Scientific, Technical and Economic Committee for Fisheries (STECF) : long-term management of skates and rays (STECF-17-21).
Date: 2018-01-19
Institutions: Joint Research Centre
Subjects: Community fisheries, conservation of fish stocks, data collection, environmental economics, evaluation of resources, fishery management, fishery research, fishing controls, research report

Scientific, Technical and Economic 
Committee for Fisheries (STECF) 
- 
Long-term management of skates 
and rays 
(STECF-17-21)

Edited by Michel Bertignac & Finlay Scott 

 EUR 28359 EN 

This  publication  is  a  Science  for  Policy  report  by  the  Joint  Research  Centre  (JRC),  the  European 
Commission’s science and knowledge service. It aims to provide evidence-based scientific support 
to  the  European  policy-making  process.  The  scientific  output  expressed  does  not  imply  a  policy 
position of the European Commission. Neither the European Commission nor any person acting on 
behalf of the Commission is responsible for the use which might be made of this publication. 

Contact information  

Name: STECF secretariat 

Address: Unit D.02 Water and Marine Resources, Via Enrico Fermi 2749, 21027 Ispra VA, Italy 

E-mail: stecf-secretariat@jrc.ec.europa.eu 

Tel.: +39 0332 789343 

JRC Science Hub 

https://ec.europa.eu/jrc 

JRC109366 

EUR 28359 EN 

PDF 

ISBN 978-92-79-67493-8 

ISSN 1831-9424

doi:10.2760/44133

STECF 

ISSN 2467-0715 

Luxembourg: Publications Office of the European Union, 2017 

© European Union, 2017 

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How  to  cite:  Scientific,  Technical  and  Economic  Committee  for  Fisheries  (STECF)  –  Long-term 
management  of  skates  and  rays  (STECF-17-21).  Publications  Office  of  the  European  Union, 
Luxembourg, 2017, ISBN 978-92-79-67493-8, doi:10.2760/44133, JRC109366

All images © European Union 2017 

Abstract 

Commission  Decision  of  25  February  2016  setting  up  a  Scientific,  Technical  and  Economic 

Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult 

the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries 

economics, fisheries governance, ecosystem effects of fisheries, aquaculture or similar disciplines. 

This report focusses on the long-term management of skates and rays.  

Authors: 

STECF advice: 

Ulrich, C.., Abella, J. A., Andersen, J., Arrizabalaga, H., Bailey, N., Bertignac, M., Borges, 
L.,  Cardinale,  M.,  Catchpole,  T.,  Curtis,  H.,  Daskalov,  G.,  Döring,  R.,  Gascuel,  D., 
Knittweis,  L.,    Lloret,  J.,  Malvarosa,  L.,  Martin,  P.,  Motova,  A.,  Murua,  H.,  Nord,  J., 
Prellezo,  R.,  Raid,  T.,  Sabatella,  E.,  Sala,  A.,  Scarcella,  G.,  Soldo,  A.,  Somarakis,  S., 
Stransky, C., van Hoof, L., Vanhee, W., van Oostenbrugge, Hans , Vrgoc, Nedo 

EWG-17-10 report:  

Bertignac,  M.,  Borges,  L.,  Clarke,  M.,  Ellis,  J.,  Figueiredo,  I.,  Gadenne,  H.,  Jung,  A., 
Rihan, D., Scott, F., Walker, P. 

3 

TABLE OF CONTENTS 

SCIENTIFIC, TECHNICAL AND ECONOMIC COMMITTEE FOR FISHERIES 

(STECF) - Long-term management of skates and rays (STECF-17-
21) ............................................................................................................................... 7

Request to the STECF ......................................................................................................... 7 

STECF response .................................................................................................................... 7 

STECF observations ............................................................................................................. 7 

STECF conclusions ............................................................................................................. 12 

References ............................................................................................................................ 13 

Contact details of STECF members ............................................................................. 13 

Expert Working Group  EWG-17-10 report .............................................................. 18 

1 

2 

2.1 

2.2 

2.3 

3 

3.1 

3.2 

EXECUTIVE SUMMARY ................................................................................................ 19 

INTRODUCTION ........................................................................................................... 22 

Background ............................................................................................................. 22 

Terms of Reference for EWG-17-10 ............................................................. 22 

Approach followed by EWG-17-10 ................................................................ 24 

FISHERIES CATCHING SKATES (RAJIDAE) IN THE ICES AREA ............................... 26 

Skates and rays in the north-east Atlantic ................................................ 26 

Commercial skate taxa ...................................................................................... 26 

3.2.1  Genus Dipturus ..................................................................................................... 26 

3.2.2  Genus Leucoraja ................................................................................................... 27 

3.2.3  Genus Raja ............................................................................................................. 27 

3.2.4  Other genera .......................................................................................................... 27 

3.3 

General overview of those métiers catching skates ............................... 33 

3.3.1  Inshore and coastal fleets ................................................................................ 33 

3.3.2  Offshore fleets ....................................................................................................... 33 

3.3.3  Deepwater fleets .................................................................................................. 34 

3.3.4  Miscellaneous fisheries and gears ................................................................. 34 

3.4 

Skates and their fisheries by area ................................................................. 36 

3.4.1  Skagerrak (Division 3.a) ................................................................................... 36 

3.4.2  North Sea (Divisions 4.a-c) .............................................................................. 36 

3.4.3  Eastern English Channel (Division 7.d) ....................................................... 37 

4 

3.4.4  Northwest Scotland (Divisions 6.a-b) .......................................................... 38 

3.4.5  West of Ireland (Divisions 7.b-c and 7.j-k) ............................................... 38 

3.4.6  Irish Sea, Bristol Channel and northern Celtic Sea (Divisions 7.a 

and 7.f-g) ................................................................................................................ 38 

3.4.7  Western English Channel and approaches (Division 7.e and 7.h) .... 39 

3.4.8  Bay of Biscay (Divisions 8.a-b, 8.d-e) ......................................................... 40 

3.4.9  Cantabrian Sea (Division 8.c) ......................................................................... 40 

3.4.10 Atlantic Iberian waters (Division 9.a) .......................................................... 41 

3.4.11 Azores (Division 10.a) ........................................................................................ 42 

3.5 

3.6 

4 

4.1 

4.2 

4.3 

Length distribution of skates in example fisheries ................................. 42 

Species composition of skates in commercial landings ........................ 48 

SURVIVAL.................................................................................................................... 51 

Background ............................................................................................................. 51 

Available information on survival rates of skates and rays ................ 51 

Data extrapolation to fleets segments/métiers/species not covered 
by the available studies ..................................................................................... 53 

4.4 

Conclusions ............................................................................................................. 54 

5 

5.1 

5.2 

5.3 

5.4 

5.5 

6 

SELECTIVITY ............................................................................................................... 55 

Sorting grids and By-catch Reduction Devices (BRDs) ......................... 55 

Escape panels ........................................................................................................ 56 

Trawl gear modifications ................................................................................... 56 

Gillnets and longlines ......................................................................................... 57 

Conclusions ............................................................................................................. 58 

MANAGEMENT MEASURE EVALUATIONS .................................................................... 58 

6.1 

TAC based management measures .............................................................. 58 

6.1.1  Information needed ............................................................................................. 59 

6.1.2  Pros and cons ........................................................................................................ 59 

6.2 

Landing trip limits ................................................................................................ 60 

6.2.1  Information needs ............................................................................................... 60 

6.2.2  Pros and cons ........................................................................................................ 60 

6.3 

Effort control .......................................................................................................... 60 

6.3.1  Information needs ............................................................................................... 61 

6.3.2  Pros and cons ........................................................................................................ 61 

5 

6.4 

Landing sizes ......................................................................................................... 61 

6.4.1  Information needed ............................................................................................. 62 

6.4.2  Pros and cons ........................................................................................................ 62 

6.5 

Gear selectivity ..................................................................................................... 63 

6.5.1  Information needed ............................................................................................. 63 

6.5.2  Pros and cons ........................................................................................................ 63 

6.6 

Spatio-temporal measures ............................................................................... 63 

6.6.1  Information needed ............................................................................................. 64 

6.6.2  Pros and cons ........................................................................................................ 64 

6.6.3  Practical examples ............................................................................................... 64 

6.7 

Prohibited species list ......................................................................................... 65 

6.7.1  Information needed ............................................................................................. 65 

6.7.2  Pros and cons ........................................................................................................ 65 

6.7.3  Practical application ............................................................................................ 66 

7 

7.1 

7.2 

7.3 

8 

9 

10 

11 

CONCLUSION WITH SOME GUIDANCE FOR NEXT STEPS ........................................... 71 

Management measure review ......................................................................... 71 

Data limitation and needs ................................................................................. 72 

Next steps ............................................................................................................... 72 

REFERENCES ............................................................................................................... 73 

APPENDIX ................................................................................................................... 79 

Contact details of EWG-17-10 participants ............................................... 80 

List of Background Documents ....................................................................... 83 

6 

SCIENTIFIC, TECHNICAL AND ECONOMIC COMMITTEE FOR FISHERIES (STECF) 
- Long-term management of skates and rays (STECF-17-21) 

Request to the STECF 

STECF  is  requested  to  review  the  report  of  the  STECF  Expert  Working  Group  meeting 
and  the  additional  information  received  from  the  Regional  Groups  after  the  EWG, 
evaluate the findings and make any appropriate comments and recommendations. 

STECF response 

Background for the STECF 17-10 

Skates and rays are currently managed under five regional TACs. Each is a general skate 
and ray TAC including several species. ICES (International Council for the Exploration of 
the Sea) used to publish generic skates and rays stock assessment scientific advice but 
increasing  scientific  knowledge  and  data  reporting  at  species  level  has  allowed  for  the 
provision  of  advice  at  a  more  detailed  level.  As  a  result,  TACs  in  each  region  include 
individual  stocks  which  may  have  very  different  stock  development  and  status  and 
different  advice  and  as  STECF  has  previously  noted,  “the  approach  of  setting  combine 
TACs (…) does not offer adequate protection for ray species that require reductions in F” 
(STECF, 2014). 

In  recent  years,  a number of  requests  for scientific  advice have been  issued by  the  EU 
regarding the management of European skate and ray stocks. This includes a request to 
ICES  in  2013  to  explore  alternative  management  measures,  to  list  the  associated  data 
needs and explore the state of knowledge on the fishing activity (ICES, 2013); a request 
to  STECF  in  2015  on  a  proposal  for an  alternative TAC  calculation  method  proposed  by 
France  (STECF,  2015);  and  a  request  to  ICES  in  2016  to review  proposal  of  an  in-year 
TAC  adjustment  in  division  7d  (ICES,  2016).  In  2016,  the  Commission  proposed  a 
change  to  skate  and  ray  TAC  management  for  2017,  with  several  new  sub-TACs  for 
different  species.  The  proposal  used  the  existing  "SRX"  quota  allocation  key,  applying 
the  relative  stability  shares  to  each  sub-TAC.  Feedback  from  stakeholders  and  Member 
States raised concerns that such an allocation did not reflect current fishing activity and 
the  distribution  of  species  within  the  management  area,  causing  significant  socio-
economic  impact  on  fishermen.  Thus  at  the  December  Fisheries  Council,  the  proposal 
reverted  back  to  the  2016  system  of  combined  skate  and  ray  quota  management,  but 
with  a  joint  statement  from  Member  States  and  the  Commission  to  further  explore 
alternative management options. 

In  March  2017,  the  Commission  received  advice  from  the  North-Western  Waters 
Advisory  Council  (NWWAC)  suggesting  several  alternative  management  measures  and 
requested  they  be  reviewed  by  STECF.  The  Commission  organised  a  seminar  with 
fishermen, scientists, national administrations and other stakeholders in May 2017. This 
meeting helped in the drafting of these terms of reference for EWG 17-10. 

STECF observations 

The working group was held in Brussels, Belgium, 16-20 October 2017. The meeting was 
attended by 10 experts in total, including 2 STECF members and 1 JRC expert.  

7 

Terms of Reference for EWG-17-10 

To  review  possible  management  options  and  recommend  a  new  approach  for  the 
sustainable management of skates and rays fisheries. 

The review and assessment of management options should consider; sustainability such 
as  MSY  proxies,  the  regional  approach  to  fisheries  management,  mixed  fisheries 
approach  to  catches  of  skates  and  rays  and  possible  "choke"  species,  socioeconomic 
impacts  and  the  practical  applicability  of  management  measures.  Practical  applicability 
would  include  the  consideration  of  relative  stability,  including  the  evaluation  of  historic 
landing data, ease of enforcement / control and the risk to increased misreporting. 

The Commission understands that many of the skate stocks concerned are data-limited 
and  does  not  expect  definitive  quantitative  simulations.  A  risk-based  approach  may  be 
more  suitable;  however  suggestions  and  analysis  by  STECF  should  include  information 
on how skates and rays can be fished and managed sustainably in accordance with the 
CFP  objectives  in  each  scenario,  with  suggestions  on  appropriate  safeguards  and 
monitoring techniques. 

Furthermore, the expert working group is requested to: 

a) Collect and analyse information available for those fleets/métiers involved in the catch 
of  skates  and  rays,  by  identifying  (i)  those  métiers  (or  higher  aggregation  levels) 
catching  skates,  (ii)  the  catch  composition  (species  and  length  composition)  of  the 
métiers,  and  (iii)  the  social  and  economic  dependence  of  the  métier  on  the  main  skate 
and  rays  species.  Provide  an  overview  of  the  current  scientific  knowledge  and  data 
availability regarding mixed-fisheries involved in the catch of skates and rays 

b)  Evaluate  the  usefulness  of  closed  areas/seasons  as  measures  for  controlling  fishing 
mortality  and/or  protecting  spawning  fish  and  reducing  mortality  on  juveniles  (survey 
data, scientific knowledge available in the literature). 

c)  Collate  and  review  the  results  of  research  on  selectivity  and  relevant  bycatch 
mitigation  measures  for  relevant  fishing  gears  (haul  time  etc.)  that  would  either  help 
avoid the catch of skates and rays, or that could increase their discard survival. Evaluate 
the  effect  of  the  most  relevant  technical  measures  affecting  the  selectivity  of  fishing 
gears. 

d)  Collate  and  review  information  on  the  survival  rates  of  skates  and  rays  (updating 
STECF  2014).  The  output  would  be  a  table  of  stocks  /  species  versus  métier  /fleet 
segment  for  each  sea  basin  or  TAC  unit.  This  exercise  should  consider  to  what  extent 
information  from  one  métier  /  fleet  could  be  extrapolated  to  other  fleets,  detailing  the 
criteria to do so. If this is not possible, then the working group is requested to conduct a 
gap analysis, detailing what information would be required to consider extrapolation and 
high  survivability  exemptions  across  all  species  of  skates  and  rays,  métiers  and  fleer 
segments per sea basin or TAC unit, whichever is more suitable. 

e)  Compare  the  relative  merits  (Pros  and  cons)  of  potential  alternative  management 
measures  proposed  in  the  attached  documentation  by  the  NWWAC  and  the  Dutch 
Elasmobranch Society, as well as the output of the 12 May Focus Group. These potential 
management  measures  can  be  considered  in  a  qualitative,  risk-based  framework  for 
each sea basin or TAC unit, based on expert opinion. DG MARE understands that no one 
measure will be perfect, so where possible, combinations of management measures that 
mitigate risks, should be suggested by the working group. 

STECF observes that the ToRs were very ambitious and broad ranging. The EWG made 
substantial  progress  towards delivering  all  ToRs but  was  not  able  to  recommend  a new 

8 

 
 
 
approach  for  the  sustainable  management  of  skates  and  rays  fisheries.  The  approach 
followed by the EWG 17-10 was to group the ToRs as follows: 

The first category, including ToR a, c and d, is presented as a compilation and review of 
available information related to i) the fleets and métiers involved in the capture of skates 
and rays, ii) the results of research on selectivity and bycatch mitigation measures and 
iii) the survival rates following discarding. 

ToR a Skate catch data 

The  EWG  presented  tables  indicating  the  occurrence  by  ICES  Division  of  32  species  of 
skates  (Rajiformes)  in  the  North-east  Atlantic  and  those  that  are,  or  have  been, 
exploited  commercially  in  northern  European  fisheries  (16  species).  Information  on  the 
interactions of different gears with skate species are summarised and the differences in 
these  interactions  between  inshore,  coastal  and  off-shore  fleets  described,  as  well  as 
specific skate fisheries by ICES area (ToR a.i). Data on the composition of skates caught 
in different fisheries and length frequencies in the full catch are presented but only for a 
few  examples  (ToR  a.ii).  STECF  observes  that  the  social  and  economic  dependence  of 
the métier on the main skate species could not be addressed (ToR a.iii).  

STECF  observes  there  is  no  single  dataset  that  can  provide  all  relevant  skate  fisheries 
data;  there  are  various  subsets  of  relevant  data  available,  however  the  data  sources 
used  by  EWG  17-10  are  not  clearly  described.  The  EWG  also  noted  that  the  ICES 
Working  Group  on  Elasmobranch  Fishes  (WGEF)  considers  that  some  ‘species-specific’ 
records held in official data are inaccurate, which can be due to a range of issues (e.g. 
coding errors, misidentifications, misreporting). STECF observes that there is consensus 
that  data  limitations  exist  for  skate  stocks,  but  the  nature  of  these  limitations  and  the 
stocks  to  which  they  apply  have  not  yet  been  defined.  For  example,  there  are  discard 
data available in the STECF FDI database that is not referred to in the ICES advice. 

ToR d) Skate discard survival 

EWG-17-10 collated and reviewed available  information  on the discard survival rates of 
skates. As requested, the EWG updated a table from STECF (2015) and presented seven 
studies  in  European  waters,  of  which  only  two  estimated  discard  survival.  The  other 
studies reported either vitality values or the percentage of individuals that survived after 
the observation period. 

STECF  observes  that,  while  it  was  useful  to  update  the  survival  study  table,  modifying 
the  table  to  include  an  assessment  of  the  quality  of  the  estimates  would  improve  its 
utility.  The  table  includes  a  column  ‘short-term’.  STECF  observes  that  the  phrases  of 
‘short-term’ and ‘long-term’ discard survival estimates can be misleading, consequently 
the  outputs  of  the  ICES  Workshop  on  Methods  to  Estimate  Discard  Survival  (WKMEDS) 
no  longer  use  these  terms.  There  are  two  methods  to  estimate  discard  survival,  i) 
deploying  tags  on  discarded  fish  and  retrieving  those  tags  to  determine  the  fate  of  the 
fish;  and  ii)  taking  fish  at  the  point  they  would  be  discarded,  holding  them  in  captivity 
and  recording  their  fate.  When  using  this  captive  observation  method,  it  is  necessary 
that  all  mortalities  associated  with  the  commercial  catch  and  sorting  process  are 
observed.  This  means  that  the  monitoring  period  has  to  be  sufficiently  long  to 
demonstrate  that  mortalities  have  stopped.  If  the  monitoring  period  is  too  short,  then 
the discard survival rates overestimate the true levels. But when applied correctly, both 
methods  generate  robust  discard  survival  estimates,  and  the  main  difference  between 
the  two  methods  is  that  when  using  tags,  the  discard  estimate  includes  the  effect  of 
predation, which is missing when using captive observation. 

9 

 
 
 
 
Therefore, some of the ‘short-term’ estimates presented may be robust discard survival 
rates  that  do  not  include  predation,  while  other  estimates  may  be  generated  from 
insufficient monitoring periods, but this cannot be determined from the table. Similarly, 
the EWG reports that none of the studies provide  long-term discard  survival estimates, 
however,  STECF  observes  that  one  study  using  DST  tags  deployed  on  thornback  rays 
(Raja  clavata)  was  based  on  data  collected  for  up  to  317  days  (Catchpole,  2017). 
Instead  of  short  and  long  term  estimates,  the  table  could  be  modified  in  the  future  to 
include  the  experimental  method  used  and  the  quality  of  the  study.  A  critical  review 
process  developed  by  WKMEDS  and  used  by  STECF  in  assessing  discard  survival 
evidence has previously been applied to the reported studies (Catchpole, 2017), and this 
includes  assessing  whether  all  mortalities  were  observed  when  using  the  captive 
observation method. 

Discard  survival  estimates  are  needed  to  support  requests  for  exemption  from  the 
landing  obligation.  STECF  observes  that  current  estimates  cover  a  limited  number  of 
métiers,  areas  and  species,  and  because  the  factors  that  influence  survival  are  poorly 
understood  extrapolation  across  species,  fisheries  and  areas  is  challenging.  The  EWG 
also recognised that it is important to further encourage good practice on fish handling 
when discarded alive. 

ToR c) Selectivity  

The EWG reports that gear-based technical measures for towed gears such as increased 
codend mesh sizes and square mesh panels are ineffective in increasing size selectivity 
for  skates  and  rays  because  their  large,  flattened  body  shape  prevents  escape  once 
inside  fishing  gears  (Ellis  et  al.,  2016).  However,  this  type  of  modification  can  improve 
the condition of skates and therefore their survival chances, by reducing the volume of 
catch in the codend (e.g. Enever et al., 2010). 

STECF observes that improvements in the selectivity of trawls for skates can be achieved 
through  modifications  which  utilise  the  difference  in  shape  and  size  of  skates  and 
behaviour compared with other species in the catch. The EWG divided these into sorting 
grids  and  By-catch  Reduction  Devices  (BRDs),  escape  panels  and  separator trawls,  and 
other  trawl  gear  modifications.  The  short  review  provided  by  the  EWG  demonstrated 
good potential for these modifications to reduce catches of skates and rays. 

The  EWG  reports  that  for  static  gears  and  long  line  fisheries,  the  options  for  reducing 
skate bycatch are limited, but there have been few studies to date. A number of possible 
modifications  were  given,  including  restricted  lengths  of  net,  limiting  soak  times, 
adjusting mesh size, hanging ratio and height of the net and modifying the thickness and 
colour of netting material for static nets and hook design for long lines.  

STECF  observes  that  reducing  skate  catches  is  often  not  a  specific  objective  of  gear 
trials,  and  observations  of  incidental  catches  of  skates  are  not  always  recorded,  and 
therefore  information  on  the  effect  on  skate  of  modified  gears  maybe  more  difficult  to 
find. Under a Landing Obligation choke species scenario, where the quota for skates and 
rays  is  limited,  there  is  likely  to  be  an  increase  in  interest  in  gear  modifications  that 
reduce skate catches. 

ToRs b and e) Management Measures 

The  second  group  of  ToRs,  including  ToR  (b)  and  (e),  is  presented  as  a  comparison  of 
the relative merits of potential alternative management measures. The EWG notes that 
because  no  analytical  stock  assessments  are  available,  there  is  no  means  for  a 
quantitative evaluation of management measures. It was decided to draw up a list of the 

10 

 
 
 
 
pros  and  cons  of  a  set  of  potential  management  measures  and  compare  them  using 
selected criteria. 

TAC options 

STECF  observes  that  four  methods  of  TAC  setting  were  considered:  general  skate  and 
rays  TACs  by  region  (status  quo),  general  TACs  with  sub-TACs  for  particular  stocks, 
TACs  by  genus  and  stock  based  TACs.  The  EWG  note  that  ICES  produces  advice  that 
allows the setting of landing TACs at stock level, but to set TACs on a catch basis, it will 
be  necessary  to  get  better  estimates  of  dead  discards.  Related  to  this,  the 
misidentification  at  species  level  and  uses  of  generic  categories  in  the  reporting  of 
landings and discard data also needs to be addressed. STECF observes that it would be 
useful  to  determine  the  level  of  confidence  in  the  landing  and  discard  data  for  the 
different stocks. 

The EWG noted that the control of fishing mortality by stock will be higher in the case of 
TACs set at stock level and lower in the case of TACs combining all species. The current 
general  skate  and  ray  TACs  may  not  offer  adequate  protection  for  stocks  that  require 
reductions  in  F  and  conversely,  may  limit  catch  opportunities  for  stocks  in  good 
condition.  The  EWG  also  report  that  incentives  to  misreport  are  likely  to  be  lower  for 
general TACs since the possibility of a TAC to become limited increases with the number 
of TACs – this has particular relevance in the context of the LO. However, while this true, 
STECF observes that the argument against splitting a TAC for a group of skate species to 
reduce  the  likelihood  of  reaching  a  choke  point  is  essentially  the  same  as  that  for 
grouping similar species to reduce the risk of choke, so this argument must be carefully 
considered. 

Landing trip limits 

This management measure would limit the quantities landed of selected species on a trip 
by  trip  basis.  STECF  observe  that  this  measure  was  considered  outside  a  quota  limit 
system, but recognise that total removals would need to be managed to control fishing 
mortality.  The  main  observation  was that  the utility  of  the  approach was  dependent  on 
the  species  demonstrating  good  survival  on  release  when  the  landing  threshold  is 
exceeded, and this evidence is currently limited.  

Spatio-temporal measures 

The  EWG  reports  that  spatio-temporal  measures  are  useful  only  where  they 
demonstrably control fishing mortality. These can be used to reduce mortality on stocks 
on  a  case-by-case  basis  and  may  be  complemented  by  other  generalised  management 
measures. STECF observes that the tables presented listing species by ICES area could 
be used to build an evidence map which could then be used to demonstrate where data 
are  sufficient  to  assess  different  management  options.  The  EWG  reports  that  the  areas 
likely  to  be  affected  by  spatio-temporal  measures  are  potentially  quite  large  with 
associated  effects  on  wider  fisheries.  STECF  observes  that,  in  terms  of  species 
identification, the spatial distribution of commercial catches of different species could be 
validated using survey data. 

Effort management 

The  EWG  conclude  that  effort  management  may  have  fewer  control  and  enforcement 
issues  compared  with  other  options.  However,  measuring  (and  limiting)  increase  in 
fishing efficiency is extremely difficult, which would undermine this approach. Moreover, 

11 

 
 
 
 
 
it  would  difficult  to  reconcile  effort  management  for  skates  caught  in  combination  with 
other species managed with quotas. 

Size restrictions 

Size  restrictions  of  landings  (minimum  and/or  maximum)  would  need  to  be  specific  to 
each  species.  The  EWG  noted  that  this  measure  would  be  in  contradiction  with  the 
landing obligation if implemented in association with catch limits, unless exemptions on 
the basis of high survival are in place. 

Prohibited species 

The  EWG  states  that  the  prohibited  species  list  should  be  used  for  species  which  are 
biologically sensitive to any exploitation. STECF observe also that “Prohibited species” by 
their  nature  are  sensitive  species,  mostly  CITES  listed,  where  even  limited  fishing 
activity  could  result  in  a  serious  risk  to  their  conservation.  There  is  currently  no 
procedure  on  which  to base  decisions  to  include  or  exclude species  from  the  prohibited 
list  in  the  TACs  and  quota  regulations.  Moreover,  the  benefits  of  classifying  species  as 
prohibited  are  unknown  without  more  information  of  the  discard  survival  of  incidental 
catches, and do not necessarily lead to a decrease in mortality. 

