Assessing Discard Mortality of Commercially Caught Skates (Rajidae) – Validation of Experimental Results

Assessing discard mortality of commercially caught skates (Rajidae) – validation of experimental results

(MB5202)

Final Report

March 2012

Project Title: Assessing discard mortality of commercially caught skates (Rajidae) – validation of experimental results

Project Code: MB5202 Marine Biodiversity R&D Programme

Defra Contract Manager: Carole Kelly

Funded by: Department for Environment Food and Rural Affairs (Defra) Marine and Fisheries Science Unit Marine Directorate Nobel House, 17 Smith Square London SW1P 3JR

Authorship:

J. R. Ellis [email protected]

S. R. McCully [email protected]

J. F. Silva [email protected]

T.L. Catchpole [email protected]

D. Goldsmith [email protected]

V. Bendall [email protected]

G. Burt [email protected]

Centre for Environment, Fisheries and Aquaculture Science (Cefas) Pakefield Road Lowestoft. Suffolk NR33 0HT www.cefas.defra.gov.uk

Disclaimer: The content of this report does not necessarily reflect the views of Defra, nor is Defra liable for the accuracy of the information provided, nor is Defra responsible for any use of the reports content.

Front cover images: Jim Elis (Cefas).

Executive Summary

Approximately 14 species of skate (Rajidae) occur on the continental shelf of the United Kingdom. These species vary in their commercial importance and also their susceptibilities to over-exploitation. Stocks of some skate species are considered healthy, whereas some of the larger-bodied species have declined or disappeared from parts of their former range. The assessment and management advice for skates has been hampered by a lack of species- specific data from commercial fisheries. A summary of the skate fauna of the British Isles, a historical perspective of their fisheries, long-term changes in skate stocks and in the recent implementation of management measures for skates are summarised in Section 1 of the report.

Since 2008 there has been progress in collecting landings data for individual species. The proportion of skate landings reported to species level for UK (English and Welsh) fleets has increased from ca. 42% (2008) to ca. 92% (2010). The quality of these data was appraised by comparing the species composition of landings (by area and gear) with the estimated species composition of retained skates from discard observer data. Although there were some inconsistencies, due to misidentifications, the general quality of official landings data appears to be coherent with other sources and is improving. Information from discard observer programmes indicted that skates <30 cm in length were usually discarded, with about half the skates discarded at a length of ca. 50 cm. Skates larger than 60 cm were typically retained. More detailed information on the species composition of skates captured by UK fleets, discard/ retention patterns and discarding rates are provided in Section 2 of the report.

Discarding is an increasingly topical issue for fisheries managers. Quotas for skate may now be restrictive in some fisheries, small skates are often discarded, some skates are not landed and recent regulations have listed some species (e.g. common skate and undulate ray) as prohibited species that must be returned to the sea. Given these scenarios, further studies to better evaluate the potential survivorship of skates in various fisheries were undertaken. About 98% of the skates survived capture in inshore gillnet fisheries with short (24 hour) soak times. This decreased to about 88% for soak times of 43-48 hours. Future analyses of recapture data for the fish tagged in these studies are required to better gauge longer-term survival. About 50% of skates survived capture by beam trawl, and mortality was higher for smaller individuals. The field work undertaken for the project is described in Section 3.

The current perceptions of the stock status, as advised by the International Council for the Exploration of the Sea (ICES), is summarised (Section 4), with potential methods for identifying and prioritising skate stocks of concern given. More recent analyses of fishery- independent survey data indicate that catch rates of many of the main commercial skate stocks in English and Welsh waters are stable, though other species are poorly sampled in existing surveys.

Options for the improved fisheries management of skates are discussed in Section 5. Existing measures include a total allowable catch (set at the family-level), minimum landing sizes in some areas, and the prohibited species list. Other measures, such as spatial management and gear modifications, are discussed, and the development of more regional management plans could usefully be taken forward. To improve the assessment and management of skates, future research could usefully be targeted at biological investigations (e.g. the life history of data-limited species, stock units, habitat utilisation), commercial information (e.g. on-going quality assurance of catch data, commercial catch per unit effort), bycatch mitigation and options for improving fishery-independent surveys for those species not sampled effectively in existing surveys.

Contents Executive Summary ...... ii List of Tables ...... vi List of Figures ...... ix 1. Introduction ...... 1 1.1 Project background...... 1 1.2 The skate fauna of the British Isles...... 2 1.3 UK skate fisheries: A historical perspective ...... 6 1.4 Longer-term changes in skate populations ...... 7 1.5 Recent management of skate fisheries ...... 9 1.6 Aims and objectives ...... 11 1.7 Soliciting and collating representative views of the fishing industry ...... 11 1.8 Format of the report ...... 12 2. The skate species discarded in representative UK fisheries and data gaps in our knowledge of their discard survival ...... 13 2.1 Introduction ...... 13 2.2 Materials and methods ...... 14 2.2.1 Landings data ...... 14 2.2.2 Observer data ...... 15 2.2.3 Species identification ...... 15 2.2.4 Conversion of length to weight ...... 15 2.2.5 Data analysis ...... 15 2.3 Appraisal of recent species-specific landings data ...... 16 2.3.1 Reported landings from UK-registered vessels ...... 16 2.3.2 Irish Sea ...... 20 2.3.3 Bristol Channel ...... 21 2.3.4 Celtic Sea and Western English Channel ...... 21 2.3.5 Southern North Sea and Eastern English Channel ...... 22 2.3.6 Northern and Central North Sea ...... 22 2.4 Discard-retention patterns ...... 29 2.5 Discarding rates: A broadscale analysis ...... 33 2.6 Discards rates: Estimating levels of discarding ...... 35 2.7 Discussion ...... 44 2.7.1 Requirements for species-specific landings ...... 44 2.7.2 Comparison of landings data and observer data...... 45 2.7.3 Data quality ...... 45 2.7.4 Prohibited species ...... 47

iii

2.7.5 Discard-retention patterns ...... 48 3. Skate discarding and survival: Recent field investigations ...... 49 3.1 Introduction ...... 49 3.2 Inshore gillnet studies ...... 52 3.3 Offshore trammel and tangle net studies ...... 58 3.4 Longline studies ...... 63 3.5 Otter trawl Studies ...... 66 3.6 Beam trawl studies ...... 71 3.7 Tag returns and validation of longer-term survival ...... 74 3.8 Discard survival: The perception of commercial fishers ...... 77 4. Current stock status of UK skates: Potential fisheries-induced mortality on skate populations and assessing the risks to stock sustainability of continuing with current fishing practices ...... 78 4.1 Introduction ...... 78 4.2 Overview of current ICES assessments and advice for skates ...... 79 4.3 Prioritising species and stocks of concern ...... 82 4.3.1 Ranking management importance of skate species ...... 82 4.3.2 Ecological Risk Assessments ...... 84 4.4 Survey trends for skates in UK waters ...... 85 4.5 Stock status: The perception of commercial fishers ...... 90 4.6 Potential fisheries induced mortality ...... 91 5. Options for improved fisheries management of skates ...... 92 5.1 Introduction ...... 92 5.2 Total allowable catch and quotas ...... 93 5.3 Size restrictions ...... 93 5.4 Prohibited species lists ...... 94 5.5 Spatial management ...... 95 5.6 Gear modifications...... 96 5.7 Implications of reforms in the common fisheries policy ...... 97 5.8 Development of regional management plan ...... 98 5.9 Management measures for elasmobranchs: The perception of commercial fishers ...... 98 5.10 Future research needs ...... 99 6. References ...... 101

Annexes

Annex I: List of acronyms Annex II: Questionnaire circulated to gain fishing industry views Annex III: Organisations to which the questionnaire was sent Annex IV: Comments from commercial fishermen Annex V: Discard rates of skates and rays in various fisheries

List of Tables

Table 1.1: Taxonomic list of skates (Rajidae) occurring around the British Isles, 4 including adjacent deep-water habitats in the North-east Atlantic

Table 1.2: Introduction of management measures for skates and rays, including 10 Total Allowable Catches (TAC, tonnes) for various parts of the ICES area

Table 2.1: Reported UK landings of skates (Rajidae) for the years 2007–2010 18

Table 2.2: Reported landings (t) of skate species by UK (English and Welsh) fleets 19 (2008–2010)

Table 2.3: Observed fisheries with discarded/retained skates by gear and area for 20 the main UK fisheries for the years 2008–2010

Table 2.4: Species composition of skates in UK fisheries operating in the Irish Sea 23

Table 2.5: Species composition of skates in UK fisheries operating in the Bristol 24 Channel

Table 2.6: Species composition of skates in UK fisheries operating in the Celtic 25 Sea

Table 2.7: Species composition of skates in UK fisheries operating in the western 26 English Channel

Table 2.8: Species composition of skates in UK fisheries operating in the southern 27 North Sea and eastern English Channel

Table 2.9: Species composition of skates in UK fisheries operating in the southern 28 North Sea and eastern English Channel (longline), and central and northern North Sea (beam and otter trawl)

Table 2.10: Categories of gear type used in estimating quantities of discards, and 33 fishing grounds examined

Table 2.11: Estimated average discard rates (averaged across years and areas) of 34 skates for the main gear categories for which discard data were available

Table 2.12: Proportion of discarded and retained skates in Irish Sea fisheries using 36 (a) otter trawl and (b) Nephrops trawl (2008–2010)

Table 2.13: Proportion of discarded and retained skates in western English 37 Channel fisheries using (a) beam trawl, (b) otter trawl and (c) gillnet (2008–2010)

Table 2.14: Proportion of discarded and retained skates in Bristol Channel fisheries 38 using (a) beam trawl, (b) otter trawl and (c) gillnet (2008–2010)

Table 2.15: Proportion of discarded and retained skates in Celtic Sea fisheries 39 using (a) beam trawl, (b) otter trawl and (c) gillnet (2008–2010)

Table 2.16: Proportion of discarded and retained skates in southern North Sea and 40 eastern English Channel fisheries using (a) beam trawl, (b) otter trawl and (c) gillnet (2008–2010)

Table 2.17: Estimated discards of Leucoraja naevus for the reported landings by 41 gear and area (2008-2010)

Table 2.18: Estimated discards of Raja clavata for the reported landings by gear 41 and area (2008-2010)

Table 2.19: Estimated discards of Raja brachyura for the reported landings by gear 42 and area (2008-2010)

Table 2.20: Estimated discards of Raja microocellata for the reported landings by 42 gear and area (2008-2010)

Table 2.21: Estimated discards of Raja montagui for the reported landings by gear 43 and area (2008-2010)

Table 3.1: Summary of field work undertaken during the project MB5202 51

Table 3.2: Species composition, sex ratio and length distributions of all batoids 55 caught whilst gillnetting on the FV Angelle Marie (May 2010)

Table 3.3: Species composition, sex ratio and length distributions of all batoids 56 caught whilst gillnetting on the FV Angelle Marie (Feb/March 2011)

Table 3.4: Species composition, sex ratio and length distributions of all batoids 57 caught whilst gillnetting on the FV Angelle Marie (March 2011)

Table 3.5: Species composition, sex ratio and length distributions of Dipturus batis- 61 complex caught in trammel and tangle nets

Table 3.6: Health state of Dipturus batis-complex following capture in trammel and 61 tangle nets

Table 3.7: Species composition (batoids only), sex ratio and length range of 65 elasmobranchs (excluding lesser-spotted dogfish) caught whilst longlining on the FV Nicola May

vii

Table 3.8: Numbers of skate and ray caught (by species), giving species 69 composition of commercial skates (by numbers), sex ratio and length ranges caught whilst otter trawling around the Channel Islands

Table 3.9: Species composition (% numbers) of skates in 14 tows conducted 69 around Guernsey

Table 3.10: Numbers of elasmobranch (n=356) tagged and released 70

Table 3.11: Summary details of survival of skates held in survival tanks following 72 capture by beam trawl

Table 3.12: Summary details of elasmobranchs (n=228) tagged and released 72 during beam trawl studies

Table 3.13: Summary of elasmobranchs released and recaptured during the project 75 for commercial fishing vessels and research vessel

Table 4.1: Perception of stock status of skates (Rajidae) occurring around the 80 British Isles according to recent ICES Advice

Table 4.2: Taxonomic ordering of skates listing the information used to rank the 83 species of concern according to maximum length, IUCN listing, commercial landings and ICES’ perception of the main stocks

Table 4.3: Scoring system for ranking UK skates according to four criteria (total 84 length, IUCN listing, quantities in reported landings and ICES assessment

Table 4.4: Perception of the current status of five skate species and four species of 90 dogfish by commercial fishers

viii

List of Figures

Figure 1.1: Main skate species occurring on the continental shelf of the United 5 Kingdom

Figure 1.2: UK landings of skates and rays (Rajidae) during the period 1903–2008 6

Figure 2.1: Spatial distribution of UK commercial landings of skates (Rajidae) 17

Figure 2.2: Cumulative size frequency of all skates (Rajidae) caught by broad 29 category of fishing gear, as observed in the Cefas observer programme (2002–2010)

Figure 2.3: Length-frequency of discarded and retained commercial skates (excluding 30 D. batis-complex and R. undulata) by (a) beam trawl, (b) otter trawl, (c) Nephrops trawl, (d) gillnets (all), (e) gillnets ≤150 mm mesh size and (f) gillnets >150 mm mesh size, as recorded in the Cefas observer programme

Figure 2.4: Length-frequency of discarded and retained (a) Raja clavata, (b) Leucoraja 31 naevus, (c) Raja brachyura, (d) Raja montagui, (e) Leucoraja fullonica and (f) Raja microocellata (all gear types, 2002–2010)

Figure 2.5: Length-frequency of discarded and retained Raja undulata captured by 32 beam trawl for the periods (a) 2002–2008 and (b) 2009–2010, and by otter trawl for the periods (c) 2002–2008 and (d) 2009–2010

Figure 2.6: Length-frequency of discarded and retained Dipturus batis-complex 32 captured by beam trawl for the periods (a) 2002–2008 and (b) 2009–2010, and by gillnet for the periods (c) 2002–2008 and (d) 2009–2010

Figure 3.1: Location of field studies undertaken during the course of project MB5202 52

Figure 3.2: Field work on (a) the Angelle Marie, showing (b) hauling the gillnets, (c) 53 skate in a gillnet, (d–e) measuring the total length and disc width of a tagged undulate ray Raja undulata, and (f–g) releasing a tagged thornback ray Raja clavata

Figure 3.3: Location of gillnet studies near Sandown Bay (Isle of Wight) in May 2010 54

Figure 3.4: Length distribution and numbers of the six batoid species caught whilst 55 gillnetting on the FV Angelle Marie (May 2010)

Figure 3.5: Length distribution and numbers of the four batoid species caught whilst 56 gillnetting on the FV Angelle Marie (Feb/Mar 2011)

Figure 3.6: Length distribution and numbers of the four batoid species caught whilst 57

ix gillnetting on the FV Angelle Marie (Mar 2011)

Figure 3.7: Location of trammel & tangle net studies off Cornwall within ICES areas 59 VIIe – VIIh in May & August 2011

Figure 3.8: Field studies on FV Govenek of Ladram showing (a) hauling trammel nets 60 aboard, (b-c) Dipturus cf. flossada measured & tagged prior to release, (d) fully scavenged Dipturus batis-complex after 24hr soak time, and (e) tagged Dipturus cf. intermedia prior to release

Figure 3.9: Length distribution of Dipturus cf. flossada (top) and Dipturus cf. 62 intermedia (bottom) caught in trammel and tangle nets during a survey by the FV Govenek of Ladram

Figure 3.10: Field work on (a) the fishing vessel Nicola May showing (b) deployment 64 of longlines, (c) close-up of longline showing sandeel bait, (d) longlines being deployed off the island of Brecqhou (Channel Islands), (e) captured blonde ray Raja brachyura at the surface, and (f) tagging an undulate ray Raja undulata

Figure 3.11: Length distribution and numbers of the skates caught whilst longlining on 65 the FV Nicola May (July 2010)

Figure 3.12: Field work on the fishing vessel Nicola May, including (a) hauling the 67 otter trawl, (b) ground gear used, with small hopper discs in wings, (c) cod-end being recovered and emptied, (d–e) typical catches of blonde and undulate ray, and (f) tagged common stingray Dasyatis pastinaca

Figure 3.13: Map of the Channel Islands and stations fished 68

Figure 3.14: Length distributions (by sex) for blonde and undulate ray and common 70 stingray

Figure 3.15: Field work on beam trawlers, including (a) recovery of beam trawl, (b) 73 typical catch on deck, (c) tagged common skate Dipturus cf. flossada, (d) tagged cuckoo ray Leucoraja naevus, (e) survival tanks, and (f) undulate ray Raja undulata in survival tank

Figure 4.1: Example PSA for demersal elasmobranchs that may be taken in gillnet 85 and otter trawl fisheries in the Celtic Sea

Figure 4.2: Trends in the mean relative abundance (ind.h–1) and frequency of 87 occurrence of four skate species in the Bristol Channel (VIIf, left hand panel) and four skate species in the Irish Sea (VIIa, right hand panel). Data from the UK beam trawl survey (based on 97 stations (33 in VIIf, and 64 in VIIa) fished at least 16 times during

x the 19 year time series)

Figure 4.3: Trends in the mean relative abundance (ind.h–1) and frequency of 88 occurrence of five skate species in the eastern English Channel and southern North Sea (VIId and IVc). Data from the UK beam trawl survey (based on 77 stations fished at least 16 times during the 19 year time series)

Figure 4.4: Trends in the mean relative abundance (numbers per 30 minute tow, grey 89 columns) and frequency of occurrence (solid line) for five skate species caught in the Great West Bay (western English Channel) during the Carhelmar survey (1989–2010)

Figure 4.5: Flow diagram for estimating total (dead) catch of skates 91

Acknowledgements

Thanks to the skippers and crews of the vessels who have helped with data collection, Cefas colleagues (Mat Evans, Rob Phillips, Joanne Smith and Mary Brown) for assisting with field work and Kieran Hyder for commenting on the report.

1. Introduction

Summary

(1) About 14 species of skate occur on the UK continental shelf, and the life histories and distributions of the various species means that they can have contrasting vulnerabilities to exploitation.

(2) The abundance, species composition and diversity of skates in British waters have changed over the course of the last century, and some of the larger-bodied species (e.g. white skate and common skate) have disappeared from parts of their former range.

(3) Management of skate fisheries was only introduced relatively recently, and measures may have only been restrictive since 2007 (North Sea) or 2009 (Celtic Seas ecoregion).

(4) Improved studies on various aspects of their biology, including the likelihood of them surviving capture and discarding, are required if appropriate and effective management measures are to be developed.

1.1 Project background

Elasmobranchs (sharks, dogfish, skates and rays) are highly vulnerable to fishing and are slow to recover from population depletion because their rate of reproduction is slow (a combination of the fact that they are long-lived, slow growing, late to mature, have protracted breeding cycles, and produce few young) and their large size and aggregating nature makes them susceptible to capture. Hence, it is essential to have conservative management if their fisheries are to be exploited sustainably and if populations of depleted species are to recover as rapidly as possible.

The morphology and behaviour of skates and rays makes them highly susceptible to capture in mixed demersal fisheries. Several species are also taken in targeted fisheries, using longline, gillnet or trawl. The abundance and diversity of the skate community around the British Isles has changed over the course of the last 100 years, and some of the larger-bodied species (e.g. white skate) have disappeared. In contrast, some of the smaller-bodied species (e.g. thornback ray) have healthier populations. Research has shown that some species have highly patchy distributions, and such species can be locally abundant yet susceptible to localised depletion.

To move towards more sustainable management of skate fisheries, a variety of measures have been introduced in recent years. For example, a skate quota was introduced into the Celtic Seas ecoregion in 2009, with landings data now to be

recorded separately for the main species. Some of the rarer species are designated as prohibited species that cannot be retained. Further mitigation measures are also possible, such as area or seasonal closures, or technical measures to limit by-catch. There has also been debate over size limits, because the efficacy of such measures is highly dependent on discard survival.

To evaluate the efficacy of current and other potential management measures it is necessary to collect evidence on the survivorship of those fish that are caught and discarded. Previous Defra-funded projects have examined some inshore fisheries (e.g. thornback ray in the Greater Thames Estuary and the Bristol Channel). However, the results of these studies cannot be used to gauge the survival of some of the other skates of conservation and/or commercial importance taken in different fisheries because the survivorship of rays after discarding is species-specific, and will also depend on the characteristics of the fishing methods in question. This work will support Defra in terms of national commitments to the European Community’s Action Plan for the conservation and management of elasmobranchs (CEC, 2009b), and to Defra’s Shark,Skate and Ray conservation plan (Defra, 2011).

1.2 The skate fauna of the British Isles

Approximately 14 species of skate1 (Rajidae) are known to inhabit the continental shelf surrounding the British Isles (Table 1.1). A variety of deep-water species also occur on the continental slope and in deep-water to the west and north of the British Isles, and there may be as many as 27 skate species around the British Isles. Little is known about the distribution, biology and fisheries of the deep-water skates and further studies on these species are clearly needed. For the purposes of the present paper we focus on those skate species occurring on the continental shelf around the British Isles (Figure 1.1).

Despite the overall importance of the skate complex to UK fisheries, scientific studies to better understand this group of fish in UK seas have only been periodic, with much of our knowledge derived from a relatively small number of workers, such as Robert Clark (Clark, 1922, 1926, 1927), George Alexander Steven (Steven 1931, 1932, 1933, 1934, 1936, 1947) and Mike Holden and his co-workers (Holden, 1963, 1972, 1975; Holden et al., 1971; Holden and Vince, 1973; Holden and Tucker, 1974). The studies of Marie-Henriette du Buit, based in Concarneau, have also provided invaluable information on the skates and skate fisheries along the western coasts of the British Isles (Du Buit, 1968a,b, 1970, 1972a,b, 1973, 1975a,b, 1976a,b, 1978, 1989; Du Buit and Maheux, 1986). More recently, there were in-depth studies on the skates in the North Sea (Walker & Heessen, 1996; Walker et al., 1997; Walker & Hislop, 1998).

Early ichthyologists had differentiated between the blue or common skate and the flapper skate, although a taxonomic revision of the European skates in the 1920s

1 Although the common names of some skate species refer to them as rays (e.g. thornback ray), for the purposes of this report we use the term ‘skate’ to refer to all members of the family Rajidae. The term ‘batoids’ is used to refer to all skates as well as other rays (e.g. stingrays, eagle rays, electric rays). 2 combined these species as common skate Raja batis. Subsequent taxonomic work differentiated the rajids into various genera, with common skate then re-named Dipturus batis. French scientists examining the molecular genetics of skates have recently reported genetic differences in specimens of “Dipturus batis”, and subsequently listed distinguishing characteristics for the two species (Iglésias et al., 2010). A subsequent study confirmed these genetic differences (Griffiths et al., 2010). The nomenclature of the ‘common skate complex’ is currently being updated. Taxonomists working on the problem initially proposed that former scientific names should be resurrected for the two species: Dipturus cf. flossada and D. cf. intermedia, but this proposed change needs to be validated by the International Commission on Zoological Nomenclature (Iglésias et al., 2010). Taxonomic rules, however, indicate that one of the species (the form described as Dipturus cf. flossada) should remain as Dipturus batis, whilst the larger species will likely be named either Dipturus intermedia or Dipturus macrorynchus. For the purposes of this report the names Dipturus cf. flossada and D. cf. intermedia have been used in oreder to distinguish the two species.

Although the overall geographical distributions of the two species are unclear, Griffiths et al. (2010) observed that samples from ICES Division VIa were generally genetically distinct from samples collected in the Celtic Sea, with flapper skate Dipturus cf. intermedia and occasional blue skate D. cf. flossada taken in VIa, and D. cf. flossada taken on the Rockall Bank and in the Celtic Sea.

Table 1.1: Taxonomic list of skates (Rajidae) occurring around the British Isles, including adjacent deep-water habitats in the North-east Atlantic. Those species that may be encountered on the continental shelf are highlighted with an asterisk. Sources are (1): Wheeler (1992); (2): Wheeler et al. (2004); (3): Griffiths et al. (2010; (4): Iglésias et al. (2010); (5) Froese & Pauly (2011). Other sources of information include: Le Danois (1913); Jenkins (1925); Poll (1947); Wheeler (1969, 1978); Edwards & Davis (1997).

Scientific name and authority Common name Source 1 Amblyraja hyperborea (Collett, 1879) Arctic skate (2) 2 Amblyraja jenseni (Bigelow & Schroeder, 1950) Short-tail skate (2) *3 Amblyraja radiata (Donovan, 1808) Starry ray (1) 4 Bathyraja pallida (Forster, 1967) Pale ray (2) 5 Bathyraja richardsoni (Garrick, 1961) Richardson’s ray (2) 6 Bathyraja spinicauda (Jensen, 1914) Spinetail ray (2) - Dipturus batis (Linnaeus, 1758) Common skate *7 = Dipturus cf. flossada = Blue skate (1,2,3,4) *8 = Dipturus cf. intermedia = Flapper skate 9 Dipturus linteus (Fries, 1838) Sailray (5) 10 Dipturus nidarosiensis (Storm, 1881) Norwegian skate (2) *11 Dipturus oxyrinchus (Linnaeus, 1758) Long-nosed skate (1) *12 Leucoraja circularis (Couch, 1838) Sandy ray (1) *13 Leucoraja fullonica (Linnaeus, 1758) Shagreen ray (1) *14 Leucoraja naevus (Müller & Henle, 1841) Cuckoo ray (1) 15 Malacoraja kreffti (Stehmann, 1977) Krefft’s ray (2) 16 Malacoraja spinacidermis (Barnard, 1923) Soft skate (5) 17 Neoraja caerulea (Stehmann, 1976) Blue ray (2) *18 Raja brachyura Lafont, 1873 Blonde ray (1) *19 Raja clavata Linnaeus, 1758 Thornback ray (1) *20 Raja microocellata Montagu, 1818 Small-eyed ray (1) *21 Raja montagui Fowler, 1910 Spotted ray (1) *22 Raja undulata Lacepède, 1802 Undulate ray (1) 23 Rajella bathyphila (Holt & Byrne, 1908) Deepwater ray (2) 24 Rajella bigelowi (Stehmann, 1978) Bigelow’s ray (2) *25 Rajella fyllae (Lütken, 1887) Round skate (1) 26 Rajella kukujevi (Dolganov, 1985) Mid-Atlantic skate (2) *27 Rostroraja alba (Lacepède, 1803) White skate (1)

Figure 1.1: Main skate species occurring on the continental shelf of the United Kingdom, showing (a) starry ray Amblyraja radiata, (b) common skate Dipturus batis cf. flossada, (c) sandy ray Leucoraja circularis, (d) shagreen ray L. fullonica, (e) cuckoo ray L. naevus, (f) blonde ray Raja brachyura, (g) thornback ray R. clavata, (h) small-eyed ray R. microocellata, (i) spotted ray R. montagui and (j) undulate ray R. undulata.

1.3 UK skate fisheries: A historical perspective

Traditionally, skates were of limited market value, and those that were landed in the early 1800s were generally for use as either pot bait or for fishermen’s families (Day, 1880–1884; Steven, 1932). Indeed, along with gurnards, scad and dogfishes, skates and rays were referred to as ‘rabble fish’ (Couch, 1862-5). This lack of perceived importance was also mirrored in some of the earlier books on the biology of British marine fishes, for example McIntosh and Masterman (1897) excluded all elasmobranch fish. Nevertheless, in certain areas, skates were of importance for some markets (e.g. white skate were sold to the French, see Section 1.4).

