Working Document presented to the Working Group on Elasmobranch Fishes ICES WGEF, - Lisbon 18-26 June 2012 ———————————————————————————————————

Results on main elasmobranch species captured during the 2001-2011 Porcupine Bank (NE Atlantic) bottom trawl surveys

S. Ruiz-Pico (1), F. Baldó (2), F. Velasco (1), O. Fernández-Zapico (1), C. Rodríguez-Cabello (1)

(1) Instituto Español de Oceanografía, Centro Oceanográfico de Santander P.O. Box 240, 39080 Santander, Spain (2) Instituto Español de Oceanografía, Centro Oceanográfico de Cádiz Puerto pesquero, Muelle de Levante s/n, 11006 Cádiz, Spain

Abstract This working document presents the results on nine of the most important elasmobranch species of the Porcupine bank Spanish surveys during the last decade (2001-2011). The species more abundant in these surveys in biomass terms were blackmouth catshark (Galeus melastomus), ( calcea), (Scymnodon ringens), velvet belly lantern shark ( spinax), lesser spotted dogfish (Scyliorhinus canicula) and bluntnose sixgill shark ( griseus); while sandy ray (Leucoraja circularis), cuckoo ray (Leucoraja naevus) and common skate (Dipturus spp. / Dipturus cf. flossada) were the more frequent Rajidae. Biomass, distribution and length ranges were analysed. Many of these species occupy mainly the deep areas covered in the survey, especially D. calcea and S. ringens.

Introduction The Porcupine Bank bottom trawl survey has been carried out annually since 2001 to provide data and information for the assessment of the commercial fish species in the area (ICES divisions VIIc and VIIk) (ICES, 2010, 2011a). The aim of this working document is to update the results (abundance indices, length frequency distributions and geographic distributions) on the most common elasmobranch species in Porcupine bottom trawl surveys following the results presented previously (Velasco et al. , 2010; Fernández-Zapico et al ., 2011). The species analysed are: blackmouth catshark ( Galeus melastomus ), birdbeak dogfish ( Deania calcea ), Knifetooth dogfish ( Scymnodon ringens ), velvet belly lantern shark ( Etmopterus spinax ), lesser spotted dogfish ( Scyliorhinus canicula ), bluntnose sixgill shark (Hexanchus griseus ), sandy ray ( Leucoraja circularis ), cuckoo ray ( Leucoraja naevus ), and common skate ( Dipturus spp . / Dipturus cf. flossada ).

Material and methods The area covered in the Spanish Ground Fish Survey on the Porcupine bank (SPPGFS) (Figure 1) extends from longitude 12° W to 15° W and from latitude 51° N to 54° N, covering depths between 180 and 800 m. The cruises are carried out annually in

1 September/October on board R/V “Vizconde de Eza”, a stern trawler of 53 m and 1800 Kw. The sampling design used in this survey is random stratified (Velasco and Serrano, 2003), with two geographical sectors (North and South) and three depth strata (> 300 m, 300 – 450 m and 450 - 800 m) (Figure 2). Hauls allocation is proportional to the strata area following a buffered random sampling procedure (as proposed by Kingsley et al ., 2004) to avoid the selection of adjacent 5×5 nm rectangles. More details on the survey design and methodology are presented in ICES (2010, 2011a). The distribution of the most common elasmobranch fish species is analysed in biomass and number terms for the eleven years of the overall time series and the length distribution. Two different methods were used to estimate abundance variability: (i) the parametric standard error derived from the random stratified sampling (Grosslein and Laurec, 1982), and (ii) a non-parametric bootstrap procedure implemented in R (R Development Core Team, 2008): re-sampling randomly with replacement stations within each stratum and maintaining the sampling intensity, and using 80% bootstrap confidence intervals from the 0.1 and 0.9 quantiles of the resultant distribution of bootstrap replicates (Efron and Tibshirani, 1993).