STECF conclusions 

STECF  acknowledges  that  the  general  skate  and  ray  TACs  may  not  offer  adequate 
protection  for  stocks  that  require  reductions  in  F  and  conversely,  may  limit  catch 
opportunities  for  stocks  in  good  condition.  There  are  also  potential  impacts  on  skates 
and rays management when the landing obligation is applied from 1 January 2019. 

STECF acknowledges that data limitations exist for skate and ray stocks, and concludes 
that the nature of these limitations and the stocks to which they apply need to be better 
identified.  STECF  highlights  that  the  main  impediment  to  setting  more  specific  TACs  is 
the lack of evidence in terms of total catch (landings + dead discards). Similarly, more 
detailed  catch  information  is  needed  to  assess  the  utility  of  spatio-temporal,  effort  and 
other management measures.  

STECF  acknowledges  the  progresses  achieved  by  ICES,  which  produced  advice  for  33 
stocks  of  skates  and  rays  in  2017.  However,  in  most  of  these  cases  the  absence  of 
discard data prohibits catch advice. STECF concludes that emphasis should be given on 
utilising  what  discard  information  and  survival  information  is  available,  applying  the 
same  protocols  as  with  other  stocks.  This  will  identify  those  stocks  for  which  data  are 
sufficient to assess management options. STECF considers that this work is of sufficient 
scale  to  warrant  a  follow-up  EWG  that  would  focus  on  collating  stock  specific  discard 
information and use survey data as a validation for species identification. Socioeconomic 
considerations could also be included.. 

STECF  observes  additionally  that,  assuming  the  approach  used  in  recent  years  for 
implementing the Landing Obligation continues, any available discard data will be utilised 
as  part  of  the  TAC  adjustment  process  when  skates  and  ray  stocks  come  under  the 
Landing Obligation in 2019. 

STECF  concludes  that  when  reporting  on  survival  studies  it  is  preferable  to  include  the 
method  applied  and  an  assessment  of  the  quality  of  the  estimates  using  the  critical 
review process developed by ICES WKMEDS. STECF concludes that evidence on discard 
survival of skates and rays is limited to a few métier-area-species combinations. Because 

12 

 
 
 
 
 
 
the  factors  that  influence  survival  are  poorly  understood,  extrapolation  across  species, 
fisheries and areas is difficult, and more practical studies to estimate discard survival of 
skates and rays for key fisheries are needed.  

STECF  concludes that  there  is  potential  to  improve selectivity  towards  skates and  rays. 
To  date,  there  are  only  few  trials  in  European  fisheries  which  have  focussed  on 
improving  gear  selectivity  towards  skates  and  rays,  however,  the  incentive  to  avoid 
catches  of  skates  and  rays  may  increase  with  the  implementation  of  the  Landing 
Obligation. 

STECF  concludes  that  the  development  of  transparent  criteria  is  needed  to  classify 
species as prohibited in the TACs and quota regulations. 

References 

Tom  Catchpole,  Serena  Wright,  Victoria  Bendall,  Stuart  Hetherington,  Peter  Randall, 
Elizabeth  Ross,  Ana  Ribiero  Santos,  Jim  Ellis,  Jochen  Depestele  (ILVO),  Suzanna 
Neville  (2017).  Ray  Discard  Survival.  Enhancing  evidence  of  the  discard  survival  of 
ray species. Lowestoft: CEFAS. 

ICES (2013). Report of the ICES Advisory Committee 2013. ICES Advice, 2013. Book 11. 

31 pp. 

ICES  (2016)  Request  from  EU  for  ICES  to  review  a  proposal  of  an  in-year  TAC 
adjustment  for  2016  for  skates  and  rays  (SRX)  in  Division  7.d.  ICES  Technical 
Services 2016, Book 11. 13p. 

STECF  (2015).  Scientific,  Technical  and  Economic  Committee  for  Fisheries  (STECF)  – 
48th  Plenary  Meeting  Report  (PLEN-15-01).  2015.  Publications  Office  of  the 
European Union, Luxembourg, EUR XXXX EN, JRC XXXX, 75 pp. 

Contact details of STECF members 

1 - Information on STECF members’ affiliations is displayed for information only. In any 
case, Members of the STECF shall act independently. In the context of the STECF work, 
the committee members do not represent the institutions/bodies they are affiliated to in 
their  daily  jobs.  STECF  members  also  declare  at  each  meeting  of  the  STECF  and  of  its 
Expert  Working  Groups  any  specific  interest  which  might  be  considered  prejudicial  to 
their  independence  in  relation  to  specific  items  on  the  agenda.  These  declarations  are 
displayed on the public meeting’s website if experts explicitly authorized the JRC to do so 
in  accordance  with  EU  legislation  on  the  protection  of  personnel  data.  For  more 
information: http://stecf.jrc.ec.europa.eu/adm-declarations 

Name 

Address1 

STECF members 

Tel. 

Email 

Abella, 
Alvaro 

J. 

Independent consultant 

Tel. 
3384989821 

0039-

aabellafisheries@gmail.c
om 

13 

 
 
 
 
 
 
Name 

Address1 

STECF members 

Andersen, 
Jesper Levring  

Arrizabalaga, 
Haritz 

Bailey, 
Nicholas  

Bertignac, 
Michel  

for  Environment 

Department  of  Food  and 
Resource 
Economics 
(IFRO) 
Section 
and Natural Resources 
University of Copenhagen 
Rolighedsvej 25 
1958 Frederiksberg 
Denmark 

Marina, 

AZTI / Unidad de 
Investigación 
Herrera 
kaia  portualdea  z/g  20110 
Pasaia 
(Gipuzkoa), Spain 

Marine  Scotland  Science, 
Marine  Laboratory,  P.O 
Box 101  
375 Victoria Road, Torry 
Aberdeen AB11 9DB  
UK 

Laboratoire  de  Biologie 
Halieutique 
IFREMER Centre de Brest 
BP  70  -  29280  Plouzane, 
France  

Tel. 

Email 

Tel.dir.:    +45  35 
33 68 92 

jla@ifro.ku.dk 

Tel.: 
+34667174477 

harri@azti.es 

Tel:  +44  (0)1224 
876544  
Direct: 
(0)1224 295398  
Fax:  +44  (0)1224 
295511 

+44 

tel  :  +33  (0)2  98 
22  45  25  -  fax  : 
+33 (0)2 98 22 46 
53  

baileyn@marlab.ac.uk   
n.bailey@marlab.ac.uk 

michel.bertignac@ifreme
r.fr 

Borges, Lisa 

FishFix, Brussels, Belgium 

info@fishfix.eu 

Cardinale, 
Massimiliano 
(vice-chair) 

Catchpole, 
Thomas 

Curtis, Hazel  

Daskalov, 
Georgi 

Föreningsgatan  45,    330 
Lysekil, Sweden 

Tel:  +46 
18750 

523 

massimiliano.cardinale@
slu.se 

Lowestoft 

thomas.catchpole@cefas
.co.uk  

CEFAS 
Laboratory, 
Pakefield Road, 
Lowestoft 
Suffolk, UK 
NR33 0HT 

Sea Fish Industry Authority 
18 Logie Mill 
Logie Green Road 
Edinburgh 
EH7 4HS, U.K. 

Tel:  +44  (0)131 
524 8664 
Fax:  +44  (0)131 
558 1442 

Hazel.curtis@seafish.co.
uk 

Tel.:  +359 
646892 

52 

Georgi.daskalov@gmail.
com 

of 

Marine 

Laboratory 
Ecology, 
Institute  of  Biodiversity 
and 
Ecosystem 
Bulgarian 
Academy of Sciences 

Research, 

14 

 
 
 
 
 
 
 
 
 
Name 

Address1 

STECF members 

Tel. 

Email 

Döring, 
(vice-chair) 

Ralf 

Thünen 
Bundesforschungsinstitut, 
für  Ländliche  Räume,  Wald 
und  Fischerei,  Institut  für 
Seefischerei 
AG 
- 
Fischereiökonomie, 
Palmaille 
Hamburg, Germany 

D-22767 

9, 

Gascuel, Didier   AGROCAMPUS OUEST 

65 Route de Saint Brieuc, 
CS 84215, 
F-35042 RENNES Cedex 
France 

Department of Biology 
University of Malta 
Msida, MSD 2080 
Malta 

Professor 
Associate 
Agregat), 
(Professor 
University of Girona (UdG), 
Spain 

Fishery 

NISEA, 
and 
Aquaculture  Research,  Via 
Irno,  11,  84135  Salerno, 
Italy 

Knittweis, 
Leyla 

Lloret, Josep 

Malvarosa, 
Loretta  

Tel.:  040  38905-
185 

Fax.:  040  38905-
263 

Tel:+33(0)2.23.48
.55.34 
Fax: 
+33(0)2.23.48.55.
35 

ralf.doering@thuenen.de 

Didier.Gascuel@agroca
mpus-ouest.fr 

Leyla.knittweis@um.edu
.mt  

josep.lloret@udg.edu 

Tel: 
089795775 

+39 

malvarosa@nisea.eu 

Martin, Paloma    CSIC  Instituto  de  Ciencias 
del Mar  
Passeig Marítim, 37-49 
08003 Barcelona 
Spain 

Tel: 4.93.2309500 
Fax: 
34.93.2309555 

paloma@icm.csic.es 

Motova, Arina 

Murua, Hilario 

Nord, Jenny  

Prellezo, Raúl  

Sea Fish Industry Authority 
18 Logie Mill 
Logie Green Road 
Edinburgh 
EH7 4HS, U.K 

Marina, 

AZTI / Unidad de 
Investigación 
Herrera 
kaia  portualdea  z/g  20110 
Pasaia 
(Gipuzkoa), Spain 

The  Swedish  Agency  of 
Marine 
Water 
and 
Management (SwAM)  

Tel.:  +44  131  524 
8662 

arina.motova@seafish.c
o.uk 

0034 

Tel: 
667174433 
Fax: 94 6572555 

hmurua@azti.es 

Tel.  0046  76  140 
140 3 

Jenny.nord@havochvatt
en.se 

de 

Tel: 
667174368 

+34 

rprellezo@azti.es 

-Unidad 

AZTI 
Investigación Marina 
Txatxarramendi 
z/g 
48395 
(Bizkaia), Spain 

Ugartea 

Sukarrieta 

15 

 
 
 
 
 
 
 
 
 
 
 
Name 

Address1 

STECF members 

Tel. 

Email 

Raid, Tiit 

Estonian  Marine  Institute, 
University 
Tartu, 
Mäealuse  14,  Tallin,  EE-
126, Estonia 

of 

Tel.: 
58339340 
Fax: 
6718900 

+372 

Tiit.raid@gmail.com  

+372 

Sabatella, 
Evelina 
Carmen 

Fishery 

NISEA, 
and 
Aquaculture  Research,  Via 
Irno,  11,  84135  Salerno, 
Italy  

TEL.: 
089795775 

+39 

e.sabatella@nisea.eu  

Sala, Antonello 

Italian  National  Research 
Council (CNR) 
Institute 
Marine 
of 
Sciences  (ISMAR),  Largo 
Fiera della Pesca, 1 
60125 Ancona - Italy 

Tel:  +39 
2078841 
Fax:  +39 
55313 
Mob.: 
3283070446 

071 

a.sala@ismar.cnr.it 

071 

+39 

Scarcella, 
Giuseppe 

Soldo, Alen 

Somarakis, 
Stylianos 

Stransky, 
Christoph 

Ulrich, 
(chair) 

Clara 

Italian 

1) 
National 
Research  Council  (CNR), 
Marine 
of 
Institute 
- 
(ISMAR) 
Sciences 
Fisheries  Section,  Largo 
Fiera della Pesca, 1, 60125 
Ancona – Italy 
2) 
Marine  
Environmental  Consultancy 
Ltd,  2,  ACROPOLEOS  ST. 
AGLANJIA, P.O.BOX 26728 
1647 Nicosia, Cyprus 

AP 

of  Marine 
Department 
Studies, University of Split, 
Livanjska  5,  21000  Split, 
Croatia 

Institute 
Marine 
of 
Biological  Resources  and 
Inland  Waters  (IMBRIW), 
Hellenic  Centre  of  Marine 
Research 
(HCMR), 
Thalassocosmos  Gournes, 
P.O.  Box  2214,  Heraklion 
71003, Crete, Greece 

Thünen  Institute  [TI-SF] 
Federal  Research  Institute 
for  Rural  Areas,  Forestry 
and  Fisheries,  Institute  of 
Sea  Fisheries,  Palmaille  9, 
D-22767 
Hamburg, 
Germany  

of 
Technical  University 
National 
Denmark, 
Institute 
Aquatic 
of 
Resources,  (DTU  Aqua), 
Charlottenlund 
Slot, 
JægersborgAllé  1,  2920 
Charlottenlund, Denmark 

Tel:  +39 
2078846 
Fax:  +39 
55313 
Tel.: 
99664694 

071 

g.scarcella@ismar.cnr.it 

071 

+357 

gscarcella@apmarine.co
m.cy 

Tel.: 
+385914433906 

soldo@unist.hr  

Tel.:  +30  2810 
337832 

somarak@hcmr. gr 

Fax 
6936566764 

+30 

Tel. 
+49 
38905-228  
+49 
Fax: 
38905-263  

40 

40 

christoph.stransky@thue
nen.de 

clu@aqua.dtu.dk 

van Hoof, Luc 

IMARES,  Haringkade  1, 
Ijmuiden, The Netherlands 

Tel.: 
61061991 

+31 

Luc.vanhoof@wur.nl 

16 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
Name 

Address1 

STECF members 

Tel. 

Email 

Vanhee, Willy  

Independent consultant 

wvanhee@telenet.be 

van 
Oostenbrugge, 
Hans 

Vrgoc, Nedo 

Fisheries 
Wageningen 
Research, 
Wageningen 
Hague, The Netherlands 

Economics, 
Economic 
LEI 
The 

formerly 

UR, 

Hans.vanOostenbrugge
@wur.nl 

Institute  of  Oceanography 
and 
Split, 
Fisheries, 
Setaliste  Ivana  Mestrovica 
63, 21000 Split, Croatia 

Tel.: 
21408002 

+385 

vrgoc@izor.hr 

17 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
EXPERT WORKING GROUP  EWG-17-10 REPORT 

REPORT TO THE STECF 

EXPERT WORKING GROUP ON  
Long-term management of skates and rays 
(EWG-17-10) 

Brussels, Belgium, 16-20 October 2017 

This report does not necessarily reflect the view of the STECF 
and the European Commission and in no way anticipates the 
Commission’s future policy in this area 

18 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 

EXECUTIVE SUMMARY 

Skates and rays are currently managed under five regional TACs. Each of those TACs is a 
generalized  skates  and  rays  TAC  including  several  species  that  are  fished  and  caught 
within  this  TAC.  Historically,  ICES  used  to  publish  generic  advice  for  skates  and  rays. 
Increased  scientific  knowledge  of  the  distribution  and  range  of  various  species  and 
improved  species  identification  and  catch  reporting  has  allowed  for  the  provision  of 
advice  at  a  stock  level.  In  recent  years,  several  requests  were  made  to  the  STECF  to 
evaluate possible  management approaches and changes to TAC calculation (e.g. STECF 
15-01). In March 2017, the Commission received advice from the North-Western Waters 
Advisory  Council  (NWWAC)  suggesting  several  alternative  management  measures  and 
requested they be reviewed by STECF. 

EWG 17-10 has carried out a general overview of the fisheries catching skates and rays, 
presenting their main characteristics in terms of catches, métiers and fleet interactions. 
This  overview  highlights  some  of  the  key  features  of  the  biology  and  exploitation  of 
skates  and  rays  that  may  be  important  to  take  into  consideration  when  developing 
life  history  traits  and  distribution,  mixed-fishery 
management  measures  (e.g. 
interactions). 

A review of available studies on selective gears has been carried out both for towed and 
static gears, and a list of available references has been provided. This review shows that 
it  is  difficult  to  increase  size  selectivity  for  skates  and  rays  due  to  their  morphology. 
There  are  a  number  of  gear  modifications  however,  that  have  been  shown  to  be 
potentially  effective  at  reducing  bycatch,  (i.e.  reducing  the  catch  of  skates  and  rays 
across the whole size range).   

EWG-17-10 updated a list of survival rate estimates compiled by STECF (STECF, 2014), 
with recent published studies and information: survival rates are now provided at species 
level, and information on some of the important factors affecting survival is also given. 
EWG-17-10  notes  that  the  estimates  available  cover  only  a  limited  number  of  métiers, 
areas  and  species.  Furthermore,  several  of  the  available  estimates  are  limited  to  short 
term survival rates and longer-term survival is still uncertain (large confidence intervals 
or  very  different  estimates  for the  same  species between  different  experiments).  EWG-
17-10  considers  it  would  be  premature  to  envisage  any  extrapolation  of  survival  rates 
estimates  across  métiers.  To  both  increase  the  coverage  of  gear,  area and  species  and 
improve current estimates, EWG-17-10 considers that the model developed by Catchpole 
et al. (2017) for UK waters could be extended to other areas. Such a review should also 
highlight  the  main  information  gaps  by  species/métier  where  particular  data  collection 
and/or further analysis are needed. 

EWG  17-10  has  reviewed  a  series  of  measures  potentially  applicable  for  the 
management  of  skates  and  rays  proposed  by  the  NWWAC.  The  advantages  and 
disadvantages of each measure in the context of fisheries catching skates and rays have 
been  highlighted  and  the  main  data  needed  to  implement,  assess  and  monitor  the 
measures  have  been  listed.  The  different  management  measures  have  been  reviewed 
independently, even though for some measures, some stocks, fisheries and/or areas,  a 
combination of measures could potentially be more appropriate. EWG-17-10 considered 
that  where  a  combination  of  measures  is  appropriate,  they  should  be  tailored  to  the 
specific needs and issues associated to the particular stocks or fisheries.  

EWG-17-10  considered  that,  among  the  TAC  based  approaches  reviewed  by  the  group, 
the TAC by stock is the only one that permits the setting of limits on catches by stocks in 

19 

 
 
 
 
line  with  individual  stock  development  and  the  catch  levels  recommended  by  ICES.  All 
other  options  would  retain,  to  varying  degrees,  the  problem  of  the  current  global  TACs 
(e.g.  limiting  fishing  opportunity  for  stocks  for  which  the  abundance  is  increasing,  and 
insufficient protection for decreasing stocks or stocks of unknown status). 

EWG-17-10  notes  however  that  TACs  set  by  stock  may  be  compromised  by  species 
identification  issues.  TACs  by  stock  could  also  create  additional  choke  issues  under  the 
landing obligation over and above the other TAC options. In any case, it must be noted 
that  adding  more  TACs  (going  from  a  generalized  TAC  system  to  a  stock  based  TAC) 
may add extra monitoring requirements. Finally, the main impediment to any TAC based 
measure is lack of advice on outtake in terms of total catch (landings + dead discards). 
Currently,  ICES  only  provides  landings  advice.  Including  discard  information  requires 
quantification of discards and survival of these discards. More work is required in these 
areas. 

Regarding the spatio-temporal measures, EWG-17-10 considers that they could be used 
to  reduce  mortality  on  stocks  on  a  case-by-case  basis  and  may  be  complemented  by 
other  generalised  management  measures.  Theoretical  modelling  work  has  been  done 
and  provides  a  firm  analytical  basis.  In  this  context,  size,  location  and  timing  of 
management  measures  can  be  developed  in  a  participatory  decision-making  process. 
The  areas  to  be  closed  are  likely  to  be  quite  large  which  could  potentially  impact  the 
general fishery. The difficulties in reaching agreement of managers and stakeholders for 
such large closures should not be underestimated. 

Effort  management  may  have  fewer  control  and  enforcement  issues  as  compared  to 
other  options  but  measuring  (and  limiting)  increase  in  fishing  efficiency  is  extremely 
difficult,  which  possibly  renders  this  measure  ineffective  in  many  fisheries.  There  may 
also  be  potential  management  conflicts  in  mixed  fisheries  where  skates  and  rays  are 
managed by effort while the other species are managed by TACs. 

From  the  review  carried  out  by  EWG-17-10,  it  is  clear  that  the  underlying  data  for 
developing  management  options  based  on  gear  selectivity  is  currently  limited.  Current 
studies indicate that it is difficult to increase size selectivity for skates and rays but there 
are  a  number  of  gear  modifications  that  have  been  shown  to  be  effective  at  reducing 
bycatch (by reducing the catch over the whole size range). The adoption of such gears is 
dependent on whether the skate and ray species involved have a commercial value and 
the  availability  of  fishing  opportunities  that  allows  them  to  be  landed.  Where  such 
species  are  considered  as  part  of  the  marketable  catch,  then  there  is  little  incentive  to 
reduce  bycatch  as  to  do  so  would  represent  a  loss  of  income.  However,  in  a  choke 
species scenario, where the quota for skates and rays is exhausted and the only option 
for a vessel to continue fishing in a specific fishery is to fish without catching skates and 
rays then such gears may be considered an option.  

Size  restrictions,  either  minimum,  maximum  or  a  combination  should  be  tailored  to 
species  to  be  most  effective.  This  management  measure  would  however  be  in 
contradiction with the landing obligation if implemented in association with catch limits, 
except  for  species  for  which  an  exemption  for  high  survival  is  granted.  It  may  also  be 
difficult to receive buy-in from fishers of limits set on maximum sizes as generally, larger 
rays have the highest commercial value.  

The prohibited species list should ideally be used  only for species which are biologically 
sensitive to any exploitation. Without additional measures to improve survival, listing will 
not  necessarily  lead  to  a  decrease  in  mortality  and  may  simply  be  a  source  of 
unaccounted mortality from the discarding of dead skates and rays and for which there 
is no requirement to report. The decision to include, or remove, any species onto or off 
the  prohibited  species  list  is  currently  not  carried  out  according  to  transparent  criteria. 
EWG-17-10  suggests  to  develop  a  procedure  for  listing  and  to  develop  transparent 
criteria in a participatory process. 

20 

 
 
Concerning  data  limitations  and  needs,  EWG-17-10  notes  that  the  current  data 
requirement  and  sampling  effort  of  the  DCMap  on  skates  and  rays  is  insufficient  to 
provide  robust  estimates  of  various  parameters  (e.g.  maturity,  commercial  catch 
composition,  sex-ratio  and  abundance  indices)  needed  for  stock  assessment  and 
management.  Increasing  needs  on  information  on  catches  and  fisheries  may  imply 
adjustments of the DCMap for the data collection for skates and rays.  

The most crucial data gaps at the current time are discard survival (vitality and at-vessel 
mortality, and short- and longer term discard survival) and estimates of (dead) discards. 
These topics should have the highest priority. Further data and knowledge issues which 
require  attention  are:  improved  delineation  of  biological  stock  units,  more  robust 
estimates of stock status and development of MSY reference points or proxies. Those are 
key elements needed to be able to quantitatively evaluate the performances and impacts 
(biological, socio-economical) of various management measures.  

In  conclusion,  EWG-17-10  has  completed  an  initial  review  of  potential  management 
measures  applicable  to  skates  and  rays.  Due  to  the  diversity  of  species  in  terms  of 
biological  characteristic,  complexity  of  fisheries  catching  them  and  data  limitations,  it 
was  not  possible  to  fully  and  quantitatively  evaluate  any  particular  management 
measures or group of measures and further work is needed. EWG-17-10 considers that a 
way  forward  could  be  for  managers  and  relevant  stakeholders  to  first  decide  on  the 
objectives  of  potential  management  measures  (and  the  scope  in  terms  of  species  and 
areas,  and  governance  framework).  It  is  only  once  these  have  been  identified  that  a 
subsequent  scientific  evaluation  by  STECF  may  be  possible.  Although  a  combination  of 
management  measures  might  be  the  best  option,  in  some  cases  EWG-17-10  considers 
important  to  avoid  developing  too  complex  frameworks  which  may  be  difficult  to 
implement,  control  and  monitor  and  may  generate  low  levels  of  compliance  and  buy-in 
by fishers. 

21 

 
 
 
 
2 

INTRODUCTION 

2.1 

Background 

Skates  and  rays  are  currently  managed  under  five  regional  TACs.  Although  each  is  a 
generalized  skates  and  rays  TAC, the  reality  is  that  there  are  multiple  different  species 
that  are  fished  and  caught  within  this  TAC.  Historically,  ICES  (International  Council  for 
the Exploration of the Sea) used to publish generic advice for skates and rays. Increased 
scientific knowledge of the distribution and range of various species, has allowed for the 
provision  of  advice  at  a  more  detailed  level.  Advice  is  biennial,  with  Celtic  Sea  and 
Biscay-Iberian stocks having updated advice in 2016, whilst the advice for North Sea and 
Azorean stocks was published in 2015. New advice for 2017 was released on October 6th. 
Although  ICES  is  publishing  more  detailed  advice  on  individual  skates  and  rays  stocks, 
some are still considered data-limited stocks. There are also potential impacts on skates 
and  rays  management  when  the  landing  obligation  is  applied  to  mixed  fisheries  from  1 
January 2019. 

Skates  and  rays  are  caught  in  both  targeted  fisheries  and  as  a  by-catch  in  multiple 
fisheries and are important species for many Member States. As such, there have been 
previous  requests  to  the  STECF  to  evaluate  possible  management  approaches  and 
changes to TAC calculation (STECF 15-01), as well as on a specific bycatch provision for 
undulate ray (Raja undulata) (STECF 15-03). 

In  2016  the  Commission  proposed  a  change  to  skates  and  rays  TAC  management  for 
2017, with several new sub-TACs proposed for different species. The proposal used the 
existing  "SRX"  quota  allocation  key,  applying  the  same  sharing  mechanism  to  the 
individual  sub  TACs.    Feedback  from  stakeholders  and  Member  States  raised  concerns 
that  such  an  allocation  did  not  reflect  current  fishing  activity  and  the  overlap  between 
regional  fisheries  and  the  distribution  of  species  within  the  management  area,  and  so 
would create significant socio-economic impacts on fishermen and not provide any extra 
protection  for  sensitive  species.  Therefore,  at  the  December  Fisheries  Council,  it  was 
agreed by Member States to revert back to the 2016 TACs with a joint declaration from 
Member  States  and  the  Commission  to  further  explore  skates  and  rays  quota 
management.   

On the 24 March 2017, the Commission received advice from the North-Western Waters 
Advisory  Council  (NWWAC)  suggesting  several  alternative  management  measures  and 
requested they be reviewed by STECF. 

Recognising this positive initiative by the NWWAC, the Commission sought to investigate 
the  suitability  and  applicability  of  these  measures  to  other  sea  basins,  such  as  South-
Western  Waters  and  the  North  Sea.  The  Commission  organised  a  focus  group  and 
seminar  with  fishermen,  scientists,  national  administrations  and  other  stakeholders  on 
the  12  May  2017  in  Brussels.  This  meeting  helped  in  the  drafting  of  these  terms  of 
reference for EWG 17-10.  