In the late 1880s and early 1900s, however, skates became increasingly marketable, and Day (1880–1884) stated that “now they are consigned to the London markets“. The increasing fishing power at this time resulted in a steady increase in skate landings during the first part of the 20th century. Reported UK skate landings were in the region of 25–30,000 t per year between 1908 and the mid-1930s (with the exception of the First World War). Skate landings began to decline in the late 1930’s and, after the Second World War, landings were in the region of 20,000 t per year. Since 1958, UK landings have declined steadily (Figure 1.2) and have been <5,000 t per year since 2005. This recent period of decline will also reflect recent management measures that have reduced fishing capacity, and also the introduction of a quota for skates and rays (see Section 1.5) which may have become restrictive for some fisheries in recent years.

Figure 1.2: UK landings of skates and rays (Rajidae) during the period 1903–2008.

1.4 Longer-term changes in skate populations

Given that skates were traditionally reported under the generic landings category “skates and rays”, it has not been possible to fully evaluate longer term patterns in landings of particular species (ICES, 2009, 2010a). Even though species-specific landings data were reported by some European nations (e.g. France), such information can contain taxonomic errors, for example spotted and blonde rays may be mixed together (see ICES, 2009), and the larger, long-nosed skates can be incorrectly identified (Iglésias et al., 2010). Such taxonomic problems will also affect the species-specific landings data that are currently being collected, although most Member States have initiated some degree of training for market sampling staff.

Fishery-independent trawl surveys currently provide the most temporally comprehensive species-specific data, and such surveys have been the basis of ICES advice (ICES, 2008a, b). However, it should be recognised that the suitability of these data are compromised by (a) incorrect species identifications in some surveys (e.g. in the case of thornback ray Raja clavata and starry ray (or thorny skate) Amblyraja radiata in some surveys within the International Bottom Trawl Survey (IBTS) of the North Sea (ICES, 2007a, b); (b) that the surveys were not originally designed to provide abundance indices for skates, and so the type of gear used and/or the distribution of survey hauls may not be appropriate for some skate species; and (c) catch rates for some of the more uncommon and/or patchily distributed skates are often low and variable. Also, it must be recognised that most of these surveys cover periods of less than 20 years, and whereas they may be appropriate for examining recent trends in relative abundance, there is less opportunity for examining longer-term changes in relative abundance.

Given that skates have been subject to exploitation for over 100 years, yet species- specific data prior to the 1970’s is only sporadic, qualitative information from the historical, ichthyological literature can help inform our perspectives on the distribution and general status of fishes, including skates (Quero and Cendrero, 1996).

Historical accounts of British fishes allow us to infer that some of our larger-bodied skates have declined dramatically. Although this has been well documented for species such as the ‘common skate complex’ (Brander, 1981), it has been less documented for white skate Rostroraja alba. This species was “much esteemed by the French who, as long ago as the time of Ray, 1658, observed that French vessels used to arrive at St Ives, in Cornwall, to purchase this fish; and which commerce has been continued up to the present time” (Day, 1880–1884). Prior to this, Yarrell (1839, 1841) stated that “The French are great consumers of skate, and this species is the favourite fish: their boats come to Plymouth during Lent to purchase skate”. The importance of white skate was also highlighted by Couch (1862-5) who considered that white skate was “the species to which they give a preference”, as it was the largest of the British rays “For whilst its measurement is often equal to that of the largest common skate, its greater thickness causes it to be of heavier bulk“. French ichthyologists also regarded white skate to be common in the English Channel, Moreau (1881) writing “La Raie blanche est assez commune dans la Manche pendant le mois d’été; elle paraît moins commune dans l’Ocean”. Although Nobre (1935) did not consider white skate to be particularly common in Portuguese waters, Lozano Rey (1928) had previously noted that “La R. alba Lacépède es una especie

7 propia de las costas atlánticas y mediterráneas europeas, que se encuentra con relative frequencia en todo el litoral ibérico. Vivo en profundidades de alguna consideración, capturándose con el arte del bou. Es una raya de alas carnosas algo estimata en los mercados por esa circunstancia y por la gran talla que pueda alcanzar”2.

It is thought that earlier descriptions of Raia marginata refer to juvenile white skate, and correspondents to Couch (1862-5) stated that this species was “rather plentiful in Portland Roads, on a sandy bottom” and that it “prefers sandy bays, partially landlocked, and not very deep water”. Ominously, this correspondent to Couch later added “the bordered ray has of late become much more scarce near Weymouth, if not altogether disappeared”. That this species was thought to prefer partially landlocked sandy bays would be supported by the presence of white skate in the Baie de Dournanez (Brittany), another area where this species seems to have been extirpated from. Although it is unclear as to exactly when the white skate declined most, it was probably in the late 1800s and early 1900s, given that Steven (1932) only recorded them in small quantities. Herdman and Dawson (1902) considered that it occurred in the Irish Sea, which is another area from where there have been no recent records, although these authors noted that some earlier reports of large skates could confuse white skate with the D. batis-complex.

The decline in the numbers of white skate in the English Channel and other parts of northern Europe went unnoticed, or at least largely unreported, at least until highlighted by Dulvy et al. (2000) and Rogers and Ellis (2000). Dulvy et al. (2000) also suggested that Dipturus oxyrinchus had also been lost from the Irish Sea, although this has been questioned as there is no reliable evidence to support this perception (Ellis et al., 2002).

Although the loss of common skate in the Irish Sea was established in the scientific literature earlier (Brander, 1981), this paper suggested that D. batis was not uncommon in the late 1940s, and Brander (1981) commented that “The disappearance of R. batis is therefore not surprising, but that this took place virtually unnoticed or without comment in the fisheries literature, perhaps is surprising”. Nevertheless, fisheries scientists had highlighted the need for the conservative management of skates (and elasmobranchs in general) for some years prior to this (e.g. Holden, 1973, 1974, 1977). Indeed, Holden (1977) considered that “it seems very probable that these stocks of skates have not been replacing themselves for 15–20 years now”.

However, it must also be recognised that concerns over skates had long been expressed prior to the work of Holden. For example, Minchin (1911) noted that “unhappily the trawls are gradually extirpating the rays, a slow-growing and not very prolific tribe”. Subsequently, Howell (1921) highlighted that there were “very large gaps which exist in our knowledge of the life-histories of the many tribes of Raiidae” and felt that “It will lamentable indeed if, when the time comes, naturalists remain

2 “R. alba Lacépède is a typical species of European Atlantic and Mediterranean coasts that is found relatively frequently off all Iberian coasts. It lives in a variety of depths and is captured with “el arte del bou” (a type of trawl). It is a ray with much flesh on the wings, somewhat esteemed in the markets for this reason and for the large size it can attain.” 8 unequipped with knowledge of the lives and habits of this widespread and most interesting family. For in that case exploitation is likely to proceed in unsound and un- economic lines”. Although the 1920s and 1930s saw progress in terms of biological studies on skates (see Section 1.2), Steven (1932) also noted that “The statistics at present available show an alarming decline in the total British catches of Rays and Skates from the English Channel”.

1.5 Recent management of skate fisheries

Despite concerns over the status of skate stocks, including over-fishing and the loss of formerly abundant species from some areas, the introduction of management has been slow. Although some English and Welsh Sea Fisheries Committees (SFCs) introduced minimum landing sizes for all ‘skates and rays’, national and international measures have only been brought in relatively recently.

A total allowable catch (TAC) for all skates and rays was first established in the North Sea (EC waters of ICES Division IIa and sub-area IV) in 1999, and set at 6,060 t for both 1999 and 2000 (Table 1.2). The TAC was then reduced by 20% (to 4,848 t) for the period 2001–2002. There have since been annual reductions of 8–25% in the skate and ray TAC for most years, and this TAC was reduced to a record low of 1,397 t for 2010. It may also be noted that the TAC has been higher than reported landings for much of this period (although it must be recognised that quota may have been restrictive for some fisheries, depending on allocation), and so restrictive management may have only been in place for a few years. In terms of other EC waters (ICES Divisions IIIa, VI–IX), TACs for skates were only established for 2009.

There have also been other measures introduced, including bycatch quotas and technical measures. The 2007 skate TAC for the North Sea was deemed a bycatch quota, whereby skates were not to comprise more than 25% by live weight of the catch retained on board. This measure was unpopular with inshore fishermen in the southern North Sea, where R. clavata is locally abundant, and was later applied only to vessels greater than 15 m overall length. Some of the problems that arose with the introduction of the bycatch quota were the increased retention of non-target fish (e.g. lesser-spotted dogfish Scyliorhinus canicula and smooth-hounds Mustelus spp.) to increase the total catch on board, and some vessels would land (or report) more fish from the adjacent fishing grounds in ICES Division VIId. There are also mesh size regulations for those fisheries targeting skates and rays (CEC, 1998).

Although the introduction of TACs and other measures have been used in skate management for about a decade or so, these management measures were traditionally applied to the skate complex as a whole, and species-specific measures have only evolved since 2007, when skate landings (for the main species) from the North Sea were to be reported to species level. The TAC for skates in the North Sea is now currently at a comparable level to reported landings, and further reductions in this TAC may result in discarding. Such discarding may not benefit those stocks of most concern to managers, and so there needs to be due consideration of management measures that are more targeted to benefiting those skate stocks of most concern.

In 2008, several skate species were listed as species that were not to be fished for, retained or sold, and there were some regional differences in these listings. Whereas some of these listings were not questioned by the fishing industry (e.g. white skate), there were complaints from the fishing industry regarding undulate ray, which is locally abundant in parts of the English Channel, and common skate, which can be caught frequently on some offshore grounds in the south-west, and may have a high discard mortality in some of these fisheries.

Table 1.2: Introduction of management measures for skates and rays, including Total Allowable Catches (TAC, tonnes) for various parts of the ICES area.

EC waters of North EC waters EC EC Sea (IV) of VIa–b EC waters Year waters of waters of Source and and VIIa–c, of VIII and IX IIIa VIId Norwegian e–k Sea (IIa) 1999 6,060 CEC (1999a) 2000 6,060 CEC (1999b) 2001 4,848 CEC (2000) 2002 4,848 CEC (2001) 2003 4,121 CEC (2002) 2004 3,503 CEC (2003) 2005 3,220 CEC (2004) 2006 2,737 CEC (2005) 2007 2,190 (1) CEC (2006) 2008 1,643 (2) CEC (2008) 2009 1,643 (3–5) 68 (3,5) 1,044 (3,8) 15,748 (6–7) 6,423 (9,10) CEC (2009a) 2010 1,397 (3–5) 58 (3,5) 887 (3,8,12) 13,387 (6,7,11) 5,459 (9,10) CEC (2010) 2011 1,397 (3–5) 58 (3,5) 887 (3,8,12) 11,379 (6,7,11) 4,640 (9,10) CEC (2011) 2012 1,395 (3–5) 58 (3,5) 887 (3,8,12) 9,915 (6,7,11) 4,222 (9,10) CEC (2012a)

(1) By-catch quota. These species shall not comprise more than 25 % by live weight of the catch retained on board. (2) Catches of Cuckoo ray (Leucoraja naevus) (RJN/2AC4-C), Thornback ray (Raja clavata) (RJC/2AC4-C), Blonde ray (Raja brachyuran) (RJH/2AC4-C), Spotted ray (Raja montagui) (RJM/2AC4-C), Starry ray (Amblyraja radiate) (RJR/2AC4-C) and Common skate (Dipturus batis) (RJB/ 2AC4-C) shall be reported separately. (3) Catches of Cuckoo ray (Leucoraja naevus) (RJN/2AC4-C), Thornback ray (Raja clavata) (RJC/2AC4-C), Blonde ray (Raja brachyura) (RJH/2AC4-C), Spotted ray (Raja montagui) (RJM/2AC4-C) and Starry ray (Amblyraja radiata) (RJR/2AC4-C) shall be reported separately. (4) By-catch quota. These species shall not comprise more than 25 % by live weight of the catch retained on board. This condition applies only to vessels over 15 m length overall. (5) Does not apply to Common skate (Dipturus batis). Catches of this species may not be retained on board and shall be promptly released unharmed to the extent practicable. Fishers shall be encouraged to develop and use techniques and equipment to facilitate the rapid and safe release of the species. (6) Catches of Cuckoo ray (Leucoraja naevus)) (RJN/67AKXD), Thornback ray (Raja clavata) (RJC/67AKXD), Blonde ray (Raja brachyura) (RJH/67AKXD), Spotted ray (Raja montagui) (RJM/67AKXD), Smalleyed ray (Raja microocellata) (RJE/67AKXD), Sandy ray (Leucoraja circularis)(RJI/67AKXD) and Shagreen ray (Leucoraja fullonica) (RJF/67AKXD) shall be reported separately. (7) Does not apply to Undulate ray (Raja undulata), Common skate (Dipturus batis), Norwegian skate (Raja (Dipturus) nidarosiensis) and White skate (Rostroraja alba). Catches of these species may not be retained on board and shall be promptly released unharmed to the extent practicable. Fishers shall be encouraged to develop and use techniques and equipment to facilitate the rapid and safe release of the species. (8) Does not apply to Common skate (Dipturus batis) and Undulate Ray (Raja undulate). Catches of this species may not be retained on board and shall be promptly released unharmed to the extent practicable. Fishers shall be encouraged to develop and use techniques and equipment to facilitate the rapid and safe release of the species. (9) Catches of Cuckoo ray (Leucoraja naevus) (RJN/8910-C), Thornback ray (Raja clavata) (RJC/8910-C) shall be reported separately. (10) Does not apply to Undulate ray (Raja undulata), Common skate (Dipturus batis) and White skate (Rostroraja alba). Catches of these species may not be retained on board and shall be promptly released unharmed to the extent practicable. Fishers shall be encouraged to develop and use techniques and equipment to facilitate the rapid and safe release of the species. (11) Of which up to 5 % may be fished in EU waters of VIId (12) Of which up to 5 % may be fished in EU waters of VIa, VIb, VIIa–c and VIIe–k

1.6 Aims and objectives

Now that management measures have started to become restrictive for skates (either through ‘prohibited species’ or restrictive quotas), issues of discard survivorship have become increasingly important. Additionally, progress made within the ICES Working Group on Elasmobranch Fishes will likely see further exploratory assessments for skates.

The aims and objectives of the project were:

(1) To identify the skate species discarded in representative UK fisheries and to highlight significant data gaps in our knowledge of their discard survival;

(2) To examine short-term survival (using on-board survival tanks) and longer-term survival (using a tag and release scheme) for the species and stocks of principal interest/ concern. Without pre-judging the outcome of (1), it is suggested at this stage that the focus will be on (a) cuckoo ray (Leucoraja naevus) captured in the beam trawl fleet operating in the south-west and (b) undulate ray (Raja undulata) taken in gill nets in the western English Channel;

(3) To collate anecdotal information and data from other sources on the factors affecting potential discard survival of all skates and rays caught in other fishing gears. This will include the views of a representative sample of the fishing industry;

(4) To evaluate the potential fisheries-induced mortality on skate populations and assess the risks to stock sustainability of continuing with current fishing practices;

(5) Identify other technical measures (e.g. closed areas, gear modification, size restrictions) that can best protect vulnerable stocks and provide evidence for their use in TAC and quota negotiations and as a part of the EU's Community Plan of Action (CPOA) for sharks.

1.7 Soliciting and collating representative views of the fishing industry

In order to bring together some of the views of the wider commercial fishing industry, a questionnaire (Annex II) was produced. This was initially trialled by circulating the questionnaire within members of the Cornish Fish Producer Organisation (CFPO), and was subsequently more widely distributed to fish producer organisations (FPOs), fishermen’s associations, Inshore Fisheries and Conservation Authorities (IFCAs) and Marine Management Organisation (MMO) offices around England and Wales electronically and/or with hard copies. Organisations contacted are summarised in Annex III.

Other elasmobranchs were also included in this questionnaire, partly in support of a parallel Defra-funded project3, and although some results for dogfish are given here,

3 MB5201: Assessing survivability of bycaught porbeagle and spurdog and furthering our understanding of movement patterns in UK marine waters 11 further analyses and discussion of these data will be presented in a subsequent report.

1.8 Format of the report

The report is divided into five main sections, including the present Introduction, which is partly based on a paper written during the course of the project (Ellis et al., 2010). Information on current discarding of skates, in terms of the quantities, species composition and discard-retention patterns is given in Section 2, and this work corresponds largely with a scientific paper written during the project (Silva et al., 2012). Section 3 summarises recent field investigations on commercial fishing vessels, and the results of some of these field trips have been included in another paper completed during the course of the project (Ellis et al., 2012a). Section 4 provides an overview of the current stock status of UK skates, discusses potential fisheries-induced mortality on skate populations and risks to stock sustainability. Finally, options for improved fisheries management of skates are discussed in Section 5.

Data collected during the project have also been used in a paper on the length at maturity for skates (McCully et al., 2012) and to support some of the work undertaken by the ICES Working Group on Elasmobranch Fishes (WGEF).

2. The skate species discarded in representative UK fisheries and data gaps in our knowledge of their discard survival

Summary

(1) In recent years, the proportion of skates reported to species level in UK (English and Welsh) fisheries has increased and in 2010, 90% of skates were reported to species.

(2) The species composition of skates in reported landings data was broadly comparable to that inferred from on-board catch sampling programmes, although some minor inconsistencies were noted (i.e. misidentifications).

(3) Skates may be discarded for various reasons, including that they are below marketable size, that quota is restrictive, that retention is currently prohibited (e.g. white skate, common skate and undulate ray), or that they are not marketable species.

(4) Information from discard observer programmes indicted that skates <30 cm in length were usually discarded, and that skates >60 cm were typically retained. About half the skates were retained at a length of 50 cm.

(5) The quantities of discarded skates in the main UK fisheries can be estimated from data collected during discard observer programmes.

2.1 Introduction

Skates are an important component of the demersal fish assemblage in many sea areas, with approximately 14 species occurring on the continental shelf of the British Isles (Wheeler, 1992; see Table 1.1). Their biological characteristics (e.g. longevity, slow growth rate, late age at maturity, protracted development period and low fecundity) make them highly vulnerable to over-exploitation (Holden, 1973; Ellis et al., 2008c). Their large size, flattened shape and aggregating nature also make them susceptible to capture in various fisheries (Ellis et al., 2010).

Traditionally, skates were of a low market value until late 1880s and early 1900s, when they became increasingly important (Ellis et al., 2010). However, since the late 1950s, UK landings have declined considerably (Figure 1.2) and, in recent years, management measures may have restricted some fishing opportunities (ICES, 2010a). Although there are some localised UK fisheries that target skates (e.g. in the southern North Sea and Bristol Channel), skates are often landed as an important bycatch in mixed demersal trawl fisheries (Enever et al., 2009; ICES, 2010a).

Skate landings for most nations (including the UK) were, until 2008/2009, typically reported under a generic category of “skates and rays” (ICES, 2010a). The lack of species-specific data has meant that some formerly abundant skate species disappeared from parts of their former range almost unnoticed, including the Dipturus batis-complex and Rostroraja alba (Brander, 1981; Rogers & Ellis, 2000). The generic “skates and rays” data has hampered individual stock assessments, with recent ICES advice for skate stocks based on the interpretation of their spatial distribution and relative abundance in fishery-independent groundfish surveys (ICES, 2008a, b).

In recent years, there has been an increased focus on using observers to collect data on commercial fishing vessels (Borges et al., 2005; Enever et al., 2007; Gonçalves et al., 2007), so that total catches of commercial species can be better estimated. However, data from observer trips may also provide valuable information on the spatial distribution and length-frequency of discarded and retained fish, and can be used to estimate the species composition of those taxa not reported routinely to species level in landing statistics, and/or of other groups of fish for which species specific data are limited (e.g. skates). Such information can augment those data collected during fishery-independent surveys (e.g. Ellis et al., 2005a, b). To date, however, there have been relatively few studies examining the bycatch and discard patterns of elasmobranchs in European fisheries (Carbonell et al., 2003; Coelho et al., 2003, 2005; Damalas & Vassilopoulou, 2011) and elsewhere in the world (Tamini et al., 2006; Stevenson & Lewis, 2010).

The main aims of this part of the project were to (a) determine the proportion of skates now being reported to species level; (b) compare the species composition of skates landed by the main fisheries (based on fishing gear and area) with the species composition of skates as recorded during observer trips on commercial fishing vessels, in order to determine if they support recent species-specific landings data; (c) examine the length-based discard/retention patterns of skates (with retained fish those that fishers kept on board for marketing) were examined by gear and species, including for those skates currently listed as ‘Prohibited species’ in European fisheries (CEC, 2011); and (d) examine the relative quantities of skates being discarded in representative UK fisheries.

2.2 Materials and methods

2.2.1 Landings data

Landings data for UK-registered vessels were extracted from the UK Fishing Activity Database (FAD) for the period 2007−2010 inclusive, with data allocated to gear and ICES Division (Table 2.1). The main skate species reported are given in Table 2.2. These data included reported landings for England, Wales, Northern Ireland and the Channel Islands (and also included any Scottish vessels landing into England, Wales and Northern Ireland). The various gears were allocated to the following broad categories of gear type (i) beam trawl, (ii) otter trawl, including pair trawls and twin rig trawl, (iii) Nephrops trawl, (iv) gillnets, including drift and trammel nets, (v) lines (including hand lines and longlines), and (vi) other gears (e.g. seines, mid-water trawl and dredges). These data were examined to identify which combinations of gear and ICES Division accounted for most of the reported skate landings. It is recognised that

14 these data may not be fully accurate for inshore fleets, where several gears can be used by a single vessel, and that each of these broad gear types can represent multiple métiers.

2.2.2 Observer data

The Cefas observer programme collects catch and discards information on English- registered commercial fishing vessels, and has been undertaken since 2002, as required by EC Data Collection Framework 199/2008. Data used for the purpose of this study were for the period 2002−2010. Vessel selection and sampling protocols were described by Enever et al. (2007) and Catchpole et al. (2011). Large catches were sub-sampled, although those data from hauls with raising factors >50 were excluded in the present analysis. All length measurements of skates refer to total length (LT), as measured to the cm below.

2.2.3 Species identification

Species identification of skates, both in fisheries-independent and fishery-dependent data, remains problematic (ICES, 2007a,b, 2010a). These problems can result from either poor species-identification or, more simply, from the use of common names that can be attributable to multiple species.

To minimise potential misidentification issues, the spatial distribution of all species and their size distributions were examined with published studies (Ellis et al., 2005a,b), so that records of fish outside their known biogeographical and/or bathymetric range, less than the size at birth or greater than the maximum length of the species could be checked. Where possible, these data were corrected. If no appropriate corrections could be made, then the records were analysed at the family level. At the start of the discard observer scheme (2002), 120 cm was used as a maximum length, and a few early records of the D. batis-complex (n = 7) and Dipturus nidarosiensis (n=1) reported lengths of ‘120 cm+’. These data were converted to the mean length of specimens >120 cm recorded in subsequent years (126 cm for the D. batis-complex and 159 cm for D. nidarosiensis).

2.2.4 Conversion of length to weight

The length-based data collected by observers on commercial vessels was converted to biomass, using length-weight relationships for the various species as collected during scientific trawl surveys (McCully et al., 2012). Data for Dipturus oxyrinchus, D. nidarosiensis and Leucoraja circularis were too limited to determine a species- specific length-weight relationship, and so the length-weight relationships for congeneric species (D. batis-complex and L. fullonica) were applied. Lengths for Rajella fyllae, R. alba and skates of uncertain identification (treated as Rajidae), were converted to weight using the length-weight relationship for Raja clavata.

2.2.5 Data analysis

The species composition of retained skates during observer trips on commercial fishing vessels was calculated from the total estimated biomass aggregated across different trips, for the years 2008–2010. This was undertaken for the main UK

15 fisheries (as identified from national landings data, Table 2.1) for which there was observer coverage. The observer data available for these fisheries over the period, in terms of the number of trips and hauls (for those trips in which skates were encountered) is shown in Table 2.3, and the spatial coverage of both reported landings and observer data shown in Figure 2.1.

For the analyses of length-based discard/retention patterns, data covered the North Sea ecoregion (ICES Sub-area IV and Division VIId) and Celtic Seas ecoregion (VIa, VIIa,b,e-j), whilst the more limited data from other regions were excluded. For the six main commercial skate species by weight (Leucoraja naevus, L. fullonica, Raja brachyura, R. microocellata, R. montagui, and R. clavata), the length-frequency distributions for discarded/retained skates were examined by gear type (Figures 2.2 and 2.3) and species (Figure 2.4) for the period 2002–2010. Analyses for gillnet catches were also undertaken separately by mesh size, as they are a bycatch in fisheries using gillnets of ≤150 mm, whilst they may be an important bycatch in fisheries using larger (>150 mm) gillnets or targeted in gillnets ≥220 mm. Catch and landings data for Raja undulata and D. batis-complex were analysed separately for the periods before and after inclusion on the ‘prohibited species list’ of the EC’s technical regulations.

2.3 Appraisal of recent species-specific landings data

2.3.1 Reported landings from UK-registered vessels

From 2007–2010, UK-registered vessels reported between 2,007 and 2,393 t of skates and rays each year (Table 2.1). These landings were primarily reported by otter trawl (55.9%), gillnet (18.7%) and beam trawl (15.5%), with smaller quantities taken by Nephrops trawl (5.9%), lines (3%) and ‘other gears’ (1%).

In terms of the spatial distribution, the majority of these landings (>85%) were reported from six ICES Divisions, covering the south-western approaches (VIIf: 27.1%; VIIe: 20.5% and VIIh: 8%), Irish Sea (VIIa: 10.0%), eastern English Channel (VIId: 7.4%) and southern North Sea (IVc: 12.6%).

More than 95% of the reported skate landings originated from 19 combinations of gear and ICES Division, and the overall proportion of total skate landings reported to species level increased from about 42% (2008) to 92% (2010) (Table 2.1). The main commercial skate species were R. clavata, R. brachyura, L. naevus, R. microocellata and R. montagui (Table 2.2).

Figure 2.1: Spatial distribution of UK commercial landings of skates (Rajidae) indicating the mean annual landings (tonnes) for the period 2008–2010 by ICES statistical rectangle (circles) and those rectangles for which there were observer data indicated (+). Data given for (a) otter trawl, (b) beam trawl, (c) Nephrops trawl and (d) gillnet.

Table 2.1: Reported UK landings (see text) of skates (Rajidae) for the years 2007–2010, giving total landings (tonnes), and the quantity (tonnes and percentage of total) reported to species level by area and gear type for the main UK fisheries. Gear types include beam trawl (BT), otter trawl (OT), gill and tangle nets (GN), Nephrops trawl (NT) and longline (LL).

