Assessing spillover from marine protected areas to adjacent fisheries : Baltic and North Seas, Atlantic EU Western Waters and Outermost Regions : final report : annex 6 : case study reports.
Date: 2024-09-01
Institutions: European Climate, Infrastructure and Environment Executive Agency
Subjects: Atlantic Ocean, Baltic Sea region, EU waters, North Sea, biodiversity, case study, conservation of fish stocks, ecological footprint, environmental protection, exploitation of the seas, fishery management, fishery resources, marine ecosystem, marine environment, marine pollution, pollution control measures, protected area, protected species, resources of the sea

ASSESSING SPILLOVER FROM 
MARINE PROTECTED AREAS TO 
ADJACENT FISHERIES 

Baltic and North Seas, Atlantic EU 
Western Waters and Outermost Regions 

Final Report  

Annex 6: Case Study Reports 

European Maritime, Aquaculture and Fisheries Fund 
(EMFAF)

© Teuni Quirijns 

Written  by:  Lead  partners  -  Research  Institute  for  Agriculture,  Fisheries  and  Food  (ILVO),  Wageningen  Marine  Research  (WMR) 
(including Wageningen Economic Research), MRAG Limited Europe and MRAG Limited in consortium with: Technical University of 
Denmark (DTU); National Marine Fisheries Research Institute (NMFRI), Swedish University of Agricultural Sciences (SLU); Research 
Institute for Agriculture and Fisheries, Johann Heinrich von Thünen-Institute (TI); Institute of Marine Research (IMR), Fundación AZTI 
– AZTI Fundazioa (AZTI)  

July 2024 

 
EUROPEAN COMMISSION 

European Climate, Infrastructure and Environment Executive Agency 
Unit D3 — Sustainable Blue Economy 

Contact:  CINEA EMFAF CONTRACTS 

E-mail:   CINEA-EMFAF-CONTRACTS@ec.europa.eu  

European Commission 
B-1049 Brussels 
BELGIUM 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
EUROPEAN COMMISSION 

ASSESSING SPILLOVER FROM 
MARINE PROTECTED AREAS TO 
ADJACENT FISHERIES 

Baltic and North Seas, Atlantic EU 
Western Waters and Outermost Regions 

Final Report 

Annex 6: Case Study Reports 

Specific Contracts  

CINEA/EMFAF/2021/3.1.4/Lot1/02/SC11 

CINEA/EMFAF/2021/3.1.4/Lot2/01/SC11 

Implementing FWC EASME/EMFF/2018/1.3.2.3/011  

European Climate, Infrastructure and Environment Executive Agency 

 
This report should be cited as: 

Van  Hoey,  G.,  Feary,  D.A.,  Brown,  E.J.,  Buyse,  J.,  Mangi,  S.C.,  Vallina,  T.,  van  Kooten,  T.,  Abreu,  S., 
Aranda, M., Bergstrom, U., Castro, N., Kleiven, P.J.N., Mosnier, P., Peat, W., Rakowski, M., Robert, M., 
Stacy, R., Uriarte, A., Whitley, C., Wakeford, R.C., Quirijns, F.J. Assessing spillover from marine protected 
areas  to  adjacent  fisheries.  Baltic  and  North  Seas,  Atlantic  EU  Western  Waters  and  Outermost  Regions 
(SPILLOVER). Final Report. Annex 6. Publication Office of the European Union, 2024, doi: 10.2926/384994 

Author contributions: 

Van Hoey G. & Feary D.A.: project coordinators, report compilation, writing and reviewing. 
Brown E.J: systematic literature review, analyses and text writing, lead tasks 1 & 2. 
Buyse J.: systematic literature review, analyses and text writing, lead task 3, analyses and text writing of a 
case study. 
Mangi S.C.: stakeholder questionnaire development, analyses and text writing, lead task 5. 
Vallina T.: development advisory protocol, analyses and text writing of 2 case studies, lead task 5, analyses 
and text writing task 5. 
Van Kooten T.: SPILLEST tool development, analyses and text writing, lead task 4. 
Abreu S., Aranda M., Bergstrom U., Castro N., Kleiven P.J.N., Mosnier P., Peat W., Rakowski M., Robert 
M., Stacy R., Uriarte A., Whitley C.: analyses and text writing of case studies. 
Wakeford R.C. & Quirijns F.J.: consortia leads, overall review of the report. 

The information and views set out in this study are those of the author(s) and do not necessarily reflect the 
official  opinion  of  CINEA  or  of  the  Commission.  Neither  CINEA  nor  the  Commission  can  guarantee  the 
accuracy of the data included in this study. Neither CINEA, the Commission or any person acting on their 
behalf may be held responsible for the use that may be made of the information contained herein. 

Manuscript completed in July 2024 

This document should not be considered as representative of the European Commission’s official 
position.  

Luxembourg: Publications Office of the European Union, 2024 

© European Climate, Infrastructure + Environment Executive Agency, 2024 

The Commission’s reuse policy is implemented by Commission Decision 2011/833/EU of 
12 December 2011 on the reuse of Commission documents (OJ L 330, 14.12.2011, p. 39, 
ELI: http://data.europa.eu/eli/dec/2011/833/oj). 

Unless otherwise noted, the reuse of this document is authorised under the Creative Commons 
Attribution 4.0 International (CC BY 4.0) licence 
(https://creativecommons.org/licenses/by/4.0/). This means that reuse is allowed, 
provided appropriate credit is given and any changes are indicated. 

PDF/Volume_02 

ISBN 978-92-9405-126-4 

doi:10.10.2926/384994 

HZ-05-24-616-EN-N 

 
 
 
 
 
 
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

CONTENTS 

ANNEX 6: CASE STUDY REPORTS.................................................................................... 5 

1. 

THE GOTSKA SANDÖN MARINE PROTECTED AREA. SWEDEN – BALTIC SEA .................. 6 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ................................................................................................... 8 

BACKGROUND .............................................................................................................. 8 

AIMS AND OBJECTIVES ................................................................................................12 

METHODOLOGY ...........................................................................................................12 

RESULTS ....................................................................................................................14 

DISCUSSION ...............................................................................................................16 

CONCLUSIONS ............................................................................................................18 

REFERENCES ...............................................................................................................18 

APPENDIX ...........................................................................................................................19 

2. 

SŁOWIŃSKI AND WOLIŃSKI NATIONAL PARKS. POLAND – BALTIC SEA ....................... 20 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ..................................................................................................22 

BACKGROUND .............................................................................................................23 

AIMS AND OBJECTIVES ................................................................................................26 

METHODOLOGY ...........................................................................................................26 

RESULTS ....................................................................................................................28 

DISCUSSION ...............................................................................................................35 

CONCLUSIONS ............................................................................................................36 

REFERENCES ...............................................................................................................37 

APPENDIX ...........................................................................................................................38 

3. 

TVEDESTRAND MARINE PROTECTED AREA. NORWAY – SKAGERRAK ........................... 39 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ..................................................................................................41 

BACKGROUND .............................................................................................................41 

AIMS AND OBJECTIVES ................................................................................................43 

METHODOLOGY ...........................................................................................................44 

RESULTS ....................................................................................................................47 

DISCUSSION ...............................................................................................................50 

CONCLUSIONS ............................................................................................................51 
REFERENCES ...............................................................................................................52 

4. 

THE NORTH SEA COASTAL ZONE. THE NETHERLANDS – NORTH SEA .......................... 53 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ..................................................................................................55 

BACKGROUND .............................................................................................................55 

AIMS AND OBJECTIVES ................................................................................................58 

METHODOLOGY ...........................................................................................................58 

RESULTS ....................................................................................................................60 

DISCUSSION ...............................................................................................................63 

CONCLUSIONS ............................................................................................................64 

REFERENCES ...............................................................................................................64 

APPENDIX ...........................................................................................................................66 

5. 

BORSSELE OFFSHORE WIND FARM ZONE. THE NETHERLANDS – NORTH SEA .............. 67 

1 

EXECUTIVE SUMMARY ..................................................................................................69 

1 

Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

2 

3 

4 

5 

6 

7 

8 

BACKGROUND .............................................................................................................69 

AIMS AND OBJECTIVES ................................................................................................71 

METHODOLOGY ...........................................................................................................71 

RESULTS ....................................................................................................................74 

DISCUSSION ...............................................................................................................80 

CONCLUSIONS ............................................................................................................80 

REFERENCES ...............................................................................................................81 

6. 

THE BELGIAN OFFSHORE WIND FARM ZONE. BELGIUM – NORTH SEA ......................... 82 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ..................................................................................................85 

BACKGROUND .............................................................................................................85 

AIMS AND OBJECTIVES ................................................................................................88 

METHODOLOGY ...........................................................................................................90 

RESULTS ....................................................................................................................95 

DISCUSSION ............................................................................................................. 104 

CONCLUSIONS .......................................................................................................... 105 
REFERENCES ............................................................................................................. 106 

7. 

LYME BAY MARINE PROTECTED AREA. UK – THE ENGLISH CHANNEL ........................ 107 

1 

2 

3 

5 

6 

7 

8 

EXECUTIVE SUMMARY ................................................................................................ 110 

BACKGROUND ........................................................................................................... 110 

AIMS AND OBJECTIVES .............................................................................................. 113 

RESULTS .................................................................................................................. 115 

DISCUSSION ............................................................................................................. 121 

CONCLUSIONS .......................................................................................................... 122 

REFERENCES ............................................................................................................. 122 

8. 

THE FLAMANVILLE PROTECTED AREA. FRANCE – THE ENGLISH CHANNEL ................. 124 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ................................................................................................ 127 

BACKGROUND ........................................................................................................... 127 

AIMS AND OBJECTIVES .............................................................................................. 129 

METHODOLOGY ......................................................................................................... 129 

RESULTS .................................................................................................................. 133 

DISCUSSION ............................................................................................................. 141 

CONCLUSIONS .......................................................................................................... 144 

REFERENCES ............................................................................................................. 145 

9. 

THE ÉCRÉHOUS AND THE MINQUIERS. JERSEY – THE ENGLISH CHANNEL ................. 146 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ................................................................................................ 148 

BACKGROUND ........................................................................................................... 148 

AIMS AND OBJECTIVES .............................................................................................. 151 

METHODOLOGY ......................................................................................................... 152 

RESULTS .................................................................................................................. 153 

DISCUSSION ............................................................................................................. 157 

CONCLUSIONS .......................................................................................................... 158 

REFERENCES ............................................................................................................. 160 

10.  LAMLASH BAY AND SOUTH ARRAN. UK – CELTIC SEA ............................................. 161 

1 

2 

3 

EXECUTIVE SUMMARY ................................................................................................ 163 

BACKGROUND ........................................................................................................... 164 

AIMS AND OBJECTIVES .............................................................................................. 165 

2 

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Annex 6 - Case Study Reports 

4 

5 

6 

7 

8 

METHODOLOGY ......................................................................................................... 166 

RESULTS .................................................................................................................. 167 

DISCUSSION ............................................................................................................. 173 

CONCLUSIONS .......................................................................................................... 176 

REFERENCES ............................................................................................................. 177 

11.  ATLANTIC ISLANDS NATIONAL PARK OF GALICIA. SPAIN – THE IBERIAN COAST ....... 178 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ................................................................................................ 180 

BACKGROUND ........................................................................................................... 181 

AIMS AND OBJECTIVES .............................................................................................. 183 

METHODOLOGY ......................................................................................................... 183 

RESULTS .................................................................................................................. 184 

DISCUSSION ............................................................................................................. 187 

CONCLUSIONS .......................................................................................................... 188 

REFERENCES ............................................................................................................. 190 

12.  PROFESSOR LUIZ SALDANHA MARINE PARK. PORTUGAL – THE IBERIAN COAST ........ 191 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ................................................................................................ 193 

BACKGROUND ........................................................................................................... 193 

AIMS AND OBJECTIVES .............................................................................................. 196 

METHODOLOGY ......................................................................................................... 196 

RESULTS .................................................................................................................. 198 

DISCUSSION ............................................................................................................. 203 

CONCLUSIONS .......................................................................................................... 204 

REFERENCES ............................................................................................................. 205 

13.  FORMIGAS MARINE PROTECTED AREA. PORTUGAL – MACARONESIA ........................ 207 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ................................................................................................ 209 

BACKGROUND ........................................................................................................... 209 

AIMS AND OBJECTIVES .............................................................................................. 211 

METHODOLOGY ......................................................................................................... 211 

RESULTS .................................................................................................................. 212 

DISCUSSION ............................................................................................................. 214 

CONCLUSIONS .......................................................................................................... 215 

REFERENCES ............................................................................................................. 216 

14.  SELVAGENS ISLANDS MARINE PROTECTED AREA. PORTUGAL – MACARONESIA ......... 217 

1 

2 

3 

4 

5 

6 

7 

8 

EXECUTIVE SUMMARY ................................................................................................ 219 

BACKGROUND ........................................................................................................... 219 

AIMS AND OBJECTIVES .............................................................................................. 222 

METHODOLOGY ......................................................................................................... 222 

RESULTS .................................................................................................................. 223 

DISCUSSION ............................................................................................................. 226 

CONCLUSIONS .......................................................................................................... 227 

REFERENCES ............................................................................................................. 228 

15.  LA GRACIOSA MARINE PROTECTED AREA. SPAIN – MACARONESIA .......................... 229 

1 

2 

3 

4 

EXECUTIVE SUMMARY ................................................................................................ 231 

BACKGROUND ........................................................................................................... 231 

AIMS AND OBJECTIVES .............................................................................................. 235 

METHODOLOGY ......................................................................................................... 236 

3 

Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

5 

6 

7 

RESULTS .................................................................................................................. 239 

DISCUSSION ............................................................................................................. 246 

CONCLUSIONS .......................................................................................................... 247 

8 
REFERENCES ............................................................................................................. 248 
SUPPLEMENTARY INFORMATION ............................................................................... 250 

4 

 
 
 
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

ANNEX 6: CASE STUDY REPORTS 

Fifteen case studies in the Baltic Sea, North Sea, EU Atlantic Western Waters and some outermost 
regions (focusing on the Azores, Madeira and  Canary Islands) were selected to gather insights 
into potential spillover effects of different types of marine protected areas (MPAs) (Table 1). The 
majority of the case studies (11) is located in the European Union (EU) waters (Belgium, France, 
The Netherlands, Poland, Portugal, Spain and Sweden); four case studies are located in non-EU 
waters (Norway and the United Kingdom). 

In this case study work, besides studying typical MPAs, ‘other effective area-based conservation 
measures’ (OECMs), including offshore wind farms (OWFs) were also investigated, as they might 
be  as  relevant  in  the  study  of  spillover  effects.  OECMs  represent  geographically  defined  areas 
outside formal protected areas which contribute to positive and sustained long-term outcomes for 
the in situ conservation of biodiversity.  

The  selection  of  case  studies  was  made  mainly  based  on  geographical  coverage  and  data 
availability to assess potential spillover effects. The case studies are well-spread in the different 
sea basins, cover an array of Member States and nations, but also vary in the type of species 
(e.g. fish, crustacea, bivalves) and type of data that are available (e.g. fishery data, trap data, 
tagging  data,  capture-recapture  data).  In  the  case  studies,  the  spillover  effects  are  analysed 
based  on  qualitative  and/or  quantitative  analytical  approaches,  using  available  data  and/or  a 
stakeholder survey. 

Case studies on the assessment of potential spillover effects. The numbers in the first 
columns are hyperlinked to the relevant case studies. 