2.2 

Terms of Reference for EWG-17-10 

To  review  possible  management  options  and  recommend  a  new  approach  for  the 
sustainable management of skates and rays fisheries. 

22 

 
 
 
 
 
 
 
 
 
 
The review and assessment of management options should consider; sustainability such 
as  MSY  proxies,  the  regional  approach  to  fisheries  management,  mixed  fisheries 
approach  to  catches  of  skates  and  rays  and  possible  "choke"  species,  socioeconomic 
impacts  and  the  practical  applicability  of  management  measures.  Practical  applicability 
would  include  the  consideration  of  relative  stability,  including  the  evaluation  of  historic 
landing data, ease of enforcement / control and the risk to increased misreporting. 

The Commission understands that many of the skate stocks concerned are data-limited 
and  does  not  expect  definitive  quantitative  simulations.  A  risk-based  approach  may  be 
more  suitable;  however  suggestions  and  analysis  by  STECF  should  include  information 
on how skates and rays can be fished and managed sustainably in accordance with the 
CFP  objectives  in  each  scenario,  with  suggestions  on  appropriate  safeguards  and 
monitoring techniques. 

Furthermore, the expert working group is requested to: 

a) Collect and analyse information available for those fleets/métiers involved in the catch 
of  skates  and  rays,  by  identifying  (i)  those  métiers  (or  higher  aggregation  levels) 
catching  skates,  (ii)  the  catch  composition  (species  and  length  composition)  of  the 
métiers,  and  (iii)  the  social  and  economic  dependence  of  the  métier  on  the  main  skate 
and  rays  species.  Provide  an  overview  of  the  current  scientific  knowledge  and  data 
availability regarding mixed-fisheries involved in the catch of skates and rays 

b)  Evaluate  the  usefulness  of  closed  areas/seasons  as  measures  for  controlling  fishing 
mortality  and/or  protecting  spawning  fish  and  reducing  mortality  on  juveniles  (survey 
data, scientific knowledge available in the literature). 

c)  Collate  and  review  the  results  of  research  on  selectivity  and  relevant  bycatch 
mitigation  measures  for  relevant  fishing  gears  (haul  time  etc.)  that  would  either  help 
avoid the catch of skates and rays, or that could increase their discard survival. Evaluate 
the  effect  of  the  most  relevant  technical  measures  affecting  the  selectivity  of  fishing 
gears. 

d)  Collate  and  review  information  on  the  survival  rates  of  skates  and  rays  (updating 
STECF  2014).  The  output  would  be  a  table  of  stocks  /  species  versus  métier  /fleet 
segment  for  each  sea  basin  or  TAC  unit.  This  exercise  should  consider  to  what  extent 
information  from  one  métier  /  fleet  could  be  extrapolated  to  other  fleets,  detailing  the 
criteria to do so. If this is not possible, then the working group is requested to conduct a 
gap analysis, detailing what information would be required to consider extrapolation and 
high  survivability  exemptions  across  all  species  of  skates  and  rays,  métiers  and  fleer 
segments per sea basin or TAC unit, whichever is more suitable. 

e) Compare the relative merits (Pros and cons-see) of potential alternative management 
measures  proposed  in  the  attached  documentation  by  the  NWWAC  and  the  Dutch 
Elasmobranch Society, as well as the output of the 12 May Focus Group. These potential 
management  measures  can  be  considered  in  a  qualitative,  risk-based  framework  for 
each sea basin or TAC unit, based on expert opinion. DG MARE understands that no one 
measure will be perfect, so where possible, combinations of management measures that 
mitigate risks, should be suggested by the working group. 

An  example  template  is  attached  to  the  background  documentation  as  a  guide.  This 
template  does  not  have  to  be  strictly  followed,  but  provides  an  example  of  comparing 
management  measures  against  the  criteria  mentioned  previously;  e.g.  sustainability, 

23 

 
 
ease of control/enforcement, socio-economic impact (short (1-2 years) vs long-term (2+ 
years)) etc. 

Background documentation: 

1. PLEN 15-011 

2. STECF 15-03, inclusive of background documentation from this contract2 

3. Commission Services Non-Paper Skates and Ray 15 November 2016 

4.  Council  Regulation  (EU)  2017/127  of  20  January  2017  fixing  for  2017  the  fishing 
opportunities for certain fish stocks and groups of fish stocks, applicable in Union waters 
and, for Union fishing vessels, in certain non-Union waters 3 

5. NWWAC 24 March 2017 Advice on Skates and Rays 

6.  PowerPoint  presentation  on  possible  Skates  and  rays  Management  by  the  Dutch 
Elasmobranch Society. 

7.  Flipcharts  and  feedback  from  the  8  May  2017  Brussels  Focus  Group  on  Skates  and 
Rays management. 

8.  Example  Excel  template  for  comparing  the  pros,  cons  and  risk  analysis  of 
management measures against criteria of concern. 

2.3 

Approach followed by EWG-17-10 

The Terms of Reference can be grouped under two broad categories. 

The first category, including ToR a, c and d, is a request for a compilation and review of 
available information related to i) the fleets and métiers involved in the capture of skates 
and rays, ii) the results of research on selectivity and bycatch mitigation measures  and 
iii) the survival rates following discarding.  

For  ToR  (a),  EWG-17-10  has  carried  out  a  general  overview  of  the  fisheries  catching 
skates  and  rays,  presenting  their  main  characteristics  in  terms  of  catches,  métiers  and 
fleet  interactions.  The  objective  is  to  highlight  some  of  the  key  features  of  the  biology 
and  exploitation  of  skates  and  rays  that  may  be  important  to  take  into  consideration 
when developing management measures (e.g. life history traits and distribution, mixed-
fishery interactions). This ToR is addressed in Section 3. 

For ToR (c) (Section 4), a review of available studies on selective gears has been carried 
out both for towed and static gears and a list of available references has been provided.  

For  ToR  (d)  (Section  5),  EWG-17-10  started  from  a  list  of  survival  rate  estimates 
compiled  by  STECF  (STECF,  2014).  This  list  was  updated  with  recent  studies  and 
information  that  is  more  detailed:  survival  rates  are  now  provided  at  species  level  and 
information on some of the key factors impacting survival is also given.  

The  second  category,  including  ToR  (b)  and  (e),  is  a  request  for  a  comparison  of  the 
relative merits of potential alternative management measures. As was mentioned above, 
despite important improvement on the biological and fishery knowledge in recent years, 
skates and rays are still considered by ICES as data-limited stocks. This means that no 
analytical  stock  assessments  are  available  and  that  the  current  advice  is  based  on  the 

24 

 
 
 
precautionary approach. This also means that no quantitative evaluation of management 
measures  is  yet  possible,  in  a  way  similar  to  the  one  conducted  by  STECF  for  the 
demersal  fisheries  of  the  Baltic  sea,  the  North  Sea  and  the  North  and  South  western 
waters (STECF, 2015). On this basis, as a first step in the development of management 
measures for skates and rays, it was decided, for comparison purpose, to draw up a list 
of the pros and cons of a set of potential management measures.  Data needs associated 
with each of those measures are also provided.  

EWG-17-10 started by selecting the potential management measure applicable to skates 
and  rays  from  the  documentation  provided  by  the  NWWAC  (NWWAC  24  March  2017 
Advice  on  Skates  and  Rays)  and  the  Dutch  Elasmobranch  Society  (Shark  and  ray 
management  under  the  landing  obligation,  powerpoint  presentation  to  the  Choke 
symposium  -  02  November  -  2016  Copenhagen),  as  well  as  the  output  of  the  12  May 
Focus  Group.  In  addition  to  the  current  TAC  based  on  a  combination  of  several  stocks, 
the  management  measures  selected  cover  a  large  range  of  management  tools.  This 
includes: 

  The baseline: Skates and Rays generalised TAC 
  Skates and rays generalised TAC with sub-TACs for particular stocks 
  TAC by stock (based on stock ICES advices) 
  TACs by Genus 
  Effort control 
  Spatio-temporal management measures 
  Landing trip limits (outside the quota system, and applied to a selection of 

species) 

  Prohibited species list 
  Minimum and or maximum size (by species, area or group) 
  Gear modifications 

EWG-17-10 has also identified several comparison criteria for the management 
measures listed above. Socio-economic criteria were not included by lack of expertise 
available during the working group.  The selected criteria are in terms of: 

  Capacity to control fishing mortality 
  Ease of control and enforcement 
  Potential issues related to compliance 
  Potential for choke effects 
  Data or information needs for implementation, monitoring and assessment and its 

availability 

  Main sources of uncertainties 

ToR  (b)  and  (e)  are  addressed  in  section  6.  For  each  management  measure,  a  short 
description  is  provided  together  with  the  data  needs  in  terms  of  implementation, 
monitoring and assessment. When possible, some practical examples are provided. The 
pros and cons are also listed. The information provided has been compiled in a summary 
table (Table 6.1) for ease of comparison.  

EWG-17-10  decided  to  first  look  at  the  pros  and  cons  of  the  different  management 
measures taken independently, even though for some measures, some stocks, fisheries 
and/or  areas,  a  combination  of  measures  could  potentially  be  more  appropriate. 
However,  it  was  not  possible,  from  this  separate  review  of  measures,  to  suggest 
potential combinations for the management of skates and rays, as EWG-17-10 considers 
that this should be tailored to the specific needs and issues associated to the particular 

25 

 
 
stocks  or  fisheries.  Instead,  EWG-17-10  provides  some  guidance  on  a  possible  way 
forward (section 7). 

3 

FISHERIES CATCHING SKATES (RAJIDAE) IN THE ICES AREA 

This section of the report addresses the TOR “Collect and analyse information available 
for those fleets/métiers involved in the catch of skates and rays, by identifying (i) those 
métiers  (or  higher  aggregation  levels)  catching  skates,  (ii)  the  catch  composition 
(species  and  length  composition)  of  the  métiers,  and  (iii)  the  social  and  economic 
dependence of the métier on the main skates and rays species. Provide an overview of 
the current scientific knowledge and data availability regarding mixed-fisheries involved 
in the catch of skates and rays”. 

There  is  no  single  dataset  providing  all  relevant  data  (landings,  discards,  species 
composition,  size/sex  composition)  by  gear,  month,  geographical  location  and  nation. 
Various subsets of such data are available that provide such data for the main métiers.  

It  should  also  be  noted  that  the  ICES  Working  Group  on  Elasmobranch  Fishes  (WGEF) 
consider  that  some  ‘species-specific’  records  held  in  official  data  are  inaccurate,  which 
can  be  due  to  a  range  of  issues  (e.g.  coding  errors,  misidentifications,  misreporting). 
Hence,  any  efforts  to  collate  data  from  various  sources  would  require  appropriate  time 
and expertise to take account of such issues. 

3.1 

Skates and rays in the north-east Atlantic 

For  the  purposes  of  this  section,  the  members  of  the  order  Rajiformes  are  referred 
collectively  as  ‘skates’,  even  though  some  may  have  the  term  ‘ray’  in  their  common 
name. 

Approximately 32 species of skate (Rajiformes) occur in the North-east Atlantic with the 
likelihood  of  more,  as  yet  undescribed,  species  occurring  in  deep-water  (Stehmann  & 
Bürkel, 1984; Ebert & Stehmann, 2013; Table 3.1). These species are currently included 
across two families, the soft-nose skates (Family Arhynchobatidae) and hard-nose skates 
(Family Rajidae). 

The soft-nose skates (Family Arhynchobatidae, Bathyraja spp.) are deep-water species, 
and  as  such  not  typically  taken  in  European  fisheries.  The  hard-nose  skates  (Family  Rajidae)  are 
more  widespread  on  the  continental  shelf  and  slope  across  the  ICES  area  (Table  3.2).  The 
main  commercial  skate  taxa  (either  historically  or  currently)  in  EU  Atlantic  waters  are 
listed in Table 3.3, and largely refer to species in three genera: Dipturus, Leucoraja and 
Raja. 

3.2 

Commercial skate taxa  

3.2.1  Genus Dipturus 

There  are  at  least  four  members  of  the  genus  Dipturus  in  European  Atlantic  seas.  Blue 
skate D. batis and flapper skate D. intermedius were formerly widespread in the waters 
of  northern  Europe,  but  declined  in  geographical  range  during  the  1960s  and  1970s, 
which has been linked to overfishing (Brander, 1981). Flapper skate is locally common in 
Scottish  waters,  whilst  blue  skate  is  locally  abundant  in  parts  of  the  Celtic  Sea.  Both 

26 

 
 
 
 
were  formerly  commercial  species,  but  now  they  are  listed  as  prohibited  species1  and 
cannot be landed. 

The  related  Norwegian  skate  D.  nidarosiensis  and  long-nosed  skate  D.  oxyrinchus  tend 
to  occur  on  the  outer  continental  shelf  and  upper  slope,  though  the  exact  geographic 
ranges  are  uncertain.  D.  nidarosiensis  is  a  prohibited  species  in  ICES  Divisions  6.a-b, 
7.a-c,  7.e-h  and  7.k.  The  taxonomy  and  identification  of  skates  in  this  genus  is 
problematic, and landings data have often been confounded (Iglesias et al., 2010; ICES, 
2016, 2017b).   

3.2.2  Genus Leucoraja 

There are three members of the genus Leucoraja in European Atlantic seas, of which the 
smaller-bodied cuckoo ray L. naevus is the most widespread and best studied. L. naevus 
is widely distributed on the continental shelf, ranging from north of Scotland to southern 
Iberian waters, but is less frequent in Divisions 4.c and 7.d. 

The  two  other  members  of  the  genus  (sandy  ray  L.  circularis  and  shagreen  ray  L. 
fullonica) are larger bodied and occur further offshore, with L. fullonica occurring on the 
outer  continental  shelf  and  upper  slope,  and  L.  circularis  occurring  on  the  edge  of  the 
continental  shelf,  upper  slope  and  offshore  banks.  As  such,  both  species  are  typically 
caught  in  fisheries  operating  in  deeper  waters,  including  around  Rockall  and  Porcupine 
Bank. There are ongoing studies to better understand the biology of these species (e.g. 
Nicolaus et al., 2017). 

3.2.3  Genus Raja 

There are eight members of the genus Raja in European Atlantic seas, five of which are 
commercially important over the shelf seas of northern and western Europe.  

Blonde  ray  Raja  brachyura,  thornback  ray  R.  clavata  and  spotted  ray  R.  montagui  are, 
along  with  L.  naevus,  some  of  the  most  ubiquitous  and  common  batoids  in  European 
Atlantic seas, occurring in shelf seas from north of Scotland to southern Iberian waters. 
Small-eyed ray R. microocellata and undulate ray  R. undulata are more coastal  species 
that are distributed from the southern and western British Isles to Iberian waters. Both 
species can be locally abundant in selected areas, possibly due to having more restricted 
habitats. 

Of the remaining species, Mediterranean starry ray R. asterias, as its name implies, is a 
Mediterranean species that occurs very occasionally in the southern parts of Division 9.a; 
brown  ray  R.  miraletus  a  small-bodied  species  of  limited  commercial  interest;  and 
Madeiran ray R. maderensis which occurs around Madeira and the Azores and is also of 
limited commercial interest.  

3.2.4  Other genera 

Most  other  skate  taxa  are  of  low  or  no  commercial  importance  in  Union  waters  of  the 
Atlantic.  Two  exceptions  to  this  are  sailray  Rajella  lintea,  which  may  be  taken  in 
Scandinavian seas and white skate Rostroraja alba. The latter was formerly an important 

1 The listing of a species on the prohibited species list means that the species must not be targeted, retained or 
transhipped. Accidental catch shall not be harmed and individuals should be released as soon as possible. 

27 

 
 
 
 
 
 
 
 
 
 
 
 
                                                 
commercial species, but declined during the 20th century (Ellis et al., 2010). White skate 
is now listed as a prohibited species and is also a protected species in some areas (e.g. 
United Kingdom) 

Table 3.1: Taxonomic list of skates (Rajiformes) occurring in the North-east Atlantic. Adapted from 
Stehmann and Bürkel (1984), Ebert & Stehmann (2013) and Last et al. (2017) 

Scientific name and authority 

English name 

Family Arhynchobatidae 

1 

2 

3 

Bathyraja pallida (Forster, 1967) 

Bathyraja richardsoni (Garrick, 1961)  

Bathyraja spinicauda (Jensen, 1914)  

Family Rajidae 

Pale ray 

Richardson’s ray 

Spinetail ray 

4 

5 

6 

7 

8 

Amblyraja hyperborea (Collett, 1879) 

Arctic skate 

Amblyraja jenseni (Bigelow & Schroeder, 1950) 

Short-tail skate 

Amblyraja radiata (Donovan, 1808) 

Starry ray 

Dipturus batis (Linnaeus, 1758) 

Blue skate (common skate) 

Dipturus intermedius (Parnell, 1837) 

Flapper skate (common skate) 

9 

Dipturus nidarosiensis (Storm, 1881) 
10  Dipturus oxyrinchus (Linnaeus, 1758) 
11 

Leucoraja circularis (Couch, 1838) 

12 

13 

Leucoraja fullonica (Linnaeus, 1758) 

Leucoraja naevus (Müller & Henle, 1841) 

14  Malacoraja kreffti (Stehmann, 1977) 
15  Malacoraja spinacidermis (Barnard, 1923) 
16  Neoraja caerulea (Stehmann, 1976) 
17  Neoraja iberica Stehmann, Séret, Costa & Baro, 2008 
18  Raja asterias Delaroche, 1809  
19  Raja brachyura Lafont, 1873 
20  Raja clavata Linnaeus, 1758 
21  Raja maderensis Lowe, 1841 
22  Raja microocellata Montagu, 1818  
23  Raja miraletus Linnaeus, 1758 
24  Raja montagui Fowler, 1910  
25  Raja undulata Lacepède, 1802  
26  Rajella bathyphila (Holt & Byrne, 1908) 
27  Rajella bigelowi (Stehmann, 1978) 
28  Rajella dissimilis (Hulley, 1970) 
29  Rajella fyllae (Lütken, 1887) 
30  Rajella kukujevi (Dolganov, 1985) 

28 

Norwegian skate 

Long-nosed skate 

Sandy ray 

Shagreen ray 

Cuckoo ray 

Krefft’s ray 

Soft skate 

Blue ray 

Iberian pygmy skate 

Mediterranean starry ray 

Blonde ray 

Thornback ray 

Madeiran ray 

Small-eyed ray 

Brown ray 

Spotted ray 

Undulate ray 

Deepwater ray 

Bigelow’s ray 

Ghost skate 

Round skate 

Mid-Atlantic skate 

FAO 
code 

BYP 

BYQ 

RJQ 

RJG 

RJJ 

RJR 

RJB 

JAD 

RJO 

RJI 

RJF 

RJN 

JFT 

RJP 

BVC 

– 

JRS 

RJH 

RJC 

JFY 

RJE 

JAI 

RJM 

RJU 

JRH 

JRW 

JRQ 

RJY 

– 

 
 
 
 
 
31  Rajella lintea (Fries, 1838) 
32  Rostroraja alba (Lacepède, 1803) 

Sailray 

White skate 

RJK 

RJA 

29 

 
 
 
 
Table 3.2: Nominal occurrence of skates (Rajiformes) in the North-east Atlantic by ICES Division ( = Present,  = absent;  = occasional vagrants likely to occur in the 
area, or distribution may extend to this division; ? = status uncertain). Adapted from Whitehead et al. (1984), Ellis et al. (2005a); ICES (2007; Table 1.4) and Ebert & 
Stehmann (2013). Information considered preliminary. 

Scientific name 

1 

2.a 

2.b 

5.a 

5.b 

3.a 

4.a 

4.b 

4.c 

6.a 

6.b 

7.a 

7.b 

7.c 

7.d 

7.e 

7.f 

7.g 

7.h 

7.j 

7.k 

8.a 

8.b 

8.c 

8.d 

8.e 

9.a 

9.b 

? 

? 

 

 

 

 

 

 

 

 

 

 

Bathyraja pallida 
B. richardsoni 
B. spinicauda 
Amblyraja hyperborea   
A. jenseni 
 
A. radiate 
Dipturus batis 
D. intermedius 
D. nidarosiensis 
D. oxyrinchus 
Leucoraja circularis 
L. fullonica 
L. naevus 
Malacoraja kreffti 
M. spinacidermis 
Neoraja caerulea 
N. iberica 
Raja asterias 
R. brachyuran 
R. clavata 
R. maderensis 
R. microocellata 
R. miraletus 
R. montagui 
R. undulata 
Rajella bathyphila 
R. bigelowi 
R. dissimilis 
R. fyllae 
R. kukujevi 
R. lintea 

 

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10 
12 
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 

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 

 
 
Rostroraja alba 

 

 

 

 

 

 

 

 

 

 

 

 

 

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 

Table 3.3:  List of skates that are, or have been, exploited commercially in northern European fisheries. Those species currently listed as ‘prohibited species’ 
on EU TAC and quota regulations, but which are known to have been important commercial species in former times, are included. Those species prohibited 
in all (or all expected) EU waters of the ICES area are marked , and those species listed as ‘prohibited species’ in certain ICES Divisions are marked . 

FAO 

code 
RJB 

JAD 

RJO 

RJI 

RJF 

RJN 

RJH 

RJC 

JFY 

RJE 

JAI 

RJM 

RJU 

Lmax 

Scientific name 

English name 

Spanish name 

French name 

Portuguese name 

Dutch name 

Norwegian name 

≈ 150 cm  D. batis  

Blue skate 

Noriega 

Pocheteau gris 

Raia oirega 

≈ 230 cm  D. intermedius  

Flapper skate 

– 

– 

≈ 200 cm  D. nidarosiensis  

Norwegian skate 

Raya noruega 

Pocheteau de Norvège 

– 

– 

Vleet 

– 

Glattskate 

– 

Noorse rog 

Svartskate 

≈ 150 cm  D. oxyrinchus 

Long-nosed skate 

Raya picuda 

Pocheteau noir 

Raia bicuda 

Scherpsnuitrog 

Spisskate 

≈ 120 cm 

L. circularis 

Sandy ray 

Raya falsa vela 

Raie circulaire 

Raia-de-São-Pedro 

Zandrog  

≈ 120 cm 

L. fullonica 

Shagreen ray 

Raya cardadora 

Raie chardon 

Raia pregada 

Kaardrog 

Sandskate 

Nebbskate 

72–81 cm 

L. naevus 

Cuckoo ray 

Raya santiguesa 

Raie fleurie 

Raia-de-dois-olhos 

Koekoeksrog 

– 

≈ 120 cm  R. brachyura 

Blonde ray 

Raya boca de rosa 

Raie lisse 

Raia pontuada 

Blonde rog 

Prikkskate 

110–130 cm  R. clavata 

Thornback ray 

Raya de clavos 

Raie bouclée 

Raia-brocheada 

Stekelrog 

Piggskate 

≈ 80 cm  R. maderensis 

Madeira skate 

Raya de Madeira 

Raie de Madère 

Raia da Madeira 

– 

91 cm  R. microocellata 

Small-eyed ray 

Raya colorada 

Raie mêlée 

Raia-zimbreira 

Kleinoogrog 

≈ 60 cm  R. miraletus 

Brown ray 

Raya de espejos 

Raie miroir 

Raia-de-espelhos 

– 

– 

– 

– 

75–80 cm  R. montagui 

Spotted ray 

Raya pintada 

Raie douce 

Raia manchata 

Gevlekte rog 

Flekkskate 

114–120 cm  R. undulata  

Undulate ray 

Raya mosaica 

Raie brunette 

Raia-mosaica 

Golfrog 

– 

31 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
RJK 

RJA 

≈ 125 cm  R. lintea 

Sailray 

Raya vela 

Raie voile 

Raia-nevoeira 

Zeilrog 

Hvitskate 

≈ 240 cm  R. alba  

White skate 

Raya bramante 

Raie blanche 

Raia-branca 

Witte rog 

– 

32 

 
 
 
 
3.3 

General overview of those métiers catching skates 

The generalities of commercial fleets and métiers that catch skates are described below. 
For  the  purposes  of  this  report,  we  have  differentiated  between  ‘inshore,  coastal  and 
deepwater  fleets’.  Coastal  fleets  refer  to  those  vessels  that  generally  operate  closer  to 
their home port, often in shallower water (at least in those areas where there is a broad 
continental  shelf)  and  mainly  involve  smaller  vessels.  It  is  important  to  differentiate 
between  these  fleets  as  the  coastal  fleets  can  often  have  a  proportionally  greater 
economic interest in some coastal  skate species (e.g. Raja brachyura, R. microocellata, 
R. undulata). The main fleets, usually involving larger vessels that operate over broader 
areas of the continental shelf are referred to here as ‘offshore fleets’, with ‘deep-water’ 
fleets  referring  to  those  vessels  fishing  along  the  edge  of  the  continental  shelf  and 
continental slope.  

3.3.1  Inshore and coastal fleets 

Skates,  especially  those  within  the  genus  Raja,  are  often  found  in  coastal  and  inner 
continental  shelf  seas.  In  these  areas,  skates  are  either  a  bycatch  or,  in  areas  of  high 
local and/or seasonal abundance are targeted. Target fisheries for skates can be of high 
importance for coastal fleets over much of the ICES area. 

Species  such  as  R.  clavata,  R.  montagui  and  Leucoraja  naevus  are  widespread  on  the 
inner  continental  shelf  for  much  of  the  Union  waters  of  the  ICES  areas.,  Other  species 
(e.g.  R.  brachyura,  R.  microocellata  and  R.  undulata)  may  be  proportionally  more 
abundant  in  inshore  waters  and  in  areas  of  high  local  abundance.  Skates  in  the  genus 
Leucoraja are not generally taken in large quantities by inshore fleets, unless there is a 
narrow  continental  shelf  and  access  to  waters  >50  m  close  to  shore  (e.g.  around  the 
south-west  UK,  Ireland,  Iberian  waters).  In  some  inshore  areas  of  the  northern  ICES 
areas, including Scotland and Northern Ireland, members of the common skate complex 
Dipturus are also found in areas close to shore. 

Nets: Skates are caught as a bycatch in the various gillnet fisheries, including set gillnets 
and  demersal  driftnets.  They  may  also  be  targeted  in  larger  mesh  nets  (e.g.  trammel 
and tangle nets), where the minimum mesh sizes is ≥220 mm. Such fisheries generally 
exploit  the  larger  species  such  as  R.  clavata,  R.  brachyura,  R.  microocellata  and  R. 
undulata.  For  the  inshore  fleet,  soak  times  typically  range  from  2-3  h  (e.g.  some 
demersal driftnets) up to 24-48 h.  