Skate landings Total landings of skates, Rajidae Skate landings reported reported to species (t) to species level (t) Area Gear level (%) 2007 2008 2009 2010 2008 2009 2010 2008 2009 2010 NT 114.3 153.9 124.3 121.8 60.0 72.6 94.1 39.0 58.4 77.3 Irish Sea OT 110.5 84.8 56.9 37.9 50.4 52.6 37.0 59.5 92.4 97.7 GN 14.9 3.3 16.8 15.9 3.2 16.7 9.6 97.6 99.0 60.0 OT 503.6 520.0 406.4 520.0 222.6 324.1 485.3 42.8 79.8 93.3 Bristol Channel GN 72.6 86.0 103.4 131.0 13.7 73.1 106.2 15.9 70.7 81.1 BT 60.4 32.9 32.0 24.8 11.1 22.3 24.8 33.7 69.7 99.9 OT 180.7 239.0 165.9 253.9 164.9 163.6 253.8 69.0 98.6 100.0 Celtic Sea BT 167.1 154.8 137.2 130.6 124.3 132.0 130.6 80.3 96.2 100.0 GN 24.7 11.2 12.3 40.2 7.0 10.3 39.7 62.6 83.8 98.7 OT 316.6 271.3 200.7 298.3 27.1 153.0 294.1 10.0 76.2 98.6 Western English GN 80.9 87.0 121.9 129.8 26.6 106.9 122.7 30.6 87.7 94.5 Channel BT 93.6 105.6 75.2 87.6 19.9 55.3 87.5 18.8 73.5 99.9 GN 168.4 219.6 168.1 184.1 50.4 94.9 151.8 22.9 56.4 82.4 Southern North Sea OT 157.9 171.8 148.5 135.0 95.4 128.2 128.5 55.5 86.4 95.2 and eastern English Channel BT 58.1 51.5 65.0 58.3 15.1 57.5 58.2 29.3 88.5 99.8 LL 84.5 92.6 22.4 49.3 56.9 22.3 49.2 61.5 99.6 100.0 Central and northern OT 41.7 59.0 68.0 33.8 20.5 62.1 33.4 34.8 91.3 98.7 North Sea BT 16.0 9.3 22.8 23.9 3.4 22.8 23.7 36.1 100.0 99.3 West of Ireland OT 53.4 72.1 14.6 16.4 59.8 14.6 16.4 82.8 99.7 100.0 Other - 73.2 44.2 45.0 89.0 12.0 29.1 42.7 27.3 64.7 48.0 TOTAL 2393.3 2469.9 2007.3 2381.6 1044.4 1613.9 2189.4 42.3 80.4 91.9

Table 2.2: Reported landings (t) of skate species by UK (English and Welsh) fleets (2008–2010)

Species name 2008 2009 2010 Average Raja clavata 441.7 712.4 869.2 674.5 Raja brachyura 155.8 337.3 490.5 327.9 Leucoraja naevus 218.4 266.8 347.0 277.4 Raja microocellata 88.3 166.9 246.9 167.4 Raja montagui 21.6 65.8 127.4 71.6 Leucoraja fullonica 12.5 33.0 86.2 43.9 Dipturus nidarosiensis 43.1 4.9 0.1 16.0 Leucoraja circularis 13.6 13.1 14.8 13.8 Dipturus oxyrinchus 20.7 8.8 1.9 10.5 Dipturus batis 24.1 1.6 2.4 9.4 Raja undulata 2.4 1.7 - 2.1 Amblyraja hyperborea - 0.6 2.3 1.4 Amblyraja radiata 1.1 0.9 0.5 0.9 Rostroraja alba 1.0 0.1 0.1 0.4 Skate (indet.) 1425.5 393.4 192.2 670.4 Grand Total 2469.9 2007.3 2381.6 2286.3

Table 2.3: Observed fisheries with discarded/retained skates by gear (BT = beam trawl; OT = otter trawl; GN = gill and tangle nets; NT = Nephrops trawl; LL = longline) and area for the main UK fisheries for the years 2008–2010 (source: Cefas observer programme)

Gear 2008 2009 2010 Area group Trips Hauls Trips Hauls Trips Hauls NT 17 29 6 8 2 7 Irish Sea OT 7 27 2 4 6 13 GN ------OT 15 51 14 46 10 45 Bristol Channel GN 3 21 3 14 1 2 BT 1 18 3 65 3 67 OT 5 12 2 4 2 14 Celtic Sea BT 7 175 5 98 4 51 GN 3 23 2 5 5 48 OT 69 131 31 60 22 52 Western English GN 3 6 11 21 9 26 Channel BT 9 70 28 273 19 127 GN 15 38 20 64 7 15 Southern North Sea OT 6 32 6 13 9 42 and eastern English Channel BT 1 35 2 28 4 103 LL 1 2 - - - - Central and northern OT 19 85 19 82 26 139 North Sea BT ------TOTAL 181 755 154 785 129 751

2.3.2 Irish Sea

Otter trawlers in the Irish Sea (ICES Division VIIa) caught and retained mostly R. clavata (81.4–98.8% of reported landings; 99.4–100% of retained skates in observer trips). R. brachyura was of secondary importance in the reported landings (1.2– 12.6%), although this species was not recorded during observer trips (Table 2.4).

The south-west of the Isle of Man and the grounds off Cumbria are important fishing grounds for Nephrops norvegicus, and R. clavata was the main skate species reported in both the commercial landings (96.7–98.6%) and observer data (88.4– 100%; Table 2.4). The average proportions of R. brachyura and R. montagui in reported landings were 1.1% and <0.2%, respectively. The former species was not observed during observer trips, whilst the latter was estimated to account for about 3% of the retained skates.

Reported landings from gillnetters in the Irish Sea comprised two skate species (R. clavata and, to a lesser extent, R. brachyura), although there were no observer data for this fishery during the study period. Overall, seven skate species were reported in landings data, including D. batis-complex, and observer coverage only recorded four of these species.

2.3.3 Bristol Channel

Gillnet and otter trawl catches in the Bristol Channel (ICES Division VIIf) were both dominated by three skate species: R. brachyura, R. clavata and R. microocellata (Table 2.5). There was broad agreement in the main species taken by otter trawl, and the mean proportions from reported landings and observer coverage were 28.1% and 30% respectively (R. brachyura), 31.9% and 25% (R. clavata) and 31.4% and 41.4% (R. microocellata). Small quantities of R. montagui were also present in both data sets. The species composition of gillnet catches also indicated the importance of R. brachyura, R. clavata and R. microocellata, although the catch proportions were more variable.

There was also an overall agreement between commercial and observer data for the main species taken by beam trawlers (L. naevus, R. brachyura, R. microocellata and R. montagui). The beam trawl fleet, which usually operates further offshore, consistently reported more L. naevus than the otter trawl fleet. Although R. clavata was reported in commercial beam trawl landings, this species was not observed in the observer programme.

Overall, commercial landings data included six skate species that were not reported in the observer programme: Amblyraja radiata, D. batis-complex, D. nidarosiensis, D. oxyrinchus, L. circularis and L. fullonica (Table 2.5).

2.3.4 Celtic Sea and Western English Channel

Leucoraja naevus was the major skate species reported from the Celtic Sea (ICES Divisions VIIg–h), and consistently made up 73–79% of beam trawl landings, and approximately 41.5% and 33.8% of reported otter trawl and gillnet landings, respectively (Table 2.6). A comparable proportion of L. naevus was evident in the observer data for beam trawl and gillnet.

Relatively high proportions of L. fullonica and D. batis-complex were also reported in this area. L. fullonica comprised approximately 1.3% (beam trawl) to 16.9% (otter trawl) of reported landings, and observer data suggested L. fullonica could account for 8.6% of beam trawl landings.

The main species retained and landed by all commercial fleets in the western English Channel (ICES Division VIIe) were R. brachyura and L. naevus (Table 2.7). The major species landed by beam trawlers in this ICES Division were R. brachyura (41.7%) and L. naevus (33%), and observer data also indicated that these were the main species landed. R. montagui, R. clavata and R. microocellata were of secondary importance. Landings from gillnetters and otter trawlers included a similar range of skate species, although a greater proportion of R. clavata was reported.

Reported landings of R. undulata and D. batis-complex decreased over the study period, in line with the introduction of management measures in 2009. Commercial landings data from both the Celtic Sea and western English Channel included five skate species that were not recorded on observed trips: A. radiata, D. nidarosiensis, D. oxyrinchus, L. circularis and R. alba (Tables VI–VII).

2.3.5 Southern North Sea and Eastern English Channel

Commercial fisheries by beam trawl, otter trawls and gillnets in the southern North Sea (ICES Division IVc) and eastern English Channel (VIId) reported primarily R. clavata and R. brachyura, with smaller quantities of R. microocellata and R. montagui (Table 2.8). Raja clavata was the main species landed in the overall area, accounting for about 51.7%, 87.2% and 95.8% of reported beam trawl, gillnet and otter trawl landings. R. brachyura was also an important constituent of beam trawl (28.9%) and gillnet (9.2%) catches. Landings of R. brachyura from gillnetters were proportionately higher in the reported landings than from the observer data. Although R. montagui accounted for approximately 14.5% of reported beam trawl landings, observer data indicated a much lower proportion (2.7%).

Skate landings from longliners were composed primarily of R. clavata (79.3–93.8%), and R. brachyura (5.6–17.4%), with smaller quantities of R. montagui and R. microocellata also taken (Table 2.9).

Seven species of skate (Amblyraja hyperborea, D. batis-complex, D. oxyrinchus, L. circularis, L. fullonica, L. naevus and R. alba) were recorded in low quantities in landings data from these fisheries, but were not reported during observer trips (Table 2.8). Once again, the proportion of R. undulata in reported landings decreased over the study period.

2.3.6 Northern and Central North Sea

Commercial otter trawlers in the central and northern North Sea (ICES Divisions IVa– b) landed primarily R. clavata (ca. 89.5%) and, to a lesser extent, R. montagui (6.8%). Small quantities of R. brachyura and L. naevus were also reported (Table 2.9). Data from the observer programme suggested a higher proportion of R. montagui in the landings than indicated from reported landings.

Reported beam trawl landings from this area were comprised primarily of R. montagui (49.6%), R. clavata (32.4%), and R. brachyura (16.8%), although no comparable data from observer programmes were available.

Although a ‘prohibited’ species, there were reported landings of the D. batis-complex, indicated in both landings and observer data (Table 2.9). Small quantities of A. radiata were reported in the landings, although this species is generally discarded (see below).

Table 2.4: Species composition of skates (Rajidae) in UK fisheries operating in the Irish Sea based on reported landings and Cefas observer programme (retained species only)

Gill and Nephrops trawl Otter trawl tangle nets Species name Reported landings Observer data Reported landings Reported landings Observer data 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 A. radiata - - <0.1 ------D. batis - 0.8 ------0.1 - - - - L. naevus 1.2 0.3 0.9 4.0 - 8.6 - - - 0.0 0.1 0.9 - - - R. brachyura 1.1 0.2 2.0 - - - 14.0 0.1 0.1 1.2 3.3 12.6 0.1 - - R. clavata 97.7 98.6 96.7 90.2 100 88.4 86.0 99.9 99.9 98.8 94.6 81.4 99.8 100 99.4 R. microocellata ------0.1 - - - R. montagui - <0.1 0.4 5.9 - 3.0 - - - - 2.0 5.0 0.1 - 0.6 TOTAL 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

Table 2.5: Species composition of skates (Rajidae) in UK fisheries operating in the Bristol Channel based on reported landings and Cefas observer programme (retained species only)

Beam trawl Gill and tangle nets Otter trawl Species name Reported landings Observer data Reported landings Observer data Reported landings Observer data 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 A. radiata 0.2 ------<0.1 - - - - - D. batis 1.5 - - - - - 4.4 <0.1 <0.1 - - - 1.3 - - - - - D. nidarosiensis ------<0.1 - - - - - D. oxyrinchus ------<0.1 ------L. circularis 1.5 0.5 0.1 - - - 1.3 2.6 - - - - 4.1 2.0 2.8 - - - L. fullonica 0.6 - <0.1 - - - - 2.9 3.8 - - - 0.7 1.0 0.1 - - - L. naevus 24.1 28.5 22.8 19.1 14.4 13.5 27.7 11.8 9.5 17.2 0.4 - 1.5 0.4 0.3 0.2 0.4 0.1 R. brachyura 50.8 45.8 35.3 74.0 35.6 78.6 62.0 43.7 28.4 0.6 89.7 - 28.2 23.7 32.4 24.3 16.3 49.3 R. clavata 6.3 5.2 15.0 - - - 0.6 23.0 27.3 42.5 - 45.8 30.4 31.8 33.5 18.5 20.4 36.0 R. microocellata 7.6 9.4 12.2 3.4 25.6 2.4 3.9 15.2 30.3 34.1 9.1 54.2 30.5 35.9 27.8 51.5 59.2 13.4 R. montagui 7.4 10.6 14.5 3.5 24.4 5.5 - 0.8 0.7 5.6 0.8 - 3.3 5.2 3.2 5.5 3.8 1.1 TOTAL 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

Table 2.6: Species composition of skates (Rajidae) in UK fisheries operating in the Celtic Sea, based on reported landings and Cefas observer programme (retained species only)

Beam Trawl Gill and tangle nets Otter trawl Species name Reported landings Observer data Reported landings Observer data Reported landings Observer data 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 A. radiata 0.5 0.6 0.3 ------D. batis 7.7 0.5 - 18.3 - - 25.1 <0.1 - - - - 4.0 - - - - - D. nidarosiensis ------20.6 2.8 <0.1 - - - D. oxyrinchus 0.4 - <0.1 - - - - 1.2 0.5 - - - 11.0 5.3 - - - - L. circularis 2.9 1.0 0.1 - - - 3.0 - - - - - 0.1 1.8 0.1 - - - L. fullonica 1.4 1.7 0.7 6.2 4.6 15.0 - 0.2 6.0 - - 23.0 5.6 15.0 30.1 - - - L. naevus 72.9 78.8 77.0 73.7 93.2 82.6 37.7 41.6 22.2 4.5 90.9 59.7 30.3 47.7 46.6 0.1 - 0.2 R. brachyura 4.7 5.6 5.3 <0.1 - - 20.3 22.1 4.4 3.0 - 0.5 8.8 4.7 4.4 60.4 8.8 37.3 R. clavata 4.5 5.7 6.4 1.3 0.6 - 3.0 9.0 28.8 46.9 - 0.4 14.1 16.6 12.0 12.1 43.1 19.1 R. microocellata 5.1 5.8 8.6 0.3 - - 10.9 21.9 29.2 44.6 - - 4.8 5.5 5.7 25.5 41.8 40.3 R. montagui <0.1 0.4 1.6 0.1 1.7 2.4 - 4.0 9.0 1.0 9.1 16.4 0.1 0.7 1.2 1.9 6.3 3.0 R. alba ------0.6 - - - - - TOTAL 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

Table 2.7: Species composition of skates (Rajidae) in UK fisheries operating in the western English Channel, based on reported landings and Cefas observer programme (retained species only)

Beam Trawl Gill and tangle nets Otter trawl Species name Reported landings Observer data Reported landings Observer data Reported landings Observer data 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 A. radiata 1.7 - - - - - 0.2 <0.1 <0.1 - - - 0.4 <0.1 <0.1 - - - D. batis 5.0 <0.1 - 2.6 - - 4.3 0.1 - - - - 0.3 0.1 - - - - D. nidarosiensis ------<0.1 - - - D. oxyrinchus - - <0.1 - - - <0.1 - 0.1 - - - - - <0.1 - - - L. circularis 0.3 <0.1 0.2 - - - - 0.1 0.2 - - - 0.1 0.2 <0.1 - - - L. fullonica 0.3 0.2 0.1 - - 0.3 - 0.1 0.3 - - - - 0.3 0.2 0.9 - - L. naevus 32.8 28.4 37.9 6.0 14.4 15.6 49.3 24.0 21.4 57.8 71.2 66.3 32.4 7.2 9.2 23.4 29.9 50.7 R. brachyura 29.7 48.7 46.7 60.3 75.9 66.1 38.2 47.5 35.1 - 15.7 20.9 60.0 50.9 43.9 28.3 22.7 13.0 R. clavata 4.3 8.7 3.0 6.6 2.4 7.5 4.1 24.5 28.8 20.0 9.6 6.3 0.9 29.2 19.1 5.3 6.9 5.9 R. microocellata 3.0 4.3 2.9 5.6 0.5 4.9 3.8 2.3 9.7 6.0 1.9 1.6 6.0 6.2 7.5 10.9 10.1 8.9 R. montagui 18.8 7.6 9.1 5.2 6.8 5.6 <0.1 1.4 4.4 16.2 1.5 4.9 0.1 5.8 20.0 27.7 23.0 21.4 R. undulata 4.2 2.1 - 13.7 ------0.1 - 3.6 7.4 - R. alba ------<0.1 - - - - <0.1 - - - - TOTAL 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

Table 2.8: Species composition of skates (Rajidae) in UK fisheries operating in the southern North Sea and eastern English Channel, based on reported landings and Cefas observer programme (retained species only)

Beam trawl Gill and tangle net Otter trawl Species name Reported landings Observer data Reported landings Observer data Reported landings Observer data 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 2008 2009 2010 A. hyperborea - 1.0 3.0 - - - - - <0.1 ------D. batis - <0.1 - - - - 0.3 - 0.3 ------D. oxyrinchus ------0.8 <0.1 1.0 - - - <0.1 - <0.1 - - - L. circularis ------<0.1 ------L. fullonica ------<0.1 <0.1 0.1 - - - - - <0.1 - - - L. naevus - 0.3 0.3 - - - - <0.1 <0.1 ------R. brachyura 30.8 29.6 26.2 66.8 24.5 30.1 6.4 12.5 8.6 1.2 0.4 - 4.6 3.4 1.8 - 5.1 18.9 R. clavata 46.2 53.0 55.9 33.2 73.4 60.1 90.5 84.2 86.8 97.1 99.4 100.0 94.5 95.4 97.6 100.0 39.9 72.0 R. microocellata 4.2 2.0 0.4 - - 3.7 - 1.4 1.0 1.7 - - 0.1 0.3 0.2 - 16.7 1.2 R. montagui 15.7 13.7 14.1 - 2.1 6.1 0.1 1.6 2.3 - 0.3 - 0.6 0.7 0.2 23.1 7.9 - R. undulata 3.1 0.4 - - - - 1.9 0.1 - - - - 0.1 0.1 - - 15.3 - R. alba ------0.1 ------<0.1 - - - TOTAL 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100

Table 2.9: Species composition of skates (Rajidae) in UK fisheries operating in the southern North Sea and eastern English Channel (longline), and central and northern North Sea (beam and otter trawl), based on reported landings and Cefas observer programme (retained species only)

Southern North Sea and eastern English Channel Central and northern North Sea Longline Beam trawl Otter trawl Species name Reported landings Observer data Reported landings Reported landings Observer data 2008 2009 2010 2008 2008 2009 2010 2008 2009 2010 2008 2009 2010 A. hyperborea - - <0.1 - - - 2.3 - <0.1 - - - - A. radiata ------<0.1 <0.1 1.1 - 4.3 D. batis - - 3.3 - - - - <0.1 - 0.3 - - 2.1 D. oxyrinchus ------3.2 - L. naevus - - - - 0.1 - 1.0 0.3 2.3 4.1 6.9 3.3 9.4 R. brachyura 17.4 5.6 15.2 - 10.8 16.3 23.2 0.5 0.3 2.7 2.5 0.2 2.7 R. clavata 79.3 93.8 80.9 99.4 36.1 24.4 36.8 86.8 92.2 89.5 65.7 80.9 30.6 R. microocellata - 0.3 0.4 - <0.1 0.1 - - 0.4 - - - - R. montagui 3.2 0.3 0.1 0.6 52.9 59.3 36.6 12.4 4.7 3.4 23.8 12.3 50.9 R. undulata <0.1 - - -

TOTAL 100 100 100 100 100 100 100 100 100 100 100 100 100

2.4 Discard-retention patterns

Beam trawlers caught proportionally more small skates than the other gears, followed by small-mesh gillnets (90–150 mm mesh size), otter and Nephrops trawls. While larger gillnets (200–256 mm mesh size) caught proportionally more large skates (Figure 2.2).

Figure 2.2: Cumulative size frequency of all skates (Rajidae) caught by broad category of fishing gear, as observed in the Cefas observer programme (2002–2010).

The high proportion of small skates caught in beam trawlers (<120 mm mesh size) were generally discarded (Figure 2.3a). First retention was at approximately 27 cm LT, with nearly all skates retained at ≥61 cm LT. The length at 50% retention was about 50–51 cm LT.

Otter trawlers (80–130 mm mesh size) captured proportionally more large skates, which were retained from about 27–30 cm LT (Figure 2.3b), with 50% retention at about 50 cm and near-full retention at 62 cm LT. A high proportion of the skates caught by Nephrops trawlers (80–110 mm mesh size) were small, with skates generally retained from 35 cm, 50% retention at 49–50 cm and near-full retention ≥62 cm LT (Figure 2.3c).

Gillnet fisheries landed skates ≥46 cm, and full retention occurred at >60 cm LT, with smaller-mesh gillnets (≤150 mm mesh size, Figure 2.3e) invariably capturing a greater proportion of small skates in comparison with larger gillnets (>150 mm mesh size, Figure 2.3f).

Figure 2.3: Length-frequency of discarded (grey columns) and retained (black columns) commercial skates (excluding D. batis-complex and R. undulata) by (a) beam trawl, (b) otter trawl, (c) Nephrops trawl, (d) gillnets (all), (e) gillnets ≤150 mm mesh size and (f) gillnets >150 mm mesh size, as recorded in the Cefas observer programme.

In general, the main commercial skate species were retained from lengths of 27–34 cm, and 50% retention occurred at 49–51 cm LT. Nearly all skates were retained at 60–67 cm LT (Figure 2.4). Although data were more limited for L. fullonica than for other species, there was a tendency for the lengths at first and 50% retention (48 and 53 cm, respectively) to be slightly higher than for other species.

Other rajid species (D. oxyrinchus, D. nidarosiensis, A. radiata, L. circularis and R. fyllae) were also recorded during the discard observer programme. A. radiata was

30 the most abundant of these, and was generally discarded across the entire length range (12–69 cm LT).

Figure 2.4: Length-frequency of discarded (grey columns) and retained (black columns) (a) R. clavata, (b) L. naevus, (c) R. brachyura, (d) R. montagui, (e) L. fullonica and (f) R. microocellata (all gear types, 2002–2010), as recorded in the Cefas observer programme.

Of the three skate species that are currently listed as prohibited species, some data were available for R. undulata and D. batis-complex, and only limited data were available for R. alba. Marketable sized fish of both species were typically retained prior to their prohibited status in 2009 (Figures 2.5a,c and 2.6a,c), and observer data since then indicated that both species are usually discarded, with only occasional specimens retained (Figures 2.5b,d and 2.6b,d).

Figure 2.5: Length-frequency of discarded (grey columns) and retained (black columns) Raja undulata captured by beam trawl for the periods (a) 2002–2008 and (b) 2009–2010, and by otter trawl for the periods (c) 2002–2008 and (d) 2009– 2010, as recorded in the Cefas observer programme.

Figure 2.6: Length-frequency of discarded (grey columns) and retained (black columns) Dipturus batis-complex captured by beam trawl for the periods (a) 2002– 2008 and (b) 2009–2010, and by gillnet for the periods (c) 2002–2008 and (d) 2009–2010, as recorded in the Cefas observer programme.

2.5 Discarding rates: A broadscale analysis

The Cefas Observer Programme has monitored catches of fishing vessels registered in England and Wales consistently since 2002. Scientific at-sea observers currently sample 200 trips and 1200 hauls each year on English and Welsh vessels, in which approximately 350,000 fish are measured, representing around 0.5% of the total fishing effort (in terms of fishing days).

The Cefas Observer Programme is target driven whereby a number of trips per vessel-gear-area combinations are sampled per quarter. The main metiers for which samples are collected are given in Table 2.10. These metiers contribute 95% of discards (and landings) quantities. The species, gear types, and areas sampled in the observer programme are determined by EU Data Collection Framework (DCF) requirements (1639/2001 and 199/2008).

The participation by skippers in the observer programme is voluntary; vessels are selected randomly. Once at sea, the sampling scheme is a multistage process whereby the composition of discards and retained components are estimated for each haul, and typically >60% of hauls are sampled during a trip. Numbers-at-length for fish are raised to haul, then to trip, and length–weight relationships were applied to estimated weights.

The estimated number and weight of retained and discarded fish from the sampled hauls were raised to trip totals, which were then raised by the effort exerted by each gear category in each area defined in Table 2.10. Annual discard rates were then calculated by each gear category (Table 2.11; and see figures in Annex V).

Table 2.10: Categories of gear type used in estimating quantities of discards, and fishing grounds examined

Gear description over 10 m beam trawlers targeting brown shrimp (20mm mesh) (TBB_CRU) under 10 m beam trawlers targeting brown shrimp (20mm mesh) (TBB_CRU) over 10 m beam trawlers targeting fish and cephalopods (TBB_DEF) over 10 m gill netters (GNS_DEF) under 10 m gill netters (GNS_DEF) over 10 m Nephrops trawlers (OTB_CRU) under 10 m Otter trawlers targeting Nephrops (OTB_CRU) over 10 m Otter trawlers (OTB_DEF) over 10 m Otter trawlers (DEF_OTB) Area descriptions ICES Sub-area IV and Division VIId ICES Division VIIa ICES Divisions VIIfgh ICES Division VIIe

Table 2.11: Estimated average discard rates (averaged across years and areas) of skates for the main gear categories for which discard data were available

Mean annual discard rate Gear category Species as % of catch weight (± sd) Beam trawl (targeting fish and R. montagui 57 (± 18) cephalopods, and over 10 m) R. undulata 48 (± 42) L. naevus 47 (± 20) D. batis-complex 36 (± 35) R. microocellata 27 (± 27) R. clavata 24 (± 22) L. fullonica 21 (± 24) R. brachyura 14 (± 16) Gill & trammel nets (over 10 m) D. batis-complex 47 (± 46) R. clavata 36 (± 32) L. naevus 20 (± 14) R. brachyura 19 (± 38) R. montagui 19 (± 27) L. fullonica 12 (± 21) Gill & trammel nets (under 10 m) R. montagui 28 (± 20) R. brachyura 17 (± 37) R. clavata 8 (± 10) L. naevus 7 (± 10) R. microocellata 0 (± 0) Nephrops trawl (over 10 m) R. montagui 41 (± 42) L. naevus 35 (± 43) R. clavata 16 (± 7) R. brachyura 0 (± 0) Nephrops trawl (under 10 m) L. naevus 50 (± 71) R. clavata 39 (± 34) Otter trawl (over 10 m) D. batis-complex 46 (± 52) L. naevus 41 (± 27) R. montagui 36 (± 25) R. clavata 21 (± 23) R. undulata 19 (± 20) L. fullonica 17 (± 33) R. brachyura 8 (± 13) R. microocellata 8 (± 8) Otter trawl (under 10 m) R. undulata 50 (± 71) R. clavata 39 (± 38) R. montagui 38 (± 37) L. naevus 32 (± 34) R. microocellata 28 (± 34) R. brachyura 17 (± 13)

2.6 Discards rates: Estimating levels of discarding

The species composition of discarded and retained rajids for the main fisheries for which observer data were available were analysed in order to calculate the proportion of biomass discarded in relation to the retained biomass. The quantities discarded were expressed as a proportion of the retained catch (by area/gear) for the years 2008–2010, and then the mean discarded biomass (across these three years) calculated (Tables 2.12–2.16). These data need to be viewed in the context of the many factors that can influence discarding practices, including quota allocation, bycatch quotas and the marketability of the skates caught by the various gears.

Dipturus batis-complex and Raja undulata, which are currently listed as ‘prohibited species’, were mainly discarded, with only a few specimens retained by otter trawl in the western English Channel (Table 2.13b). A high proportion of R. undulata was discarded in the western English Channel by beam trawlers for 2009–2010, and R. undulata are known to be locally abundant in parts of this area.

Otter trawlers in the Bristol Channel showed a low proportion of discarding for larger skate species, including R. brachyura, R. clavata and R. microocellata, for which the quantities discarded were approximately 10–17% of the retained biomass. In contrast, discarding was more of an issue for R. montagui, for which discards accounted for approximately 85% of the amounts retained (Table 2.14).

Despite their commercial importance, a high proportion of R. clavata were discarded by beam trawlers in the southern North Sea and eastern English Channel. Beam trawlers are known to catch proportionally more small skates (see above), which may partly explain the relatively low biomass of R. clavata retained in comparison to the high proportion discarded (Table 2.16a). However, other issues, including bycatch quotas and quota allocation, may also influence discard rates of commercial species.