Nr   Case Studies 

Country 

Regional Sea 

1 

2 

3 

4 

5 

6 

7 

8 

9 

Gotska Sandön Marine Protected Area 

Sweden 

Baltic Sea 

Słowiński and Woliński National Parks 

Poland 

Baltic Sea 

Tvedestrand Marine Protected Area 

Norway 

Skagerrak 

North Sea Coastal Zone 

The Netherlands 

North Sea  

Borssele offshore wind farm zone 

The Netherlands 

North Sea  

Belgian offshore wind farm  

Belgium 

North Sea  

Lyme Bay Marine Protected Area 

United Kingdom 

English Channel 

Flamanville Protected Area 

The Écréhous and the Minquiers 

France 

Jersey 

English Channel 

English Channel 

10  Lamlash Bay and South Arran 

United Kingdom 

Celtic Sea 

11  Atlantic Islands National Park of Galicia 

Spain 

Iberian Coast 

12  Professor Luiz Saldanha Marine Park 

Portugal 

Iberian Coast 

13  Formigas Marine Protected Area 

Portugal 

14  Selvagens Islands Marine Protected Area 

Portugal 

15  La Graciosa Marine Protected Area 

Spain 

Macaronesia 

Macaronesia 

Macaronesia 

5 

 
 
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

1.  CASE STUDY REPORT: 

THE GOTSKA SANDÖN MARINE PROTECTED AREA 

SWEDEN – BALTIC SEA 

Juvenile turbot (Scophthalmus maximus), the main target species of the no-take zone at 
Gotska Sandön in the Baltic Sea. © Ulf Bergström 

Analysis of potential spillover effects from the 
Gotska Sandön MPA via larval export of flatfish  

Agnes Olin & Ulf Bergström 

Department of Aquatic Resources, Swedish University of Agricultural Sciences 

6 

 
 
 
 
 
 
 
 
 
 
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Annex 6 - Case Study Reports 

TABLE OF CONTENTS_ 

EXECUTIVE SUMMARY ............................................................................................ 8 
1 
BACKGROUND ....................................................................................................... 8 
2 
AIMS AND OBJECTIVES ......................................................................................... 12 
3 
METHODOLOGY .................................................................................................... 12 
4 
RESULTS ............................................................................................................. 14 
5 
DISCUSSION ....................................................................................................... 16 
6 
CONCLUSIONS ..................................................................................................... 18 
7 
8 
REFERENCES ....................................................................................................... 18 
APPENDIX ................................................................................................................... 19 

LIST OF ABBREVIATIONS 

Term 

CPUE 

NTZ 

SE 

Description 

Catch per unit effort 

No-take zone 

Standard error 

7 

 
 
 
 
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

1  EXECUTIVE SUMMARY  

In 2006, a 360 km2 no-take zone prohibiting all fishing activities was established around the island 
of  Gotska  Sandön  in  the  central  Baltic  Sea  (Sweden),  with  the  primary  aim  of  protecting  the 
flatfish nursery grounds in the area. Local populations of both turbot (Scophthalmus maximus) 
and Baltic flounder (Platichthys solemdali) initially responded positively to the establishment of 
the no-take zone  and  the densities remained  higher in  the no-take zone  in comparison  with  a 
fished reference area at the eastern coast of the island of Gotland.  

Previous  modelling  work  showed  that  larval  export  rates  from  the  no-take  zone  to  the  fished 
reference area could be substantial, suggesting that the reference area may benefit from spillover 
effects. The goal of this case study was to estimate the magnitude of the larval export from the 
no-take zone to the reference area for both turbot and Baltic flounder, based on monitoring data 
of densities and size structure in the no-take zone, as well as modelled larval export rates. The 
data consist of 5 years of gillnet survey data (2006−2009, 2021) providing catches per species 
and  size  group,  for  both  the  no-take  zone  and  the  reference  area.  The  previously  published 
modelled  larval  export  rates  are  based  on  particle-tracking  using  output  from  a  hydrodynamic 
model.  

Our results suggest that the  larval  export from  the no-take zone  to the  reference  area  is of a 
similar magnitude to the local larval production in the reference area, and in some years even 
larger in the case of flounder. As densities of both large flounder and large turbot in the no-take 
zone,  and  thus  also  larval  export  from  the  no-take  zone,  initially  increased  following  the 
establishment  of  the no-take  zone,  this  suggests  that  the  fishery  closure  may  have  generated 
spillover effects benefitting the flatfish populations and fisheries at the eastern Gotland coast. 

There  were  initially  some  positive  signs  in  fish  densities  and  landings  in  the  reference  area 
following the establishment  of  the  no-take zone, but  these  were not  consistent  across time or 
species. Lower densities of large flounder and large turbot in the early 2020s, compared to the 
time of establishment of the no-take zone, have likely resulted in reduced larval export to the 
reference area. No clear cause for the decline has been identified, but predation from seals and 
cormorants may have contributed. More years of data on the densities of flounder and turbot are 
needed to establish whether this is a stable long-term trend, or only interannual variation. 

Estimates  of  spatio-temporal  variability  in  egg  and  larval  mortality  rates,  as  well  as  empirical 
confirmation of the estimated contribution from the no-take zone to the reference area, would be 
helpful  for  better  assessing  spillover  effects.  In  a  wider  perspective,  our  results  suggest  that 
species with a pelagic drifting  phase will be  more  likely to generate spillover effects if no-take 
zones or other protective measures are implemented in areas with hydrodynamic conditions that 
favour dispersal to other suitable habitats.  

To sum up, the estimated spillover of flatfish larvae from the Gotska Sandön no-take zone to a 
fished  reference  area  at  Gotland  is  surprisingly  large,  especially  considering  the  long  distance 
between the no-take zone and the area benefitting from the larval export (ca. 100 km). However, 
due to declines in turbot and flounder densities in the no-take zone in recent years, this spillover 
effect may have diminished over time, and there are no clear signs of a positive long-term effect 
on flatfish densities and fishery landings in the reference area. Further empirical work would be 
necessary  to  verify  the  spillover  effect.  Nonetheless,  this  study  points  to  the  importance  of 
considering the ecological connectivity between areas to maximise the benefits of spillover effects 
on species with a pelagic drifting phase when designing a protected area.  

2  BACKGROUND 

A no-take zone (NTZ) was established around the island of Gotska Sandön in the central Baltic 
Sea  in  2006  (Figure  1;  see  Bergström  et  al.  2022  for  details).  The  NTZ  prohibits  all  types  of 
fishing, commercial and recreational, and was established as part of a government commission 
to introduce and evaluate the effects of NTZs on fish and fisheries in Swedish waters. The NTZ 
covers 360 km2 of soft sediments, the majority of it is sand. Gotska Sandön itself (44.9 km2) is a 
national  park,  and  the  surrounding  waters  are  part  of  the  Natura  2000  site  Gotska  Sandön-
Salvorev,  meaning  that  the  area  is  also  protected  from  construction  and  extraction.  The  main 
purpose of the Gotska Sandön NTZ is to protect local populations of flatfish, in particular turbot 
(Scophthalmus maximus), the endemic Baltic flounder (Platichthys solemdali) and the European 
flounder (Platichthys flesus), for which the area serves as important nursery grounds.  

8 

Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Figure 1: Map of the Gotska Sandön no-take zone (NTZ) and the location of each gillnet 
survey station in the NTZ and in a fished reference area on the eastern side of the island 
of Gotland. Inset shows the location of the NTZ within the Baltic Sea. From Bergström 
et al. 2022.  

The waters around Gotland have traditionally been one of the most important grounds for flatfish 
fisheries in the Baltic Sea. While flounder catches remained fairly constant during the 1990s and 
early 2000s, the catches of the more valuable turbot declined significantly during the period, likely 
as a result of the high fishing pressure (Florin et al. 2013). The recreational catches of flounder 
and turbot have been estimated to be of the same magnitude as the commercial landings (Florin 
et al. 2013). In recent years, the landings of both turbot and flounder have continued to decrease 
(Bergström et al., 2022), attributable to the decline in the coastal fishing sector. 

The fishing closure initially resulted in a significant increase in the densities of flounder and large 
turbot (with sizes of at least legal retention size: 21 cm and 30 cm, respectively) within the NTZ 
(Florin et al. 2013; Figures 2, 4−5). However, new data collected in 2021 show that Catch Per 
Unit of Effort (CPUE) in the NTZ was lower than just after establishment (2007-2009), in particular 
for  large  turbot  (Bergström  et  al.  2022;  Figures  2,  4−5).  CPUE  of  small  (smaller  than  30  cm) 
turbot  in  2021,  however,  was  similar  to  CPUE  just  after  NTZ  establishment  (Figure  3).  The 
development of the flatfish stocks in the NTZ has also been compared to the developments in a 
fished reference area off the east coast of the island of Gotland, located to the south of Gotska 
Sandön.  The  reference  area  was  chosen  because  its  habitat  is  similar  to  that  of  the  NTZ,  and 
fishing pressure in this area was expected to be relatively high (Florin et al. 2013). There is no 
comparable data on the fish stocks in the reference area prior to the fishing closure, but after the 
NTZ was established, it hosted higher densities of both large and small turbot compared to the 
reference area (Florin et al. 2013; Figures 2−3). Turbot in the NTZ were also older and displayed 
a  more  even  sex  ratio  (Florin  et  al.  2013).  Densities  of  flounder  were  also  higher  in  the  NTZ 
(Figures 4−5), although growth was slower, suggesting density-dependent growth (Florin et al. 
2013). The higher densities in the NTZ compared to the reference area have remained over time 
(Bergström et al. 2022; Figures 2−5). The CPUE of large turbot, however, was substantially lower 
in both areas during the last survey in 2021 compared to just after NTZ establishment. 

9 

 
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Annex 6 - Case Study Reports 

Figure 2: Mean catch per unit of effort for large turbot (above minimum legal landing 
size;  ≥30  cm  total length)  in  the  no-take  zone  and  reference  area.  Values  are  fourth 
square-root transformed numbers per station, mean ± SE. From Bergström et al. 2022. 

Figure 3: Mean catch per unit of effort for small turbot (below minimum legal landing 
size;  <30  cm  total length)  in  the  no-take  zone  and  reference  area.  Values  are  fourth 
square-root transformed numbers per station, mean ± SE, and adjusted for an effect of 
temperature. From Bergström et al. 2022. 

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Figure 4: Mean catch per unit of effort for large flounder (above minimum legal landing 
size;  ≥21  cm  total length)  in  the  no-take  zone  and  reference  area.  Values  are  fourth 
square-root transformed numbers per station, mean ± SE. From Bergström et al. 2022. 

Figure 5: Mean catch per unit of effort for small flounder (below minimum legal landing 
size;  <21  cm  total length)  in  the  no-take  zone  and  reference  area.  Values  are  fourth 
square-root transformed numbers per station, mean ± SE, and adjusted for an effect of 
temperature. From Bergström et al. 2022. 

11 

 
 
 
 
 
 
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Annex 6 - Case Study Reports 

3  AIMS AND OBJECTIVES 

As  the  estimated  larval  export  from  the  NTZ  to  the  flatfish  grounds  off  eastern  Gotland  is 
substantial,  it  has  been  hypothesised  that  the  establishment  of  the  NTZ  could  also  result  in 
spillover  effects  benefitting  flatfish  on  Gotland  (Florin  et  al.  2013).  Here,  we  combine  the 
estimated larval export rates from the NTZ with data on CPUE and size structure to calculate the 
magnitude of larval export from the NTZ to the reference area off eastern Gotland, and compare 
this estimate to the level of retention of larvae produced within the area. If there is an estimated 
net export of larvae from the NTZ to the reference area, we consider this as indicating a potential 
for ecological spillover. For context, we also present reported fishery landings in both the NTZ and 
the reference area. As the NTZ was introduced as part of a government programme to evaluate 
the effects of fishing closures on fish and fisheries, understanding not only the effects on the local 
populations but also potential  spillover effects  are  important as it  can  inform future policy  and 
management decisions.  

4  METHODOLOGY 

Monitoring in the NTZ and reference area 

Fish densities and size structure were surveyed by the Swedish University of Agricultural Sciences 
using 195 m multi-mesh gillnets, comprising 5×9 m sections of mesh size 25, 30, 38, 50 and 60 
mm and 3×50 m sections of 75, 100 and 120 mm meshes. The nets were deployed for one night 
in early June in 2006−2009 and in 2021, in 36 sampling stations in each area (NTZ and reference 
area).  However,  not  all  stations  provided  data  in  each  year  due  to  unfavourable  weather 
conditions or due to the equipment being tampered with, resulting in smaller actual sample sizes 
(Table  1).  All  caught  fish  were  identified,  counted  and  measured.  Catches  from  the  9  m  long 
sections of the net were standardized to 50 m section length to give the same effort for all mesh 
sizes. These data provide us with the number of fish caught per length per species per net. This 
can be interpreted as a form of density estimate. 

Table 1: Sample size by location and year 

Year 

2006 

2007 

2008 

2009 

2021 

No-take zone 

Reference area 

36 

35 

30 

36 

29 

30 

26 

36 

30 

30 

Temperature  affects  fish  activity  patterns,  meaning  that  it  also  affects  catch  rates.  Higher 
temperatures generally result in higher activity, and thus higher CPUE. An effect of temperature 
on the catch rate of small turbot and small flounder has previously been identified in the area, 
but no effect of temperature was identified for large turbot and large flounder (Bergström et al. 
2022). As we were only concerned with the larger, reproductive individuals, we ignored the effect 
of temperature here. 

There  are  two  closely  related  species  of  European  flounder  found  in  the  region;  the  offshore 
pelagic spawning flounder (Platichthys flesus) and the coastal benthic spawning Baltic flounder 
(Platichthys  solemdali).  During  the  monitoring  period  in  early  June,  Platichthys  flesus  are  still 
mainly offshore after spawning and therefore we consider most of the European flounder caught 
during sampling to be the coastal spawning Baltic flounder Platichthys solemdali. 

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Egg production 

Based  on  the  measured  lengths,  the  total  weight  of  each  fish  was  calculated  according  to  the 
following  length-weight  relationships,  as  implemented  in  the  Swedish  national  coastal  fish 
database: 

𝑡𝑢𝑟𝑏𝑜𝑡 𝑤𝑒𝑖𝑔ℎ𝑡 (𝑔) = 0.00689 × 𝑙𝑒𝑛𝑔𝑡ℎ(𝑐𝑚)3.30906 

𝑓𝑙𝑜𝑢𝑛𝑑𝑒𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 (𝑔) = 0.0138 × 𝑙𝑒𝑛𝑔𝑡ℎ(𝑐𝑚)2.9425 

We then re-calculated these total weights to somatic weights. This was done by combining length 
and somatic weight measurements on turbot  from  Nissling et al. (2013) and on flounder from 
Nissling and Dahlman (2010) with the estimated total weight based on the measured length and 
the equations above. From these data, we estimated the ratio between total weight and somatic 
weight  as  a  function  of  length  (see  Appendix),  and  then  applied  this  to  our  dataset  to  obtain 
somatic weights for each fish.  

Then, the potential fecundity (the estimated number of vitellogenic oocytes that are expected to 
result in spawned eggs in a given season) was calculated. Based on 128 fish caught pre-spawning 
in the Gotska Sandön NTZ, the reference area and a third location (Hoburgs Bank – also in ICES 
sub-division  28)  in  2010,  the  following  relationship  between  somatic  weight  and  potential 
fecundity has been calculated for turbot (Nissling et al. 2013): 

𝑡𝑢𝑟𝑏𝑜𝑡 𝑝𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝑓𝑒𝑐𝑢𝑛𝑑𝑖𝑡𝑦 = (𝑒7.745 + 𝑠𝑜𝑚𝑎𝑡𝑖𝑐 𝑤𝑒𝑖𝑔ℎ𝑡(𝑔)1.061) × 𝑠𝑜𝑚𝑎𝑡𝑖𝑐 𝑤𝑒𝑖𝑔ℎ𝑡(𝑔) 

Similarly, the relationship between somatic weight and potential fecundity of flounder was based 
on measurements of 136 pre-spawning Platichthys solemdali (at the time considered a coastally 
spawning  ecotype  of  the  species  Platichthys  flesus,  rather  than  a  separate  species),  collected 
2005−2006 (Nissling & Dahlman 2010). The following relationship was provided: 

𝑓𝑙𝑜𝑢𝑛𝑑𝑒𝑟 𝑝𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝑓𝑒𝑐𝑢𝑛𝑑𝑖𝑡𝑦 = 𝑒4.684 × 𝑠𝑜𝑚𝑎𝑡𝑖𝑐 𝑤𝑒𝑖𝑔ℎ𝑡(𝑔)1.042 × 𝑐𝑜𝑛𝑑𝑖𝑡𝑖𝑜𝑛−0.469 × 𝑜𝑜𝑐𝑦𝑡𝑒 𝑑𝑒𝑛𝑠𝑖𝑡𝑦0.368 

Since we had no data on condition or oocyte density, these were set to the average values for the 
fish  sampled  in  eastern  and  northern  Gotland  in  the  study,  0.863  and  11,630  (number  per  g 
gonad weight), respectively. 