Trawls: Skates are a bycatch in various inshore trawl fisheries, including multi-rig trawls 
for  Nephrops  and  shrimp.  In  areas  of  high  local  abundance,  skates  can  be  a  very 
important  catch  component  and  may  even  be  the  target  species  in  some  areas  or 
seasons. Such fisheries often exploit the broader skate complex, including R. clavata, R. 
brachyura,  R.  montagui,  Leucoraja  naevus  and,  in  some  areas,  R.  undulata  and  R. 
microocellata. For the inshore fleet, haul times would be expected to range from 0.5-4 h.  

Longline:  Skates  are  an  important  catch  component  in  inshore  demersal  longline 
fisheries  and  are  also  the  target  species  in  some  areas  and/or  seasons.  Such  fisheries 
generally exploit the larger species such as R. clavata, R. brachyura and R. undulata. For 
the inshore fleet, soak times for longlines can be about 2-4 h (e.g. in the southern North 
Sea), but may be left overnight in other areas. 

3.3.2  Offshore fleets 

A  broader  range  of  skate  genera  occur  on  the  outer  continental  species,  including  Raja 
(R. clavata, R. montagui), Leucoraja (L. naevus and, on the outer shelf and upper slope, 

33 

 
 
L.  circularis  and  L.  fullonica),  larger  skates  (Dipturus  spp.)  are  often  found  on  the 
continental shelf and upper slope. 

Nets:  Various  types  of  set  nets  (including  gillnets,  tangle  nets  and  trammel  nets)  are 
used  by  larger  vessels  operating  offshore,  typically  for  fleets  targeting  anglerfish,  hake 
and large gadoids. Skates are typically a bycatch (of varying commercial importance) in 
most  areas,  although  there  are  some  areas  where  they  may  have  been  targeted  (e.g. 
parts of the Celtic Sea). Soak times in these fisheries can range up to several days. 

Otter  trawl:  Skates  are  a  bycatch  in  various  offshore  trawl  fisheries.  In  areas  of  high 
local abundance, skates can be a very important catch component and may even be the 
target species or species complex in some areas or seasons. Such fisheries often exploit 
the  broader  skate  complex,  including  R.  clavata,  R.  brachyura,  R.  montagui  and 
Leucoraja naevus. 

Beam  trawl:  Skates  are  typically  a  bycatch  in  various  beam  trawl  fisheries  (including 
beam trawl fisheries for flatfish, as well as shrimp fisheries). Beam trawls generally catch 
smaller individuals of skates compared to other gears. 

Longline:  There  are  occasional  longline  fisheries  in  the  deeper  parts  of  the  ICES  areas 
(e.g. for hake, ling and tusk), where skates can be an incidental bycatch.  

3.3.3  Deepwater fleets 

There are a range of deep-water fisheries operating in the ICES area, including longline 
fisheries and some trawl fisheries. A wide range of skate taxa might be encountered as 
bycatch,  including  representatives  from  two  distinct  families  in  the  order  Rajiformes 
(Rajidae  and  Arhynchobatidae).  Nevertheless,  there  is  no  indication  of  any  notable 
quantities being either landed or caught.  

3.3.4  Miscellaneous fisheries and gears 

In addition to the main commercial gears taking skates, there can also be an incidental 
bycatch  of  skates  in  other  fisheries  (Table  3.4).  For  example,  there  are  several  dredge 
fisheries  for  invertebrates  (e.g.  scallops  and  other  bivalves)  that  can  capture  skates, 
primarily smaller individuals and, potentially, egg cases. Whilst there have been several 
localised  accounts  of  such  fisheries  interacting  with  skates  (e.g.  Palma  et  al.,  2003; 
Craven et al., 2013), there is generally a paucity of information on the catches, discards 
and discard survival.     

34 

 
 
Table 3.4: Higher level métiers and interactions with skates (Rajidae) 

Level 2: 
Gear 
class 

Level 3: 
Gear group 

Dredges 

Dredges 

Bottom trawls 

Trawls 

Pelagic trawls 

Hooks 
and Lines 

Rods and 
Lines 

Longlines 

Level 4: Gear type 

Involvement in skate fisheries 

Boat dredge [DRB] 

Skates can be a bycatch in various dredge fisheries (e.g. for scallops) 

Mechanised/Suction 
dredge (HMD) 
Bottom otter Trawl 
(OTB) 
Multi-rig otter trawl 
[OTT] 

Minimal interactions with skates, but potential interactions with early 
life history stages, including egg cases 
Skates can be an important bycatch and, in some areas, there can be 
targeted fisheries for the skate complex 
Skates can be an important bycatch and, in some areas, there can be 
targeted fisheries for the skate complex 

Bottom pair trawl [PTB]  Skates can be an important bycatch 

Beam trawl [TBB] 

Midwater otter trawl 
[OTM] 

Pelagic pair trawl [PTM] 

Hand and Pole lines 
[LHP] [LHM] 

Skates are a bycatch, and this gear may catch proportionally more 
juveniles in comparison to other bottom trawls 
Skates may be an incidental bycatch, depending on fishing location and 
fishing depths 
Skates may be an incidental bycatch with very rare occurrence, 
depending on fishing location and fishing depths 
Minimal interactions 

Minimal interactions 

Trolling lines [LTL]  Minimal to no interactions 

Drifting longlines [LLD]  Minimal interactions for surface longlines 

Set longlines [LLS] 

Skates can be an important bycatch in bottom-set longlines and, in 
some areas, there can be targeted fisheries for skates 

Pots and Traps [FPO]  Minimal interactions 

Traps 

Traps 

Fyke nets [FYK] 

Stationary uncovered 
pound nets [FPN] 

Trammel net [GTR] 

Set gillnet [GNS] 

Driftnet [GND] 

Purse seine [PS] 

Skates may be an incidental bycatch, depending on fishing location (e.g. 
fyke nets set in marine waters) 
Minimal interactions 

Skates can be an important bycatch in bottom-set trammel and, in some 
areas, there can be target fisheries for skates (i.e. where the mesh size 
is ≥220 mm)  
Skates can be an important bycatch and, in some areas, there can be 
target fisheries for skates (i.e. where the mesh size is ≥220 mm) 
Skates can be an important bycatch in demersal driftnets 

Minimal interactions 

Nets 

Nets 

Surrounding 
nets 

Seines 

Seines 

Lampara nets [LA]  Minimal to no interactions 

Fly shooting seine [SSC]  Skates can be an important bycatch 

Anchored seine [SDN]  Skates can be an important bycatch 

Pair seine [SPR] 

Beach and boat seine 
[SB] [SV] 

Skates can be an important bycatch 

Coastal skates may be taken 

Other 
gear 
Misc. 
(Specify) 

Other gear 

Glass eel fishing 

Minimal interactions 

Misc. 
(Specify) 

-  

35 

 
 
 
3.4 

Skates and their fisheries by area 

In general terms, skates are a bycatch in mixed demersal fisheries using bottom trawls 
and gill- and trammel nets, with some target fisheries (large-mesh tangle and trammel 
nets, demersal lines and otter trawl) occurring in some areas of high local abundance.  

3.4.1  Skagerrak (Division 3.a) 

Otter trawls are the most common gear types used with the fisheries typically catching 
gadoids,  other  groundfish,  Pandalus,  plaice,  and  Nephrops.  The  species  composition  of 
the catch depends on the area and depth fished and the gear design, including cod-end 
mesh size. Bottom seine fisheries also operate in this area and have similar mesh sizes 
and  target  species  as  otter  trawl  fisheries.  In  the  shallower  areas  the  Skagerrak  there 
are  also  gillnet  fisheries  operated  by  small  and  medium-sized  vessels  targeting  flatfish 
and  demersal  fish.  The  skate  fauna  of  the  Skagerrak  is  poorly  known,  especially  in 
deeper waters, but they are likely to be taken in both trawl and gillnet fisheries. 

According  to  Council  Regulation  (EU)  2017/127  catches  of  Leucoraja  naevus,  Raja 
brachyura and Raja montagui should be reported separately for this TAC area (although 
none  of  these  species  seem  to  have  been  recorded  in  trawl  surveys,  Heessen  et  al., 
2015).  Amblyraja  radiata,  Dipturus  batis-complex  and  Raja  clavata  are  prohibited 
species in the area and there is no requirement for landings of L. circularis, L. fullonica, 
Dipturus  nidarosiensis  and  Rajella  lintea,  which  may  occur  in  the  deeper  waters  of 
Division 3.a, to be reported by species. 

3.4.2  North Sea (Divisions 4.a-c) 

In  the  North  Sea,  skates  are  caught  mainly  as  a  bycatch  in  mixed  trawl  fisheries  for 
roundfish  and  flatfish.  Otter  trawls  (with  mesh  sizes  greater  than  100  mm)  target 
haddock,  cod,  whiting,  anglerfish,  megrim,  and  plaice,  with  important  bycatch  of 
Nephrops and some flatfish species. Some vessels target saithe in deeper waters in the 
north of the region. Other parts of the otter trawl fleet operate with mesh sizes less than 
100  mm.  This  fleet  primarily  targets  Nephrops  in  muddy  areas  and,  in  other  fishing 
grounds,  a  mix  of  fish  and  shellfish  (including  cephalopods).  Bottom  seine  fisheries 
operate mainly in the central and southern North Sea with limited effort in the northern 
North  Sea.  This  fleet  targets  the  same  species  as  the  otter  trawl  fleet  and  the  fishing 
gear  used  has  similar  mesh  size.  Trawl  fisheries  in  the  northern  North  Sea  would  be 
expected to have a bycatch of L. naevus, R. montagui and Dipturus intermedius. 

In the shallow parts of the southern and central North Sea in the southern Bight, beam 
and  pulse  trawl  fisheries  have  particularly  intense  fishing  activity.  The  most  important 
species caught are sole and plaice in terms of value and volume, respectively, with other 
flatfish  (e.g.  turbot  and  brill)  valued  species.  Because  of  the  relatively  small  codend 
mesh  size  (80  mm)  used  in  beam  trawls  targeting  flatfish,  significant  quantities  of  fish 

36 

 
 
 
 
 
  
 
 
 
below  minimum  sizes  may  be  caught,  resulting  in  high  discard  rates.  Small  beam 
trawlers (<24 m LOA) target brown shrimp in the southern North Sea and coastal areas 
using  a  20–25  mm  codend  mesh  size.  These  fisheries  also  catch  various  species  of 
skates. 

In  the  North  Sea  are  there  are  also  mixed  fisheries  using  static  fishing  gears.  In  the 
southern  North  Sea,  gillnet  fisheries  target  flatfish  (sole)  and  demersal  fishes.  Some  of 
these fisheries seasonally and/or locally target Raja clavata.  When conducted in deeper 
areas of the northern North Sea, gillnet fisheries target anglerfish. Gillnet fisheries using 
small mesh sizes (90 mm) usually target sole, and may have considerable discard rates 
of dab. In the northern North Sea, longline fisheries target saithe, cod, haddock, ling and 
tusk. There are also inshore longline fisheries in the south-western North Sea, where the 
main  species  of  commercial  interest  are  cod,  bass,  Raja  clavata  and  R.  brachyura.  The 
latter is usually taken in low numbers but is of higher value. 

According  to  Council  Regulation  (EU)  2017/127,  catches  of  Leucoraja  naevus,  Raja 
brachyura,  Raja  clavata  and  Raja  montagui  should  be  reported  separately  for  this  TAC 
area,  and  these  are  among  the  main  skate  species  in  the  area  (Heessen  et  al.,  2015). 
Amblyraja  radiata  and  Dipturus  batis-complex  are  both  prohibited  species  in  this  area. 
There  is  no  necessity  for  landings  of  L.  circularis,  L.  fullonica,  Dipturus  nidarosiensis, 
Dipturus oxyrinchus and Rajella lintea (which may occur in the northern North Sea), or 
for Raja microocellata and Raja undulata (which may extend into the southernmost part 
of the North Sea) to be reported to species. 

3.4.3  Eastern English Channel (Division 7.d) 

Skates  in  the  eastern  English  Channel  are  caught  mainly  in  mixed  demersal  fisheries. 
Otter  trawls  are  the  most  common  métier  operating  over  the  wider  area.  This  fleet 
operates  with  mesh  sizes  less  than  100  mm  and  catches  a  variety  of  fish  and  shellfish 
species (including cuttlefish). There are also  beam trawl fleets targeting sole and plaice, 
that are known to capture juvenile skates.  

In the English Channel there are also gillnet fisheries that take Rajidae species as either 
a target species or bycatch. The bycatch is taken in gillnet fisheries for flatfish (e.g. sole) 
and roundfish.  

There  are  also  dredge  fisheries  for  scallops.  These  fisheries  occur  primarily  on  sand-
gravel  substrates  and  there  are  some  exclusion  zones  to  protect  sensitive  habitats  in 
some areas. The potential interaction of this fishery with skates is unknown. 

According  to  Council  Regulation  (EU)  2017/127,  catches  of  Leucoraja  naevus,  Raja 
brachyura, Raja clavata, Raja montagui and Raja undulata should be reported separately 
for  this  TAC  area  (the  latter  in  a  sub-TAC).  Amblyraja  radiata  and  Dipturus  batis-
complex are both prohibited species in this area, although the former is not expected to 

37 

 
 
 
 
 
 
 
 
 
occur in the area. There is currently no necessity for landings of Raja microocellata to be 
reported at the species level. 

Celtic Seas Ecoregion 

This  ecoregion  displays  subtle  differences  in  the  skate  assemblages,  and  are  so 
described in finer detail below. 

According  to  Council  Regulation  (EU)  2017/127,  landings  of  Leucoraja  circularis, 
Leucoraja  fullonica,  Leucoraja  naevus,  Raja brachyura,  Raja clavata  and  Raja montagui 
should  be  reported  to  species  in  this  TAC  area.  There  are  sub-TACs  for  two  stocks, 
allowing  for  Raja  undulata  to  be  landed  from  Division  7.e  and  Raja  microocellata  to  be 
landed  from  7.f-g.  These  should  also  be  recorded  to  species  level.  Prohibited  skate 
species  in  this  TAC  area  are  Raja  undulata  (Subarea  6),  Dipturus  batis-complex 
(Subareas  6-7  and  elsewhere),  Rostroraja  alba  (Subareas  6-7  and  elsewhere)  and 
Dipturus  nidarosiensis  (Divisions  6.a-b,  7.a-c,  7.e-h  and  7.k).  There  is  currently  no 
requirement for Dipturus oxyrinchus to be reported to species level.  

3.4.4  Northwest Scotland (Divisions 6.a-b) 

Skates  are  caught  mainly  in  mixed  demersal  fisheries  operating  with  otter  trawls.  As  a 
consequence  of  fishing  effort  restrictions  resulting  from  the  EU’s  cod  management  plan 
(Regulation  1342/2008),  the  main  otter  trawl  fisheries  are  predominantly  for  Nephrops 
fisheries  and  mixed  demersal  species  mainly  hake,  anglerfish  and  megrim.  There  are 
also mixed gadoid fisheries using larger mesh size, typically 120 mm. Such fisheries will 
catch Dipturus intermedius, Raja clavata, Raja montagui and Leucoraja naevus. Vessels 
operating  in  the  deeper  waters,  including  Rockall,  will  catch  deep-water  species, 
including L. fullonica.  

In inshore areas, scallop fisheries (using dredge) operate on sand-gravel substrates, and 
these fisheries may have some bycatch of skates.  

3.4.5  West of Ireland (Divisions 7.b-c and 7.j-k) 

Rajidae  species  are  mainly  caught  in  mixed  demersal  fisheries  operating  with  otter 
trawls.  The  rays  are  caught  along  with  cod,  haddock,  whiting,  plaice,  sole,  hake, 
anglerfish  and  megrim.  They  are  also  caught  in  targeted  artisanal  fisheries  in  a  few 
places  along  the  coast  using  gill  and  tangle  nets,  and  sometimes  longlines.  Beam 
trawlers are confined mainly to 7.g, and majority of vessels employ meshes of 80 mm. 

3.4.6  Irish Sea, Bristol Channel and northern Celtic Sea (Divisions 7.a and 7.f-g) 

38 

 
 
 
 
  
 
 
 
 
 
 
  
 
 
The  Irish  Sea  mixed  gadoid  fisheries,  using  larger  mesh  size,  has  declined  in  line  with 
the EU’s cod management plan (Regulation 1342/2008), and the main otter trawl fishery 
in the Irish Sea (Division 7.a) is currently the Nephrops fishery. Comparatively few skate 
species  occur  on  the  main  Nephrops  grounds.  There  are  also  mixed  demersal  trawl 
fisheries  in  the  northern  Celtic  Sea  and  Bristol  Channel,  and  a  range  of  skate  species 
occur  on  these  grounds.  There  are  also  some  localised  and/or  seasonal  trawl  fisheries 
targeting the wider skate complex (R. brachyura, R. clavata, R. microocellata (mostly in 
7.f-g) and, to a lesser extent, L. naevus and R. montagui) in the south-western Irish Sea 
(Divisions 7.a) and Bristol Channel (7.f-g). 

Beam  trawlers  also  operate  in  the  area  (mesh  sizes  of  80–89  mm)  and,  whilst  often 
targeting plaice and sole, will operate on grounds where skates occur. 

Various gillnet fisheries operate in Divisions 7.a and 7.f-g, often targeting large gadoids 
and,  further  west,  catching  anglerfish.  Turbot  and  brill  are  important  bycatch  species, 
with  a  range  of  skates  also  taken.  The  mesh  sizes  used  vary,  but  recently  the  use  of 
larger mesh sizes (varying from 150 -219 mm) has increased. There are some localised 
and/or seasonal fisheries targeting the wider skate complex (R. brachyura, R. clavata, R. 
microocellata and R. montagui) with nets of ≥220 mm mesh size. Dipturus batis appear 
to be locally abundant in parts of the Celtic Sea, and are a bycatch in some net fisheries. 

The scallop fisheries operating in this area, including in the Irish Sea, are known to have 
a bycatch of L. naevus which is frequently discarded in the scallop fishery around the Isle 
of Man (Craven et al., 2013). 

There is also a large recreational fishery for skates, particularly for those species close to 
shore, with some ports having locally important charter boat fisheries. There is likely to 
be some retention of skates, although the levels of these catches are unknown. 

3.4.7  Western English Channel and approaches (Division 7.e and 7.h) 

There are a range of bottom trawl fisheries (otter and beam trawl) in the area, as well as 
net  fisheries  (gillnet,  wreck  net,  trammel  net)  operating  in  this  area.  There  are  also 
important fisheries for a range of shellfish, some of which will presumably have minimal 
interactions  with  skates  (e.g.  pot  fisheries  for  crab  and  lobster),  and  other  fisheries  in 
which skates may be a bycatch (e.g. trawling for cuttlefish and dredging for scallops). 

There  is  a  high  diversity  of  skates  in  this  area  (Dipturus  batis,  Leucoraja  fullonica,  L. 
naevus,  Raja  brachyura,  R.  clavata,  R.  microocellata,  R.  montagui  and  R.  undulata)  all 
locally abundant in various parts of the area. 

Biscay-Iberian Ecoregion 

This  ecoregion  displays  subtle  differences  in  the  skate  assemblages,  and  are  so 
described in finer detail below. 

39 

 
 
 
 
 
 
 
 
 
 
 
According  to  Council  Regulation  (EU)  2017/127,  landings  of  Leucoraja  naevus,  Raja 
brachyura  and  Raja  clavata  should  be  reported  to  species  in  this  TAC  area.  There  are 
sub-TACs  for  Raja  undulata  in  both  Subarea  8  and  Subarea  9,  and  landings  of  this 
species  should  also  be  recorded  to  species  level.  Prohibited  skate  species  in  this  TAC 
area  are  Dipturus  batis-complex  (Subareas  8-9  and  elsewhere)  and  Rostroraja  alba 
(Subareas  8-9  and  elsewhere).  There  is  currently  no  requirement  for  landings  of 
Dipturus  oxyrinchus,  Leucoraja  circularis,  Leucoraja  fullonica,  Raja  microocellata  and 
Raja montagui to be reported to species level. 

3.4.8  Bay of Biscay (Divisions 8.a-b, 8.d-e) 

In  the  Bay  of  Biscay,  Spanish  and  French  trawl  fleets  are  the  main  métiers  landing 
skates. In 2016, skate landings originated mainly from Divisions 8.a–b (77%), and these 
were mostly from France (1560 t). In the 1960s, skates were taken primarily by bottom 
trawl  fisheries  operating  in  the  northern  parts  of  the  Bay  of  Biscay.  At  that  time,  Raja 
clavata  was  the  main  landed  species  and  was  targeted  seasonally.  After  the  1980s, 
Leucoraja  naevus  became  the  main  skate  species  landed  by  the  French  fisheries.  After 
1986, landings of both these species declined. Other skates are also landed, including L. 
circularis, L. fullonica, R. microocellata, D. batis complex and D. oxyrinchus. There have 
been  no  major  annual  landings  of  Rostroraja  alba  by  French  fleets  in  the  past  three 
decades. 

The  historical  French  catches  of  skates  in  coastal  fisheries  are  poorly  known.  Species 
landings of coastal, such as Raja brachyura, R. microocellata and Raja undulata began to 
be reported after the EU legislation on species recording of landings (Council Regulation 
(EC) 43/2009). 

Spanish demersal fisheries operating in the Bay of Biscay (Divisions 8.a–b and 8.d) catch 
various  skate  species  using  different  fishing  gears.  Most  landings  are  a  bycatch  from 
trawl  fisheries  targeting  demersal  teleosts,  (e.g.  hake,  anglerfish  and  megrim).  L. 
naevus and R. clavata are the most important landed species.  

3.4.9  Cantabrian Sea (Division 8.c) 

Skate  landings  in  Division  8.c  account  for  ca.  20%  of  the  total  landed  from  Subarea  8, 
and are mainly from Spain (407 t in 2016). The Spanish demersal fisheries operating in 
the  Cantabrian  Sea  catch  skates  as  a  bycatch  in  trawl  fisheries  targeting  demersal 
teleosts.  The  most  important  species  caught  by  these  fisheries  are  L.  naevus  and  R. 
clavata. 

There are also some artisanal fisheries that operate closer to the coast that catch various 
skates, as a bycatch. The Spanish artisanal fleets catching skates are not well described 
but most of the skate landings have been attributed to gillnet fisheries operating in bays 

40 

 
 
  
 
 
 
 
 
 
 
 
along  the  northern  coast  of  Spain.  Historically,  and  due  to  their  comparatively  low 
commercial  value,  most  skate  species  caught  by  these  artisanal  fisheries  were  landed 
under a unique generic name. 

3.4.10 Atlantic Iberian waters (Division 9.a) 

In  the  western  parts  of  the  Iberian  Peninsula,  skates  are  caught  mainly  as  bycatch  in 
fisheries  targeting  other  species  (fin-fish  and  crustaceans).  In  the  past,  in  the  north  of 
Spain there was a targeted skate fishery that used a special fishing gear, a gillnet type 
known  locally  as  ‘raeiras’  (DOG  nº  31  15/02/2011).  This  fishery  took  place  at  more 
coastal  areas  and  inside  rias  and  estuaries.  At  present,  there  are  no  Spanish  directed 
fisheries and most of the landings come from the trawl fisheries targeting other species 
(Rodriguez-Cabello et al., 2005). In the inshore areas, i.e. inside Galician estuaries, the 
artisanal fleet operates with a special type of gillnet known locally as ‘miño’ (DOG nº 31 
15/02/2011), and this commonly catches skates. The two most important species in this 
fishery  are  Raja  montagui  and  R.  brachyura  (Bañón  et  al.,  2008).  The  landings  from 
these  inshore  fisheries  represent  nearly  9%  of  the  Spanish  total  landings  of  skate  in 
this/the  ICES  area  (Bañón  et  al.,  2008).  Raja  undulata  is  caught  mainly  in  the  coastal 
waters of Galicia (northern part of Division 9.a and western part of Division 8.c). Other 
skate  species  caught  in  Galician  waters  include  R.  brachyura,  R.  microocellata,  R. 
montagui, R. clavata and L. naevus.  

Along  the  Portuguese  continental  coast  (Division  9.a),  skate  species  are  caught  mainly 
by  the  polyvalent  segment,  which  represents  around  75%  of  the  total  landed  weight, 
followed  by  the  trawl  segment  (24%).  The  trawl  fleet  segment  included  vessels  that 
operate with mesh sizes of 55, 65 or 70 mm. 

The  Portuguese  polyvalent  segment  includes  vessels  with  ranging  from  5  to  27  m  in 
overall  length  which  generally  operate  in  waters  between  10  and  150  m  deep.  These 
vessels  may  use  a  range  of  fishing  gears  and  catch  a  high  diversity  of  skate  species. 
Vessels  in  this  fleet  may  have  more  than  one  fishing  gear  (e.g.  trammel  nets,  gillnets, 
longline, trawl, traps and/or pots) and consequently different fishing gears may be used 
during  a  fishing  trip.  Within  the  polyvalent  segment,  skates  are  caught  mainly  by  nets 
(trammel  and  gillnets).  For  the  period  2008-2016  the  landed  weight  derived  from  nets 
represented  65-78%  of  the  total  landed  weight,  while  longline  and  artisanal  trawl 
represented 19- 24%, and up to 5% respectively.  

In the Gulf of Cádiz, skates are taken mainly as a bycatch in Spanish fisheries targeting 
demersal species, mostly involving the trawl fleet. The artisanal fishing fleet operating in 
shallow  waters  close  to  the  Guadalquivir  river  mouth  with  trammel  nets  catch  other 
batoids,  mainly  Dasyatis  pastinaca  and  Myliobatis  aquila.  These  two  species  are 
economically  important  being  locally  consumed.  Hydraulic  dredges  targeting  clams 
Chamaela gallina may also catch batoid species. 

41 

 
 
 
 
 
 
 
 
3.4.11 Azores (Division 10.a) 

Two  broad  types  of  fisheries  occur  in  ICES  Subarea  10:  the  ‘oceanic  fisheries’,  which 
involves  large  midwater  and  bottom  trawlers  and  longliners  that  operate  in  the  central 
region  and  northern  parts  of  the  Mid-Atlantic  Ridge  (MAR),  and  the  ‘Azorean  fishery’. 
Through  time,  skate  landings  from  the  former  have  been  relatively  small,  or  even 
absent, and at present their catches are considered minimal, as limited demersal fishing 
occurs  in  the  MAR.  Fisheries  operating  within  the  Azorean  EEZ  catch  several  skate 
species,  typically  in  the  multispecies  demersal  fishery,  that  uses  handlines  or  bottom 
longlines, and by the black scabbardfish fishery that uses bottom longlines. Raja clavata 
is the most commercially important skate caught and landed (ICES, 2005, 2017b). 

3.5 

Length distribution of skates in example fisheries 

There  are  no  internationally  collated  data  to  show  the  length  compositions  of  skates 
taken  in  the  various  European  fisheries.  However,  some  examples  from  particular  case 
studies are presented below, which can be used to infer the types of length compositions 
that can be seen in different fisheries.  