For the five main commercial skate species, the quantities of discards (based on the proportion discarded each year in the time series, as estimated from the Cefas observer programme) were raised in relation to the officially reported landings for the species taken each year in the main fisheries (Table 2.17–2.21). These are considered preliminary estimates, as some observer data were based on comparatively few trips. These results suggested that there may be high levels of discarding of L. naevus in the Celtic Sea (beam and otter trawl, Table 2.17) and R. clavata in the southern North Sea/eastern English Channel (otter and beam trawl, Table 2.18). High proportions of R. montagui were also discarded. In contrast, only low quantities of Raja brachyura and R. microocellata were discarded. Small R. microocellata tend to occur in shallow areas (Ellis et al., 2005a,b), and such habitats may be outside the main trawling grounds, and this may influence the low discarding rates observed here.

Obviously, estimates of discards for each species in the various fisheries cannot be simply added to reported catch to determine total fishing mortality, as for many of these fisheries there will be some degree of discard survival (see section 3), and this is discussed further in Section 4.

Table 2.12: Proportion of discarded and retained skates (by species) in Irish Sea fisheries using (a) otter trawl and (b) Nephrops trawl (2008–2010). Data given in terms of individuals (ind.) and biomass (kg)

2008 2009 2010 average % Discarded Retained Discarded Retained Discarded Retained discarded Biomass Biomass Biomass Biomass Biomass Biomass Otter trawl Ind. Ind. Ind. Ind. Ind. Ind. biomass (kg) (kg) (kg) (kg) (kg) (kg) L. naevus 41.8 29.3 ------100.0 R. brachyura - - 1 1.5 ------0 R. clavata 360 196.5 777.9 1717.5 94 24.7 121 249.6 553.6 198.2 384.3 578.0 18.5 R. montagui - - 1 2.0 4 0.9 - - 10.75 0.3 2 3.8 35.9 average % Biomass Biomass Biomass Biomass Biomass Biomass Nephrops trawl Ind. Ind. Ind. Ind. Ind. Ind. discarded (kg) (kg) (kg) (kg) (kg) (kg) biomass L. naevus - - 6 6.5 - - - - 5.5 5.8 7 6.4 45.9 R. clavata 75.5 28.3 79 147.4 60.1 15.0 25 46.8 81.2 69.8 33 65.2 52.8 R. montagui 10.2 4.4 8 9.6 - - - - 1 0.1 1 2.2 25.1

Table 2.13: Proportion of discarded and retained skates (by species) in western English Channel fisheries using (a) beam trawl, (b) otter trawl and (c) gillnet (2008–2010) 2008 2009 2010 average % Discarded Retained Discarded Retained Discarded Retained Beam trawl discarded Biomass Biomass Biomass Biomass Biomass Ind. Ind. Biomass (kg) Ind. Ind. Ind. Ind. biomass (kg) (kg) (kg) (kg) (kg) D. batis 12 2.0 3 10.0 23 12.4 ------60.0 L. fullonica - - - - 7 1.6 - - - - 1 1.7 50.0 L. naevus 79.5 26.3 16 23.1 573 153.7 60 86.4 261 92.9 58 85.7 133.5 R. brachyura 11 2.5 66 230.3 152 42.9 228 455.0 28.5 10.0 143 362.9 4.4 R. clavata 199 73.8 8 25.0 96 35.0 4 14.2 - - 29 41.3 180.2 R. microocellata - - 9 21.5 8 2.7 2 3.0 4 1.7 8 26.6 32.0 R. montagui 175 42.0 18 19.9 140 55.8 32 40.6 49.5 23.1 28 30.8 141.0 R. undulata 31 17.5 19 52.2 167 140.2 - - 177 123.6 - - 77.9 average % Biomass Biomass Biomass Biomass Biomass Otter trawl Ind. Ind. Biomass (kg) Ind. Ind. Ind. Ind. discarded (kg) (kg) (kg) (kg) (kg) biomass D. batis 1 0.2 ------100.0 L. fullonica 8 7.0 5 7.7 - - - - 3.75 0.4 - - 95.5 L. naevus 599 239.5 144 200.2 31 14.2 69 78.5 371.1 194.9 207 232.0 73.9 R. brachyura 112 15.9 88 242.0 3 0.6 19 59.7 54 22.5 10 59.6 15.1 R. clavata 144 36.3 66 45.0 54.5 16.3 9 18.0 196.5 86.5 21 27.1 163.3 R. microocellata 16 26.4 36 93.1 1 0.1 9 26.6 2 1.0 20 40.6 10.3 R. montagui 255 80.4 195.5 236.6 89.1 38.2 44.5 60.5 361.8 160.2 82 98.0 86.9 R. undulata 4 1.9 9 31.0 1 2.5 3 19.5 - - - - 9.5 average % Biomass Biomass Biomass Biomass Biomass Gillnet Ind. Ind. Biomass (kg) Ind. Ind. Ind. Ind. discarded (kg) (kg) (kg) (kg) (kg) biomass D. batis ------1 4.4 - - 100.0 L. naevus 4 6.7 7 12.4 19 18.6 122 191.7 13 12.1 102 163.2 23.6 R. brachyura 2 5.6 - - - - 8 42.3 - - 10 51.4 33.3 R. clavata 1 0.7 1 4.3 - - 6 25.9 3 0.8 4 15.5 7.2 R. microocellata - - 1 1.3 - - 1 5.1 - - 1 4.1 0.0 R. montagui 1 0.5 2 3.5 1 0.7 3 4.1 1 0.8 6 11.9 12.0 R. undulata ------1 7.8 - - 100.0

Table 2.14: Proportion of discarded and retained skates (by species) in Bristol Channel fisheries using (a) beam trawl, (b) otter trawl and (c) gillnet (2008–2010)

2008 2009 2010 average % Discarded Retained Discarded Retained Discarded Retained Beam trawl discarded Biomass Biomass Biomass Biomass Biomass Biomass Ind. Ind. Ind. Ind. Ind. Ind. biomass (kg) (kg) (kg) (kg) (kg) (kg) L. naevus 165 75.2 208.7 203.4 6 4.0 7 8.0 43 32.2 67 75.2 43.2 R. brachyura 73 33.8 289.4 787.4 115 44.1 13 19.8 97 25.5 158 438.4 77.8 R. microocellata - - 24.3 35.7 10 4.1 10 14.2 24 19.6 6 13.6 57.9 R. montagui 48 24.8 41 37.8 154 24.5 13 13.6 79 16.5 22 30.4 100.2 average % Biomass Biomass Biomass Biomass Biomass Biomass Otter trawl Ind. Ind. Ind. Ind. Ind. Ind. discarded (kg) (kg) (kg) (kg) (kg) kg) biomass L. naevus 7 5.4 10 12.3 60 35.3 18 21.1 4 1.5 12 14.3 73.9 R. brachyura 267 130.2 457.3 1388.3 387 138.1 268 839.4 648.5 230.2 1971 4727.3 10.2 R. clavata 340 133.1 453.2 1052.3 188 81.9 406 1054.8 2549.8 1075.5 1825 3450.2 17.2 R. microocellata 722 378.4 1290 2936.2 623 492.4 1245 3054.6 247.5 117.8 683.5 1283.5 12.7 R. montagui 647 326.3 258.5 313.1 320 141.3 117 193.7 187.5 83.1 89 108.6 84.6 average % Biomass Biomass Biomass Biomass Biomass Biomass Gillnet Ind. Ind. Ind. Ind. Ind. Ind. discarded (kg) (kg) (kg) (kg) (kg) (kg) biomass L. naevus 21 26.4 61 108.7 1 0.9 2 3.3 - - - - 26.3 R. brachyura 1 7.5 1 3.6 3 24.1 120 734.5 - - - - 105.3 R. clavata 3 6.8 94 269.0 - - - - 1 1.1 2 3.6 16.7 R. microocellata - - 63 215.5 - - 26 74.5 - - 1 4.2 0.0 R. montagui 1 1.9 19 35.5 5 3.7 4 6.7 - - - - 29.9

Table 2.15: Proportion of discarded and retained skates (by species) in Celtic Sea fisheries using (a) beam trawl, (b) otter trawl and (c) gillnet (2008–2010)

2008 2009 2010 average % Discarded Retained Discarded Retained Discarded Retained Beam trawl discarded Biomass Biomass Biomass Biomass Biomass Biomass Ind. Ind. Ind. Ind. Ind. Ind. biomass (kg) (kg) (kg) (kg) (kg) (kg) D. batis 56.5 14.2 144.5 639.3 32 46.5 - - 72 158.1 - - 67.4 L. fullonica 249 35.6 101 217.7 26 8.0 32 70.1 38 17.0 25 68.0 17.6 L. naevus 3206 1038.2 2159 2574.9 652 231.6 1098 1427.6 678 178.5 379 375.4 34.7 R. brachyura - - 1 1.5 3 0.1 ------50.0 R. clavata 10 3.3 18 46.4 - - 3 8.5 - - - - 3.6 R. microocellata 4 0.8 4 9.1 ------8.4 R. montagui 45 10.0 5 5.1 95.5 36.9 19 25.5 16 9.4 8 10.9 143.3 average % Biomass Biomass Biomass Biomass Biomass Biomass Otter trawl Ind. Ind. Ind. Ind. Ind. Ind. discarded (kg) (kg) (kg) (kg) (kg) (kg) biomass L. naevus 3 2.5 2 2.7 - - - - 86 55.8 7 8.2 386.3 R. brachyura 44 22.6 452.5 1580.3 10 7.9 15 60.0 301 146.3 706.8 1531.4 8.1 R. clavata 107 60.7 178.5 317.2 57 25.1 140 293.9 323 175.4 415.3 784.3 16.7 R. microocellata 54 32.2 285 667.3 19 9.1 134 284.4 120 63.9 805.5 1656.1 4.0 R. montagui 121 52.3 38 50.3 125 49.8 31 42.9 324 154.0 109.3 124.5 114.5 average % Biomass Biomass Biomass Biomass Biomass Biomass Gillnet Ind. Ind. Ind. Ind. Ind. Ind. discarded (kg) (kg) (kg) (kg) (kg) (kg) biomass D. batis - - - - 3 42.1 - - 26 174.2 - - 100.0 L. fullonica ------18 32.6 38 112.9 28.8 L. naevus 15 17.4 43 64.7 11 16.5 14 24.1 31 57.3 171 292.6 38.3 R. brachyura 9 14.9 27 42.4 ------1 2.4 17.6 R. clavata 17 30.4 281 672.9 - - - - 2 2.9 1 1.8 84.8 R. microocellata 1 2.2 225 640.0 ------0.3 R. montagui 4 3.8 9 13.9 2 3.9 1 2.4 6 8.4 42 80.5 67.1

Table 2.16: Proportion of discarded and retained skates (by species) in southern North Sea and eastern English Channel fisheries using (a) beam trawl, (b) otter trawl and (c) gillnet (2008–2010)

2008 2009 2010 average % Discarded Retained Discarded Retained Discarded Retained Beam trawl discarded Biomass Biomass Biomass Biomass Biomass Ind. Ind. Ind. Ind. Ind. Ind. Biomass (kg) biomass (kg) (kg) (kg) (kg) (kg) R. brachyura 19 9.6 8 24.2 - - 17 36.5 312 110.3 20 74.1 62.8 R. clavata 299 80.5 6 12.1 484 148.9 104 109.4 1254.9 265.6 71 147.7 327.9 R. microocellata ------12.7 8.3 4 9.1 91.1 R. montagui 8 3.4 - - 14 3.9 2 3.2 77.75 26.8 11 15.0 134.6 R. undulata ------39.7 6.4 - - 100.0 Skate (indet.) ------5.5 0.3 - - 100.0 average % Biomass Biomass Biomass Biomass Biomass Otter trawl Ind. Ind. Ind. Ind. Ind. Ind. Biomass (kg) discarded (kg) (kg) (kg) (kg) (kg) biomass R. brachyura - - - - 11 3.2 2 2.2 36.5 17.8 8 29.3 102.2 R. clavata 509 116.4 37 104.6 265 28.8 8 17.5 2368.0 317.7 47 111.3 187.1 R. microocellata - - - - 2 0.9 4 7.3 3 1.0 1 1.8 34.0 R. montagui ------7 10.2 42 24.1 8 12.2 98.3 R. undulata - - - - 8 3.6 1 6.7 5 9.9 - - 76.8 average % Biomass Biomass Biomass Biomass Biomass Gillnet Ind. Ind. Ind. Ind. Ind. Ind. Biomass (kg) discarded (kg) (kg) (kg) (kg) (kg) biomass R. brachyura - - 1 3.0 - - 1 2.0 - - - - 0.0 R. clavata 98 46.4 90 250.9 297 135.4 243 542.9 48 24.1 10 27.2 44.0 R. microocellata - - 1 4.4 ------0.0 R. montagui 1 0.2 - - - - 1 1.5 3 0.6 - - 66.7 R. undulata - - - - 18 20.0 ------100.0

Table 2.17: Estimated discards of Leucoraja naevus for the reported landings by gear and area (2008-2010)

Reported landings (t) Estimated discards (t) Area Gear 2008 2009 2010 2008 2009 2010 BT 2.7 6.4 5.6 1.0 3.2 2.4 Bristol Channel GN 3.8 8.6 10.0 0.9 2.4 - OT 3.4 1.4 1.7 1.5 2.4 0.2 BT 90.7 104.1 100.6 36.6 16.9 47.8 Celtic Sea GN 2.6 4.1 8.6 0.7 2.8 1.7 OT 12.2 28.3 64.7 11.1 - 440.6 OT <0.01 <0.1 0.3 <0.01 - - Irish Sea NT 0.7 0.2 0.8 0 - 0.8 Southern North Sea and BT - 0.2 0.2 - - - eastern English Channel GN - <0.1 <0.1 - - - BT 6.5 15.7 33.2 7.4 27.9 36.0 Western English Channel GN 13.1 25.6 26.3 7.0 2.5 1.9 OT 8.8 11.0 27.1 10.5 2.0 22.8

Table 2.18: Estimated discards of Raja clavata for the reported landings by gear and area (2008-2010)

Reported landings (t) Estimated discards (t) Area Gear 2008 2009 2010 2008 2009 2010 BT 0.7 1.2 3.7 - - - Bristol Channel GN 0.1 16.8 29.0 <0.01 - 9.0 OT 67.6 102.9 162.4 8.6 8.0 50.6 BT 5.5 7.5 8.3 0.4 0.0 - Celtic Sea GN 0.2 0.9 11.4 <0.01 - 18.9 OT 13.0 17.9 23.2 2.5 1.5 5.2 GN 2.8 16.7 9.5 - - - Irish Sea NT 58.6 71.6 91.0 11.2 23.0 97.5 OT 49.8 49.7 30.2 5.7 4.9 10.3 BT 7.0 30.5 32.5 46.4 41.5 58.5 Southern North Sea and GN 45.6 79.9 131.8 8.4 19.9 116.7 eastern English Channel OT 90.2 122.4 125.5 100.4 201.4 358.1 BT 0.9 4.8 2.6 2.5 11.8 0.0 Western English Channel GN 1.1 26.2 35.3 0.2 0.0 1.7 OT 0.2 44.7 56.3 0.2 40.4 179.3

Table 2.19: Estimated discards of Raja brachyura for the reported landings by gear and area (2008-2010)

Reported landings (t) Estimated discards (t) Area Gear 2008 2009 2010 2008 2009 2010 BT 5.6 10.2 8.8 0.2 22.8 0.5 Bristol Channel GN 8.5 32.0 30.2 17.6 1.0 - OT 62.8 76.8 157.1 5.9 12.6 7.7 BT 5.9 7.4 6.9 0.0 7.4 - Celtic Sea GN 1.4 2.1 1.7 0.5 - 0.0 OT 13.9 7.2 9.6 0.2 1.0 0.9 GN 0.5 <0.01 <0.1 - - - Irish Sea NT 0.6 0.2 1.9 - - - OT 0.6 1.7 4.7 0.0 - - BT 4.6 17.0 15.3 1.8 0.0 22.7 Southern North Sea and GN 3.2 11.9 13.0 0.0 0.0 - eastern English Channel OT 4.4 4.3 2.4 - 6.2 1.4 BT 5.9 26.9 40.8 0.1 2.5 1.1 Western English Channel GN 10.2 50.8 43.0 10.2 0.0 0.0 OT 16.3 77.9 129.0 1.1 0.8 48.6

Table 2.20: Estimated discards of Raja microocellata for the reported landings by gear and area (2008-2010)

Reported landings (t) Estimated discards (t) Area Gear 2008 2009 2010 2008 2009 2010 BT 0.8 2.1 3.0 0.0 0.6 4.4 Bristol Channel GN 0.5 11.1 32.2 0.0 0.0 0.0 OT 68.0 116.4 134.9 8.8 18.8 12.4 BT 6.3 7.7 11.3 0.5 - - Celtic Sea GN 0.8 2.1 11.4 <0.01 - - OT 7.8 8.9 14.4 0.4 0.3 0.6 Irish Sea OT - - <0.1 - - - BT 0.6 1.1 0.2 - - 0.2 Southern North Sea and GN 1.3 1.5 - - - eastern English Channel OT 0.1 0.4 0.3 - 0.1 0.2 BT 0.6 2.4 2.6 0.0 2.1 0.2 Western English Channel GN 1.0 2.5 11.9 0.0 0.0 0.0 OT 1.6 9.5 22.0 0.5 <0.1 0.5

Table 2.21: Estimated discards of Raja montagui for the reported landings by gear and area (2008-2010)

Reported landings (t) Estimated discards (t) Area Gear 2008 2009 2010 2008 2009 2010 BT 0.8 2.4 3.6 0.5 4.3 2.0 Bristol Channel GN - 0.6 0.8 - 0.3 - OT 7.3 16.9 15.3 7.6 12.3 11.7 BT 0.1 0.5 2.1 0.1 0.8 1.9 Celtic Sea GN - 0.4 3.5 - 0.7 0.4 OT 0.2 0.9 1.3 0.2 1.0 1.6 NT - <0.01 0.3 - - <0.1 Irish Sea OT - 1.0 1.8 - 1.0 0.1 BT 2.4 7.9 8.2 2.4 9.8 14.7 Southern North Sea and GN 0.1 1.6 3.5 0.1 0.0 3.5 eastern English Channel OT 0.6 0.9 0.3 - 0.0 0.6 BT 3.7 4.2 8.0 7.9 5.8 6.0 Western English Channel GN <0.01 1.5 5.4 <0.001 0.2 0.4 OT <0.1 8.9 58.8 <0.01 5.6 96.2

2.7 Discussion

There has been an increased concern over the status of elasmobranchs, and particularly larger-bodied skates, since Holden (1973) highlighted the biological susceptibility of elasmobranchs, and Brander (1981) documented the loss of the D. batis-complex from the Irish Sea. Nevertheless, the implementation of management has been slow.

Although some UK Sea Fisheries Committees enforced a minimum landing size in coastal waters, the first EC measures were only established in 1999, when a Total Allowable Catch (TAC) for ‘skates and rays’ was fixed for the North Sea. The TAC has since been reduced (typically in the region of 8–25% per year), and the TAC was reduced to a record low of 1,397 t for 2010. Although the TAC has been higher than reported landings for much of this period, quota may have been restrictive for some fisheries, depending on its allocation. For other parts of the ICES area (Divisions IIIa, and sub-areas VI–IX), quotas for skates and rays were only established in 2009.

The introduction of management measures has not only occurred slowly, but for much of the time has been implemented at the family-level, despite there being important species-specific differences in the life history and susceptibility of the various stocks in the skate complex. For example, some of the larger bodied species (D. batis-complex and R. alba) have disappeared from parts of their former range, whilst there may be healthier populations of some of the smaller and more productive stocks, such as A. radiata and R. montagui (Brander, 1981; Walker & Hislop, 1998; Rogers & Ellis, 2000). Some larger skates predate on smaller skates (e.g. Steven, 1932), and some sympatric species may have similar feeding habits (Ellis et al., 1996), and such trophic and competitive interactions may influence the structure and composition of skate assemblages. Nevertheless, to address the increased conservation interest in larger-bodied skates, the EC recently included three skates (D. batis-complex, R. undulata and R. alba) on the list of ‘Prohibited species’ (see CEC, 2011).

2.7.1 Requirements for species-specific landings

One of the major problems for the assessment and management of the different skate species has been that much of the landings data were reported for all species combined (Ellis et al., 2008b,c; ICES, 2010a). Although some skate species may be landed separately in some fisheries, they have traditionally been landed according to ease of processing (skinning) and size, and so species with similar characteristics have often been combined (Fahy, 1989; Holden, 1963). In recent years there have been some national market sampling programmes to better understand the species composition of skates (e.g. Machado et al., 2004; Figueiredo et al., 2007), but no published information were previously available for UK fleets.

Since 2008, TAC and quota regulations have required skates (A. radiata, D. batis- complex, L. naevus, R. brachyura, R. clavata and R. montagui) caught in EC waters of ICES Division IIa and sub-area IV to be reported separately (EC Regulation No. 40/2008). This was extended to other ICES divisions, including the Celtic Seas ecoregion, in 2009, and other species (L. circularis, L. fullonica and R. microocellata) were also to be recorded separately in this region. Although there has been an

44 increase in the proportion of skate landings reported to species level, both in the UK and elsewhere in northern Europe (ICES, 2010a), there are still several issues regarding the accuracy of these data and potential misidentifications and confusion between species.

2.7.2 Comparison of landings data and observer data

The reported skate landings from the main UK fisheries taking skate were more diverse than estimated from the observer programme, in terms of the total number of species retained and landed across gears and divisions. There are several reasons for this discrepancy. There were some probable misidentifications and/or incorrect reporting of some species and also the small proportion of commercial trips that have observers on board may reduce the chance of observing less frequent species. In some areas, there were contrasting spatial distribution in the reported landings and national observer coverage, as discard sampling on foreign-owned, English registered vessels is undertaken by the other country.

Nevertheless, there was usually broad agreement in the main species taken in the fisheries, and observer coverage can be used to inform on the validity (and potential discrepancies) of national landings data. Observer data collected on commercial vessels are normally used to provide information on discarding levels of the main commercial species, but as demonstrated here, such data can also provide valuable information on the size range, spatial and temporal distribution, and species composition of species-complexes. For example, although this study has focused on skates, comparable analyses could be used to better understand the species composition of other fish landed in mixed categories, such as gurnards (Triglidae).

2.7.3 Data quality

It is important to recognise that large datasets (including national landing statistics, observer data and even fishery-independent trawl surveys) need to be subject to appropriate quality control, as potential errors may occur, such as input errors, misidentifications, as well as confusion resulting from regional differences in common names. There may also be confusion between the generic term ‘skate’, which has traditionally been applied by commercial fishermen to all rajids, and the common names of the long-snouted species within the genus Dipturus.

It should also be noted that commercial landings for the trip can be divided pro-rata between the rectangles fished during that trip. Hence, it is possible for fish that were caught in one ICES Division to be partly allocated to another Division, if fishing activities were conducted in both areas.

After the requirements for species-specific recording of landings were introduced, training in species identification (and circulation of species ID sheets) was undertaken by Cefas scientists in several areas. However, this training typically focused on the most common species caught in the area, and so there is some doubt over the accuracy of reports of some less frequently landed species, including for R. alba and the genus Dipturus (ICES, 2010a). Therefore, there is still a need for further training and quality control of the data (e.g. through market sampling programmes).

Analyses of the species composition for the main skate fisheries by geographic region (Tables 2.4–2.9) show some potentially erroneous records that were neither supported by either the known distribution of the species (e.g. Stehmann & Bürkel, 1984; Ellis et al., 2005a) nor corroborated by observer data.

Amblyraja hyperborea was reported in both the central and southern North Sea (Tables 2.8–2.9), although this species is not known to occur in these Divisions (Stehmann & Bürkel, 1984; ICES, 2010a). The related A. radiata was reported in the Irish Sea, Bristol Channel, western English Channel and Celtic Sea (Tables 2.5–2.7), whereas this northerly species occurs mainly to the north of the British Isles and in the northern and central North Sea. These records may represent misidentification of the sympatric R. clavata. Nevertheless, the quantities involved were generally low.

There has long been some confusion between R. brachyura and R. montagui, as these species can occur on the same fishing grounds and have quite similar colourations. There were several instances where the proportions of these two species appeared to be subtly different in national landing statistics and observer data. For example, landings data from Irish Sea Nephrops trawlers indicated a low proportion of R. brachyura (≤2%), although this species was not recorded in observer trips (Table 2.4). In contrast, observer trips indicated a comparable proportion of R. montagui. Similarly, landings and observer data from beam trawl catches in the eastern English Channel and southern North Sea were suggestive of some discrepancy (Table 2.9). Observer data indicated that, on average, R. brachyura and R. montagui accounted for 40.5% and 2.7%, respectively, whereas the corresponding values from landings data were 28.9% and 14.5%.

Although there were instances of potential confusion between these species, it should be recognised that R. brachyura has a patchy distribution (Ellis et al., 2005a). Discrepancies between the two data sets could occur if the temporal and spatial coverage of the observer trips either over or under sampled those fishing grounds where species with patchy distributions and/or high local abundance occur. Hence, the coverage of the observer programme should be accounted for when evaluating the validity of landings data for some species.

ICES has not been able to provide advice for R. brachyura, which can be a locally important commercial species, as catch rates in trawl surveys are both low and variable (ICES, 2010a). Given the similarity in the morphology and colouration of R. montagui and R. brachyura and that there is uncertainty in the accuracy of commercial data further training or market sampling may be required to better estimate the landings of these species.

Other problematic species, for which misidentification with sympatric species may occur include L. fullonica and R. microocellata. Confusion between these skates would explain the contrast in reported landings and observer information from the Bristol Channel (Table 2.5).

Some of the records may also be problematic due to regional variations in common names. For example, ‘sandy ray’ is the widely accepted common name for the offshore species L. circularis, but is also used regionally (e.g. in the Bristol Channel) to refer to small-eyed ray R. microocellata. Therefore, reported landings of L.

46 circularis from the Bristol Channel (Table 2.5) and, to a lesser extent, the western English Channel (Table 2.7) may in fact relate to R. microocellata, which is one of the more frequent skates in those areas. This may also have occurred in the Celtic Sea (Table 2.6), where reports for L. circularis are significantly higher than indicated by observer data, and are more consistent with being R. microocellata. Similarly, both R. microocellata and R. undulata are sometimes called ‘painted ray’, which may also lead to some confusion.

Observer data have the potential to inform on potential identification issues in reported landings, but it should also be recognised that observer data have limited coverage relative to total fishing effort. There can also be important spatial and temporal differences in the skate species composition within both ICES Sub-areas and Divisions, and some elasmobranchs are known to have patchy distributions, and observer data may be limited in some of these fisheries. For example, skates reported by gillnetters operating in the Bristol Channel and Celtic Sea appeared quite variable both between years and between the two data sets. This may be due to the localised nature of some of these fisheries and/or low observer coverage.

Analyses of data collected for foreign-owned, English-registered fishing vessels are required, as there was a paucity of observer data to corroborate reported otter trawl catches in the outer parts of the Celtic Sea. For example, there was an apparent contrast in the landings of L. naevus, L. fullonica and R. microocellata in the Celtic Sea (Table 2.6), where reported landings by otter trawl indicated that these species accounted for, on average, 41.5%, 16.9% and 5.3%, respectively. In contrast, data from the English observer programme reported a small proportion of L. naevus (<1%) and did not record L. fullonica. The distribution of Cefas observer trips was eastwards of the main fishing grounds (Figure 2.1) and analyses of observer data for the Anglo- Spanish fleet are still required.