Based on these equations and the measured lengths of all caught individuals, the total potential 
fecundity was calculated for each net. To correct for the fact that not all individuals are female, 
sex ratios female:male (Table 2; Florin et al., 2013) estimated for the NTZ and the reference area 
for larger sizes (≥30 cm turbots and ≥21 cm flounders) were multiplied by the estimated total 
potential fecundity. 

Table 2: Sex ratios female:male estimate for large (≥30 cm) turbot and large (≥21 cm) 
flounder,  based  on  measurements  from  the  NTZ  and  the  reference  area  (Florin  et  al. 
2013). 

Location 

Turbot (≥30 cm) 

Flounder (≥21 cm) 

No-take zone 

Reference area 

Larval export rates 

0.92 

0.73 

0.48 

0.52 

To estimate larval transport between the NTZ and the reference area, as well as retention rates 
within  each  area,  we  made  use  of  published  estimates  based  on  hydrodynamic  models  and 
particle-tracking  (Florin  et  al.,  2013).  Velocity  fields  were  produced  with  a  three-dimensional 
ocean circulation model, with a horizontal spatial resolution of 3.7 km and 84 depth intervals. The 
particle tracking used the velocity fields to calculate expected dispersal trajectories, with updates 
to  the  velocity  fields  at  3-hour  intervals,  and  tracking  calculations  performed  at  15-minute 
intervals. For each simulation experiment, 49 larvae were released in each of the 12 model grid 
cells around the NTZ and 49 larvae were released in each of the 73 grid cells in the reference 
area. This was repeated for 8 years (1995−2002) to cover a range of hydro-dynamic conditions. 

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In the calculations of larval dispersal, mean values for these years have been used. Turbot were 
assumed  to  begin  their  drifting  on  the  15th  of  June  and  drift  for  30  days,  while  flounder  were 
assumed to begin drifting on the 15th of April and drift for 60 days. Based on these simulations, 
averaging over two simulated drift depths (0−2 m and 12−14 m) and over the simulated years, 
the rate of export between the NTZ and the reference area, as well as the retention rate of each 
area, was calculated (Table 3). 

Table  3:  Probability  of  dispersal  between  the  NTZ  and  the  reference  area,  as  well  as 
probability of retention, for flounder and turbot based on particle tracking models (see 
Florin et al. 2013). The estimates represent mean values for years 1995−2002 and for 
two depth strata (0−2 m and 12−14m). The probabilities should be read from row (the 
source) to column (the destination). 

TO 

Turbot 

Flounder 

NTZ 

reference 

NTZ 

reference 

FROM 

NTZ 

0.11 

0.063 

0.05 

0.056 

Reference 

0.0006 

0.33 

0.001 

0.31 

Larval export from the NTZ to the reference area 

To estimate the relative larval export from the NTZ to the reference area (i.e., a potential spillover 
effect), the estimated potential fecundity per station per year from the NTZ was multiplied by the 
larval export rate from the NTZ to the reference area, for turbot and flounder respectively. To get 
one  value  per  year,  an  average  was  taken  across  stations  within  each  year.  Uncertainty 
boundaries  were  obtained  by  the  corresponding  standard  errors.  As  a  comparison,  the  same 
calculations were  repeated looking at  dispersal  from  the reference  area to the NTZ, as well  as 
retention rates within each area. 

5  RESULTS 

While the larval retention of the reference area was very high (see also Table 3), the estimated 
larval export from the NTZ to the reference area was of a comparable magnitude (Figure 6). In 
one  year,  the  estimated  export  from  the  NTZ  to  the  reference  area  was  even  higher  than the 
reference area’s retention for flounder, and for both flounder and turbot it was more than half of 
the retention rate in several years. The export from the reference area to the NTZ was consistently 
low, in line with the modelled export rates (Table 3).  

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Figure  6:  The  estimated  larval  dispersal  per  sampling  station  for  (a)  turbot  and  (b) 
flounder. Shape indicates direction, i.e. export (from the NTZ to the reference area or 
vice  versa)  or  retention  (from  the  NTZ  to  the  NTZ  or  from  the  reference  area  to  the 
reference  area).  Colour  indicates  the  source  population.  Points  represent  means  and 
error  bars  standard  errors,  as  estimated  from  the  variability  in  catches  between 
stations within each area (export rates were assumed to be constant across years). 

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6  DISCUSSION 

Our results suggest that  the potential larval export from the Gotska Sandön NTZ to the 
reference  area  on  the  east  coast  of  Gotland  was  of  a  comparable  magnitude  to  the 
larvae produced and retained within the reference area. This may seem surprisingly high, 
given the fairly long distance between the NTZ and the reference area (ca. 100 km), but can be 
explained by the higher overall larval production in the NTZ in combination with a clear directional 
transport of larvae towards the waters of Gotland south of the NTZ. Usually, spillover effects are 
mostly  considered  and  detected  at  a  local  scale,  up  to  ca.  800  m  (Halpern  et  al.  2009).  As 
densities  of  both  large  flounder  and  large  turbot  initially  increased  following  the 
establishment  of  the  NTZ  (Figures  2  and  4),  this  suggests  that  the  fishery  closure  has 
increased  the  larval  production  and  hence  spillover  to  the  flatfish  populations on  the 
east coast of Gotland (Figure 6). In line with this, densities of small turbot (i.e. possible 
recruits from the NTZ) increased initially after the establishment of the NTZ (Figure 3). 
However, no similar effect was seen in small flounder (Figure 5). With the exception of a 
small, temporary increase in the landings of turbot, there were no signs that a potential spillover 
effect had a positive effect on the fishery in the reference area (Figure 7 and 8). However, the 
number of fishers and the fishing  effort  in the reference  area  has been in decline, and flatfish 
landings cannot be used as a reliable estimate of fish availability.  

While the CPUE of both turbot and flounder remains higher in the NTZ compared to the 
reference  area  in  the  gillnet  survey,  there were  signs  that  densities  have  declined  in 
recent years, at least for large turbot (Figures 2−5). This is also reflected in the calculated 
larval  export  from  the  NTZ  to  the  reference  area,  which  in  the  most  recent years  are  back  to 
similar levels as at the establishment of the NTZ (Figure 6). The reason behind the declines is not 
clear, but predation from grey seals (Halichoerus grypus) and cormorants (Phalacrocorax carbo) 
may have contributed (Bergström et al. 2022). 

While  the  calculations  were  based  on  the  best  available  information,  the  estimated 
larval dispersal rates should be interpreted as a relative measure only. For example, we 
do not account for mortality during the egg or larval stage and how this may vary over time and 
space,  nor  do  we  take  year-to-year  variation  in  hydrodynamic  patterns  into  account.  Better 
estimates of spatio-temporal variation in egg and larval survival would improve our estimates, 
but  are  unlikely  to  drastically  alter  our  qualitative  conclusions.  A  more  recent  study  of  Baltic 
flounder dispersal around Gotland, but not including Gotska Sandön, suggests that drift depth has 
a large impact on where and how far the larvae drift (Corell & Nissling 2019). Drifting in the lower 
part of the water mass, at a similar depth to the preferred spawning depth, favours local retention 
and it may be that the larvae actively stay deeper in the water mass to increase the chance of 
remaining in suitable habitat along the coast.  

Further  studies  are  needed  to  establish  at  what  depth  the  Baltic  flounder  larvae  are  typically 
found, but if it is the case that the larvae tend to stay at lower depths, the larval export from 
Gotska Sandön may to some extent be overestimated in our study. At the same time, genetic 
studies of both turbot and demersal spawning flounder (now recognised as Platichthys solemdali) 
suggest that gene  flow across populations is high (Florin &  Höglund  2007;2008),  suggesting a 
high level of connectivity. As such, several sources of uncertainty remain, so in order to 
confirm our conclusions regarding the dispersal of larvae from the NTZ to the reference 
area,  and  to  assess  whether  these  contribute  to  the  spawning  population,  empirical 
studies  would  be  needed,  relying  on,  for  example,  high-resolution  genetic  data.  More 
years of monitoring are also needed to follow up the results from 2021, to ascertain whether the 
low densities observed are part of a long-term trend or only due to interannual variability. 

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Figure 7: Commercial landings per unit area per year of turbot (Scophthalmus maximus) 
in the no-take zone around Gotska Sandön (almost zero) and the fished reference area 
outside Gotland. From Bergström et al. 2022. 

Figure 8: Commercial landings per unit area per year of flounder (Platichthys solemdali) 
in the Gotska Sandön no-take zone (almost zero) and the fished reference area outside 
Gotland. From Bergström et al. 2022. 

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7  CONCLUSIONS 

The estimated larval export from the NTZ to the reference area was of a similar magnitude, and 
sometimes larger, than the local, retained larval production in the reference area. The high level 
of  larval  spillover  can  be  explained  by  the  higher  overall  larval  production  in  the  NTZ  in 
combination with a clear directional transport of larvae towards the reference area in the waters 
of Gotland. As densities of both large flounder and large turbot initially increased following the 
establishment of the no-take zone, this suggests that the fishery closure has increased the larval 
production and hence spillover to the flatfish populations in the reference area.  

There  were  initially  some  positive  signs  in  fish  densities  and  landings  in  the  reference  area 
following the establishment  of  the  no-take zone, but  these  were not  consistent  across time or 
species. Declines in the densities of large flounder and large turbot in recent years, likely to some 
extent connected to increasing populations of grey seals and cormorants, have likely resulted in 
reduced larval export to the reference area.  

Further work is needed both to establish whether the lower densities observed in recent years are 
part of a long-term trend and to confirm the magnitude of the dispersal rates empirically, but our 
approach  was  helpful  for estimating  the  potential  for  spillover  effects  via  larval  dispersal.  In  a 
wider perspective, our results point to the importance of considering the ecological connectivity 
between areas to maximise the potential spillover effects on species with a pelagic drifting phase 
when designing a protected area.  

8  REFERENCES 

Bergström,  U.,  Berkström,  C.,  Sköld,  M.  (eds.),  Börjesson,  P.,  Eggertsen,  M.,  Fetterplace,  L.,  Florin,  A-B., 
Fredriksson, R., Fredriksson, S., Kraufvelin, P., Lundström, K., Nilsson, J., Ovegård, M., Perry, D., Sacre, 
E.,  Sundelöf,  A.,  Wikström,  A.,  Wennhage,  H.  (2022).  Long-term  effects  of  no-take  zones  in  Swedish 
waters. Aqua reports 2022:20. Swedish University of Agricultural Sciences. 289 pp.  

Corell, H., Nissling, A. (2019). Modelling of larval dispersal of Baltic flounder (Platichthys solemdali) revealed 
drifting depth as a major factor determining opportunities for local retention vs large-scale connectivity. 
Fisheries Research, 218, 127−137. doi.org/10.1016/j.fishres.2019.05.010 

Florin,  A.-B.,  Bergström,  U.,  Ustups,  D.,  Lundström,  K.,  Jonsson,  P.R.  (2013).  Effects  of  a  large  northern 
Journal  of  Fish  Biology,  83,  939−962. 

flatfish  populations. 

European  no-take  zone  on 
doi.org/10.1111/jfb.12097 

Florin, A.-B., Höglund, J. (2007). Absence of population structure of turbot (Psetta maxima) in the Baltic Sea. 

Molecular Ecology, 16, 115−126. doi: 10.1111/j.1365-294X.2006.03120.x 

Florin,  A.-B.,  Höglund,  J.  (2008).  Population  structure  of  flounder  (Platichthys  flesus)  in  the  Baltic  Sea: 

differences among demersal and pelagic spawners Heredity, 101, 27−38. doi.org/10.1038/hdy.2008.22 

Halpern,  B.S.,  Lester,  S.E.,  Kellner,  J.B.  (2009).  Spillover  from  marine  reserves  and  the  replenishment  of 

fished stocks. Environmental Conservation, 36, 268−276. 

Nissling, A., Dahlman, G. (2010). Fecundity of flounder, Pleuronectes flesus, in the Baltic Sea — Reproductive 
190−198. 

of  Sea  Research, 

populations. 

Journal 

64, 

in 

strategies 
two 
doi.org/10.1016/j.seares.2010.02.001 

sympatric 

Nissling,  A.,  Florin,  A.-B.,  Thorsen,  A.,  Bergström,  U.  (2013).  Egg  production  of  turbot,  Scophthalmus 
maximus, in the Baltic Sea. Journal of Sea Research, 84, 77−86. doi.org/10.1016/j.seares.2012.07.009 

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APPENDIX 

Figure A1: Points show (a) the reported minimum and maximum lengths of turbot (Nissling et 
al. 2013) and (b) the reported minimum, median and maximum lengths of flounder (Nissling & 
Dahlman 2010), plotted against (a) the corresponding reported minimum and maximum somatic 
weights of turbot (Nissling et al. 2013) and (b) the corresponding reported minimum, median and 
maximum somatic lengths of flounder (Nissling & Dahlman 2010), divided by the estimated total 
weight  based  on  the  measured  lengths  and  published  relationships  between  length  and  total 
weight (see main text). The black lines show fitted linear models.  

The fitted linear models (Figure A1) provided the following relationships: 

𝑡𝑢𝑟𝑏𝑜𝑡 𝑠𝑜𝑚𝑎𝑡𝑖𝑐 𝑤𝑒𝑖𝑔ℎ𝑡 𝑡𝑜𝑡𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡

⁄

= 1.08 − 0.008 × 𝑙𝑒𝑛𝑔𝑡ℎ(𝑚𝑚) 

𝑓𝑙𝑜𝑢𝑛𝑑𝑒𝑟 𝑠𝑜𝑚𝑎𝑡𝑖𝑐 𝑤𝑒𝑖𝑔ℎ𝑡 𝑡𝑜𝑡𝑎𝑙 𝑤𝑒𝑖𝑔ℎ𝑡

⁄

= 1.09 − 0.00109 × 𝑙𝑒𝑛𝑔𝑡ℎ(𝑚𝑚) 

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2.  CASE STUDY REPORT: 

SŁOWIŃSKI AND WOLIŃSKI NATIONAL PARKS 

POLAND – BALTIC SEA 

Fishing vessel leaving port of Lubin (community Międzyzdroje, near 
Woliński National Park) to collect nets. Photo: M Rakowski 

Analysis of potential spillover effects 
around the Słowiński and Woliński 
National Parks 

Marcin Rakowski, Adam Mytlewski 
National Marine Fisheries Research Institute (NMFRI) 

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TABLE OF CONTENTS 

5 

1 
2 
3 
4 

EXECUTIVE SUMMARY ........................................................................................... 22 
BACKGROUND ...................................................................................................... 23 
AIMS AND OBJECTIVES ......................................................................................... 26 
METHODOLOGY .................................................................................................... 26 
4.1  Quantitative approach .................................................................................. 26 
4.2  Qualitative approach .................................................................................... 27 
RESULTS ............................................................................................................. 28 
5.1  Quantitative research................................................................................... 28 
Catch analysis ............................................................................................. 28 
Desk research and literature studies .............................................................. 30 
5.2  Qualitative research ..................................................................................... 32 
Response of the managing authorities and park authorities .............................. 34 
Response of the fishermen, NGO’s and science stakeholders ............................. 34 
DISCUSSION ....................................................................................................... 35 
6 
CONCLUSIONS ..................................................................................................... 36 
7 
8 
REFERENCES ....................................................................................................... 37 
APPENDIX ................................................................................................................... 38 

LIST OF ABBREVIATIONS 

Term 

DCA 

DCF 

JCWP 

MPA 

NMFRI 

WFC 

Description 

Detrended correspondence analysis 

Data Collection Framework 

Jednorodnych Części Wód Powierzchniowych  

(homogenous surface water bodies) 

Marine protected area 

National Marine Fisheries Research Institute 

Water Framework Directive 

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1  EXECUTIVE SUMMARY  

This case study aims to evaluate the potential spillover effects around two marine protected areas 
(MPAs), namely the Słowiński National Park and the Woliński National Park, located in the Polish 
marine areas of the Baltic Sea. The marine areas, covered by the park boundaries, are two nautical 
miles along the 33 km coast of Słowiński National Park and one nautical mile along the 17 km of 
the  coast  of  the  Woliński  National  Park.  Since  2005,  the  Minister  of  the  Environment  has 
separately  issued  a  ‘regulation  on  protective  tasks’  for  each  national  park.  Then,  within  these 
marine areas, only ‘cultural fishing’ based on licences was allowed. Fishing took place in shallow 
water by local fishers using boats and passive gears. The establishment of these MPAs did not 
change the area used by fisheries and the number of vessels registered in the ports around parks 
were stable in the past 10 years.  

