national evaluation of populations of threatened and...

Project Code: MB5201

National Evaluation of Populations of Threatened and

Uncertain Elasmobranchs (NEPTUNE)

Authors: J. R. Ellis, V. A. Bendall, S. J. Hetherington, J. F. Silva

and S. R. McCully Phillips.

Issue date: 15-Jan-2016

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page i

Cefas Document Control

Title: National Evaluation of Populations of Threatened and



Submitted to: Defra

Date submitted: 15-Jan-2016

Project Manager: Jim Ellis

Project Sponsor: Wendy Dawson

Report compiled by: Jim Ellis, Vicky Bendall, Stuart Hetherington, Joana Silva and Sophy McCully Phillips

Quality control by: David Righton

Approved by &

date:

Version: V1.4

Suggested citation

Ellis, J. R., Bendall, V. A., Hetherington, S. J., Silva, J. F. and McCully Phillips, S. R. (2015). National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE). Project Report (Cefas), x + 105 pp.

Version Control History

Author Date Comment Version

Ellis et al. 25 Feb 2015 Initial draft V1.0

Ellis et al. 26 Feb 2015 Edits made by JE and SM V1.1

Ellis et al. 04 Mar 2015 QA by DR, further edits by JE/SM V1.2

Ellis et al. 24 Jul 2015 Following comments from PSG V1.3

Ellis et al. 15 Jan 2016 Final version after external review V1.4

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page ii

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page iii


National Evaluation of Populations of Threatened and


Authors: J. R. Ellis, V. A. Bendall, S. Hetherington, J. F. Silva and S. R.

McCully Phillips

Issue date: 15-Jan-2016

Head office

Centre for Environment, Fisheries & Aquaculture Science

Pakefield Road, Lowestoft, Suffolk NR33 0HT, UK

Tel +44 (0) 1502 56 2244 Fax +44 (0) 1502 51 3865

www.cefas.defra.gov.uk

Cefas is an executive agency of Defra

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page iv

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page v

Table of contents

Informing policy .................................................................................................................................... 1

1 Introduction ................................................................................................................................... 3

1.1 Background ............................................................................................................................. 3

1.2 Project background ................................................................................................................. 4

1.3 Format of the report ............................................................................................................... 5

2 Elasmobranchs of the British Isles and prioritisation of species of interest ......................... 7

Summary ............................................................................................................................................. 7

2.1 Elasmobranchs of the British Isles .......................................................................................... 8

2.2 Prioritising elasmobranchs and holocephalans of interest .................................................. 13

2.3 Productivity Susceptibility Analyses ..................................................................................... 17

3 Elasmobranch bycatch in the Celtic Sea .................................................................................. 25

Summary ........................................................................................................................................... 25

3.1 Introduction .......................................................................................................................... 26

3.2 Stakeholder engagement ...................................................................................................... 26

3.3 Approach and data collection ............................................................................................... 27

3.4 Catches of spurdog, common skate and porbeagle ............................................................. 31

3.5 Tagging studies and biological information .......................................................................... 40

3.6 At-vessel mortality ................................................................................................................ 42

3.7 Best practice in handling elasmobranchs and developing a ‘Code of conduct’ ................... 44

3.8 Lessons learnt: Advantages and limitations of fisher-collected data ................................... 47

4 Biological investigations of elasmobranchs ............................................................................ 49

Summary ........................................................................................................................................... 49

4.1 Introduction .......................................................................................................................... 50

4.2 Starry smooth-hound Mustelus asterias .............................................................................. 53

4.3 Spurdog Squalus acanthias ................................................................................................... 61

4.4 Porbeagle Lamna nasus ........................................................................................................ 69

4.5 Other biological investigations ............................................................................................. 73

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page vi

5 Concluding remarks ................................................................................................................... 77

6 Acknowledgments ...................................................................................................................... 81

7 References ................................................................................................................................... 82

8 Annexes ....................................................................................................................................... 87

8.1 List of acronyms .................................................................................................................... 87

8.2 Outputs from project and associated work .......................................................................... 88

8.3 Taxonomic list of chondrichthyans of the British Isles and adjacent waters ........................ 91

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page vii

Figures

Figure 1. Diversity of the elasmobranch fauna of the British Isles, showing (a) spurdog, (b) angel

shark, (c) porbeagle, (d) blue shark, (e) tope, (f) starry smooth-hound, (g) lesser-spotted dogfish, (h)

greater-spotted dogfish, (i) common stingray and (j) electric ray .......................................................... 9

Figure 2. Diversity of the elasmobranch fauna of the British Isles, showing (a) starry ray, (b) blue

skate, (c) sandy ray, (d) shagreen ray, (e) cuckoo ray, (f) blonde ray, (g) thornback ray, (h) small-eyed

ray, (i) spotted ray and (j) undulate ray. ............................................................................................... 10

Figure 3: PSA plot indicating vulnerabilities of Celtic Sea elasmobranchs in the demersal gillnet

fishery. Species codes given in Table 9. ................................................................................................ 24

Figure 4: PSA plot indicating vulnerabilities of Celtic Sea elasmobranchs in the demersal otter trawl

fishery. Species codes given in Table 9. ................................................................................................ 24

Figure 5: Disentangling a common skate from fishing gear ................................................................. 28

Figure 6. Main fishing grounds of Vessel A when setting gillnets. ....................................................... 32

Figure 7. Main fishing grounds of Vessel A when setting tangle nets. ................................................. 33

Figure 8. Main fishing grounds of Vessel B when setting gillnets. ........................................................ 34

Figure 9. Main fishing grounds of Vessel C when setting gillnets. ........................................................ 36

Figure 10. Main fishing grounds of Vessel C when setting tangle nets. ............................................... 37

Figure 11. Spatial distribution of spurdog bycatch observed by ICES rectangle .................................. 38

Figure 12. Spatial distribution of porbeagle bycatch observed by ICES rectangle ............................... 39

Figure 13. Spatial distribution of common skate bycatch observed by ICES rectangle ........................ 39

Figure 14. Length frequency of Dipturus spp. tagged and released, showing those identified as

Dipturus batis (BSKT), Dipturus cf. intermedia (FSKT) and Dipturus batis-complex (SKT) .................... 41

Figure 15. Relationship between disc width and total length in Dipturus batis ................................... 41

Figure 16. Length frequency of spurdog Squalus acanthias tagged and released ............................... 42

Figure 17. Length frequency of undulate ray Raja undulata tagged and released .............................. 42

Figure 18. Example ‘Code of Conduct’ .................................................................................................. 46

Figure 19. Length frequency distribution of starry smooth-hound examined by sex .......................... 54

Figure 20. Relationship between total weight and total length in starry smooth-hound by sex and

maturity stage ....................................................................................................................................... 55

Figure 21. Relationship between gutted weight and total length in starry smooth-hound by sex ...... 55

Figure 22. Relationship between liver weight and total length by sex ................................................. 56

Figure 23. Relationship between gonad weight and total length by sex and maturity stage .............. 57

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page viii

Figure 24. Relationship between width of the shell (or nidamental) gland and total length in female

starry smooth-hound by maturity stage ............................................................................................... 58

Figure 25. Relationship between outer clasper length and total length in male starry smooth-hound

by maturity stage .................................................................................................................................. 58

Figure 26. Relationship between uterine fecundity (embryos and term pups) and maternal total

length in starry smooth-hound ............................................................................................................. 59

Figure 27. Relationship between the average length (left) and average weight (right) of term pups in

relation to maternal length for starry smooth-hound ......................................................................... 60

Figure 28. Length frequency of spurdog examined by sex (black = female, n=307; grey = male, n=

803) ....................................................................................................................................................... 62

Figure 29. Relationships between total weight and total length by maturity stage for female (n = 301)

and male (n = 792) spurdog .................................................................................................................. 64

Figure 30. Relationship between gutted weight and total length in female (n = 301) and male (n =

793) spurdog ......................................................................................................................................... 64

Figure 31. Relationship between gonad weight and total length by maturity stage for female (n =

298) and male (n = 793) spurdog .......................................................................................................... 65

Figure 32. Relationship between width of the nidamental gland and total length in female spurdog (n

= 300) .................................................................................................................................................... 66

Figure 33. Relationship between inner and outer clasper length and total length in male spurdog by

maturity stage ....................................................................................................................................... 67

Figure 34. Ovarian (mature follicles) and uterine fecundity (embryos and term pups) in relation to

maternal total length (n = 151 and 85, respectively) in spurdog. Some of these fish may have aborted

some pups during capture .................................................................................................................... 68

Figure 35. Average total length (left) and average weight (right) of term pups in relation to maternal

total length (n = 49) in spurdog ............................................................................................................ 68

Figure 36. Relationships between inner clasper length (taken as the distance from the anterior

margin of the cloaca to the tip of the clasper) for male porbeagle (n = 33) for developing (open

circles) and mature (closed circles) fish. Total length refers to total length with the upper lobe of the

caudal fin depressed, measured under the body ................................................................................. 71

Figure 37. Length-weight relationships for porbeagle (n = 53) for (a) total weight and (b) gutted

weight. Total length refers to total length with the upper lobe of the caudal fin depressed, measured

under the body ..................................................................................................................................... 72

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page ix

Tables

Table 1. Taxonomic list of elasmobranchs and holocephalans occurring around the British Isles and

adjacent waters (See Annex 8.3 for more comprehensive details). ..................................................... 11

Table 2. Scores applied to elasmobranch and holocephalan fishes in relation to conservation interest

.............................................................................................................................................................. 14

Table 3. Scores applied to elasmobranch and holocephalan fishes in relation to commercial

importance ............................................................................................................................................ 14

Table 4. Scores applied to elasmobranch and holocephalan fishes in relation to biological sensitivity

.............................................................................................................................................................. 15

Table 5. Scores applied to elasmobranch and holocephalan fishes in relation to the importance of UK

waters to the species range .................................................................................................................. 15

Table 6. Highest scoring elasmobranch fishes ...................................................................................... 17

Table 7: Productivity attributes used in the PSA. Those in normal font were as used in the NOAA PSA

framework, parameters modified from NOAA are shown in bold, and additional parameters shown in

bold italics. ............................................................................................................................................ 21

Table 8: Susceptibility attributes used in this study. Those in normal font are taken from the NOAA

PSA framework, those in bold are modified parameters, and added parameters are denoted by bold

italics. .................................................................................................................................................... 22

Table 9: Results of the PSA vulnerabilities and overall rankings for elasmobranchs that may be

encountered in otter trawl and gillnet fisheries in the Celtic Sea. Productivity is species-specific and

does not change between fisheries, whilst susceptibility scores are fishery-specific). ........................ 23

Table 10. Details of the three vessels participating in the “Shark, Skate and Ray Scientific bycatch

fishery”. ................................................................................................................................................. 29

Table 11. Summary details of commercial trips for which data were collated. Note: trips marked [1]

and [2] only provided information for porbeagle and common skate, respectively. ........................... 30

Table 12. Reported catches by Vessel A of spurdog (estimated biomass) and porbeagle (number)

caught in gillnets per trip and in relation to the reported retained catch of the main species (hake

and pollack, ‘na = data not available). Data aggregated at a trip level. For those sets where spurdog

were counted, the biomass was estimated based on an average weight of 3.5 kg per fish. ............... 32

Table 13. Reported catches by Vessel A of Dipturus spp. (estimated biomass for all species in the

genus) caught in tangle nets per trip and in relation to the reported retained catch of the main

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page x

species (anglerfish and turbot). Data aggregated at a trip level. For those sets where common skate

were counted, the biomass was estimated based on an average weight of 10 kg per fish. ................ 33

Table 14. Reported quantities of spurdog caught by Vessel B in relation to the main target species

(pollack and saithe) between November 2013 and March 2014. Data shown by set, as spurdog were

either enumerated, or the catch was estimated based on the number of fish boxes. ........................ 35

Table 15. Summary details of the quantities of spurdog caught in relation to the main target species

(pollack, cod and saithe) by Vessel C between December 2013 and March 2014, and between during

October and December 2014. Catch data aggregated across trips. ..................................................... 37

Table 16. Summary details of the quantities of Dipturus spp. caught in tangle nets in relation to the

main target species (turbot and anglerfish) by Vessel B during three trips in 2014. Catch data

aggregated across trips. ........................................................................................................................ 37

Table 17. Numbers of elasmobranchs tagged and released during the pilot programme ................... 40

Table 18. Preliminary estimates of at-vessel mortality of porbeagle as reported by fishers on

commercial netters ............................................................................................................................... 43

Table 19. Preliminary estimates of at-vessel mortality of common skate complex as reported by

fishers retrieving tangle nets (Vessel A only) ........................................................................................ 43

Table 20. Maturity scale for viviparous sharks. Adapted from ICES (2009) .......................................... 52

Table 21. Hepatosomatic index (IH) of starry smooth-hound by sex and maturity stage ..................... 56

Table 22. Mean gonad weight and gonadosomatic index (IG) by sex and maturity stage of starry

smooth-hound ...................................................................................................................................... 57

Table 23. Summary of numbers (by sex) and length range of spurdog retained during the project ... 62

Table 24. Numbers of samples collected for future studies (preliminary) ........................................... 63

Table 25. Mean gonad weight (g) and gonadosomatic index (IG) by sex and maturity stage .............. 65

Table 26. Relationships between alternative length measurements with total length in porbeagle (n =

53), where total length refers to the total length with the upper lobe of the caudal fin flexed down

(LT_under) and measured under the body. Relationships given as an equation and in proportional terms

(percentage of LT_under). ......................................................................................................................... 71

National Evaluation of Populations of Threatened and Uncertain Elasmobranchs (NEPTUNE) Page 1

Informing policy

Approximately 80 species of chondrichthyan fish (sharks, skates, rays and rabbitfish) occur

around the British Isles. Only one species (spurdog) currently has a benchmarked stock

assessment. Indices of relative abundance are currently used to inform on the status of the more

commonly occurring demersal species. There is a clear need to increase our understanding of

data-limited species, and to ensure that appropriate data are available to undertake more

quantitative stock assessments in the future.

A prioritisation process, incorporating commercial importance, conservation interest and

biological vulnerability, identified species which may be of greater relevance to the ‘Shark, Skate

and Ray Conservation Plan’. High ranking species included those of conservation interest (e.g.

flapper skate, angel shark and white skate), commercial importance (e.g. starry smooth-hound

and cuckoo, spotted, blonde and thornback ray) and species that have been of recent commercial

interest as well as conservation concern (e.g. blue skate, porbeagle, undulate ray and spurdog).

Productivity-Susceptibility Analyses were used to provide a semi-quantitative approach to

identifying vulnerable stocks for case-study fisheries. The species ranked as most vulnerable in

the Celtic Sea (e.g. angel shark, spurdog and tope) already have some form of restrictive

management in place at the present time. Species that are subject to commercial exploitation in

the Celtic Sea and ranked as vulnerable, but for which ICES has unable to gauge stock status,

included blonde ray, shagreen ray and starry smooth-hound.

A pilot project was undertaken in collaboration with commercial fishers to collect data on

common skate, spurdog and porbeagle in the Celtic Sea. Fishing opportunities for these species

ceased over the period 2009–2011, through either prohibited status or a zero Total Allowable

Catch. These three species can all be locally and/or seasonally common in the Celtic Sea and are

often caught in commercial gears, including gillnet and tangle net fisheries.

Spurdog were taken in high numbers as a bycatch in the Celtic Sea. In the most extreme cases,

the estimated biomass of spurdog caught exceeded the retained biomass of the main target

species. Catches of spurdog were variable, due to the aggregating nature of the species (which

may be influenced by seasonal factors) and as to whether fishing operations coincided with the

locations of any aggregation.


Porbeagle bycatch in the Celtic Sea was highly seasonal, with the largest catches reported from

August to October. The majority of porbeagle caught in gillnets did not survive. At-vessel

mortality of porbeagle in set nets ranged from 56–97% in two of the vessels studied, with the

former based on a small sample size. Across all trips, at-vessel mortality was >90%.

Catches of the common skate complex were comprised mostly of the smaller of the two species

(Dipturus batis), and this species could be taken in high numbers in tangle net fisheries.

Estimated at-vessel mortality was ca. 34–39%, which is higher in comparison to those gillnet

fisheries with shorter soak times.

Biological sampling has enabled recent life history data to be collected for spurdog, starry

smooth-hound and porbeagle. Data collection focused on those parameters relating to the

reproductive biology which are required for future stock assessments and can provide evidence

to support biologically meaningful management measures. In total 1,112 spurdog (307 females;

805 males); 430 starry smooth-hound (231 females; 199 males) and 53 porbeagle were sampled.

Biological sampling of porbeagle sharks provided length conversion factors and biological samples

for future studies, including contaminant levels and growth studies. Biological samples (including

vertebrae and fin clips) were collected for spurdog and starry smooth-hound. These samples will

allow contemporary data on the age and growth of these species to be collected.

The size at maturity of spurdog does not appear to have changed over time, but fecundity may

have increased. Female spurdog matured across the length range of 79–86 cm, with 50% maturity

at about 82 cm - similar to previously published estimates. The maximum fecundity reported was

19 pups - higher than values reported in the 1960s. This provides further credence to the

hypothesis that the fecundity of spurdog has increased.

Starry smooth-hound is of increasing interest to UK fisheries. The data collected will provide

input data to future assessment models. Females usually matured across the 78–87 cm length

range, and males across the 65–74 cm length range. Ovarian and uterine fecundity ranged from

1–28 and 4–20, respectively. The number of pups increased with maternal size. Larger females

produced bigger pups.

Starry smooth-hound is probably the only smooth-hound species to occur in British waters.

Genetic tissue samples from over 300 starry smooth-hound contributed to a larger-scale

collaborative study across the Northeast Atlantic. No common smooth-hound have been recorded

in the study.


1 Introduction

1.1 Background

Sharks, skates and rays (Elasmobranchs) are key predators in the marine ecosystem. They are

important to commercial and recreational fisheries. Elasmobranch populations are often susceptible

to over-exploitation and slow to recover, due to their longevity, late age at maturity, slow growth rate

and low fecundity (Holden, 1974; Ellis et al., 2008). However, there are still important gaps in our

knowledge of elasmobranchs which restricts our ability to assess and monitor various stocks, and

manage their fisheries.

There has been increased interest in elasmobranch fisheries. In 1999 the Food and Agriculture

Organisation (FAO1) published the voluntary International Plan of Action (IPOA) for the conservation

and management of sharks2 (FAO, 1999), which encouraged nations to establish national plans of

action. Following the subsequent European Community (EC) Plan of Action for Sharks (CEC, 2009),

Defra developed a ‘Shark, Skate and Ray Conservation Plan’ (Defra, 2011) that aims to “manage

elasmobranch stocks sustainably so that depleted stocks recover and that those faring better are fished

sustainably”. Key to this plan is that “Knowledge on elasmobranch fisheries and species is improved

through better data collection and scientific research” so that appropriate ecological information can

be “used to more effectively manage elasmobranchs” (Defra, 2011).

The assessments for many of the elasmobranch stocks around the British Isles are undertaken under

the auspices of the International Council for the Exploration of the Seas (ICES), and their Working

Group on Elasmobranch Fishes (WGEF)3. Although the ICES first convened a Study Group on

Elasmobranch Fisheries in 1989, the lack of data hampered attempts to assess the stocks, and it did

not meet again until 1995, when the Study Group on Elasmobranch Fishes (SGEF) was initiated. The

initial meetings of this group provided descriptions of the fisheries, and collated landings data and

biological information. Given the need for the ICES to provide regular advice to the EC, the SGEF

1 A summary list of acronyms is given in Annex 8.1 2 In general, ‘shark’ action plans tend to consider all chondrichthyan fish, which includes both sharks, dogfish, skates and rays (Class Elasmobranchii), as well as the rabbitfish, or chimaeras (Class Holocephali).

3 The International Commission for the Conservation of Atlantic Tunas (ICCAT) is the body responsible for the assessments of the main pelagic species that occur over the wider Atlantic Ocean


became the Working Group on Elasmobranch Fish (WGEF) in 2003 and has helped in the provision of

ICES advice since 2004.

ICES currently have only bench-marked one assessment for an elasmobranch stock: spurdog in the

Northeast Atlantic (De Oliveira et al., 2013; ICES, 2013). Whilst exploratory assessments have been

undertaken for some other stocks, including deep-water sharks, the main source of data currently

used to evaluate the status of demersal elasmobranchs, including skates (Rajidae), catsharks

(Scyliorhinidae) and smooth-hounds (Triakidae), are scientific trawl surveys. These surveys are

thought to be effective for smaller-bodied species that are widespread across the survey areas, but

data are more limited for larger-species species and those with patchy distributions.

Given the limitations of existing data to understanding the nature and status of elasmobranchs stocks

that are of national interest, a variety of Defra-funded projects have been undertaken by Cefas,

including:

Bristol Channel ray survival (Catchpole et al., 2007)

Thames ray tagging and survival (Ellis et al., 2008)

Spurdog in the Irish Sea (Ellis et al., 2010)

Spurdog, porbeagle and common skate bycatch and discard reduction (Bendall et al., 2012)

Assessing the survivability of bycaught porbeagle and spurdog and furthering our

understanding of their movement patterns in UK marine waters

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

experimental results (Ellis et al., 2012b)

Monitoring thornback ray movements and assessing stock levels (McCully et al., 2013)

1.2 Project background

The current project, entitled “National Evaluation of Populations of Threatened and Uncertain

Elasmobranch stocks (NEPTUNE)” was designed to improve our knowledge of those elasmobranch

fishes that are either considered ‘threatened’ or that are of uncertain status. The project aimed to

support both Defra’s ‘Shark, Skate and Ray Conservation Plan’ and the assessment and advisory

process conducted through the ICES, by providing relevant scientific information to the WGEF.