Results and discussion In 2011, 80 standard hauls and 5 additional hauls were carried out (Figure 2). Mean total catch per haul was 437.9 ± 32.42 kg. Fishes represented about 93% of the total catch and elasmobranchs made up ca. 4% of the total fish catch. The shark species with larger stratified biomass indices were blackmouth catshark (Galeus melastomus ), then birdbeak dogfish ( Deania calcea ) and lastly knifetooth dogfish ( Scymnodon ringens ), velvet belly lantern shark ( Etmopterus spinax ), lesser spotted dogfish ( Scyliorhinus canicula ) and bluntnose sixgill shark ( Hexanchus griseus ). The skate species with larger stratified biomass were sandy ray ( Leucoraja circularis ), then cuckoo ray ( Leucoraja naevus ) and common skate ( Dipturus spp). D. calcea and S. ringens showed deeper distribution than G. melastomus , E. spinax and S. canicula . On the other hand , L. naevus and Dipturus spp. was mainly found around the central mound of Porcupine bank while L. circularis showed a wider distribution. Regarding the length distribution, the shark species which showed wider range sizes were D. calcea, S. ringens and H. griseus and regarding the skates, L. naevus showed narrower size range than L. circularis .

Blackmouth catshark (Galeus melastomus ) This species represented about 56% of the elasmobranchs mean stratified biomass caught and about 73% of the elasmobranchs mean stratified abundance. The stratified biomass and abundance trend were similar. Although a lower capture was found in 2011, G. melastomus showed a steady increasing trend during the last four years after the remarkable drop in 2006 (Figure 3). G. melastomus was mainly found in the southern part of the survey area. Higher biomass was found in the deepest South sector between 450 and 800 m (Figure 4). Catshark length size in the last survey ranged from 11 cm to 77 cm. In 2011, the sizes were similar to the mean values of the series with a marked mode around 60 cm (Figure 5).

2 Birdbeak dogfish (Deania calcea ) This species represented a small percentage of the elasmobranchs mean stratified biomass caught (13%) and of the stratified abundance caught (3%). Although higher capture was found in 2011 (Figure 6), the stratified biomass and abundance was quite variable in the overall time series may be due to the fact that this species dwells in the depth limits covered in this survey as pointed out in Velasco et al. (2010). It was found between 490 m and 800 m in the overall time series and the highest biomass was in the westernmost area, resembling the 2006 and 2010 pattern (Figure 7). Far fewer small specimens were found in 2011. Although the length size of this last survey ranged from 39 cm to 111 cm, it has been the year with less individuals smaller than 65 cm in the time series, with an abundance of only 0.02 individuals per haul (Figure 9). In 2011, one marked mode was evident around 84 cm and a smaller one around 100 cm, similar to the modes found years before (Figure 8). Knifetooth dogfish ( Scymnodon ringens ) This species represented a small percentage of the elasmobranchs mean stratified abundance caught (8%) and of the stratified biomass caught (2%). The stratified biomass showed a rise after the drop in 2005, while the stratified abundance have remained fairly stable in the last six years (Figure 10). S. ringens appears in the muddy slopes of the Porcupine Seabight southeast of the survey area, as shown in Velasco et al. (2010). The last survey showed as well this pattern, but high biomass was also found in the westernmost area, that before were found in just one haul in 2007 and 2008 (Figure 11). It was found between 465 m and 800 m in the overall time series. The S. ringens sizes ranged between 32 cm and 134 cm in 2011, although a marked mode was found around 73 cm (Figure 12). That last survey showed the largest size range in the eleven years of the series. Velvet belly lantern shark ( Etmopterus spinax ) E. spinax just represented about 7% of the elasmobranchs mean stratified biomass caught while it showed about 17% of the stratified abundance caught. The stratified biomass and abundance were low in the overall time series, although a marked peak was found in 2006 and another two smaller ones in 2003 and 2009. The capture in 2011 was markedly low (Figure 13). No clear pattern was found in the geographical distribution of E. spinax. Higher biomass were found in the eastern part of the central mound of Porcupine Bank around 350 m, but was also found frequently close to the 450 m boundary in the western and Northern area and between 450 m and 800 m in the southern part of the survey area (Figure 14). E. spinax showed the narrowest length range of the elasmobranchs reported in these surveys. Specimens ranged from 10 cm to 52 cm in 2011 and no clear mode was found. Lesser spotted dogfish ( Scyliorhinus canicula ) This species represented a small percentage of the elasmobranchs mean stratified abundance caught (5%) and biomass caught (3%). The biomass and abundance of this species have shown an increasing trend in the last years. In 2011 this trend was again confirmed with a higher biomass value around 1.8 Kg per haul (Figure 16). In 2011, geographic distribution of biomass was also clearly related to the Irish shelf, as reported before (Velasco et al. , 2010; Fernández-Zapico et al ., 2011) but also higher capture was shown in the northwest of the bank around 300 m (Figure 17).