To study the potential effects of spillover from the Słowiński National Park and Woliński National 
Park to adjacent areas, a quantitative method was applied based on total catches in  the Baltic 
Sea fishing squares where the MPAs are located, for the period 2014-2023. Due to a lack of more 
detailed quantitative information, this was the only spatial resolution that could be used in the 
analysis. The low spatial resolution resulted in the data covering a much larger area than that 
within  the  parks'  boundaries  and  challenged  the  detection  of  potential  spillover  in  the  areas 
surrounding the MPAs. Nevertheless, declining trends in total volume of fish catches in the study 
areas over the years, indicate that spillover from the MPAs is unlikely. A more in-depth analysis 
of the 2019-2023 catch data would be required, however additional events in that period of time 
are likely to have affected catches, i.e. the cod ban, the Covid-19 pandemic, and the Russian war 
of aggression against Ukraine.  

Another approach to study potential spillover effects in this case study used  desk research and 
interviews with key stakeholders. Four focus group meetings with fishers took place in which, in 
total,  22  fishermen  participated.  Also,  seven  surveys  were  conducted,  with  nine  respondents, 
including  scientists,  environmental  non-governmental  organisations  and  a  fisherman.  MPA 
managers  (from  the  Słowiński  National  Park)  and  government  fishery  authorities  completed  a 
questionnaire  prepared  for  both  areas  of  this  case  study.  The  fishermen  of  the  focus  group 
demonstrated a high degree of social responsibility and understanding of the MPA’s operation, as 
reflected  in  the  strong  convergence  between  their  statements  and  those  of  other  study 
participants. 

The survey indicates that there have been no perceptible spillover effects of the two MPAs, most 
likely due to the small marine  surface  and the relatively short period since the introduction of 
restrictions.  The  fishery  sector  considered  that  MPAs  are  neither  a  conservation  nor  a  fishery 
management  tool,  contrary  to  what  they  expected.  Currently,  fishers  claim  that  the 
implementation of the MPAs increases the cost of fishing activities due to access fees and the time 
needed  for  reporting.  They  see  that  the  volume  of  catches  has  not  increased  since  the 
implementation of the MPAs, and the MPAs have no significant impact on the economy of fishers 
and their revenue. Current conditions are acceptable to fishers and the fishers see no need for 
permanent closure of the MPAs for fishing. In their opinion, to create some spillover effect for the 
small marine areas of these parks, other tools such as temporary closures during spawning season 
and limitations of gear types and number of gears should be implemented. MPAs may be seen as 
advantageous for the condition of fish stocks by limiting the number of fishers active in the area. 
Additionally, in the parks the natural growth of aquatic plants, which limit catching opportunities, 
creates a ‘natural’ protection for the fish species. 

Park authorities and scientists claim that MPAs already are or will be a conservation tool and a 
fisheries  management  tool  at  the  same  time.  They  see  positive  effects  on  the  environment, 
biodiversity and fish stocks health conditions. In their opinion, the spillover effect will be seen in 
a few more years and will apply mostly to the young stages of fish. The Protection Plans for the 
Słowiński National Park and Woliński National Park are still under development and the current 
protective tasks do not result in a decrease in fishing activity. Therefore, in the current situation 
it is too early to expect spillover effects. Additionally, the parks are small, reducing the probability 
of spillover effects. A robust quantitative analysis of spillover effects currently is challenging, and 
would require more detailed data and targeted studies. 

22 

 
 
 
 
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2  BACKGROUND 

This case study covers two marine protected areas (MPAs): the Słowiński National Park and the 
Woliński National Park. Both MPAs were established as national parks and included land areas and 
inland bodies of water. Słowiński National Park has as its primary task the protection of coastal 
dunes,  while  Woliński  National  Park  has  as  its  primary  task  the  protection  of  the  cliffside  and 
forest complex of Wolin Island. In 1996, the areas of Woliński National Park and in 2004 Słowiński 
National  Park  were  expanded  to  include  the  nearshore  strip  of  sea  waters  and,  in  the  case  of 
Woliński National Park, the adjacent waters of the Szczecin Lagoon. In both cases, this measure 
was  primarily  for  the  sake  of  coastline  protection.  The  managers  conducted  environmental 
assessments of the new areas, inventoried the flora and fauna resources present and introduced 
regulations for the use of the areas. 

Both national parks are part of a larger protected area. For these larger areas, there are Plans of 
Protective Tasks (see Appendix), describing the conservation regulations. For both national parks, 
Protection  Plans  (see  Appendix)  are  currently  being  developed,  describing  conservation 
regulations  for  marine  areas.  These  Protection  Plans  have  a  higher  priority  than  the  Plans  of 
Protective Tasks.  

The similarities in management, the size of the marine areas covered by the boundaries of these 
parks  and  the  advancement  of  the  creation of  regulations,  as  well  as  the  results of  interviews 
conducted  with  stakeholders  in  these  areas,  formed  the  basis  for  combining  the  results  into  a 
single case study instead of presenting two separate case studies. 

The Słowiński National Park (Figure 1) is located on the Central Coast of Poland, between the 
ports of Rowy and Łeba. The park was created to protect swamps, marshes, coastal lakes, forests 
and  meadows  and  especially  the  dune  belt  of  the  spit  with  moving  dunes  that  are  unique  in 
Europe. It was established on January 1, 19671, with an area of 18 618 ha, of which 10 213 ha 
are  water  areas  and  4  599  ha  include  terrestrial  forest  areas.  Strict  protection,  meaning  the 
absolute  and  permanent  elimination  of  human  intervention  in  the  state  of  ecosystems,  covers 
5 619 ha in total (including both water and land surface). In 1977, Słowiński National Park was 
recognized as a UNESCO World Biosphere Reserve. In 20042 the area was enlarged by 14 675 ha, 
including 11 000 ha of surface waters (a strip 33 km long and two nautical miles wide, with a 
maximum depth of 20 m). Since then, the park  covered an area of 32 744 ha. The Baltic  Sea 
water  area  is  characterised  by  a  sandy  bottom,  prone  to  changes  caused  by  sea  currents  and 
wave action. The relatively stable area, which is the western part of the park waters, is home to 
brown, red and green algae, as well as mussels and barnacles. In this area, fish species common 
for the Baltic Sea are found (mostly flounder, turbot and herring). Seals and porpoises are also 
found in the area. 

The Woliński National Park (Figure 2) is located in the western part of the Polish Baltic Sea 
coast,  between  the  ports  of  Międzyzdroje  and  Dziwnów  and  Lubin  on  the  side  of  the  Szczecin 
Lagoon (Zalew Szczeciński). The park was established in 19603 and, at the time, it covered an 
area of 4 844 ha on Wolin Island. In 19964, the marine waters, the waters of the Szczecin Lagoon, 
and the archipelago of coastal islands in the delta of the old riverbed of Świna were included in 
the park area, making Woliński National Park the first marine park in Poland. The current surface 
area of the park is 10 937 ha, including aquatic ecosystems of 4 681 ha. A one nautical mile wide, 
17 km-long strip of cliff coastline east of Międzyzdroje is included in the park’s boundary, as are 
areas of Lake Wicko and a part of the Szczecin Lagoon, which are used for fishing activity. 

The aquatic areas in the southern part of Woliński National Park are a refuge for phytoplankton 
and phytobenthos, as well as rush vegetation and reed beds, while the marine area of the park 
has  the  character  of  a  sandbank  with  occurring  rock  covered  with  green,  red  and  brown 
macroalgae. Among the ichthyofauna, 61 species were identified, including lampreys (2 species), 
migratory fish (4), marine fish (22) and freshwater fish (33)5. 

1  Rozporządzenie  Rady  Ministrów  z  dnia 23  września 1966  r.  ws.  utworzenia Słowińskiego  Parku Narodowego  (Dz.U. z 1966 r.  nr 42, 

poz. 254). 

2 Rozporządzenie Rady Ministrów z dnia 2 marca 2004 r. w sprawie Słowińskiego Parku Narodowego (Dz.U. z 2004 r. nr 43, poz. 390) 
3 Rozporządzenie Rady Ministrów z dnia 3 marca 1960 r. ws. utworzenia Wolińskiego Parku Narodowego (Dz.U. z 1960 r. nr 14, poz. 79) 
4 Rozporządzenie Rady Ministrów z dnia 3 stycznia 1996 r. w sprawie Wolińskiego Parku Narodowego (Dz.U. 1996 nr 4 poz. 30). 
5 https://wolinpn.pl/przyroda-parku/ekosystemy-wodne/ 

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Figure 1: Map of the area of the Słowiński National Park (Olczyk et al 2011). 

Figure 2: Map of the area of the Woliński National Park (Olczyk et al 2011).   

24 

 
 
 
 
 
 
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As described above, for both national parks a Protection Plan is under development. Until these 
Protection Plans are implemented, a decree describing conservation tasks is in place. Every three 
years since 2005, the minister responsible for environment protection issued a separate regulation 
on protective tasks for each national park. The current decree for the Słowiński National Park for 
2023-20256 is the Decree of the Minister of Climate and Environment dated December 28, 2022, 
on the protective tasks. For the Woliński National Park, the current decree is the Decree of the 
Minister of Climate and Environment dated January 13, 2023, amending the Decree on protective 
tasks for the Woliński National Park for 2020-20237
. The documents specify, among other things, 
protective  actions  in  aquatic  ecosystems.  The  indicated  method  of  active  protection  in  marine 
waters is as follows for the Słowiński National Park:  

‘Protection of the resources of the Baltic Sea - maintenance of cultural fishing carried out 
by the inhabitants of the communities where the Słowiński National Park is located with 
the help of boats of an overall length not exceeding 10 m, from the home ports in Łeba 
and Rowy’.  

Meanwhile, for the Woliński National Park, the indicated objectives have changed:  

‘1. Controlling the performance of fishing in marine waters including jointly with the Sea 
Fisheries Inspector,  
2. Protection of habitats and fauna sites and preservation of species diversity by limiting 
the availability of Woliński National Park water areas for fishing and recreation,  
3. Protection of habitats and sites of aquatic flora and preservation of species diversity by 
limiting the availability of Woliński National Park water areas for fishing and recreation,  
4. Monitoring of surface waters’.  

The  Baltic  Sea  area  within  the  boundaries  of  the  parks  is  designated  as  an  ‘active 
protection area’. 

An important element for evaluating potential spillover effects for both MPAs is the fishing activity 
potentially present in the study area. Commercial fishing in the area up to 3 nautical miles from 
the shore is limited to vessels up to 12 m in length fishing with passive gears. Trawls and other 
towing  gears  are  not  allowed  in  this  3-miles  zone.  As  shown  in  Table  1,  the number  of  active 
commercial vessels in the ports around the parks was stable in the past 10 years. Not all of vessels 
were allowed to operate in the National Park areas: only cultural fishing is allowed in the marine 
areas of the parks, by residents of the municipalities where the park is situated (see description 
of cultural fishing in Appendix). Fishing is carried out with boats of an overall length not exceeding 
12 metres, from home ports in Łeba, Rowy (Słowiński National Park) and Dziwnów, Międzyzdroje, 
Lubin,  Świnoujście  Przytór,  Świnoujście  Karsibór  (Woliński  National  Park).  Furthermore,  the 
regulations governing cultural fishing in the parks are determined by internal directives issued by 
the park directors. To be added to the list of authorized entities conducting cultural fishing within 
the  National  Park's  territory,  fishers  must  apply,  and  each  permission  is  subject  to  an 
administrative fee of 100 zł (approximately €25). Obtaining permission for cultural fishing in the 
marine waters within the parks'  boundaries  requires  an individual  permit from the  Director.  In 
2024,  the  permit  of  the  Director  of  the  Słowiński  National  Park  is  held  by  seventeen  vessels. 
Eleven of these vessels’ home port is Łeba; six of these vessels’ home port is Rowy. Permits from 
the Director of the Woliński National Park are held by a total of twelve vessels, from the ports of 
Lubin (4), Międzyzdroje (3), Świnoujście Przytór (2), Świnoujście Karsibór (1), Świnoujście (1), 
and  Dziwnów  (1).  Fishers  are  bound  by  EU  and  national  law.  Furthermore,  the  parks  have 
introduced additional restrictions. The fishing gear consists exclusively of set nets. The minimum 
distance for spacing fishing gear from the shore must be at least 200 meters. Fishing for sea trout 
and  Atlantic  salmon  is  permitted  from  January  1  to  September  14.  Commercial  fishing  with  a 
fishing rod from fishing boats is not permitted. 

6 https://dziennikurzedowy.mos.gov.pl/fileadmin/Dziennik_Urzedowy/user_upload/ZO_Slowinski_PN_2023-

25_zarzadzenie_do_podpisu_MKiS.xml.xades  

7 https://dziennikurzedowy.mos.gov.pl/fileadmin/Dziennik_Urzedowy/user_upload/DO_PODPISU_-_ZZO_Wolinski_PN_2020-

23_zarzadzenie.xml.xades 

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Table 1. Number of active commercial vessels (<12m) at the end of each year in ports 
around Woliński National Park and Słowiński National Park (2013-2023). 

MPA 
Woliński 
NP 

Port 
Wolin 

Lubin 
Świnoujście-Przytór 
Świnoujście-Karsibór 
Międzyzdroje 
Dziwnów 

Woliński NP Total 
Słowiński 
NP 

2013  2014  2015  2016  2017  2018  2019  2020  2021  2022  2023 
15 
15 

14 

15 

14 

15 

15 

15 

15 

15 

13 

8 
4 
7 
4 
13 
49 

8 
4 
10 
4 
14 
54 

8 
4 
9 
4 
14 
54 

8 
4 
9 
4 
13 
53 

8 
4 
9 
4 
13 
53 

8 
4 
9 
4 
13 
53 

8 
4 
9 
4 
14 
53 

7 
4 
9 
4 
14 
53 

7 
4 
9 
4 
14 
53 

8 
4 
9 
4 
14 
54 

8 
4 
9 
4 
14 
54 

Rowy 
Łeba 

Słowiński NP Total 

6 
19 
25 
Total 
79 
Source:  National Marine Fisheries Research  Institute  (NMFRI) elaboration  on  data from Fishing Fleet Register and  Fishery 
Monitoring Centre of Department of Fishery of The Ministry of Agriculture and Rural Development, Poland. 

6 
18 
24 
78 

6 
19 
25 
79 

6 
19 
25 
78 

6 
20 
26 
79 

6 
18 
24 
77 

6 
18 
24 
77 

6 
18 
24 
77 

6 
17 
23 
76 

6 
18 
24 
73 

6 
18 
24 
78 

3  AIMS AND OBJECTIVES 

The main objective of this  case study was to evaluate the  potential spillover effects of the fish 
resources  around  the  seawaters  of  the  Słowiński  National  Park  and  Woliński  National  Park.  A 
quantitative and a qualitative approach was used to do this.  

The quantitative approach aimed to study trends in catches and changes in fishing vessel numbers 
(as a proxy for effort) in the area. The hypothesis was that if MPAs should create spillover effects, 
it could potentially be detected by positive trends in the catches  per unit of effort  in the areas 
surrounding the MPAs (see also Annex 5, Advisory Protocol, Table 28).  