In terms of the length distributions of skates that are discarded or retained, it should be 
noted  that  there  are  various  factors  that  influence  discarding  patterns,  ranging  from 
commercial  drivers  (e.g.  market  price,  condition  of  fish  caught)  to  the  influence  of 
management measures (e.g. quota available, regional bylaws relating to minimum sizes 
etc.).  Hence,  any 
the  size  distribution  of 
discarded/retained  skates  should  be  viewed  as  examples  only,  and  not  necessarily 
indicative for specific fisheries. 

information  presented  below  on 

Ellis et al. (2010) and Silva et al. (2012) provided information on the length distributions 
of skates taken in various UK fisheries by broad métier. In general terms, beam trawlers 
mostly capture skates from ≈10 cm (size at hatching) to ≈70 cm, peaking at about 20-
40  cm,  and  with  only  occasional  captures  of  skates  >90  cm.  In  contrast,  whilst  otter 
trawlers also capture newly hatched skates, the peak length range was ≈40-60 cm, and 
proportionally more fish within the 70-90 cm size range would be taken. The size range 
of  skates  taken  in  gillnets  (≤150  mm  mesh  size)  was  also  quite  broad,  but  recently 
hatched  fish  (20-30  cm  length  range)  were  not  usually  observed.  Gillnets  (including 
tangle  and  trammel  nets)  with  larger  mesh  sizes  (>150  mm)  appeared  the  most  size 
selective, with most fish from 50-90 cm. These gears were one of the more effective for 
catching larger (>90 cm) skates (Figure 3.1). 

Whilst larger skates are also taken in longline fisheries, these gears also capture fish of 
more  moderate  size.  For  example,  studies  on  R.  clavata  in  the  southern  North  Sea 
indicate  that  trawls  catch  proportionally  more  small  fish,  followed  by  gillnets,  longlines 
and large mesh gillnets the most size selective (Figures 3.2-3.3). Comparable patterns in 
the  size  compositions  of  skates  are  seen  in  other  species  and  fleets  (Figure  3.4).  ICES 
(2017a)  provide  further  examples  of  the  size  compositions  of  skates  taken  by  various 
national métiers. 

Length–frequency  distributions  of  L.  naevus  and  R.  clavata  (Figure  3.5),  and  R. 
brachyura and R. microocellata (Figure 3.6) from the Portuguese commercial polyvalent 
and trawl fleets (2008–2016) were extrapolated to the total estimated landed weight of 
each  species.  Length  distributions  and  their  ranges  were  similar  between  years  for  the 

42 

 
 
 
 
fleets, but there were differences in the length distributions between the two fleets. For 
both  R.  brachyura  and  R.  microocellata,  landings  from  trawlers  could  comprise  of 
proportionally smaller length classes, with larger fish taken by the polyvalent fleet.  

Figure 3.1: Length frequency distribution (numbers at total length) of commercial skates 
(excluding Dipturus batis-complex and Raja undulata) for (a) beam trawl, (b) otter trawl, 
(c) Nephrops trawl, (d) gillnets (≤150 mm mesh size) and (e) gillnets (>150 mm mesh 
size),  showing  those  that  were  discarded  (grey)  and  retained  (black).  From  Silva  et  al. 
(2012). 

Figure  3.2:  Length  frequency  distribution  (cumulative  percentage  by  total  length)  of 
thornback  ray  Raja  clavata  caught  in  the  southern  North  Sea  by  three  inshore  trawlers 

43 

 
 
 
 
(solid  pink,  red  and  green  lines),  gillnets  (solid  blue  line),  longline  (dashed  lines)  and 
gillnets (>260 mm mesh size). From Ellis et al. (2008). 

Figure 3.3 Length-based discard-retention patterns of thornback ray Raja clavata caught 
in ICES Divisions 4.b.c and 7.d) by otter trawl, beam trawl, longline, gill net (≤150 mm 
mesh size) and gillnet (>150 mm mesh size) as recorded during the UK (English) 
observer programme (2002-2016). From ICES (2017a). 

44 

 
 
 
Figure 3.4. Length-based discard-retention patterns of cuckoo ray Leucoraja naevus 
caught in ICES Subareas 6 and 7 by métier (2011-2016 combined), as recorded during 
the French observer programme. Métiers are GTR-demersal fish (top left), miscellaneous 
gears (top right), OTB-demersal fish (bottom left) and OTT-demersal fish (bottom right). 
From ICES (2017a). 

45 

 
 
 
 
 
Figure 3.5: Length–frequency distribution of Leucoraja naevus (top) and Raja clavata (bottom), 
(2008–2015) caught off mainland Portugal (Division 9.a) by the polyvalent fleet (black line) and trawl 
fleet (grey line). Source: ICES (2017b).  

46 

 
 
 
 
 
Figure 3.6 (continued): Length–frequency distribution of  Raja brachyura (top) and Raja 
microocellata  (bottom) (2008–2015)  caught  off  mainland  Portugal  (Division  9.a)  by the 
polyvalent fleet (black line) and trawl fleet (grey line). Source: ICES (2017b). 

47 

 
 
 
 
 
 
 
 
 
3.6 

Species composition of skates in commercial landings 

There have been various published studies providing information on species composition 
of skates, and these studies can provide both historical (Steven, 1932; Holden, 1963; Du 
Buit,  1973;  Fahy  1989,  1991)  and  more  recent  perspectives  (Machado  et  al.,  2004; 
Figueiredo et al., 2007; Silva et al., 2012). 

The species composition of skates, can vary both seasonally and spatially. Some areas, 
such  as  the  southern  North  Sea,  have  a  comparatively  low  species  richness  of  skates, 
and  R.  clavata  is  by  far  the  main  species  encountered  (Ellis  et  al.,  2008;  Silva  et  al., 
2012;  Table  3.5).  In  contrast,  other  regions  (e.g.  Celtic  Sea)  have  a  greater  range  of 
skate taxa (Table 3.6). 

ICES WGEF has recently collated data for elasmobranch landings by nation (ICES, 2016). 
These  data  also  available  by  fleets,  although  the  data  supplied  are  to  varying  levels  of 
gear  type,  category  and  métier.  ICES  WGEF  has  regularly  noted  that  some  of  the 
species-specific information in official/national data are inaccurate, which can be due to 
misidentifications  or  coding  errors  (ICES,  2016,  2017b).  These  data  collated  by  ICES 
could be used to provide a more up-to-date synthesis of the species composition by ICES 
Division and gear.  

48 

 
 
 
 
  
 
Table 3.5: Species composition of skates in UK fisheries operating in the southern North Sea and eastern English Channel, based on 
reported landings and CEFAS observer programme (retained species only). Species denoted * are considered questionable records, and 
may be due to either misidentifications or coding errors. Source: Silva et al. (2012) 

Beam trawl 

Gill and tangle net 

Otter trawl 

Observer data 
2009 
- 
- 
- 
- 
- 
- 
0.4 
99.4 
- 
0.3 
- 
- 
100 

2008 
- 
- 
- 
- 
- 
- 
1.2 
97.1 
1.7 
- 
- 
- 
100 

2010 
- 
- 
- 
- 
- 
- 
- 
100.0 
- 
- 
- 
- 
100 

Reported landings 
2009 
- 
- 
- 
- 
- 
- 
3.4 
95.4 
0.3 
0.7 
0.1 
- 
100 

2008 
- 
- 
<0.1 
- 
- 
- 
4.6 
94.5 
0.1 
0.6 
0.1 
- 
100 

2010 
- 
- 
<0.1 
- 
<0.1 
- 
1.8 
97.6 
0.2 
0.2 
- 
<0.1 
100 

Observer data 
2009 
- 
- 
- 
- 
- 
- 
5.1 
39.9 
16.7 
7.9 
15.3 
- 
100 

2008 
- 
- 
- 
- 
- 
- 
- 
100.0 
- 
23.1 
- 
- 
100 

2010 
- 
- 
- 
- 
- 
- 
18.9 
72.0 
1.2 
- 
- 
- 
100 

Species name 

A. hyperborea* 
D. batis 
D. oxyrinchus* 
L. circularis* 
L. fullonica* 
L. naevus 
R. brachyura 
R. clavata 
R. microocellata 
R. montagui 
R. undulata 
R. alba 
TOTAL 

Reported landings 
2009 
1.0 
<0.1 
- 
- 
- 
0.3 
29.6 
53.0 
2.0 
13.7 
0.4 
- 
100 

2008 
- 
- 
- 
- 
- 
- 
30.8 
46.2 
4.2 
15.7 
3.1 
- 
100 

2010 
3.0 
- 
- 
- 
- 
0.3 
26.2 
55.9 
0.4 
14.1 
- 
- 
100 

Observer data 
2009 
- 
- 
- 
- 
- 
- 
24.5 
73.4 
- 
2.1 
- 
- 
100 

2008 
- 
- 
- 
- 
- 
- 
66.8 
33.2 
- 
- 
- 
- 
100 

2010 
- 
- 
- 
- 
- 
- 
30.1 
60.1 
3.7 
6.1 
- 
- 
100 

Reported landings 
2009 
- 
- 
<0.1 
- 
<0.1 
<0.1 
12.5 
84.2 
1.4 
1.6 
0.1 
0.1 
100 

2008 
- 
0.3 
0.8 
- 
<0.1 
- 
6.4 
90.5 
- 
0.1 
1.9 
- 
100 

2010 
<0.1 
0.3 
1.0 
<0.1 
0.1 
<0.1 
8.6 
86.8 
1.0 
2.3 
- 
- 
100 

49 

 
 
 
 
 
 
 
Table 3.6: Species composition of skates (Rajidae) in UK fisheries operating in the Celtic Sea, based on reported landings and CEFAS 
observer programme (retained species only). Species denoted * are considered questionable records, and may be due to either 
misidentifications or coding errors. Source: Silva et al. (2012) 

Beam Trawl 

Gill and tangle nets 

Otter trawl 

Species name 

Reported landings 

Observer data 

Reported landings 

Observer data 

Reported landings 

Observer data 

2008  2009  2010  2008  2009  2010  2008  2009  2010  2008  2009  2010  2008  2009  2010  2008  2009  2010 

A. radiata* 

D. batis 

D. nidarosiensis* 

D. oxyrinchus 

L. circularis 

L. fullonica 

L. naevus 

R. brachyura 

R. clavata 

R. microocellata 

R. montagui 

R. alba 

TOTAL 

0.5 

7.7 

- 

0.4 

2.9 

1.4 

0.6 

0.5 

- 

- 

1.0 

1.7 

0.3 

- 

- 

<0.1 

0.1 

0.7 

72.9 

78.8 

77.0 

4.7 

4.5 

5.1 

<0.1 

- 

5.6 

5.7 

5.8 

0.4 

- 

5.3 

6.4 

8.6 

1.6 

- 

- 

18.3 

- 

- 

- 

6.2 

73.7 

<0.1 

1.3 

0.3 

0.1 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

4.6 

93.2 

15.0 

82.6 

- 

0.6 

- 

- 

- 

- 

1.7 

2.4 

- 

- 

1.2 

0.5 

- 

- 

25.1 

<0.1 

- 

- 

3.0 

- 

37.7 

20.3 

3.0 

- 

- 

0.2 

41.6 

22.1 

9.0 

10.9 

21.9 

- 

- 

4.0 

- 

- 

- 

- 

- 

6.0 

22.2 

4.4 

28.8 

29.2 

9.0 

- 

- 

- 

- 

- 

- 

- 

4.5 

3.0 

46.9 

44.6 

1.0 

- 

- 

- 

- 

- 

- 

- 

90.9 

- 

- 

- 

- 

- 

- 

- 

- 

23.0 

59.7 

0.5 

0.4 

- 

9.1 

16.4 

- 

- 

- 

4.0 

20.6 

11.0 

0.1 

5.6 

30.3 

8.8 

- 

- 

2.8 

5.3 

1.8 

15.0 

47.7 

4.7 

- 

- 

<0.1 

- 

0.1 

30.1 

46.6 

4.4 

14.1 

16.6 

12.0 

4.8 

0.1 

0.6 

5.5 

0.7 

- 

5.7 

1.2 

- 

- 

- 

- 

- 

- 

- 

0.1 

60.4 

12.1 

25.5 

1.9 

- 

- 

- 

- 

- 

- 

- 

- 

8.8 

43.1 

41.8 

6.3 

- 

- 

- 

- 

- 

- 

- 

0.2 

37.3 

19.1 

40.3 

3.0 

- 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

100 

50 

 
 
 
 
 
 
4 

SURVIVAL 

4.1 

Background 

As  stated  in  STECF  2014  “Article  15  paragraph  2(b)  of  the  landing  obligation  allows  for  the 
possibility  of  exemptions  from  the  landing  obligation  for  species  for  which  "scientific  evidence 
demonstrates high survival rates"”. Two previous STECF (STECF-14-19 and STECF-15-01) reports 
have  reviewed  existing  information  on  survivability  of  discards,  including  skates  and  rays,  and 
have commented on factors that influence survivability. 

STECF (14-19) has provided guidance on best practice to undertake survival studies. EWG-13-16 
has identified three methodologies for conducting survival experiments (i.e. captive observations, 
vitality/reflex  assessments  and  tagging/biotelemetry  experiments).  STECF  has  identified  the 
gears  that  catch  skates  and  rays  and  has  classified  them  by  proportion  of  total  landed  catch  of 
skates  and  rays.  These  are  bottom  trawls,  gillnets  and  entangling  nets,  beam  trawls,  trammel 
nets  and  longlines.  Minimum  and  maximum  observed  survivability  rates  were  reported  for  rays 
and skates at the family/group level, by gear and country. STECF-15-01 confirmed in the findings 
of STECF-14-19, reporting that species of ray have discard survival rates between 64% and 79% 
across all gears. They also reported that discard rates vary with biological attributes and type of 
gears and handlings (ICES, WKMEDS 2014).  

STECF  reported  by  gear  type  and  by  area  (limited  to  ICES  Subareas  4–7)  for  which  no 
information  was  available  on  survivability  of  skates  and  rays.  STECF  suggested  that  these  gaps 
could  potentially  be  filled  by  comparing  studies  with  the  same  species  for  similar  gears  and 
similar  handling  procedures  to  determine  if  discard  survivability  rates  were  comparable  enough 
and therefore possibly transferable between areas.  

4.2 

Available information on survival rates of skates and rays 

EWG-17-10 was asked to “collate and review available information on the survival rates of skates 
and rays updating STECF 2014, producing a table of stocks/species versus  métier/fleet segment 
for each sea basin or TAC unit”.  

The table of discard survival rates per métier from STECF-01-15 was updated bringing the level of 
detail from family to species. Next to the survival rate of discarded fish, mortality at vessel and 
tow/soak duration were added in the table (Table 4.1).  

Only seven studies in European waters (highlighted in grey and blue in the table) were found and 
of  these  only  two  (Enever  et  al.,  2009;  Catchpole  et  al.,  2017)  had  estimated  survival  rate  for 
discards.  The  other  studies  reported  either  vitality  values  or  the  percentage  of  individuals  that 
survived after the observation period. No information on long-term survival rates after discarding 
is available in those studies. Studies carried out outside of European waters were also reported to 
determine whether it would be possible to use such information to fill in gaps on certain métiers 
used also in European waters. 

The  above  mentioned  studies  reported  an  effect  of  depth  (Endicott  and  Agnew,  2004),  sex 
(Endicott and Agnew, 2004; Laptikhovsky et al., 2004; Enever et al., 2009), catch mass (Enever 
et al., 2009), tow and soak duration (Ellis et al., 2008; Bendall et al., 2012; Mandelmann et al., 
2012)  with  the  level  of  survival/vitality  recorded.  It  would  thus  be  useful  to  obtain,  in  future 
studies, a quantification of the effects of some of those factors on the estimates of survival rates 
of discarded fish 

51 

 
 
EWG-17-10  notes  that  recent  studies  lead  to  the  revision  of  some  survival  rate  estimates 
previously  reported  (STECF-15-01).  Catchpole  et  al.  (2017)  re-estimated  discard  survival  in  UK 
waters reviewing the available data from previous studies applying the latest analytical methods 
to  obtain  more  robust  estimates.  They  found  that  previous  estimates  (Enever  et  al.  2009)  may 
have overestimated survival at discard for Raja brachyura (Table 4.1 in blue) therefore indicating 
that  more  robust data analysis  and  data  collection  are  still  needed  to  better estimate skate  and 
ray discard survival rates. 

EWG-17-10  notes  that  there  might  be  some  potential  to  increase  survival  of  discarded  fish  by 
improving handling. This could be done through projects aiming at improving communication with 
fishers and/or through specific training. 

Table 4.1 Estimates of survival at discard and mortality at vessel across gear types and species. 
Studies highlighted in grey and blue were from European waters outside the Mediterranean. 

SPECIES 

GEAR 

LOCATION 

REFERENCE 

OBSERVATION 
PERIOD 

SHORT TERM 
SURVIVAL (%) 

AT VESSEL 
MORTALITY (%) 

TOW 
DURATION OR 
SOAK TIME 

Leucoraja 
naevus 
Raja 
microocellata 
Raja brachyura 
Raja clavata 
Raja 
microocellata 

Leucoraja 
naevus 

Raja clavata 

Otter trawl 

Beam trawl 

Demersal trawl 
Longline 
Gillnets 
(inshore 
vessels): fixed 
and drifters 

Raja sp. 

Beam trawls 

Dipturus batis - 
complex 

Trammel nets 
and gillnets 

Raja clavata 
Raja brachyura 
Leucoraja 
naevus 

Demersal trawl 

Beam trawl 

Raja clavata 

Trammel nets 

Otter trawl 

Raja clavata 

Raja miratelus 

Bathyraja 
Psammobatis 
sp. 
Bathyraja 
brachiurops 
Bathyraja 
griseocauda 
Rhinoraja 
macloviana 
Rhinoraja 
magellanica 
Bathyraja sp. 
Psammobatis 
sp. 

Otter trawl 

VII g,f (U.K. - 
Bristol Channel) 

Enever et al. 
(2009) 

3 days 

2 days 

5 days 

NA 
NA 

NA 

Enever et al. 
(2010) 

Kaiser and 
Spencer (1995) 

Ellis et al. 
(2008) 

Depestele et al. 
(2014) 

3-4 days 

Bendall et al. 
(2012) 

NA 

Catchpole et al. 
(2017) 

See Enever et 
al. (2009) 

Catchpole et al. 
(2017) 

Electronic 
tagging 

Saygu and 
Deval (2014) 

2 days 

VII g,f (U.K. - 
Bristol Channel) 
Dulas Bay, 
North Wales 
(UK) 

NorthEast 
Atlantic; 
southern North 
Sea 

NorthEast 
Atlantic; North 
Sea 
NorthEast 
Atlantic; Celtic 
Sea 
Bristol Channel 

English western 
channel 

Southern North 
Sea 
Antalaya bay 
(Eastern 
Mediterranean) 

Squid trawl 

Falkland Islands 

Laptikhovsky 
(2004) 

3 hours 

52 

NA 

NA 

0 

0.6 
0 

2 (fixed); 0 
(drifters) 

3.2h 

3.1h 

3.9h 
3.9h 

5.5h 

0.5h 

0.5-1.5h 
2-4h 

overnight 
(fixed); 1-3h 
(drifters) 

NA 

0.17h; 1.5h 

6.6; 8.6 (higher 
at longer soak 
time) 

12-26h ; 36-48h 

See Enever et 
al. (2009) 

See Enever et 
al. (2009) 

NA 

2 

26 

NA 

NA 

NA 

NA 

33 

51 

55 
59 

67 

59 

NA 
NA 

NA 

72 

NA 

 57-69 
45 (22-65) 

34 (15-54) 

95 

81 

21 

71 

55 

0 

0 

60 

75 

60 

 
 
Amblyraja 
radiata 
Malacoraja 
senta 
Leucoraja 
ocellata 
Leucoraja 
erinacea 

Leucoraja 
ocellata 

Amblyraja 
radiata, 
Malacoraja 
senta, 
Leucoraja 
ocellata 
Amblyraja 
radiata, 
Malacoraja 
senta, 
Leucoraja 
ocellata 
Amblyraja 
radiata, 
Malacoraja 
senta, 
Leucoraja 
ocellata 

Otter trawl 

Gulf of Maine 
(USA) 

Mandelman et 
al. (2012) 

3 days 

4 days 

5 days 

6 days 

81; 77 

41; 40 

92; 91 

86; 78 

<1 

15-20mins; 2-
4h 

Scallop dredge 
fishery 

Southern Gulf 
of St. Lawrence 
(Canada) 

Benoit et al. 
(2010)b 

2 days 

62.5-100 

NA 

NA 

Bottom trawl 

Longline 

Southern Gulf 
of St. Lawrence 
(Canada) 

Benoit et al. 
(2010)a 

2;>3 days 

42-100 

Bottom trawl 

Southern Gulf 
of St. Lawrence 
(Canada) 

Benoit et al. 
(2012) 

2;>4 days (72h) 

50 

30 

NA 

NA 

1-2h 

0 

NA 

65 (43-80) 
(total survival 
estimate) 

75 (1200m-
1300m depth)-
46 (1300m-
1500m)-
24(1500m-
2000m); 68 
(males) - 34 
(females) 

Raja sp. 

Longline 

South Georgia 

Endicott and 
Agnew (2004) 

12 hours 

Leucoraja 
erinacea 
Leucoraja 
ocellata 
Zearaja 
maugeana 
Raja whitleyi 
Leucoraja 
eglanteria 

Scallop dredges 

NorthWest 
Atlantic 

Rudders et al. 
(2015) 

3 days 

Gillnets 

Tasmania 

Bottom longline 

Gulf of Mexico 

Lyle et al. 
(2014) 

Scott-Denton et 
al. (2011) 

NA 

NA 

50.9 

34.8 

>87.2 

NA 

NA 

0-9 (higher as 
soak time 
increases) 

0.17h; 1.5h 

NA 

2-24h 

4 

0.9-32.2h 

4.3 

Data  extrapolation  to  fleets  segments/métiers/species  not  covered  by  the 
available studies 

EWG-17-10  was  asked  to  “consider to  what extent  information  from  one  métier /  fleet  could  be 
extrapolated to other fleets, detailing the criteria to do so. If this is not possible, then the working 
group  is  requested  to  conduct  a  gap  analysis,  detailing  what  information  would  be  required  to 
consider  extrapolation  and  high  survivability  exemptions  across  all  species  of  skates  and  rays, 
métiers and fleet segments per sea basin or TAC unit, whichever is more suitable”. 

In  2015,  STECF-15-01  listed  a  series  of  fisheries  (area  and  gear  combination)  for  which  it  was 
unable to identify skates and rays survival data: 

  TR1 and TR2 in North Sea (IVab); 
  GT1 in North Sea (IVc); 

53 

 
 
 
  BT, GT1 and TR2 in the Eastern Chanel (VIId); 
  TR1 and TR2 in Western Channel (VIIe & VIIh); 
  BT1 and GN1 in the Bristol Chanel (VIIfg); 
  GN1 and TR1 in the Irish Sea (VIIa) and; 
  TR1 and TR2 in West of Scotland (Vb & VIab). 

Since  then,  estimates  of  survival  rates  have  only  been  provided  for  the  métier  GT1  in  the 
southern North Sea (Catchpole et al., 2017) and, for all other gear and area combinations, there 
is still a lack of information on discards survival rates. 

STECF-15-01  noted  that  “for  many  of  the  area/gear/species  combinations  where  there  is  an 
absence of survival information, it may be worthwhile considering whether there are studies with 
similar  gears  and  the  same  species  from  other  areas,  the  results  from  which  could  be 
extrapolated from”.  

However,  STECF  noted  “that  such  analogies  should  not  be  applied  across  gear  types  (e.g. 
assuming  that  the  survival  rates  from  longline  fisheries  would  be  comparable  with  gill  nets  for 
example”).  In  a  more  recent  review,  Catchpole  et  al.  (2017)  reached  a  similar  conclusion  and 
reported  that  due  to  the  limited  number  of  survival  rate  estimates  available  in  the  literature,  it 
may be difficult for the moment to extrapolate values across  métiers and that more studies are 
needed  to  cover  a  larger  palette  of  gears,  species  and  areas.  To  both  increase  the  coverage  of 
gear, area and species and improve current estimates, a data review and analysis, on the model 
developed  by  Catchpole  et  al.  (2017)  on  UK  waters  should  be  extended  to  other  areas.  Such 
review should also highlight the main data gaps where particular efforts are needed. 

The compilation of available studies presented in Table 4.1 confirms the limited number and large 
variability  of  estimates  of  discard  survival  rates.  It  also  shows  that  those  estimates  are  not 
always comparable, as they focus on different métiers, areas and species and often use different 
methods to collect and analyse data. For instance, three studies (Ellis et al., 2008; Enever et al., 
2009;  Saygu  and  Deval,  2014)  relates  to  the  same  species  (Raja  clavata)  and  the  same  gear 
(demersal trawl), but in different areas, with different tow durations and observation periods. The 
estimates obtained are affected by different parameters and vary from 57 to 87 %.  EWG-17-10 
thus  considers  that  it  would  be  premature  to  envisage  any  extrapolation  of  survival  rates 
estimates across métiers before more work is carried out as explained above. This consideration 
is  also  valid  for  the  extrapolation  of  such  estimates  across  species  and/or  fleets  segments.  The 
different  species  may  have  different  biological  characteristics,  which  may  affect  survival  (body 
size  (as  an  adult),  skin  hardness,  body robustness);  the  type  and  operation  of  gears  (e.g.  soak 
time/tow  duration);  the  deck  handling  procedures  (e.g.  time  taken  to  sort  the  catch);  and  the 
broad  environmental  conditions  that  may  vary  across  fleet  segments.  Another  approach  to 
estimating  mortality  of  discards,  could  be  to  carry  out  a  retrospective  analysis  of  the  data  from 
tagging experiments which has been collected in the past decades. 

4.4 

Conclusions 

Discard  survival  estimates  are  needed  to  support  future  requests  regarding  the  exemption 
measure  associated  with  the  landing  obligation.  Currently,  the  estimates  available  only  cover  a 
limited  number  of  métiers,  areas  and  species,  which  are  caught  by  commercial  fisheries. 
Information  in  support  of  high  survival  exemption  requests  are  limited  and  extrapolation  of 
estimates  of  survival  rates  across  métiers  rather  difficult.  Furthermore,  the  available  estimates 
are  limited  to  short  term  survival  rates  and  are  still  considered  uncertain  (due  for  instance  to 
limited sample sizes and duration of experiments).  

To  highlight  the  data  gaps  on  species  and  métiers  by  area  which  limit  improvement  in  current 
survival  estimates,  EWG-17-10  suggests  that  a  review  and  analysis,  based  on  the  model 

54 

 
 
developed by Catchpole et al. (2017) on UK waters should be extended to other areas. It needs 
to be stressed that in order to allow easy comparisons between studies and simplify validation, a 
standardized  data  collection  procedure  and  analysis  should  be  followed.  Further  data  collection 
using  tagging  technologies  (e.g.  conventional,  electronic,  satellite,  acoustic)  should  be 
encouraged when considered appropriate to provide better estimates of both short and long-term 
survival.  