3 The minimum length size of S. canicula in 2011 was 20 cm and the maximum 81 cm. Some individuals smaller than 40 cm were shown in the last survey in contrast with the lack of sizes smaller than 40 cm in the previous two years. Although individuals smaller than 55 cm are relatively scarce in this area, peaks in biomass and abundance related with small sizes, were reported in 2007 and 2008 (Velasco et al. , 2010). The higher biomass and abundance in 2011 may also correspond to the apparition of these small sizes (Figure 18). Bluntnose sixgill shark ( Hexanchus griseus ) This species represented a small percentage of the elasmobranchs mean stratified abundance caught (4%) and of the stratified biomass caught (0.4%). The stratified biomass and abundance was quite steady over the previous seven years between 0.5 and 1 Kg per haul, as the capture around 0.9 Kg per haul during the last survey (Figure 19). H. griseus extended throughout the Porcupine area with no clear pattern in the geographical distribution, but in 2011 although no catches were found in the southernmost tip of the area, the species was more spreaded along the area (Figure 20). H. griseus length distribution ranged from 64 cm to 139 cm in 2011(Figure 21). Sandy ray ( Leucoraja circularis ) and Cuckoo ray ( Leucoraja naevus ) These two species of rays represented small percentages of the elasmobranchs mean stratified biomass caught (around 2%) and abundance caught (around 1%) in the time series. The increasing trend of biomass and abundance of L. circularis in the last years were confirmed with the higher value in 2011 (around 0.6 Kg per haul) in the same way as the low biomass and abundance of L. circularis in 2011 (around 0.2 Kg per haul) confirmed the decreasing trend in the last years (Figure 22; Figure 25). In 2011, L. circularis extended throughout the west Porcupine area, with higher biomass in the northwest than previous years, while L. naevus was mainly around the central mound of Porcupine bank with lesser biomass located in the south than previous surveys (Figure 23; Figure 26). L. circularis sizes ranged between 18 cm and 104 cm in 2011, while L. naevus showed a narrower length range from 37 cm to 60 cm. Some small specimens of L. circularis were shown during the last survey despite the fact that individuals smaller than 32 cm are very scarce, whereas no specimen of L. naevus smaller than 37 cm appeared in contrast with previous years (Figure 24; Figure 27). Common skate (Dipturus spp.) The common skate Dipturus batis, has been recently separated in two species, Dipturus cf. flossada and Dipturus cf. intermedia (Iglésias et al, 2009) . Up to date, the information these species was not split for the Porcupine survey, and it was identified as Dipturus batis complex. A special request is addressed to ICES for advice on an individual species basis for the two components of the common skate. The results previously reported in the Porcupine area as Dipturus batis are now merged into Dipturus spp. Meanwhile in 2011, a careful identification was made in order to split the components of the D.batis complex, and all the individuals found were identified as Dipturus cf. flossada , therefore data for this species in the that last survey is presented below, together with the trends of Dipturus spp. in the overall time series. Dipturus spp. only represented about 1% of the elasmobranchs mean stratified biomass caught and about 0.2% of the stratified abundance caught. The WGCSE (Working Group for the Celtic Seas Ecoregion) (ICES, 2011b) noted that this species has declined in inshore areas of northern Europe, but the common skate in the Porcupine area showed a steady pattern in the overall time series, although the abundances are small,