The project had two main work packages, (i) a bycatch monitoring and mitigation programme for

elasmobranch catches in the Celtic Sea; and (ii) a synthesis of our current knowledge of the status and

biology of UK elasmobranchs, with a prioritisation of species and stocks for further study and

associated data collection to provide relevant biological data for those stocks ranked as important.

Synthesis of current knowledge and identification of data gaps: To help identify the priorities for future

study, the elasmobranchs occurring around the British Isles were prioritised in terms of their

commercial and conservation importance, biological sensitivity and also the importance of the UK to

the stock in question (Section 2). For the highest ranking species, data gaps and uncertainties that

need to be addressed for appropriate assessments to be undertaken were identified, and studies to

address some of these data gaps undertaken (Section 4).

Bycatch monitoring in the Celtic Sea: Development of pragmatic management measures for what are

often regarded as some of the more ‘threatened’ elasmobranchs in British waters is currently

hampered by limited data on their distribution and abundance, necessitating a precautionary

approach. This part of the project involved collaboration with commercial fishermen in the south-

west, to facilitate the collection of more detailed information on species that are of conservation

interest and had also been of commercial interest prior to restrictive management, such as spurdog

Squalus acanthias, common skate Dipturus batis-complex and porbeagle Lamna nasus.

This case study aimed to improve the availability of fishery-dependent information for assessing the

fishery and status of the stocks, with participating fishermen trained to collect data on catch

composition (Section 3). A proportion of dead bycatch was retained (under dispensation) by a small

number of vessels for biological sampling (Section 4). Fishermen were also involved in the

development of a “Code of conduct‟ for elasmobranch bycatch.

1.3 Format of the report

The initial work undertaken was to update the inventory of the elasmobranchs and holocephalans

(chimaeras or rabbitfish) fishes occurring around the British Isles, prioritising species of interest and

identifying data gaps. The work undertaken during this first phase of the project is summarised in

Section 2. There has been an increased interest in Productivity Susceptibility Analyses (PSAs) as an

approach to better understand data limited stocks taken in multi-species fisheries. Preliminary work


on this topic had been undertaken during previous Defra-funded projects, and a specific case study to

examine elasmobranchs in the wider Celtic Sea was also undertaken (Section 2).

Studies on the elasmobranch bycatch taken by gillnetters operating in the Celtic Sea (Section 3) were

undertaken under a “Shark, Skate and Ray Scientific Bycatch Fishery”. This part of the project involved

regular meetings with fishers and other stakeholders. Data on the seasonal bycatch of spurdog,

porbeagle and common skate complex were collected in relation to the associated catches of

commercial fish. A ‘code of conduct’ to promote the safe and effective release of live fish was

developed. The “Shark, Skate and Ray Scientific Bycatch Fishery” associated with this study also

enabled samples of dead bycatch to be landed for scientific study.

Updated biological data were collected for various elasmobranch species (Section 4). Samples of

spurdog and porbeagle were available from the dead bycatch of the Celtic Sea case study. Biological

data were also collected for starry smooth-hound Mustelus asterias, given that this species had been

little studied, ranked high on the prioritisation exercise and has been subject to increased exploitation

in recent years.

Some of the work undertaken during the project has been written up as working documents that were

presented at annual meetings of the ICES WGEF. These and other outputs are summarised in Annex

8.2, with summary information provided in the main body of the report (Section 4.5).


2 Elasmobranchs of the British Isles and prioritisation of species of interest

Summary

An up-to-date inventory of sharks, skates, rays and rabbitfish occurring around the British Isles

was compiled. Of the approximately 80 species, only one (spurdog) currently has a benchmarked

stock assessment. The status of several others is evaluated regularly by ICES, but the status of

several of the species that are of interest to national fisheries remains uncertain.

A prioritisation exercise was conducted to identify the species of greater relevance for the ‘Shark,

Skate and Ray Conservation Plan’. Whilst several of these ranked highly in terms of their

conservation interest (e.g. flapper skate, angel shark and white skate), some data-limited species

of commercial interest also ranked highly (e.g. starry smooth-hound and blonde ray). Other

species that ranked highly were those that were of recent commercial interest but are also of

conservation concern (e.g. blue skate, porbeagle, undulate ray and spurdog).

Productivity-Susceptibility Analyses were used to provide a semi-quantitative approach to

identifying vulnerable stocks for specific fisheries. The species ranked as most vulnerable in the

Celtic Sea already have some form of restrictive management in place at the present time. The

species that are subject to commercial exploitation and ranked of intermediate vulnerability, but

for which ICES has unable to gauge stock status, included blonde ray, shagreen ray and starry

smooth-hound. The species that ranked least in their vulnerability (including thornback, spotted

and cuckoo ray and lesser-spotted dogfish) are generally species for which ICES has been able to

provide advice.

Given the precautionary approach to fisheries management, it will become increasingly important

to be able to evaluate the statuses of those species of intermediate vulnerability, so as to ensure

that their exploitation is sustainable.


2.1 Elasmobranchs of the British Isles

The British Isles has a relatively diverse elasmobranch fauna, including a variety of sharks (Figure 1)

and skates (Figure 2). Whilst the majority of sharks occurring around the British Isles are deep-water

species, there are several species that occur on the continental shelf that are of either conservation

interest or commercial importance. The skates (Rajidae) form the most diverse family of

elasmobranchs in the shelf seas of the British Isles.

Although there have been several earlier taxonomic lists of the elasmobranchs occurring around the

British Isles (Wheeler, 1992; Edwards and Edwards, 1987; Wheeler et al., 2004; Fowler et al., 2004;

George, 2009), changes in the taxonomy of certain taxa and reports of new species has necessitated

an updated list. Wheeler (1992) originally listed 39 elasmobranchs and one rabbitfish (holocephalan)

as occurring in the shelf seas around the British Isles, with deep-water species mostly excluded. Some

deep-water species were included by Edwards and Davis (1987), with 49 elasmobranchs and one

holocephalan listed. More recently, Fowler et al. (2004) listed 68 chondrichthyans from British and

adjacent waters and Wheeler et al. (2004) reported 71 elasmobranchs and six holocephalans from

around the British Isles.

This report provided an up-to-date inventory of the elasmobranchs of the British Isles, updates their

taxonomic names where appropriate, and provides sources of information to better document the

evidence for their occurrence in the waters around the British Isles (Annex 8.3). The higher taxonomic

ordering of Eschemeyer (2012) is followed. This updated taxonomic list included 80 species of

chondrichthyan fish that have been reported from around the British Isles (Table 1), with information

for a further 13 species that are either based on questionable records, reported from adjacent waters

or have been found washed ashore in neighbouring areas also given (Annex 8.3).


Figure 1. Diversity of the elasmobranch fauna of the British Isles, showing (a) spurdog, (b) angel shark, (c) porbeagle, (d) blue shark, (e) tope, (f) starry smooth-hound, (g) lesser-spotted dogfish, (h) greater-spotted dogfish, (i) common stingray

and (j) electric ray

(b)(a)

(c) (d)

(e) (f)

(g)

(i)

(h)(j)


Figure 2. Diversity of the elasmobranch fauna of the British Isles, showing (a) starry ray, (b) blue skate, (c) sandy ray, (d) shagreen ray, (e) cuckoo ray, (f) blonde ray, (g) thornback ray, (h) small-eyed ray, (i) spotted ray and (j) undulate ray.

(a) (b)

(g)(f)(e)

(c)(d)

(h)

(j)

(i)


Table 1. Taxonomic list of elasmobranchs and holocephalans occurring around the British Isles and adjacent waters (See Annex 8.3 for more comprehensive details).

Family Common name Scientific name and authority

CLASS ELASMOBRANCHII

ORDER HEXANCHIFORMES

1 Hexanchidae Bluntnose six-gill shark Hexanchus griseus (Bonnaterre, 1788)

2 Sharpnose seven-gill shark Heptranchias perlo (Bonnaterre, 1788)

3 Chlamydoselachiidae Frilled shark Chlamydoselachus anguineus Garman, 1884

ORDER LAMNIFORMES

4 Lamnidae Shortfin mako Isurus oxyrinchus Rafinesque, 1810

5 Porbeagle shark Lamna nasus (Bonnaterre, 1788)

6 Cetorhinidae Basking shark Cetorhinus maximus (Gunnerus, 1765)

7 Alopiidae Big-eye thresher shark Alopias superciliosus (Lowe, 1841)

8 Thresher shark Alopias vulpinus (Bonnaterre, 1788)

ORDER CARCHARHINIFORMES

9 Scyliorhinidae White ghost catshark Apristurus aphyodes Nakaya & Stehmann, 1998

10 Iceland catshark Apristurus laurussonii (Saemundsson, 1922)

11 Ghost catshark Apristurus manis (Springer, 1979)

12 Black roughscale catshark Apristurus melanoasper

13 Smalleye catshark Apristurus microps (Gilchrist, 1922)

14 Black-mouth dogfish Galeus melastomus Rafinesque, 1810

15 Mouse catshark Galeus murinus (Collett, 1904)

16 Lesser-spotted dogfish Scyliorhinus canicula (Linnaeus, 1758)

17 Greater-spotted dogfish Scyliorhinus stellaris (Linnaeus, 1758)

18 Pseudotriakidae False catshark Pseudotriakis microdon Capello, 1867

19 Triakidae Starry smooth- hound Mustelus asterias Cloquet, 1821

20 Smooth-hound Mustelus mustelus (Linnaeus, 1758) 4

21 Tope shark Galeorhinus galeus (Linnaeus, 1758)

22 Carcharhinidae Blue shark Prionace glauca (Linnaeus, 1758)

23 Sphyrnidae Smooth hammerhead Sphyrna zygaena (Linnaeus, 1758)

ORDER SQUALIFORMES

24 Dalatiidae Kitefin shark Dalatias licha (Bonnaterre, 1788)

25 Etmopteridae Black dogfish Centroscyllium fabricii (Reinhardt, 1825)

26 Great lantern shark Etmopterus princeps Collett, 1904

27 Velvet belly Etmopterus spinax (Linnaeus, 1758)

28 Somnosidae Portuguese dogfish Centroscymnus coelolepis Bocage & Capello, 1864

4 Whilst Mustelus mustelus was originally included in this list, recent examination of museum specimens would suggest that this species occurs off western Africa and in the Mediterranean Sea and may not occur in British seas (E. Farrell, S. McCully and J. Ellis, pers. obs.)



29 Longnose velvet dogfish Centroselachus crepidater (Bocage & Capello, 1864)

30 Knifetooth dogfish Scymnodon ringens Bocage & Capello, 1864

31 Greenland shark Somniosus microcephalus (Bloch & Schneider, 1801)

32 Oxynotidae Angular roughshark Oxynotus centrina (Linnaeus, 1758)

33 Sailfin roughshark Oxynotus paradoxus Frade, 1929

34 Centrophoridae Leafscale gulper shark Centrophorus squamosus (Bonnaterre, 1788)

35 Birdbeak dogfish Deania calcea (Lowe, 1839)

36 Rough longnose dogfish Deania hystricosa (Garman, 1906)

37 Squalidae Spurdog Squalus acanthias Linnaeus, 1758

38 Little gulper shark Squalus uyato Rafinesque, 1810

39 Echinorhinidae Bramble shark Echinorhinus brucus (Bonnaterre, 1788)

ORDER SQUATINIFORMES

40 Squatinidae Angel shark Squatina squatina (Linnaeus, 1758)

ORDER TORPEDINIFORMES

41 Torpedinidae Common electric ray Torpedo (Tetronarce) nobiliana Bonaparte, 1835

42 Marbled electric ray Torpedo (Torpedo) marmorata Risso, 1810

ORDER RAJIFORMES

43 Arhynchobatidae Pale ray Bathyraja pallida (Forster, 1967)

44 Richardson's ray Bathyraja richardsoni (Garrick, 1961)

45 Spinytail ray Bathyraja spinicauda (Jensen, 1914)

46 Unknown deep-water ray Bathyraja sp.

47 Rajidae Arctic skate Amblyraja hyperborea (Collett, 1879)

48 Jensen’s skate Amblyraja jenseni (Bigelow & Schroeder, 1950)

49 Starry ray Amblyraja radiata (Donovan, 1808)

50 Blue skate Dipturus batis (Linnaeus, 1758)

51 Flapper skate Dipturus cf. intermedia (Parnell, 1837)

52 Norwegian skate Dipturus nidarosiensis (Storm, 1881)

53 Long-nose skate Dipturus oxyrinchus (Linnaeus, 1758)

54 Sandy ray Leucoraja circularis (Couch, 1838)

55 Shagreen ray Leucoraja fullonica (Linnaeus, 1758)

56 Cuckoo ray Leucoraja naevus (Müller & Henle, 1841)

57 Krefft's ray Malacoraja kreffti (Stehmann, 1977)

58 Soft (Prickled) skate Malacoraja spinacidermis (Barnard, 1923)

59 Blue pygmy skate Neoraja caerulea (Stehmann, 1976)

60 Blonde ray Raja brachyura Lafont, 1873

61 Thornback ray Raja clavata Linnaeus, 1758

62 Small-eyed ray Raja microocellata Montagu, 1818

63 Spotted ray Raja montagui Fowler, 1910

64 Undulate ray Raja undulata Lacepède, 1802

65 Deepwater ray Rajella bathyphila (Holt & Byrne, 1908)



66 Bigelow's ray Rajella bigelowi (Stehmann, 1978)

67 Mid-Atlantic skate Rajella fyllae (Lütken, 1887)

68 Round skate Rajella kukujevi (Dolganov, 1985)

69 White skate Rostroraja alba (Lacepède, 1803)

ORDER MYLIOBATIFORMES

70 Dasyatidae Common Stingray Dasyatis pastinaca (Linnaeus, 1758)

71 Pelagic stingray Pteroplatytrygon violacea (Bonaparte, 1832)

72 Myliobatidae Common eagle ray Myliobatis aquila (Linnaeus, 1758)

CLASS HOLOCEPHALI

ORDER CHIMAERIFORMES

73 Chimaeridae Rabbit fish Chimaera monstrosa Linnaeus, 1758

74 Opal chimaera Chimaera opalescens Luchetti, Iglésias & Sellos, 2011

75 Small-eyed rabbitfish Hydrolagus affinis (Capello, 1868)

76 Large-eyed rabbitfish Hydrolagus mirabilis (Collett, 1904)

77 Pale chimaera Hydrolagus pallidus Hardy & Stehmann, 1990

78 Rhinochimaeridae Smallspine spookfish Harriotta haeckeli Karrer, 1972

79 Longnose chimaera Harriotta raleighana Goode & Bean, 1895

80 Straightnose rabbitfish Rhinochimaera atlantica Holt & Byrne, 1909

2.2 Prioritising elasmobranchs and holocephalans of interest 5

There have been earlier studies that had included elasmobranchs in exercises to prioritise marine

species for improved management (Hiscock et al., 2011, 2013). These exercises, however, were based

on species being listed on some form of conservation instrument and a more holistic and standardised

approach to considering all elasmobranchs had been lacking.

To prioritise the elasmobranch and holocephalan fishes of the British Isles, all species were scored

under the following four categories: conservation interest, commercial importance, importance of UK

waters to the species range and perceived biological sensitivity.

Conservation interest: This was ranked according to the regional International Union for the

Conservation of Nature (IUCN) listings (Gibson et al. 2008), and also as to whether the species was

listed for legal protection on the UK Wildlife and Countryside Act and/or listed on Appendix I or II of

5 This section is based on: Ellis, J. R. and McCully, S. R. (2013). An overview of the sharks, skates and rays (Elasmobranchii) and rabbit fish (Holocephali) of the British Isles, and prioritisation of species of interest. Working Document to the ICES Working Group on Elasmobranch Fishes, Lisbon, June 17–21 2013, 41 pp.


CITES. The scores allocated for these criteria (Table 2) could range from 0–15, as the three parameters

were summed.

Table 2. Scores applied to elasmobranch and holocephalan fishes in relation to conservation interest

IUCN Listing Score UK Wildlife and Countryside Act Score

Critically Endangered 5 Listed + 5

Endangered 4 Not listed 0

Vulnerable6 3

Data Deficient 2 CITES7 Score8

Near Threatened 1 Listed + 5

Least Concern 0 Not listed 0

Not Evaluated9 1

Commercial importance: This was scored according to (i) ICES landings data (based on data provided

for the 10 year period 2000–2009), and (ii) market value for the UK fishery in terms of the value of fish

(value per kg), as reported in 2008. Data for market value were only derived from 2008 data, as data

prior to this were not always reported to species level, and data after this year were limited for those

species with restricted fishing opportunities (e.g. species allocated a zero Total Allowable Catch (TAC)

or listed as ‘prohibited species’ status on TAC and quota regulations). The scores allocated for these

two criteria (Table 3) ranged from 1–5 (magnitude of landings) and 1–3 (value of fish), with the two

scores multiplied to give totals of 1–15.

Table 3. Scores applied to elasmobranch and holocephalan fishes in relation to commercial importance

Commercial (FAO)

Landings (t) Score Value to UK £ per kg Score

> 1500 5 High > 1.0 3

> 500 4 Medium 0.5 – 0.99 2

> 100 3 Low < 0.5 1

> 15 2

< 15 1

6 Where the term ‘Vulnerable’ is capitalised, it refers to IUCN listing criteria. The term ‘vulnerable’ (lower case) is used in the context of vulnerability studies (see Section 2.3) 7 Since this work was undertaken, porbeagle Lamna nasus was listed on Appendix II of CITES 8 Given that very few elasmobranchs from the British Isles are listed on CITES, no differentiation between Appendices I and II were made. If the current method were to be applied to other taxa, then there should be consideration of a higher score for species on Appendix I. 9 Given that the IUCN Shark Specialist Group has attempted to review all elasmobranch fish through various regional and taxonomic workshops, there were few ‘NE’ species. If the current method were to be applied to other taxa, then there should be consideration of increasing the score for ‘NE’ species


Biological sensitivity: This was scored by maximum body length (scored from 1–5) and reproductive

mode (scored as 1–3), as outlined in Table 4. Values were multiplied to create the overall score of

biological sensitivity ranging from 1 (e.g. blue pygmy skate) to 15 (e.g. porbeagle).

Table 4. Scores applied to elasmobranch and holocephalan fishes in relation to biological sensitivity

Maximum length (cm) Score Reproductive mode Score

200+ 5 Viviparous (Fecundity <10) 3

150 – 199 4 Viviparous (fecundity >10) 2

100 – 149 3 Oviparous 1

50 – 99 2

<50 1

Importance of UK waters to the stock range: This was scored according to the importance of the

eastern North Atlantic to the species and by their occurrence in waters around the British Isles (Table

5). For the former, species were identified as (a) cosmopolitan (i.e. occurring in the Atlantic and the

Indian and/or Pacific basins); (b) occurring in the wider Atlantic (i.e. they also occurred in the western

North Atlantic and/or South Atlantic) and (c) occurring in the eastern North Atlantic (which could

include the Mediterranean and parts of north-western Africa).

Species were subsequently scored as either (a) absent from the British Isles (i.e. those species which

occur in waters adjacent to the British Isles, but have not been reported from the area), (b) occasional

vagrants have been reported, (c) regular visitor, (d) present around the British Isles, but this area was

only the fringe of the distribution, (e) present and widely distributed around the British Isles and (f)

present and (probably) breeds in British waters (the term ‘breeding’ used to highlight whether the

species had mating, egg-laying/parturition or nursery grounds in the area), or with discrete stocks in

the area. Values of these two parameters were multiplied to give scores between 0 and 15.

Table 5. Scores applied to elasmobranch and holocephalan fishes in relation to the importance of UK waters to the species range

Global distribution Score UK Distribution Score

NE Atlantic only 3 British waters has ecologically important breeding sites and/or

discrete stocks 5

Wider Atlantic 2 Present around the British Isles 4

Cosmopolitan 1 Present in British seas, but only the fringe of the distribution 3

Regular visitor to British seas 2

Occasional vagrants reported 1

Absent, no authenticated records in British seas 0


Overall ranking process: Conservation importance (0–15), biological sensitivity (1–15) and

commercial importance (1–15) were summed, and this was then multiplied by the importance of this

species to the UK (0–15). This approach prevented those species that have not been officially reported

from around the British Isles from attaining a high score. This approach gave final scores (out of a

maximum of 675) to allow species to be prioritised impartially.

The current status of management advice, in relation to advice given by either ICES or ICCAT, was also

listed. Although this was not scored or used in the prioritisation process, it was included in the

prioritisation table (see Ellis and McCully, 2013) to identify those species for which the ability to

provide advice has been hampered by a lack of data. Where advice is not provided, this is a good

indication of data deficiencies, a lack of presence in trawl surveys, limited catch/landings records, or

that this stock is rare in wider European waters. Each species was listed as having (i) advice based on

a quantitative stock assessment, (ii) advice based on survey trends (usually fishery-independent trawl

surveys), (iii) qualitative assessment only, given limited signal from survey trends or other data

sources; or (iv) no assessment has been possible.

Prioritised list of chondrichthyans occurring around the British Isles: The results of the prioritisation

process identified 15 species that scored > 120 (Table 6) and these species were considered further in

terms of data availability and data gaps. Of these 15 species, the main group were the skates (Dipturus

cf. intermedia, Dipturus batis, Leucoraja naevus, Raja montagui, Raja brachyura, Leucoraja circularis,

Raja clavata, Leucoraja fullonica, Raja undulata and Rostroraja alba), with the highest ranking sharks

and dogfish including Squatina squatina, Mustelus asterias, Lamna nasus, Squalus acanthias and

Cetorhinus maximus. Of these species, data were collected for three species (Dipturus batis, Lamna

nasus and Squalus acanthias) under the south-west pilot programme. Another high ranking species

was M. asterias (ranked fifth in Table 6). This species was also selected for further study, as existing

trawl surveys generally only catch smaller individuals and the biology of this species is little known,

despite it being subject to increasing exploitation.