The  qualitative  approach  aimed  to  study  stakeholders’  perceptions  on  potential  spillover  effect 
from the MPAs, by assessing stakeholders’ level of knowledge about MPA regulations and their 
socio-economic  impacts,  particularly  related  to  fisheries;  assessing  MPAs'  perceived  role  as 
management and or fishery conservation tool; identifying key factors linked to spillover effects, 
according to stakeholders.  

4  METHODOLOGY 

Two approaches were used to study the potential spillover effects: a quantitative analysis to look 
at trends in catches inside and outside of the MPAs and a qualitative analysis using interviews to 
assess stakeholder perceptions on spillover effects. Due to lack of publications on this topic in the 
area,  the  literature  review  was  marginal  and  focused  on  environmental  effects  of  the  MPA 
implementation.  

4.1  Quantitative approach 

The  quantitative  analysis  relied  on  commercial  catches  within  designated  Baltic  Sea  fishing 
squares  (see  Appendix)  corresponding  to  each  respective  park's  location.  Specifically,  for 
Słowiński National Park, these squares are N6 and M6, and for Woliński National Park, it is square 
D1  (Figure  3).  Unfortunately,  a  more  comprehensive  spatial  analysis  of  catches  is  currently 
unfeasible  due  to  the  absence  of  higher  resolution  data,  such  as  GPS  data.  Only  data  from 
commercial vessels using passive gear and with a maximum length of 12 m were considered, as 
these are the only vessels allowed in the area and the primary operators in the coastal zone. 

The Baltic Sea fishing squares grid is a scale commonly used to locate fishing grounds in the Baltic 
Sea (Figure 3). It is used in fishing logbooks and statistical studies. This grid comprises parallels 
spaced  at  10  geographic  minutes  and  meridians  spaced  at  20  geographic  minutes,  forming 
standardized  "squares"  with  dimensions  of  10  x  11.5  nautical  miles  (nm).  These  squares  are 
designated from west to east with alphabetical letters (A through Z) and from south to north with 
numerical values (1 through 31). 

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Annex 6 - Case Study Reports 

Figure 3 Baltic Sea fishing squares grid with marked squares (in green) bordering the 
two national parks (Source: National Marine Fisheries Research Institute). 

Given the stable number of vessels recorded in the relevant ports (Table 1), catch volume was 
used as the primary parameter in the catch analysis. A sustained increase in the overall weight 
of species caught within the Baltic Sea fishing squares corresponding to the parks could potentially 
indicate of spillover effect, while maintaining a constant vessel  number (see Annex 5, advisory 
protocol, for more details). It should be noted that the catch volumes may have been influenced 
by other events: first, there was the cod fishing ban, effective as of mid-2019. Second, the Covid-
19 pandemic impacted the market and value chain between 2020-2023. And finally, the Russian 
war of aggression against Ukraine resulted in increased costs. 

4.2  Qualitative approach 

The qualitative research methodology employed for this case study encompassed desk research 
and interviews conducted with key stakeholders. The structured questionnaire aimed to delve into 
the perceptions of both users and authorities regarding the presence of designated areas and the 
potential  spillover  effects  within  the  MPAs.  To  accommodate  variations  in  expertise  among 
representatives  of  four  stakeholder  groups  (fishers,  MPA  managers  and  authorities,  scientists, 
and environmental non-governmental organizations), the questionnaire (Annex 4) was tailored in 
different formats.  

Comprising three sections, the questionnaire sought to comprehensively explore various facets: 

1.  Background: aiming to gain insights into the respondents' backgrounds and affiliations. 
2.  Fishery Impact: examining the respondents' perspectives on the socio-economic implications 

of MPA spillover. 

3.  Management  Tool:  gauging  the  respondents'  views  regarding  the  efficacy  of  MPAs  as 

management and conservation tools. 

After  identifying  30  potential  respondents,  primarily  through  established  leaders  within  local 
harbours, relevant organizations, and administrative bodies, additional stakeholders were enlisted 
through  a  'snowball  effect',  leveraging  existing  contacts  to  expand  the  participant  pool. 
Subsequently, the questionnaire forms were disseminated to the management institutions of the 
MPA sites (such as the Management of Słowiński National Park and the Management of Woliński 
National Park), as well as governmental bodies like the Department of Fishery within the Ministry 
of Agriculture and Rural Development. 

Following  telephone  interviews  with  representatives  from  environmental  organizations  and 
scientific communities, the questionnaire forms were forwarded to these groups as well, soliciting 
their input to corroborate statements. The bulk of responses were received during July 2023, with 
some arriving in early August 2023. 

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A  different  approach  was  adopted  to  engage  fishers  who  initially  declined  to  fill  out  the 
questionnaires  independently.  Responding  to  requests  from  fishermen  in  specific  ports 
surrounding the MPAs, a series of four group interviews were organized, conducted as meetings 
in the ports situated around the protected areas. These meetings took place between July 20th 
(around the area of Woliński National Park) and July 27th (around the area of Słowiński National 
Park)  of  2023.  The  format  of  these  meetings  mirrored  the  questionnaire  prepared  for  fishers, 
facilitating a greater level of participation from the fishing sector. This approach yielded positive 
results, with fourteen fishers from three ports surrounding Słowiński National Park (Łeba, Ustka, 
and Rowy) and nine fishers from three ports surrounding Woliński National Park (Dziwnów, Wolin, 
and Lubin) participating in the meetings. In total, we received 5 questionnaires from the fishery 
sector. An individual interview request was declined by a fisherman from the port of Międzyzdroje.  

In total, the study involved 31  respondents (Table 2),  comprising one representative from  the 
park  authorities,  23  fishers,  two  representatives  of  the  scientific  community  and  two 
representatives  of  non-governmental  environmental  organisations.  Furthermore,  respondents 
from three different departments within the Department of Fisheries of the Ministry of Agriculture 
and Rural Development returned the questionnaire. The research was conducted in the period of 
July and August 2023.  

Table 2. Number of respondents and methods in Słowiński National Park & Woliński 
National Park Case Study Qualitative research. 

Group of respondents 

Managing Authorities 
Park Authorities 
NGO's 
Scientists 
Fisherman 

Number of 
questionnaires 
1 
1 
2 
2 
1 

Number of 
respondents 
3 
1 
2 
2 
1 

Fishermen 
Total 

4 
11 

22 
31 

Technique 

Online questionnaire 
Online questionnaire 
Online questionnaire 
Online questionnaire 
Online questionnaire 
Focus groups in ports (based 
on questionnaire) 

5  RESULTS 

5.1  Quantitative research 

Catch analysis 

Fishery is an activity which may be potentially affected by MPA establishment.  Given the stable 
number of vessels observed in the analyzed areas over the past decade (Table 1), an analysis of 
catch volume emerges as a preferred indicator for assessing the potential spillover effect resulting 
from MPA establishment.  

Figure 4 shows the volume of commercial fish catches from 2014 to 2023, by vessels with lengths 
lower than 12 meters, in the Baltic Sea fishing squares where the MPAs are located. In the area 
of  Pomorska  Bay,  where  Woliński  National  Park  is  located,  mostly  fishing  vessels  up  to  12  m 
length using passive gears are active. Catches decreased over the studied period, both in square 
D1 (covering waters within the boundaries of Woliński National Park) and in squares M6 and N6 
(covering waters of Słowiński National Park). In terms of species composition in square D1, the 
dominant  species  in  the  catch  were  roach,  bream  and  perch  (32%,  25%  and  13%  in  2023, 
respectively). In squares M6 and N6, cod (57%) and flatfish (30%) dominated the catch in 2014. 
The  cod  fishing  ban  was  implemented  in  May  2019,  and  after  that,  in  2023,  catches  were 
dominated by flatfish (75%) and herring (20%). 

28 

 
 
 
 
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Słowiński NP.
Linear (Słowiński NP.)

Woliński NP.
Linear (Woliński NP.)

R² = 0.756

R² = 0.6282

s
e
n
n
o
T

800

700

600

500

400

300

200

100

0

2014

2015

2016

2017

2018

2019

2020

2021

2022

2023

Year

Figure 4. Catches of fish of the fleet up to 12 m in length, in Baltic Sea fishing squares 
D1 (covering waters of the Woliński National Park) and M6, N6 (covering waters of the 
Słowiński National Park) in years 2014-2023. 

Since 2017, the Polish fishery has undergone a notable reorientation away from cod toward other 
fish  species.  This  shift  was  prompted  by  significant  reductions  in  available  quotas  for  cod, 
culminating in the eventual imposition of a total ban on cod catches. The exclusion of cod catches 
from the analysis has allowed for the identification, to some extent, of changes in the volume of 
fish  catches  from  year  to  year  (see  Figure  5,  presenting  catches  excluding  cod).  The  trend  in 
catches  in  areas  adjacent  to  the  Woliński  National  Park  has  remained  relatively  stable,  with  a 
slight decline observed. This is largely attributed to cod constituting a small portion of the overall 
catch composition (with at a maximum of 2% between 2014 and 2019). Conversely, the ban on 
cod fishing has had a more pronounced impact on catches in squares M6 and N6, which encompass 
the fisheries around the Słowiński National Park. There, an increasing trend in catches was evident 
as early as 2018. One notable observation is the significant increase in catch volume of flounder, 
which tripled from 87 thousand tonnes in 2017 to 234 thousand tonnes in 2018. This surge can 
be attributed to the use of similar fishing gears employed in cod fishing. However, this increase 
was  not  sustained  in  subsequent  years,  indicating  a  decline.  Additionally,  herring  catches 
increased, although this required changes in fishing gears and vessel adjustments. 

29 

 
 
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Słowiński NP.
Linear (Słowiński NP.)

Woliński NP.
Linear (Woliński NP.)

R² = 0.7625

R² = 0.21

s
e
n
n
o
T

800

700

600

500

400

300

200

100

0

2014

2015

2016

2017

2018

2019

2020

2021

2022

2023

Year

Figure 5. Catches of fish (without cod) of the fleet up to 12 m in length, in fishing Baltic 
Sea  fishing  squares  D1  (covering  waters  of  the  Woliński  National  Park)  and  M6,  N6 
(covering waters of the Słowiński National Park) in years 2014-2023. 

The  interpretation  of  the  results  of  this  quantitative  analysis  is  complicated  by  disruptions  in 
fishing activities after 2019, related to restrictions on cod fishing and the temporary suspension 
of fishing during the Covid-19 pandemic. Also, increased energy costs related to the Russian war 
of aggression against potentially had an impact on fleet activity. 

Desk research and literature studies 

Findings of our desk research show that there is a lack of relevant data analyses or publications 
describing the spillover effects in these areas. Consequently, the authors of the report drew upon 
many studies conducted during the formulation of the Protection Plan for each respective area. 
For the maritime areas of both National Parks, these studies were limited to inventories of flora 
and fauna species, as well as assessments of physical and chemical conditions of water within the 
administrative boundaries of the respective National Park. The information in these studies were 
used to determine the conservation tasks within the MPAs. 

The  Nature  Protection  Act8  underscores  that  the  National  Park  is  the  highest  form  of  nature 
protection in Poland, and all nature and landscape values are protected. The Act does not explicitly 
indicate a catalog of protection activities, but obliges the Director of the National Park to develop 
a Protection Plan. This Protection Plan has to include specific elements aimed at facilitating the 
development of a robust protection concept for inventoried elements, assessing potential threats, 
and, most importantly, delineating the type, scope, and location of protection measures. In the 
Protection Plans, measures for fisheries are the limitation of the number of vessels, geographical 
origin of vessels, and elimination of the trawling fishing technique.  

Based  on  monitoring  data  from  2014-2019,  an  assessment  of  the  ecological  status  and 
classification of surface waters was carried out in 2020 (Anon, 2020). Of the 4 047 homogenous 
surface  waterbodies  (JCWP)  in  marine  areas,  studies  were  conducted  in  19  JCWPs,  mainly 
transitional waters (Szczecin Lagoon, Vistula Lagoon, individual parts of the Gulf of Gdansk) and 
coastal waters. It  should  be noted that  according to the typology of waters resulting from  the 

8 Ustawa z dnia 16 kwietnia 2004 r. o ochronie przyrody, tekst jedn. Dz.U. z 2018 r. poz. 1614 z późn. zm. 

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Water Framework Directive  of the European Union  (WFD  2000/60/EC9), coastal waters include 
the area of surface waters from the shoreline, the outer boundary of which is determined by a 
distance of one nautical mile on the seaward side, calculated from the baseline. In the case of 
coastal waters, the following elements were assessed:  

• 
• 
• 

biological (phytoplankton, macroalgae and angiosperms, benthic invertebrates);  
hydro-morphological (tidal regime, morphological conditions);  
physicochemical (biogenes, oxygen conditions, transparency, temperature), specific synthetic 
pollutants and specific non-synthetic pollutants.  

The research of water quality (Anon, 2020) has been prepared for all coastal waters in Poland and 
generally  indicates  poor  ecological  status  (54%  very  bad,  38%  poor  and  8%  moderate).  The 
condition was poor also in parts of the waters of the two national parks of this study.  

No  separate  catch  statistics  are  collected  for  protected  areas,  which  is  another  obstacle  to 
assessing  the  impact  of  MPAs  on  fish  stocks.  Despite  the  small  marine  areas  covered  by  the 
boundaries  of  the national  parks,  representatives  of  the  Ministry  consider these  zones  to  be  a 
conservation tool, and park authorities also consider them to be part of the fishery management 
tool.  

In 2015, Smoliński and Całkiewicz proposed a fish-based index for assessing the ecological status 
of Polish transitional and coastal waters, with initial trials conducted in both parks (Smoliński & 
Całkiewicz,  2015).  This  initiative  arose  in  response  to  EU  directive  for  Member  States  to  take 
responsibility for water quality control, recognizing the significant anthropogenic impact on these 
environments. Utilizing fish as bioindicators, which are reliable proxies for evaluating water quality 
and specific components, the authors proposed a multimetric fish index inspired by the Helcom 
Baltic Sea Impact Index, tailored to assess the condition of coastal and transitional waters. 

Data on the ecosystem of coastal waters in Poland were collected, selected and analyzed during 
the years 2011, 2013, and 2014. For all fish specimens utilized for testing, species identification 
took  place  and  weight  and  length  were  measured.  Freshwater  species  dominated  the  dataset, 
comprising 94% of observations. Detrended correspondence analysis (DCA) showed that salinity 
was the most important environmental factor affecting the fish community. While transitional and 
coastal waters theoretically serve as excellent habitats, owing to their brackish salinity, they also 
function as unique feeding grounds for freshwater fish. However, field observations revealed that 
both  the  Słowiński  National  Park  and  Woliński  National  Park  are  subject  to  substantial 
anthropogenic pressure, which adversely affects the environment and fish stocks. This impact is 
reflected in the diminished number of species within these ecosystems (Smoliński and Całkiewicz 
2015).  A  decline  in  the  overall  species  richness  in  aquatic  ecosystems  typically  indicates  a 
deterioration in habitat condition. 

Margoński (2016) conducted a basic analysis of the impact of environmental conditions on fish 
recruitment in the Baltic Sea. The variability of recruitment of some species (sprat) was analyzed 
taking  into  account  spring  water  temperature,  intensity  of  ice  cover  and  the  North  Atlantic 
Oscillation.  However,  environmental  changes  are  so  dynamic  and  significant  that  analytical 
models cannot include these changes in long-term forecasts. 

In  conclusion,  the  existing  literature  on  the  potential  effects  of  MPAs  in  influencing  the 
environment and fish stocks in the two investigated MPAs and more widely in Poland is notably 
scarce. The studies available, where coastal protected areas in Poland were mentioned, primarily 
focus  on  environmental  aspects,  with  limited  research  scale  and  methodology.  Consequently, 
there is a noticeable absence of benchmark data necessary for studying spillover effects in the 
future. 