4 especially in terms of number, given that the biomass is greatly influence by the appearance of big skates. Nevertheless, the stratified biomass in 2011, which correspond with Dipturus cf. flossada , decreased after the remarkable peak in the previous year, although the stratified abundance remained at stable values around 0.05 kg per haul during the last four years (Figure 28). Dipturus spp. was mainly found around the mound in the centre of the bank (Figure 29) and it showed a wide bathymetric range between 190 m and 740 m in the overall time series. In 2011, Dipturus cf. flossada also showed a similar distribution (Figure 30) and was found between 230 m and 320 m. Regarding the length distribution, Dipturus spp. captured in the time series ranged from 20 cm to 177 cm, while Dipturus cf. flossada captured in 2011 showed a narrower range from 49 cm to 74 cm (Figure 31). Other elasmobranch species Other species with less abundance have been previously reported in the area (Velasco et al. , 2010; Fernández-Zapico et al ., 2011), namely coelolepi, Centroscymnus crepidater , squamosus, Dalatias licha , Galeus murinus, Galeorhinus galeus , Raja clavata , Leucoraja fullonica , Dipturus nidarosiensis and Rajella fyllae. However, in 2011 only D. nidarosiensis and R. clavata were caught.

Acknowledgements We would like to thank R/V Vizconde de Eza crews and the scientific teams from IEO, Marine Institute and AZTI that made the Porcupine Surveys possible.

References

Efron and Tibshirani, 1993. An Introduction to the Bootstrap. Chapman & Hall 436 pp.

Fernández-Zapico O., Velasco F., Baldó F., Ruiz-Pico S., and Blanco M., 2011. Results on main elasmobranch species captured during the 2001-2010 Porcupine Bank (NE Atlantic) bottom trawl surveys. Working Document presented to the Working Group on Elasmobranch Fishes ICES WGEF, 22-24 June 2011. 22 pp.

Grosslein M.D. and Laurec A., 1982. Bottom trawl survey design, operation and analysis. CECAF/ECAF Series 81/22. 22 pp.ICES, 2010. Manual for the International Bottom Trawl Surveys in the Western and Southern Areas. Addendum 2 to the Report of the International Bottom Trawl Surveys Working Group. Lisbon, Portugal, 22-26 March 2010. ICES CM 2010/SSGESST:06. 58 pp.

ICES, 2011a. Report of the International Bottom Trawl Survey Working Group (IBTSWG), 28 March - 1 April 2011, Copenhage, Denmark. ICES CM 2011/SSGESST: 06. 237 pp.

ICES, 2011b. Report of the Working Group for Celtic Seas Ecoregion (WGCSE), 11–19 May 2011, Copenhagen, Denmark. ICES CM 2011/ACOM:12. 1573 pp.

ICES, 2010. Manual for the International Bottom Trawl Surveys in the Western and Southern Areas Revision III Agreed during the meeting of the International Bottom Trawl Survey Working Group 22–26 March 2010, Lisbon. Addendum 2: ICES CM 2010/SSGESST:06. 58 pp.

5 Iglésias, S.P., Toulhoat, L., Sellos, D.Y., 2009. Taxonomic confusion and market mislabelling of threatened skates: important consequences for their conservation status. Aquatic Conserv: Mar. Freshw. Ecosyst.

Kingsley, M.C.S.; Kanneworff, P. and Carlsson, D.M., 2004. Buffered random sampling: a sequential inhibited spatial point process applied to sampling in a trawl survey for northern shrimp Pandalus borealis in West Greenland waters. ICES Journal of Marine Science, 61: 12-24.

R Development Core Team. 2008. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3-900051-07-0, URL http://www.R-project.org.

Velasco, F., and Serrano, A., 2003. Distribution patterns of bottom trawl faunal assemblages in Porcupine bank: Implications for Porcupine surveys stratification design. Working Document presented to IBTSWG 2003. 19 pp.

Velasco F., Blanco M. Baldó F., 2010. Results on main elasmobranch species captured during the 2001-2009 Porcupine Bank (NE Atlantic) bottom trawl surveys. Working Document presented to the Working Group on Elasmobranch Fishes ICES WGEF, Açores - 22-29 June 2010. 26 pp.

6 Figures

15 10 5

60 60

Hatton Rosemary bank bank George Bligh bank

s e

id r b 58 e 58

k H n r e a t b u l VIa VIb l O a k c o R

56 56

54 54

VIIc VIIb VIIa Porcupine bank

52 52

VIIg VIIf

Porcupine Seabight VIIk VIIj 50 Celtic Sea 50

Grand VIIe Sole VIIh

48 48 15 10 5 Figure 1. North eastern Atlantic showing the Porcupine bank, Porcupine Seabight, and ICES divisions.