The prioritisation approach described here included all chondrichthyan fish from around the British

Isles. The inclusion of all species invariably necessitates a more qualitative approach, as some species

are data-limited. However, more quantitative approaches can be developed for better defined

assemblages and fisheries, as highlighted in Section 2.3.


Table 6. Highest scoring elasmobranch fishes

Rank Scientific name

Sam

ple

d in

exi

stin

g

traw

l su

rve

ys

ICES

/ IC

CA

T ad

vice

Co

nse

rvat

ion

imp

ort

ance

(0–1

5)

Bio

logi

cal s

en

siti

vity

(1–1

5)

Co

mm

erc

ial i

mp

ort

ance

(0–1

5)

Imp

ort

ance

of

UK

(0–1

5)

Fin

al s

core

(0

–67

5)

1 Dipturus cf. intermedia Survey data

limited

QA 5 5 12 15 330

2 Dipturus batis Survey data

limited

QA 5 4 12 15 315

3 Squatina squatina Isolated records (QA) 10 15 1 12 312

4 Leucoraja naevus Data for advice ST 0 2 15 15 255

5 Mustelus asterias Data for advice ST 0 6 10 15 240

6 Raja montagui Data for advice ST 0 2 12 15 210

7 Raja brachyura Survey data

limited

QA 1 3 9 15 195

8 Leucoraja circularis Survey data

limited

QA 3 3 9 12 180

9 Lamna nasus Isolated records SA 5 15 15 5 175

10 Raja clavata Data for advice ST 1 3 12 10 160

11 Leucoraja fullonica Survey data

limited

QA 1 3 6 15 150

12 Raja undulata Survey data

limited

QA 4 3 3 15 150

13 Rostroraja alba No (QA) 10 5 3 8 144

14 Squalus acanthias Data for advice SA 5 6 15 5 130

15 Cetorhinus maximus No QA 14 15 3 4 128

2.3 Productivity Susceptibility Analyses 10

Following the United Nations Code of Conduct for Responsible Fisheries (FAO, 1995), the “best

scientific evidence available” should be used when evaluating the state of a fishery and to inform

management decisions. In order to support this, various risk-based approaches, including Ecological

Risk Assessments (ERAs) and Productivity Susceptibility Analyses (PSAs), have been developed for

data-limited, multi-species scenarios. These approaches gauge the ‘vulnerability’ of a species (or

stock) to over-exploitation based on its biological sensitivity (or ‘productivity’), and its ‘susceptibility’

10 This section is based on: McCully Phillips, S. R., Scott, F. and Ellis, J. R. (2015). Having confidence in Productivity Susceptibility Analyses: A method for underpinning scientific advice on skate stocks? Fisheries Research, 171, 87–100.


to the fisheries being considered (Stobutzki et al., 2002; Fletcher, 2005; Griffiths et al., 2006; Hobday

et al., 2011).

Semi-quantitative PSAs have been considered for elasmobranch species elsewhere in the world

(reviewed by Gallagher et al., 2012), including elasmobranchs taken in pelagic (Simpfendorfer et al.,

2008; Cortés et al., 2010; Arrizabalaga et al., 2011) and deepwater fisheries (Watling et al., 2011;

Dransfeld et al., 2013).

To evaluate the elasmobranch fauna that may be encountered in Celtic Sea fisheries, an existing PSA

framework was updated, using a semi-quantitative approach, based upon their characteristics of

biological productivity and their susceptibility to fisheries. The NOAA toolbox11 PSA framework (Patrick

et al., 2009) was used, albeit with some modifications to address better the biological characteristics

of elasmobranchs. Twelve ‘productivity’ attributes were included in the PSA (Table 7) of which two

(measured fecundity and breeding strategy) were modified from the default NOAA toolbox, and an

additional two attributes (breeding cycle and genetic distinctness) also included. Thirteen

‘susceptibility’ attributes were included (Table 8), of which three (fishery importance, management

applicable and monitoring (or assessment) of status) were added attributes (replacing the single

‘management strategy’ attribute in the NOAA toolbox), as these attributes were all considered

discrete issues. One attribute (‘fishing rate relative to M’) was excluded, as this is unknown for the

species in this case study, and another attribute (value of fishery) removed exact monetary definitions

and made the scoring more qualitative in terms of desirability.

Score for each ‘productivity’ and ‘susceptibility’ attribute were between 0–3 (with bridging values of

1.5 and 2.5 permitted). Attributes were also ‘weighted’ (i.e. how much consideration was given to this

attribute in the assessment). Following Patrick et al. (2009), the default score was two (where each

attribute would be given equal importance), with a range of zero (i.e. excluded from the assessment)

to four (of greatest importance). The weights assigned to each attribute remained constant across all

species in the assessment, and for each fishery assessed. The attribute score multiplied by the weight

gives the ‘weighted attribute score’.

The attributes for ‘productivity’ were scored based on published information, and these scores were

also reviewed by an international colleague with considerable experience in elasmobranch biology.

Four national experts from three European countries scored the ‘susceptibility’ attributes for the case-

11 Available at http://nft.nefsc.noaa.gov/index.html

http://nft.nefsc.noaa.gov/index.html


study species in two broad types of fishery (demersal otter trawl and gillnet fleets) operating in the

Celtic Sea. They also provided a ‘data quality’ score to assign weightings (between zero and four, the

higher the score, the more ‘weight’ that attribute carries within the assessment) that they believed

appropriate to each attribute. Weightings were assigned to attributes using the modal values attained,

and did not change between species within a gear, or between the two gears themselves. In addition

to ‘data quality’, a ‘confidence score’ (low, medium, high, very high scored as 0.2, 0.5, 0.8 and 0.9,

respectively) was also given to each attribute by each assessor to represent their degree of confidence

of being correct. More detailed analyses of these are given in McCully Phillips et al. (2015).

The data quality score for biological productivity ranged from low (nine species, including angel shark)

to high (one species, spurdog), with 11 species deemed of ‘medium’ data quality. For the

‘susceptibility’, all species in both fisheries achieved a data quality score of ‘medium’.

The relative vulnerabilities (final PSA score) of all species were ranked from high to low for both gillnet

(Table 9, Figure 3) and otter trawl fisheries (Table 9, Figure 4). In the gillnet fishery, the most vulnerable

species were tope Galeorhinus galeus (score of 2.00) followed by five other species that are either

currently designated as prohibited species or have a zero TAC in the Celtic Seas ecoregion. Of the

species that are not subject to restrictive management, the most vulnerable members of the

commercially exploited ‘skate and ray’ assemblage were blonde ray Raja brachyura, long-nose skate

Dipturus oxyrinchus and shagreen ray Leucoraja fullonica. The former species is a commercially

important species for which ICES has been unable to ascertain the stock status, and the latter two

species are deeper water skates that are infrequent on the continental shelf. Results for the otter

trawl fishery were broadly similar, with angel shark Squatina squatina (which is now a protected

species) ranking as the most vulnerable species (1.98), followed by tope and then three prohibited or

zero TAC species (spurdog, white skate Rostroraja alba and flapper skate Dipturus cf. intermedia).

This PSA was conducted primarily to assess the relative vulnerabilities of the various skates caught in

mixed fisheries that are currently managed under the generic ‘skate and ray’ TAC, whilst the inclusion

of other elasmobranchs allowed comparisons to be drawn for six different families of elasmobranch,

thereby allowing slightly different life histories to be included. Earlier studies (McCully et al., 2012b)

investigated whether ‘data rich’ teleosts with quantitative stock assessments could be used to

‘ground-truth’ the elasmobranch results, but the results were inconclusive, as elasmobranchs

generally clustered together on the PSA plot as a result of their life history being so different to most

teleosts. The results presented here allowed the elasmobranchs to be better differentiated.


Whilst this type of assessment allows the highest priority species within the elasmobranch assemblage

to be identified, it is important to consider how such assessments can inform management advice. In

this case, given that the top ranking 5–6 species are already subject to some form of restrictive

management (e.g. through a zero TAC or prohibited listing), the focus for future assessments and

management could usefully be directed towards the next most vulnerable elasmobranchs for which

stock status is uncertain. This would include various members of the commercial skate complex such

as blonde ray and shagreen ray.

The approach clearly highlights where knowledge gathering and management action could be

prioritised, it is more difficult to see how PSAs could inform on quota management and estimating

maximum sustainable yield (MSY). However, elsewhere in the world, information from PSA

approaches has helped to identify ‘acceptable biological catches’ (ABC) for data-limited species

(Berkson et al., 2011; Carmichael and Fenske, 2011). Such PSA approaches may also be useful in the

initial evaluation of potential management options, especially when more quantitative susceptibility

attributes can be defined for more discrete fisheries. Within the framework of regional management,

fishers from relevant sectors of the fleet could be involved in identifying pragmatic and effective

management options through iterative applications of PSA tools.


Table 7: Productivity attributes used in the PSA. Those in normal font were as used in the NOAA PSA framework, parameters modified from NOAA are shown in bold, and additional parameters shown in bold italics.

Productivity Attributes Low (1) Moderate (2) High (3)

Intrinsic rate of population

growth (R) <0.16 0.5–0.16 (mid-point 0.10) >0.5

Maximum Age > 30 years 10–30 years (mid-point 20) <10 Years

Maximum Size >150 cm 60–150 cm (mid-point 105) < 60 cm

von Bertalanffy Growth

Coefficient (k) < 0.15 0.15–0.25 (mid-point 0.20) > 0.25

Estimated Natural Mortality < 0.20 0.20–0.40 (mid-point 0.30) > 0.40

Measured Fecundity < 10 10–100 > 100

Breeding strategy Live bearer Demersal egg layer Broadcast spawner

Breeding cycle (female) Bi / Triennial Annual cycle with a

seasonal peak

Annual cycle with

protracted breeding

season or with multiple

broods per year

Recruitment Pattern

infrequent recruitment

success (< 10% of year

classes are successful)

moderately frequent

recruitment success

(between 10% and 75% of

year classes are successful)

highly frequent

recruitment success (> 75%

of year classes are

successful)

Age at Maturity > 4 years 2–4 years (mid-point 3.0) < 2 years

Mean Trophic Level >3.5 2.5–3.5 (mid-point 3) <2.5

Genetic distinctness

In this region, this

species is the only one in

its family

In this region, this species is

the only one in its genus

In this region, this species

is one of several in its

genus


Table 8: Susceptibility attributes used in this study. Those in normal font are taken from the NOAA PSA framework, those in bold are modified parameters, and added parameters are denoted by bold italics.

Susceptibility Attributes Low (1) Moderate (2) High (3)

Fishery Non-commercial species in this fishery

Important bycatch in mixed fisheries and/or targeted in seasonal/localised fisheries

Important target fisheries operate or have operated in recent times (for this metier)

Management applicable

Landings or catches strictly regulated for much of the stock area

Landings or catches partly regulated for the stock area

No management measures for the species/species-complex

Monitoring (or assessment) of stocks

Appropriate monitoring to inform on stock status

Limited data can inform on trends in catches or landings

Insufficient data to evaluate status

Areal Overlap < 25% of stock occurs in the area fished

Between 25% and 50% of the stock occurs in the area fished

> 50% of stock occurs in the area fished

Geographic Distribution

Continuous: stock is distributed in > 50% of the range of the fishery

Restricted: stock is distributed in 25% to 50% of the range of the fishery

Fragmented: stock is distributed in < 25% of the range of the fishery

Vertical Overlap < 25% of stock occurs in the depths fished

Between 25% and 50% of the stock occurs in the depths fished

> 50% of stock occurs in the depths fished

Biomass of Spawners (SSB) or other proxies

B is > 40% of B0 (or maximum observed from time series of biomass estimates)

B is between 25% and 40% of B0 (or maximum observed from time series of biomass estimates)

B is < 25% of B0 (or maximum observed from time series of biomass estimates)

Seasonal Migrations Seasonal migrations decrease overlap with the fishery

Seasonal migrations do not substantially affect the overlap with the fishery

Seasonal migrations increase overlap with the fishery

Schooling/Aggregation and Other Behavioural Responses

Behavioural responses decrease the catchability of the gear

Behavioural responses do not substantially affect the catchability of the gear

Behavioural responses increase the catchability of the gear [i.e., hyperstability of CPUE with schooling behaviour]

Morphology Affecting Capture

Species shows low selectivity to the fishing gear.

Species shows moderate selectivity to the fishing gear.

Species shows high selectivity to the fishing gear.

Survival After Capture and Release

Probability of survival > 67%

33% < probability of survival < 67%

Probability of survival < 33%

Desirability/Value of the Fishery

stock is not highly valued or desired by the fishery

stock is moderately valued or desired by the fishery

stock is highly valued or desired by the fishery

Fishery Impact to EFH or Habitat in General for Non-targets

Adverse effects absent, minimal or temporary

Adverse effects more than minimal or temporary but are mitigated

Adverse effects more than minimal or temporary and are not mitigated


Table 9: Results of the PSA vulnerabilities and overall rankings for elasmobranchs that may be encountered in otter trawl and gillnet fisheries in the Celtic Sea. Productivity is species-specific and does not change between fisheries, whilst susceptibility scores are fishery-specific).

Species FAO Code

Productivity

Otter Trawl Gillnet Otter Trawl Gillnet

Susceptibility Susceptibility Vulnerability Vulnerability

We

igh

ted

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Sco

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ttri

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core

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a

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Score Rank Score Rank

Tope GAG 1.33 2.88 2.07 2.85 2.11 2.80 1.98 2 2.00 1

Angel shark AGN 1.29 3.82 2.00 3.22 1.97 3.07 1.98 1 1.97 2

Spurdog DGS 1.39 1.97 2.06 2.00 2.12 1.94 1.93 3 1.96 3

White skate RJA 1.52 3.55 2.10 3.37 2.16 3.48 1.85 4 1.88 4

Flapper skate RJB1 1.50 2.79 2.06 2.98 2.12 2.98 1.83 5 1.87 5

Electric ray TTO 1.48 4.06 1.93 3.00 1.95 3.06 1.78 6 1.79 7

Common skate RJB2 1.65 2.94 2.13 2.77 2.18 2.72 1.76 7 1.79 6

Blonde ray RJH 1.76 3.03 2.22 2.61 2.24 2.63 1.74 8 1.75 8

Long-nosed skate RJO 1.71 4.00 2.16 3.32 2.14 3.31 1.73 9 1.72 10

Norwegian skate JAD 1.65 3.88 2.04 3.35 2.10 3.36 1.70 10 1.74 9

Starry smooth-hound SDS 1.70 2.91 2.10 2.42 2.12 2.45 1.70 11 1.72 11

Shagreen ray RJF 1.77 3.76 2.14 2.91 2.19 2.86 1.67 12 1.71 12

Sandy ray RJI 1.77 3.76 2.12 3.42 2.14 3.47 1.66 13 1.68 13

Small-eyed ray RJE 1.80 3.03 2.10 2.56 2.12 2.60 1.63 14 1.64 15

Marbled electric ray TTR 1.67 3.82 1.93 3.02 1.95 3.09 1.63 15 1.64 16

Undulate ray RJU 1.86 2.88 2.12 2.84 2.19 2.78 1.60 17 1.65 14

Thornback ray RJC 1.89 2.24 2.18 2.44 2.11 2.44 1.61 16 1.56 17

Spotted ray RJM 1.98 2.55 2.10 2.55 2.10 2.56 1.50 18 1.50 18

Cuckoo ray RJN 1.98 2.42 2.06 2.46 2.07 2.51 1.46 19 1.48 19

Greater-spotted dogfish SYT 1.98 3.88 1.92 2.80 1.90 2.79 1.37 20 1.35 20

Lesser-spotted dogfish SYC 2.09 2.67 1.91 2.03 1.82 2.02 1.29 21 1.22 21


Figure 3: PSA plot indicating vulnerabilities of Celtic Sea elasmobranchs in the demersal gillnet fishery. Species codes given in Table 9.

Figure 4: PSA plot indicating vulnerabilities of Celtic Sea elasmobranchs in the demersal otter trawl fishery. Species codes given in Table 9.

RJB1

RJB2RJU

RJNRJC

RJM RJE

RJH

RJI

RJFRJO

JAD

RJA

SYC

SYT

SDS

GAGDGS

AGN

TTR TTO

1.0

1.5

2.0

2.5

3.0

11.522.53

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Productivity

Data Quality HighData Quality MediumData Quality Low

RJB1

RJB2

RJU

RJN

RJC

RJM

RJE

RJH

RJI

RJFRJO

JAD

RJA

SYC SYT

SDS GAG

DGS

AGN

TTR TTO

1.0

1.5

2.0

2.5

3.0

11.522.53

Susc

ep

tib

ility

Productivity

Data Quality HighData Quality MediumData Quality Low


3 Elasmobranch bycatch in the Celtic Sea

Summary

A pilot project was undertaken in conjunction with selected netters operating in the south-west

in order to collect data on spurdog, common skate and porbeagle. These three species are locally

and/or seasonally common in the area and the current regulations that prevent landing these

species, especially when brought on board dead, has been controversial with the fishing industry.

Spurdog could be taken in high numbers as a bycatch species and, in the most extreme cases, the

estimated biomass of spurdog caught could exceed the retained biomass of the main target

species. Catches were highly variable, which may be related to the aggregating nature of the

species and as to whether fishing operations coincided with the locations of any aggregation.

Porbeagle bycatch was much more seasonal and this species was caught mostly from August to

December, with the largest catches reported from August to October.

Catches of the common skate complex was comprised mostly of the smaller of the two species

(Dipturus batis), and this species could be taken in high numbers in tangle net fisheries.

At-vessel mortality of porbeagle in set nets ranged from 56–97% in two of the vessels studied,

with the former based on a small sample size. Across all trips, at-vessel mortality was >90%.

At-vessel mortality of common skate in tangle nets averaged 33.6% across the sets examined.

Aggregated across all trips, at-vessel mortality was 38.5%. This confirms that the survival of skates

in offshore net fisheries is lower than observed in inshore tangle and gillnet fisheries, presumably

related to the higher soak times on offshore fishing grounds.


3.1 Introduction

The reformed Common Fisheries Policy (CFP) aims to have a more ecosystem approach to fisheries

management and to conserve threatened species, whilst also minimising waste, especially in terms of

reducing ‘dead discards’ (CEC, 2013). These sentiments can, however, be difficult to balance when a

species that is perceived as threatened can be taken as bycatch and a proportion of the bycatch is

dead. The restrictive management of certain elasmobranchs, notably spurdog, porbeagle and

common skate, has been a controversial issue, especially for those fleets that operate where these

species are locally and/or seasonally abundant, and/or are taken as an incidental (and sometimes

dead) bycatch.

A pilot project was conducted to understand better the extent to which these three species are taken

as incidental bycatch in the offshore gillnet fishery in the Celtic Sea. This work was developed through

a “Shark, Skate and Ray Scientific Bycatch Fishery”, with the aim to:

Collect fishery-dependent data on the seasonal and spatial variability in spurdog, common

skate and porbeagle bycatch in Celtic Sea fisheries (ICES Divisions VIIe–j),

Collate further data and anecdotal information on discard survival,

Retain a proportion of the dead bycatch for subsequent biological examination

Develop a ‘Code of Conduct’ that could help reduce fishing mortality.

3.2 Stakeholder engagement

Engaging with commercial fishers in collaborative research can help develop stronger links between

the fishing industry and the science that underpins management and policy decisions. In October

2012, one year before the start of the NEPTUNE project, a meeting on shark, skate and ray bycatch

and discard issues was held with stakeholders in the south-west of the UK. Some of the commercial

fishers considered that the science, fisheries policy and restrictive management measures for

porbeagle, spurdog and common skate were not in line with what they encountered at sea. They

perceived that these species were locally and/or seasonally abundant, and more so than inferred from

scientific studies. It was agreed at this meeting that fisher’s knowledge and information could help

improve the evidence used in the assessment and management process. An action of this meeting

was for Defra and Cefas to develop an industry-led scientific sampling programme for porbeagle,

common skate and spurdog. Given that fishery-independent data for these species are, to varying

degrees, limited, it was considered that fishery-dependent sources could provide important

information to better understand these stocks (see Section 3.3).


Cefas organised two further stakeholder meetings in Newlyn, Cornwall (November 2013 and February

2015), with both meetings attended by 30 or more participants, including commercial fishers, as well

as representatives from the Cornish Fish Producers Organisation (CFPO), Cefas, Defra, Marine

Management Organisation (MMO), Natural Resource Wales (NRW), Cornwall Inshore Fisheries and

Conservation Authority (CIFCA) and the Shark Trust. These meetings gave the fishing industry an

opportunity to discuss issues relating to elasmobranchs with both scientists and policy staff, and gave

a forum for the exchange of knowledge and views from the attending parties.

3.3 Approach and data collection

Following an open tender process, which was held in the spring of 2013, suitable commercial fishing

vessels that would provide appropriate coverage and sampling of the case study species were

identified. These vessels would be expected to encounter the case study species as incidental and

unavoidable bycatch during the course of their normal fishing practices. Following a tender evaluation

process (July 2013), six vessels were selected to participate in the “Shark, Skate and Ray Scientific

Bycatch Fishery”. Cefas staff visited Newlyn and Plymouth to meet with the owners and skippers of

these fishing vessels in September 2013 and, following this, detailed survey plans were drawn up for

the first three vessels (netters) and agreed with the skippers, including protocols for data collection

and tagging. Dispensations for these vessels to land dead bycatch of two species (spurdog and

porbeagle, both of which were zero TAC species) were granted by the MMO, and permissions to retain

and land both species were sought via the Foreign and Commonwealth Office (FCO), as participating

vessels may not have always exclusively operated in or transited through UK waters. Whilst it was

originally hoped to include further vessels representative of other métiers (e.g. beam and otter trawl),

it was decided during the course of the project that it would be preferable to focus efforts on netters,

and that single vessels from other métiers may not be representative.