2.7.4 Prohibited species

In addition to the requirements for species-specific reporting of commercial landings, it is also currently “prohibited for EU vessels to fish for, to retain on board, to tranship or to land” three species of skate D. batis-complex, R. undulata and R. alba (CEC, 2011). This measure has been unpopular with fishermen operating in areas where D. batis-complex or R. undulata are locally common. Reported landings of these species have decreased, in line with these conservation measures, and observer data also demonstrate that these species are now typically discarded. The real extent of recent landings of the D. batis-complex is difficult to quantify, as there can be confusion (and potentially misreporting) with congenerics (D. nidarosiensis and D. oxyrinchus).

Raja undulata accounted for up to 4% of landings in the western English Channel, and up to 2–3% of skate landings in beam trawl and gillnet catches from the eastern English Channel and southern North Sea in 2008, prior to regulations preventing their retention. It should be noted, however, that these proportions were for the regions as a whole, and R. undulata can be locally abundant and one of the dominant rajids in an area covering the eastern part of VIIe and western part of VIId.

Although there were reported landings for the little-known R. alba from the Celtic Sea and English Channel (Tables 2.6–2.8), no voucher specimens or evidence is available, and these data should be treated with caution, as they may result from misidentifications.

2.7.5 Discard-retention patterns

The discard and retention patterns of skates in terms of gear suggested that there were differences in the selection patterns between the various gears. Gillnets with larger (>150 mm) mesh sizes had the lowest discarding of small skates, whilst beam trawlers caught proportionally more small skates, so resulting in high levels of discarding. Otter trawls captured proportionally more larger skates in comparison to beam trawls.

For the main commercial skate species (L. naevus, R. brachyura, R. clavata, R. microocellata, R. montagui), individuals <35 cm LT were usually discarded, and 50% retention occurred at approximately 49–53 cm LT. Nearly all individuals of these species were retained at sizes of >60 cm LT. The discard and retention pattern for R. undulata (prior to their listing as a prohibited species) was similar to the species discussed above, whilst the length at retention was slightly greater for D. batis- complex (Figure 2.6), which would be expected given its longer snout.

Many factors can influence discarding rates and patterns. Smaller skates are not of marketable size or value (or may be subject to a minimum landing size in some inshore areas). Other skates may be discarded because of insufficient quota, prohibited status or state of the fish (e.g. trawl-caught skates can be damaged in the codend; some skates caught in gillnets with a high soak time can be damaged by scavenging isopods etc.), and such factors may account for the occasional incidences of larger fish being discarded. The presence of observers may also influence the discarding practices of fishers.

Despite the requirement for commercial landings data of rajids to be recorded to species level, there is still a need to improve our knowledge of discarding patterns in some fisheries, and also to have a better understanding of potential survivorship.

3. Skate discarding and survival: Recent field investigations

Summary

(1) Field studies on commercial vessels were undertaken to provide a better indication of potential discard survival, with emphasis on gillnetters and beam trawlers.

(2) Skates had a high short-term discard survival when caught by longline, but for those line fisheries with overnight soak times, the damage to the mouth and jaws may compromise longer-term survival.

(3) Skates had a high short-term discard survival when caught by gillnet with short soak times. Short-term survivorship for skates caught in gillnets deployed overnight was approximately 98%, although this decreased to about 88% for soak times of 43–48 hours. These values were taken from field studies in an inshore area with potentially high tidal flows, which may enhance survival.

(4) Skates caught by gillnet on offshore fishing grounds tended to have a higher mortality than inshore gillnet fisheries, although 93% still survived over-night soaks, and 92% survived capture in nets set for 36–60 h. The presence of scavenging isopods may also compromise the survivorship of fish caught in offshore gillnet fisheries in the south-west.

(5) Skates caught by otter trawl in tows of <4 h duration should survive capture in the short-term, depending on the weight and contents of the cod-end, although further studies on longer-term survival are required.

(6) About 50% of skates demonstrated short-term survival following capture by beam trawl, with higher mortality observed for the smallest size category.

(7) Further analyses of tagging data are needed to verify longer-term survival.

3.1 Introduction

There is an important need to have an improved understanding of discarding patterns and discard survivorship, and of the various factors that affect discard mortality, for both stock assessment and fisheries management.

Firstly, estimates of dead discards (individuals and biomass) are required to better quantify total removals from the stock for any future quantitative stock assessments. Secondly, information on the potential survival of discarding is also needed to ensure that the efficacy of potential management measures can be justified, in order that the fishing industry may see both the rationale and potential benefits of returning fish

(e.g. threatened species) to the sea. Thirdly, an appropriate knowledge of discard survival is needed to inform the current debate regarding the contrasting issues of discard bans, full utilisation, technical measures for reducing fishing mortality and animal welfare issues.

Currently, there are several reasons why skates (and other elasmobranchs) may be discarded, including:

 Protected species: Species listed on national wildlife legislation (e.g. the UK Wildlife and Countryside Act) or as prohibited species in EC Regulations have to be returned to the sea. This currently affects the following skate species: white skate Rostroraja alba, common skate Dipturus batis-complex, and undulate ray Raja undulata.

 Juvenile fish: Small individuals of many species may be unmarketable due to the small amount of flesh, or that there may be local bylaws that stipulate a minimum landing size (MLS).

 Limited quota: Depending on the level and allocation of quota, various fisheries may have periods during which quota is restricted, and so fish will be discarded.

 Non-commercial species: Some species are not viewed as marketable, either due to the quality of the flesh, ease of processing or market demand. Examples of this include some of the smaller bodied skates, such as starry ray Amblyraja radiata and round skate Rajella fyllae.

 Mature fish: Although not currently in place for any skates, maximum landing lengths (MLL) were introduced for spurdog Squalus acanthias and porbeagle Lamna nasus to afford protection to larger, mature females.

In some areas, skates that may not be marketable for human consumption may have some value as bait in pot fisheries, which may also influence discarding patterns.

The lack of swim bladders in elasmobranchs, and the robustness of some of these species, may result in relatively good discard survival (e.g. Broadhurst et al., 2006), and the more sedentary nature of skates and some demersal dogfish may enable them to survive better in some fisheries in comparison to those faster swimming sharks and dogfish that are ram ventilators.

To date, few studies have examined the discard survival of batoids (e.g. Kaiser & Spencer, 1995; Stobutzki et al., 2002; Laptikhovsky, 2004, Enever et al., 2009). Discard survivorship of skates will depend on a variety of factors, including the species (e.g. R. clavata has a thicker skin than some other skate species, which may afford some protection from damage), the gear used and its duration/soak time, contents of the net and fisher behaviour (Catchpole et al., 2007; Enever et al., 2009, 2010).

There have been a few studies in recent years to better understand the potential short-term and longer-term discard survival of elasmobranchs taken in British fisheries (Revill et al., 2005; Ellis et al., 2008a; Enever et al., 2009). During the 50 current project, further field studies were conducted to provide additional information on skate species and fisheries of interest, focusing on ‘prohibited species’ (e.g. undulate ray) and fishing gears for which data were previously limited (e.g. beam trawl and gillnet). Additionally, the field work was also able to facilitate further biological studies and data collection (e.g. maturity studies, distribution and stock identity) for some of the lesser-known skate species, so as to provide added value to the work undertaken.

Table 3.1: Summary of field work undertaken during the project MB5202

No. of No. of Fishing elasmobranchs skates held Location Gear Dates vessel tagged and in survival released tank studies Angelle Isle of Gillnets May 2010 118 - Marie Wight Feb/Mar 2011 117 - (SU233) Mar 2011 121 - Nicola May Channel Longline Jul 2010 80 - (GU57) Islands Otter trawl Jan 2011 356 - Barentszee Western Beam Jul 2010 30 27 English trawl Dec 2010 145 18 Channel Lady Lou North coast Beam Feb 2011 9 29 of Cornwall trawl Cornishman South-west Beam Sept 2010 33 21 Approaches trawl Billy Rowney Western Beam Oct/Nov 2010 11 6 English trawl Channel

52.0

51.5

51.0

Lady Lou 50.5 Angelle Marie

Barentszee 50.0

Cornishman Billy Rowney 49.5

Nicola May

49.0

48.5

48.0 -8 -7 -6 -5 -4 -3 -2 -1 0 Figure 3.1: Location of field studies undertaken during the course of the project

3.2 Inshore gillnet studies

A previous study of thornback ray Raja clavata in the southern North Sea included work on two vessels deploying gillnets (Ellis et al., 2008a,b). During the current project, further field studies of gillnet fisheries for skates were conducted off the western parts of the Isle of Wight (ICES Division VIId), an area where R. undulata are known to be locally common. Field investigations (Figure 3.2) were undertaken over the course of three trips conducted in May 2010 and February–March 2011 (two trips).

The gears used throughout these surveys were gillnets of 10.5–12.5” (ca. 266–317 mm) mesh size, and each approximately 300 fathoms (ca. 550 m) long. These were deployed and then left for approximately 24 or 48 hours, which were the normal soak times in this fishery, given the strong tidal currents and amount of seaweed in the area at these times of the year. After each haul, all live skates were tagged with Petersen disc tags and then put into sea water tanks with running water until the gillnet was fully hauled. Any dead skates were recorded and measured. When the vessel was away from any gillnets, the tagged skates were measured (total length and disc width), sexed and released back to the sea. The nets were replaced each day in a slightly different position.

Figure 3.2: Field work on (a) the Angelle Marie, showing (b) hauling the gillnets, (c) skate in a gillnet, (d–e) measuring the total length and disc width of a tagged undulate ray Raja undulata, and (f–g) releasing a tagged thornback ray Raja clavata.

May 2010: Four gillnets were set each of the five days with a total of 20 stations fished in the general area of Sandown Bay (Figure 3.3). This area was selected by the skipper of the Angelle Marie as an area of local abundance of undulate ray as well as other skate species. Latitude, longitude, date, time, water depth (15–18 m) and surface water temperature (11.8–12.3°C) were recorded. Soak time ranged from 19.75–25.4 hours. This soak time was as used commercially at this time of year, as there was weed in the water, and this could foul the nets.

A total of 120 rays were caught (Table 3.2). Species, total length, disc width, sex, maturity (males), and health state (lively, sluggish or dead) were recorded for all rays. 118 fish were tagged with Petersen discs and released. Of these, 101 (84.2%) were considered to be in good condition i.e. lively, and 17 (14.2%) considered to be sluggish. Two fish (1.7%) were dead when hauled, comprising of one thornback ray and one spotted ray. One undulate ray that was tagged on the first day was recaptured approximately half a mile from its release position on the fourth day and found to be in good condition.

Catches were predominantly comprised of larger fish, and although spotted rays of 54–65 cm were caught, only larger size classes of thornback, undulate and blonde ray were caught (Figure 3.4).

Figure 3.3: Location of gillnet studies near Sandown Bay (Isle of Wight) in May 2010

Table 3.2: Species composition, sex ratio and length distributions of all batoids caught whilst gillnetting on the FV Angelle Marie (May 2010).

Spp Males Females Sex ratio Species comp Length Length N N F:M (%) range range Raja clavata 57.5 57 65–85 cm 11 81–90 cm 1:5.3 Raja undulata 27.5 27 80–97 cm 6 79–91 cm 1:4.5 Raja montagui 10.0 9 54–65 cm 2 63–65 cm 1:4.5 Raja microocellata 2.5 2 73–75 cm 1 76 cm - Raja brachyura 1.7 2 87–97 cm 0 - - Dasyatis pastinaca 0.8 - - 1 73 cm - Total 100% 99 21 1:4.3

Frequency 4

0 54 56 58 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 Total length (cm)

R.brachyura R.microocellata R.montagui D.pastinaca R.clavata R.undulata

Figure 3.4: Length distribution and numbers of the six batoid species caught whilst gillnetting on the FV Angelle Marie (May 2010).

February and March 2011: During the period 25 February to 2 March 2011, a total of 19 stations were fished in the general area of Sandown Bay. Fishing was undertaken in waters of 14–22 m depth and surface water temperature was 7.6– 9.0°C. Soak times ranged from 17.0– 47.5 hrs.

A total of 128 skates were caught (Table 3.3), of which seven (5.5%) were dead or near-dead on hauling (comprising five thornback rays and two spotted rays), 52 (40.6%) were considered to be in good condition, and 69 (53.9%) were categorised as sluggish. Catches also included recaptures of four tagged fish, three that were tagged in the same area in May 2010, and one tagged earlier in the trip. Once again, catches were comprised of larger fish and males (Table 3.3; Figure 3.5).

Of the fish caught in shorter soak times (17–27.75 hrs), similar proportions of fish were lively (n=38, 48.1%) and sluggish (40, 50.6%) and only a single fish (1.3%) was dead. Longer soak times (42.9–47.5 hrs) resulted in an increased quantity of dead fish (n=6, 12.2%), and more fish were sluggish (n=29, 59.2%) than lively (n=14, 28.6%).

Table 3.3: Species composition, sex ratio and length distributions of all batoids caught whilst gillnetting on the FV Angelle Marie (Feb/March 2011).

Spp Males Females Sex ratio Species comp Length N Length N F:M (%) range range Raja clavata 77.2 81 61–87 cm 17 56–89 cm 1:4.8 Raja montagui 15.7 9 55–59 cm 11 48–66 cm 1:0.8 Raja undulata 5.5 6 90–93 cm 1 100 cm 1:6 Raja microocellata 1.6 2 67–72 cm 0 - - Total 100% 99 21 1:4.7

Frequency 4

0 45 50 55 60 65 70 75 80 85 90 95 100 Total length (cm)

R. microocellata R. montagui R. clavata R. undulata

Figure 3.5: Length distribution and numbers of the four batoid species caught whilst gillnetting on the FV Angelle Marie (Feb/Mar2011).

A subsequent trip was undertaken on the next set of appropriate tides (10– 15 March 2011), during which time a further 14 stations were fished in Sandown Bay and outside Portsmouth harbour. Strong NE winds and low catch numbers resulted in the nets being fished closer to Portsmouth harbour towards the end of the survey. These stations produced good numbers of skates. One station was fished in shallow water (7 m) to ascertain the catches of skates in more coastal areas. Soak times ranged from 18.9 – 24.9 hrs.

A total of 123 skates were caught (Table 3.4; Figure 3.6), of which only one (0.8%) was dead. The condition of 86 (69.9%) of the remaining fish were considered to be in good condition (i.e. lively), and 36 (29.3%) recorded as sluggish. This sample of fish included one fish that had been tagged and released on the preceding survey. The remaining fish were all tagged with Petersen discs and released.

Table 3.4: Species composition, sex ratio and length distributions of all batoids caught whilst gillnetting on the FV Angelle Marie (March 2011).

Spp Males Females Sex ratio Species comp Length Length N N F:M (%) range range Raja clavata 83.7 87 60–85 cm 16 55–92 cm 1:5.4 Raja montagui 11.4 7 55–60 cm 7 53–67 cm 1:1 Raja undulata 4.1 5 86–92 cm - - - Raja microocellata 0.8 1 80 cm - - - Total 100%

Frequency 4

0 50 55 60 65 70 75 80 85 90 95 Total length (cm)

R. microocellata R. montagui R. clavata R. undulata

Figure 3.6: Length distribution and numbers of the four batoid species caught whilst gillnetting on the FV Angelle Marie (Mar2011).

In summary, soak times of approximately 24 hrs resulted in low levels of mortality (at least in the short-term), with only 0.8–1.7% of skates considered to be dead (or near dead) when the gillnets were retrieved. When soak time increased to >40 hours, then the proportion of skates considered dead increased to just over 12%. It should be noted that these values do not include any post-capture mortality.

Whereas these studies attempted to mimic fishing operations as realistically as possible, it should be recognised that both crew and scientists handled the fish with care, with skates removed from the nets as soon as possible. Under other conditions, it may be that skates are impacted more by the net hauler, and so fisher behaviour will be an important element of mortality that is harder to quantify.

3.3 Offshore trammel and tangle net studies4

Field studies looking at common skate by-catch in commercial offshore trammel and tangle net fisheries were conducted off Cornwall (ICES Division VIIe – VIIh; Figure 3.7), an area where the D. batis-complex is sufficiently locally and seasonally common that bycatch has become a significant issue for local fishers.

Field studies off Cornwall were undertaken on FV Govenek of Ladram (Figure 3.8) on 1– 5 May and 20–26 August 2011 (period of neap tides). The gear setup used for the field studies consisted of 150 hake nets (120 mm mesh size), 400 trammel nets (250–300 mm inner mesh size) and 50 wreck nets (140 mm mesh size). During normal commercial practise the vessel would typically undertake a mixed target fishery for anglerfish Lophius piscatorius, hake Merluccius merluccius, pollack Pollachius pollachius, cod Gadus morhua and various skate species. Typical commercial trips would last 8–10 days during neap tides. The fishing grounds were broadly within the area 48.5– 51.33º N and 04–10º W.

For the purpose of the field studies, a wide area was fished within these grounds (Figure 3.7), under normal commercial practise with some nets set for shorter soak times to address survivability of common skate by-catch prior to discarding. Soak times ranged from 15–60 hours.

After nets were hauled, all ‘common skate’ were identified to species, measured (total length and disc width), sexed (with maturity recorded for males) and condition scored on a qualitative scale: lively, sluggish/very sluggish (these categories were subsequently combined), dead or scavenged5. Live fish were returned to sea immediately after capture, with >400 lively individuals tagged with roto-tags. Dead specimens were biologically sampled before discarding.

4 This field work was supported by the Defra-funded Fishery Science Partnership project “Spurdog, porbeagle and common skate by-catch and discard reduction” 5 The category ‘scavenged’ was only used in this study, as isopods are an important scavenging group in the Celtic Sea, and can damage fish catches. 58

Figure 3.7: Location of trammel & tangle net studies off Cornwall within ICES areas VIIe – VIIh in May & August 2011.

Figure 3.8: Field studies on FV Govenek of Ladram showing (a) hauling trammel nets aboard, (b-c) Dipturus cf. flossada measured & tagged prior to release, (d) fully scavenged Dipturus batis-complex after 24hr soak time, and (e) tagged Dipturus cf. intermedia prior to release.

A total of 1,242 D. batis-complex were caught (Table 3.5), which were dominated by D. cf. flossada (n = 1234) and with few D. cf. intermedia observed (n = 8). Catches of D. cf. flossada were predominantly comprised of larger (mature) and some sub-adult fish, with smaller size classes not captured in the gears used (Figure 3.9). In the case of D. cf. intermedia (which attains a larger size), the specimens caught were mostly immature. Both species showed an equal sex ratio (Table 3.5).

Of the 1,242 D.batis-complex caught, a total of 1,058 (85.2%) were considered to be in good condition (i.e. lively), with 91 (7.3%) and 93 (7.5%) fish recorded as sluggish and dead, respectively (Table 3.6). Of the lively fish, 420 D. cf. flossada and seven D. cf. intermedia were tagged and released. It was also observed that 51 specimens of D. cf. flossada showed damage by isopods (e.g. Cirolana spp., Eurydice spp.) and other scavengers, which in some cases had scavenged completely through body tissue and internal organs within a 24 h soak time (Fig 3.7(d)).

All soak times resulted in low levels of immediate mortality (i.e. prior to discarding), with 85% of the Dipturus spp. considered lively. Health state was influenced by soak time, with 90% of D. cf. flossada rated as lively for soak times of 15–25 h, and 75% rated as lively for soak times of 58–60 h (Table 3.6). While these studies tried to mimic normal fishing operations, it must be recognised that crew and scientists handled the skates with care, and skates were removed from nets as soon as possible and returned to the sea immediately after data collection. Under normal commercial practices, skates may be impacted more by hauling and handling prior to discarding, and so these estimates should be regarded as upper limits. Furthermore, additional work to better understand longer-term mortality is required.

Table 3.5: Species composition, sex ratio and length distributions of Dipturus batis- complex caught in trammel and tangle nets.

Spp Males Females Sex ratio Species comp N N Length range Length range F:M (%) D. cf. flossada 99.3 608 65–158 626 53–110 1.03:1 D. cf. intermedia 0.7 4 79–230 4 119–128 1:1 Total 100 612 630 1:1.03

Table 3.6: Health state of Dipturus batis-complex following capture in trammel and tangle nets

Lively Sluggish Dead Species Soak time No. % No. % No. % D. cf. flossada 15–25 h 313 90 10 3 23 7 36–48 h 588 85 43 6 59 9 58–60 h 149 75 38 19 11 6 D. cf. intermedia 36–48 h 4 100 58–60 h 4 100 Total 1058 85.2 91 7.3 93 7.5

Figure 3.9: Length distribution of Dipturus cf. flossada (top) and Dipturus cf. intermedia (bottom) caught in trammel and tangle nets during a survey by the FV Govenek of Ladram.

3.4 Longline studies

Further field studies of longline fisheries for skates were conducted off the Channel Islands (ICES Division VIIe), an area where R. undulata and R. brachyura are known to be locally common. Previous studies on longliners operating in the southern North Sea had indicated a high discard survival, but whereas soak times in that fishery were 2–4 hours, the longline fisheries in the Normano-Breton Gulf are often set overnight.

Field studies off the Channel Islands were undertaken on the FV Nicola May (Figure 3.10) from 20–22 July 2010, a period of neap tides. The longline setup used for the three days consisted of five lines, each with approximately 200 hooks, which were usually all connected together, and thus set and hauled as a single line. Each line was 1 nm long, so in total each day approximately 1,000 hooks were set over 5 nm. The hooks used were size 4 Mustad, stainless steel hooks. The bait used throughout the survey was live sandeels.

The five lines were baited and deployed off the south-west tip of Guernsey on the 19th July at around 18:30, in preparation for the survey the following day. The longlines were hauled each morning between 09:30–11:30. Upon hauling, all live rays were tagged with Petersen disc tags and immediately returned to the sea. The lines were then re-deployed in a slightly different location, and left overnight. The five longlines were set in one location for the first two days, whilst four lines were set in one area, and one line set in a separate area on the last day.

Latitude, longitude, date, time and water depth (35–60 m) were recorded for all stations. Soak time ranged from 15–17 hours, which was the normal soak time used in commercial operations in this area. In addition to longlining, a sandeel trawl was deployed on one day, to provide further bait, and two of the three R. brachyura were tagged and released (a smaller specimen of 28 cm total length was considered too small to tag).

A total of 22 skates were caught on longline (Table 3.7). Species, total length, wing width, sex, maturity (males), health state (lively, sluggish or dead), and amount of jaw damage (slight, medium or severe) were recorded for all skates. All individuals were tagged with Petersen discs and released. Specimens of greater-spotted dogfish Scyliorhinus stellaris (n=52) and tope Galeorhinus galeus (n=4) were also tagged and released.

Sixteen (72.7%) of the line-caught skates were rated as ‘lively’ and six (27.3%) were considered to be sluggish. All of the ‘sluggish’ skates were R. brachyura, whilst all R. undulata were lively. All the S. stellaris and G. galeus were lively, and no elasmobranchs were hauled dead.

All specimens of R. undulata (72–97cm) and R. brachyura (69–106 cm) were large fish (Figure 3.11). Of the three male R. undulata, two were mature, with the smallest (72 cm) immature. Eight of the male R. brachyura (91–105 cm) were mature, with three specimens (28–89 cm, including specimens from the sandeel trawl) immature.

Figure 3.10: Field work on (a) the fishing vessel Nicola May showing (b) deployment of longlines, (c) close-up of longline showing sandeel bait, (d) longlines being deployed off the island of Brecqhou (Channel Islands), (e) captured blonde ray Raja brachyura at the surface, and (f) tagging an undulate ray Raja undulata.

Table 3.7: Species composition (batoids only), sex ratio and length range of elasmobranchs (excluding lesser-spotted dogfish) caught whilst longlining on the FV Nicola May.

Spp Males Females Sex ratio Species comp N N Length range Length range F:M (%) Longline Raja undulata 27.3 3 72–97 cm 3 82–95 cm 1:1 Raja brachyura 72.7 9 89–105 cm 7 69–106 cm 1:1.3 Scyliorhinus stellaris - 28 63–118 cm 26 65–109 cm 1:1.08 Galeorhinus galeus - 3 138–150 cm 1 135 cm 1:3 Total 100% Sandeel trawl Raja brachyura 76 2 28–51 cm 1 42 cm 1:2

1 Frequency

0 60 65 70 75 80 85 90 95 100 105 110 Total length (cm)

R. brachyura R. undulata

Figure 3.11: Length distribution and numbers of the skates caught whilst longlining on the FV Nicola May (July 2010).

3.5 Otter trawl Studies

Although discard survival of skates taken in otter trawl fisheries were conducted previously in the southern North Sea (Ellis et al., 2008a) and Bristol Channel (Catchpole et al., 2007), some additional studies were also undertaken off the Channel Islands, as this is an area where Raja undulata is locally abundant.

These studies were undertaken on the FV Nicola May (Figure 3.12) from 17–21 January 2011. The gear used was an otter trawl, as this gear is used for the commercial fishing of skates in this area at this time of year. The trawl had small hopper discs on the ground gear, three fathom chain bridles, and a tickler chain 6’ in front of the fishing line. The trawl had a 9 fathom headline/fishing line, and the cod end used 90 mm mesh.

On the 17th January, given the tidal and wind conditions and recent catches, the Nicola May steamed to fishing grounds to the NE of Sark and fished the first station under typical commercial conditions (4 h tow duration). A second station was then fished on these grounds (3 h tow duration) through dusk and into darkness. The following day a further three stations (one of 3 h and two of 2 h duration) were carried out on fishing grounds between Guernsey and Jersey. On the 19th January, a single tow (4 h duration) was undertaken on the grounds fished the previous day, and then two stations on the fishing grounds between Sark and Alderney were undertaken (each of 2 h duration). The following day three stations (two of 2 h and one of 1 h duration) were sampled on the fishing grounds between Jersey and Guernsey. The last day of the survey undertook a station on a patch of rough ground off the north coast of Guernsey. At this site, starry smooth-hound was the dominant species in the catch (37 of the 40 caught were tagged and released), and although three stingray were also tagged, no skates were captured. Two more stations (1–1.5 h tow duration) were then fished on the grounds between Jersey and Guernsey where two tows were completed.

In total, 14 valid fishing stations were towed over the five day period, with tow durations ranging from one to four hours. Most stations were on a patch of ground between Jersey and Guernsey, with tows also made to the NE of Sark, between Guernsey and Alderney, and north of Guernsey (Figure 3.13). On hauling, the catch was emptied onto the deck, and all live skates that were considered to be large enough (ca. >40cm total length) were tagged with Petersen disc tags and immediately returned to the sea. Total length, wing width, sex, maturity (males), and health state (lively, sluggish or dead) were recorded. Station details included water depth (which ranged from 35–59 m), tow duration (one to four hours), latitude and longitude of shooting and hauling positions. Many tows were undertaken around banks and so tows were not in straight lines. Fish were tagged as soon as practicable and undulate rays were processed before other species. If there were large numbers of fish some were maintained in a deck tank until processing.

Figure 3.12: Field work on the fishing vessel Nicola May, including (a) hauling the otter trawl, (b) ground gear used, with small hopper discs in wings, (c) cod-end being recovered and emptied, (d–e) typical catches of blonde and undulate ray, and (f) tagged common stingray Dasyatis pastinaca.

Figure 3.13: Map of the Channel Islands and stations fished (note the islands of Herm and Sark are not indicated)

A total of 322 skates were caught over the course of the survey (Table 3.8), with blonde ray the most abundant (56.5% by number), closely followed by undulate ray (41.7%). Small-eyed ray were observed in small numbers, but are known to be more abundant on particular grounds nearer to Jersey. A total of 11 common stingrays were also caught.