15º 14º 13º 12º 11º 10º 9º

54º 54º

Galway

53º 53º

IRELAND 52º 52º

51º Valid tows 51º Extra tows

15º 14º 13º 12º 11º 10º 9º

Figure 2. Stratification design and hauls in 2011 Porcupine surveys; Straight lines show geographical sectors (North and South) and the isobaths delimit the three depth strata (> 300 m, 300 – 450 m and 450 - 800 m).

7

Galeus melastomus Biomass

25 90 % 1 − 20 15 10 % 10 kg · haul 5 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number 80 1

− 60 90 % 40

10 %

Ind. haul 20

0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 3. Changes in blackmouth catshark ( Galeus melastomus ) biomass index and abundance during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified biomass index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations = 1000).

Galeus melastomus

2001 2002 2003 2004 2005 2006

300 kg 300 kg 300 kg 300 kg 300 kg 300 kg 51 52 53 54

2007 2008 2009 2010 2011

300 kg 300 kg 300 kg 300 kg 300 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 4. Geographic distribution of blackmouth catshark ( G. melastomus ) catches (kg·haul -1) during Porcupine survey time series (2001- 2011).

8 2011 Mean 2001-2011 1 1 − − Ind. haul Ind. haul 0.0 0.5 1.0 1.5 2.0 0.0 0.5 1.0 1.5 2.0 1 5 9 14 20 26 32 38 44 50 56 62 68 74 80 1 5 9 14 20 26 32 38 44 50 56 62 68 74 80 Length (cm) Length (cm) Figure 5. Stratified length distributions of blackmouth catshark ( G. melastomus ) in 2011 Porcupine survey, and mean values during Porcupine survey time series (2001-2011).

Deania calcea Biomass 12 10 1 − 8 90 % 6 4

kg · haul 10 % 2 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number 5

1 4 − 3 90 % 2

Ind. haul 1 10 %

0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 6. Changes in birdbeak dogfish ( Deania calcea ) biomass index (kg·haul-1) during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified biomass index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations =1000).

9 Deania calcea

2001 2002 2003 2004 2005 2006

300 kg 300 kg 300 kg 300 kg 300 kg 300 kg 51 52 53 54

2007 2008 2009 2010 2011

300 kg 300 kg 300 kg 300 kg 300 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 7. Geographic distribution of birdbeak dogfish ( D. calcea ) catches (kg·haul -1) during Porcupine survey time series (2001- 2011).

2011 Mean 2001-2011 1 1 − − Ind. haul Ind. haul

0.001 7 0.0514 23 32 0.10 41 50 0.15 59 68 0.20 77 86 95 105 116 0.001 7 0.0514 23 32 0.10 41 50 0.15 59 68 0.20 77 86 95 105 116 Length (cm) Length (cm) Figure 8. Stratified length distributions of Deania calcea in 2011 Porcupine survey, and mean values during Porcupine survey time series (2001-2011).

10 Deania calcea 1-65 cm 1 − Ind. haul haul Ind. 0.00 0.05 0.10 0.15 0.20 0.25 0.30

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Length (cm)

Figure 9. Abundance of Deania calcea smaller than 65 cm during Porcupine survey time series (2001- 2011).

Scymnodon ringens Biomass

5

1 90 %

− 4 3 2 10 % kg · haul 1 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number 4 1

− 3

2

90 % 1 Ind. haul 10 % 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 10. Changes in knifetooth dogfish ( Scymnodom ringens ) biomass index (kg·haul-1) during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified biomass index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations = 1000).

11 Scymnodon ringens

2001 2002 2003 2004 2005 2006

80 kg 80 kg 80 kg 80 kg 80 kg 80 kg 51 52 53 54

2007 2008 2009 2010 2011

80 kg 80 kg 80 kg 80 kg 80 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 11. Geographic distribution of knifetooth dogfish ( S. ringens ) catches (kg·haul -1) during Porcupine survey time series (2001- 2011).

2011 Mean 2001-2011 1 1 − − Ind. haul Ind. haul 0.00 0.02 0.04 0.06 0.08 0.00 0.02 0.04 0.06 0.08 1 8 17 27 37 47 57 67 77 87 97 109 122 135 1 8 17 27 37 47 57 67 77 87 97 109 122 135 Length (cm) Length (cm) Figure 12. Stratified length distributions of knifetooth dogfish ( S. ringens ) in 2010 in Porcupine survey, and Mean values during Porcupine survey time series (2001-2010).