During this pilot project, three commercial fishing vessels were used12. The first trip was undertaken

on Vessel A (8–13 October 2013), with two Cefas scientists training the crew in self-sampling

techniques. This was followed by trips on Vessel B (November 2013) and Vessel C (December 2013),

each with a Cefas scientist aboard to help train the crew. The crews were trained in elasmobranch

species identification, sexing, measurement, sub-sampling and recording (Figure 5). For those

elasmobranchs alive and in a fit condition for live release, the crews were trained to tag and release

with mark-ID tags.

12 Participating vessels are named here as Vessels A, B and C


These vessels subsequently collected data, usually for at least one trip each month. In addition to the

initial training period, there was observer coverage on one additional trip on both Vessel A and Vessel

C, during which the crew recorded independently from the scientists for comparative data quality

purposes. Summary details of the three vessels are provided in Table 10, and details of those trips

undertaken and for which data were provided are summarised in Table 11.

Figure 5: Disentangling a common skate from fishing gear

The data provided included the broader location of the grounds fished each trip (but not usually the

exact positions for each gear deployment), dates fished, gear used and number of sets. Catch data

provided by the vessels included the approximate weights of commercial catch (typically in terms of

the numbers of fish boxes raised by the approximate weight per box) and also the quantity (numbers

or estimated biomass) of the case study species. These data were supplied by ICES Statistical

Rectangle. Whilst information on the lengths of nets used and approximate soak times were provided

on some occasions, which could then be used to estimate the catch per unit effort, these data were

not available for all sets. For the purposes of this report, catches of case study species are expressed

as a number or biomass per quantity of target species retained.

For the case study species, selected specimens that were alive were tagged with rototags, with

information on sex, length and ‘health state’ (lively or sluggish) and tag number recorded before

release back to the sea. Sub-samples of dead porbeagle and spurdog bycatch were retained for

subsequent biological examination ashore.


Table 10. Details of the three vessels participating in the “Shark, Skate and Ray Scientific bycatch fishery”.

Vessel Main fishing practices

A

This offshore netter (22.65 m LOA), based at Newlyn, fished mainly on open grounds

using a combination of gillnets and tangle nets. Gillnets were of 120–150 mm mesh size

and deployed in ranging from 7.5–10.5 nm (ca. 14–20 km). Soak times typically ranged

from 16–34 h, although longer soak times were reported very occasionally. The main

species taken in gillnets were hake and pollack, as well as other gadoids (ling, haddock,

saithe and cod). Spurdog was a frequent bycatch species, and porbeagle was a seasonal

bycatch in late summer and early autumn.

Tangle nets were of 250–300 mm mesh size and deployed in ranging from 12–27 nm

(ca. 22–50 km). Soak times ranged from 24–120 hours, but most sets were from 72–96

h. The main commercial species taken in tangle nets were anglerfish and turbot, with

skates and rays (including common skate) a frequent bycatch. Spurdog and porbeagle

were also an occasional bycatch in tangle nets

B

This gillnetter (20.43 m LOA), based at Newlyn, fished mainly on open grounds for

pollack, saithe and cod, with spurdog a frequent bycatch species. The mesh size used

was 135–140 mm, with fleets of gillnet set at lengths of 600–3,300 yards (ca. 550–3,000

m), with soak times ranging from 6–16 h.

C

This netter (20.6 m LOA), based at Newlyn, fished mainly near wrecks with gillnets,

targeting pollack, saithe, cod, ling, hake and anglerfish with gillnets, and also fished for

turbot, hake and anglerfish with tangle nets. Gillnets (mesh size = 155 mm) were 3,420

m long and set for soak times of approximately 12 h. Tangle nets (271 mm mesh) were

set in fleets ranging from 3,200–25,600 m, with a 48–120 h soak time.


Table 11. Summary details of commercial trips for which data were collated. Note: trips marked [1] and [2] only provided information for porbeagle and common skate, respectively.

Vessel Year Trip no. Dates of fishing Stations fished with

Notes Gillnet Tangle

Vessel A 2013 1 10–13 Oct 8 5

2 14–15 Oct 3 3

3 10–13 Nov 13

4 23–24 Nov 8

5 26–30 Nov 17 5

6 03–07 Dec 14 6

7 11–14 Dec 11 8

2014 1 09–11 Jan 18

2 19 Jan 3

3 8–14 Mar 4 11

4 17–18 Mar 7 3

5 24–29 Mar 12 1

6 06–13 Apr 15 15

7 19–22 Apr 12 8

8 25–28 Apr 3 3

9 4–10 May 25 15

10–12 2–4 Aug, 6–8 and 17–19 Aug [1]

13 26 Sep–4 Oct 20 8

14–15 Oct–Dec [2]

Vessel B 2013 1 11–13 Nov 6

2 24–28 Nov 5

3 11–13 Dec 3

2014 1 9 Jan 1

2 10–11 Feb 2

3 20–24 Feb 5

4 8–11 Mar 3

Vessel C 2013 1 09–13 Dec 7

2014 1 10–12 Jan 6

2 20–22 Jan 3

3 23–27 Jan 5

4 17–22 Feb 6

5 23–26 Feb 4

6 07–10 Mar 5

7 04–09 Jun 6

8 21–26 Jun 6

9 5–9 Jul 5

10 29–31 Oct 5

11 13–17 Nov 8

12 31 Nov –3 Dec 4

13 15–16 Dec 3


3.4 Catches of spurdog, common skate and porbeagle

3.4.1 Vessel A

Vessel A operated with the most gear, using both tangle nets and gillnets on most trips. Gillnet catches

were dominated by various gadiform fish, notably hake and pollack, with ling, haddock, saithe and cod

also taken. The main fishing grounds for their gillnet operations were 160 km west of the Scilly Isles

(ICES Rectangle 29E1; Figure 6), with adjacent grounds (mainly 29E2) fished with tangle nets (Figure

7). Some tangle net fishing was also undertaken in the western English Channel (27E6), where catches

mostly comprised various skates, anglerfish and brill.

Spurdog was a frequent bycatch species that was taken in all months for which data were available

(14 trips from October to May; Table 12). It could also be an abundant bycatch species. For example,

the estimated biomass of spurdog taken in one trip during October was higher than the retained

quantity of the main target species (hake and pollack). Spurdog was also taken in large quantities in

four other trips, with catches equating to ca. 300–580 kg of spurdog per tonne of hake and pollack.

Smaller catches (<30 kg of spurdog per tonne of hake and pollack) were reported on six of the trips.

There was no apparent seasonal pattern in these ratios for the period examined, and catches of

spurdog could be high or low in any given month.

Although porbeagle (n = 83) could be reported in low numbers (1–2 fish per trip) over much of the

year, there was a clear seasonal peak. Most records were between August and November, with the

largest catches made during trips undertaken in August and September (34 and 39 in two of the trips

undertaken), confirming the seasonality of this species (Table 12).

Tangle net catches were composed primarily of anglerfish and turbot, with common skate-complex

(primarily Dipturus batis with some D. cf. intermedia) an important bycatch (

Table 13). As with spurdog, the estimated biomass of common skate caught could occasionally exceed

the weight of the retained catch of the main target species (anglerfish and turbot). For the majority of

trips, however, catches of common skate were estimated to be in the range of 340–880 kg per tonne

of anglerfish and turbot. Spurdog were also caught in tangle nets, albeit in lower quantities than

gillnet, and occasionally porbeagle (n = 10).


Figure 6. Main fishing grounds of Vessel A when setting gillnets.

Table 12. Reported catches by Vessel A of spurdog (estimated biomass) and porbeagle (number) caught in gillnets per trip and in relation to the reported retained catch of the main species (hake and pollack, ‘na = data not available). Data aggregated at a trip level. For those sets where spurdog were counted, the biomass was estimated based on an average weight of 3.5 kg per fish.

Year Trip Month Hake Pollack Spurdog Porbeagle

Kg Kg Kg Kg/t No. No/t

2013 1 Oct 8976 214.5 23.9 2 0.22

2 Oct 1056 429 1914 1288.9 1 0.67

3 Nov 11121 99 8.9 2 0.18

4 Nov 11022 3348 303.8 – –

5 Nov 6072 1848 396 50.0 – –

6 Dec 3201 198 1980 582.5 – –

7 Dec 165 1782 709.5 364.4 – –

2014 1 Jan 1188 4917 102.5 16.8 – –

4 Mar 858 1023 157.5 83.7 – –

5 Mar 6369 363 17.5 2.6 – –

6 Apr 1505 2730 0.0 – –

7 Apr 2240 805 1235 405.6 – –

8 Apr 3366 429 231 60.9 – –

9 May 2640 1287 33 8.4 2 0.51

10 Aug na Na 33 – 2

11 Aug na Na na – 1

12 Aug na Na na – 34

13 Sep/Oct na Na 33 – 39


Figure 7. Main fishing grounds of Vessel A when setting tangle nets.

Table 13. Reported catches by Vessel A of Dipturus spp. (estimated biomass for all species in the genus) caught in tangle nets per trip and in relation to the reported retained catch of the main species (anglerfish and turbot). Data aggregated at a trip level. For those sets where common skate were counted, the biomass was estimated based on an average weight of 10 kg per fish.

Year Trip Month Anglerfish Turbot Dipturus spp.

Kg Kg Kg Kg/t target species

2013 1 Oct na na 2602.5 na

2 Oct na na 790 na

5 Nov 1089 37.5 858 761.7

6 Dec 726 25 535 712.4

7 Dec 1023 50 363 338.3

2014 2 Jan 66 25 80 879.1

3 Mar 4320 100 23.1

4 Mar 240 25 270 1018.9

5 Mar – 25 66 2640.013

6 Apr 1085 625 – –

7 Apr 240 125 806 2208.2

8 Apr 840 400 470 379.0

9 May – 2050 – –

13 Sep/Oct na na 620 na

13 Catch data for this gear limited on this trip and so the ratio is not representative


3.4.2 Vessel B

Vessel B targeted pollack and saithe primarily, with spurdog the most frequent case study species

taken as bycatch. This vessel operated over a variety of grounds, in the Celtic Sea, with the largest

catches made in ICES Rectangle 29E0 (Figure 8). Few common skate were reported, and only a single

porbeagle. Spurdog catches were generally reported as the numbers of fish, but in those sets where

they were caught in greater numbers they were quantified in terms of numbers of fish boxes. Spurdog

was encountered mostly in low numbers (<15 fish per set, typically at a rate of 3.6 spurdog per tonne

of Pollachius spp.), but there were some instances where up to three fish boxes (estimated at 40 kg

per box) of spurdog could be caught, equating to ca. 23–53 kg of spurdog per tonne of Pollachius spp.

(Table 14). This vessel left the fishing industry during the course of the project, and data were only

available from November 2013 to March 2014.

Figure 8. Main fishing grounds of Vessel B when setting gillnets.


Table 14. Reported quantities of spurdog caught by Vessel B in relation to the main target species (pollack and saithe) between November 2013 and March 2014. Data shown by set, as spurdog were either enumerated, or the catch was estimated based on the number of fish boxes.

Year Trip Set Pollack Saithe Spurdog Spurdog

Kg Kg Kg No. kg/t target

species No/t target

species

2013 1 (Nov) 1 1260 924 – 2 – 0.92

2 630 378 – 2 – 1.98

3 210 840 – 4 – 3.81

4 210 798 – 10 – 9.92

5 378 924 – 8 – 6.14

6 210 336 – 4 – 7.33

2 (Nov) 1 966 630 – 1 – 0.63

2 1554 588 0 0 0.00 0.00

3 1092 756 0 0 0.00 0.00

4 1302 588 0 0 0.00 0.00

5 462 504 0 0 0.00 0.00

3 (Dec) 1 714 546 40 na 31.75

2 756 756 – 12 – 7.94

3 420 546 0 0 0.00 0.00

2014 1 (Jan) 1 52.5 na

2 (Feb) 1 2100 84 80 na 36.63

2 2226 42 120 na 52.91

3 (Feb) 1 420 42 42 na 23.26

2 756 – – 9 – 11.90

3 1218 42 – 1 – 0.79

4 840 336 – 2 – 1.70

5 798 – – 6 – 7.52

4 (Mar) 1 1344 – 42 na 31.25 –

2 na na 6 – na

3 na na 1 – na

3.4.3 Vessel C

Vessel C fished mainly near wrecks for pollack, saithe, cod, ling, hake and anglerfish with gillnets (the

main gear used over the period for which data were collected), and turbot, and anglerfish were

targeted with tangle nets. This vessel operated over a broad range of grounds, in the Celtic Sea and

western Channel, with the main area fished with gillnet corresponding to ICES Rectangles 28E4 and

26E3 (Figure 9) and tangle nets used on the grounds covering 28E2, 29E2 and 28E1 (Figure 10).

Catches of spurdog were generally small (up to 24 spurdog per set) and were always enumerated (the

smaller catches of spurdog possibly related to the shorter lengths of gillnet deployed in the vicinity of


wrecks). They occurred in 29 of the 53 sets (54.7%) for which data were collected. The highest bycatch

rates in individual sets were about 21 spurdog per tonne of gadoid (for this vessel defined as the

aggregated landed weight of pollack, saithe and cod), but the average was only 3.6 spurdog per tonne

of gadoid landed. Once again, spurdog catches were quite sporadic, with high and low catches taken

in any given month (Table 15).

A total of 42 porbeagle sharks were reported, of which four were reported to have either dropped out

of the net on retrieval or to have been returned alive and five were noted as dead. The single largest

catch was of 15 porbeagle in one set (October 2014), with most porbeagle recorded in the period

October to December.

Common and flapper skates were recorded in tangle net catches (Table 16), with only a single

porbeagle recorded in this gear. This gear was used seasonally, with data available for June and July,

and Dipturus spp. were caught at rates of about 5.1–16.9 fish per tonne of anglerfish and turbot.

Figure 9. Main fishing grounds of Vessel C when setting gillnets.


Figure 10. Main fishing grounds of Vessel C when setting tangle nets.

Table 15. Summary details of the quantities of spurdog caught in relation to the main target species (pollack, cod and saithe) by Vessel C between December 2013 and March 2014, and between during October and December 2014. Catch data aggregated across trips.

Year Trip Month Cod Pollack Saithe Spurdog

Kg Kg Kg No No/t target species

2013 1 Dec 3680 2562 2256 2 0.24

2014 1 Jan 5754 240 4 0.67

2 Jan 6048 20 30 4.94

3 Jan 13052 48 50 3.82

4 Feb 4788 4 24 5.01

5 Feb 6426 20 5 0.78

6 Mar 12402 432 58 4.52

10 Oct 1912 1116 3344

11 Nov 4576 1804 2860 4 0.43

12 Dec 1870 1496 2354

13 Dec 528 704 1232 26 10.55

Table 16. Summary details of the quantities of Dipturus spp. caught in tangle nets in relation to the main target species (turbot and anglerfish) by Vessel B during three trips in 2014. Catch data aggregated across trips.

Trip Month Anglerfish Turbot Dipturus spp.

Kg Kg No No/t target

species

7 Jun 337.5 2747 52 16.9

8 Jun 200 1523 9 5.2

9 Jul 218 2132 12 5.1


3.4.4 Summary

Catches of spurdog in gillnets were a common occurrence, and this species was often taken in large

numbers. Catches also occurred over a wide area (Figure 11) and successive trips could have high and

low catches, even when a short time apart. Such a pattern is consistent with the known aggregating

behaviour of this species, highlighting the problems in identifying times and locations where any

aggregation may occur.

Although catches of porbeagle were also made over a relatively large area (Figure 12), the catches

described above showed a clear seasonality, which could be related to the migratory behaviours of

this species. Most catches occurred between August and December, and peaked in September and

October.

Catches of common skate in tangle nets were mostly reported from a more restricted number of

rectangles (Figure 13), and large catches could be reported during all the months for which data were

available, confirming the view that this species has more restricted movements.

Figure 11. Spatial distribution of spurdog bycatch observed by ICES rectangle


Figure 12. Spatial distribution of porbeagle bycatch observed by ICES rectangle

Figure 13. Spatial distribution of common skate bycatch observed by ICES rectangle


3.5 Tagging studies and biological information

Overall, 759 elasmobranchs were tagged and released (Table 17), and relevant details supplied. These

data have been archived on Cefas’ Tagged Fish Database. Whilst there have only been limited numbers

of recaptures to date, this is in part related to the current ‘prohibited status’ of one of the species

(common skate) and that the time at liberty has been limited.

Table 17. Numbers of elasmobranchs tagged and released during the pilot programme

Species No. tagged Length range (cm)

Lamna nasus 5 127–196

Squalus acanthias 279 40–122

Galeorhinus galeus 1 130–130

Dipturus batis 412 53–176

Dipturus cf. intermedia 24 88–204

Dipturus batis complex 5 48–184

Raja undulata 33 68–104

The most frequently tagged species was common skate Dipturus batis, with small numbers of flapper

skate also reported. The majority of fish were in the 110–135 cm length range (Figure 14). The largest

common skate recorded were much larger than that observed by Iglésias et al. (2010), suggesting that

some of these fish may have been misidentified flapper skate. Information on the relationship

between total length (LT) and disc width (D) was also recorded, and the linear relationship (Figure 15)

was described as D = 0.6727. LT+ 4.9083 (n = 151, r2 = 0.967). Most of the common skate complex were

reported as Dipturus batis, with smaller numbers of Dipturus cf. intermedia, which is in keeping with

earlier studies (Griffiths et al., 2010; Bendall et al., 2014).

Most of the spurdog tagged were either in the 65–90 cm length range, where males were the

predominant sex, or from 101–113 cm (Table 16). The latter cohort would be expected to comprise

mature females, although the records did include some males in this length range. These nominal

records are greater than the maximum length that would be expected for males, indicating that the

sex (or species) was not recorded correctly.

One vessel, which operated occasionally in the western English Channel, tagged and released a sample

of undulate ray (Figure 17), with most of the larger (>90 cm LT) individuals female.


As part of the “Shark, Skate and Ray Scientific Bycatch Fishery” a proportion of dead spurdog and

porbeagle bycatch was retained and landed, under dispensation, for biological study. Samples of

spurdog (1,112 specimens) were kept in frozen storage in the south-west, and transported to

Lowestoft in September 2014, where detailed biological sampling was undertaken (Section 4.3). The

sample of dead porbeagle (n = 53), which was also kept frozen, was brought to Lowestoft in January

2015 for examination (Section 4.4).

Figure 14. Length frequency of Dipturus spp. tagged and released, showing those identified as Dipturus batis (BSKT),

Dipturus cf. intermedia (FSKT) and Dipturus batis-complex (SKT)

Figure 15. Relationship between disc width and total length in Dipturus batis

0

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BSKT FSKT SKT

y = 0.6727x + 4.9083R² = 0.9668

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40 60 80 100 120 140 160

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Figure 16. Length frequency of spurdog Squalus acanthias tagged and released

Figure 17. Length frequency of undulate ray Raja undulata tagged and released

3.6 At-vessel mortality

Data on the vitality and fate of porbeagle were provided by all three vessels, but most specimens

caught by Vessel A. During the course of the project, porbeagle were recorded in four categories: (a)

tagged and released, (b) released in ‘sluggish condition’ or dropped out of the net alive, (c) dead, or

(d) fate unknown or dropped out of the net in unspecified condition. Three estimates of at-vessel

mortality were calculated, depending as to whether specimens of ‘unknown fate’ were excluded

case), assumed alive (best case scenario) or assumed dead (worst case scenario). Across all trips and

vessels, the at-vessel mortality was >90% (

0

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Table 18), unless specimens of ‘unknown fate’ were assumed alive, which would indicate at-vessel

mortality of 77.5%. One of the vessels (Vessel C) encountered only small numbers of porbeagle, and

estimates of at-vessel mortality were lower (ca. 56%) for this vessel than with Vessel A (> 97%).

Data on the vitality and fate of common skate complex were provided by one vessel, with these data

collected in most detail across ten trips and 14 sets. In total, at-vessel mortality was 38.5% (data

aggregated across trips) with the mean at-vessel mortality (averaged across all sets) 33.6% (Table 19).

This confirms that the survival of skates in offshore net fisheries is lower than observed in inshore

tangle and gillnet fisheries (Ellis et al., 2012b), presumably relating to the higher soak times on

offshore fishing grounds.

Table 18. Preliminary estimates of at-vessel mortality of porbeagle as reported by fishers on commercial netters

Vessel

Alive Dead Fate unknown (including dropped out)

At-vessel mortality (%)

Tagged and released

Sluggish or dropped out alive Total

Base case

Worst case

Best case

Vessel A 1 1 80 14 96 97.6% 97.9% 83.3%

Vessel B 1 1 2 50.0% 50.0% 50.0%

Vessel C 3 1 5 4 13 55.6% 69.2% 38.5%

Total 5 2 86 18 111 92.5% 93.7% 77.5%

Table 19. Preliminary estimates of at-vessel mortality of common skate complex as reported by fishers retrieving tangle nets (Vessel A only)

Vitality

At-vessel mortality

Lively Sluggish Alive (unspecified)

Dead Total

Sets

18 6 3 27 11.1%

39 1 75 115 65.2%

2 0 9 11 81.8%

25 2 1 28 3.6%

21 18 39 46.2%

17 2 11 3 33 9.1%

17 4 4 25 16.0%

15 4 0 19 0.0%

5 0 16 21 76.2%

2 2 4 50.0%

9 14 23 60.9%

8 0 8 0.0%

28 11 39 28.2%

20 4 24 16.7%

Total 205 19 32 160 416 38.5%

Average 33.6%


3.7 Best practice in handling elasmobranchs and developing a ‘Code of conduct’

There have been increasing numbers of studies on elasmobranch discard survival (see Ellis et al., 2014

for a review). An important consideration that is rarely addressed is that the care and short handling

times afforded to fish by scientists and observers can be more benign than could be experienced under

normal commercial fishing conditions. Hence, there has been an increased impetus to consider ways

of promoting best practice in the handling and release of fish (e.g. Jones and Francis, 2012; Poisson et

al., 2012; Australian Fisheries Management Authority, 2014).