Although blonde ray was the most common overall, there were subtle differences on the grounds frequented by blonde and undulate ray, and so either species could be more abundant in any one tow (Table 3.9). For example, blonde ray accounted for more than 80% of the skates captured in some tows, whereas undulate ray accounted for more than 90% of the skates caught on other grounds. These differences were thought to relate to relate to sea bed topography and substrate, and further studies on habitat utilisation and preference are required.

Overall 356 fish were tagged with Petersen discs, comprising 168 blonde rays, 127 undulate rays, ten stingrays, six smalleyed ray and 45 starry smooth-hounds Mustelus asterias (Table 3.10).

During the 5–day period, despite towing over the same ground several times, and the large number of tagged skates in the area, only one recapture was made; this was a 57 cm immature male blonde ray caught at the last station. Despite being released in a ‘sluggish’ condition several days earlier, upon recapture and re-release it was recorded as being in a ‘lively’ condition.

The total length ranges caught were 25–103 cm for blonde ray, 35–94 cm for undulate rays, 71–80 cm for the smalleyed ray and 41–67 cm for stingray (Figure 3.14), showing that a broad size spectrum occurs in this region. The absence of

68 smaller fish will likely be due to lower gear efficiency for smaller fish, and that juveniles may occur in shallower, nursery habitats.

The maturity of the males was recorded, based on the state of the claspers. Overall, 89% of blonde ray were immature, with the smallest mature male 79 cm in length, and the largest immature male recorded at 91 cm. The majority (69%) of the male undulate ray sampled were also immature, and the smallest mature male and largest immature male measured 80 cm and 87 cm, respectively.

No skates were dead on capture, although one specimen of blonde ray was badly damaged and recorded as near dead (this specimen was not tagged). Of the 332 rays released, 33% were considered lively and 67% considered sluggish. Overall, for tows of less than 2 h duration, the majority of skates were rated as ‘lively, and for tows 2–4 h duration, the majority were rated as ‘sluggish’. Although anecdotal, it was noted that in the few catches where a lot of kelp was taken, that fish appeared to be in a better condition, possibly because they were protected from abrasion in the codend and/or kept moist whilst on deck.

Table 3.8: Numbers of skate and ray caught (by species), giving species composition of commercial skates (by numbers), sex ratio and length ranges caught whilst otter trawling around the Channel Islands.

Males Females Species Total no. Length Length Sex ratio Species composition N caught N range range F:M (% number) (cm) (cm) Raja brachyura 182 56.5% 93 25–103 88 28–91 1:1.06 Raja undulata 134 41.7% 75 35–94 58 38–94 1:1.29 Raja microocellata 6 1.9% 4 71–78 2 77–80 1:2 Dasyatis pastinaca 11 – 2 42–67 8 41–57 1:0.25 Total 100%

Table 3.9: Species composition (% numbers) of skates in 14 tows conducted around Guernsey

Raja Raja Raja micro- Raja Raja Raja micro- Stn undulata brachyura ocellata Stn undulata brachyura ocellata 1 13.6 81.8 4.5 8 27.8 70.4 1.9 2 12.5 87.5 0.0 9 93.3 0.0 6.7 3 50.0 50.0 0.0 10 90.6 6.3 3.1 4 48.6 51.4 0.0 11 41.2 52.9 5.9 5 22.2 77.8 0.0 12 - - - 6 29.6 66.7 3.7 13 75.0 25.0 0.0 7 20.0 80.0 0.0 14 46.7 53.3 0.0

Table 3.10: Numbers of elasmobranch (n=356) tagged and released

Female Male Species Number Length range (cm) Number Length range (cm) Blonde ray 82 39–91 86 41–103 Undulate ray 57 41–94 70 42–94 Small-eyed ray 2 77–80 4 71–78 Common stingray* 8 41–57 1 67–67 Starry smooth-hound 6 66–80 39 53–95 * one specimen (45 cm total length) was unsexed

9 Blonde ray 8 7 6 5 4

Frequency 3 2 1 0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Total length (cm)

F M U

8 Undulate ray 7 6 5 4

3 Frequency 2 1 0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Total length (cm)

F M

3 Common stingray

Frequency 1

0 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100

Total length (cm)

F M U

Figure 3.14: Length distributions (by sex) for blonde and undulate ray and common stingray

3.6 Beam trawl studies

Field studies of beam trawl fisheries (Figure 3.15) were conducted in south-western waters using vessels from Brixham and Newlyn. Five trips were undertaken on four beam trawlers, under partial-charter, whereby a Cefas observer would have access to those skates that were to be discarded, and with space provided on board for survival tanks.

An initial trip was undertaken on the FV Barentszee (July 2010), which was followed by trips on the FV Cornishman (September 2010), FV Billy Rowney (October/November 2010), FV Barentszee (December 2010) and FV Lady Lou (February 2011). These vessels allowed a range of tow durations to be examined, with the Barentszee and Lady Lou trawling for approximately 1.5–1.75 hrs, and the Billy Rowney and Cornishman towing for longer (ca. 2.5–3 hrs). All vessels fished on the fishing grounds they would normally fish (Figure 3.1), and work was undertaken across various parts of the western English Channel and south-western approaches. Poor weather on one of the trips (Billy Rowney) hampered some of the studies, with sea conditions considered too poor for working with the survival tanks.

When the nets were hauled and emptied, commercial fish were removed (with retained skates measured when time allowed), and those skates that were to be discarded (e.g. fish of unmarketable size and any species listed as ‘prohibited species’) available for scientific study.

Fish were maintained in survival tanks for periods of about 48–72 hours, and were checked each day. The health state was recorded on a qualitative scale (1 = healthy; 2 = sluggish; 3 = very sluggish; 4 = dead), based on the appearance and behaviour of the fish (movements of the fins, spiracles etc.). The survival tanks and protocols used for this study were as described in earlier studies (Revill et al. 2005; Catchpole et al., 2007).

Overall, 101 skates (from a total of six different species) were held in survival tanks (Table 3.11). The main species studies were R. brachyura and L. naevus (n= 26 for each), with smaller samples of R. undulata (n=18), D. batis-complex (n=16), R. montagui (n=13) and R. microocellata (n=1).

The majority of R. undulata survived (77.8%), and survival was relatively high, in the range of 42–50%, for most of the other species (R. brachyura, R. montagui, L. naevus). A smaller proportion of D. batis-complex survived (31.3%), although data for this species were only from one trip which used a tow duration of 3 hrs.

Overall, about 50% of skates survived when tow duration was <2 hrs, and survival was marginally less (48%) for those tows of 2–3 hrs. That approximately 50% of skates survived was also evident across most size categories, although a smaller proportion of small (<40 cm) skates survived in beam trawl catches (ca. 27% compared to 47–60% for other size categories).

Studies on beam trawlers allowed for the release of 228 tagged elasmobranchs (Table 3.12), including R. undulata (n=150) and D. batis-complex (n=32).

Table 3.11: Summary details of survival of skates held in survival tanks following capture by beam trawl

Size Tow Survived Vessel Species range N duration (cm) No. % Barentszee 1.5 h R. undulata 22–69 18 14 77.8 (Trip 1) R. brachyura 20–64 8 2 25.0 R. microocellata 52 1 1 100.0 Barentszee 1.5 h R. brachyura 36–50 8 6 75.0 (Trip 2) R. montagui 33–55 10 4 40.0 Lady Lou 1.75 h R. brachyura 38–53 9 4 44.4 L. naevus 40–52 16 4 25.0 R. microocellata 51 1 - R. montagui 38–45 3 2 66.7 Billy Rowney 2.75 h L. naevus 43–51 6 5 83.3 Cornishman 3 h R. brachyura 48 1 1 100.0 L. naevus 33–67 4 2 50.0 D. batis-complex 22–70 16 5 31.3 Summary data on skate survival (species combined) in relation to tow duration <2 hrs 20–69 74 37 50 >2 hrs 22–70 27 13 48.1 Summary data on skate survival (species combined) in relation to size of the fish 20–39 15 4 26.7 40–44 26 14 53.8 45–49 23 12 52.2 50–54 20 12 60.0 55–70 16 8 47.1

Table 3.12: Summary details of elasmobranchs (n=228) tagged and released during beam trawl studies

otal

Leucoraja naevus Leucoraja brachyura Raja microocellata Raja montagui Raja undulata Raja acanthias Squalus stellaris Scyliorhinus asterias Mustelus T Fishing vessel batis Dipturus Barentzee (Trip 1) 5 1 15 5 4 30 Barentzee (Trip 2) 5 4 135 1 145

Billy Rowney 3 5 3 11

Cornishman 29 3 1 33

Lady Lou 4 4 1 9

Total 32 12 15 1 5 150 3 6 4 228

Figure 3.15: Field work on beam trawlers, including (a) recovery of beam trawl, (b) typical catch on deck, (c) tagged common skate Dipturus cf. flossada, (d) tagged cuckoo ray Leucoraja naevus, (e) survival tanks, and (f) undulate ray Raja undulata in survival tank.

3.7 Tag returns and validation of longer-term survival

Over the course of the study, between March 2010 and September 2011, a total of 1,465 elasmobranchs were tagged and released6, of which 1,117 were species of skate. Chartered fishing vessels were the primary platform for tagging fish, with the majority of fish (ca. 70%) released during these studies. In total, six fishing vessels were chartered for about 45 sea-days. Additional work was undertaken during annual groundfish surveys on board RV Cefas Endeavour.

In total, seven species of skate were tagged, the main species being R. undulata, R. clavata and R. brachyura, with more than 200 of each of these species released. Other species (e.g. R. montagui, L. naevus and D. batis-complex) were tagged and released in lower numbers. Small numbers of two other batoids (Dasyatis pastinaca and Torpedo nobiliana) were caught, and tagged opportunistically.

All releases were catalogued on the Cefas Tagged Fish Database. As of 7 March 2012, a total of 76 individuals (5.2%) had been recaptured, with the recapture rates broadly ranged from 1.4–21.1% (Table 3.13). The most returned species were R. undulata, R. clavata and R. brachyura. Overall return rates for these species ranged from 4.9–9.0%, which confirms that there is a degree of longer-term survival. The longest time at liberty for tagged skates was 650 days. Obviously, the time at liberty is still somewhat restricted, and so subsequent analyses of these data are required to better understand the longer-term survival.

To date, there have been no reported recaptures for those species released in lower numbers (e.g. D. batis-complex and D. pastinaca). Recent fishing regulations have prohibited the capture, retention and landing of R. undulata and D. batis-complex, which has hampered reporting and data collection, as fishermen are not allowed to retain and return whole tagged specimens to land.

During the study five species of dogfish, including Mustelus asterias, Scyliorhinus stellaris, Squalus acanthias, Galeorhinus galeus, were also tagged and released (n = 336) in support of wider elasmobranch studies and other Defra-funded projects. To date, the return rates for dogfish are low, although one was recaptured 333 days after release.

6 not including the skate FSP 74

Table 3.13: Summary of elasmobranchs released and recaptured during the project for commercial fishing vessels and research vessel surveys (Data extracted 7 March 2012)

Number of Fishing Return Vessel Area Dates Species Re- gear Releases (%) captures Angelle Gillnets Isle of 21-25 R. brachyura 2 Marie Wight May R. microocellata 3 2010 R. montagui 11 2 18.2% D. pastinaca 1 R. clavata 68 6 8.8% R. undulata 33 3 9.1% Isle of 24 Feb-1 R. microocellata 2 1 50.0% Wight Mar R. montagui 17 2 11.8% 2011 R. clavata 91 8 8.8% R. undulata 7 Isle of 11-14 R. microocellata 1 Wight Mar R. montagui 14 1 7.1% 2011 R. clavata 101 5 5.0% R. undulata 5 1 20.0% Barentszee Beam SW 12-16 R. brachyura 5 trawl Approaches Jul 2010 R. microocellata 1 R. undulata 15 1 6.7% S. stellaris 5 1 20.0% M. asterias 4 SW 2-6 Dec R. brachyura 5 1 20.0% Approaches 2010 R. montagui 4 R. undulata 135 6 4.4% S. stellaris 1 Billy Beam SW 3-6 Nov D. batis-complex 3 Rowney trawl Approaches 2010 S. acanthias 3 Cornishman Beam SW 25-29 D. batis-complex 24 trawl Approaches Sep L. naevus 1 2010 Lady Lou Beam SW 28 Feb-5 R. brachyura 4 trawl Approaches Mar L. naevus 4 2011 R. montagui 1 Nicola May Longline Channel 20-22 S. stellaris 52 2 3.8% Islands Jul 2010 G. galeus 4 R. brachyura 18 1 5.6% R. undulata 6 Otter Channel 17-21 R. brachyura 168 15 8.9% trawl Islands Jan R. microocellata 6 1 16.7% 2011 D. pastinaca 10 R. undulata 127 7 5.5% M. asterias 45

Table 3.13 (continued): Summary of elasmobranchs released and recaptured during the project for commercial fishing vessels and research vessel surveys (Data extracted 7 March 2012).

Number of Fishing Return Vessel Area Dates Species Re- gear Releases (%) captures CEFAS Beam Western 17-28 R. brachyura 3 1 33.3% Endeavour trawl Channel Mar D. batis-complex 3 2010 L. naevus 1 R. undulata 24 Beam Eastern 20-29 R. brachyura 1 trawl Channel Jul 2010 R. clavata 6 Otter North Sea 17 Aug- D. batis-complex 2 trawl 1 Sep L. naevus 9 2010 S. acanthias 2 Beam Irish Sea 12-29 S. stellaris 15 trawl Sep R. brachyura 6 2 33.3% 2010 L. naevus 5 R. microocellata 4 R. montagui 17 R. clavata 19 Otter Celtic Sea 4 Nov-1 S. stellaris 13 trawl and Irish Dec R. brachyura 8 Sea 2010 T. nobiliana 1 D. batis-complex 6 L. naevus 5 R. microocellata 1 1 100.0% R. montagui 5 R. clavata 8 1 12.5% S. acanthias 71 M. asterias 68 1 1.5% G. galeus 8 Beam Western 7-21 Mar S. stellaris 3 trawl Channel 2011 R. brachyura 3 D. batis-complex 1 L. naevus 11 3 27.3% R. microocellata 1 1 100.0% R. montagui 8 1 12.5% R. undulata 13 M. asterias 22 1 4.5% Otter North Sea 9 Aug-5 G. melastomus 1 trawl Sep D. batis-complex 5 2011 L. naevus 22 R. montagui 38 S. acanthias 15 M. asterias 3 G. galeus 1

3.8 Discard survival: The perception of commercial fishers

Results from the questionnaire (Annex II) indicated that the fishing industry perceived a high discard survival rate for lesser-spotted dogfish from trawls. Longlining was reported to have high discard survival rate for tope and spurdog, the latter of which was perceived to have predominantly lower discard survival rates when caught by trawl and static nets.

Static nets and trawls were predominantly reported as having moderate or low discard survival for skates and rays. Respondents detailed static nets as having a low discard survival rate for sharks, although one respondent reported that smalleyed ray and spotted ray had a high discard survival rate with static nets.

Some respondents provided suggestions for practical ways of increasing the survival chances for discarded elasmobranchs. Four respondents thought there should be a restriction on the tow period (i.e. 3–4 h) for towed gears, and one respondent thought that there should be a shorter soak time for static nets.

4. Current stock status of UK skates: Potential fisheries-induced mortality on skate populations and assessing the risks to stock sustainability of continuing with current fishing practices

Summary

(1) In recent years, ICES has tried to provide advice for an increasing number of nominal skate stocks, although it is acknowledged that the stock units for many species are still unclear.

(2) To date, the perception of the stocks is based largely on the results of scientific trawl surveys, as this provides the best longer-term species-specific information. Improved commercial catch information (including landings and dead discards) is only available for recent years.

(3) The smaller-bodied commercial species, including thornback ray, spotted ray and small-eyed ray, are sampled more effectively in fishery-independent surveys, and have generally shown stable catch rates. Data for those species that occur on offshore grounds (e.g. sandy and shagreen ray) or have more patchy distributions (e.g. undulate and blonde ray) are usually too limited to inform on trends in catch rates.

(4) Potential methods for prioritising stocks of concern are given, and such approaches can help identify those stocks that may be more vulnerable to over- exploitation and/or require more detailed study to better understand current stock status.

(5) Improved species-specific estimates of (i) commercial landings, (ii) discards and (iii) discard survival will allow dead removals to be estimated for the UK (English and Welsh) fleet, although comparable information for other EC fleets is required to estimate the total removals of the various stocks.

4.1 Introduction

Despite the long history of exploitation of skates, the assessments of the relevant species/stocks has only been undertaken in recent years, and ICES only started providing fisheries advice for skates (Raja clavata and Leucoraja naevus) in 2004 (ICES, 2004).

Various methods of evaluating the status of skate stocks have been undertaken by the ICES Working Group on Elasmobranch Fishes (WGEF), and these have been

78 based primarily on survey data, as these were some of the only species-specific data available to the scientific community. Analyses have generally been based on temporal trends in catch rates, with some more detailed studies using Generalised Linear Models (GLM) and spatial analyses using GIS undertaken where possible. Some species-specific information from commercial fisheries has been available for some fleets.

In addition to the limited availability of species-specific data from commercial fisheries, a major problem that has also hampered the quantitative assessment of skates has been the quality of the species-specific data. Such problems are apparent in commercial data and even in some of the scientific trawl survey data. Hence, analyses of survey data need to consider the accuracy of some of these data, and quality assurance and data filtering (especially in terms of international trawl survey data) are required.

Another key issue in evaluating stock status is the unit stock. Although tagging studies have been used to delineate some stocks (e.g. Raja clavata in IVc and VIId are considered to be a single unit; with R. clavata elsewhere in the North Sea (IVa,b) thought to comprise a separate stock), there is a general paucity of information with which to delineate stocks. The reliability of scientific trawl surveys to inform on the status of skates is highly dependent on the grounds fished, the gear used and as to whether the survey grid covers the stock area representatively.

Whereas the stock units for some of the more coastal Raja species can be inferred from our current knowledge of their distribution, including any discontinuities in their occurrence, identification of stock units for those genera occurring offshore (Dipturus spp. and Leucoraja spp.) is more problematic. Although WGEF have attempted to identify biologically-meaningful management units, further studies on the stock identity is required for many species, which may provide more clarity in our perception of stock status.

4.2 Overview of current ICES assessments and advice for skates

In 2005, ICES advised on the demersal elasmobranchs in the North Sea (ICES, 2005), and this advice, based on the catch rates of skates in the North Sea IBTS, suggested that Dipturus batis-complex was depleted, Raja clavata was depleted (though locally abundant in parts), that the status of both Raja montagui and Leucoraja naevus were uncertain, and that catch rates of Amblyraja radiata had increased from the early 1970s to early 1990s. ICES was unable to provide advice for Raja brachyura. Similar advice was given the following year (ICES, 2006).

Further studies by the WGEF in recent years has increased the number of skate stocks for which ICES tries to provide advice for (ICES, 2008a,b, 2010b,c; summarised in Table 4.1), although it should be noted that “In the absence of defined reference points, the status of the stocks of demersal skates and rays … cannot be evaluated. The following (advice) provides a qualitative summary of the general status of the major species based on surveys and landings data” (ICES 2008b).

In recent years, ICES advice for skates has broadly categorised the stocks into the following categories:

(a) Uncertain. Typically because existing surveys do not sample the stock effectively, with catch rates low and/or variable. This category is often used for those species occurring on the outer continental shelf, as there is often a low degree of sampling in these areas, or for those species on the inner continental shelf that have patchy distributions;

(b) Stable or stable/increasing. Typically for those stocks that are sampled in existing surveys and for where information on the catch rates and/or distribution indicates that there is no decline over the course of the time series;

(c) Depleted. For those species where there has known to have been a longer- term decline in the geographical distribution.

Table 4.1: Perception of stock status of skates (Rajidae) occurring around the British Isles according to recent ICES Advice (Adapted from ICES 2008a,b; ICES 2010b,c)

Scientific State of stock Area name 2008 2010 Amblyraja IVa,b, IIa Stable Stable radiata Dipturus batis- IVa (likely complex merging with VIa Depleted Depleted & IIa) Depleted. The stock likely extends into VI Depleted IIa and IVa Depleted. Near extirpated from the Irish VII Depleted Sea (VIIa) D. VI – Uncertain nidarosiensis D. oxyrinchus VI–VII – Uncertain Leucoraja VI Uncertain Uncertain circularis VIIb,c,h–k Stable/increasing Uncertain, stable/increasing in VIIj L. fullonica Uncertain. There is a poor signal from VI – surveys for this species Uncertain. There is a poor signal from VIIbc,g–k Uncertain surveys for this species L. naevus IVa,b (may Stable Stable extend into VI) Uncertain. The stock area is not known, and may merge with sub-areas IV and VI Stable/increasing VII. Survey catches in VIa are increasing Uncertain. The stock area is not known, and may merge with sub-areas VI and VII Uncertain VIII. French LPUE in the Celtic Sea has declined. Survey catches appear stable

Table 4.1 (continued): Perception of stock status of skates (Rajidae) occurring around the British Isles according to recent ICES Advice (Adapted from ICES 2008a,b; ICES 2010a,b) State of stock Scientific name Area 2008 2010 Raja brachyura IVc, VIId (patchy Uncertain Uncertain occurrence) Uncertain. No trends are apparent VIa Uncertain from surveys Uncertain. No trends are apparent VIIa Uncertain from surveys VIIe – Uncertain Uncertain. No trends are apparent VIIf Uncertain from surveys R. clavata IVc, VIId Stable/increasing Stable/increasing IVa,b Uncertain Uncertain VIa Stable/increasing Stable/increasing VIIa,f,g Stable/increasing Stable/increasing VIIe – Uncertain R. microocellata VIIf Stable/increasing Stable/increasing R. montagui IVb,c Stable/increasing Stable/increasing VIa Stable/increasing Stable/increasing VIIa,f,g Stable/increasing Stable/increasing VIIe – Uncertain R. undulata VIId, merges Uncertain, reasons Uncertain. Locally common in with VIIe for concern discrete areas Uncertain (but with Uncertain. Locally common in VIIj (Tralee Bay) cause for concern) discrete areas Rostroraja alba VII Severely depleted –

4.3 Prioritising species and stocks of concern

The prioritisation of skate species/stocks of management interest and concern may be informed by various criteria, including:  maximum total length (given that larger skates are often considered to be more susceptible to over-fishing),  commercial importance (by weight and/or value),  conservation listing (e.g. IUCN),  the perception of the stock, as advised on by ICES, and  whether or not ICES has been able to formulate advice.

Such criteria can be used to rank species of conservation or commercial importance, but other approaches can be used to integrate such information and prioritise species of potential interest and concern, as discussed below.

4.3.1 Ranking management importance of skate species

Information on the recent commercial importance (by weight and value), conservation importance, total length and whether or not they are assessed by ICES was compiled for all skates thought to occur around the British Isles, including the deep-water species that may occur to the west of the area (Table 4.2).

In order to prioritize species of particular interest, these values were ranked on a scale of 1–5, as shown in Table 4.3. The sum of the rankings was used to give an indicative list of those skate species for which there should be consideration of further studies to better understand their current status.

Using this approach ranked the skates in the following order of concern (incorporating both commercial and conservation importance): Dipturus batis- complex, Rostroraja alba, Raja brachyura, R. undulata, Leucoraja circularis, D. oxyrinchus, D. nidarosiensis, R. clavata, L. fullonica and R. microocellata.

Table 4.2: Taxonomic ordering of skates listing the information used to rank the species of concern according to maximum length, IUCN listing, commercial landings and ICES’ perception of the main stocks. Sources: [1] Stehman & Burkel (1984), [2] Froese & Pauly (2011), [3], Ellis et al. (2005b), [4] Ryland & Ajayi (1984), [5] Ellis et al. (2012a), [6] Gibson et al. (2008). IUCN listings are data deficient (DD), least concern (LC), near threatened (NT), vulnerable (VU), endangered (EN) and critically endangered (CR).

UK Value of UK IUCN landings landings ICES advice Maximum Scientific name Listing (t) in 2008 (£’000) in or Length [6] (exc. 2008) (exc. assessment Scotland) Scotland)

Amblyraja hyperborea 85 cm [1] LC - - No advice A. jenseni 85 cm [2] LC - - No advice A. radiata 60 cm [1] LC 1.1 1.3 Stable Bathyraja pallida 160 cm [1] LC - - No advice B. richardsoni 175 cm [1] LC - - No advice B. spinicauda 170 cm [1] LC - - No advice Dipturus batis- 250 cm [1] CR 24.1 30.5 Depleted complex D. linteus 110 cm [1] LC - - No advice D. nidarosiensis 200 cm [1] NT 43.1 68.4 Uncertain D. oxyrinchus 150 cm [1] NT 20.7 31.9 Uncertain Leucoraja circularis 120 cm [1] VU 13.6 17.8 Uncertain L. fullonica 100 cm [1] NT 12.5 13.7 Uncertain L. naevus 70 cm [1] LC 218.4 264.4 Uncertain/stable Malacoraja kreffti 70 cm [1] LC - - No advice M. spinacidermis 70 cm [1] LC - - No advice Neoraja caerula 30 cm [1] DD - - No advice Raja brachyura 120 cm [1] NT 155.8 187.3 Uncertain R. clavata 112 cm [3] NT 441.7 524.9 Stable R. microocellata 90 cm [4] NT 88.3 84.6 Stable R. montagui 80 cm [1] LC 21.6 28.7 Stable R. undulata 120 cm [5] EN 2.4 1.1 Uncertain Rajella bathyphila 90 cm [1] LC - - No advice R. bigelowi 50 cm [1] LC - - No advice R. fyllae 55 cm [1] LC - - No advice R. kukujevi Unknown DD - - No advice Rostroraja alba 200 cm [1] CR 1.0 3.4 Depleted

Table 4.3: Scoring system for ranking UK skates according to four criteria (total length, IUCN listing, quantities of reported landings and ICES assessment). All criteria were given equal waiting in this example.

Score Total length IUCN Listing Landings ICES assessment 1 <60 cm LC 0 Stable 2 60-79 cm NT <10 t 3 80-99 cm DD / VU 10-50 t Uncertain or No advice 4 100-149 cm EN 50-100 t 5 >150 cm CR >100 t Depleted

4.3.2 Ecological Risk Assessments

The UN Code of Conduct for Responsible Fisheries (FAO, 1995; Webster & Collins, 2005) states that the “best scientific evidence available” should be used to evaluate the state of any fisheries to support decisions, yet for many elasmobranch species, stock size, catch levels, mortality rates and thus stock status are unknown. To try to address this, various risk-based approaches have been considered for data-poor, multi-species scenarios.

These include Productivity Susceptibility Analyses (PSAs), which are often carried out as part of larger ecosystem assessments (Ecological Risk Assessments, ERAs).

Such approaches attempt to evaluate the vulnerability of a species or stock to overfishing based on its biological sensitivity or productivity, and its susceptibility to capture in the main fisheries operating over its range. Such approaches were explored under other Defra-funded projects7, and are being applied to elasmobranchs within UK waters. Such PSAs are being tested to evaluate the suitability of such methods to identify and prioritise those species for which improved assessments and/or precautionary management may be required. The final report for Defra project MF1205 provides more details on these methods and approaches.

An example plot of the overall rankings according to the biological productivity and fisheries susceptibility of demersal elasmobranchs (including ten skate and six batoid species) in the Celtic Sea is shown in Figure 4.1.