12 Etmopterus spinax Biomass 10

8 1 − 6 4 kg · haul 2 90 % 0 10 % 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number 40 1 − 30

20

Ind. haul 10 90 % 10 % 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 13. Changes in velvet belly ( Etmopterus spinax ) biomass index (kg·haul -1) during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified biomass index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations =1000).

Etmopterus spinax

2001 2002 2003 2004 2005 2006

300 kg 300 kg 300 kg 300 kg 300 kg 300 kg 51 52 53 54

2007 2008 2009 2010 2011

300 kg 300 kg 300 kg 300 kg 300 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 14. Geographic distribution of velvet belly ( E. spinax ) catches (kg·haul -1) during Porcupine surveys time series (2001- 2011).

13 2011 Mean 2001-2011 1 1 − − Ind. haul Ind. haul 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 1 5 9 14 19 24 29 34 39 44 49 54 59 64 69 1 5 9 14 19 24 29 34 39 44 49 54 59 64 69 Length (cm) Length (cm) Figure 15. Stratified length distributions of velvet belly ( E. spinax ) in 2011 Porcupine survey, and mean values during Porcupine survey time series (2001-2011).

Scyliorhinus canicula Biomass

3.0 90 %

1 2.5 − 2.0 1.5 1.0 10 % kg · haul 0.5 0.0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number

5 1 − 4 3 90 % 2

Ind. haul 1 10 % 0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 16 . Changes in lesser-spotted dogfish ( Scyliorhinus canicula ) biomass index (kg·haul -1) during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified biomass index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations = 1000).

14 Scyliorhinus canicula

2001 2002 2003 2004 2005 2006

60 kg 60 kg 60 kg 60 kg 60 kg 60 kg 51 52 53 54

2007 2008 2009 2010 2011

60 kg 60 kg 60 kg 60 kg 60 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 17. Geographic distribution of lesser spotted dogfish (S. canicula ) catches (kg·haul-1) in Porcupine survey time series (2001-2011).

2011 Mean 2001-2011 1 1 − − Ind. haul Ind. haul 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 1 6 12 19 26 33 40 47 54 61 68 75 82 89 1 6 12 19 26 33 40 47 54 61 68 75 82 89 Length (cm) Length (cm) Figure 18. Stratified length distributions of lesser spotted dogfish ( S. canicula ) in 2011 in Porcupine survey, and mean values during Porcupine survey time series (2001-2011).

15 Hexanchus griseus Biomass 3.0 2.5 1 − 2.0 1.5 90 % 1.0 kg · haul 0.5 10 % 0.0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number 0.5

1 0.4 − 0.3 90 % 0.2 10 % Ind. haul 0.1

0.0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 19. Changes in bluntnose sixgill shark (Hexanchus griseus ) biomass index (kg•haul-1) during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified biomass index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations = 1000).

Hexanchus griseus

2001 2002 2003 2004 2005 2006

40 kg 40 kg 40 kg 40 kg 40 kg 40 kg 51 52 53 54

2007 2008 2009 2010 2011

40 kg 40 kg 40 kg 40 kg 40 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 20. Geographic distribution of bluntnose sixgill shark ( H. griseus ) catches (ind · haul -1) in Porcupine surveys (2001-2011).

16

2011 Mean 2001-2011 1 1 − − Ind. haul Ind. haul 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.02 0.03 0.04 0.05 1 9 18 29 40 51 62 73 84 95 107 121 135 149 1 9 18 29 40 51 62 73 84 95 107 121 135 149 Length (cm) Length (cm) Figure 21. Stratified length distributions of bluntnose sixgill shark ( H. griseus ) in 2011 Porcupine survey and mean values during Porcupine survey time series (2001-2011).

Leucoraja circularis Biomass 2.0

1 1.5 −

1.0 90 %

kg · haul 0.5 10 % 0.0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number 0.8 1

− 0.6 90 % 0.4

0.2 10 % Ind. haul

0.0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 22. Changes in sandy ray (Leucoraja circularis ) biomass index (kg·haul -1) during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified biomass index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations =1000).