Whilst such approaches are relatively well established in some recreational fisheries (Pelletier et al.,

2007; Arlinghaus et al., 2010), there have been fewer studies addressing welfare and handling in

commercial fisheries (Campbell and Cornwell, 2008; Metcalfe, 2009). Similarly, the progress that has

been made to encourage bycatch mitigation for seabirds, sea turtles and marine mammals is less

developed for elasmobranchs, and studies to help develop safe and effective handling and release

protocols for commercial fishers encountering elasmobranchs has received limited consideration

(Poisson et al., 2014).

Bycatch mitigation can take several forms, ranging from modifying fishing gears and fishing practices

to reduce the likelihood of catching vulnerable bycatch species, through to more simply using ‘best

practise’ in terms of handling catches and releasing unwanted catch. For such approaches to be

validated and supported by the fishing industry requires that there is minimal economic impact (i.e.

catch value should be maintained, whether in terms of quantity and/or quality; consideration of costs

that may be incurred for fishing gears and operations) as well as modifications being both practical

and safe. Some measures, such as communication with other vessels in the fleet in order to inform

other fishers where vulnerable species may occur in large numbers, can be implemented easily.

The survivability of the species of concern is also a key factor. If a species to be released is hardy and

typically resilient to capture, then changes to fishing gears and patterns may not actually be required,

as appropriate handling can ensure any bycatch can be released alive. However, if there is a higher

rate of mortality of the bycatch species, and at a level that could result in population level affects,

then there is a stronger rationale to examine how changes to gears and/or fishing patterns may either

reduce the likelihood of capture and/or minimise the mortality of those captures.


Various measures can help maximise the prospects of discarded elasmobranchs surviving capture and

release, such as:

Reducing tow duration / soak time on grounds where vulnerable species may occur

When hauling nets and lines, trying to return lively fish to the sea as soon as practical and before

they go through the net hauler or bait stripper

When processing trawl catches, returning unwanted fish that are alive as soon as possible, and

avoid leaving unwanted fish on deck, and not in direct sunlight

Not using a gaff to bring unwanted fish on board or to move them about

Supporting the fish when lifting them (e.g. using one hand to support the underside and the other

to support the tail) and not lifting or dragging them by their tail, gills or eye sockets

Not standing on the fish

Removing any gear remains (e.g. lines) from the caught specimen or cutting the trace as short/close

to the body as possible.

When releasing fish into the sea, try not to throw them, but place them in the sea (small boats) or

gently slide them head first from as low a height as safely possible.

To promote good handling, it is important to work with the fishing industry and to develop and

dissemination of user-friendly posters (e.g. Figure 18) to convey important messages to the skippers

and crews of fishing vessels.


Figure 18. Example ‘Code of Conduct’


3.8 Lessons learnt: Advantages and limitations of fisher-collected data

There has been increased interest in incorporating fisher knowledge into the assessment and advisory

process. Furthermore, with resources for observers to conduct scientific monitoring often limited,

there is increasing consideration of how fishers could assist in data collection, such as with self-

sampling.

The pilot project undertaken has highlighted several advantages and limitations of dedicated data

collection by fishermen during their normal commercial fishing practices.

Advantages include:

Commercial fishers involved in data collection, so it is an avenue whereby their knowledge and

information can be passed onto scientists (which may in turn result in greater ‘buy-in’ to future

management)

Data collected for species that are not sampled effectively in scientific surveys and/or only seen

occasionally during discard observer trips;

Facilitates data collection for bycatch species throughout the year, allowing improved knowledge

of seasonality;

Effective supply of biological material that would not typically be available from other sources,

thereby allowing the collection of relevant life history data to inform assessments and

management advice

Fishers proactively involved in tagging programmes (including tagging and release fish, and

reporting of tags), which can provide evidence of longer-term survival of discards;

Data on the estimated numbers and/or biomass of selected species can be collected in relation to

the reported catches of the target species, so allowing alternative ways of estimating catch.

There are, however, several limitations, including:

Reliable effort data for nets set under commercial conditions (in terms of total lengths, soak times

and whether any gear damage has affected fishing efficiency) are difficult to record consistently;

Possibilities that assessment scientists will not accept fisher data without independent verification;

Resolution of data can be limited (e.g. numbers of fish boxes multiplied by typical weight; fishers

may be reluctant to supply exact coordinates where large catches are made);


Units can be variable (e.g. smaller catches often counted, larger catches have estimates of

biomass);

More species were often recorded in final set, presumably due to part-filled fish boxes for more

infrequent commercial species only being quantified at the end of the trip;

Potential issues of incorrect species identification, sex or length being recorded.

Other factors that need to be considered include:

Degree and rigour of sampling can be related to workload. For example, larger catches may be

associated with lower quality data as the crew are busier. Similarly, catches of occasional fish to be

discarded may be reported as ‘live’ or ‘dead’, which is not always practicable for larger catches;

Recorded observations were sometimes semi-quantitative or anecdotal, so it is difficult to collate

all information in an unbiased and representative way;

Biological sampling of samples retained frozen can be problematic for some parameters. For

example, the ‘candle’ stage (where uteri are filled with segmented yolky matter, without visible

embryos, see Section 4) of spurdog breaks down, so preventing fecundity determination for this

maturity stage. Similarly, the numbers of pups that may have been aborted is unknown.

Finally, as well as issues relating to ‘data’ there are several other important factors to be considered

in programmes where fishers contribute knowledge and data: stakeholder ‘fatigue’, managing

expectations and trust (Hetherington et al., in prep.). Regular dialogue with fishers (e.g. through

stakeholder meetings and observer trips) and the inclusion of fishery organisations on the PSG were

found to be very beneficial to those programmes collating data and knowledge from fishers.


4 Biological investigations of elasmobranchs

Summary

An appropriate biological and ecological knowledge is needed to underpin the assessment and

advisory processes that inform management of elasmobranchs. Whilst existing surveys have

allowed some of these data to be collected for some species, many data gaps remain. The data

collection presented here focused on those parameters relating to the reproductive biology which

are required for future stock assessments and can provide information to inform biologically

meaningful management measures. Material for future age and growth studies were collected.

During the present study, recent life history data were collected for spurdog, complementing the

extensive data collected for this species by Lowestoft scientists in the 1960s. In total, 1,112

specimens (805 males and 307 females) were examined. Females matured across the 79–86 cm

length range. The length at 50% maturity was about 82 cm, which is similar to previously published

estimates. The maximum fecundity reported was 19 pups, which was higher than values reported

in the 1960s, providing further credence to the hypothesis that spurdog fecundity has increased.

Starry smooth-hound is of increasing interest to UK fishermen, yet the biology and status of this

species had been little studied. In total, 430 specimens (199 males and 231 females) were

sampled. The length at maturity of females was typically between 78 and 87 cm, although one

female matured at 69 cm. Males matured across the 65–74 cm length range. Ovarian and uterine

fecundity ranged from 1–28 and 4–20, and the number of pups increased with maternal size.

Larger females also produced longer and heavier pups. The data collected during the project will

facilitate the development of future demographic assessments, as already developed for spurdog.

Genetic tissue samples from over 300 starry smooth-hound specimens were contributed to a

larger-scale collaborative study across the Northeast Atlantic. Preliminary results of this study

indicate that Mustelus asterias is probably the only Mustelus species to occur in British waters.

Biological sampling of porbeagle sharks (n=53) that were taken as dead bycatch from the south-

west have provided length conversion factors and biological samples for future studies, including

contaminant levels and growth studies.


4.1 Introduction

An improved biological and ecological knowledge of elasmobranchs is considered essential for

developing pragmatic management plans for elasmobranchs. Furthermore, there will be increasing

options for the types of assessment that can be developed as such biological data (as well as

commercial catch data) improve. For example, recent estimates of spurdog fecundity collected by

Cefas scientists (Ellis and Keable, 2008), which suggested that spurdog produce more pups nowadays

than they did in the 1960s (possibly due to a density-dependent increase in fecundity), were used in

the subsequent benchmark assessment (De Oliveira et al., 2013). This was one of the factors that

resulted in the estimated decline in spurdog not being as high as previous exploratory assessments.

Existing trawl surveys undertaken by Cefas have provided extensive data on demersal elasmobranchs,

and such data have been used to further our understanding of distribution, stock structure and

habitats (Pawson and Ellis, 2005; Ellis et al., 2005a; Chevolot et al., 2006), size at maturity (McCully et

al., 2012a), movements (Burt et al., 2013) as well as analyses of time series data (Ellis et al., 2005b,

ICES, 2013).

Although Cefas have maximised the use of existing surveys to collect additional data for

elasmobranchs, including the collection of biological material for genetic studies, existing trawl

surveys have clear limitations in terms of what samples and data can be collected. To augment the

data collected during these surveys, the NEPTUNE project has facilitated more detailed and dedicated

investigations to be undertaken for spurdog and starry smooth-hound. Samples of the former were

collected from the “Shark, Skate and Ray Scientific Bycatch Fishery”. (Section 3), whilst the latter were

sourced from commercial fishermen and from existing trawl surveys. Additional biological data were

also collected for porbeagle retained under the “Shark, Skate and Ray Scientific Bycatch Fishery”.

The main life history data reported here relate to the reproductive biology of the species. The size at

which fish mature, fecundity and reproductive periodicity are all important factors to determine in

fisheries management, as they are key parameters for various assessment methods (e.g. demographic

models). Furthermore, if fisheries managers are to consider size restrictions as possible management

measures, these are often related to the size at maturity. With regards to elasmobranchs, it is also

important to consider measures to ‘protect’ the larger or reproductively active part of the stock, as

there is generally assumed to be a closer relationship between recruitment and spawning stock in

elasmobranchs than in teleosts. Measures to protect large females are often questioned by fishers,

and data to show how fecundity and pup size relate to the size of females provides the evidence to


inform such discussions. Understanding the reproductive cycle and the timings of key events (e.g.

parturition or egg-laying) are also important if seasonal management is to be considered.

Recent studies on the length at maturity of skates (McCully et al., 2012) have indicated that some

previously purported decreases in the size at maturity, which are often viewed as an effect of over-

fishing, have been based on the use of different maturity scales and interpretation of ‘mature’ fish. In

order to ensure that robust maturity data are collected, it is important to use standardised maturity

keys (Table 20) and also, where possible, to collect data that quantitatively support the assignment of

maturity, rather than a more simple visual assessment, which can be somewhat arbitrary and not

necessary equate with any future studies.

Age and growth are also very important parameters to be understood, and whilst not undertaken

during the present project, samples of vertebrae (and spines of spurdog) have been collected to

enable such studies to be undertaken in the near future.

The need to have important biological and ecological data for elasmobranchs has already been noted

in the ‘Shark, Skate and Ray Conservation Plan’, which highlights that ecological information can be

“used to more effectively manage elasmobranchs” (Defra, 2011) and in ICES advice. For example, the

2014 ICES advice for skates and rays stated that “Biological knowledge (age, growth, fecundity) of

many skate species is limited; therefore some life-history assessment models cannot be developed at

the present time” (ICES, 2014a) and for spurdog, it was noted that “Future assessments require

updated and validated growth parameters (particularly for larger individuals)” (ICES, 2014b).

In addition to the biological information shown in greater detail here for starry smooth-hound (Section

4.2), spurdog (Section 4.3) and porbeagle (Section 4.4), various other biological studies have been

undertaken and written up in the form of working documents to the ICES WGEF (summarised in

Section 4.5).


Table 20. Maturity scale for viviparous sharks. Adapted from ICES (2009)

Stage Male Female

A

Immature: Claspers undeveloped, shorter than extreme tips of posterior margin of pelvic fin.

Testes small and thread-shaped, sperm ducts straight

Immature: Ovaries small, gelatinous or granulated, but no differentiated oocytes visible. Oviducts small and thread-shaped, width of shell gland not much greater than the width of the oviduct.

B Developing: Claspers longer than posterior margin of pelvic fin, their tips more structured, but the claspers are soft and flexible and the cartilaginous elements are not hardened.

Testes enlarged, sperm ducts beginning to meander.

Developing: Ovaries enlarged and with more transparent walls. Oocytes differentiated in various small sizes (usually <5mm) and pale in colour. Oviducts small and thread-shaped, width of the shell gland greater than the width of the oviduct, but not hardened.

C Mature: Claspers longer than posterior margin of pelvic fin, cartilaginous elements hardened and claspers stiff.

Testes enlarged, sperm ducts meandering and tightly filled with sperm.

Mature: Ovaries large with very large, yolk-filled oocytes, (> 5mm and often 10–30 mm in diameter). Shell gland fully formed and hard. Uteri fully developed but without yolky matter (Stage D) or embryos (Stages E-F) and not dilated (Stage G)

D Active: Clasper reddish and swollen, sperm present in clasper groove, or flows if pressure exerted on cloaca.

Early gravid (or candle stage): Uteri filled with yolky matter, which may appear unsegmented, or if segmented, without visible embryos.

E

Mid-term gravid: Uteri filled with yolk sacs and small developing embryos that can be counted.

F

Late gravid: Uteri filled with well-developed term pups, and the yolk sac has been absorbed (or is very small).

G

Post partum: Similar to stage C, but with a greater number of degenerating follicles and uteri dilated and flaccid.


4.2 Starry smooth-hound Mustelus asterias 14

Seasonal catches of starry smooth-hound Mustelus asterias have been commonplace around the UK

coast for many years. These were historically discarded due to their low commercial value; however

national landings statistics have indicated a steady increase in reported smooth-hound landings over

the period 2000–2012. Following a prioritisation exercise of the chondrichthyans of the British Isles

(see Section 2), this species was deemed to be a high priority for study, given its life history,

importance of UK waters to the stock and the emerging commercial interest. Furthermore, many

aspects of the biology of this species are poorly known. A biological sampling programme was initiated

to collect data on those life history parameters necessary for any future stock assessment.

The reproductive biology of Mustelus spp. in the Northeast Atlantic has been relatively little studied

to date (Capapé, 1983; Farrell et al., 2010a), despite it having a broad geographical distribution and

being increasingly exploited. The main published study on the reproductive biology from Atlantic

waters is from Farrell et al. (2010a), who reported on ovarian and embryonic fecundities, and alluded

to a possible two year reproductive cycle (12 month gestation and possible resting period) for starry

smooth-hound in the Irish Sea. Further work by Farrell et al. (2010b) investigated the age and growth

of this species, with longevity estimated at 13 and 18.3 years for males and females respectively.

Whilst triakid sharks are often considered relatively productive, relative to some other elasmobranch

groups, the longevity, large size, late age at maturity, low fecundity, protracted gestation periods and

aggregating nature of this species means that exploitation may need to be managed if overfishing,

such as occurred with S. acanthias, is to be avoided. Given their comparable biology, and the fact that

currently there is limited management for smooth-hounds, increasing our knowledge of their life

history at this stage will facilitate more robust assessments and management in the future.

Samples of larger specimens were sourced from commercial fisheries operating in the southern North

Sea and eastern English Channel across an 18-month period. Smaller specimens were collected from

the dead bycatch in surveys of the Celtic Sea and western English Channel undertaken by RV Cefas

Endeavour. In addition to data on length and weight, those parameters needed to understand the

14 Preliminary findings from this work were given in: McCully, S. R. and Ellis, J. R. 2014. Biological studies to

inform management of smooth-hounds (Mustelus spp.) in the North-east Atlantic. Working Document to the

ICES Working Group on Elasmobranch Fishes (WGEF), 17–26 June 2014; 16 pp. Final publication resulting from

this work: McCully Phillips, S. R. and Ellis, J. R. 2015. Reproductive characteristics and other life history

parameters starry smooth-hound Mustelus asterias in British waters. Journal of Fish Biology, 87: 1411–1433.


reproductive biology were recorded, including maturity stage, gonad weight, clasper length (males)

and, for females, width of the shell gland, the number of mature ovarian follicles, maximum follicle

diameter, and uterine and ovarian fecundity. The diet was also quantified, with data on the stomach

contents collected using the fullness/points method and numerical abundance of prey taxa.

Furthermore, biological samples were collected for collaborative studies and future work. Fin clips

were collected from mature adults (n = 305) and their pups (n = 121) for genetic studies. Vertebrae

were dissected out of the body cavity for future studies on age and growth.

In total, 430 specimens (199 males, 27–99 cm LT and 231 females, 28–124 cm LT) were examined

(Figure 19), with information also collected for 238 uterine pups. The relationships between total

weight and length (Figure 20), and gutted weight and length (Figure 21) highlight the increased

variability in total weight in larger specimens, as the weights of the reproductive organs and the liver

will be influenced by maturity stage. Of note is the 119 cm ‘outlier’, which related to a post-partum

female with a very low body mass.

Figure 19. Length frequency distribution of starry smooth-hound examined by sex


Figure 20. Relationship between total weight and total length in starry smooth-hound by sex and maturity stage

Figure 21. Relationship between gutted weight and total length in starry smooth-hound by sex

Given that the reproductive cycle of starry smooth-hound is uncertain, information on the weight of

the liver and the hepatosomatic index (IH, the weight of the liver as a percentage of total weight) were

also collected. This is because the liver is the main site of energy storage and supports the high

maternal investment to pup production over the reproductive cycle. The relationship between liver

weight and total length (Figure 22) is highly variable, especially for larger fish, as it is strongly

influenced by sex and maturity stage. The lowest IH values were seen in gravid females with term pups


(stage F), and the highest values observed in females at stage C, which includes fish at the stage

preceding gestation (Table 21).

Table 21. Hepatosomatic index (IH) of starry smooth-hound by sex and maturity stage

Maturity Stage

Mean IH of females

n Mean IH of males n

A 5.12 72 4.45 58 B 8.58 64 7.10 20 C 9.91 44 5.32 117 D 8.05 9 7.24 2

E 6.96 4 F 3.30 17 G 4.68 3

Figure 22. Relationship between liver weight and total length by sex

The relationship between gonad weight and total length was also examined (Figure 23), with gonad

weight clearly increasing with length but also showing an increased variability between maturity

stages of adult fish, with pregnant and post-partum females having smaller gonads than mature

females not carrying young. Gonad weight was also examined by gonadosomatic index (IG), and the

average IG by sex and maturity stage is given in Table 22. As expected, IG was low in immature and

developing fish (stages A and B) and increased in mature fish (stage C). During the course of gestation,


IG decreased during (stages D and E) and then appeared to increase in the latter stages, when the fish

was either carrying term pups or had recently given birth (stages F and G)

Table 22. Mean gonad weight and gonadosomatic index (IG) by sex and maturity stage of starry smooth-hound

Sex Female Male

Maturity Stage

Mean gonad weight (g)

Mean IG (%) n Mean gonad weight (g)

Mean IG (%) n

A 2.93 0.36 72 1.44 0.24 58 B 5.37 0.32 64 6.15 0.53 20 C 24.53 0.84 44 24.93 1.22 117 D 17.85 0.52 9 21.55 1.27 2

E 11.95 0.32 4 F 23.6 0.43 17 G 19.23 0.44 3

Figure 23. Relationship between gonad weight and total length by sex and maturity stage

The smallest mature and largest immature females recorded in the present study were 69 and 87 cm,

respectively. The smallest mature female that Farrell et al. (2010a) reported was 83 cm – considerably

larger than the smallest mature female recorded in the present study, although this was an

exceptional specimen, and the next smallest female recorded was 78 cm LT. This is also interesting, as

Farrell et al. (2010a) considered females to be mature when follicles were yellow and >3 mm in

diameter, whereas the maturity keys used here (Table 20), which are comparable to those keys

developed within ICES, assign a female as mature when the follicles are larger (>5 mm). The smallest

mature and largest immature males in the present study were 65 and 74 cm, respectively. In order to


help quantify the maturity stage, the width of the shell gland of females (Figure 24) and length of the

claspers of males (Figure 25) were also recorded.

Figure 24. Relationship between width of the shell (or nidamental) gland and total length in female starry smooth-hound by maturity stage

Figure 25. Relationship between outer clasper length and total length in male starry smooth-hound by maturity stage


The number of mature ovarian follicles ranged from 1–28 in mature females. These will not all

necessarily develop into embryos, however, and estimates of ovarian fecundity generally exceed

estimates of uterine fecundity. The diameters of the mature follicles of females (all mature stages)

ranged from 4.1 mm (mid-term gravid female) to 20.7 mm (mature female). Uterine fecundity ranged

from 4–20, which exceeds the maximum uterine fecundity (18) reported by Farrell et al. (2010a),

however they stated that their values may be underestimated due to females aborting pups on

capture. The highest fecundity (20 pups) was a female carrying full-term pups. Uterine fecundity

increased with length (Figure 26). Furthermore there were also positive linear relationships identified

between maternal length and average pup length and weight (Figure 27).

Farrell et al. (2010a) alluded to a possible two year reproductive cycle (12 month gestation and

possible resting period) for starry smooth-hound in the Irish Sea. However, within our mature female

fish, 16 late gravid females with term pups (uterine fecundity 4–20) were also found to have numerous

mature follicles (n = 6–22, length range 6–10 mm). This could indicate a possible annual reproductive

cycle, but more in depth analysis is required to confirm or reject this hypothesis.