7 See “Development of tools for estimation of stock status under uncertainty - MF1205” and “Definelt – Developing fisheries management indicators and targets - MF1206” on http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=ProjectList&Completed=0&AUID=1667 84

Figure 4.1: Example PSA for demersal elasmobranchs that may be taken in gillnet, otter trawl, pelagic longline and pelagic trawl fisheries in the Celtic Sea, with uncertainties indicated by dashed lines. Species include ten skates (Dipturus batis– complex (SKT), Raja brachyura (BLR), R. clavata (THR), R. microocellata (PTR), R. montagui (SDR), R. undulata (UNR), Leucoraja circularis (SAR), L. fullonica (SHR), L. naevus (CUR), and Rostroraja alba (WSK)), five other batoids (Dasyatis pastinaca (SGR), Myliobatis aquila (EGR), Pteroplatytrygon violacea (pelagic stingray), Torpedo nobiliana (ECR) and T. marmorata (MER)), and the angel shark Squatina squatina (ALS). Numbers indicate the vulnerability rank in that particular fishery. It should be noted that teleosts are not shown in this plot, but were included in rankings.

4.4 Survey trends for skates in UK waters

Currently, the evaluations of skate stocks conducted by WGEF that support ICES advice are based on analyses of survey trends. Several current scientific trawl surveys are internationally-coordinated, including various beam trawl surveys (coordinated by WGBEAM) and surveys with Grande Ouverture Verticale (GOV) otter trawl (coordinated by IBTSWG). For example, UK beam trawl surveys sample several skate stocks in the eastern English Channel and southern North Sea, western English Channel and in the Bristol Channel and Irish Sea.

It is important to note that there are no long-term or broad scale surveys specifically to sample skate stocks, and so the gears and survey grids of existing surveys may not be ideal for sampling skates. For example, beam trawl surveys are thought to sample juvenile skates effectively, although larger individuals/species will not be sampled effectively, whereas the GOV trawl used in IBTS will not fish the smallest size categories effectively. In terms of survey grids, the UK beam trawl surveys have a greater proportion of stations in inshore waters (as the surveys were originally

85 designed to sample juvenile plaice and sole), and so catch rates of inshore skates (e.g. R. clavata and R. microocellata) are generally higher than for the offshore species. Furthermore, some skates have patchy distributions, which may be related to more specific habitat requirements, and so the catch rates of species such as R. brachyura and R. undulata may be low and variable.

Examples of the temporal trends in catch rates and the frequency of occurrence for the main skate species taken in UK beam trawl surveys are shown in Figures 4.2– 4.4. These surveys include the July survey of the eastern English Channel and southern North Sea (see Parker-Humphreys, 2005), Irish Sea and Bristol Channel (see Parker-Humphreys, 2004a,b) and the survey conducted in the Great West Bay (western English Channel) by the commercial fishing vessel Carhelmar.

The occurrence of R. brachyura were low in most of the beam trawl surveys, with this species usually occurring in <10% of hauls for the surveys in the English Channel and Irish Sea. They were more frequently observed in the Bristol Channel. Although average catch rates were low, there were no obvious signs of declining catches over the time periods considered (but see below for potential confusion with R. montagui).

Raja clavata was usually the most frequently observed skate species in beam trawl surveys of the eastern English Channel, Bristol Channel and Irish Sea. Trends in the mean catch per unit effort (CPUE) have either increased slightly over time, or been relatively stable, in all these surveys series, with no signs of decreasing catches.

Catch rates of R. montagui have been broadly stable or increasing in the Bristol Channel and Irish Sea. In contrast, survey catches in both the eastern and western English Channel were generally higher in the first half of the survey series than in the latter half. The causes of this apparent decline are unclear, but may be related to (a) improved separation of R. montagui from R. brachyura, (b) increased competition from other larger skates (e.g. R. brachyura and R. clavata), (c) subtle shifts in habitat use (given that R. montagui tends to occur on the deeper grounds of these survey grids).

Leucoraja naevus, which generally occurs on offshore grounds, was only taken in reasonable numbers in the Irish Sea beam trawl survey. Although catch rates were higher at the start of the time series, catches have been relatively stable in the last decade or so. Further studies to better understand the wider status of this species on offshore fishing grounds are required.

Raja microocellata is locally abundant in the Bristol Channel, and catch rates in this area were stable. Although it is taken in smaller numbers in the English Channel, catch rates in surveys were generally low and variable. R. undulata is locally abundant in parts of the English Channel, although catch rates in the both the eastern Channel and Carhelmar surveys were low. This species was not observed in the eastern Channel beam trawl survey in 2006–2007, although it has since re- appeared in the survey. Although only taken in low numbers in the Carhelmar survey, this species also ‘disappeared’ from 2005–2009. Given the patchy distribution of this species in the English Channel, dedicated surveys may be required to better inform on its current status, as it can be locally abundant on certain inshore grounds (see Section 3).

3.0 35 3.0 20 (a) R. brachyura (VIIf) (b) R. brachyura (VIIa) 30 2.5 2.5 16 25 2.0 2.0 12 20 1.5 1.5

15 8 % occurrence% 1.0 occurrence% 1.0

10 Mean numberMean per hour Mean numberMean per hour 4 0.5 0.5 5

0.0 0 0.0 0

1995 1998 1999 2002 2005 2008 2011 1993 1994 1996 1997 2000 2001 2003 2004 2006 2007 2009 2010

1995 1998 2001 2002 2005 2008 2011 1993 1994 1996 1997 1999 2000 2003 2004 2006 2007 2009 2010

5.0 60 10.0 60 (c) R. montagui (VIIf) (d) R. montagui (VIIa)

4.0 8.0 45 45

3.0 6.0

30 30 % occurrence%

2.0 4.0

% occurrence% Mean numberMean per hour

15 numberMean per hour 15 1.0 2.0

0.0 0 0.0 0

1995 1998 2001 2002 2005 2008 2011 1993 1994 1996 1997 1999 2000 2003 2004 2006 2007 2009 2010 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

10.0 75 10.0 75 (e) R. clavata (VIIf) (f) R. clavata (VIIa)

8.0 60 8.0 60

6.0 45 6.0 45 % occurrence%

4.0 30 4.0 30

Mean numberMean per hour % occurrence%

2.0 15 numberMean per hour 2.0 15

0.0 0 0.0 0

1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

6.0 75 4.0 35 (g) R. microocellata (VIIf) (h) L. naevus (VIIa) 5.0 30 60 3.0 25 4.0 45 20 3.0 2.0 15

30 % occurrence% 2.0 occurrence%

10 Mean numberMean per hour Mean numberMean per hour 1.0 15 1.0 5

0.0 0 0.0 0

1995 1998 2001 2002 2005 2008 2011 1995 1998 1999 2002 2005 2008 2011 1994 1996 1997 1999 2000 2003 2004 2006 2007 2009 2010 1993 1994 1996 1997 2000 2001 2003 2004 2006 2007 2009 2010 1993

Figure 4.2: Trends in the mean relative abundance (ind.h–1) and frequency of occurrence of four skate species in the Bristol Channel (VIIf, left hand panel) and four skate species in the Irish Sea (VIIa, right hand panel). Data from the UK beam trawl survey (based on 97 stations (33 in VIIf, and 64 in VIIa) fished at least 16 times during the 19 year time series).

12 70 (a) R. clavata 60 9 50

40 6

30 % occurrence% 20

Mean numberMean per hour 3 10

0 0

1993 1996 1999 2000 2003 2006 2009 2010 1994 1995 1997 1998 2001 2002 2004 2005 2007 2008 2011

0.3 10 0.15 5 (b) R. brachyura (c) R. microocellata

8 0.12 4

0.2 6 0.09 3

4 0.06 2 % occurrence%

0.1 occurrence% Mean numberMean per hour 2 numberMean per hour 0.03 1

0 0 0 0

1993 1996 1999 2002 2004 2007 2010 1994 1995 1997 1998 2000 2001 2003 2005 2006 2008 2009 2011

1995 1997 2000 2003 2006 2008 2009 2011 1993 1994 1996 1998 1999 2001 2002 2004 2005 2007 2010

0.8 30 0.3 15 (d) R. montagui (e) R. undulata 25 12 0.6 20 0.2 9 0.4 15

6 % occurrence%

10 occurrence% 0.1 Mean numberMean per hour

Mean numberMean per hour 0.2 3 5

0 0 0 0

1995 1997 2000 2003 2006 2008 2011 1993 1994 1996 1998 1999 2001 2002 2004 2005 2007 2009 2010

1995 1998 2000 2003 2006 2009 2011 1994 1996 1997 1999 2001 2002 2004 2005 2007 2008 2010 1993

Figure 4.3: Trends in the mean relative abundance (ind.h–1) and frequency of occurrence of five skate species in the eastern English Channel and southern North Sea (VIId and IVc). Data from the UK beam trawl survey (based on 77 stations fished at least 16 times during the 19 year time series).

0.20 15% 2.0 40% (a) R. brachyura (b) R. clavata

0.15 1.5 30% 10%

0.10 1.0 20%

% occurence% % occurence% 5%

0.05 0.5 10%

Mean number per 30 minute towminute 30 per numberMean Mean number per 30 minute towminute 30 per numberMean

0.00 0% 0.0 0%

1991 1995 2005 2009 1989 1993 1997 1999 2001 2003 2007

1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2009

0.15 10% 1.0 50% (c) R. microocellata (d) R. montagui

0.12 8% 0.8 40%

0.09 6% 0.6 30%

0.06 4% 0.4 20%

% occurence% % occurence%

0.03 2% 0.2 10%

Mean number per 30 minute towminute 30 per numberMean Mean number per 30 minutetow per 30 numberMean

0.00 0% 0.0 0%

1995 1997 2009 1989 1991 1993 1999 2001 2003 2005 2007

1991 1995 2005 2009 1989 1993 1997 1999 2001 2003 2007

0.15 10% (e) R. undulata

0.12 8%

0.09 6%

0.06 4% % occurence%

0.03 2% Mean number per 30 minute towminute 30 per numberMean

0.00 0%

1991 1993 1995 1997 1999 2001 2003 2005 2007 2009 1989 Figure 4.4: Trends in the mean relative abundance (numbers per 30 minute tow, grey columns) and frequency of occurrence (solid line) for five skate species caught in the Great West Bay (western English Channel) during the Carhelmar survey (1989–2010). See Burt et al. (2013) for further information.

4.5 Stock status: The perception of commercial fishers

Fishers were asked their perceptions on the current status of elasmobranch stocks. Cuckoo ray, spotted ray, thornback ray and blonde ray stocks were generally deemed by commercial fishers to be stable, although smaller numbers of respondents perceived these stocks to be either increasing or decreasing (Table 4.4). Thornback ray was the species for which the greatest proportion of respondents felt the stock was increasing, although there was also a relatively high proportion of respondents who felt their stock was decreasing. There was more uncertainty over the state of cuckoo ray, with 26% of respondents unsure about their current status.

Small-eyed ray stocks were perceived to be stable or increasing by all respondents (n = 6). Only one respondent (VIId) reported on undulate ray stocks and perceived they were stable or increasing.

The majority of respondents thought that stocks of two other demersal elasmobranchs (lesser-spotted dogfish and smooth-hounds) were increasing or stable. Two respondents commented that these species may be more prolific due to an increased food supply in the area. Although nearly half the respondents considered the tope stock to be stable, there was a mixed perception. Spurdog stocks also had a mixed perception, and although 42% of respondents perceived this stock to be increasing, other respondents thought they were stable (29% of respondents), decreasing (21%) or were unsure (8%). Most respondents were unsure on the status of blue shark stocks (65%), and 55% were unsure of the status of porbeagle stocks.

Reasons for increasing stocks reported by some of the respondents included reduced fleet size, landing restrictions, increasing water temperatures and increased food availability. Factors reported for decreasing stock levels included dredging, wind farm construction and effort outside the 6 mile limit by French, Dutch and Belgian trawlers.

Table 4.4: Perception of the current status of five skate species and four species of dogfish by commercial fishers.

Total number No. (and %) of respondents who felt their stock was: Species of Increasing Stable Decreasing Unsure respondents L. naevus 19 1 5.3% 11 57.9% 2 10.5% 5 26.3% R. brachyura 24 3 12.5% 15 62.5% 3 12.5% 3 12.5% R. clavata 26 5 19.2% 15 57.7% 4 15.4% 2 7.7% R. microocellata 6 1 16.7% 5 83.3% 0 0.0% 0 0.0% R. montagui 21 1 4.8% 14 66.7% 3 14.3% 3 14.3% S. canicula 26 15 57.7% 11 42.3% 0 0.0% 0 0.0% Mustelus spp. 24 12 50.0% 10 41.7% 1 4.2% 1 4.2% Squalus acanthias 24 10 41.7% 7 29.2% 5 20.8% 2 8.3% Galeorhinus galeus 25 5 20.0% 12 48.0% 7 28.0% 1 4.0%

4.6 Potential fisheries induced mortality

Currently, ICES advises that several skate stocks appear stable (see Table 4.1), on the basis of fishery-independent trawl surveys. Other stocks are thought to show signs of concern, with ICES advising either a reduction in catch (e.g. for L. naevus), no target fisheries (e.g. R. undulata) or for listing the species as ‘prohibited’ (e.g. R. alba). There are also several stocks for which ICES has not been able to advise, and some of these are important commercial species (e.g. R. brachyura).

Species-specific landings data are now becoming available and, as most nations have discard sampling programmes, improved estimates of catch will soon be able to be made for recent years. Although the quantities of skate discards can now be estimated for many UK fleets (see Section 2), and there are improved estimates of discard survival for several metiers (see Section 3), further collaborative studies at an international level are required to estimate the total removals of the various stocks. Hence, comparable studies to the current project are required for other European fleets exploiting these stocks, so that more accurate estimates of total dead removals from the stock can be made.

Furthermore, it should be reiterated that better definitions of stock units are required for some species, and that both national and international data will need to be corrected, due to species misidentifications. It should also be noted that the discarding rates (and discard survival rates) of skates may be very different between small, inshore vessels and larger, offshore vessels; and so landings and discard data may need to be disaggregated by vessel size. This process is illustrated in Figure 4.5.

Figure 4.5: Flow diagram for estimating total (dead) catch of skates 91

5. Options for improved fisheries management of skates

Summary

(1) There are several potential management options for skates, including input (effort) and output (catch) controls and technical measures.

(2) The main measures currently used include a Total Allowable Catch (TAC) and ‘Prohibited species list’ (EC measures), and a Minimum Landing Size (local bylaws in some areas of England and Wales).

(3) TACs are the main measure currently used in EC waters, but the TAC is currently applied to combined skates (Rajidae) and often over broad areas. The potential merits of allocating TACs to more defined grouping (e.g. by genera and/or over more biologically meaningful spatial areas) could usefully be evaluated, as could more regionally-focused management plans.

(4) If spatial management is to be considered for skates, then further studies to better delineate what may be defined as ‘essential fish habitat’ or ‘ecologically-important habitat’ for some skate stocks occurring in UK waters are required.

(5) The improved management of skates will benefit from various studies (including aspects of their life-history, commercial catch information, fishery-independent survey data, ecology and behaviour, and stock definition) that can provide evidence of current stock status and to inform on the most effective and pragmatic management measures.

5.1 Introduction

There have been longer-term changes in the species composition of the skate fauna in several regions around the UK, as exemplified by the disappearances of Rostroraja alba and Dipturus batis-complex from areas of former range (see Section 1). There has also been concern over declines in the abundance of other skate stocks, for example R. clavata in the central and northern North Sea, and uncertainty in the current status of many of the lesser-known species (including those occurring along the edge of the continental shelf, such as L. circularis and L. fullonica).

Management actions for skates have only been introduced in recent years, and many of the initial management actions (e.g. the total allowable catches established, local bylaws establishing a minimum landing size) were implemented for skates at the Family level. The introduction of species-specific recording of landings and some species-specific management measures have only existed for recent years. Elsewhere in the world, the management of skate stocks have often been managed as the multi species-complex as a whole (e.g. Hogan & Cadrin, 2010; Keiley et al.,

2010), despite that there may be very different life-histories, geographical and bathymetric distributions, commercial importance and susceptibilities to over- exploitation. This is not a situation unique to skates, as such issues can occur within other groups where species identification is problematic, such as in the case of rockfish (Sebastidae) (Parker et al., 2000; Heifetz et al., 2007).

Management options for skates, as with all fisheries, may be broadly categorised into input (effort) and output (catch) controls and technical measures (FAO, 2003). Input controls can include effort control, license schemes and restrictions on effective effort for particular gears type (e.g. restrictions on number of hooks, soak times, length of gillnets). Output controls refer to total allowable catches and quotas. Technical measures can include mesh size regulations, minimum and maximum landing sizes, closed areas, gear restrictions and gear modifications (e.g. to avoid unwanted bycatch).

5.2 Total allowable catch and quotas

This is currently the main method for regulating fishing opportunities for skates within the ICES area, although depending on the level at which the TAC is set and the allocation of quotas to Member States and to individual vessels / producer organisations, it can result in discarding, a proportion of which will be dead.

A TAC for skates was only established in 1999 (for EC waters in the North Sea) and 2009 (other EC waters in the ICES area), and these TACs are implemented at a Family level and over broad regions which may potentially cover multiple stocks for some species. Hence, TACs may not necessarily benefit those species/stocks that are depleted and in need of management.

The more recent collection of species-specific landings data, and recent increased number of stocks for which ICES tries to provide advice for, may allow for a more refined approach to quota management (e.g. by genus and at a finer spatial scale) in the future, and such an approach has been suggested by the North West Waters Regional Advisory Council (NWWRAC, see below).

5.3 Size restrictions

Potential size restrictions for elasmobranchs may include a minimum landing size (MLS) and/or a maximum landing length (MLL). Traditionally, fisheries management has emphasized the need to protect juveniles and to allow them to reach maturity. Hence, for there are minimum landing sizes for many commercial teleost stocks in UK waters and, in some instances, local bylaws to afford some degree of protection to nursery grounds.

However, elasmobranchs theoretically have a closer relationship between the spawning stock biomass and recruitment, and larger females typically produce more offspring that may be of better quality (e.g. of larger size). Hence, there has been much discussion on the merits of minimizing fishing mortality on the mature female component of elasmobranch stocks (see Cortés, 1999; Simpfendorfer, 1999; Prince, 2005), especially if the female component of the stock can be targeted.

An important issue for the effectiveness of a MLS is if it is introduced at a species- specific or family level. Whereas many SFCs (now IFCAs) introduced a MLS for ‘skates and rays’ in inshore waters, extending such measures into waters further offshore could restrict the landing of some of the smaller-bodied species that are most abundant on such grounds, such as L. naevus and R. montagui.

5.4 Prohibited species lists

Worldwide, several nations have gradually introduced ‘Prohibited species lists’ into regional fishery management plans. For example, the USA, in implementing a shark management plan for their Atlantic coast included 19 shark species as ‘prohibited’ (Cortes & Neer, 2009), and sawfish and several shark species are protected in either state or commonwealth waters of Australia (Rose, 2001; Bensley et al., 2009).

The European TAC and quota regulations introduced a list of ‘prohibited species’ in 2007, whereby it was “prohibited for Community vessels to fish for, to retain on board, to tranship and to land” basking shark Cetorhinus maximus and white shark Carcharodon carcharias in all Community and non-Community waters. Since 2010, this list has been extended to include angel shark Squatina squatina in all EU waters; porbeagle Lamna nasus in some waters; Dipturus batis in EU waters of ICES division IIa and ICES sub-areas III–IV, VI–X; Raja undulata and Rostroraja alba in EU waters of ICES sub-areas VI–X; and guitarfishes (Rhinobatidae) in EU waters of ICES sub- areas I–XII (CEC, 2012a).

The utility of prohibited species lists was also extended to fisheries in the ICCAT convention area, and it is currently prohibited to retain on board, tranship or land any part or whole carcass of bigeye thresher shark Alopias superciliosus, hammerhead sharks (Family Sphyrnidae, except for Sphyrna tiburo), oceanic whitetip Carcharhinus longimanus and silky shark Carcharhinus falciformis (CEC, 2012b).

The inclusion of some species that may be locally abundant on prohibited species lists has been a contentious issue with the fishing industry, including UK vessels, with D. batis and R. undulata the two species questioned. In terms of these two species, ICES (2010d,e) advised that there was “no basis in the current or previous ICES advice for the listing of (D. batis / R. undulata) as a prohibited species”.

ICES WGEF considered the utility of lists of prohibited species, and highlighted that such lists were an “appropriate measure for trying to protect the marine fishes of highest conservation importance, particularly those species that are also listed on CITES and various other conservation conventions. Additionally, there should be sufficient concern over the population status and/or impacts of exploitation that warrants such a long-term conservation strategy over the whole management area” (ICES, 2010a).

However, ICES WGEF also considered that there some species that were depleted in parts of their range “may remain locally abundant in some areas, and such species might be able to support low levels of exploitation. From a fisheries management viewpoint, advice for a zero or near zero TAC, or for no target fisheries, is very different to a requirement for ‘prohibited species’ status, especially as a period of

94 conservative management may benefit the species and facilitate a return to commercial exploitation in the short term” (ICES, 2010a).

Obviously, there should be a clear rationale and long-term conservation need to include species within a ‘prohibited species list’, as regular changes to such a list could lead to confusion for both the fishing industry and enforcement officers.

5.5 Spatial management

There has been much discussion in relation to marine protected areas (MPAs) for elasmobranchs in recent years (e.g. Bonfil, 1999; Wiegand et al., 2011). For those elasmobranch species that aggregate in certain sites (and which may be seasonal), and may be for mating, pupping, egg-laying or feeding, there could be due consideration of spatial management. This could include seasonal closures or effort/gear restrictions; because this could minimize directed fisheries from over- fishing important life-history stages (Ellis et al., 2008c).

Spatial management has been included within management plans for elasmobranchs elsewhere in the world, for example seasonal gear restrictions and fishing area closures for certain commercial shark species, and sanctuaries to help protect sand tigers have been established in Australian waters (Stevens, 2002; Walker, 2004), and ecologically-important sites for nurse sharks have been protected in US waters (Carrier & Pratt, 1998).

The utility of closed areas for species protection would be highly dependent on their home range. Hence, studies to examine the movements, home range and threats within this area need to be fully evaluated (e.g. Hunter et al., 2005a, 2006). Although some elasmobranchs may have relatively small home ranges (Ellis et al., 2011), many elasmobranchs, including many skates, have broad habitats. Several studies have reported either distributional data (e.g. Ellis et al., 2005a) or modelled habitats (e.g. Martin et al., 2010) at the species level. However, further studies are required to better delineate what may be defined as ‘essential fish habitat’ or ‘ecologically- important habitat’ for the main skate stocks occurring in UK waters.

Recent studies to better define spawning and nursery grounds of selected fish species in UK waters were undertaken recently (Ellis et al., 2012b), and this study included several elasmobranchs, including R. clavata, R. montagui, R. undulata and Dipturus batis-complex. Of these, only R. undulata was subsequently considered for inclusion as a ‘feature of conservation importance’ (FOCI) within the national programme to identify potential Marine Conservation Zones8.

Although existing fishery-independent data can be used for the preliminary identification of some nursery areas, further studies to better define areas of importance to spawning are required. Although there is some evidence from elsewhere in the world to suggest that some oviparous elasmobranchs have defined spawning grounds (e.g. Hoff, 2008, 2010; Love et al., 2008), there is little reliable

8 See: Natural England/Joint Nature Conservation Committee (2010). Marine Conservation Zone Project – Ecological Network Guidance, 142 pp (http://jncc.defra.gov.uk/pdf/100608_ENG_v10.pdf). 95 field evidence in European seas (see Ellis et al., 2005a and references cited therein; Hunter et al., 2005b) to delineate such ‘essential fish habitat’.

5.6 Gear modifications

Fishing gear technology offers potential mechanisms to alter catch compositions in fisheries that catch elasmobranchs. To date, there are no fishing gear specifications legislated for in EU fisheries that are designed specifically to alter the catch patterns of elasmobranchs. Moreover, there have been limited gear technology studies focusing on reducing elasmobranch catches in EU fisheries. There are, however, studies focusing on reducing elasmobranch catches that have been conducted in other parts of the world.

For example, an excluder grid has been developed in the US hake fishery to reduce bycatch of spurdog Squalus acanthias. The numbers of this species caught were reduced, while target species were caught in commercial quantities. The reduced catch of S. acanthias also resulted in an increased quality of marketable catches, likely reductions in the mortality of non-target species, and decreases in the codend catch handling times (Chosid et al., 2012).

Also, in the pelagic and bottom longline fisheries off Northeast Brazil, changing the type of hook and the relative hook position within the water column reduced elasmobranch bycatch, and decreased their fishing mortality. Comparisons between circle and J-style hooks demonstrated that the circle hooks had a greater efficiency in reducing the mortality of elasmobranch species (Afonso et al., 2011).

Other gear technology developments, although not developed to improve selectivity towards elasmobranchs specifically, have reduced the capture of elasmobranchs alongside other species. In the US hake trawl fishery, large escape panels in the belly of the net have been shown to significantly reduce the catch of skate and other species while not reducing the catch commercial species (Milliken & DeAlteris, 2004). Similarly, large mesh belly panels developed for the North Sea roundfish otter trawl fishery also led to reduced catches of skates (e.g. Revill & Doran, 2008). The installation of benthic release square mesh panels also reduced the capture of thornback ray in the Thames otter trawl fishery (Catchpole et al., 2010). This type of trawl modification makes use of the behaviour of skates and rays, which often remain on the bottom of the trawl during the catching process.

Species selective grids developed for use in the EC Nephrops and anglerfish fisheries have also shown to reduce the capture of skates and rays (e.g. Meillat & Dupouy, 1994). This type of gear modifications is less dependent on the behavioural reactions of fish inside the trawl and acts more as a physical barrier. The large size attained by elasmobranchs at an early age, lends itself to the physical filtering of the catch within the trawl. There is potential to reduce the capture or further improve size selection of elasmobranchs by utilising the disparity between their large size and the smaller target species.

Further to the improvement of selectivity towards elasmobranchs is the advantage of improving selectivity towards the whole catch, in order to improve the survival of those elasmobranchs which are retained by the trawl and discarded. Enever et al.

(2010) demonstrated that the survival of skates discarded after being caught can be improved by simple gear-based technical measures aimed at reducing the catch of other unwanted species.

5.7 Implications of reforms in the common fisheries policy

The two proposed reforms to the Common Fisheries Policy (CFP) that are of most relevance to this study are the introduction of a discard ban and achieving a fishing mortality to deliver Maximum Sustainable Yield (MSY). The reforms to the CFP have not yet been finalised and these comments are based on the latest proposals.

Fishermen across Europe have taken a number of good initiatives to decrease discards, but the initiatives are considered to be too scattered across Europe. In the meantime public opinion is quickly building up against what is viewed as a wasteful practice.

The European Commission has stated that ‘...discarding of fish is no longer acceptable. Discarding casts a negative image on the industry and has harmful impacts on sustainable stock exploitation, marine ecosystems, the financial viability of fisheries, and may influence the quality of scientific advice. The elimination of discards must be part of the objectives of the reformed CFP. An obligation for the industry to land catches of regulated species is introduced in the proposed Basic Regulation. This obligation will enter into force by groups of species under an ambitious, but realistic timeline, and will be accompanied by flanking measures. Species with a high expected survival rate when thrown back into the water after being caught should not be covered by the landing obligation’ (EC COM, 2011)

The proposed timeline consists of three steps: pelagic species (in 2014), most of the valuable demersal species, including cod, hake and sole (in 2015), and other species in 2016 (haddock, whiting, megrim, anglerfish, plaice, ling, saithe, pollack, lemon sole, turbot, brill, blue ling, black scabbardfish, roundnose grenadier, orange roughy, Greenland halibut, tusk, redfish and Mediterranean demersal stocks), regardless of whether they are managed with quota or effort. There is currently no list of species that are excluded from the discard ban because they are considered to survive when discarded.