Finally, it would be important to further encourage good practice on fish handling when discarded 
alive. This could be done through projects aiming at improving communication with fishers and/or 
through training. 

5 

SELECTIVITY 

Typical gear-based technical measures for towed gears such as increased codend mesh sizes and 
square  mesh  panels  are  considered  ineffective  in  increasing  size  selectivity  for  skates  and  rays 
because their large, flattened body shape prevents escape once inside fishing gears (Ellis et al., 
2016).   

Increasing codend mesh sizes to the extent required for reducing the catches of small skates and 
rays  could  be  prohibitive  given  the  resulting  losses  of  marketable  catches of  other  species.  This 
partly  explain  why  research  into  increasing  size  selectivity  for  such  species  has  been  limited. 
Enever et al. (2010) did investigate the effects of different configurations of codend construction 
and  mesh  size  on  the  survival  of  skates,  which  showed  changing  from  80  mm  diamond  to  100 
mm square mesh in the codend improved the condition of skates, and hence survival of discarded 
individuals.  However,  there  is  no  indication  from  this  study  that  size  selectivity  was  anyway 
improved for skates and rays.  Experiments carried out in the mixed fisheries in the Celtic Sea by 
France  using  100mm  T90  codends  with  120mm  square  mesh  panels  compared  to  standard 
diamond mesh codend likewise did not show any increases in size selectivity for skates and rays 
(Fiche et al., 2017).  

Meillat et al., 2011 reported on trials in the early 1990s with a prototype semi-rigid grid placed in 
the bottom panel of a standard demersal trawl tested in the Bay of Biscay. The objective of this 
trail  was  primarily  to  reduce  the  catches  of  small  anglerfish  and  megrim.  These  trials  showed  a 
reduction in the catch of Cuckoo ray below 40cm of around 55%. The majority of rays released 
were below 32cm.  No further trials are reported with this type of grid device.  

There have been a number of studies of selective gears that have indirectly shown impossible to 
reduce  the  catches  of  skates  and  rays.  None  of  these  gears  increase  size  selectivity  but  simply 
reduce the catch of skates and rays across the whole size range. These can be divided into: 

1.  Sorting grids and By-catch Reduction Devices (BRDs) 
2.  Escape panels and separator trawls 
3.  Other Trawl gear modifications  

The  following  is  a  short  review  of  the  relevant  work  carried  out  with  these  gears  which  have 
shown reductions in catches of skates and rays. 

5.1 

Sorting grids and By-catch Reduction Devices (BRDs) 

The use of rigid sorting grids is now common practice in a multitude of fisheries and in particular 
in shrimp fisheries.  In many of these fisheries such grids have been demonstrated to reduce the 
catch  of  skates  and  rays  in  a  number  of  bottom  trawl  fisheries  (Brothers,  1991;    Hartill  et  al., 
2016; Lomeli & Wakefeld, 2013; Cosgrove et al., 2016; Willems et al., 2016). In some cases (i.e. 
Canadian  Pandalus  shrimp  fisheries)  skate  bycatch  has  been  reduced  to  almost  zero  (Brothers, 

55 

 
 
1991)  although  generally  in  such  fisheries  skate  bycatch  is  unwanted  and  the  species 
encountered have no or very low commercial value.   

The  results  of  trials  reported  by  Willems  et  al.,  2016  in  a  trawl  fishery  for  seabob  shrimp  in 
Suriname showed that the size, morphology and behaviour of skates and rays are key factors in 
understanding the potential benefits of the various excluder devices. In these trials the grids used 
tended to facilitate the escape of larger species, but showed less of a reduction in the catches of 
juveniles and smaller-bodied species.  

Brewer  et  al.  (2006)  examined  the  catches  of  prawn  trawls  fitted  with  turtle  excluding  devices 
(TED) and by-catch reduction devices (BRD) to reduce unwanted bycatch in prawn fisheries. This 
study  reported  that  nets  with  TEDs  or  combined  TED–BRDs  successfully  reduced  ray  bycatch, 
with  upward-excluding  TEDs  more  effective  for  reducing  shark  catches.  The  use  of  trawls  with 
only BRDs was less successful.  

While most of these trials show sorting grids and similar type devices effective at reducing skates 
and  ray  bycatch,  there  is  evidence  that  elasmobranchs,  especially  large  batoids,  can  clog  grids 
(Isaksen  et  al.,  1992;  Lomeli  &  Wakefeld,  2013).  This  can  compromise  the  retention  of  target 
species and act as a disincentive for fishermen from using such systems voluntarily).  

5.2 

Escape panels 

There  are  have  been  several  trials  with  gears  fitted  with  escape  panels  placed  in  the  bottom 
panels  of  trawls  which  have  shown  reductions  in  skate  and  ray  bycatch.  None  of  these 
experiments have specifically designed to reduce skate and ray bycatch but have noted this as an 
outcome  from  such  trials.  Anon  (2011)  reported  on  trials  in  the  squid  fishery  off  Massachusetts 
with  a  modified  trawl  that  was  constructed  with  two  rows  of  32”  mesh  (~800  mm)  in  the  belly 
section of the trawl. While no quantitative results were reported, it was observed that the number 
of skate was drastically reduced when using the experimental net.   

Similar types of release panels have been tested in Scotland as reported by Kynoch et al. (2009,  
2010).  In  these  experiments  a  range  of  diamond  mesh  panels  of  300mm,  600mm  and  800mm 
were placed in the bottom sheet of demersal trawls. The main objective was to reduce the catch 
of  cod  but  there  were  indications  that  catches  of  rays  were  decreased  significantly.  In  this  case 
much of the ray catch was of marketable species.   

5.3 

Trawl gear modifications 

There  has  been  considerable  research  into  developing  trawl  modifications  that  use  the  natural 
behaviour of fish in trawls to sort different components of the catch into separate parts of a trawl 
and allow them to be treated in different ways. Main and Sangster (1982) showed in experiments 
with  a  modified  trawl  fitted  with  a  horizontal  separator  panel  that  it  was  possible  to  sort  low 
swimming species such as Nephrops, flatfish and skates and rays from higher swimming species 
such as haddock and whiting. In these initial trials with this separator trawl, 100% of the catch of 
skates  and  rays  was  retained  in  a  lower  codend.  Trials  carried  out  by  BIM  in  Ireland  (Anon., 
1997)  with  a  similar  designed  separator  trawl  showed  that  88%  of  catches  of  spotted,  blonde, 
cuckoo and thornback ray were sorted into a lower codend.  It was noted, though, that any rays 
that were retained in the top codend tended to be larger specimens.  In these trials the objective 
was  not  necessarily  to  reduce  the  catch  of  bycatch  species  but  simply  to  sort  catches  in  to 
different components.  

56 

 
 
 
Using  a  similar  approach  relating  by  exploiting  behaviour  differences  between  species  to  reduce 
unwanted  bycatch,  fishermen  in  New  England  in  collaboration  with  the  net  manufacturers 
Superior Trawl, and fishery specialists developed the Eliminator TrawlTM (Beutel et al., 2008). The 
goal  of  this  trawl  design  was  to  reduce  cod  bycatch,  while  retaining  catch  of  targeted  haddock.  
The  trawl  is  essentially  a  high  opening  demersal  trawl  with  large  mesh  sections  in  the  top  and 
bottom panels of the trawl and cutaway bottom wings that allow low swimming fish to escape like 
skates and rays, cod and flatfish to escape. Christensen (2014) reported that that, based on the 
work  in  New  England,  the  Eliminator  Trawl  was  found  to  have  a  significant  impact  on  reducing 
skate bycatch. The control net caught primarily skates, haddock, and winter flounder. The results 
from  the  trials  carried  out  showed  catches  from  the  Eliminator  Trawl  were  reduced  by  98.6%, 
totalling 258kg compared to 18,956 kg in the standard trawl gear. While not the main species of 
interest  in  Beutel  et  al.’s  (2008)  study,  the  Eliminator  Trawl  had  the  most  significant  impact  on 
skate bycatch of any bycatch species, while retaining similar catch levels for haddock.  

Revill  and  Horan  (2008)  similarly  report  of  reductions  in  bycatch  of  rays  in  trials  using  an 
Eliminator style trawl in the North Sea. In these trials a 43% reduction in catches of a range of 
non-commercial  species  including  unspecified  species  of  rays  was  observed.    Reeves  and 
Armstrong  (2009)  report  on  further  trials  with  an  Eliminator  type  trawl  in  the  North  Sea  saithe 
fishery. Several species of rays including cuckoo ray, common skate and starry ray are a bycatch 
in this fishery (both wanted and unwanted).  These trials again showed reductions in the catches 
of all these species although it also significantly reduced the catches of saithe. 

McHugh  et  al.  (2017)  reported  on  more  recent  trials  with  a  modified  trawl  with  a  raised  fishing 
line.  Raising  the  fishing  line  involved  lengthening  the  droppers  between  the  fishing  line  and  the 
ground  gear  to  approximately  1m  and  effectively  creating  an  escape  opening  for  bottom 
swimming fish to escape in the gap between the fishing line and the footrope. The main aim was 
to  reduce  the  catch  of  cod  while  maintaining  the  catch  of  haddock  and  whiting.  This  gear  was 
tested  in  the  mixed  demersal  fishery  in  the  Celtic  Sea  and  in  which  mixed  rays  are  a  bycatch. 
These  trials  showed  a  reduction  in  total  ray  catch  of  80%.    These  are  similar  results  to  those 
reported by Bayse et al. (2016) who tested a modified squid trawl with a drop-chain groundgear 
setup. The objective of this trial was to reduce the bycatch of finfish in the Nantucket Sound squid 
fishery.  They  reported  that  90%  of  skates  encountered  avoided  entering  the  trawl  and  escaped 
under the fishing line and based on video analysis results concluded that the drop-chain trawl was 
effective at allowing skates to escape 

Kynoch et al. (2015) showed that not using a tickler chain can reduce the catch of sharks, skates 
and  rays  in  mixed demersal  trawl  fisheries in  the North  Sea.  In  these  trials  the  presence  of  the 
tickler chains increased the catch of skates and rays by a factor of 3.6.  However, in this instance 
catches of anglerfish Lophius spp., one of the main target species in the fishery, were significantly 
reduced suggesting in this fishery that removing tickler chains would not be a measure supported 
by the fishing industry. 

5.4 

Gillnets and longlines 

For  static  gears  the  options  for  reducing  bycatch  are  limited  and  there  have  been  few  such 
studies to date that have investigated modifications to reduce bycatch of skates and rays.  Based 
on the characteristics of the species and the operation of such gears, potential bycatch mitigation 
measures in gillnet fisheries could include spatial and temporal restrictions, restricted lengths of 
net, limiting soak times, changes to mesh size, hanging ratio and height of the net and modifying 
the thickness and colour of netting material (Thorpe & Frierson, 2009; Baeta et al., 2010). These, 
however,  remain  unproven  and  indeed  in  many European countries, large mesh entangling nets 
with  relatively  long  soak  times  are  used  specifically  to  target  rays.  On  the  whole  these  are 
selective fisheries given the size of mesh used and that the fisheries are concentrated in areas of 
abundance.   

57 

 
 
In  longline  fisheries  there  are  limited  options  for  reducing  unwanted  catches.  There  have  been 
numerous  publications  on  the  potential  use  of  magnets  and  electropositive  metals  attached  to 
longlines to reduce bycatch of elasmobranchs. According to the review by Favaro & Côté (2015), 
such devices remain unproven. 

5.5 

Conclusions 

• 

Improving  the  size  selectivity  of  towed  gears  for  skates  and  rays  is  difficult  due  to  their 
morphology. There is only limited evidence from trials carried out by France with a type of 
flexible sorting grid that showed size selectivity for cuckoo ray could be increased. 

•  There  are  numerous  trials  with  sorting  grids  that  have  shown  that  catches  of  skates  and 
rays  can  be  reduced.  In  most  cases  these  devices  have  been  tested  in  fisheries  where 
skates  and  rays  are  classified  as  unwanted  catches  due  to  the  species  involved  being  of 
low or no commercial value. In certain circumstances the effectiveness of such devices has 
been reduced due by larger skates or rays blocking or clogging up the grid compromising 
the retention of target species. 

•  Several trials have demonstrated that installing large mesh panels in the bottom panels of 
trawls can reduce skate and ray bycatch. As with sorting grids in some cases this has been 
a favourable outcome as the species are classed as unwanted bycatch. However, in other 
fisheries (e.g. mixed demersal fisheries in the North Sea) this is a negative outcome as the 
skates and rays catch is valued by the fishermen operating in the fishery. 

•  Trawl modifications such as the use of the EliminatorTM trawl as well as the use of trawls 
with raised fishing lines have also been shown effective at reducing the bycatch of skates 
and  rays.  Such  trawl  designs  exploit  behaviour  differences  between  species  to  reduce 
unwanted  bycatch.    Removing  tickler  chains  has  also  be  shown  to  reduce  skate  and  ray 
catches  in  mixed  demersal  fisheries  in  the  North  Sea  but  the  removal  of  tickler  chains 
significantly reduce the catch of other target species, particularly anglerfish, in this fishery. 
•  There  are  limited  ways  of  increasing  selectivity  in  gillnet  and  longline  fisheries  and  few 
trials  have  been  carried  out  from  which  to  draw  any  conclusions  as  to  whether  this  is 
possible or not.  

•  Potential  bycatch  mitigation  measures  in  gillnet  fisheries  could  include  spatial  and 
temporal restrictions, restricted lengths of net, limiting soak times, changes to mesh size, 
hanging  ratio  and  height  of  the  net  and  modifying  the  thickness  and  colour  of  netting 
material. None of these have been tested to any degree and in any cases gillnet fisheries 
for  skates  and  rays  tend  to  be  targeted  and  conducted  with  large  mesh  gillnets  making 
them selective in some regards.  

• 
•  The  overall  conclusion  is  that  it  is  difficult  to  increase  size  selectivity  for skates  and  rays 
but  there  are  a  number  of  gear  modifications  that  have  been  shown  to  be  effective  at 
reducing bycatch.  The adoption of such gears is dependent on whether the skates and ray 
species involved have a commercial value and the availability of fishing opportunities that 
allows  them  to  be  landed.  Where  such  species  are  considered  as  part  of  the  marketable 
catch then there is little incentive to reduce bycatch as to do so would represent a loss of 
income.  However,  in  a  choke  species  scenario,  where  the  quota  for  skates  and  rays  is 
exhausted and the only option for a vessel to continue fishing in a specific fishery is to fish 
without catching skates and rays then such gears may be considered an option.  

6 

MANAGEMENT MEASURE EVALUATIONS 

6.1 

TAC based management measures 

Several  types  of  TAC  based  management  measures  have  been  reviewed  (Table  6.1).  They 
include: 

58 

 
 
  
• 

• 

• 

• 

Generalized skate and rays TACs: This is the current method of TAC setting for 
skates and rays. The objective is to limit the combined total allowable catch of 
all stocks of skates and rays across several management areas. 
Generalized TAC with sub-TACs for particular stocks: the objective is to restrict 
the total allowable catch by management areas for all stocks of skates and rays 
combined  with  specific  sub-TACs  for  some  particular  stocks.  The  choice  of  the 
particular  stock  could  be  based  on  several  criteria  (e.g.  the  more  vulnerable 
stocks or the more important in terms of catches or revenues) 
TAC  by  genus:  the  objective  is  to  restrict  total  allowable  catch  at  the  scale  of 
genus of skates and rays (Raja and Leucoraja). 
TAC by stocks (from ICES advices): the objective is to limit total allowable catch 
at the individual stock level for skates and rays by management area as defined 
by the ICES stocks advice. 

6.1.1  Information needed 

For most stocks of skates and rays, ICES already produce advice that allows the setting of TACs. 
However, this advice is currently a landing advice. In order to set TACs on a catch basis, it will be 
necessary to get better estimates of dead discards. This implies improvement in both estimates of 
discards and survival rates of discarded fish. 

Despite  improvement  in  recent  years,  recurring  misidentification  at  species  level  and  uses  of 
generic  categories  occurs  in  the  reporting  of  landings  and  discard  data.  It  is  thus  important  to 
improve  species  identification  and  increasing  information  on  catches  and  fisheries  may  imply 
adjustments of the DCMap in terms of the skates and rays data collection.  

In  the  case  of  generalized  TACs  with  sub-TAC  for  particular  stocks,  it  is  worth  noting  that  the 
selection  criteria  for  sub-TAC  stocks  may  have  direct  consequences  on  the  effectiveness  of  the 
management  method  and  buy-in  by  stakeholders.  This  would  be  facilitated  if  the  criteria  were 
developed in a transparent, collegial and revisable way (e.g. stocks targeted, stocks with poor or 
unknown status, stocks with low level of landed, etc…). A sub-TAC would probably be more useful 
for species where there are targeted fisheries and reasonable catch data. 

For all TAC management options, building performance indicators will require information on the 
level  of  F  and  SSB  and  the  definition  of  reference  points.  Proxies  could  be  used  until  suitable 
metrics can be estimated (e.g. stock size indicators as currently used by ICES for several stocks 
of skates and rays). 

6.1.2  Pros and cons 

It is evident that the level of control of fishing mortality by stock will vary between TAC allocation 
method and it is expected that the capacity of controlling F will be higher in the case of TACs set 
at  stock  level  and  lower  in  the  case  of  TACs  combining  all  species.    In  the  case  of  aggregated 
TACs  combining  stocks  with  different  status,  the  management  measure  may  not  offer  adequate 
protection for stocks that require reductions in F and conversely, may limit catch opportunities for 
stocks in good condition. Additionally, in the case of a generalized TAC with sub-TACs, if a sub-
TAC  is  restrictive,  this  may  result  in  an  increase  in  fishing  pressure  on  the  other  generalized 
stocks of the same area, once the sub-TAC level has been reached for the specific stock(s). 

Control  and  enforcement  will  also  vary  depending  on  the  TAC  management  options.  It  can  be 
expected  to  be  easier  to  implement  in  the  case  of  a  generalized  TACs  considering  it  does  not 
required  species-specific  or  genus  information,  as  species  identification  is  an  issue  with  some 
species  of  skate  and  ray.  This  may  still  be  a  problem  for  TACs  set  at  stock  level  although  this 
identification  has  been  made 
could  be  mitigated  once 

improvement 

in  species 

59 

 
 
(training/awareness raising with fishermen). In any case, it must be noted that adding more TACs 
(going  from  a  generalized  TAC  system  to  a  stock  based  TAC)  may  add  extra  monitoring 
requirements. The fact that skates and rays are mainly caught by mixed fisheries targeting other 
species needs also to be taken into considerations. 

In all cases, some incentives for misreporting exist, although this could be expected to be much 
less important in the case of a generalized TAC. This can be due to misidentification but also to 
deliberate  misreporting  of  TAC  catches  once  quota  allocation  is  reached.  Additionally, 
misreporting can still occur for prohibited species although is rare as catches of such species tend 
to be limited. 

All TACs management option can produce, to a various degree, the dangers of skates and rays of 
being choke species. This is possibly highest for TAC by stocks as more TACs need to be defined. 
This effect will be linked to the exemptions granted in the landing obligation as well as other tools 
and  flexibility  measures  available  under the  CFP.  The  survival  rate  per species,  métier and  area 
will be of particular importance. 

6.2 

Landing trip limits 

This management  measure  would limit  the  quantity  of  a (or several)  selected stock(s)  on  a  trip 
by trip basis. The measure is considered here outside a quota limit system.  

6.2.1  Information needs 

Landing  trips  limits  requires  information  on  catch  (or  landings)  weights  by  trip  for  each  métier 
together  with  discard  survival.  Data  on  landings  by  trip  is  available  but  length  distributions  of 
landings/discards  are  only  available  for  some  fisheries  from  at-sea  observer  programmes. 
Building performance indicators will require information on the landings or catch data by trip (to 
verify compliance) and on F and SSB to assess the stock status.  

6.2.2  Pros and cons 

This  measures  can  potentially  control  fishing  mortality  by  deterring  the  development  of  target 
fisheries for species that survive discarding. It may however encourage high grading by retaining 
larger  (mature)  individuals.  If  the  survival  rate  of  the  species  selected  is  low,  this  measure  will 
not  control  F.  Control  and  enforcement  can  be  easy  at  point  of  landing  but  can  be  more 
problematic  if  the  fishery  operates  from  a  large  number  of  ports.  Absolute  limits  in  kg  per  trip 
would  be  easier  to  enforce  than  percentages  of  catch.  There  might  be  issues  with  species 
identification  as  for  other  management  measures  based  on  catch/landing  limits.  There  is  also  a 
need for better definition of conversion factors for processed to live weight (including the option 
to land individual whole/gutted) 

Poor knowledge on the spatial-temporal distribution and abundance of some lesser-known species 
in  relation  to  fleet  dynamics  (e.g.  is  there  an  area  of  high  local  abundance  in  relation  to  some 
specific  fleets)  may  be  a  source  of  uncertainty  in  the  implementation  of  such  measure  together 
with  discard  survival  rates.  Furthermore,  the  selected  level  of  the  landing  limit  and  its  market 
value could potentially affect compliance.  

6.3 

Effort control 

In a fishing effort management system, fishing is limited by the amount of effort exerted and not 
by  the  amount  of  fish  caught.  A  prerequisite  is  however  that  the  relation  between  fishing  effort 
and fishing mortality of a species is known. In an effort regulated system the fishing mortality can 

60 

 
 
be,  for  instance,  limited  by  the  number  of  fishing  vessels  (expressed  as  kilowatt  or  gross 
tonnage) multiplied by their fishing days deployed (Lovgreen et al., 2009). 

6.3.1  Information needs 

Effort  management  tools  require  an  appropriate  measure  of  effective  unit  of  fishing  effort  to 
account for vessel size/power and gear effectiveness, effort information spatially discriminated by 
métier, fleet dynamic and catch composition data. This information is already partially available in 
fleet  registers,  in  the  STECF  FDI  database  by  métier,  and  from  logbooks  and  observers 
programmes,  although  discard  data  for  skates  and  rays  is  sparse  and  information  on  dead 
discards is missing. 

6.3.2  Pros and cons 

It must firstly worth noting that while this management method has been used by the European 
Commission  over  recent  years,  there  is  currently  a  tendency  to  move  away  from  effort  as  a 
management method. 

If  there  is  correlation  between  fishing  mortality  (F)  and  effort,  control  of  fishing  effort  could  be 
used  as  a  useful  measure  to  manage  fishing  mortality.  However,  technological  creep,  capacity 
increases  and  fishers  know  how  all  can  lead  to  higher  fishing  efficiency  with  the  resulting  effect 
that F will not necessarily be controlled by effort. In addition, effort limitations may change fleet 
dynamics  with  fisheries  changing  to  other  métiers,  which  could  also  lead  to  changes  in  F.  The 
bycatch of skates and rays in mixed fisheries might increase, particularly if 'abundance hotspots' 
and fleet dynamics are not taken into account in the design of the system. 

Controlling  a  fishing  effort  system  is  somewhat  straightforward  as  the  amount  of  effort  exerted 
can  be  easily  measured  by  days  away  from  port  associated  to  VMS  data;  this  may  however  be 
less  appropriate  for  static  gears  or  small  vessels  with  no  VMS  system  on  board.  An  additional 
advantage  is  that  there  is  no  incentive  for  misreporting  catches  as  there  are  no  constraints  on 
catches. It also provides the flexibility for fishing operators to manage their activity according to 
live  occurrence  of  catches  and  market  demands.  However,  measuring  (and  limiting)  increase  in 
fishing  efficiency  is  extremely  difficult,  and  thus  possibly  rendering  this  measure  ineffective  in 
many  fisheries.  Furthermore,  managing  skates  and  rays  by  effort  while  other  species  caught  in 
the same fisheries would be managed by TACs may be very complex. 

6.4 

Landing sizes  

This management could be used to protect juveniles with a minimum conservation reference size 
(mcrs) and/or reproducers with a maximum landing size. It could be set by species or by group of 
species and/or by area although it would be preferable to avoid setting different size in different 
areas. The size measure could be set by length or width and should be harmonised across regions 
and  species.  However,  it  should  be  noted  that  this  management  measure  would  be  in 
contradiction with the landing obligation if implemented in association with catch limits, except in 
the case of exemptions for high survival. In case of no exemption, the introduction of a maximum 
landing  size  might  be  problematic.  The  landing  obligation  uses  a  mcrs  to  differentiate  between 
fish  that  can  be  used  for  human  consumption  (above  mcrs)  and  fish  that  cannot  (below  mcrs); 
under  the  LO,  all  fish  have  to  be  landed.  It  is  thus  not  clear  how  such  rationale  could  be 
implemented with a maximum size (illegal to sell fish above the maximum size) and if this would 
work. 

61 

 
 
6.4.1  Information needed 

Targeted  sizes  should  be  identified  at  species  level  using  biological  parameters.  Length  at 
maturity  and  first  maternity,  and  growth  are  needed  to  implement  the  measure  on  juveniles. 
Length at first and full maternity, fecundity at length, spawning periodicity, growth and longevity 
are needed for reproducers, especially large females with higher reproductive rate. Data needed 
to  define  minimum  size  are  readily  available  even  if  they  are  not  always  published  and  just 
available in grey literature. This is less the case for maximum landing size where data availability 
is limited. Life history parameters are also limited for most species.  

This type of management and landing sizes definition would ideally take place  in a participatory 
modelling  process  with  stakeholders  and  should  take  into  account  the  benefit  for  the  stock  and 
the  socio-economic  impact.  Catch  data  (size  composition  by  métier  at  a  level  6,  to  include  for 
instance gill net mesh size), fishing practice data (retention ogive) and survivorship by métier are 
needed  to  assess  their potential  benefit.  Length/weight  relation  and  market  data  (price  per  size 
grade) are also needed to assess their potential socio-economic impact by métier.  

Defining  performance  indicators  will  require  information  on  the  actual  level  of  F  and  SSB  and 
defined  reference  points.  Proxies  can  however  be  used  until  suitable  metrics  can  be  estimated 
(e.g.  stock  size  indicators  as  currently  used  by  ICES).  Alternative  indicators  could  be  the 
length/age  composition  of  the  catch  or  average  length  of  catches  in  order  to  measure  the 
proportion  of  the  undersized/oversized  fraction  in  the  total  catch.  This  metric  is  however  very 
sensitive  to  population  structure  and  may  give  an  overall  positive  or  negative  impression  of 
whether it is working or not. 

6.4.2  Pros and cons 

Minimum  conservation  reference  sizes  can  control  fishing  mortality  on  juveniles,  furthermore  it 
may  incentivise  better  size  selection  by  gear  selectivity  or  avoiding  areas  with  high  densities  of 
juveniles. Regarding gear selectivity improvements, options may be relatively limited as already 
mentioned in Section 5. High grading can lead to increased exploitation of mature females.  