Figure 26. Relationship between uterine fecundity (embryos and term pups) and maternal total length in starry smooth-hound


Figure 27. Relationship between the average length (left) and average weight (right) of term pups in relation to maternal length for starry smooth-hound

The main prey items of starry smooth-hound were dominated by crustaceans, including the mantis

shrimp Rissoides desmaresti, amphipods (in smaller individuals), natantid shrimps (Alpheus glaber,

Processa spp., pandalids, Crangon allmanni and Crangon crangon), thalassinoid shrimps (Callianassa

tyrrhena and Upogebia spp.), hermit crabs (Anapagurus laevis and Pagurus bernhardus), squat

lobsters (Galathea spp. and Mundia rugosa), brachyuran crabs (Hyas coarctatus, Macropodia spp.,

Atelecyclus rotundatus, Cancer pagurus, Corystes cassivelaunus, Liocarcinus depurator, Liocarcinus

holsatus, Liocarcinus pusillus and Necora puber). A few specimens had contained squid (the bait from

longline fisheries), with the mussel Mytilus edulis, the brittlestar Ophiura albida and hydroids found

in occasional specimens. In some samples, either Necora puber or Cancer pagurus could be important

prey items, indicating that starry smooth-hound could be an important predator of these

commercially valuable shellfish.


4.3 Spurdog Squalus acanthias

Spurdog was formerly an important commercial species that was targeted in longline and gillnet

fisheries around the British Isles. These fisheries were unmanaged for several decades, and

management measures may have only been restrictive since 2007. Intensive biological sampling of

spurdog was undertaken in the North-east Atlantic in the 1960s, when the fishery was at its peak, but

life-history parameters for recent times are more limited. It is known, however, that many life history

parameters can change in relation to exploitation. The latest stock assessment incorporated both

historic and recent fecundity data, as several studies have suggested that spurdog may have become

more fecund in recent times. Given the low numbers of spurdog taken in Cefas’ current scientific trawl

surveys and restrictions on commercial landings, the specimens collected during the “Shark, Skate and

Ray Scientific Bycatch Fishery” provided a unique opportunity to collect contemporary biological data

to complement data collected by scientists at Lowestoft in the 1960s. The results of these biological

investigations are presented here.

Data collected included total length (cm), total and gutted weight (g), sex, maturity stage, gonad

weight (0.1 g), weight of the stomach contents (0.1 g) and stomach “fullness” (a qualitative score of

0–10) and a description of the stomach contents. Additional data collected for females were shell

gland width (0.1 mm), number of mature ovarian follicles (ovarian fecundity), maximum follicle

diameter (0.1 mm), uterine fecundity (by uterus), and the number of any atretic/undeveloped eggs.

Data were also collected for pups including sex, total length (mm), total weight of the embryo and

yolk sac, and weights of the embryo and yolk sac only (0.1 g). Additional data collected for males were

the inner and outer lengths of the clasper (0.1 mm).

A total of 1,112 specimens were examined (Figure 28), including 805 males (53–92 cm LT) and 307

females (47–122 cm LT), as well as associated pups (n = 935, 98–296 mm LT). The number of spurdog

sampled by vessel, date, sex and length range are summarised in Table 23. Biological samples that

were taken for all specimens where possible included fin clips for genetic analysis, and the spine from

the second dorsal fin and vertebrae (taken from the body cavity corresponding to that part of the body

just anterior to and below the first dorsal fin) for age determination. Samples of stomach contents and

muscle were also retained as frozen material for future studies Table 24.


Figure 28. Length frequency of spurdog examined by sex (black = female, n=307; grey = male, n= 803)

Table 23. Summary of numbers (by sex) and length range of spurdog retained during the project

Vessel Trip date Males Females

N Length range (cm) N Length range (cm)

A

8–12 Oct 2013 64 * 53–92 49*** 47–116 14 Oct 2013 22 73–89 6 72–109 14 Nov 2013 46 58–90 6 98–109 27 Nov 2013 103 60–89 34 60–117 1 Dec 2013 159 57–89 5 61–109

2–8 Dec 2013 86 67–92 8 102–116 10–12 Dec 2013 64 65–91 5 99–107

12 Jan 2014 44 72–87 1 102 16– 19 Mar 2014 21 71–87 8 * 76–109

24 Apr 2014 118 * 55–86 56 56–111 30 Apr 2014 19 **** 58–81 20 * 58–107

Unknown trip 1 5 67–74 6 68–103 Unknown trip 2 17 75–85 2 75–108

B

11–16 Dec 2013 9 76–87 10 97–109 8–10 Jan 2014 – – 13 83–111 9–14 Feb 2014 24 $ 61–87 43 58–113 7–13 Mar 2014 – – 18 * 87–115 7–15 Nov 2014 4 74–86 17 79–122

TOTAL 805 53–92 307 47–122 Footnotes: * included one specimen that had been scavenged internally, so data unavailable for some

parameters (*** = three specimens scavenged; **** = four specimens scavenged); $ length data not collected for two specimens


Table 24. Numbers of samples collected for future studies (preliminary)

Samples Males Females Total

Spine 750 279 1029 $ Vertebrae 803 302 1105

Fin clip 803 303 1106 Muscle 161 87 248

Stomach 160 76 236 $ Spines that were broken or badly damaged were not collected

The relationships between total length and total weight are shown by sex and maturity stage (Figure

29) and gutted weight by sex only (Figure 30). The outlier on these figures was due to an abnormal

female specimen that was emaciated, presumed to be a mature fish given the state of the nidamental

gland, although no mature ovarian follicles were present and the uteri were not flaccid as would be

observed in a post-partum specimen (stage G). In addition, a hook was present in its liver.

The smallest mature and largest immature fish were 79 and 86 cm, respectively (female) and 59 and

79 cm (male). All specimens were mature (100% maturity) when >87 cm (female) and >80 cm (male).

The length at 50% maturity was approximately 82 cm (female) and 66–67 cm (male). The length at

maturity of females seems unchanged from the earlier estimates of Holden and Meadows (1962),

indicating that this life history parameter may not change in relation to overexploitation.

The relationship between gonad weight and total length sex and maturity stage is shown in Figure 31

and summary data on the gonadosomatic index (gonad weight as a percentage of total weight) given

in Table 25.


Figure 29. Relationships between total weight and total length by maturity stage for female (n = 301) and male (n = 792) spurdog

Figure 30. Relationship between gutted weight and total length in female (n = 301) and male (n = 793) spurdog


Figure 31. Relationship between gonad weight and total length by maturity stage for female (n = 298) and male (n = 793) spurdog

Table 25. Mean gonad weight (g) and gonadosomatic index (IG) by sex and maturity stage

Sex Maturity stage Mean gonad

weight (g)

Gonadosomatic index (IG) N

Mean SD Min Max

Fem

ale

A 2.98 0.27 0.09 0.12 0.58 66

B 8.97 0.49 0.15 0.18 0.80 22

C 73.71 2.99 2.24 1.09 12.48 27

D 48.15 1.16 0.42 0.48 2.27 59

E 180.80 3.88 1.29 0.45 7.79 45

F 532.94 10.47 1.90 6.06 13.99 56

G 455.84 9.75 3.93 1.35 16.44 22

X (Abnormal) 28.40 0.91 - - - 1

Mal

e

A 1.08 0.19 0.06 0.13 0.26 6

B 6.66 0.79 0.47 0.12 3.04 48

C 24.75 1.76 0.69 0.68 7.17 128

D 34.51 2.02 0.42 0.97 4.96 609

The qualitative assignment of maturity stage was based on the visual inspection of reproductive

organs (uterus, shell gland and ovaries for females; claspers, testes and degree of coiling in the

epididymus in males). Given that there have been several studies purporting changes in length at

maturity in elasmobranchs that may not have had standardised approaches to assigning maturity

stage, quantitative data were also collected, as this helps validate the assignment of maturity stages.

For females, the width of the shell gland in relation to total length (Figure 32) ranged from ca. 1.5 mm

in an undeveloped uterus to 28 mm in mature fish. The length of the claspers of male fish are often


used a standardised approach to quantifying maturity, as shown here for here for outer and inner

clasper length (Figure 33).

For females, the number of mature ovarian follicles ranged from two (a specimen at stage D) to 22 (a

specimen at stage F), and the maximum follicle diameter for mature follicles for fish at stages C–F

ranged from 10.3–55.3 mm. Post-partum females (stage G) had a minimum of five degenerating

follicles, and a maximum of 21 mature follicles, with the follicle diameters ranging from 27–59.2 mm.

Figure 32. Relationship between width of the nidamental gland and total length in female spurdog (n = 300)


Figure 33. Relationship between inner and outer clasper length and total length in male spurdog by maturity stage

To minimise the potential impact of aborted specimens on fecundity estimations, specimens where

the difference in the number of pups between uteri was ≥4 (similar to Ellis and Keable, 2008) or with

no pups in one of the two uteri were excluded from further analysis (n = 17). For the remaining

specimens (n = 85), uterine fecundity ranged from 2–19 (Figure 34), although these values might still

underestimate fecundity, as some females may have aborted pups from the uteri. In addition to

possible abortion on capture, occasional aborted pups were found in the sample boxes and the

maternal origin could not always be determined. Uterine fecundity for females at stage D (the candle

stage) could not be estimated in most cases, as the membranes separating the yolks broke down

during the freezing process. The total numbers of term pups increased with maternal length (Figure

34), and larger females also produced larger pups, as evident from the relationships between the

average length and average weight of term pups in relation to the maternal length (Figure 35).

The fecundity reported here is higher than reported in earlier studies (e.g. Ford, 1921; Holden and

Meadows, 1964; Gauld, 1979), and provides further support to the hypothesis that there has been a

density-dependent increase in fecundity (see Ellis and Keable, 2008 and references therein).

Stomach contents analysis gave limited data, as a high proportion of fish had stomachs that were

either empty or only with a small quantity of fully digested remains. The maximum weight of stomach

contents was 528 g and an average weight of ca. 36 g. The main prey species that were recorded

included a variety of pelagic fish (mackerel, herring and other clupeids, garfish and horse mackerel),

demersal fish (hake, haddock, poor cod, lesser weaver and common dragonet), and cephalopods

(Loligo spp., Todaropsis eblanae and Eledone cirrhosa).


Figure 34. Ovarian (mature follicles) and uterine fecundity (embryos and term pups) in relation to maternal total length (n = 151 and 85, respectively) in spurdog. Some of these fish may have aborted some pups during capture

Figure 35. Average total length (left) and average weight (right) of term pups in relation to maternal total length (n = 49) in spurdog


4.4 Porbeagle Lamna nasus

There have been several biological investigations on porbeagle shark in the North-east Atlantic (Aasen,

1961; Gauld, 1989; Ellis and Shackley, 1995), yet several important parameters have been lacking, and

there has often been a lack of recent life-history information. Recent studies to better understand the

movements and behaviour of porbeagle (Bendall et al., 2013 and references therein) have been

undertaken. Here, the dead bycatch of porbeagle taken in gillnet fisheries has allowed recent

biological samples and new data to be collected. A total of 53 dead specimens (females = 20; males =

33) were retained by participating vessels, and these were examined in February 2015. The following

data were collected:

Total length (tail extended, measured both over and under the body)

Total length (tail in a natural position, measured both over and under the body)

Fork length (measured both over and under the body)

Standard length (measured both over and under the body, measured from the tip of the

snout to the origin of the pre-caudal pit)

Sex and maturity

Pre-dorsal length

Girth (anterior to the pectoral fins, and posterior to the first dorsal fin)

Height and length of the first dorsal fin

Pre-oral length

Outer and inner clasper length (males only)

Width of the shell gland (females only)

Total body weight and gutted weight (kg)

Weight of the first dorsal, caudal and pectoral fins (g)

Liver and gonad weight (g)

In addition to these measurements, the following samples were also collected for future analyses

Samples of muscle and liver to examine contaminant levels (Cefas)

Vertebrae for age determination (Cefas)

Stomach contents for analyses of diets (Cefas and University of East Anglia)

Heads and jaws (provided to the Natural History Museum, London)

Eyes, dorsal muscle and vertebrae for stable isotope research (Southampton University)

Fin clips for genetic studies (samples collected for Aberdeen University and samples also

retained by Cefas)

Spiral valves for potential microplastic research (as pelagic predators, it is possible they

accumulate microplastics from their prey)

Fins (Cefas and the Shark Trust)

Internal health status bacteriology (Zoological Society London)


There are various approaches for measuring the sizes of large sharks, and lamnid sharks can be

measured as either total length (for which the upper lobe of the caudal fin may be in a natural position,

or flexed down to be in line with the main axis of the body), fork length or standard length. Whilst

most fisheries sampling use measuring boards for which a straight measure can be recorded, larger

fish are sometimes easier to measure with a tape measure over the body, although this then can add

the curvature of the body and so exaggerate true length. For the present sample of porbeagle, four

length measurements were recorded both under and over the body. The relationships between these

different measures showed significant linear relationships, and the parameter for these relationships

summarised in Table 26. The measurement of total length with the tail flexed down and measured

under the body (LT_under) has been used as the standard unit for analyses here, as recommended by

Francis (2006).

All females (119–221 cm) were immature. Males were immature (staged as ‘developing’) over the

length range 113–194 cm (n = 21), with larger males (178–218 cm, n = 12) considered mature. The

relationship between clasper length (shown here as the inner clasper length, measured from the

anterior margin of the cloaca to the posterior tip of the clasper) is shown in Figure 36. The relationships

between total and gutted weight with total length are illustrated in Figure 37.

Given the recent prohibited listing for porbeagle, for which MMO cannot give dispensation for dead

bycatch to be landed, these samples have provided a unique source of contemporary data. Muscle

and liver samples for a sub-sample of the fish are currently being used to examine concentrations of

metals, to complement work undertaken in an earlier study (Bendall et al., 2014).


Table 26. Relationships between alternative length measurements with total length in porbeagle (n = 53), where total length refers to the total length with the upper lobe of the caudal fin flexed down (LT_under) and measured under the body. Relationships given as an equation and in proportional terms (percentage of LT_under).

Measurement Equation r2

Total length (flexed), measured over body (LT_over) LT_over = 1.0279.LT_under – 0.3109 0.99

Total length (natural), measured under body (LN_under) LN_under = 0.9906.LT_under – 3.9749 0.99

Total length (natural), measured over body (LN_over) LN_over = 0.9979.LT_under – 1.0713 0.99

Fork length, measured under body (LF_under) LF_under = 0.877.LT_under – 3.6981 0.99

Fork length, measured over body (LF_over) LF_over = 0.8919.LT_under – 1.4538 0.99

Standard length, measured under body (LS_under) LS_under = 0.7688.LT_under – 2.1165 0.99

Standard length, measured over body (LS_over) LS_over = 0.7849.LT_under – 0.2599 0.99

Measurement % of LT_under (mean ± SD and range)

Total length (flexed), measured over body (LT_over) 102.6 ± 1.31 (100.0–106.7)

Total length (natural), measured under body (LN_under) 96.7 ± 1.72 (91.9–101.9)

Total length (natural), measured over body (LN_over) 99.1 ± 1.82 (95.3–102.6)

Fork length, measured under body (LF_under) 85.5 ± 0.99 (83.3–88.9)

Fork length, measured over body (LF_over) 88.3 ± 1.34 (85.2–92.5)

Standard length, measured under body (LS_under) 75.6 ± 1.07 (74.1–79.1)

Standard length, measured over body (LS_over) 78.3 ± 1.34 (75.6–82.2)

Figure 36. Relationships between inner clasper length (taken as the distance from the anterior margin of the cloaca to the tip of the clasper) for male porbeagle (n = 33) for developing (open circles) and mature (closed circles) fish. Total

length refers to total length with the upper lobe of the caudal fin depressed, measured under the body

0

50

100

150

200

250

300

350

400

50 70 90 110 130 150 170 190 210 230

Inn

er c

lasp

er le

ngt

h (

mm

)

Total length (cm)


Figure 37. Length-weight relationships for porbeagle (n = 53) for (a) total weight and (b) gutted weight. Total length refers to total length with the upper lobe of the caudal fin depressed, measured under the body

y = 1E-05x2.908

R² = 0.9634

0

20

40

60

80

100

50 100 150 200 250

Tota

l we

igh

t (k

g)

Total length (cm)

y = 7E-06x3.0079

R² = 0.9715

0

20

40

60

80

50 100 150 200 250

Gu

tte

d w

eig

ht

(kg)

Total length (cm)

(a)

(b)


4.5 Other biological investigations

This section provides the abstracts of four other working documents presented to the ICES WGEF

providing biological information on elasmobranch fish.

4.5.1 Summary results from opportunistic tagging programmes for smooth-hound Mustelus spp.,

greater-spotted dogfish Scyliorhinus stellaris and tope Galeorhinus galeus around the British

Isles

Since 2000, research vessel groundfish surveys and other field programmes have been used as

platforms to opportunistically tag and release various elasmobranch species, including smooth-

hounds Mustelus spp. (n = 717), greater-spotted dogfish Scyliorhinus stellaris (n = 567) and tope

Galeorhinus galeus (n = 159). Additional opportunities during Fishery Science Partnership (FSP) and

Defra-funded research projects that targeted other elasmobranch species have also been used to tag

these species. Overall, 74% of the releases were from groundfish surveys. Most specimens were

tagged and released with Petersen disc and were tagged around much of the British Isles, although

the greatest tagging activity occurred in the Irish Sea, Celtic Sea and, to a lesser extent, the western

English Channel and southern North Sea. The overall return rate was relatively low (1.6%), and to date

a total of 24 fish were returned (eight greater-spotted dogfish, four tope and 12 smooth-hounds).

Nevertheless, the recaptured fish were at liberty for a total 9568 days. Although the number of returns

was limited, useful information was obtained about their biology and behaviour that would not have

been realised if it was not for the programme. In general, greater-spotted dogfish were recaptured

close to their release positions, and there was no indication of mixing between the western English

Channel and Irish Sea. In contrast, tope and smooth-hounds travelled further and there was mixing

between the North Sea and Celtic Seas ecoregions. The greatest time at liberty for an individual fish

was for a 2403 days for a tope, and the furthest that a fish had travelled was 408 km, which was for a

smooth-hound that had travelled from the western English Channel to the southern North Sea in 73

days, recording the highest average daily speed of 5.6 km/day.15

15 Burt, G. J., Silva, J. F., McCully, S. R., Bendall, V.A. and Ellis, J. R. 2013. Summary results from opportunistic tagging programmes for smooth-hound Mustelus spp., greater-spotted dogfish Scyliorhinus stellaris and tope Galeorhinus galeus around the British Isles. Working Document to the ICES Working Group on Elasmobranch Fishes, Lisbon, June 17–21 2013; 12 pp.


4.5.2 A global review of elasmobranch discard survival studies and implications in relation to the

EU ‘discard ban’

There is a need to better understand the survivorship of discarded fish, both for commercial stocks

and species of management concern. The landing obligations that are currently being phased in as

part of the European Union’s reformed Common Fisheries Policy means that an increasing number of

fish stocks, with certain exceptions, should not be discarded unless it can be demonstrated that there

is a high probability of survival. This working document reviews various approaches which can be used

to examine the discard survival of elasmobranchs (in terms of at-vessel mortality and post-release

mortality), with relevant findings summarised by the main fishing gears used. Discard survival varies

with biological attributes (e.g. species, size, sex and mode of gill ventilation) as well as variety of factors

associated with capture (e.g. gear type, soak time, catch weight and composition, handing practices

and temperature). In general, demersal species with buccal-pump ventilation have a higher survival

than obligate ram ventilators; some studies indicate that females may have a higher survival than

males; and it is apparent that some taxa (e.g. hammerhead sharks Sphyrna spp. and thresher sharks

Alopias spp.) are prone to high rates of mortality when caught.16

4.5.3 Bycatch and discarding patterns of dogfish, sharks and catsharks taken in commercial

fisheries around the British Isles

The discard and retention patterns of dogfish, sharks and catsharks taken as a bycatch in UK

commercial fisheries were examined. Data were collected primarily on English vessels fishing on the

continental shelf of the North Sea ecoregion (ICES Divisions IV a–c, VIId) and Celtic Seas ecoregion

(ICES Divisions VIa, VIIa–c,e–k). Vessels examined represented four main gear types (otter, beam and

Nephrops trawls, and gillnet), with only limited data available for longline and mid-water trawl. Beam

trawlers generally captured proportionally more small (juvenile) dogfish and catsharks than otter

trawlers. Gillnets were the most size selective gear. Data on the elasmobranch catches from Nephrops

trawlers were frequently too limited to draw an accurate discard/retention pattern, which may reflect

a low catchability of sharks by this gear and/or that elasmobranchs are not abundant on these muddy

fishing grounds. In general, juvenile sharks (Triakidae and Squalidae) were usually discarded, and

16 Ellis, J. R., McCully, S. R. and Poisson, F. 2014. A global review of elasmobranch discard survival studies and implications in relation to the EU ‘discard ban’. Working Document to the ICES Working Group on Elasmobranch Fishes (WGEF), 17–26 June 2014; 48 pp.


larger fish retained, whilst catsharks (Scyliorhinidae) were generally discarded. Discarding patterns are

discussed in relation to recent changes in management regulations.17

4.5.4 Demersal elasmobranchs in the western English Channel (ICES Division VIIe)

In 2006 a new Cefas beam trawl survey was initiated in the western English Channel to provide

information on sole Solea solea and plaice Pleuronectes platessa, as well as providing information on

other demersal fish and ecosystem components. The western English Channel is an important area for

a number of demersal elasmobranchs, with species of interest including undulate ray Raja undulata,

which is locally abundant and, prior to their prohibited status, was an important commercial species

in some inshore areas. This study presents preliminary results on the spatial distribution and size

frequency for all dogfish, catsharks, skates and rays encountered during 2006–2014. Results indicated

that species including common skate Dipturus batis-complex, cuckoo ray Leucoraja naevus, thornback

ray Raja clavata and undulate ray showed persistent association with specific sites, with lesser-

spotted dogfish Scyliorhinus canicula and smooth-hounds Mustelus spp. distributed over much of the

survey grid. Juvenile skates were routinely caught, as beam trawls are more selective for smaller fish.