17 Leucoraja circularis

2001 2002 2003 2004 2005 2006

40 kg 40 kg 40 kg 40 kg 40 kg 40 kg 51 52 53 54

2007 2008 2009 2010 2011

40 kg 40 kg 40 kg 40 kg 40 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 23. Geographic distribution of sandy ray (L. circularis ) catches (kg·haul -1) in Porcupine survey time series (2001-2011).

2011 Mean 2001-2011 1 1 − − Ind. haul Ind. haul

0.0001 0.005 7 0.010 15 0.015 24 0.020 33 0.025 42 0.030 51 60 69 78 87 96 106 117 0.0001 0.005 7 0.010 15 0.015 24 0.020 33 0.025 42 0.030 51 60 69 78 87 96 106 117 Length (cm) Length (cm) Figure 24. Stratified length distributions of sandy ray ( L. circularis ) in 2011 Porcupine survey, and mean values during Porcupine survey time series (2001-2011).

18 Leucoraja naevus Biomass 1.5 1 − 1.0

0.5 kg · haul 90 % 10 % 0.0 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number 2.5

1 2.0 − 1.5

1.0

Ind. haul 0.5 90 % 0.0 10 % 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 25. Changes in Cuckoo ray (Leucoraja naevus ) biomass index (kg·haul -1) during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified biomass index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations = 1000).

Leucoraja naevus

2001 2002 2003 2004 2005 2006

20 kg 20 kg 20 kg 20 kg 20 kg 20 kg 51 52 53 54

2007 2008 2009 2010 2011

20 kg 20 kg 20 kg 20 kg 20 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 26. Geographic distribution of cuckoo ray (L. naevus ) catches (ind · haul -1) during Porcupine survey time series (2001- 2011).

19 2011 Mean 2001-2011 1 1 − − Ind. haul Ind. haul 0.00 0.01 0.02 0.03 0.04 0.05 0.00 0.01 0.02 0.03 0.04 0.05 1 5 9 14 19 24 29 34 39 44 49 54 59 64 69 1 5 9 14 19 24 29 34 39 44 49 54 59 64 69 Length (cm) Length (cm) Figure 27. Stratified length distributions of cuckoo ray ( L. naevus ) in 2011 Porcupine survey, and mean values during Porcupine survey time series (2001-2011).

Dipturus spp. Biomass

1.5 1 − 1.0

0.5 kg · haul

90 % 0.0 10 % 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year

Number 0.5

1 0.4 − 0.3

0.2

Ind. haul 0.1 90 %

0.0 10 % 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 Year Figure 28. Changes in common skate ( Dipturus spp.) biomass index (kg.haul -1) during Porcupine survey time series (2001-2011). Boxes mark parametric standard error of the stratified index. Lines mark bootstrap confidence intervals (a = 0.80, bootstrap iterations = 1000).

20 Dipturus spp.

2001 2002 2003 2004 2005

30 kg 30 kg 30 kg 30 kg 30 kg 51 52 53 54 2006 2007 2008 2009 2010

30 kg 30 kg 30 kg 30 kg 30 kg 51 52 53 54

15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11 15 14 13 12 11

Figure 29. Geographic distribution of common skate ( Dipturus spp.) catches (ind. · haul-1) in Porcupine survey time series (2001-2010).

Dipturus flossada

2011

3 kg 51 52 53 54

15 14 13 12 11

Figure 30. Geographic distribution of common skate ( Dipturus cf. flossada ) catches (ind. · haul-1) in 2011 Porcupine survey.

21 2011 Mean 2001-2010 1 1 − − Ind. haul Ind. haul

0.000 0.002 0.0041 0.006 5 0.008 9 0.010 0.012 14 0.014 20 26 32 38 44 50 56 62 68 74 80 0.000 0.0021 0.004 0.006 12 0.008 0.010 25 0.012 0.014 38 51 64 77 90 105 122 139 156 173 Length (cm) Length (cm)

Figure 31. Stratified length distributions of Dipturus cf. flossada in 2011 Porcupine survey, and mean values of Diptururs spp. during Porcupine survey time series (2001-2010).

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