates and demersal sharks in the Bay of Biscay and the Iberian region.
Uncertainties in assessment and forecast
In general data on these species are limited. The lack of species-specific information in the landings is a particular problem. Only lesser-spotted dogfish is currently reported to species level.
Comparison with previous assessment and advice
ICES has not previously produced advice for these species and stocks.
Results
Table 7.4.12.1 Demersal elasmobranchs in the Bay of Biscay and Iberian waters. Nominal landings (tonnes) of smooth hounds by Subarea and country (Source: ICES).
Smooth hounds unident. (
Mustelus
spp.) - ICES Area VIII
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007*
Belgium
.
.
.
.
.
.
.
.
+
0,1
0,1
.
France
96,6
115
158
47,8
142
149
188
321
407
394
437
354
Portugal
.
.
.
.
+
.
.
.
1
.
.
Spain (Basque Country)
53
56
57
46
61
58
85
58
56
54
62
45
Total
150
170
214
94
202
207
273
379
464
448
500
399
* provisional data
Smooth hound (
Mustelus mustelus
) - ICES Area IX
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007*
Portugal
5
2
4
4
2
2
2
1
1
10
25
45
Total
5
2
4
4
2
2
2
1
1
10
25
45
* provisional data
Smooth hounds
unident
. (
Mustelus
spp.) - ICES Area IX
1999
2000
2001
2002
2003
2004
2005
2006
2007*
Portugal
72
39
41
43
50
35
24
11
11
Total
72
39
41
43
50
34
24
11
11
* provisional data
Table 7.4.12.2 Landings (t), effective effort (fishing days = trips*(days/trip)), and lpue (landings in kg/day) of lesser-spotted dogfish, Rajidae and spurdog of the Bakk trawler fleet, recorded at Basque Country (Spain) ports in the period 1994–2007.
BAKA trawl-ON-VIIIa,b,d
Lesser-spotted dogfish
Rajidae
spurdog
Year
Landings (t)
Effort (days)
lpue
(kg/days)
Landings (t)
Effort (days)
lpue
(kg/days)
Landings (t)
Effort (days)
lpue
(kg/days)
1994
112
5619
20
179
5619
32
32
5619
6
1995
202
4474
45
505
4474
113
23
4474
5
1996
206
4378
47
471
4378
108
45
4378
10
1997
242
4286
56
549
4286
128
34
4286
8
1998
303
3002
101
598
3002
199
25
3002
8
1999
231
2337
99
362
2337
155
12
2337
5
2000
228
2227
102
272
2227
122
38
2227
17
2001
217
2118
103
292
2118
138
9
2118
4
2002
331
2107
157
265
2107
126
12
2107
5
2003
303
2296
132
219
2296
95
3
2296
1
2004
235
2159
109
177
2159
82
1
2159
0.5
2005
320
2263
141
233
2263
103
3
2263
2
2006
311
2398
130
185
2398
77
3
2398
1
2007
256
2805
91
194
2805
69
0.7
2805
0.3
|
Figure 7.4.12.1 Demersal elasmobranchs in the Bay of Biscay and Iberian Waters. Historical trends in landings of skates (Rajidae) in Divisions VIIIab, VIIId, VIIIc, and IXa. From ICES (2008). 2007 data are unavailable for Spain and preliminary for other nations. |
|
Figure 7.4.12.2 Demersal elasmobranchs in the Bay of Biscay and Iberian Waters. Historical trends in landings of lesser-spotted dogfish in Divisions VIIIab, VIIId, VIIIc, and IXa (From ICES, 2008). 2007 data are unavailable for Spain and preliminary for other nations. |
|
Figure 7.4.12.3 Demersal elasmobranchs in the Bay of Biscay and Iberian Waters. Changes in Rajidae spp. (Raja clavata) biomass indices in ICES Divisions IXa and VIIIc, from the Northern Spanish Coast Survey time-series (1983–2007). Boxes mark parametric standard errors of the stratified abundance index. Lines mark bootstrap confidence intervals ( = 0.80, bootstrap iterations = 1000). |
|
Figure 7.4.12.4 Demersal elasmobranchs in the Bay of Biscay and Iberian Waters. Changes in lesser spotted dogfish (Scyliorhinus canicula) biomass indices in ICES Divisions IXa and VIIIc, from the Northern Spanish Coast Survey time-series (1983–2007). Boxes mark parametric standard errors of the stratified abundance index. Lines mark bootstrap confidence intervals ( = 0.80, bootstrap iterations = 1000). |
Ref Point
No reference points have been defined.
Sci Advice
Single-stock exploitation boundaries
ICES advises that landings of demersal elasmobranchs in 2009 should not exceed recent average landings (2002–2006), treating skates and rays, and lesser-spotted dogfish separately. Species-specific landings data should be collected for the major skate species (including cuckoo ray, blonde ray, thornback ray, spotted ray, undulate ray, and smalleyed ray).
Skates and rays
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
Disc.
slip
.
ICES
Catch
Year
1996
No advice
no TAC
4.2
1997
No advice
no TAC
4.8
1998
No advice
no TAC
4.4
1999
No advice
no TAC
3.1
2000
No advice
no TAC
3.7
2001
No advice
no TAC
4.4
2002
No advice
no TAC
3.5
2003
No advice
no TAC
4.2
2004
No advice
no TAC
4.2
2005
No advice
no TAC
3.8
2006
No advice
no TAC
3.6
2007
No advice
no TAC
2.4 (2)
2008
No advice
no TAC
2009
landings not to exceed recent average (2002–2006) (3)
3.9
Weights in ‘000 t.
(1)EU only.
(2)Preliminary data.
(3)Given that landings of major species are recorded by species.
Lesser-spotted dogfish
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
Disc.
slip
.
ICES
Catch
Year
1996
No advice
no TAC
1.9
1997
No advice
no TAC
2.1
1998
No advice
no TAC
2.4
1999
No advice
no TAC
2.0
2000
No advice
no TAC
1.7
2001
No advice
no TAC
1.7
2002
No advice
no TAC
1.6
2003
No advice
no TAC
1.7
2004
No advice
no TAC
1.9
2005
No advice
no TAC
1.9
2006
No advice
no TAC
1.7
2007
No advice
no TAC
1.3 (2)
2008
No advice
no TAC
2009
landings not to exceed recent average (2002–2006) (3)
1.8
Weights in ‘000 t.
(1)EU only.
(2)Preliminary data.
(3)Given that landings of major species are recorded by species.
Management
Management unit: No
Objectives
None have been adopted.
An EC Action Plan on elasmobranchs is being considered in 2008.
Advice
Management considerations
Demersal elasmobranchs are landed as a bycatch in the demersal fisheries for teleosts. In the Bay of Biscay and Iberian waters they are not generally identified to species in the landings data. For example, several skate species are landed as “skates and rays”. In addition to species identification, market sampling is needed to support the scientific advice.
Since demersal elasmobranchs are a bycatch in mixed fisheries, a restrictive TAC may result in additional discards without necessarily reducing fishing mortality. The survival rate of discards is a relevant management consideration. For some species it is believed that survival rate is high (e.g. lesser-spotted dogfish), but for other species it is unknown.
Elasmobranchs are typically slow growing, having a high age-at-maturity and a low reproductive capacity. These aspects of the biology as well as the limited information on the stock status, indicate that a cautious approach to management should be considered, which could imply reducing landings compared to recent averages.
Generally it should be noted that since elasmobranch species are caught as a bycatch in demersal fisheries, they would benefit from a reduction in the overall demersal fishing effort.
Sources
ICES.2009.Report of the ICES Advisory Committee, 2009. ICES Advice, 2009.