Mature specimens of the smaller bodied skate species, such as cuckoo ray, were also represented in

the catch, while fewer mature specimens of the larger bodied skate species (e.g. undulate, blonde and

thornback ray) were observed.18

17 Silva, J. F., Ellis, J. R., Catchpole, T. L. and Righton, D. 2013. Bycatch and discarding patterns of dogfish and sharks taken in commercial fisheries around the British Isles. Working Document to the ICES Working Group on Elasmobranch Fishes, Lisbon, June 17–21 2013; 31 pp. 18 Silva, J. F., McCully, S. R., Ellis, J. R. and Kupschus, S. 2014. Demersal elasmobranchs in the western English Channel (ICES Division VIIe). Working Document to the ICES Working Group on Elasmobranch Fishes (WGEF), 17–26 June 2014; 28 pp.


5 Concluding remarks

The reformed Common Fisheries Policy has clear objectives with regards the status of our marine

resources. It states that “the exploitation of marine biological resources restores and maintains

populations of harvested stocks above levels that can produce the maximum sustainable yield … by

2015 (and) ... no later than 2020”, that “An ecosystem-based approach to fisheries management needs

to be implemented” and that management of our fisheries should be coherent with European

biodiversity targets. In terms of fisheries management, it also highlights that “Technical measures may

include… Requirements for fishing vessels to cease operating in a defined area for a defined minimum

period in order to protect temporary aggregations of endangered species, spawning fish, fish below

minimum conservation reference size, and other vulnerable marine resources”.

Elasmobranchs feature among our more vulnerable fish species, and so there is increasing interest in

this group of fish from conservation bodies and the public. Whilst fisheries scientists have highlighted

the need for improved management of these stocks for several decades, management at a European

level has evolved slowly. For example, although a TAC for skates in the North Sea was first established

in 1999, catch limits for skates were only established for other areas in 2009. Similarly the TAC and

associated management of spurdog, initiated from 2000, may only have become restrictive since 2007

(De Oliveira et al., 2013).

Given a history of over-exploitation and lack of management actions, some of the elasmobranchs of

northern Europe have shown signs indicative of near-extirpation (e.g. angel shark and white skate)

whilst others have shown marked declines in either geographic distribution (e.g. common skate

complex) or population size, as seen in spurdog (Brander, 1981; Rogers and Ellis, 2000; Ellis et al.,

2010). In contrast, however, it is important to also note that several stocks of demersal elasmobranchs

have shown recent increases in relative abundance.

There are many limitations to the data that are available for elasmobranchs. Much of the historical

landings data were not species-specific, some data confound multiple species, and species-

misidentifications are a common occurrence in both landings and observer data. Whilst data quality

appears to be improving, much of the data are of too restrictive a time series to inform the types of

assessment that are undertaken routinely for many of our teleost stocks. Against this background,


there are two important sources of information that have been used to inform management advice;

fishery-independent survey data and biological information.

Trawl surveys, primarily those coordinated under the auspices of the ICES Working Group on Beam

Trawl Surveys (WGBEAM) and the International Bottom Trawl Survey Working Group (IBTSWG), have

provided data to support the advice on stock status for several of the smaller-bodied and more

frequently encountered demersal elasmobranchs. Data from existing trawl surveys could usefully be

further investigated to better understand the temporal dynamics of the demersal elasmobranch

assemblage, especially to inform how environmental parameters and multispecies interactions may

influence the interpretation of the ‘traditional’ single-species assessments and advice provided by

ICES. However, more targeted surveys, including work with the fishing industry and studies to improve

our biological knowledge, are needed to underpin any advice for those species not sampled effectively

in surveys, as shown recently for undulate ray Raja undulata (Ellis et al., 2012a; STECF, 2015).

The current project has supported a proportion of our ongoing and continuing work on elasmobranch

fish, and will provide data for use in future meetings of the ICES WGEF, further peer-reviewed

publications and other studies, thereby supporting the development of biologically-meaningful

assessments and management.

The current project has compiled an up-to-date inventory of the elasmobranch and holocephalan

fishes of the British Isles and adjacent areas. Whilst some earlier studies have identified data gaps,

these works have only considered a subset of species (e.g. those species listed on conservation

instruments). A more holistic prioritisation exercise to consider all species in a consistent approach,

as also undertaken by the IUCN’s Shark Specialist Group, has enabled species to be ranked

incorporating their commercial importance, conservation interest, biological characteristics and the

relative importance of British waters to the species. This approach clearly ranked many of the known

threatened species highly (e.g. angel shark and flapper skate), but commercial species of less

conservation interest would also rank quite highly. Whilst the status of some of these species may be

gauged by existing surveys, some species that ranked quite highly, such as starry smooth-hound and

blonde ray, are not sampled effectively in existing surveys and the status of such species is somewhat

uncertain.

Whilst such approaches have the benefits of including all species, it does means that they are

invariably more qualitative, as many data-limited stocks are included. Such approaches can be


developed further using Productivity-Susceptibility Analyses and, as PSAs are best applied for specified

fisheries, a more defined suite of fish can be included and the approaches start to become more

quantitative.

PSAs were undertaken for the elasmobranch fish taken in ‘otter trawl’ and ‘gillnet’ fisheries in the

Celtic Sea, and this enabled novel approaches, such as the inclusion of expert opinion and modelling

confidence scoring, to be trialled and applied. The outputs of the PSA, as could be expected, ranked

many of the species currently under very conservative management as the most vulnerable. Similarly,

those species for which the stock status is thought to be no cause for concern ranked as least

vulnerable. Several of the intermediate species, which are relatively vulnerable, are often data limited

stocks. It will become increasingly important to evaluate the status of such species in the future.

Fisheries in the Celtic Sea are known to encounter several of the species of conservation interest,

particularly some of the larger netters that deploy both gillnets (in which spurdog and porbeagle can

be an important bycatch) and tangle nets, which are highly effective at catching batoids, including

common skate.

A pilot project to allow fishers to help collect data on these vessels was initiated, as coverage of

observer programmes is often limited and so risks missing some of the potential seasonality. The type

and quality of data that fishers can collect at sea is variable. Vessels deploying smaller amounts of nets

catch fewer fish, and so more quantitative data can be collected. In contrast, vessels encountering

large quantities of fish invariably risk having more variability in the quality of additional data that are

recorded. Another issue related to vessels operating with net is estimating ‘fishing effort’, as the

numbers of nets and soak times may not always be recorded accurately, and it is not generally known

where gear damage (which would then affect overall catches) has occurred. For the present study, the

catches of species of concern have been related as a function of the reported weight of the main target

species. The pilot project was only based on three vessels operating over 5–10 months, and so these

data have not been raised to reported landings of the target species by the gears in question.

Data collected by commercial fishers in this study (see Section 3.6), and from previous Defra-funded

projects (e.g. Ellis et al., 2008, 2012b), have indicated that at-vessel mortality can be relatively low for

some elasmobranchs and there are also some data regarding their short-term survival (Catchpole et

al., 2007). Whilst there are an increasing number of studies from around the world on the longer-term


post-release mortality of elasmobranchs (see Section 4.5.2), further studies may be required if

derogations from the landings obligation are to be sought.

The pilot project also allowed vessels to retain and land (for scientific study only) specimens of spurdog

and porbeagle. Catches of spurdog in trawl surveys are sporadic, and so biologically meaningful

sample sizes cannot be collected over a short time. Whilst there have been several studies on the

biology of spurdog over the last century (see Ellis and Keable, 2008, and references therein), recent

studies have been more limited. Contemporary biological data were collected for over 1 000

specimens. The data presented here focused on reproductive parameters, but spines and vertebrae

were also collected, and future studies could usefully reappraise age and growth parameters. Cefas

also have a large collection of spines collected from the 1960s (which could be used to examine

temporal changes in growth parameters) and have also collected spines from dead spurdog caught in

ground fish surveys, including smaller fish.

Starry smooth-hound ranked quite highly in the prioritisation exercise and was one of the more

vulnerable species in the PSA. Despite increased exploitation of this species, there is currently no

management for this species. The increased landings of starry smooth-hound has allowed cost-

effective data collection for this species, with a full range of biological parameters to be collected for

the stock. These data (length at maturity, fecundity at length) will be important input parameters for

future stock assessments undertaken in the ICES community.

Previous work undertaken by members of the project team have indicated that several published

studies purporting a decreased length at maturity for elasmobranchs (which are claimed to relate to

the impacts of fishing) may simply be artefacts due to inconsistent use of maturity keys and

misinterpretation of maturity data. It is increasingly important that biological studies provide more

robust estimates of life history parameters using better defined keys and improved quantification of

reproductive stages.


6 Acknowledgments

We gratefully acknowledge the continued support of the Department for Environment, Food and Rural

Affairs towards elasmobranch research. We thank the Project Steering Group for their support and

input, including Carole Kelly, Kirsty McGregor and Jamie Rendell (Defra), Paul Trebilcock (CFPO), Clare

Bowers (MMO), Ali Hood (Shark Trust) and Matthew Gollock (Zoological Society of London). The

project benefitted greatly from the assistance of the owners, skippers and crews of the vessels that

assisted with the project and provided data and specimens. The following Cefas staff assisted with

biological sampling: Dave Brown, Gary Burt, Scott Davis, Matt Eade, Rebecca Faulkner, Denise

Goldsmith, Charlotte Jennings, Thomas Maes, Peter Randall, Ainsley Riley, Joanne Smith, Camilla

Sguotti and Nicola Travell. Additional thanks to our national and international colleagues, including

Oliver Crimmen (Natural History Museums, London), Guzman Diez (AZTI), Edward Farrell (University

College Dublin), Graham Johnston (Marine Institute), and Bernard Séret (Muséum national d'Histoire

naturelle, Paris), for their assistance. David Righton (Cefas) and the anonymous reviewer provided

valuable comments on the report.


7 References

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commercial fishers in Southern Australia. Australian Fisheries Management Authority,

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guide/

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8 Annexes

8.1 List of acronyms

BTS Beam Trawl Survey

CITES Convention on International Trade in Endangered Species of Wild Fauna and Flora

CFP Common Fishery Policy

CFPO Cornish Fish Producers Organisation

CPOA Community Plan of Action

CPUE Catch per unit effort

Defra Department for Environment, Food and Rural Affairs

EC / EU European Commission / European Union

ERA Ecological Risk Assessment

FAO Food and Agriculture Organisation

FV Fishing Vessel

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

IUCN International Union for Conservation of Nature

LOA Length Overall

MLL Maximum landing length

MLS Minimum landing size

MMO Marine Management Organisation

MPA Marine Protected Area

MSY Maximum Sustainable Yield

NOAA National Oceanic and Atmospheric Administration

NWWAC North Western Waters Advisory Council

PSA Productivity Susceptibility Analysis

RV Research Vessel

SFC Sea Fishery Committee

STECF Scientific, Technical and Economic Committee for Fisheries

TAC Total Allowable Catch

WGEF Working Group on Elasmobranch Fishes


8.2 Outputs from project and associated work

During the period 2013–2015, Cefas scientists contributed to the following outputs in relation to

elasmobranch fish. These outputs have been supported by Defra-funding through various projects,

including MA funding and the NEPTUNE project (MB5201). Members of the project team also

contributed to several of the species accounts drafted during the European elasmobranch Red List

Workshop (Plymouth, 12–15 May 2014; see Nieto et al., 2015). Members of the project team also

contributed to all chapters related to chondrichthyan fish in the ‘Fish atlas of the Celtic Sea, North Sea,

and Baltic Sea’ (Heessen et al., 2015)

(a) Peer-reviewed publications De Oliveira, J. A. A., Ellis, J. R. and Dobby, H. 2013. A stock assessment model for Northeast Atlantic

spurdog, incorporating fecundity data to estimate the extent of density dependence in pup

production. ICES Journal of Marine Science, 70: 1341–1353.

Available from: http://icesjms.oxfordjournals.org/content/70/7/1341.full

Gubili, C., Sims, D. W., Veríssimo, A., Domenici, P., Ellis, J., Grigoriou, P., Johnson, A. F., McHugh, M.,

Neat, F., Satta, A., Scarcella, G., Serra-Pereira, B., Soldo, A., Genner, M. J. and Griffiths, A. M. 2014. A

tale of two seas: Contrasting patterns of population structure in the small-spotted catshark across

Europe. Royal Society Open Science, 1: 140175; 18 pp.

Available from: http://rsos.royalsocietypublishing.org/content/1/3/140175

McCully Phillips, S. R., Scott, F. and Ellis, J. R. 2015. Having confidence in Productivity Susceptibility

Analyses: A method for underpinning scientific advice on skate stocks? Fisheries Research, 171: 87–

100.

Available from: http://www.sciencedirect.com/science/article/pii/S016578361500017X

McCully Phillips, S. R. and Ellis, J. R. 2015. Reproductive characteristics and other life history

parameters starry smooth-hound Mustelus asterias in British waters. Journal of Fish Biology, 87: 1411–

1433.

Available from: http://onlinelibrary.wiley.com/doi/10.1111/jfb.12826/full

(b) Other publications

Bendall, V., Ellis, J. R., Hetherington, S. J., McCully, S. R., Righton, D. and Silva, J. F. (2013). Preliminary

observations on the biology and movements of porbeagle Lamna nasus around the British Isles.

Collective Volume of Scientific Papers ICCAT, 69: 1702–1722.

Available from: http://www.iccat.int/Documents/CVSP/CV069_2013/n_4/CV069041702.pdf

Heessen, H. J. L., Daan, N. and Ellis, J. R. (Eds.) (2015). Fish atlas of the Celtic Sea, North Sea, and Baltic

Sea. Wageningen Academic Publishers / KNNV Publishing, 572 pp.

http://icesjms.oxfordjournals.org/content/70/7/1341.full

http://rsos.royalsocietypublishing.org/content/1/3/140175

http://www.sciencedirect.com/science/article/pii/S016578361500017X

http://onlinelibrary.wiley.com/doi/10.1111/jfb.12826/full

http://www.iccat.int/Documents/CVSP/CV069_2013/n_4/CV069041702.pdf


McCully, S. R., Scott, F., Ellis, J. R., Pilling, G. M. 2013 Productivity and Susceptibility Analysis:

Application and suitability for data poor assessment of elasmobranchs in Northern European seas.

Collective Volume of Scientific Papers ICCAT, 69: 1679–1698.

Available from: http://www.iccat.org/Documents/CVSP/CV069_2013/n_4/CV069041679.pdf

Nieto, A., Ralph, G. M., Comeros-Raynal, M. T., Kemp, J., García Criado, M., Allen, D. J., Dulvy, N. K.,

Walls, R. H. L., Russell, B., Pollard, D., García, S., Craig, M., Collette, B. B., Pollom, R., Biscoito, M.,

Labbish Chao, N., Abella, A., Afonso, P., Álvarez, H., Carpenter, K. E., Clò, S., Cook, R., Costa, M. J.,

Delgado, J., Dureuil, M., Ellis, J. R., Farrell, E. D., Fernandes, P., Florin, A-B., Fordham, S., Fowler, S., Gil

de Sola, L., Gil Herrera, J., Goodpaster, A., Harvey, M., Heessen, H., Herler, J., Jung, A., Karmovskaya,

E., Keskin, C., Knudsen, S. W., Kobyliansky, S., Kovačić, M., Lawson, J. M., Lorance, P., McCully Phillips,

S., Munroe, T., Nedreaas, K., Nielsen, J., Papaconstantinou, C., Polidoro, B., Pollock, C. M., Rijnsdorp,

A. D., Sayer, C., Scott, J., Serena, F., Smith-Vaniz, W. F., Soldo, A., Stump, E. and Williams, J. T. 2015.

European Red List of marine fishes. Luxembourg: Publications Office of the European Union, iv + 81

pp. Available from:

http://ec.europa.eu/environment/nature/conservation/species/redlist/downloads/European_marin

e_fishes.pdf

(c) Working Documents to ICES WGEF Bendall, V., Hetherington, S., O’Brien, C., Righton, D., Riley, A. and Cragg, A. 2014. Proposal for a UK

pilot project to develop a real-time spurdog by-catch avoidance programme to mitigate the potential

for spurdog to become a choke species and so minimize fishing induced mortality. Working Document

to the ICES Working Group on Elasmobranch Fishes (WGEF), 17–26 June 2014; 12 pp.

Burt, G. J., Silva, J. F., McCully, S. R., Bendall, V.A. and Ellis, J. R. 2013. Summary results from

opportunistic tagging programmes for smooth-hound Mustelus spp., greater-spotted dogfish

Scyliorhinus stellaris and tope Galeorhinus galeus around the British Isles. Working Document to the

ICES Working Group on Elasmobranch Fishes, Lisbon, June 17–21 2013; 12 pp.

Ellis, J. R. and McCully, S. R. 2013. An overview of the sharks, skates and rays (Elasmobranchii) and

rabbit fish (Holocephali) of the British Isles, and prioritisation of species of interest. Working Document

to the ICES Working Group on Elasmobranch Fishes, Lisbon, June 17–21 2013; 41 pp.

Ellis, J. R., McCully, S. R. and Poisson, F. 2014. A global review of elasmobranch discard survival studies

and implications in relation to the EU ‘discard ban’. Working Document to the ICES Working Group on

Elasmobranch Fishes (WGEF), 17–26 June 2014; 48 pp.

McCully, S. R. and Ellis, J. R. 2014. Biological studies to inform management of smooth-hounds

(Mustelus spp.) in the North-east Atlantic. Working Document to the ICES Working Group on

Elasmobranch Fishes (WGEF), 17–26 June 2014; 16 pp.

http://www.iccat.org/Documents/CVSP/CV069_2013/n_4/CV069041679.pdf

http://ec.europa.eu/environment/nature/conservation/species/redlist/downloads/European_marine_fishes.pdf

http://ec.europa.eu/environment/nature/conservation/species/redlist/downloads/European_marine_fishes.pdf


Silva, J. F., Ellis, J. R., Catchpole, T. L. and Righton, D. 2013. Bycatch and discarding patterns of dogfish

and sharks taken in commercial fisheries around the British Isles. Working Document to the ICES

Working Group on Elasmobranch Fishes, Lisbon, June 17–21 2013; 31 pp.

Silva, J. F., McCully, S. R., Ellis, J. R. and Kupschus, S. 2014. Demersal elasmobranchs in the western English Channel (ICES Division VIIe). Working Document to the ICES Working Group on Elasmobranch Fishes (WGEF), 17–26 June 2014; 28 pp.

(d) Presentations Bendall, V. A., Hetherington, S. J., Duggan, K., Corton, J. and Randall, P. 2013. Shark ByWatch UK –

Regional bycatch awareness of sharks and rays in the southern North Sea. 17th European

Elasmobranch Association Annual Scientific Conference, Plymouth.

Bendall, V., Law, R., Barber, J., Papachlimitzou, A., Bolam, T., Hetherington, S., Silva, J., McCully, S.,

Righton, D., Ellis, J. and Maes, T. 2013. Bioaccumulation of trace metals and organochlorines in North-

East Atlantic porbeagle sharks Lamna nasus. 17th European Elasmobranch Association Annual

Scientific Conference, Plymouth.

Ellis, J. R., McCully, S. R. and Silva, J. F. 2013. The skate complex of the British Isles: current status,

discard survival and management options. 17th European Elasmobranch Association Annual Scientific

Conference, Plymouth.

Heessen, H. J. L., Daan, N. and Ellis, J. R. 2014. Elasmobranchs of the North-East Atlantic Shelf. 18th

European Elasmobranch Association Annual Scientific Conference, Leeuwarden.

Hetherington, S. J. and Bendall, V. A. 2013. “Science & Fishery Collaboration”: A new collaborative

approach to scientists and fishermen actively working together to provide evidence and inform policy

needs. 17th European Elasmobranch Association Annual Scientific Conference, Plymouth.

McCully, S. R. and Ellis, J. R. 2013. Biological studies to inform management of smooth-hounds

Mustelus spp. in the Northeast Atlantic. 17th European Elasmobranch Association Annual Scientific

Conference, Plymouth.

McCully, S. R. and Ellis, J. R. 2013. Chondrichthyan fish of the British Isles: Prioritising species for

further study and the utility of Ecological Risk Assessments for informing management. 17th European

Elasmobranch Association Annual Scientific Conference, Plymouth.

Silva, J. F., Ellis, J. R., Catchpole, T. L. and Righton, D. 2013. Bycatch and discarding patterns of dogfish

and sharks taken in commercial fisheries around the British Isles. 17th European Elasmobranch

Association Annual Scientific Conference, Plymouth.

Silva, J. F., McCully Phillips, S. R., Ellis, J. R. and Kupschus, S. 2014. Demersal elasmobranchs in the

western English Channel. 18th European Elasmobranch Association Annual Scientific Conference,

Leeuwarden.


8.3 Taxonomic list of chondrichthyans of the British Isles and adjacent waters

This annotated list of the chondrichthyan fishes of the British Isles and adjacent waters gives sources of information in relation to their occurrence and

distribution in the region. Rank refers to the taxonomic ordering.