There is a requirement for the scientific community to undertake discard survival rate surveys in order to know exactly what the effects of discarding are in all fisheries. The results from this study are therefore of particular relevance to the proposed reforms to the CFP.

A move to a ‘land-all-catch’ policy is likely to generate changes in fisher’s behaviour. For example, it is expected that there will be an increased incentive to fish more selectively for the species identified in the timeline. This in turn, may improve the selectivity towards other species, including elasmobranchs, and also increase discard survival rates. Other changes may include avoiding catches of juvenile quota species through changes in the spatial and temporal distribution of fishing effort. The implications of these behavioural changes cannot be determined at present.

5.8 Development of regional management plan

Given the important regional differences in the skate fauna around the British Isles, and indeed across the ICES area, more regional management of the skate complex may be better able to target the species and stocks of management concern, and implement more appropriate, pragmatic and effective regional measures. For example, skates within the Celtic Seas eco-region are currently managed with a single TAC for rajids in EC waters of VIa–b and VIIa–c, e–k, despite there being important regional differences within this eco-region. The North Western Waters Regional Advisory Council (NWWRAC) has convened two meetings for a ‘Focus Group on Skates, Rays and Sharks’ (Madrid, 16 September 2011, and Paris, 29 February 2012) to discuss more regional management.

This forum has discussed the potential benefits of re-allocating the TAC for ‘skates and rays (Rajidae)’ to, for example, genus (i.e. to have separate TACs for Raja spp., Leucoraja spp., Dipturus spp. and ‘other rajids’) or possibly individual species (depending on data collection). If such an approach was taken forward and also established on a more regional scale (e.g. by ICES Division or small groups of ICES Division), then this could facilitate more bespoke species- and stock-specific management measures being brought in at a more effective level.

5.9 Management measures for elasmobranchs: The perception of commercial fishers

Many of the respondents to the questionnaire (Annex II) provided suggestions on practical ways of minimising bycatch (Annex IV). Six respondents suggested increasing net mesh sizes and restricting the amount of gear fished. Four respondents thought that there should be minimum and/or maximum landing sizes for elasmobranchs. Four respondents commented that there should be fishing restrictions on known stock hotspots at particular times of the year. Other management suggestions included having a ‘no towed’ gear area and having a bycatch allowance. For declining stocks management measures suggestions included:

• Limiting net sizes for particular fisheries, • Reduction of fishing effort, • Identify stock spawning areas and stop fishing effort at certain times of the year, • Limiting the days at sea for all larger EU and British vessels, • Increased mesh size, • Increased minimum landing sizes

5.10 Future research needs

Further studies are required to make further progress with the national / European management of skate fisheries. These are summarised below under the general fields of life-history information, commercial information, gear modifications, fishery- independent trawl surveys, ecology and behaviour and stock definition. These areas are not prioritised here, as exact data requirements will vary between species and stocks, and also because the perceived importance of the various skate species/stocks will vary between commercial, recreational, scientific and conservation interests.

Life-history information

Although some life-history information (e.g. length at maturity, and age and growth rate) are known for some of the more common species, such as R. clavata, R. montagui and L. naevus (e.g. Ryland & Ajayi, 1984; Walker, 1999), other aspects of the reproductive biology (e.g. fecundity and egg-laying) are little studied. In contrast, data are more limited for some other species (e.g. R. brachyura and R. undulata), and may be based on small sample sizes or only available from elsewhere in Europe. In terms of some offshore species, such as L. circularis and L. fullonica, life-history data are almost entirely lacking. Given that some life-history characteristics (including length at maturity and fecundity) can vary temporally and spatially, more contemporary studies for some species would also be beneficial.

Commercial information

Species-specific data collection has improved in the last few years. It is, however, important to recognise that there are still some issues regarding data quality, and so there is a need for on-going training for fishers and port officials, and quality assurance to further improve the quality of commercial catch data.

Discard observer programmes have provided useful information on the relative quantities discarded, discard-retention patterns and species composition. Further studies for important skate fisheries for which observer coverage is low are required, especially for those longline and gillnet fisheries that may target different species during the course of the year.

Gear modifications

Fishing gear technology offers potential mechanisms to reduce the capture rates of elasmobranchs and/or improve the health state of discarded individuals. Cooperative studies with the fishing industry to try and identify pragmatic and effective solutions to reduce the incidence of elasmobranch bycatch and/or to maximise the chances of discarded elasmobranchs surviving (including improved handling practices) are required for a variety of fisheries.

Fishery-independent trawl surveys

Current trawl surveys have been used by ICES to provide advice on the status of the main skate stocks around the British Isles (including R. clavata, R. montagui and R. microocellata). However, some species are not effectively sampled in these surveys, either because they are inner continental shelf species with patchy distributions (e.g. R. brachyura and R. undulata) or because they are offshore species for which the main area of distribution is not sampled effectively (e.g. L. fullonica and L. circularis). There are potential benefits of having dedicated inshore surveys for the former group if their status is to be more effectively monitored. Collaborative studies with the fishing industry could usefully be undertaken to provide additional information on the latter species.

Ecology and behaviour

Further studies to better understand the movements, migrations and stock mixing of selected skate stocks could usefully be undertaken to (i) better understand the home range of those species which may have restricted habitats (e.g. R. brachyura and R.undulata), (ii) provide supporting evidence to support the delineation of nominal stock units, and (iii) provide information on ‘critical habitats’ for any species for which spatial management is to be considered. Various tagging programmes have helped in the identification of some stock units (e.g. R. clavata in the southern North Sea and eastern English Channel), and improved tagging programmes to help inform on the stock units of species such as L. naevus and R. brachyura could usefully be undertaken. To date, studies using electronic tags on skates around Britain have been broadly restricted to R. clavata and D. batis-complex (e.g. Hunter et al., 2005a; Bendall et al., 2012), and such approaches could provide valuable information on the home range and habitat requirements of those species with more patchy distributions.

Stock definition

Assessment and advice is currently based on nominal stock units. An improved knowledge of stock boundaries can influence advice, as seen in the ICES advice for R. clavata in the southern North Sea. There are several skate stocks for which stock units are unknown (e.g. L. naevus, links between several skate species in the western English Channel with elsewhere), and this hampers appropriate assessments being made. The identification of stocks can be undertaken by a variety of methods, including examining spatial differences in life-history characteristics and biological markers (e.g. parasites), tagging studies and genetic studies (Pawson & Ellis, 2005). Integrated, international studies to better delineate stocks are required.

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Annex I: List of acronyms

BTS Beam Trawl Survey CPOA Community Plan of Action CPUE Catch-per-unit-effort EC / EU European Commission / European Union FV Fishing Vessel GLM Generalized Linear Model GOV Grande Ouverture Verticale (trawl) IBTS International Bottom Trawl Survey ICES International Council for the Exploration of the Seas IFCA Inshore Fisheries and Conservation Authority IPOA International Plan of Action MLL Maximum landing length MLS Minimum landing size MPA Marine Protected Area NWWRAC North Western Waters Regional Advisory Council RV Research Vessel SFC Sea Fishery Committee TAC Total Allowable Catch WGEF Working Group on Elasmobranch Fishes

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Annex II: Questionnaire circulated to gain fishing industry views How to manage sharks, dogfish, skates and rays: Compiling the views of the fishing industry

In recent years the EC have been more active in establishing conservation measures for sharks, dogfish, skates and rays, with TACs for many stocks, landing size restrictions for some species, and other species now listed as ‘prohibited species’ that cannot be retained on board. Some measures are known to be unpopular with the fishing industry.

As part of a Defra-funded project we are asking fishermen to answer a small number of questions so that we can see (i) for which species that fishermen and scientists have similar or dissimilar views on the health of the stocks, and (ii) what measures the fishing industry would view as the best ways to manage shark stocks.

This voluntary questionnaire is divided in 4 parts and should only take about 10-15 minutes of your time.

Please return the questionnaire to Jim Ellis, Cefas, Pakefield Road, Lowestoft, NR33 0HT, Or e-mail to: [email protected]

Part A: General information

Skipper name

(Optional) Vessel name

(Optional)

General fishing area

Gear(s) used

What are the main factors that influence your catches of sharks, skates and rays?

No difficulties  How easy is it for you Other comments: to identify and report your landings of Minor difficulties  sharks, skates and rays by species? Major difficulties 

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Part B: Your perception of the health of shark, skate and ray stocks

What are the most important shark, skate and ray species for you nowadays? What is your view on the states of their populations?

Importance to you What is your view on the health of the population Species 1=very important 3 = little importance Increasing Stable Decreasing Don’t know Blonde ray 1  2  3     

Thornback ray 1  2  3     

Spotted ray 1  2  3     

Cuckoo ray 1  2  3     

Spurdog 1  2  3     

Smooth-hound 1  2  3     

Tope 1  2  3     

Lesser-spotted dogfish 1  2  3     

Porbeagle 1  2  3     

Blue shark 1  2  3     

1  2  3     

Others 1  2  3     

1  2  3     

What do you think are the main factors affecting any changes in shark or skate stocks in your area?

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Part C: Your views on current management

Which of these current measures affect you and do you think they benefit their stocks Do you think it will Does it impact on your landings? benefit the stock? Measure Large Negligible or Small impact Yes No impact no impact Minimum landing size      Maximum landing length      Quota/TAC      Zero TAC      Prohibited listing of undulate ray/common skate      Prohibited listings of white skate and angel shark      Bycatch ratios (e.g. skates can only be x% of catch)      Other      What do you think of the survival of any discards of the main species in your fishery?

Species Gear Survival: 1 = High, 3 = Low

1  2  3 

Part D: What do you think should be done to best manage sharks, dogfish, skates and rays?

Can you think of any practical ways of minimising bycatch of particular species or sizes of shark, skate and ray?

Can you think of any practical ways of increasing the survival chances for any discarded sharks, skates and rays?

For the species that you think have declined, how do you think they should be managed?

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Annex III: Organisations to which the questionnaire was sent

Northumberland IFCA North Eastern IFCA Eastern IFCA Kent and Essex IFCA Sussex IFCA Southern IFCA Devon and Severn IFCA Cornwall IFCA Isles of Scilly IFCA North Western IFCA Cornish Fish Producers Organisation South Western Fish Producers Organisation Fleetwood Fish Producers Organisation Lowestoft Fish Producers Organisation North Sea Fishermen’s Organisation Guernsey Fishermen’s Association Jersey Fishermen’s Association Looe Fishermen’s Protection Association Mevagissey Fishermen’s Protection Association Lowestoft MMO Newlyn Fishing Boat Owner’s Association North Devon Fishermen’s Association Plymouth Fishermen’s Association Port Isaac Fishermen Ltd St Mawes & District Fishermen’s Association Eastbourne Fishermen’s & Boatmen’s Protection Society Folkestone Fishermen’s Association Hastings Fishermen’s Protection Society Newhaven (Sussex) Fish & Flake Ice Society ltd Normans Bay Fishermen’s Association Rye Fishermen’s Association Blyth Fishermen’s Association Bridlington & Flamborough Fishermen’s Society Cullercoats Fishermen’s Association Newbiggin Fishermen’s Association North Shields Fishermen’s Society Humber & East Coast Inshore Fishermen’s Association Lincolnshire Coast Fishermen’s Association Fleetwood Fishermen’s Association Morecambe & Heysham Fishermen’s Association Southport & North Fishermen’s Association Whitehaven Fishermen’s Association

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Annex IV: Comments from commercial fishermen The comments below are provided by respondents, and do not necessarily relate to the views of the report authors, Cefas or Defra. Each questionnaire has been numbered to allow the anonymity of the respondent.

Skipper Fishing ground(s) ICES divisions Gear(s) used* 1 Bristol Channel VIIf Trawl/ scallop dredge 2 Lundy VIIf Trawl/static nets/longline 3 IVc IVc Static nets/longline 4 Plymouth VIIe Trawl 5 Plymouth VIIe Static nets 6 Scarborough IVb Pots 7 VIId VIId Static nets 8 Southwold to N.Foreland IVc Static nets/longline/pots 9 Morecambe Bay VIIa Trawl 10 S.North Sea/Thames/Lowestoft IVc Trawl 11 VII VII Static nets 12 Mounts Bay/S.Scillys/Plymouth VIIe Trawl 13 N. Cornwall/ N.Devon/Lundy/S.Wales VIIf, g Trawl/static nets 14 VIIe,f,g VIIe,f,g Trawl 15 VIIe, f VIIe, f Static nets 16 SW approaches VIIe, f Static nets 17 Bristol Channel/Lundy/S.Wales VIIf Trawl 18 Bristol Channel VIIf Trawl 19 Bristol Channel VIIf Trawl 20 Bristol Channel VIIf Trawl 21 Falmouth/Coverach/Cadgwith VIIe, f Static nets 22 W.English Channel VIId Static nets/longline 23 Bristol Channel VIIf Trawl 24 VIIe VIIe Static nets 25 VIId VIId Trawl 26 VIId VIId Static nets 27 VIId,e,f, g VIId,e,f, g Trawl 28 VIId VIId Static nets/pots

*Gear(s) used: Trawl includes single and twin otter trawls, bottom and pair trawls. Static nets include gill, ray, tangle and trammel nets.

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Q. What are the main factors that influence your catches of sharks, skates and rays?

 “Location on times. Tides are crucial, dropping tides are best for rays, rising tides seem best for spurdog.” (Respondent 1)

 “Dominant species in the area.”( Respondent 2)

 “We have always fished spurdog as part of a mixed fishery but since they have been banned it has had a large effect on our fishery and the grounds that we fish.” (Respondent 3)

 “Prohibited listings (total bans).” (Respondent 4)

 “Areas fished and net size. 12”mesh for skates and rays. Sharks generally deeper nets 6”.” (Respondent 5)

 “Weather – seasonal fisheries. Size of net used, positions of nets.” (Respondent 7)

 “The migration of skate is still the same appearing in our area in December and then moving SW in January or February in large concentrations of fish. Skate move close inshore in early summer and lay close to the beach until October when they start to move off again.” (Respondent 8)

 “Skate is the most important part of my earnings. There is no impact on the fishery in my area as MAFF will agree. Any restrictions will put me out of work.” (Respondent 9)

 “Fishing patterns, mainly spring/summer better catches, tides/weather, quotas.” (Respondent 10)

 “Feed in the area that we are working.” (Respondent 11)

 “Type of bottom being fished.” (Respondent 12)

 “They are in large numbers in the area I fish.” (Respondent 13)

 “Accidental bycatch.” (Respondent 14)

 “14” nets used to target rays seasonally.” (Respondent 15)

 “Not targeted but do catch a lot of sharks, dogs, skate at certain times.” (Respondent 16)

 “Seasons of the year is one of the main factors, and our business has been built up over 25yrs and very much relies upon being able to catch rays and spurs.” (Respondent 17)

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 “Having good ground contact. Having a very good fish sounder. Being able to follow moving ray.” (Respondent 18)

 “No skate caught. Sharks including spurdogs incidental bycatch. Ray are a main target species.” (Respondent 20)

 “Seasons and quotas.” (Respondent 21)

 “If we catch a porbeagle shark in our nets it is always dead so the fish is dumped dead. The fish may be worth £100.” (Respondent 22)

 “Skates and rays.” (Respondent 23)

 “Area fished. More rays to the west, more dogs to the east.” (Respondent 24)

 “Substrate i.e. skate on hard ground not sand.”( Respondent 25)

 “Quotas.”( Respondent 26)

 “Seasonality in a truly mixed fishery. Caught through-out the year but in higher numbers during certain seasons. As a part of a mixed fishery catching in excess of twenty species per trip.”( Respondent 27)

 “The biggest effect is the ban on undulates, as long as they are all returned they are forcing out other species of ray out of the fishing ground. All other species of ray are being forced out. It is impossible to ray net without catching undulates. By returning there is no guarantee of survival (i.e. squashing out of the nets).”( Respondent 28)

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Q. What do you think that are the main factors affecting any changes in shark or skate stocks in your area?

 “Spurdogs seem to be increasing since there is no targeted line fishery but are caught in increasing numbers by nets and trawl. The same goes for the porbeagles by the netters. Rays are pretty stable but increased pressure by netters using trammels not only take out marketable fish but anything that swims.” (Respondent 1)

 “Trevose Box has seen an increase of ray. Spurdog are seasonal Nov-May and seem as plentiful as ever. I’ve been fishing for 25 years in this area. Don’t target porbeagle since there been a stop but angling boats do see a few around.” (Respondent 2)

 “We have a lot of dredging and wind farm construction. Fishing effort in our area is decreasing year on year. Because of quota and the ban on spurdog the longline fleet is decreasing.” (Respondent 3)

 “The use of smaller ray net of 9” takes a considerable number of smaller size blond and thornback rays both of which reach a large size. It is not helpful to use these often finer mesh nets.” (Respondent 5)

 “Effort outside the 6 mile limit by the French, Dutch and Belgium trawlers.” (Respondent 7)

 “No change in spurdog amounts while we were looking for them in their annual run south to the channel in January and then back North in March, April and May. Outside the 2o line skate stocks are still strong in our area and a job to avoid at times in nets or lines.” (Respondent 8)

 “No fishing vessels left in our area. Stocks are very healthy with a high proportion of mixed sizes. No controls needed.” (Respondent 9)

 “We are catching more skate. I do not believe they are overfished in the Thames estuary. The stock is healthy with all sizes caught. I do believe there should be a minimum size to protect the stock.” (Respondent 10)

 “To state the obvious, population depends on fishing effort.” (Respondent 12)

 “Too many boats. Multi rig fishing. Twin rig or triple rig. Also larger mesh size 100mm single twine would help their survival on being returned to the sea.” (Respondent 13)

 “Feed and water temperature.” (Respondent 15)

 “Water temperature, feed in the water causing increasing shark stocks.” (Respondent 16)

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 “The one main factor is not being able to catch spurdog and having to throw them back dead, and putting even more pressure on other species to make the remaining trip profitable. These are not a targeted species they are merely a bycatch as experienced by the endeavour itself! Four tonne I do believe for one haul and they would have witnessed them being dead, I’m sure!” (Respondent 17)

 “Don’t know about sharks and skate but ray is looked after by the strong tides, too much to trawl and weather in Bristol Channel.” (Respondent 18)

 “Fishing by the large trawlers outside the 6/12 mile limit off Lundy island.” (Respondent 19)

 “Spurdog not being fished. All being dumped dead!” (Respondent 23)

 “It’s hard not to over fish species grown big enough to catch, but I would suggest more are under threat of extinction.” (Respondent 24)

 “Population is exploding with rays, probably because of landing restrictions. Smooth hounds are rife, more than ever, probably due to the increase of spider crab for food.” (Respondent 26)

 “In the inshore section of 7d and 7e the reduced fleet size has increased elasmobranch stocks, especially in 7d. Smooth hound and lesser spotted dogs are more prolific than at any time in the last 30 years, probably due to increased food supply in this area (again due to less vessels in catching fleet).”( Respondent 27)

 “Pointless total bans which cause over fishing for other species.”( Respondent 28)

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Q. Can you think of any practical ways of minimising bycatch of particular species or sizes of shark, skate and ray?

Fishing gear  “No way unless mesh sizes are so large nothing would be caught of virtually any species of fish.” (Respondent 1)

 “100mm mesh cod end will give survival/returns better chance due to less sanding/mudding up.” (Respondent 2)

 “Stop multi rigging and a gear size restriction.” (Respondent 13)

 “200mm + mesh size would be the only way but most, probably all commercial species would be lost so not practical.” (Respondent 20)

 “Not in static gear fishery.” (Respondent 26)

 “Limit nets fished and raise mesh sizes.” (Respondent 28)

Minimum/maximum landing size  “With the longline the spurdog will be caught, banning them has made discards. Maybe maximum landing length would help.” (Respondent 3)

 “All trawls to have rock hoppers on clean ground. Minimum of 8”, let small fish pass underneath.” (Respondent 23)

 “Due to the exceptionally high survival rate of elasmobranches, limiting the catching of these species is not the issue. Better to set sensible minimum landing size and maybe maximum on some species of skate/ray so that small and very large are returned to the sea to help biomass.”( Respondent 27)

Avoid known hotspots  “By avoiding specific areas when a high density of fish is pregnant. As spurdogs do not show on fish finder it is only possible to avoid area after initial catch.” (Respondent 5)

 “Skate – avoid areas where concentrations are at certain times of the year and are known to fishermen by their diaries through the years. Spurdogs the same. They show some places each year within a few days every year since have been fishing.” (Respondent 8)

 “Have a no towed gear area/box.” (Respondent 22)

 “This can only be achieved by closing areas down when a certain amount of a targeted species are being caught when they do not meet the minimum size. This must be done by the fishermen themselves.” (Respondent 17)

Bycatch allowance

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 “Landing a bycatch may increase the amount of dead skate being returned to the sea.” (Respondent 10)

 “Do not target fisheries, nothing can be done about bycatch. Chucking back dead fish does not help!” (Respondent 16)

 “Land everything sizeable but only fish for two or three weeks per month.” (Respondent 18)

 “Keep males, return female.” (Respondent 28)

No solution/misc  “No, due to nomadic nature.” (Respondent 15)

 “Leave well alone as it is now.” (Respondent 24)

 “No. It’s not under threat in this area.” (Respondent 9)

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Q. Can you think of any practical ways of increasing the survival chances for any discarded sharks, skates and rays?

 “The elasmobranch survival trials already carried out prove survivability to be near 100% so discarding is a benefit to this stock.” (Respondent 27)

Shorter tows  “Shorter tow times.” (Respondent 1)

 “Survival rates for longline is not a problem. Short soak time on ray nets would increase survival rates.” (Respondent 3)

 “Shorter tows.” (Respondent 18)

 “Only tow gear for maximum of 3 hrs.” (Respondent 19)

 “Mandatory shorter tow periods. Some boats tow for up to 7hrs. Tow period should be 4hrs maximum.” (Respondent 20)

Minimum/maximum landing size  “Increase landing sizes for skate on longlines. Have a maximum size for spurdog on longlines to protect the larger females.” (Respondent 8)

Bycatch allowance  “No. Fish should not be discarded, it does not help. Skate are easily spooked and takes off. Nobody knows how much there is.” (Respondent 9)

 “If the percentage of skate is low for catching sole we will be putting more dead fish back over the rail i.e. if they give us for example 25% skate/for soles. We catch approx 3/4stone soles per haul, we can only keep one decent skate when the stock is healthy.” (Respondent 10)

Fishing gear  “Increase mesh size for more than 30% of the catch being ray/shark to 100mm single twine 3mm twine.” (Respondent 13)

 “100mm mesh cod end will give survival/returns better chance due to less sanding/mudding up.” (Respondent 2)

 “I do not think this can be achieved as there are so many different circumstances i.e. weather, weight in codend.” (Respondent 17)

 “Short of banning commercial fishing, nothing.” (Respondent 24)

 “Return to sea as soon as possible.” (Respondent 12)

 “Other than returning to sea immediately, no.” (Respondent 26)

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Q. For the species that you think have declined, how do you think they should be managed?

Fishing gear/effort

 “A limit on the size of the net used for the particular fishery.” (Respondent 5)

 “They will still be caught and discarded dead if there is no TAC, only way is less boats and pressure inside 15 miles.” (Respondent 1)

 “I don’t know of any species that are still declining, in fact quite the opposite. We just don’t have the TAC’s in balance with most stocks.” (Respondent 11)

 “Blonde ray/spurdog. The biggest change in recent years to the fishing has been since there has been a targeted fishery in the Bristol Channel for ray species. A cut in effort in this area and an introduction of a closed spawning area is a must. The issue of the Belgian fleet fishing on the basis of a scientific survey inside the 12mile limit has had a huge impact. The use of trammel nets targeting ray on the shore on the north coast of Devon and Cornwall has also had an impact. The damage to the spurdog fishery was done years ago with a targeted dog fishery which was from November to June around the coast of Cornwall. You would have to identify the spawning area and put in place measures to stop fisheries which will harm the dogs. The stock is slowly improving.” (Respondent 14)

 “Limit the days at sea for all larger EU and British vessels that fish all weather, 24hr days, 7 days a week.” (Respondent 19)

 “No target fishing. Lining and netting which is the worst form of fishing for a stock; wipes it out. As the netters are wiping out the turbot in the west of the channel at present.” (Respondent 18)

 “For the survival of all species increase in mesh size is the only way and to compensate the fishermen for the change.”( Respondent 28)

Bycatch allowance

 “Stop targeting fisheries but allow reasonable bycatches due to poor survival on discarding.” (Respondent 7)

 “My worse day in fishing career was having to throw away x1 tonne of tope on a netting trip from a two hour soak. What a waste, all dead. (GUTTED!!)” (Respondent 15)

 “I feel there needs to be a way of landing spurdog if caught by mistake i.e. we catch between 1 and 5 spurdogs per year but one net last October for no reason had approx 1200kg. I have fished that spot for approx 30 years and have never seen that before or since.” (Respondent 21)

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 “With spurdog, same as porbeagle, fish are dead so are dumped back dead. Should be a small bycatch.” (Respondent 22)

Minimum/maximum landing size

 “Increase landing sizes for skate on longlines. Have a maximum size for spurdog on longlines to protect the larger females. In my opinion if the above ideas are taken in our area the stocks will be sustainable.” (Respondent 8)

 “You need to increase the minimum landing size on thornback rays.” (Respondent 21)

 “All species should have minimum landing sizes increased. Mesh size restrictions are not so important because fishermen would not work a net to catch fish to throw away (waste of valuable time!). My theory is to let fish reproduce a couple of times then harvest them. Most small fish are of low value.” (Respondent 22)

Miscellaneous

 “There are so few fishing boats left, stocks will increase.” (Respondent 24)

 “I don’t think any species have declined except fishermen. Any more restrictions on how we fish will kill us off!” (Respondent 9)

 “I believe that fishermen themselves must take a greater role in managing skates and rays and the powers that be must start listening to the industry when it says that there are a lot of ray or spurs on the ground, whatever the case may be and move away from throwing the fish back dead then putting more pressure on the fish you are allowed to land. As I have already said I do believe when a certain percentage of your catch is below the minimum landing size (to be agreed) that the area should be closed immediately thus reducing discards. You may be aware that we do believe that the Belgium outriggers have had a massive affect on certain areas of ray stocks under the rights to fish (historic rights), this was granted to them as a beamer not a trawler. In some cases they have decimated ray stocks, this should never have been allowed. Just one more point I would like to make is that you are more than welcome to look at our logbooks and you will see that we have experienced some of the best fishing on rays that we have ever seen in over 20 years. Some of the hauls being well over 1000kilos, the best we have ever seen.” (Respondent 17)

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Annex V: Discard rates of skates and rays in various fisheries. Species codes are BLR = Raja brachyura; THR = R. clavata; PTR = R. microocellata; SDR = R. montagui; UNR = R. undulata; CUR = Leucoraja naevus; SHR = L. fullonica; SKT = Dipturus batis-complex. Metiers as defined in Section 2.10.

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Annex V (cont.): Discard rates of skates and rays in various fisheries. Species codes are BLR = Raja brachyura; THR = R. clavata; PTR = R. microocellata; SDR = R. montagui; UNR = R. undulata; CUR = Leucoraja naevus; SHR = L. fullonica; SKT = Dipturus batis-complex. Metiers as defined in Section 2.10.

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