Maximum  landing  sizes  can  control  fishing  mortality  on  reproducers,  furthermore  it  may 
incentivise  better  size  selection  by  gear  selectivity  or  avoiding  times/areas  with  high  density  of 
large  reproducers,  but  low  grading  can  lead  to  increased  exploitation  of  juveniles.  Limited 
knowledge on annual egg production and its contribution to recruitment is a source of uncertainty 
to assess the benefit of this measure. Socio-economic impact is expected to be largely negative 
as bigger fish are more valuable. This suggests it would be difficult to achieve agreement on such 
measures. 

Combination  of  minimum  and  maximum  landing  size  can  control  the  fishing  mortality  of  both 
juveniles  and  reproducers.  Socio-economic  impact  of  maximum  landing  size  is  expected  to  be 
largely negative as bigger fish are more valuable, suggesting that it would be difficult to achieve 
agreement on such measures.  

The efficiency of management based on landing sizes will depend on the level of discard survival 
rate and if an exemption from the landing obligation is implemented. Good handling practice can 
increase survivorship and consequently the benefits of this type of management. 

If  the  landing  sizes  are  defined  by  group  of  species  (“one  size  for  all”),  which  could  make  the 
implementation of the measure easier for fishermen, this can lead to changes in species targeting 
and  not  be  beneficial  to  the  smaller  or  larger  bodied  species.  It  may  thus  not  control  mortality 
adequately per species. If set by stock, it may be compromised by species identification issues. 

62 

 
 
Such  measures  would  be  relatively  easy  to  implement  from  a  control  and  enforcement 
perspective  provided  the  level  of  inspection  is  adequate.    It  only  requires  size  measurement 
inspections,  which  can  be  difficult  if  skates  and  rays  are  winged  at  sea.  These  measures  could 
possibly  increase  dead  discarding  which  is  currently  difficult  to  quantify  as  information  on  dead 
discards is missing for most species. 

6.5 

Gear selectivity 

Gear  selectivity  improvement  could  be  used  to  avoid  or  reduce  the  catch  of  a  species  (for 
instance  unwanted  or  prohibited  species)  or  increase  size  selectivity  (change  in  exploitation 
pattern).  It  could  mitigate  bycatch  and  also  improve  discard  survival.  Several  gear-based 
technical measures could potentially be considered depending on the area and/or the fishery.  

6.5.1  Information needed 

Selectivity  studies  per  species  and  size  are  needed  but  are  relatively  limited  (see  section  5). 
Some data are only available in certain areas and fisheries so further work is needed. 

6.5.2  Pros and cons 

Skates  and  rays  size  (large  and  flattened  body  shape)  make  improving  selectivity  difficult. 
However,  it  is  possible  to  use  more  selective  gears  to  reduce  the  catch  across  the  whole  size 
range  to  control  fishing  mortality  in  mixed  fisheries  where  skates  and  rays  are  a  bycatch.  The 
utility  of  such  measures  is  dependent  on  the  importance  of  the  skate  and  ray  bycatch  and  also 
the extent of any potential losses of other marketable species associated with the use of selective 
gears.  

Limitations on control and enforcement are similar to any other technical measures. As with other 
measures,  dialogue  with  stakeholders  and  step-by-step  implementation  may  help  compliance. 
Some  difficulties  for  control  may  arise  if,  to  account  for  fishery  and  area  specificities,  a  large 
variety of technical measures are implemented.  

This  type  of  measure  may  reduce  the  choke  risk  if  unwanted  catches  in  mixed  fisheries  can  be 
reduced.  This  may  need  finding  trade-offs  between  reducing  the  bycatch  of  skates  and  rays  to 
avoid  choking  mixed  fisheries  (with  some  potential  loss  in  revenues)  with  the  impact  of  a  total 
closure of the fishery. 

6.6 

Spatio-temporal measures 

These  measures  include  closure  of  specified  areas  to  some  or  all  fisheries  partially  or 
permanently.  Fisheries  management  cannot  in  general  be  achieved  through  closed  areas  alone 
and require permanent controls on fishing mortality. Closed areas are usually more efficient when 
they  actively  reduce  fishing  mortality  (Horwood  et  al.  1998).  Alternatively,  temporal  measures 
such as avoidance of catching skates and rays could be implemented by a ‘move-on’ principle in 
which the fishery relocates if a certain level of catch density is achieved. 

The  current  ICES  assessment  (only  based  on  trends  in  abundance  for  some  stocks)  may  be 
insufficient  to  act  as  performance  indicators  for  spatio-temporal  closures.  Stock  composition  in 
terms  of  sex,  maturity,  size,  age  etc.  could  act  as  secondary  indicators.  However,  these 
secondary  indicators  must  be  considered  carefully  when  defining  the  objectives  of  any  closure. 
Moreover, these objectives must guarantee positive outcomes in terms of the primary indicators 
of stock health, viz. fishing mortality and SSB or suitable proxies thereof. 

63 

 
 
6.6.1  Information needed 

Modelling  exercises  are  required  to  identify  the  extent  of  any  closure.  Modelling  requires  geo 
referenced  data  on  distribution  and  abundance,  by  life  history  stages  and  species,  including 
information on movement habitat quality and human activity. Information is required on the level 
of  F,  or  suitable  proxies,  to  feed  into  a  decision-making  process  to  determine  size,  location  and 
timing of closures. This would ideally take place in a participatory modelling process (Clarke et al. 
2007;  Hegland  et  al.  2009).  Modelling  should  take  into  account  existing  closures  such  as  MPAs, 
and  their  effects  in  reducing  F.  Much  of  the  data  requirements  are  met  by  VMS  data,  but  these 
may not be readily available for all countries, and perhaps automatic identification system (AIS) 
data could be an alternative.  

A  modelling  tool,  developed  by  Dedman  et  al.  (2017)  can  be  used  to  develop  closed  areas.    It 
generates  options  for  location  and  size  of  closed  areas  based  on  the  priorities  of  stakeholders, 
9notably the minimisation of fishing effort displacement. Results of hypothetical modelling in Irish 
Sea  rays  show  that  closing  high  CPUE  cells  results  in  a  smaller  closed  area  that  displaces  the 
most  fishing  effort,  whereas  closing  low  fishing  effort  areas  results  in  a  larger  closed  area  that 
displaces the least fishing effort (Dedman et al. 2017). Another approach was taken by Wiegand 
et al. (2011) using a four-season age-structured life-table matrix model to evaluate the relative 
effectiveness of seasonal closures versus size-based landing restrictions. This study showed that 
while long seasonal closures and full marine protected areas could be more effective at ensuring 
the  recovery  of  thornback  rays,  length  restrictions  may  be  simpler  to  implement  under  the 
current  institutional  framework  and  may  have  less  impact  on  the  multispecies  trawl  fisheries 
operating in the area (Wiegand et al, 2011). 

6.6.2  Pros and cons 

It is self-evident that closure to all fishing of 100% of a stock’s distribution will reduce F to zero. 
Such full closures are meaningful for endangered sedentary species in discrete areas (Hilborn et 
al.  2004).  But  in  general,  partial  closures  cannot  guarantee  a  particular  degree  of  fishing 
mortality  reduction.  A  key  concern  in  framing  such  closures  is  displacement  of  effort  to  other 
areas, which would reduce or eliminate the supposed benefits. For fisheries managed by quotas, 
a displacement of the fleet from one locality to another, where the same population is fished, will 
generally have little effect if the same quota is caught (Horwood et al. 1998).  

In  terms  of  control  and  enforcement,  closed  areas  appear  to  have  obvious  benefits  in  terms  of 
ease of enforcement using VMS, and inspections. However, given that ray and skate are targeted 
by multiple gears and fleets, not all active vessels may  be covered  by VMS. Furthermore, static 
gears  cannot  be  monitored  by  VMS  alone.  The  process  to  develop  such  measures  may  be  self-
defeating,  see  below.  Closures  leading  to  potentially  decreasing  fishing  opportunities  and 
increasing competition between users will be difficult to reach agreement on.  

6.6.3  Practical examples 

There is no example of an extant spatio-temporal closure as a fisheries management measure for 
rays,  but  a  marine  reserve  to  protect  Dipturus  intermedius  has  been  implemented  in  Scotland 
(Scottish Government, 2014). This closure does not, however, cover the entire stock distribution 
though some of the skates are fairly sedentary and do not move beyond its confines (Neat et al. 
2015). Therefore, the measure may be useful for the sedentary portion of the population. Further 
research may be required to investigate the extent of sedentary behaviour in this stock. 

Experience  of  two  previous  failed  attempts,  in  2013,  to  establish  such  closures  in  the  Irish  and 
Celtic Seas may be instructive. The Irish Sea box closure was proposed by industry. The first step 
was  a  small  closed  area,  to  be  progressively  increased  subject  to  advice  from  science  on  the 

64 

 
 
extent required. The proposal was not adopted because managers were concerned that the initial 
proposed  area  was  too  small  to  regulate  fishing  effort  to  any  great  extent.  Managers  also  were 
not convinced that an iterative process to increase the area could be operationalised.  

The  Celtic  Sea  box  closure  was  recommended  to  managers  and  stakeholders  by  a  group  of 
scientists  who  had  identified  an  area  in  the  Celtic  Sea  with  high  abundance  of  rays,  but 
apparently  no  fishing  effort.  The  proposal  failed  to  reach  wider  agreement  within  the  European 
industry when it became apparent that there was significant effort by Belgian vessels in the area. 

The  main  lessons  from  these  failed  exercises  is  that  there  needs  to  be  full  participation  of  all 
international  stakeholders  and  managers  throughout  the  process,  with  available  information 
readily  evaluated  in  a participatory  modelling  exercise.  Another  lesson  is  that  for  closures  to  be 
effective they need to be quite large in extent (Dedman et al. 2017; Stefansson and Rosenburg, 
2005;  Murawski  et  al.  2000;  Wiegand  et  al.  2011).  Very  importantly,  the  governance  and 
administrative  framework  does  not  exist  to  implement  them,  especially  for  multispecies  trawl 
fisheries (Wiegand et al 2011). Such mismatches between theory and current practice may also 
have prevented consideration by managers of the real time incentive concept defined by Kraak et 
al. (2012). This study allows fishers to dynamically choose how to spend fishing opportunities by 
limited fishing in sensitive areas. If closed areas are implemented without case by case evaluation 
and  appropriate  monitoring  programs,  there  is  a  risk  of  unfulfilled  expectations,  the  creation  of 
disincentives, and a loss of credibility (Hilborn et al. 2004). 

6.7 

Prohibited species list 

The  listing  of  a  species  on  the  prohibited  species  list  means  that  the  species  must  not  be 
targeted, retained or transhipped. Accidental catch shall not be harmed and individuals should be 
released as soon as possible.  

The ICES WGEF has looked at the usefulness of this measure (ICES, 2016) and writes:  The list of 
prohibited  species  on  the  TACs  and  quotas  regulations  (e.g.  CEC,  2016a)  is  an  appropriate 
measure  for  trying  to  protect  the  marine  fish  of  highest  conservation  importance,  particularly 
those  species  that  are  also  listed  on  CITES  and  various  other  conservation  conventions. 
Additionally,  there  should  be  sufficient  concern  over  the  population  status  and/or  impacts  of 
exploitation  that  warrants  such  a  long-term  conservation  strategy  over  the  whole  management 
area. See Appendix 1.  

6.7.1  Information needed 

In order to determine if a species has to be listed on the prohibited species list, evidence that this 
species  is  biologically  sensitive  to  any  exploitation  needs  to  be  provided.  It  is  also  necessary  to 
know if any (inter)national legislation is applicable for the species. Furthermore, the outcome of a 
productivity-susceptibility  analysis  per  fishery  should  be  available  together  with  estimates  of 
discard survival rate, studies on interaction of the species with the gear, avoidance and selectivity 
and information on handling to reduce mortality. Once the measure is in place, at sea monitoring 
can be used to determine compliance, although the probability of observing catches (and release) 
of  the  species  may  be  low  due  to  its  sporadic occurrence.  Information  for  monitoring  could also 
be  obtained  indirectly  from  abundance  indices  if  available.  Here  again,  due  the  sporadic 
occurrence of the species, such indices may be poorly estimated or unavailable. 

6.7.2  Pros and cons 

This measure has, potentially, the ability to control fishing mortality, but this is dependent on the 
rate  of  survival  of  the  individuals  after  discarding  and  encounter  rate  with  the  fishing  gear.  The 
measure could also be an incentive to avoid catching. It cannot however be considered as a stock 

65 

 
 
rebuilding  measure.  Once  the  species  is  on  the  prohibited  species  list,  no  data  can  be  collected 
other  than  the  fact  that  it  has  been  caught,  as  the  individuals  must  be  released  as  soon  as 
possible  which  may  lead  to  difficulty  to  assess  compliance.  Several  factors  may  lead  to  non-
compliance: possible high value of the products, species identification issues, non-transparency in 
the  criteria  used  to  include  the  species  in  the  list  leading  to  poor  acceptancy/buy-in  of  the 
measure, difficulty to predict the location of aggregations or individuals which makes difficult any 
avoidance.  

If implemented alone, the measure has no potential for choke. 

6.7.3  Practical application 

There  are  currently  no  transparent  criteria  to  include,  or  remove,  a  species  onto  or  off  the 
prohibited  species  list.  The  effectiveness  of  this  measure  can  be  measured  by  the  level  of 
compliance.  It  is  therefore  suggested  to  develop  a  procedure  for  listing  and  to  develop 
transparent  criteria  in  a  participatory  process.  Alternative  management  options  to  reduce 
mortality and maintain data provision should be part of this procedure. 

66 

 
 
 
 
Table 6.1. A summary of the main pros and cons of different potential management measures for skates and rays 

Management 
Measures 

Skates and rays 
generalised TAC 

Information needed 
as a basis for 
implementation 

ICES catch advice 

Generalised TAC 
with sub-TAC for 
particular stocks 

ICES catch advice 

TACs by Genus 

ICES catch advice 

TAC by stock 
(ICES advice) 

ICES catch advice 

Landing trip limit 
(outside the quota 
system, and 
applied to selected 
species) 

Catch (landings) 
weights by trip for 
each métier by 
season/area. Discard 
survival. Market value 

Data availability and 
limits 

ICES is currently landings 
advice so estimates of 
dead discard needed. 
Improvement in species-
specific catch estimates 
Better stock identification 

ICES is currently landings 
advice so estimates of 
dead discard needed. 
Improvement in species-
specific catch estimates 
Better stock identification 

ICES is currently landings 
advice so estimates of 
dead discard needed. 
Improvement in species-
specific catch estimates 
Better stock identification 

ICES is currently landings 
advice so estimates of 
dead discard needed. 
Improvement in species-
specific catch estimates 
Better stock identification 

Numbers at length 
retained/discarded 
available for some 
fisheries from at-sea 
observer programmes. 
Landings (catch) data by 
trip available. Discard 
survival rates estimates 
needed  

Control Fishing 
Mortality 

Pro 

Limited 

Control and 
Enforcement 

Con 

Pro 

Con 

Potential issues 
related to compliance 

Choke 

Sources of 
uncertainty 

Limited control at 
stock level 

Easy as species is 
not required for 
monitoring quota 
uptake 

Low incentive for 
misreporting except for 
prohibited species 

Potential for 
choke effects, 
depending on 
potential 
exemptions 

Quantification of 
survival per species 
and métier 
Species identification 

For the sub-TAC 
stocks and 
partially for the 
others 

Restrictive sub-TAC 
may result in an 
increase in F on the 
other generalised 
stocks 
Limited control of F 
for the species not in 
the sub-TAC 

Potentially easy to 
control subject to 
species 
identification 

Increase in 
resources for 
monitoring species 
specific data for 
Sub-TAC 

Species identification 
and misreporting 
Non-transparent criteria 
for selecting Sub-TAC 
stocks 

High potential for 
choke effects, 
depending on 
potential 
exemptions 

Quantification of 
survival per species 
and métier. 
Transparent 
selection of stocks 
under sub-TAC. 
Species identification 

Potential 
performance 
indicator 

Ideally F and SSB 
or proxies for all 
species 
Reference points 
defined 

Ideally F and SSB 
or proxies for all 
species 
Reference points 
defined 

Partly  

Control F at genus 
level, not at stock 
level 

Potentially easy to 
control subject to 
genus identification 

Increase in 
resources for 
monitoring species 
specific data for the 
genera 

Species identification 
and (low potential) for 
misreporting 

Potential for 
choke effects, 
depending on 
potential 
exemptions 

Quantification of 
survival per species 
and métier 
Species 
identifications 

Ideally F and SSB 
or proxies for all 
species. 
Reference points 
defined 

Potential to 
control F at the 
stock level 

Potentially easy to 
control subject to 
species 
identification 

Increase in 
resources for 
monitoring species 
specific data 

Species identification 
and misreporting 

High potential for 
choke effects, 
depending on 
potential 
exemptions 

Quantification of 
survival per species 
and métier 
Species 
identifications 

Ideally F and SSB 
or proxies for all 
species. 
Reference points 
defined 

For species that 
survive 
discarding. 
Deters the 
development of 
target fisheries.  

No control for 
species that do not 
survive discarding.  
May encourage high 
grading (e.g. 
retaining of larger 
(mature) females) 

Easy at point of 
landing (more 
problematic if large 
number of port). 
absolute limits (kg 
per trip) is easier to 
enforce than 
percentages of 
catch 

Species 
identification; better 
definition of 
conversion factors 
for processed to live 
weight  (including 
the option to land 
individual 
whole/gutted) 

No 

Appropriate conversion 
factors availability. 
Degree of 
variance/tolerance 
established. 
Stakeholder 
consultation to agree on 
the landing limit 

Landings/catch data 
by trip (to verify 
compliance). F and 
SSB (to assess 
stock status).  

Spatial-temporal 
distribution and 
abundance of some 
lesser-known 
species in relation to 
fleet dynamics (e.g. 
is there an area of 
high local abundance 
in relation to some 
specific fleets); 
discard survival. The 
selected level of the 
limit and market 
value would affect 
effectiveness. 

67 

 
 
 
 
 
 
Control Fishing 
Mortality 

Control and 
Enforcement 

Pro 

Con 

Pro 

Con 

Potential issues 
related to compliance 

Choke 

Sources of 
uncertainty 

Yes if correlation 
between fishing 
mortality (F) and 
effort. Applicable 
to mixed fisheries 

Potentially easy; no 
incentive for 
misreporting 
catches 

Technological creep 
is difficult to control 

Displacement of effort 
and transfer to other 
fisheries.   

No potential for 
choke effects 
without a TAC 

Technological creep, 
increase in capacity 
and fishers know 
how increase 
efficiency. Shift to 
other métier may 
increase F. Increase 
in bycatch of skates 
and rays in mixed 
fisheries. Fleet 
dynamics not taken 
into account 

Ineffective if discard 
survival rate is low or 
it increases 
exploitation of 
mature females. If 
"one size for all'' then 
may not control F 
adequately per 
species. 
Improvement in gear 
selectivity may be 
difficult.  

Ineffective if survival 
low or low grading 

Management 
Measures 

Effort 

Information needed 
as a basis for 
implementation 

Standardised measure 
of effort per métier and 
spatial distribution. 
Catches composition. 
Stock status 

Data availability and 
limits 

Fisheries Dependent 
Information (FDI) 
available but discard 
information incomplete. 
Species composition 
available (observer 
programmes and log 
books). Data on effort 
available from fleet 
register 

Minimum size 

Species-specific size 
at maturity/first 
maternity; size 
composition by métier 
(level 6); discard 
survival by size/métier; 
retention ogive; 
price/size; growth 

Data mostly available. 
Missing life history for 
some species. 
Species identification  
and estimation of dead 
discards needs 
improvement 

If discard survival 
rate is high and 
good discard 
practice; potential 
incentive for size 
selection or 
changes in fishing 
ground 

Maximum size 

Minimum and 
maximum size 
combined  

Species-specific 
female size at first or 
full maternity, fecundity 
at length, spawning 
periodicity; size 
composition by métier 
(level 6); retention 
ogive; price/size 
grade; growth and 
longevity 

See both of above 

Data available in some 
cases. Missing life history 
in most species. 
Species identification  
and estimation of dead 
discards needs 
improvement  

If discard survival 
rate is high and 
good discard 
practice; potential 
incentive for size 
selection or 
changing fishing 
ground 

Data available in some 
cases. Missing life history 
in most species. 
Species identification  
and estimation of dead 
discards needs 
improvement  

If discard survival 
rate is high and 
good discard 
practice; potential 
incentive for size 
selection or 
changing fishing 
ground 

Easy to implement 
by measurement on 
inspection 

Potential increase of 
dead discarding 

Species identification. 
Standardisation of size 
measurement needed 

Easy to implement 
by measurement on 
inspection 

Possible increased 
dead discarding, 
difficult to implement 
if fish are winged at 
sea 

Species identification. 
Standardisation of size 
measurement needed 

Ineffective if survival 
low 

Easy to implement 
by measurement on 
inspection 

Possible increased 
dead discarding 

Species identification; 
Standardisation of size 
measurement needed 

68 

Changes to other 
métiers need to be 
quantified or 
regulated; 
technological creep; 
applicability in mixed 
fisheries 

If defined for a group 
of species, can lead 
to changes in 
species targeting, 
possibly not 
benefiting the larger 
bodied species.  
Species identification 
if implemented at 
species level 

Species identification 
if implemented at 
species level 

Potential 
performance 
indicator 

Ideally F and SSB 
or proxies. 

Primary indicator is 
F and SSB or their 
proxies ; secondary 
indicator is size (% 
undersized) 
composition in 
catch 

Primary indicator is 
F and SSB or their 
proxies ; secondary 
indicator is size  
(%mature) 
composition in 
catch 

Species identification 
if implemented at 
species level 

Primary indicator is 
F and SSB or their 
proxies ; secondary 
indicator is size  
composition in 
catch 

No potential for 
choke if without a 
TAC. If associated 
with catch limits, 
work if high 
survival and 
exemption 
granted otherwise 
in contradiction 
with the landing 
obligation.  

No potential for 
choke if without a 
TAC. If associated 
with catch limits, 
work if high 
survival and 
exemption 
granted otherwise 
in contradiction 
with the landing 
obligation.  

No potential for 
choke if without a 
TAC. If associated 
with catch limits, 
work if high 
survival and 
exemption 
granted otherwise 
in contradiction 
with the landing 
obligation.  

 
 
 
 
 
 
Management 
Measures 

Gear selectivity 

Spatio-temporal 
management 

Information needed 
as a basis for 
implementation 

Selectivity studies, 
species and size 
composition of catch, 
list of prohibited 
species 

Data availability and 
limits 

Limited. Only available in 
some areas and some 
gears. Further work 
needed but difficult to 
increase size selectivity 
due to the skates and 
rays morphology. 

Control Fishing 
Mortality 

Control and 
Enforcement 

Pro 

Con 

Pro 

Con 

Potential issues 
related to compliance 

Choke 

Sources of 
uncertainty 

Possible for some 
fisheries. May 
work better for 
limiting bycatch 

Maybe more difficult 
in mixed fisheries. 
Difficult to increase 
size selectivity. 

Potentially easy to 
control 

Difficult if large 
number of technical 
measures 
implemented 

If too many measures 
implemented 

May reduce the 
choke risk if 
unwanted catches 
in mixed fisheries 
can be reduced. 

Difficult to measure if 
a large variety of 
measures are 
implemented . 
A results based 
approach could be 
preferable. 

Geo referenced data 
on distribution and 
abundance; 
Distribution and level 
of current fishing 
pressure (F or F 
proxies) and spatio-
temporal management 
measures already 
implemented (MPA); 
Catch composition in 
relevant fisheries. Data 
from at-sea monitoring 
programmes; 

Most data already 
available (Surveys, VMS); 
Surveys not covering all 
species and areas. VMS 
data not always available 
to scientists. 
Limited data availability 
for vessels without VMS;  
Use of automatic 
identification system (AIS) 
data as an alternative; 
Limited availability of fish 
movement data (tagging) 

Can reduce 
fishing mortality 
subject to 
conditions on a 
case by case 
basis : e.g. 
sufficient extent 
of the closure; 
Potential to 
control other 
sources of 
mortality besides 
fishing; 

Displacement of 
effort and transfer to 
other fisheries inside 
the area; 
Potential for 
increased effort on 
border;  
In areas with multiple 
users (e.g. harbours, 
dredging) other 
sources of mortality 
may be difficult to 
control; 

Potentially easy to 
control (VMS);  

Difficulties for 
fisheries not 
covered by VMS;  
Difficult to assess 
fishing activities and 
effort for static 
gears;  

Permitted fisheries may 
still be catching skates 
and rays. 

This type of 
management 
without TAC has 
no potential for 
choke 

Prohibited species 
list 

Evidence of very rare 
occurrence. 
(Inter)national 
legislation. 
Productivity-
Susceptibility Analysis 
(PSA) per fishery. 
Discard survival rate. 
Interaction of the 
species with the gear, 
selectivity and 
handling to reduce 
mortality. 

ICES advice and 
consideration of species 
listed on CITES and CMS 
partially available. PSA 
available for some 
fisheries in North and 
Celtic Seas. (Limited) 
avoidance and discard 
survival studies and gear 
selectivity. Handling 
protocols available 
(potentially difficult to 
implement at sea). 
Abundance indices 
available for some 
species. 

Possible but 
dependent on the 
rate of discards 
survival; 
May be an 
incentive not to 
fish the stock;   

Dependent on 
encounter rate and 
discard survival rate. 
Not a rebuilding 
measure.  

No fishing for, or 
landings allowed, 
so at sea and 
market inspections 
possibly 
straightforward 

Possibly, not to be 
detected during 
inspections at sea 
and in the market 
place as potentially 
a sporadic 
occurrence. Species 
identification both at 
sea and in the 
market place 
problematic. Catch 
might not be 
reported 

No 

Possible high value of 
products. Species 
identification issues. 
Non-transparency in 
listing criteria leading to 
poor acceptance of the 
measure. Difficulty to 
predict location of 
aggregations or 
individuals makes 
difficult any avoidance. 

69 

Potential 
performance 
indicator 

Primary indicator is 
F and SSB or their 
proxies ; secondary 
indicator is size  
composition in 
catch. 

Depends on the 
type spatio-
temporal 
management 
measure. Could 
include 
demographic 
composition of 
stock (e.g. size and 
gender) or local 
increase in 
abundance; 
Ideally F and SSB 
or proxies for 
relevant stocks 

Levels of 
compliance (no 
targeting, landing or 
transhipment) 

Displacement of 
effort and transfer to 
other fisheries inside 
or outside the area; 
Difficulty to assess 
impacts (e.g. 
increase in stock, 
decrease in F); 
Difficulty to select the 
type of spatio-
temporal 
management (from 
seasonal gear 
restrictions to full no-
take zone); 
Variable availability 
and resolution of 
vessel data for 
scientific 
investigations 

Catch level, 
occurrence and 
fishery interaction. 
Species 
identification. Rates 
of discard survival 
and handling 
methodologies. 
Information on 
population 
productivity. Loss of 
data from 
commercial and 
scientific sources. 