9  Directive  2000/60/EC  of  the  European  Parliament  and  of  the  Council  of  23  October  2000  establishing  a 
framework  for  Community  action  in  the  field  of  water  policy  -  https://eur-lex.europa.eu/legal-
content/en/ALL/?uri=CELEX%3A32000L0060 

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5.2  Qualitative research 

The  responses  gathered  from  interview  participants  and  focus  group  attendees  revealed  a 
divergence of opinions, often aligning with the expectations and perspectives of their respective 
industries: fishery, tourism, environmental protection entities, and others. Notably, during group 
interviews with fishers, the majority emphasized the challenges in assessing the impact of these 
small MPA areas on both fish resources and the local economy. Many local fishermen asserted 
that there is insufficient scientific evidence supporting the need for protection of these specific 
areas. They contended that the marine areas were included in the park primarily for the protection 
of the coastline rather than for the preservation of marine habitats. 

The viewpoints expressed by fishers, scientists, environmental organizations, managing and park 
authorities  collectively  suggest  that  it  is  too  early  to  discern  the  results  of  MPA  management 
actions for both MPAs. Additionally, due to the limited availability of data and publications on this 
issue,  it  remains  premature  to  observe  tangible  outcomes  from  these  management  actions. 
Therefore, there is a clear need for enhanced exchange of information among the various entities 
involved  in  managing  and  benefiting  from  the  MPAs.  The  structured  results  of  the  qualitative 
survey are summarized in Table . 

Evaluation  of  the  spillover  effects  is  difficult  due  to  the  unavailability  of  data  and  the  lack  of 
scientific research in this area (e.g. scientific publications). According to fishers the MPAs have 
not affected adjacent fishing areas. Both fishers from ports around the Woliński National Park and 
the Słowiński National Park indicated that these particular MPA areas are too small, although even 
such an area can contribute to improving resources. On the one hand, they should be as large as 
possible to protect nature on the other hand, they should not be too large to avoid limiting fishing 
activities too much.  

The protected areas are small and established in areas that, according to representatives of the 
fishing sector, do not have sufficient effects beyond increasing the operating costs of the fishing 
fleet. Interviews showed that for park authorities and fishermen, MPAs are perceived as a tool for 
both  biodiversity  conservation  and  fisheries  management.  Managing  authorities,  eNGOs  and 
scientists perceive the MPA to be a biodiversity conservation tool. Fishers do not see these parks 
as a significant barrier for fishing, as the small depths of the area had naturally eliminated large 
vessels and active fishing methods. 

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Table 3. Views expressed by stakeholders in response to the qualitative survey.  

Stakeholder 

Any changes since 
the MPA 
implementation? 
Social perception 

MPA implementation measures: size, 
regulation advancement 

MPA as biodiversity 
conservation or 
fisheries management 
tool? 

Catches change/ 
Biomass? Species 
composition? 

Economic benefit for fisheries 

Biodiversity protection/ 
Larvae habitat? 

Managing Authorities  Not enough data, too 

No data/publications on this issue  

Conservation tool 

preliminary to see 
results 

No data/publications on this 
issue 

No data/publications on this issue 

No data/publications on this 
issue 

MPAs would help to benefit fisheries 
communities only in case there are a 
lot of options around/outside an MPA 
to fish and MPA itself has a fisheries 
closure large enough to generate 
spillover effects that could be 
profitable for fishermen around 

Spillover effects could help 
fisheries, but only in case 
fisheries closure would be 
large enough 

Hard to say, no expertise 

Park Authorities 

Correlated with the 
overall negative trends 
in catches on Baltic 
Sea 

Regulations for fisheries in the National 
Parks were established in 2010 and have 
not been changed. Changes are 
connected to general regulations. 

Conservation and 
management tool 

No data on this issue, but 
decrease of numbers of fish 
is similar to what happens in 
the whole Baltic Sea 

Temporal cessation of fleet may be 
one of the issue for smaller catch. 
Anyway, limitation of number of 
vessels may positively impact local 
fleet up to 12 m (having permission) 

NGO's 

Positive changes in 
habitat 

Area of the marine area of the single park 
is too small to impact, but with other, 
bigger MPAs there should be a positive 
impact on the environment (cumulative 
effect) 

Conservation tool, but in 
case of National Parks 
hard to assess impact 

No data. In recent years 
many species are 
overfished 

It is too early, but protection should 
economically benefit fisheries in the 
future 

No data, but protection of 
habitat should benefit to that 

Scientists 

Changes are more 
likely to be caused by 
climate change 

Size of MPA and time of implementation 
of protection is crucial  

Conservation tool, but 
both approaches support 
each other 

Establishing of MPAs 
should lead to improved 
environmental parameters. 
No research on this matter  

Area of National Parks is not very 
important for commercial species. 
Local fishermen are neutral to MPA, 
but owners of bigger segments of 
fleet are concerned the area may be 
expanded 

Even if positive effect 
occurs, its extent is small 
and it would need time to be 
noticeable and to impact a 
bigger area 

Fishermen 

No changes or   
changes due to other 
causes (i.e. overall 
condition of fish stocks 
in Baltic Sea)  

Effectiveness of protection of marine 
waters of national parks is low. The areas 
are too small and there is a more strict 
protection of predators (seals, 
cormorants). More important for fish 
protection are temporary closures and 
limitations of gear types and number of 
gears 

It acts as both 
management tool (3 
respondents) and 
conservation tool (2 
respondents) 

Not at all (no changes in 
catches). 

MPA didn’t bring economic benefits 
and livelihood security (all 
respondents). They didn’t see 
changes 

For sure it may help to 
protect and enhance 
biodiversity, but for most 
commercially important 
species other areas are 
important. 

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Response of the managing authorities and park authorities 

Ministry representatives highlighted that a team of employees actively contributed to crafting the 
responses  to  the  questionnaire,  ensuring  comprehensive  coverage  and  accuracy  from  the 
perspective  of  the  Fishery  Department.  The  ministry  representatives  perceive  that  MPAs  are  a 
conservation tool. They referred to the impact of the MPAs on the promotion of restoration of fish 
resources and thus on fisheries economics. In almost every answer they also highlighted the short 
duration of the  restrictions, which  do not allow  for estimating  spillover  effects  at  this point.  In 
their opinion, the MPA implementation process in Poland is in most cases too preliminary to see 
effects of the MPA. And in relation to management, the measures taken so far are limitations on 
certain fisheries and temporary area closures in spawning season. These measures are seen as 
sufficient to achieve protection for different species. Note that there is no scientific monitoring of 
catches  in  the  MPA  area  and  data  collected  under  the  Data  Collection  Framework  (DCF)  are 
aggregated, so it is challenging to have specific data on changes in fish species occurrence due 
to the MPA measures. Fishers have to send monthly reports of catches and by-catch (birds, seals, 
porpoises) to the park’s authorities, and these reports are used as a monitoring tool for protection 
of birds and mammals.   

The  issue  of  the  national  park’s  function  as  an  MPA  was  described  quite  thoroughly  by  a 
representative  of  the Słowiński National  Park. His answers showed  substantial  experience  with 
the functioning of fisheries in areas  both  inside  and  outside the MPA. He often referred to the 
relatively small area of the MPA under the jurisdiction of the Słowiński National Park; the generally 
weak condition of fishing opportunity in the Baltic Sea; and the limitation of users that is almost 
in line with the natural needs of local fishers. He claimed that fisheries are a natural activity. The 
park does not harm the business. 

Response of the fishermen, NGO’s and science stakeholders 

A  great  deal  of  information  was  contributed  by  group  interviews  from  the  surrounding  ports. 
Fishers  from  Dziwnów,  Wolin,  Lubin,  Ustka,  Rowy  and  Łeba  responded  similarly,  focusing  on 
assessing  the  impact  of  the  establishment  of  the  MPAs  on  their  work.  Everywhere,  the  fishers 
agreed that, apart from a few administrative duties and the cost of obtaining permission, they 
had not radically changed their nets’ staging locations. They also pointed to non-obvious, non-
planned  effects  of  environmental  changes  that  will  potentially  have  an  impact  on  resource 
protection. 

Representatives  of  NGOs  mainly  pointed  to  the  slowness  of  establishing  mandatory  Protection 
Plans  for MPAs, confirming  the limited area  of parks in marine areas  and  the lack of plans for 
other  established  protected  areas.  They  emphasised  the  long  process  needed  for  creating  the 
conditions to stimulate potential spillover effects from MPAs. 

In  general,  respondents  from  the  fishery  sector  and  scientific  community  asserted  that  MPAs 
neither solely serve as conservation tools nor exclusively as fishery management tools; rather, 
they represent a blend of both functions, mutually reinforcing each other. While MPAs do impose 
additional costs on fishery activities through access fees and reporting requirements, these costs 
are generally perceived as negligible. However, due to their limited spatial extent, none of the 
described MPAs have resulted in a noticeable spillover effect, or if such an effect exists, it cannot 
be reliably measured. Fishers perceived that the volume of catches has not increased since the 
establishment of the MPAs, and MPAs have no impact on the economy of fishers and their revenue. 
Despite this, the livelihoods of local fishers have not become more secure, although some fishers 
acknowledge that the limitation of vessel numbers in the MPA area could be viewed positively. 
Moreover, it was noted that all local fishers interested in accessing this area have been granted 
approval by the park authorities. 

The  current  conditions  for  exercising  protection  of  marine  waters  and  their  resources  are 
acceptable to fishers, who see no need to permanently close MPA areas to fishing. The established 
rules for the use of the areas of these MPAs are not seen as restrictions by local fishers, as these 
rules do not limit fishers’ rights for catching, and from the point of view of park managers, the 
rules  allow  control  of  fishing  volumes,  by-catch  and  sightings  of  birds,  marine  mammals  and 
lampreys through the reporting system. Fishers pointed to the impact of water plant protection 
regulations in the areas of national parks. The growth of water plants has made fishing impossible 
in many areas due to the risk of damaging equipment (net clogging with macroalgae or seagrass). 
At the same time, fishers have identified areas in the border of the national parks as potentially 
important  areas  for  fish  spawning  (not  species-specific).  Given  the  challenges  in  catching  fish 

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within areas rich in macroalgae or seagrass, these regions have naturally evolved into  ‘natural’ 
protection zones, avoided by fishers. 

According to respondents from the three groups (fishermen, NGOs and science stakeholders), the 
potential  spillover  effect  of  the  small  areas  can  be  viewed  as  supportive  of  fish  habitats, 
understood as the creation of conducive conditions for reproduction and the survival of juveniles. 
However, fishermen place greater emphasis on alternative tools, such as the temporary closure 
of  certain  areas  (not  necessarily  associated  with  the  MPA)  during  spawning  seasons  and 
regulations pertaining to the restriction of fishing gear. Remarkably, this perspective aligns closely 
with that presented by the managing authorities, indicating that communication between various 
stakeholders involved in marine resource utilization is at an appropriate level. This suggests that 
management  decisions  are  made  in  consultation  with  stakeholders,  facilitating  a  collaborative 
approach to sustainable marine resource management in the investigated areas. 

6  DISCUSSION 

The study of spillover effects in Poland is pioneering, yet limited by the lack of reference points in 
both literature (scientific research) and statistics (e.g. catch data). The knowledge on coastal area 
protection does not provide a methodology to extrapolate the results of the studies to a broader 
context, particularly to Polish MPAs. The literature  did not include  any specific aspects of 
the parks but focused only on the overall characteristics like: salinity, anthropogenic impact 
or  interaction  with  invasive  species,  environmental  protection  and  role  of  coastal  areas  in 
protecting biodiversity. The literature does not give any result on the characteristics of the MPA 
or effects of the management actions on nature restoration or potential spillover. The authors of 
this study underscore the necessity of a scientific survey in this area to assess effectiveness of 
park implementation and its impact on adjacent areas. This scientific inquiry could be juxtaposed 
with  insights  from  stakeholder  interviews,  where  it  was  suggested  that  multispecies 
mechanisms in relatively small coastal areas may not be easy to evaluate (Novaczek et 
al. 2017). While discussions can draw upon general studies on marine environment quality and 
the function of coastal areas for fish habitat and reproduction, it is imperative that such studies 
reference larger areas or MPA networks (Berkström et al. 2022). The disparities between studies 
should be acknowledged and discussed to provide a comprehensive understanding of the subject 
matter.  

Data  collected  under  the  DCF  focuses  on  the  so-called  Baltic  Sea  fishing  squares,  which  give 
challenges in any scientific analysis that would aim to separate data according to the boundaries 
of  the  MPAs.  This  limitation  was  underscored  by  respondents  from  fisheries  managers,  park 
authorities, scientists, and NGOs, who highlighted the lack of knowledge to effectively assess and 
promote  these  MPAs  as  conservation  tools.  The  aim  of  development  in  this  area  is  data 
aggregation adjusted to the needs of management purpose. During interviews, it became 
evident that the absence (or limitation) of data significantly influences the perception of the role 
of national parks in marine areas. Consequently, social perception and knowledge about the role 
of MPAs, including the changes they bring, are limited among local fisheries (Silva & Lopes, 2015). 
The  marine  areas  within  the  national  parks  are  not  perceived  as  an  important  conservation 
measure by them. No Protection Plan has yet been established for any MPA in Poland. Although 
areas  within  national  parks  are  in  the  advanced  stages  of  drafting  Protection  Plans,  general 
regulations remain in force in practice. Environmental organizations, scientists and fishers share 
a  similar  opinion.  There  is  a  prevailing  belief  that  the  two  approaches  —  conservation  and 
management  tools  —  mutually  support  and  amplify  each  other,  demonstrating  a  consensus 
among various stakeholders regarding the multifaceted role of MPAs. 

The  advancement  of  regulations  and  their  implementation  for  MPAs  is  still  in  the 
preparation phase. Even the assessment of MPAs and their associated potential spillover effects 
is impacted by the fact that the regulation of MPA operation as part of national parks has not been 
finalized and implemented. The designation of areas without the establishment of Protection Plans 
undermines their proper functioning. According to the Polish regulation10, National Parks, being 
legal entities, are obliged to prepare such plans. Moreover, they benefit from special regulations 

10 Ustawa z dnia 16 kwietnia 2004 r. o ochronie przyrody (tekst jednolity: Dz.U. z 2021 r. poz. 

1098 z późn. zm.) 

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limiting access of economic activities and visitors. In the long term, there is a need to assess the 
efficiency of regulation in the protected areas (Kriegl at al. 2021).  

The  economic  impact  of  the  establishment  of  protected  areas  was  not  perceived  by 
fishers. Instead, they link the decline in fishing income to the general condition of fish resources 
in the Baltic Sea. There was even a comment that a much more important area for improving the 
environmental situation  (considered  by  fishers  as improving  cod  stocks) is the Bornholm  Deep 
(see Appendix), and that small and shallow areas such as those in the MPAs in this case study 
are of minor importance. The sentiment among fishers regarding reduced profit due to MPAs was 
echoed by the park authority of the Słowiński National Park. Conversely, respondents from the 
science  sector  and  environmental  organizations  believe  that  the  economic  situation  of  fishers 
should  be  enhanced  through  the  establishment  of  protected  areas  and  would  need  time  to  be 
noticeable.  

The  results  of  the  catch  analysis  were  corroborated  by  interviews  with  fishermen. 
Fishers perceived that the volume of catch did not increase since the establishment of 
the MPAs, and that MPAs have no observed impact on the economy of fishers and their revenue 
(Leleu  et  al.  2012).  They  indicated  that,  for  economic  reasons,  they  were  compelled  to  seek 
alternative  species  to  replace  lost  income  from  cod  fishing.  Consequently,  it  is  not  feasible  to 
attribute  the  increase  in  catches  of  other  species  in  the  Słowiński  National  Park  to  a  potential 
spillover  effect.  Similarly,  analyses  of  catches  and  interviews  in  the  Woliński  National  Park 
confirmed the predominance of an economic approach in fisheries behaviour.   

7  CONCLUSIONS 

Park authorities and scientists acknowledge that MPAs are or will be simultaneously conservation 
and management tools. They see positive effects on the environment, biodiversity and fish stock 
health conditions. The spillover effect is expected to be seen in a few more years, and it will apply 
mostly to the young stages of fish. However, fishers have different views, and these expectations 
are not currently supported by scientific research and publications. 