Family Rank Scientific name Common name Distribution around British Isles Source(s)

CLASS ELASMOBRANCHII ORDER HEXANCHIFORMES

Hexanchidae 1 Hexanchus griseus Bluntnose six-gill shark

Occurs on the outer continental shelf and in the deep-water to the west of the British Isles, including the Porcupine Seabight

Went (1979); Boeseman (1984a); Haedrich & Merrett (1988); Wheeler (1992); Gordon et al. (1996); Ellis et al. (2005)

2 Heptranchius perlo Sharpnose seven-gill shark

Although typically caught in deep waters south of the British Isles, this species is caught occasionally on the continental shelf and slope off the south-west British Isles

Boeseman (1984a); Cappetta et al. (1985); Henderson & Williams (2001)

Chlamydoselachiidae 3 Chlamydoselachus anguineus

Frilled shark Deep water of the southern and western British Isles Wheeler (1962, 1992); Boeseman (1984b)

ORDER LAMNIFORMES

Odontaspidae – Odontaspis spp. Sand tiger

Odontaspis ferox is reported from the Bay of Biscay. Recently a dead specimen (ca. 2.5 cm LT) of Odontaspis spp. was found washed ashore at Agon-Coutainville (French coast of the English Channel) (13/08/2012), but no records of live individuals in the area.

Quéro (1984a); Fergusson et al. (2008)

Mitsukurinidae – Mitsukurina owstoni Goblin shark No records from UK or Irish waters, although there have been several records from the northern Bay of Biscay, at latitudes of up to 46°N

Quéro (1984b)

Lamnidae – Carcharodon carcharias

White shark No records from UK or Irish waters, although there is an authenticated record from the northern Bay of Biscay, at a latitude of ca. 46°N (Quéro et al., 1978)

Quéro et al. (1978); Quéro (1984c).

4 Isurus oxyrinchus Shortfin mako Oceanic species, vagrants of which may occur to the west of the British Isles. May be confused with Lamna nasus and some records need to be treated with caution

Wheeler (1992); Quéro (1984c).Henderson et al. (1999)



5 Lamna nasus Porbeagle shark Widespread around the British Isles, with areas of high abundance known along south-western and western coasts, and North Sea

Quéro (1984c); Wheeler (1992)

Cetorhinidae 6 Cetorhinus maximus Basking shark Widespread around the British Isles, with areas of high abundance along south-western and western coasts

Quéro (1984d); Wheeler (1992); Southall et al. (2005)

Alopiidae 7 Alopias superciliosus Big-eye thresher shark

Oceanic species. Typically occurs further south, but a large individual was captured to the west of the British Isles.

Quéro (1984e); Thorpe (1997)

8 Alopias vulpinus Thresher shark Large pelagic species that may occur all around the British Isles, although caught relatively infrequently

Quéro (1984e); Wheeler (1992); Ellis (2004)

ORDER CARCHARHINIFORMES

Scyliorhinidae 9 Apristurus aphyodes White ghost catshark

Overall distribution unclear, as the taxonomy of this genus is problematic. This species has been reported in the deep waters west of the British Isles

O'Hea et al. (2008), Neat et al. (2008)

10 Apristurus laurussonii Iceland catshark Overall distribution unclear, as the taxonomy of this genus is problematic. This species has been reported in the deep waters west of the British Isles

Quéro (1984f); O'Hea et al. (2008), Neat et al. (2008)

– Apristurus maderensis Madeiran catshark

Although this nominal species was reported from the deep waters west of the British Isles, it has more recently been treated as a synonym of Apristurus laurussonii.

Neat et al. (2008)

11 Apristurus manis Ghost catshark Overall distribution unclear, as the taxonomy of this genus is problematic. This species has been reported in the deep waters west of the British Isles

O'Hea et al. (2008); Neat et al. (2008)

12 Apristurus melanoasper

Black roughscale catshark


O'Hea et al. (2008); Neat et al. (2008)

13 Apristurus microps Smalleye catshark


Neat et al. (2008)

– Galeus atlanticus Atlantic sawtail catshark

No authenticated records from the UK or Ireland, but often confused with Galeus melastomus, and now known to occur in the southern Bay of Biscay (Banon et al., 2010)

Banon et al. (2010)

14 Galeus melastomus Black-mouth dogfish

Occurs on the outer continental shelf (including the deeper waters of the Irish Sea) and continental slope all around the British Isles

Went (1979); Quéro (1984f); Haedrich & Merrett (1988); Wheeler (1992); Gordon et al. (1996); Ellis et al. (2005)



15 Galeus murinus Mouse catshark Occurs in the deep-water to the west of the British Isles, including the Rockall Trough and Porcupine Seabight

Quéro (1984f); Haedrich & Merrett (1988); Gordon et al. (1996); O'Hea et al. (2008); Neat et al. (2008)

16 Scyliorhinus canicula Lesser-spotted dogfish

Occurs on the continental shelf and upper slope all around the British Isles

Quéro (1984f); Wheeler (1992); Ellis et al. (2005)

17 Scyliorhinus stellaris Greater-spotted dogfish

May occur all around the British Isles, but most frequent along southern and western coasts, usually in waters <100 m deep

Quéro (1984f); Wheeler (1992); Ellis et al. (2005)

Pseudotriakidae 18 Pseudotriakis microdon

False catshark Deepwater species that is occasionally reported from off the continental slope to the west of the British Isles

Forster (1964; 1968); Quéro (1984g); Clarke et al. (2005)

Triakidae (subfamily Triakinae)

19 Mustelus asterias Starry smooth- hound

Occurs on the continental shelf all around the British Isles, but more abundant in southern and western areas

Branstetter (1984b); Wheeler (1992); Ellis et al. (2005)

20 Mustelus mustelus19 Smooth-hound

Is reported to occur around the British Isles, although its distribution in UK waters is uncertain, due to widespread confusion between this and the more common Mustelus asterias.

Branstetter (1984b); Wheeler (1992)

Triakidae (subfamily Galeorhininae)

21 Galeorhinus galeus Tope shark Occurs on the continental shelf and upper slope all around the British Isles

Branstetter (1984b); Wheeler (1992); Ellis et al. (2005)

Carcharhinidae – Carcharhinus longimanus

Oceanic white-tip shark

A tropical and sub-tropical oceanic species. Although there are no records from the British Isles, a single specimen was washed ashore in Sweden (George, 2009), and this specimen would have had to have passed in or near to UK waters to reach Sweden

Branstetter (1984a); George (2009)

– Carcharhinus obscurus Dusky shark A tropical and sub-tropical species. Although there are no records from the British Isles, a specimen was recorded in the northern Bay of Biscay (47°N, 5°50’W) by Quéro et al. (2001).

Branstetter (1984a); Quéro et al. (2001).

– Galeocerdo cuvier Tiger shark No authenticated records from the British Isles, although one unconfirmed sighting reported by Wheeler & Blacker (1972). A vagrant tiger shark was reported from Iceland (Jónsson, 1983).

Wheeler & Blacker (1972); Jónsson (1983); Branstetter (1984a);

22 Prionace glauca Blue shark Oceanic species that is a regular visitor to shelf seas along the southern and western coasts of the British Isles, and occasionally in the North Sea.

Branstetter (1984a); Wheeler (1992); Vas (1990)

19 Since undertaking this work, examination of more specimens from research vessel surveys, commercial landings and museum material indicate that this species may not occur in British waters, with authenticated specimens now only thought to have been reported from the Mediterranean Sea and the west coast of Africa.



Sphyrnidae 23 Sphyrna zygaena Smooth hammerhead

Very occasional vagrant that may occur in the south-west waters of the British Isles

Quéro (1984h). Southall & Sims (2005)

ORDER SQUALIFORMES

Dalatiidae 24 Dalatias licha Kitefin shark Occurs in the deep-water to the west of the British Isles, including the Rockall Trough and Porcupine Seabight

McEachran & Branstetter (1984); Haedrich & Merrett (1988); Wheeler (1992); Gordon et al. (1996);

Etmopteridae 25 Centroscyllium fabricii Black dogfish Occurs in the deep-water to the north and west of the British Isles, including the Rockall Trough

McEachran & Branstetter (1984); Haedrich & Merrett (1988); Gordon et al. (1996);

26 Etmopterus princeps Great lantern shark

Occurs in the deep-water to the west of the British Isles, including the Rockall Trough and Porcupine Seabight


27 Etmopterus spinax Velvet belly

Occurs in the deep-water around the British Isles, including the Rockall Trough and Porcupine Seabight, and occasionally found on the outer continetal shelf of the northern North Sea and Celtic Sea

McEachran & Branstetter (1984); Haedrich & Merrett (1988); Wheeler (1992); Gordon et al. (1996); Ellis et al. (2005)

Somnosidae 28 Centroscymnus coelolepis

Portuguese dogfish



29 Centroselachus crepidater

Longnose velvet dogfish

Reported (as Centroscymnus crepidater) Occurs in the deep-water to the west of the British Isles, including the Rockall Trough


– Scymnodon obscurus Smallmouth knifetooth dogfish

Currently viewed as a junior synonym of Zameus squamulosus

30 Scymnodon ringens Knifetooth dogfish



31 Somniosus microcephalus

Greenland shark Large-bodied northerly shark species that has been captured occasionally along the northern and western coasts of the British Isles and in the North Sea.

McEachran & Branstetter (1984); Wheeler (1992)

– Somniosus rostratus Lesser sleeper shark

Although typically reported from further south (e.g. off the Iberian peninsula), it has been reported from deep-waters off

McEachran & Branstetter (1984); Neat et al. (2008)



Scotland (Neat et al., 2008). The taxonomy of this genus is problematic and until further records are confirmed, its occurrence around the British Isles is questionable

– Zameus squamulosus Velvet dogfish

A deep-water species. Although purported to occur around the British Isles, sometimes as Scymnodon obscurus, (Compagno, 1984; George, 2009) there does not appear to be published accounts confirming its presence.

McEachran & Branstetter (1984); George (2009)

Oxynotidae 32 Oxynotus centrina Angular roughshark

Occasionally reported from deep waters to the south-west of the British Isles, but generally occurs further south

Quéro (1984i); Wheeler et al. (2004)

33 Oxynotus paradoxus Sailfin roughshark

Occasionally reported from deep waters to the west of the British Isles

Quéro (1984i); Wheeler (1992); Quigley & Flannery (1994)

Centrophoridae – Centrophorus granulosus

Gulper shark

Although recorded for the British Isles (Wheeler et al., 2004; Neat et al., 2008), the taxonomy of this genus is problematic, and many deep-sea studies have not reported this species. It is generally regarded to occur further south, up to the southern Bay of Biscay

McEachran & Branstetter (1984); Wheeler et al. (2004); Neat et al (2008)

34 Centrophorus squamosus

Leafscale gulper shark



35 Deania calcea Birdbeak dogfish Occurs in the deep-water to the west of the British Isles, including the Rockall Trough and Porcupine Seabight


36 Deania hystricosa Rough longnose dogfish

Reported (as D. mauli) from a deep-water trawl survey off south-west Ireland

Cappetta et al. (1985)

Squalidae20 37 Squalus acanthias Spurdog Widely distribution all around the British Isles Wheeler (1992); Ellis et al. (2005)

– Squalus blainvillei Longnose spurdog

This species is reported to occur in the Bay of Biscay, but there are no records from the British Isles and the northern limits of its geographic range in the NE Atlantic are unclear.

McEachran & Branstetter (1984);

20 Blacker (1962) reported on an elasmobranch that “resembles the common spurdog (Squalus acanthias L.), but differs in the larger eye, deeper body and shorter distance between the second dorsal and caudal fins. It may perhaps be the southern species S. fernandinus Molina, but certain identification must await the capture and preservation of another specimen”. It is unclear as to whether this specimen would refer to S. blainvillei or S. uyato.



38 Squalus uyato Little gulper shark

The taxonomy of this species is problematic, and for many years was reported as Centrophorus uyato. Many deep-sea studies have not reported this species. Although typically reported from further south (e.g. off the Iberian peninsula), it was reported from the Rockall trough (Clarke, 2000).

McEachran & Branstetter (1984); Clarke (2000)

Echinorhinidae 39 Echinorhinus brucus Bramble shark Unusual deep-water shark that has been reported sporadically to the west of the British Isles

Went (1978); McEachran & Branstetter (1984); Wheeler (1992);

ORDER SQUATINIFORMES

Squatinidae 40 Squatina squatina Angel shark Reported from many parts of the inner continental shelf of the British Isles, although most records from southern and western coasts

Roux (1984); Wheeler (1992); Rogers & Ellis (2000)

ORDER TOPEDINIFORMES

Torpedinidae 41 Torpedo (Tetronarce) nobiliana

Common electric ray

Occurs on the continental shelf and upper slope, although most frequently observed along south-western and western coasts

Stehmann & Bürkel (1984a); Wheeler (1992); Ellis et al. (2005)

42 Torpedo (Torpedo) marmorata

Marbled electric ray

Occurs in the English Channel, including occasionally in UK waters

Stehmann & Bürkel (1984a); Wheeler (1992); Ellis et al. (2005)

ORDER RAJIFORMES

Arhynchobatidae 43 Bathyraja pallida Pale ray Occasionally captured in deep water to the west of the British Isles

Stehmann & Bürkel (1984b); Clarke (2000); O'Hea et al. (2008)

44 Bathyraja richardsoni Richardson's ray Occurs in the deep-water to the west of the British Isles, including the Rockall Trough and Porcupine Seabight

Stehmann & Bürkel (1984b); Haedrich & Merrett (1988); Gordon et al. (1996); Clarke (2000)

45 Bathyraja spinicauda Spinytail ray Deepwater species that may occur off the continental shelf of the northern and western British Isles

Stehmann & Bürkel (1984b); Wheeler et al. (2004)

46 Bathyraja sp. A specimen of what appears to be an undescribed member of the genus Bathyraja was caught west of Scotland in waters of ca. 2000 m deep. The specimen was photographed but not retained

Quéro & Vayne (2001)

Rajidae 47 Amblyraja hyperborea Arctic skate This northerly species may occasionally occur in the deeper waters around the northern parts of the British Isles

Stehmann & Bürkel (1984b); Clarke (2000); Wheeler et al. (2004)



48 Amblyraja jenseni Jensen’s skate (or short-tail ray)

Occasionally captured in deep water to the west and north of the British Isles

Quéro et al. (2000); O'Hea et al. (2008)

49 Amblyraja radiata Starry ray Widespread in the central and northern North Sea. Also occurs off NW Scotland

Stehmann & Bürkel (1984b); Wheeler (1992); Ellis et al. (2005)

50 Dipturus batis (D. cf. flossada)

Common skate (or blue skate)

Known from the Rockall Bank and Celtic Sea. Thought to have been more widely distributed historically.

Stehmann & Bürkel (1984b); Ellis et al. (2005); Griffiths et al. (2010); Iglésias et al. (2010)

51 Dipturus cf. intermedia Flapper skate Known from the northern North Sea, NW Scotland and Celtic Sea, although not as frequent as D. batis in the latter area. Thought to have been more widely distributed historically.

Stehmann & Bürkel (1984b); Ellis et al. (2005); Griffiths et al. (2010) ; Iglésias et al. (2010)

– “Dipturus” linteus Sailray

Although no authenticated specimens from the British Isles, this northerly species occurs off the Faroes and in the north-eastern North Sea, and as such may occur in the deep waters off the Shetland Isles. Currently accepted as being in the genus Dipturus, but some suggestions that it should be included within the genus Malacoraja

Stehmann & Bürkel (1984b)

52 Dipturus nidarosiensis Norwegian skate Occurs in the deep-water to the west of the British Isles, including the Rockall Trough and Porcupine Seabight

Stehmann & Bürkel (1984b); Haedrich & Merrett (1988); Gordon et al. (1996);

53 Dipturus oxyrinchus Long-nose skate Occurs on the outer continental shelf and continental slope all around the British Isles

Stehmann & Bürkel (1984b); Wheeler (1992)

54 Leucoraja circularis Sandy ray Occurs on the outer continental shelf and continental slope all around the British Isles, typically in waters >100 m deep

Stehmann & Bürkel (1984b); Haedrich & Merrett (1988); Wheeler (1992); Ellis et al. (2005)

55 Leucoraja fullonica Shagreen ray Occurs on the outer continental shelf and continental slope all around the British Isles, and occasionally in the deeper waters of the Irish Sea.

Stehmann & Bürkel (1984b); Wheeler (1992); Ellis et al. (2002; 2005)

56 Leucoraja naevus Cuckoo ray

Widespread on the continental shelf of the British Isles, although most frequent along western coasts and the northern North Sea, and only occasionally observed in the southern North Sea and eastern English Channel




57 Malacoraja kreffti Krefft's ray Deep-water species that has been reported from the Rockall Trough

Stehmann & Bürkel (1984b); Stehmann (1993)

58 Malacoraja spinacidermis

Soft skate (or prickled skate)

Deep-water species that has been reported on the Iceland-Faroe Ridge and may occur to the north-west of the British Isles.

Stehmann & Bürkel (1984b); Quéro et al. (2000)

59 Neoraja caerulea Blue pygmy skate



60 Raja brachyura Blonde ray Widespread but patchily distributed on the continental shelf of the British Isles, but most common along southern and western coasts in waters <150 m deep


61 Raja clavata Thornback ray Widespread on the continental shelf of the British Isles, with areas of high abundance on inshore grounds (e.g. Outer Thames Estuary, Bristol Channel, Irish Sea)


62 Raja microocellata Small-eyed ray Common and abundant in the Bristol Channel and parts of the English Channel. Occasional specimens reported from the Irish Sea, Firth of Clyde and southern North Sea.


63 Raja montagui Spotted ray Widespread on the continental shelf of the British Isles Stehmann & Bürkel (1984b); Wheeler (1992); Ellis et al. (2005)

64 Raja undulata Undulate ray Locally common in parts of the English Channel, with very occasional specimens from the Bristol Channel. Also occurs in some Irish bays. Typically in waters <100 m deep.


65 Rajella bathyphila Deepwater ray Occurs in the deep-water to the west of the British Isles, including the Rockall Trough

Stehmann & Bürkel (1984b); Haedrich & Merrett (1988)

66 Rajella bigelowi Bigelow's ray Occurs in the deep-water to the west of the British Isles, including the Rockall Trough and Porcupine Seabight


67 Rajella kukujevi Mid-Atlantic skate

Originally described from the North Atlantic Ridge, but subsequently reported from deep waters off NW Europe, including in the Rockall Trough

Clarke (2000); Rodríguez-Cabello et al. (2012)

68 Rajella fyllae Round skate Occurs in the deep-water to the west of the British Isles, including the Rockall Trough and Porcupine Seabight

Stehmann & Bürkel (1984b); Haedrich & Merrett (1988); Wheeler (1992); Gordon et al. (1996);



69 Rostroraja alba White skate On the southern wand western coasts of the British Isles. Reported to be one of the main commercial species in the English Channel during the 1800s, but now rarely caught.


ORDER MYLIOBATIFORMES

Dasyatidae 70 Dasyatis pastinaca Common Stingray

Occurs in the inshore waters of the English Channel, Bristol Channel and southern North Sea, with occasional records from elsewhere in UK waters

McEachran & Capapé (1984a); Wheeler (1992); Ellis et al. (2005)

71 Pteroplatytrygon violacea

Pelagic stingray An oceanic species normally associated with tropical and sub-tropical waters. Individuals have been reported from the North Sea and from west of Ireland, but these are considered vagrants

McEachran & Capapé (1984a); Henderson et al. (1999); Ellis (2007)

Myliobatidae (subfamily Myliobatinae)

72 Myliobatis aquila Common eagle ray

Occasional vagrant to the southern and western parts of the British Isles

McEachran & Capapé (1984b); Wheeler (1992)

Myliobatidae (subfamily Mobulinae)

– Mobula mobular Devil ray One record of a stranded individual along the Irish coast from the ca. 1830 (O’Riordan, 1968) and has also been recorded from the south coast of Brittany (Quéro et al., 1996).

O’Riordan (1968); McEachran & Capapé (1984c); Wheeler (1992); Quéro et al. (1996).

CLASS HOLOCEPHALI; ORDER CHIMAERIFORMES

Chimaeridae 73 Chimaera monstrosa Rabbit fish

Occurs in the deep-water around the British Isles, including the Rockall Trough and Porcupine Seabight, and occasionally found on the outer continetal shelf of the northern North Sea and Celtic Sea

Stehmann & Bürkel (1984c); Haedrich & Merrett (1988); Wheeler (1992); Gordon et al. (1996); Ellis et al. (2005)

74 Chimaera opalescens Opal chimaera

A recently described species which has been confused with Chimaera monstrosa. Has been described from specimens collected from deep waters to the south of the British Isles, including the Porcupine Bank, Porcupine Seabight, Goban Spur, Great Sole Bank and Rockall Bank.

Luchetti et al., 2011

75 Hydrolagus affinis Small-eyed rabbitfish


Stehmann & Bürkel (1984c); Haedrich & Merrett (1988)

76 Hydrolagus mirabilis Large-eyed rabbitfish


Stehmann & Bürkel (1984c); Haedrich & Merrett (1988); Gordon et al. (1996);

77 Hydrolagus pallidus Pale chimaera Occurs in the deep-water to the west of the British Isles, including the Rockall Trough

Hardy & Stehmann (1990); Gordon et al. (1996);

Rhinochimaeridae 78 Harriotta haeckeli Smallspine spookfish

Some records of this species in the deep waters to the north-west of Ireland

Quéro et al. (2000)



79 Harriotta raleighana Longnose chimaera


Stehmann & Bürkel (1984d); Haedrich & Merrett (1988); Gordon et al. (1996);

80 Rhinochimaera atlantica

Straightnose rabbitfish


Stehmann & Bürkel (1984d); Haedrich & Merrett (1988); Gordon et al. (1996);


Sources:

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