 
 
 
 
 
 
70 

 
 
 
7 

CONCLUSION WITH SOME GUIDANCE FOR NEXT STEPS  

The conclusions from EWG-17-10 are split into general conclusions related to the review of the 
potential management measures, elements associated with main data and knowledge gaps and 
needs and some guidance for the next steps. 

7.1 

Management measure review 

  Among the TAC based approaches reviewed by the group, the TAC by stock is the only one 
that  permits  the  setting  of  limits  on  catches  by  stock  in  line  with  individual  stock 
development  and  the  catch  levels  recommended  by  ICES.  All  other  options  would  retain, 
to  varying  degrees,  the  problem  of  the  current  global  TACs  (e.g.  limiting  fishing 
opportunity for stocks for which the abundance is increasing, and insufficient protection for 
decreasing stocks or stocks of unknown status) 

  TACs  set  by  stock  may  be  compromised  by  species  identification  issues.  This  might  be 
offset in certain cases by incentives to provide better data at stock level by fishers. TACs 
by stock could also create additional choke issues over and above the other TAC options. 
In  any  case,  it  must  be  noted  that  adding  more  TACs  (going  from  a  generalized  TAC 
system to a stock based TAC) may add extra monitoring requirements. 

  The main impediment to any TAC based measure is lack of advice on outtake in terms of 
total  catch  (landings  +  dead  discards).  Currently,  ICES  only  provide  landings  advice  for 
skates  and  rays.  Including  discard  information  requires  quantification  of  discards  and 
survival of these discards. More work is required in these areas.  

  Spatio-temporal measures can only be successful if they can demonstrably control fishing 
mortality.  These  can  be  used  to  reduce  mortality  on  stocks  on  a  case-by-case  basis  and 
may be complemented by other generalised management measures. Theoretical modelling 
work  has  been  done  and  provides  a  firm  analytical  basis.    In  this  context,  size,  location 
and timing of management measures can be developed in a participatory decision-making 
process. The areas to be closed are likely to be quite large which could potentially impact 
the  general  fishery.  The  difficulties  in  reaching  agreement  of  managers  and  stakeholders 
for such large closures should not be underestimated. 

  Effort management may have fewer control and enforcement issues as compared to other 
options.  However,  measuring  (and  limiting)  increase  in  fishing  efficiency  is  extremely 
difficult, which possibly renders this measure ineffective in many fisheries. There may also 
be potential management conflicts in mixed fisheries where skates and rays are managed 
by effort while the other species are managed by TACs. 

  The  underlying  data  for  developing  management  options  based  on  gear  selectivity  is 
currently limited. Current studies indicate that it  is difficult to increase size selectivity for 
skates and rays but there are a number of gear modifications that have been shown to be 
effective  at  reducing  their  bycatch.  The  adoption  of  such  gears  is  dependent  on  whether 
the skates and ray species involved have a commercial value and the availability of fishing 
opportunities that allows them to be landed. Where such species are considered as part of 
the  marketable  catch  then  there  is  little  incentive  to  reduce  bycatch  as  to  do  so  would 
represent  a  loss  of  income.  However,  in  a  choke  species  scenario,  where  the  quota  for 
skates  and  rays  is  exhausted  and  the  only  option  for  a  vessel  to  continue  fishing  in  a 
specific  fishery  is  to  fish  without  catching  skates  and  rays  then  such  gears  may  be 
considered an option.  

  Size  restrictions,  either  minimum,  maximum  or  a  combination  should  be  tailored  to 
species  to  be  most  effective.  This  management  measure  would  however  be  in 
contradiction  with  the  landing  obligation  if  implemented  in  association  with  catch  limits, 
except  for  species  for  which  an  exemption  for  high  survival  is  granted.  It  may  also  be 
difficult  to  receive  buy-in  from  fishermen  of  limits  set  on  maximum  sizes  as  generally, 
larger rays have the highest commercial value.  

71 

71 

 
 
 
  The  prohibited  species  list  should  ideally  only  be  used  for  species  which  are  biologically 
sensitive  to  any  exploitation.  Without  additional  management  measures  to  improve 
survival, listing will not necessarily lead to a decrease in mortality. The decision to include, 
or  remove,  any  species  onto  or  off  the  prohibited  species  list  is  currently  not  carried  out 
according to transparent criteria. It is suggested to develop a procedure for listing and to 
develop transparent criteria in a participatory process. 

7.2 

Data limitation and needs 

  EWG-17-10 notes that the current data requirement and sampling effort of the DCMap on 
skates  and  rays  is  insufficient  to  provide  robust  estimates  of  various  parameters  (e.g. 
maturity,  commercial  catch  composition,  sex-ratio)  needed  for  stock  assessment  and 
management. Consequently, increasing needs on information on catches and fisheries may 
imply adjustments of the DCMap for the data collection for skates and rays.  

  The most crucial data gaps at the current time are discard survival (vitality and at-vessel 
mortality, and short- and longer-term discard survival) and estimates of (dead) discards. 
These topics should have the highest priority.  

  Regarding  survival  of  discarded  fish,  the  EWG  notes  that  the  estimates  available  only 
cover  a  limited  number  of  métiers,  areas  and  species.  Several  of  the  available  estimates 
are  limited  to  short  term  survival  rate  and  are  still  uncertain.  To  both  increase  the 
coverage  of  gear,  area  and  species  and  improve  current  estimates,  a  data  review  and 
analysis,  on  the  model  developed  by  Catchpole  et  al.  (2017)  on  UK  waters  should  be 
extended  to  other  areas.  Such  a  review  should  also  highlight  the  main  data  gaps  where 
particular efforts are needed.  

  Further  data  issues  which  require  attention  are  improved  delineation  of  biological  stock 
units, more robust estimates of stock status and development of MSY reference points or 
proxies.  Those  are  key  elements  needed  to  be  able  to  quantitatively  evaluate  the 
performances  and 
impacts  (biological,  socio-economical)  of  various  management 
measures. EWG-17-10 notes that some ICES working groups (WKMSYcat34, WKlife) or EU 
and/or  national  research  projects  (Damara,  Drumfish),  although  not  necessarily 
specifically on skates and rays, may contribute to progress on those topics.  

7.3 

Next steps 

  EWG-17-10 was asked to “recommend a new approach for the sustainable management of 
skates  and  rays  fisheries.”  Due  to  the  diversity  of  species  in  terms  of  biological 
characteristics,  complexity  of  fisheries  catching  them  and  data  limitations,  it  is  not 
currently  possible  to  fully  and  quantitatively  evaluate  any  particular  management 
measures  or  group  of  measures.  A  way  forward  would  be  for  managers  and  relevant 
stakeholders to first decide on the objectives of potential management measures (and the 
scope  in  terms  of  species  and  areas,  and  governance  framework).  It  is  only  once  these 
have been identified that a subsequent scientific evaluation may be possible. 

  Any  change  to  the  current  management  practice  should  be  based  on  an  evaluation  of 
current and potential measures, may include a combination of the measures presented in 
this  report  and  may  vary  regionally.  The  participation  of  stakeholders  to  discuss  the 
viability  of  potential  measures  and  improve  subsequent  uptake  and  compliance  is 
important. This could be carried  out in the context of participating modelling and/or with 
the  development  of  management  strategy  evaluation  framework.  Any  development  of 
participatory  modelling  for  regional  areas  should  be  at  a  regional  level  that  is  consistent 
with biological stock units.  
It  is  worth  noting  that  although  a  combination  of  management  measures  might  be  the 
best  option  in  some  cases,  it  is  very  important  to  avoid  developing  complex  frameworks 
which may be difficult to implement, control and monitor and may generate low levels of 
compliance and buy-in by fishermen. 

 

  Specificities in the biology of skates and rays should be considered when developing both 
alternative  stock  assessment  methods  and  management  frameworks.  This  should  be 
considered  together  with  regional  differences  in  skate  assemblages,  metrics  for 
abundance, demography, geographic range and fishing pressure.  

72 

72 

 
8 

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CEFAS. 

Final 

Benoit,  H.  P.,  Swain,  D.  P.,  Niles,  M.,  LeBlanc,  S.  &  Davidson,  L.  A.  (2010a).  Incidental  catch 
amounts  and  potential  post-release  survival  of  winter  skate  (Leucoraja  ocellata)  captured  in  the 
scallop  dredge  fishery  in  the  southern  Gulf  of  St.  Lawrence  (2006–2008).  Canadian  Science 
Advisory Secretariat Research Document 2010/043. Available at http://www.dfo-mpo.gc.ca/csas-
sccs/publications/resdocs-docrech/2010/2010_043_e.pdf/ 

Benoit, H. P., Hurlbut, T.&Chassé, J. (2010b). Assessing the factors influencing discard mortality 
of  demersal  fishes  using  a  semi-quantitative  indicator  of  survival  potential.  Fisheries  Research 
106, 436–447. 

Benoit,  H.  P.,  Hurlbut,  T.,  Chassé,  J.  &  Jonsen,  I.  D.  (2012).  Estimating  fishery-scale  rates  of 
discard mortality using conditional reasoning. Fisheries Research 125, 318–330. 

Depestele, J., Desender, M., Benoˆıt, H. P., Polet, H. & Vincx, M. (2014). Short-term survival of 
discarded target fish and non-target invertebrate species in the “eurocutter” beam trawl fishery of 
the southern North Sea. Fisheries Research 154, 82–92. 

Enever,  R.,  Catchpole,  T.  L.,  Ellis,  J.  R.  &  Grant,  A.  (2009).  The  survival  of  skates  (Rajidae) 
caught by demersal trawlers fishing in UK waters. Fisheries Research 97, 72–76. 

Enever,  R.,  Revill,  A.  S.,  Caslake,  R.  &  Grant,  A.  (2010).  Discard  mitigation  increases  skate 
survival in the Bristol Channel. Fisheries Research 102, 9–15. 

Endicott,  M.  &  Agnew,  D.  J.  (2004).  The  survivorship  of  rays  discarded  from  the  South  Georgia 
longline fishery. CCAMLR Science 11, 155–164. 

Kaiser,  M.  J.  &  Spencer,  B.  E.  (1995).  Survival  of  by-catch  from  a  beam  trawl.  Marine  Ecology 
Progress Series 126, 31–38. 

Laptikhovsky, V. V. (2004). Survival rates for rays discarded by the bottom trawl squid fishery off 
the Falkland Islands. Fishery Bulletin 102, 757–759. 

Lyle,  J.  M.,  Bell,  J.  D.,  Chuwen,  B.  M.,  Barrett,  N.,  Tracey,  S.  R.  &  Buxton,  C.  D.  (2014). 
Assessing  the  impacts  of  gillnetting  in  Tasmania:  implications  for  by-catch  and  biodiversity. 
Institute  for  Marine  and  Antarctic  Studies,  University  of  Tasmania.  Fisheries  Research  and 
Development 
at 
http://dpipwe.tas.gov.au/Documents/Gillnetting_Impacts_Tas_Bycatch_Biodiversity_FRDC2010.p
df/ 

Corporation 

2010/016. 

Available 

(FRDC) 

Project 

No. 

76 

76 

 
 
 
 
 
 
 
 
 
 
 
 
 
Mandelman, J. W., Cicia, A. M., Ingram, G. W. Jr., Driggers, W. B. III, Coutre, K. M. & Sulikowski, 
J. A. (2012). Short-term post-release mortality of skates (family Rajidae) discarded in a western 
North Atlantic commercial otter trawl fishery. Fisheries Research 139, 76–84. 

Rudders,  D.  B.,  Knotek,  R.  J.,  Sulikowski,  J.  A.,  Mandleman,  J.  A.  &  Benoˆıt,  H.  P.  (2015). 
Evaluating the condition and discard mortality of skates following capture and handling in the sea 
scallop dredge fishery. VIMS Marine Resource Report No. 2015–6. Gloucester Point, VA: Virginia 
Institute  of  Marine  Science.  Available  at  http://s3.amazonaws.com/nefmc.org/2.2-FR12-
0030_VIMS-.pdf/ 

Saygu,  I.&  Deval,M.  C.  (2014).  The  post-release  survival  of  two  skate  species  discarded  by 
bottom  trawl  fisheries  in  Antalya  Bay,  eastern  Mediterranean.  Turkish  Journal  of  Fisheries  and 
Aquatic Sciences 14, 1–7. 

Scott-Denton, E., Cryer, P. F., Gocke, J. P., Harrelson, M. R., Kinsella, D. L., Pulver, J. R., Smith, 
R. C. &Williams, J. A. (2011). Descriptions of the U.S. Gulf of Mexico reef fish bottom longline and 
vertical line fisheries based on observer data. Marine Fisheries Review 73, 1–26. 

References on selectivity (section 5) 

Anon. 1997.  Separator trawl trials off the North-west coast - mfv “Slieve Bloom” April 1997. BIM 
internal report. 12pp. 

Anon. 2011. Reducing winter flounder retention through the use of avoidance gear adaptations – 
Squid  trawl  network  –  AGA  Trip  reports.    Cornell  Cooperative  Extension’s  Fisheries  Program  in 
partnership  with  University  of  Massachusetts  School  and  Marine  Science  and  Technology  and 
University of Rhode Island Fisheries Center.  

Baeta,  F.,  Batista,  M.,  Maia,  A.,  Costa,  M.  J.  &  Cabral,  H.  (2010).  Elasmobranch  by-catch  in  a 
trammel net fishery in the Portuguese west coast. Fisheries Research 102, 123–129. 

Bayse, S. M., Pol, M. V., and He, P. Fish and squid behaviour at the mouth of a drop-chain trawl: 
factors  contributing  to  capture  or  escape.  ICES  Journal  of  Marine  Science  (2016),  73(6),  1545–
1556. doi:10.1093/icesjms/fsw007 Original Article 73: 1545–1556. 

Beutel,  D.,  L.  Skrobe,  K.  Castro,  P.  Ruhle  Sr.,  P.  Ruhle  Jr.,  J.  O'Grady,  and  J.  Knight.  2008. 
Bycatch 
reduction in the Northeast USA directed haddock bottom trawl fishery. Fisheries 
Research 94(2): 190 – 198. 

Brewer, D., Heales, D., Milton, D., Dell, Q., Fry, G., Venables, B.& Jones, P. 2006. The impact of 
turtle excluder devices and by-catch reduction devices on diverse tropical marine communities in 
Australia’s northern prawn trawl fishery. Fisheries Research 81, 176–188. 

Brothers, G. 1991. Shrimping with sorting panels and modified trawls. DFO. 26pp. 

Christensen, C.P. 2014. Opportunities for the reduction of skate bycatch in Atlantic Canada trawl 
fisheries:  A  case  study  of  two  innovative  trawl  gear  designs  [graduate  project].  Halifax,  NS: 
Dalhousie University. 

Cosgrove,  R.,  Browne,  D.,  and  McDonald,  D.  2016.  Assessment  of  rigid  sorting  grids  in  an  Irish 
quad-rig trawl fishery for Nephrops. BIM Report. February 2016. 

Enever, R., Revill, A. S., Caslake, R. & Grant, A. 2010. Discard mitigation increases skate survival 
in the Bristol Channel. Fisheries Research 102, 9–15. 

77 

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Favaro,  B.  &  Côté,  I.  M.  (2015).  Do  by-catch  reduction  devices  in  longline  fisheries  reduce 
capture of sharks and rays? A global meta-analysis. Fish and Fisheries 16, 300–309. 

Fiche, M, Morandeau, F, and Robert, M. , 2017. Using 100mm T90 netting in the extension and 
codend and a 120mm square mesh panel to reduce discards in whitefish fisheries. In O’Neill, F.G. 
and Mutch, K. (Eds): Selectivity in Trawl Fishing Gears. Scottish Marine and Freshwater Science 
Vol 8 No 1.Fiche et al., 2017) 

Hartell, B.W., Cryer, M., MacDiarmid, A.B. 2006. Reducing bycatch in New Zealand’s scampi trawl 
fisheries. New Zealand Aquatic Environment and Biodiversity Report No. 4. 53pp. 

Isaksen, B., Valdemarsen, J., Larsen, R. & Karlsen, L. 1992. Reduction of fish by-catch in shrimp 
trawl using a rigid separator grid in the aft belly. Fisheries Research 13, 335–352. 

Kynoch, R.J., Ferro, R.S.T. and Fryer, R.J. 2009. Trials to reduce cod by-catches in whitefish trawl 
fisheries  by  modifying  the  belly  sheets  of  commercial  trawl  nets  to  incorporate  large  diamond 
mesh panels. Scottish Industry/Science Partnership (SISP) Report No 05/09. 

Kynoch,  R.J.,  O’Neill,  F.G.  and  Fryer,  R.J.,  2010.  Test  for  300mm  and  600mm  netting  in  the 
forward section of a Scottish whitefish trawl. Fisheries Research, 108, 277-282. 

Kynoch,  R. J.,  Fryer,  R.  J.  & Neat, F.  C.  (2015).  A  simple  technical  measure  to  reduce by-catch 
and discard of skates and sharks in mixed-species bottom-trawl fisheries. ICES Journal of Marine 
Science 72, 1861–1868. doi: 10.1093/icesjms/fsv037 

Lomeli,  M.  J.  &  Wakefield,W.W.  (2013).  A  flexible  sorting  grid  to  reduce  Pacific  halibut 
(Hippoglossus 
stenolepis) by-catch in the US west coast groundfish bottom trawl fishery. 
Fisheries Research 143, 102–108. 

Main,  J.  and  Sangster,  G.I.  1982.  A  study  of  separating  fish  from  Nephrops  norvegicus  in  a 
bottom trawl. Scottish Fisheries Research Report Number 24. 8pp. 

Meillat,  M.,  Morandeau,  F.,  Mehault  S.,  Larnaud,  P.  2011.  Nephrops  grid  and  Nephrops  grid 
combined to square mesh cylinder and window. Presentation at information session on technical 
conservation measures, discards and escapement of juvenile fish. North western Waters Regional 
Advisory Group (NWWAC). Dublin 5 July 2011. 

McHugh, M., Browne, D., Oliver, M., Tyndall, P., Minto, C., Cosgrove, R. 2017. Raising the fishing 
line to reduce cod catches in demersal trawls targeting fish species.  BIM Fisheries Conservation 
Report. May 2017. 9pp. 

Reeves, S. and Armstrong, F. 2009. Trials with an Eliminator-type trawl in the North Sea Saithe 
Fishery. Cefas Fisheries Science Partnership: 2009/10. December 2009. 14pp. 

Revill,  A.  and  Doran,  S.  2008.  Further  North  Sae  fishing  triasl  with  the  “EliminatorTM  ”  trawl 
(2008). CEFAS Project Reference: MF 1002 & C3307. December 2008. 6pp. 

Willems,  T.,  Depestele,  J.,De  Backer,A.&Hostens,  K.  2016.  Ray  by-catch  in  a  tropical  shrimp 
fishery:  do  bycatch  reduction  devices  and  turtle  excluder  devices  effectively  exclude  rays? 
Fisheries Research 175, 35–42. 

Thorpe,  T.  &  Frierson,  D.  (2009).  Bycatch  mitigation  assessment  for  sharks  caught  in  coastal 
anchored gillnets. Fisheries Research 98, 102–112. 

78 

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9 

APPENDIX 

Information from ICES WGEF 2016 on the utility of the Prohibited species list on TAC and quotas 
regulations (ICES, 2016) 

The list of prohibited species on the TACs and quotas regulations (e.g. CEC, 2016a) is an 
appropriate measure for trying to protect the marine fish of highest conservation importance, 
particularly those species that are also listed on CITES and various other conservation 
conventions. Additionally, there should be sufficient concern over the population status and/or 
impacts of exploitation that warrants such a long-term conservation strategy over the whole 
management area. 

There are some species that would fall into this category. For example, white shark and basking 
shark are both listed on CITES and some European nations have given legal protection to these 
species. Angel shark has also been given legal protection in UK.  

It should also be recognized that some species that are considered depleted in parts of their 
range may remain locally abundant in some areas, and such species might be able to support low 
levels of exploitation. From a fisheries management viewpoint, advice for a zero or near-zero 
TAC, or for no target fisheries, is very different from a requirement for ‘prohibited species’ status, 
especially as a period of conservative management may benefit the species and facilitate a return 
to commercial exploitation in the short term. Additionally, there is a rationale that a list of 
prohibited species should not be changing regularly, as this could lead to confusion for both the 
fishing and enforcement communities. 

In 2009 and 2010 undulate ray (Raja undulata) was moved on to the prohibited species list. This 
had not been advised by ICES. Following a request from commercial fishers, the European 
Commission asked ICES to give advice on this listing. ICES reiterated that undulate ray would be 
better managed under local management measures and that there was no justification for placing 
undulate ray on the prohibited species list. There have been subsequent changes in the listing of 
this species. It was removed from the Prohibited Species List for Subarea 7 in 2014 (albeit as a 
species that cannot be retained or landed). In 2015, undulate ray was only maintained in the 
prohibited species list in Subareas 6 and 10. Small TACs were established for stocks in the 
English Channel and Bay of Biscay in 2015 and for the stock in the Iberian ecoregion in 2016. 

Reference 

ICES.  2016.  Report  of  the  Working  Group  on  Elasmobranch  Fishes  (WGEF),  15–24  June  2016, 

Lisbon, Portugal. ICES CM/ACOM:20. 26 pp. 

79 

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10 CONTACT DETAILS OF EWG-17-10 PARTICIPANTS 

1  -  Information  on  EWG  participant’s  affiliations  is  displayed  for  information  only.  In  any  case, 
Members of the STECF, invited experts, and JRC experts shall act independently. In the context of 
the  STECF  work,  the  committee  members  and  other  experts  do  not  represent  the 
institutions/bodies  they  are  affiliated  to  in  their  daily  jobs.  STECF  members  and  experts  also 
declare  at  each  meeting  of  the  STECF  and  of  its  Expert  Working  Groups  any  specific  interest 
which  might  be  considered  prejudicial  to  their  independence  in  relation  to  specific  items  on  the 
agenda.  These  declarations  are  displayed  on  the  public  meeting’s  website  if  experts  explicitly 
authorized the JRC to do so in accordance with EU legislation on the protection of personnel data. 
For more information: http://stecf.jrc.ec.europa.eu/adm-declarations 

STECF members 

Name 

Address1 

Telephone no. 

Email 

Bertignac, 
Michel (chair) 

Borges, Lisa 

Laboratoire de 
Biologie Halieutique 
IFREMER Centre de 
Brest BP 70 - 29280 
Plouzane, France 
FishFix, Brussels, 
Belgium 

Tel: +33 (0)2 98 
22 45 25 

michel.bertignac@ifremer.fr 

info@fishfix.eu 

Invited experts 

Name 

Address 

Telephone no.  Email 

Clarke, Maurice  Marine Institute, 

Maurice.Clarke@Marine.ie 

Rinville, 
Oranmore, Co, 
Galway, Ireland 

Ellis, Jim 

Cefas 

Pakefield Road 

Lowestoft 

Suffolk  NR33 
0HT 

United Kingdom 

IPMA 

Avenida de 
Brasilia 1449-
006 

jim.ellis@cefas.co.uk 

ifigueiredo@ipma.pt 

Phone +44 
1502 524300 

Fax +44 1502 
513865 

Phone + 351 
21 3027131 

Fax + 351 21 
3015948 

 Lisbon Portugal 

MNHN – CRESCO 

Phone +33 
789068877 

gadenne.helene@gmail.com 

38 rue de Port-
Blanc 

35800 Dinard 

France 

Des Requins et 
des Hommes 

Phone +33 6 14 
38 60 01 

armelle@desrequinsetdeshommes.org 

80 

80 

Figueiredo, 
Ivone 

Gadenne, 
Hélène 

Jung, Armelle 

 
 
 
 
 
 
 
 
 
 
 
Rihan, Dominic 
(by 
correspondance) 

Walker, Paddy 

PO Box 70F 

BLP/Technopôle 
Brest Iroise 

15 rue Dumont 
d'Urville 

29280  Plouzané 

France 
Bord Iascaigh 
Mhara,  
Crofton Road,  
Dun Laoghaire,  
Co Dublin,  
Ireland 

Van Hall 
Larenstein 
University of 
Applied 
Sciences,  

Agora 1, PO Box 
1528 

8901 BV  
Leeuwarden 

Netherlands 

Tel: +353 1 
2144159 

rihan@bim.ie 

Phone +31 6 
222 78 193  

paddy.walker@hvhl.nl 

JRC experts 

Name 

Address 

Telephone no. 

Scott, Finlay  DG Joint Research Center 

Email 
Finlay.SCOTT@ec.europa.eu 

European Commission 

Name 

Address 

Telephone no. 

Email 

Shrives, 
Jonathan 

European 
Commission 

jonathan.shrives@ec.europa.e
u 

Directorate-General 
for Maritime Affairs 
and Fisheries 

Unit C.1 – Fisheries 
Management, 
Atlantic North Sea 
and Baltic 

Scott, Finlay 

STECF secretariat 

JRC-stecf-
secretariat@ec.europa.eu 

81 

81 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
Observers 

Name 

Address 

Telephone no. 

Email 

Leblanc, Nicolas  Comité régionale 

des pêches de 
Normandie 

nicolas.leblanc@comite-
peches-normandie.fr 

Lynch, John 

NWWAC 

jleblana@hotmail.com 

c/o Bord Iascaigh 
Mhara Crofton Road 
Dun Laoghaire Co. 
Dublin, Ireland 

82 

82

11 LIST OF BACKGROUND DOCUMENTS

Background documents are published on the meeting’s web site on: 
https://stecf.jrc.ec.europa.eu/ewg1710  

List of background documents: 

EWG-17-16 – Doc 1 - Declarations of invited and JRC experts (see also section 10 of this report – 
List of participants) 

83 

83

84

L
B
-
A
X
-
1
7
-
0
2
1
-
E
N
N

-

STECF 

JRC Mission 

The  Scientific,  Technical 
and 
Economic  Committee  for  Fisheries 
(STECF)  has  been  established  by 
the  European  Commission.  The 
is  being  consulted  at 
STECF 
regular 
on  matters 
intervals 
pertaining  to  the  conservation  and 
living  aquatic 
management  of 
resources, 
including  biological, 
economic,  environmental,  social 
and technical considerations. 

of 

the  science  and  knowledge 
As 
service 
European 
the 
Commission,  the  Joint  Research 
Centre’s  mission  is  to  support  EU 
independent, 
policies 
evidence 
the  whole 
policy cycle. 

with 
throughout 

85

doi:10.2760/44133

ISBN 978-92-79-67493-8