The  literature  does  not  give  any  insights  on  the  characteristics  of  the  MPA  or  effects  of  the 
management  actions  on  fish  stocks  and  potential  spillover  effects.  In  addition,  the  analysis  of 
potential spillover effects requires detailed data and targeted biological and economic studies to 
allow spatial and temporal modelling of both the occurrence of fish schools, as well as the size, 
geographic dispersion and species composition of catches. Currently, the aggregated nature of 
fishing  catch  volume  data  poses  challenges  in  assessing  spillover  effects  based  solely  on  this 
information. 

Protection  Plans  for  the  Woliński  National  Park  and  Słowiński  National  Park  are  still  under 
development.  They  are  based  on  an  inventory  of  the  parks'  resources  and  scientific  advice. 
However, the parks primarily focus on protecting the terrestrial environment, with the coastal sea 
area  regarded  as  a  form  of  shore  protection.  The  areas  encompassed  by  the  borders  of  these 
national  parks  are  perceived  by  respondents  as  too  small  to  have  an  impact  on  commercially 
exploited  fish  stocks.  This  was  corroborated  by  the  assessments  of  scientists  and  managing 
authorities, who also recognize a lack of knowledge and public awareness on the matter. 

There  is  a  need  of  scientific,  targeted  research  to  verify  the  effectiveness  of  park’s 
implementation.  The  current  scientific  studies  address  mostly  the  effects  of  environmental 
protection on water bodies, the role of coastal areas in the protection of biodiversity, and related 
topics.  New  research  on  the  effects  of  protection  on  commercial  fish  species  within  and 
surrounding the investigated and Polish MPAs, including on spillover, will motivate and educate 
stakeholders, and promote MPAs as a long-term management tool.  

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8  REFERENCES 

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wykonanej za 2019 rok na podstawie danych z lat 2014-2019, Główny Inspektorat Ochrony Środowiska 
Warszawa. 

Berkström, C., Wennerström, L. & Bergström, U. (2022) Ecological connectivity of the marine protected area 
network in the Baltic Sea, Kattegat and Skagerrak: Current knowledge and management needs. Ambio 
51, 1485–1503 (2022). https://doi.org/10.1007/s13280-021-01684-x 

Kriegl  M,  X.E.Ilosvay,  von  Dorrien  Ch.,  Oesterwind  (2021),  Marine  Protected  Areas:  At  the  Crossroads  of 
Nature Conservation and Fisheries Management. Front. Mar. Sci., 08 June 2021, Sec. Marine Conservation 
and Sustainability, Volume 8 - 2021 | https://doi.org/10.3389/fmars.2021.676264 

Leleu K., Alban Frédérique, Pelletier D., Charbonnel E., Letourneur Y., Boudouresque C. F. (2012), Fishers' 
perceptions as indicators of the performance of Marine Protected Areas (MPAs), Marine Policy, Volume 36, 
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Marchowski  D.,  Łąwicki  Ł.,  Kaliciuk  J.  (2022), Management  of  Marine  Natura 2000  Sites  as  Exemplified  by 
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Margoński P. (2016) Czynniki środowiskowe warunkujące rekrutację ryb w południowym Bałtyku  – kierunki 
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Marine Protected Areas to Regional Biodiversity: The Example of a Small Canadian No-Take MPA. Front. 
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Silva M.R.O., Lopes P. F.M. (2015)  Each fisherman is different: Taking the environmental perception of small-
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APPENDIX 

This Appendix contains a description of key terms used in the case study report.  

Term 

Description 

Active 
methods/gears 

Fishing  methods/gears  that  require  additional  effort  in  the  fishing 
process, such as trawls. 

Baltic  Sea  fishing 
squares 

A grid  of Baltic Sea fishing  squares  was  created  by  NMFRI  in  the  early 
1960s  for location and statistical  reasons.  This grid comprises parallels 
spaced at 10 geographic minutes and meridians spaced at 20 geographic 
minutes, forming standardized  "squares" with  dimensions of 10 x 11.5 
nautical miles (nm). These squares are designated from west to east with 
alphabetical letters (A through Z) and from south to north with numerical 
values (1 through 31) 

Bornholm Deep 

The Baltic Deep (105 m) is located on the eastern side of the Bornholm 
Island, which is an important breeding ground for cod. 

Cultural fishery 

Commercial fishery based on the use of traditional gear, equipment and 
fishing techniques, which is related to the tradition of the region, building 
the social and cultural identity of the region and its unique image. Fishers 
can  participate  in  cultural  fishing  in  a  given  National  Park  if  they  are 
included in the list of authorized entities. They have to apply to be on this 
list. The criteria of entry on the list includes vessels up to 12 meters in 
length,  fishing  with  passive  gear  from  ports  around  the  areas  of  a 
particular National Park.  

Passive gears 

Fishing gears that do not require additional effort in the fishing process, 
such as entangling nets and traps. 

Plan of protective 
tasks 

Protection Plan 

The basic document regulating protective tasks for conservation zones in 
Poland  (including  MPAs,  Natura  2000).  The  plan  is  implemented  by 
ordinance of the regional director of environmental protection and has to 
be updated at least every 10 years. The plan of protective tasks can be 
considered  as  an  equivalent  for  a  management  plan.  Until  the  end  of 
2022, none of the management plans (i.e. plan of protective tasks) have 
been approved (Marchowski et al, 2022). 

The  document  regulating  the  protective  tasks  for  National  Parks  in 
Poland, mandatory for marine areas. It is implemented by regulation of 
the  Ministry  of  Environment  and  has  to  be  updated  at  least  every  20 
years. The plan has a scientific basis. Note that the MPAs are only a part 
of the protected areas in Słowiński National Park and Woliński National 
Park  

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3.  CASE STUDY REPORT: 

TVEDESTRAND MARINE PROTECTED AREA 

NORWAY – SKAGERRAK 

European lobster Homarus Gammarus. © 
Havforskningsinstituttet 

Analysis of potential spillover effects around the 
Tvedestrand Marine Protected Area  

Portia Joy Nillos Kleiven & Alf Ring Kleiven  

Institute for Marine Research - Norway 

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TABLE OF CONTENTS 

1 
2 
3 
4 

5 
6 
7 
8 

EXECUTIVE SUMMARY ........................................................................................... 41 
BACKGROUND ...................................................................................................... 41 
AIMS AND OBJECTIVES ......................................................................................... 43 
METHODOLOGY .................................................................................................... 44 
4.1  Data collection ............................................................................................ 44 
4.2  Study design .............................................................................................. 45 
4.3  Data analysis .............................................................................................. 45 
4.4  Method for evaluation of spillover assessment ................................................. 46 
4.5  Qualitative approach .................................................................................... 47 
RESULTS ............................................................................................................. 47 
DISCUSSION ....................................................................................................... 50 
CONCLUSIONS ..................................................................................................... 51 
REFERENCES ....................................................................................................... 52 

LIST OF ABBREVIATIONS 

Term 

Description 

ACF 

BACI 

CPUE 

GAM 

MPA 

SD 

Auto-correlation function  

Before-after control-impact  

Catch per unit effort (number of lobsters per trap-day) 

Generalized additive model 

Marine protected area 

Standard deviation 

UTM  

Universal Transverse Mercator 

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1  EXECUTIVE SUMMARY  

Spillover can be inferred with an increased abundance of target species right outside the boundary 
of a marine protected area (MPA) compared to fished areas further out. In this  case study, we 
present evidence of spillover happening within 200 m from the boundaries of a small lobster MPA 
in  Tvedestrand,  located  in  the  Skagerrak  region  of  southern  Norway.  Since  2010,  catch 
monitoring, with the use of a randomized sampling, using a before-after control-impact (BACI) 
design  has  produced  a  12-year  time  series  data  on  Catch  Per  Unit  of  Effort  (CPUE)  and  total 
lengths  for  the  European  lobster  Homarus  gammarus.  Results  that  are  presented  in  this  case 
study  extend  the  work  that  was  published  by  Nillos-Kleiven  et  al  (2019),  with  the  same 
generalized additive model analysis done on the extended data set until 2021. 

Results show that CPUE inside the MPA has gradually increased over time and is currently at 1.47 
lobsters per trap-day, more than 2 times higher than compared to fished areas (0.63 lobsters per 
trap-day), 9 years after the MPA was established. Within 200 m of the borders, CPUE is higher in 
2021  compared  to  before  establishment  and  implementation.  At  1,000  m  from  the  boundary, 
CPUE remains at a stable lower level, most probably due to the increased fishing pressure from 
local fishers in this area. A similar but more pronounced non-linear response of high abundance 
in the centre of the MPA, followed by a dip in the border and a plateau in fished areas further 
away was also detected in 2021 compared to results from 2016. 

Data  from  interviews  with  local  fishers  indicate  that  many  have  moved  their  preferred  fishing 
spots  closer  to  the  boundaries  because  they  have  experienced  better  (stable)  catches  there.   
Despite lower lobster abundance near the border, higher abundances further away in the fished 
area indicate that after close to a decade of protection, the fisheries seem to be finally benefitting 
from the nearby MPA. 

The  total  lengths  of  caught  lobsters  are  20%  larger  inside  the  MPA  compared  to  fished  areas 
outside. Furthermore, a shift towards higher numbers of larger individuals is visible in the length 
distribution for catches inside the MPA.  

On the other hand, the  increase in  the abundance and size of lobsters in and around the MPA 
cannot  be  attributed  to  protection  alone,  as  it  is  only  one  of  the  tools  in  the  expanding 
conservation toolkit for lobster populations in Norway. Also, there are not sufficient data on fishing 
pressure to support a conclusion that the increased fishing pressure may have caused erosion of 
the spillover gradient that should have been observed in this area.  

The main scientific recommendations from this case study are the following: (i) To continue the 
monitoring series for CPUE for several years more, as European lobsters have a relatively long 
lifespan; (ii) To collect data on fishing pressure by conducting fishing gear survey during the open 
season in the next years; and (iii) To increase the duration of the annual sampling period. 

To conclude, this study demonstrates that protection for severely targeted species works, but it 
takes a long period of time to be perceived in the fisheries. The dynamics of spillover and fisheries 
around MPA borders, as well as the interaction of protection time with other fishery management 
tools, are topics that should be investigated in more detail and in many other areas as these are 
important in developing sustainable fisheries and conservation of marine resources. 

2  BACKGROUND 

The Tvedestrand Marine Protected Area (MPA) (9°8′0″ E, 58°36′30″ N) is a 4.9 km2 no-take zone 
for lobsters, located in the outer skerries of Tvedestrand municipality in the Norwegian Skagerrak 
region (Figure 1). The MPA is situated in an area generally classified as rocky substrate, originating 
from a glacial moraine that is running parallel to the coastline. Only hook and line fishing gear is 
allowed inside this MPA,  and  the use  of  sedentary fishing gear and all other methods that  can 
potentially catch lobsters are prohibited. The outermost border, with a depth of 60 m, is adjacent 
to  the  rim  of  the  Norwegian  Trench  which  forms  a  natural  deep-water  barrier  for  lobster 
movement. 

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Figure 1: Detailed map of the Tvedestrand coast showing the MPA (box with solid line), 
and  the  study  area  (dashed  line).  Grey  lines  indicate  depth  contours.  Inset:  map  of 
northern Europe indicating approximate location of the study area (red star). 

The MPA, due to its location, was part of the preferred fishing grounds for local fishers. The MPA 
was established in 2012 after a long process that was initiated by the local government with help 
from government agencies and with strong support from the Institute of Marine Research station 
in  nearby  Flødevigen.  Stakeholder  consultation  was  conducted,  and  while  the  majority  was  in 
favour of the establishment of an MPA, a group of local fishers was also vehemently against. The 
fishers  reasoned that  there  were  already  enough  restrictions  to  lobster  fishing  in  Norway,  and 
that taking away part of the fishing grounds their grandfathers had always utilized is a violation 
of their constitutional rights to access their local natural resources. A more detailed narrative of 
the process is documented in Knutsen et al (2022). 

In June 2012, a 5-year plan was adopted by the municipality of Tvedestrand with the provision 
that  if  the  MPA  proves  to  be  effective,  it  can  continue  based  on  an  agreed  extension 
(Fiskeridirektoratet,  2023).  In  2017,  a  hearing  was  conducted  on  the  extension  of  the  MPA 
ordinance,  and  its  status  as  a  protected  area  for  another  10  years  was  acknowledged  by  the 
Norwegian Ministry of Fisheries. The ministry’s decision was based, among other things, on the 
value  of  scientific  data  on  spatial  protection  that  was  (and  is  being)  collected  as  well  as  the 
ecological  value  of  the  area  for  the  local  struggling  cod  (Gadus  morhua)  population.  Although 
several individuals from the local commercial fishery sector were vocally against the extension of 
the MPA ordinance, it was eventually approved. The documents on the hearing, statements from 
the stakeholders, as well as the decision of the national government on the continued protection 
of  the  Tvedestrand  lobster  MPA  can  be  accessed  at  the  Fiskeridirektoraret’s  website  (only  in 
Norwegian).  

The MPA is also part of the larger Raet National Park. The park has zonation and regulations, but 
the implementation is generally non-existent (Fjeld, 2021). However, it must be mentioned that 
the local population and majority of recreational fishers who utilize the area are generally aware 
of the boundaries of the MPA, and generally abide by the rules and regulations.  

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The Tvedestrand MPA is in many ways unique because the push for its establishment came from 
scientists  and  local  stakeholders  in  a  municipality  that  are  passionate  about  conservation  of 
marine  resources.  In  Norway,  where  the  fisheries  regulation  is usually  done  using  a  top-down 
approach, this bottom-up approach was rarely heard of. The result is that the implementation of 
the  local  ordinance  (spatial  protection)  is  supported  greatly  by  national  regulations  (temporal 
closures, legal size limits, etc.) that result in a good “toolbox” for lobster conservation. 

Lobster  fishing  in  Norway,  at  present,  is  generally  considered  to  be  a  recreational  activity, 
although there are a few fishers that sell their catch. The fishery used to be an important economic 
resource in southern Norway, but catches have been steadily plummeting since WWII and never 
really recovered. Populations of European lobster were so severely reduced that the species ended 
up  in  the  IUCN  Red  List  for  a  period  of  time.  Therefore,  several  steps  were  taken  by  the 
government in the last 2 decades to mitigate the decline, and with the hope of improving current 
numbers (Kleiven et al., 2012). 

Aside from the locally established no-take areas, lobster fishing is also regulated by many other 
rules that are implemented nationally. Recreational fishing is only allowed between October 1-30 
and  otherwise  closed  for  the  rest  of  the  year.  There  is  also  a  minimum  and  maximum  size 
restriction in the Skagerrak area. The minimum size was increased from 24 to 25 cm, and since 
2017, lobsters over 32 cm in total length cannot be harvested. All roe-bearing lobsters have been 
protected from harvest since 2008. Recreational fishers are allowed to have a maximum of 10 
lobster pots per person per boat throughout the open season. Traps have to be marked with the 
fisher’s name and address. In recent years, the Ministry of Fisheries imposed the registration of 
all recreational fishers prior to the start of the fishing season, as well as the use of an escape vent 
sewed shut with cotton thread that can degrade and prevent “ghost fishing” in the sea bottom if 
the trap is lost during fishing (Fiskeridirektoratet, Lobster fishing).  

The Skagerrak region in Norway has a long history of trawling.  Fisheries for cod used to be an 
important economic resource in the region, but this has continually declined over the years, and 
is currently considered non-profitable. A handful of shrimp trawlers still operate in the area, but 
it is a very small fraction of this previously existing lucrative fishing industry. In and around the 
MPA, the majority of fishers is recreational fishers with small boats, mostly older men who have 
fishing  as  a  life-long  hobby.  The  most  popular  target  species  are,  for  example,  cod,  pollack, 
lobsters, crabs. The “high season” for these recreational fishers is therefore during the summer 
and autumn holiday periods, the latter often coinciding with the open season for lobster fishing.  

3  AIMS AND OBJECTIVES 

The objective of this case study is to look into whether or not spillover is happening at the borders 
of the Tvedestrand MPA, 9 years after it was established. The answer is of great interest not only 
for scientists but also for the local government of Tvedestrand, since continued implementation 
of the MPA is dependent on whether the “experiment” has worked or not.  

For this study, we looked at the development over time of the CPUE for lobsters relative to the 
boundary of the MPA. This study builds on an on-going before-and after-impact (BACI) monitoring 
that was conducted between 2010-2016, and published in 2019 (Nillos-Kleiven et al., 2019). New 
to  this  study  are  data  from  2017,  2019  and  2021,  which  were  incorporated  into  the  same 
statistical model used for the earlier study. 

The dataset for this analysis contains 3 years of data prior to MPA establishment, and 10 years of 
data from monitoring afterwards. And although monitoring after establishment has not been done 
on an annual basis due to personnel and budget constraints, the sampling method and time of 
year for sampling has remained the same. Also, by using the same statistical analysis, we expect 
to get a good picture of the temporal and spatial patterns of lobster abundance a decade after 
the MPA was established.   

We  hypothesised  that  the  key  factors  that  potentially  influence  spillover  dynamics  in  the 
Tvedestrand MPA are the location of the MPA, development/increase of the recreational fishing 
pressure at the border areas, the implementation of other regulations and restrictions on lobster 
fishing over time.  

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4  METHODOLOGY 

4.1  Data collection 

Data from the study area have been collected with the use of lobster traps for experimental fishing 
in randomly determined points. Since 2010, the same two-chambered lobster traps (90 × 45 × 
40 cm) with 11.5 cm entrance diameter and closed escape vents have been used. These traps 
are  commonly  known  as  Scottish  lobster  traps  (Figure  2).  Sampling  is  conducted  at  the  same 
period every year (last week of August to first week of September), a month before the start of 
the lobster fishing season in Norway. Sampling effort (Table 1) was doubled in 2016 to obtain 
better-quality data for statistical analyses. Trap locations inside and around the MPA were selected 
at random during the pilot survey (2010). From 2011 onwards, the sampling regime was modified 
slightly using topography data to maximize sampling efficiency while still maintaining randomized 
trap locations (random stratification). Sampling was thus limited to only those areas that 1) have 
a rocky bottom; 2) have a slope between 5 and 20° and a maximum depth of 35 m from the MPA 
surface; and 3) are situated inside the study area (within 3 km northeast and southwest of the 
borders). 

The traps are baited with frozen mackerel (Scomber scombrus) before deployment and attached 
to  a  marker  buoy  with  a  40–45  m  length  rope.  Marker  buoys  for  each  trap  are  individually 
numbered and carried information about the experimental fishing activity. Time, GPS position and 
depth are recorded for each trap haul. All lobsters caught are released at their capture location. 

Figure 2: Lobster trap used for this study. Note that the escape vents are mandated to 
be open by law, but these are sewn shut (with special dispensation) for the purpose of 
this study. (Photo credit: Online catalogue of jula.no).   

Table 1. Sampling effort: total number of traps deployed in the study area (2010-2021). 

Year 

2010  2011  2012  2013  2014  2015  2016  2017  2019  2021 

Fished area 
MPA 
Total 

110 
17 
127 

104 
39 
143 

127 
60 
187 

89 
55 
144 

203 
139 
342 

191 
88 
279 

352 
183 
535 

71 
120 
191 

67 
128 
195 

96 
171 
267 

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4.2  Study design 

This case study employed a BACI design with random sampling in and around the MPA with the 
use of Scottish lobster traps over time to determine the catch per unit effort for lobsters (as a 
proxy  for  abundance).  The  study  area,  with  an  area  of  52.4  km2,  is  indicated  in  Figure  1.  It 
encompasses  fishing  grounds  within  3  kilometres  from  the  side  boundaries  of  the  MPA.  The 
boundary towards the open sea was not included because it is a deep-water area that forms a 
natural boundary for lobster movement. Lobster abundance was the metric selected, because it 
is easily replicable and is well-suited for field work with small boat with a crew of 2-3 people and 
standard fishing equipment. As we are using the same traps as the local fishers, it gives us results 
that are easy to interpret and allow for easier dissemination to the stakeholders (e.g. “A catch of 
1 lobster per trap in 2 days is the norm in this area”). Thus, we have a common metric to discuss, 
and catch over the years (as well as indications of spillover) can be easily monitored by the locals 
as well.  

As to the duration of the study, the BACI design has been implemented from the start, thus we 
have 3 years of “before” data in the area that was eventually designated as an MPA. Monitoring 
of  this  area  has  been  ongoing  11  years  after  implementation,  and  we  hope  to  continue  this 
monitoring for a decade or more. The Tvedestrand MPA is one of the few MPAs in Norway that 
have been established with the purpose of scientific monitoring, and as its location and the data 
we have – and will be – generating from it is of great importance in understanding the mechanisms 
of spillover. 

The study area has a similar habitat inside and outside the MPA, so it is expected that habitat 
selection for lobsters will be evenly distributed. We also assumed the same catchability for the 
traps that are deployed inside and outside the MPA. The only difference is the (assumed) absence 
of fishing pressure inside the MPA, which over time should result in an abundance gradient that 
is highest in the middle of the MPA and with a steeply declining gradient towards the border and 
outwards to the fished areas. The fishing pressure was also assumed to eventually increase closer 
to the border over time  due  to  fishers’  expectations  of bigger and more catch in fishing areas 
adjacent to the MPA border. 

Since we covered a relatively small area for this case study, and have randomly placed sampling 
points collected over the same period time every year, it was feasible for us to detect eventual 
changes in abundance. The availability of precise GPS units as well as spatial analysis tools in R 
allowed us to ask if there is a gradient in and around the border, and how steep that gradient is.  
This is one approach in determining spillover. 

4.3  Data analysis 

For this study, we adopted the use of CPUE as a proxy for abundance, and the aim was to detect 
any  change  in  the  abundance  in  and  around  the  MPA  border  over  time,  which  is  expected  to 
develop a steeper gradient if spillover is happening.  

The following section on data analysis for CPUE is taken from Nillos-Kleiven, et al. (2019). 

To achieve parsimony in the analysis of CPUE, a zero-inflated Poisson generalized additive model 
(GAM) of the main factors (distance from border and years of protection) that influence CPUE was 
used. Depth was added as a random factor. The optimal model determined by backwards step 
Akaike selection criterion is as follows: 

Chij=s1(Bh,Pi) +s2(Dj)+ βk +εijk. 

Here, the model predicted CPUE (C) for a trap at distance h and year i at depth j is given by the 
interaction between the distance from the border (Bh) and years of protection (Pi) as well as the 
depth of trap from the surface (Dj). The splines (s1 and s2) are the smoothing functions modelled 
as  a  product  of  quadratically  penalized  regression  spline  basis  functions  of  B,  P  and  D  with 
software-determined  automatic  smoothness  estimation. βk is  the  model  intercept  and ɛijk is  the 
error term (see electronic supplementary material, S1 for intercept values and GAM output). The 
fitted values for CPUE (at model predicted optimal depth) were obtained by using the formula: 

CPUE=log(Chij). 

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The locations of traps (longitude and latitude) were converted into  metric Universal Transverse 
Mercator (UTM) units for use in data analyses and mapping in R. Spatial and temporal correlation 
was checked using auto-correlation tests (ACF), to confirm that the data were neither spatially 
nor temporally correlated before proceeding with the analysis. The distance from the border for 
each trap was calculated as the shortest distance to the nearest MPA border. To aid interpretation, 
the border line was designated as 0. Distance from the border was negative inside the MPA and 
positive outside the MPA. 

Data preparation and analyses, as well as generation of figures and maps were done primarily in 
the  R  environment  for  statistical  computing  (http://www.r-project.org)  using  the  following 
packages: mgcv, pscl, splancs, rgeos and sp.  

Validation  for  the  optimal  model  is  done  by  using  the  Pearson  residual  and  the  inspection  of 
residual plots for the zero-inflated models. 

4.4  Method for evaluation of spillover assessment 

Our current method of experimental fishing in random sites throughout the study site is suitable 
for assessing spillover effects because it is easy and practical to execute in the field, as well as 
easily replicable. In terms of reliability, it is difficult to say, because the dataset is zero-inflated, 
with  up  to  60%  empty  traps  on  certain  days,  and  therefore  a  large  number  of  traps  must  be 
deployed. This zero-inflation reflects the many factors that affect catchability of lobsters, mainly 
patchiness  of  the  habitat,  presence  of  a  large  number  of  crabs,  as  well  as  weather  and  sea 
conditions. We do our best to ensure that the traps fall within a set range of conditions, but it has 
happened that these traps ended up in muddy patches, which lobsters are known to avoid. Also, 
it is not uncommon to pull up a trap full of crabs, and the question then is are there lobsters that 
could have gone in if the traps were not full of crabs. However, despite of these drawbacks, it is 
with a certain amount of confidence that we could say that spillover  can be detected if it does 
occur in the MPA because sampling has been done in the same way over a relatively long period 
of time in the same  study area. An  increase  in both  abundance  and lobster size at the border 
areas compared to areas further away that are heavily fished can be considered as evidence of 
spillover.   

Of course, no method is foolproof. Increased size and abundance of lobsters in the border area is 
bound to attract higher fishing pressure, and we have seen this trend in our data set from 2012-
2016. Spillover in the border area, if it does occur, will thus be harder to detect because of the 
greater  loss  to  fisheries.  Although  we  have  no  data  on  fishing  pressure  from  2017  onwards, 
interviews with recreational fishers who use the border areas confirm that this shift is happening 
even more as they experience improving catches near the border over time. Recreational fishers 
have  reported  stable  yields,  or  slight  increases  in  yields  in  the  border  areas  despite  the 
documented  lower  CPUE  there.  This  is  because  they  are  not  allowed  to  take  home  the  larger 
individuals (more than 32 cm) as well as those that are smaller than the 25 cm minimum legal 
size that they catch. Fishers are reporting that they have to throw back more than half of their 
catches due to the legal restrictions (but they do so without complaining, because they are aware 
that the restrictions are in place to ensure stable yields in the coming years). 

Our  study  is  limited  in  that  we  have  no  means  to  monitor  the  actual  fishing  pressure  that  is 
happening at the MPA borders. We are aware that this fishing pressure peaks during a first two 
weeks of the open season, but the number of fishers can vary according to whether it is autumn 
break  and  on  weather  and  sea  conditions.  Also,  the  MPA  in  Tvedestrand  is  not  monitored  by 
enforcement agencies, and poaching is happening at a chronic low level and “everybody knows 
it”.  Fishers also catch lobsters that were tagged inside the MPA in the fished areas outside, but 
these are often unreported, and the numbers are too few to run a proper mark-recapture analysis 
to demonstrate spillover movement.   

In an ideal world with unlimited budget and personnel, and the same ideal climate for fieldwork 
throughout the year, the same sampling procedure should be done both a month before and after 
the open season to determine if lobster movement to outside areas are occurring, and if there is 
a notable decrease in the CPUE after the open season. Sampling using the same experimental 
fishing method should also be done yearly, and the fishing pressure around the MPA should be 
quantified properly by doing a gear survey throughout the open season. A longer sampling period 
is also desirable. 

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4.5  Qualitative approach 

In  order  to  fill  in  some  knowledge  gaps  on  the  perception  of  the  local  stakeholders  on  the 
occurrence of spillover, 4 interviews were conducted with local fishers who have been fishing in 
the  area  long  before  the  MPA  was  established  in  2012.  The  local  resource  manager  of  the 
municipality was unavailable for personal reasons. The interviewees were selected from a short 
list of known local lobster fishers, and they were interviewed using the standard questionnaire 
that was developed for this study (Annex 4).   

5  RESULTS 

Lobsters became bigger in the MPA immediately after protection, and more of them are 
growing bigger over time under protection. 

The mean total lengths of lobsters caught in traps deployed in the  MPA are significantly longer 
compared to those that were caught in fished areas outside the border, after 11 years of protection 
(see Figure 3). Prior to protection, the difference in the lengths of lobsters caught between these 
areas was relatively smaller. The results of length monitoring, although not a direct indication of 
spillover, clearly show that protection has a direct effect on the sizes of individuals.  Interestingly, 
for 2021, the mean total length of lobsters caught outside the MPA is at 25.4 cm, which is just 
above the legal-size limit. Inside the MPA, mean total length is at 30.8 cm, which represents a 
21% increase in length. These results also  reaffirm the stories of local recreational fishers that 
many of lobsters caught just outside the MPA are now “safe from fishing” as they are nearing the 
32 cm maximum legal catch size.  

Figure 3: Total length of lobsters caught inside (black circles) compared to fished areas 
(boxes).    Error  bars  are  +/-  1  SD.  The  dotted  vertical  line  indicates when  protection 
was implemented.   

Another way to look at the data for total lengths is to look at the histograms for length distribution 
based on area and implementation of protection.  Figure 4 indicates that while the control area 
has a similar length distribution before and after protection status, the length distribution in the 
MPA area has shifted, with more individuals in the 30-cm-and-longer group. In this graph, one 
can easily see in the “after protection” side that there are more of the larger lobsters in the MPA 
compared to the fished area.   

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Figure  4:  Length  distributions  for  before  and  after  protection  in  fished  (control)  and 
protected (MPA) areas.  Data are pooled for the entire study period (2010-2021).  

In general, the CPUE (number of lobsters caught per trap-day) in fished areas outside the MPA is 
low and has remained at the same level as prior to MPA implementation. CPUE inside the  MPA, 
however, has gradually increased over time (see Figure 5) and is currently at 1.47 lobsters per 
trap-day, more than two times higher than compared to fished areas (0.63 lobsters per trap-day) 
9 years after protection started.  

Figure  5:  Trend  over  time  for  catch  per  unit  effort  (number  of  lobsters  per  trap-day) 
from 2010-2021 inside the protected area (dark circles) compared to the fished areas 
(triangles in a box) in the Tvedestrand lobster MPA.  Error bars are +/- 1 S.D. The dotted 
vertical line indicates when protection was implemented.   

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Predicted values from the GAM has indicated a very clear response to CPUE to protection over 
time (Figure 6). The values are predicted by the model at the optimal depth of 25 m. The gradient 
inside the MPA has been increasing, and after 9 years of protection, a much higher CPUE at fished 
areas up to 200 m from the border is visible, an indication of spillover. Another interesting finding 
is the even more pronounced “dip” in CPUE in the fished area within 1 km of the boundary. This 
area  corresponds  to  the  same  area  that  the  fishers  we  interviewed  referred  to,  where  they 
indicated that they had stable catch since the establishment of the MPA. 

Figure 6: Model predicted CPUE response to years of protection and distance to border 
(bold  lines),  prior  to,  4  years  and  9  years  after  MPA  implementation,  at  the  optimal 
depth of 25 m. Thinner lines of the same colour indicate +/- 1 S.E.  Vertical dotted line 
indicates the MPA boundary.   

Results from the  GAM  on the interaction  of trap  distance  from  border  and  length of protection 
show a non-linear CPUE response, with catches being higher inside the MPA compared to fished 
areas outside (Figure 7). The general shape of these splines are similar, indicating the  gradual 
but positive response of abundance to protection over time in areas within the border of the MPA.   

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A 

C 

E 

G 

B 

D 

F 

H 

Figure 7:  Splines showing the effect of the interaction of trap distance from the MPA 
border and length of protection to catch per unit effort, derived from GAM. A) Prior to 
protection; B) 1 year of protection; C) 2 years of protection; D) 3 years of protection; 
E)  4  years of  protection;  F)  5  years of  protection;  G)  7 years of  protection;  and  H)  9 
years of protection. X-axis numbers indicates distance to border, with negative values 
on the left side of the graph indicating distance inside the MPA. Dotted non-linear lines 
are 95% confidence intervals. Y-axis indicates the partial effect of the time protection 
variable, from 0 year to 9 years.    

6  DISCUSSION 

Compared  to  values  prior  to  protection,  the  CPUE  gradient  9  years  after  MPA 
implementation  indicate  that  the  catch  within  200  m  of  the  boundary  increased. 
Together with higher catches further away from the preferred fishing area at 1000 m 
from  the  boundary,  these  values  suggest  that  spillover  is  happening.  If  the  fishing 
pressure  in  the  1  km  area  outside  the  border  has  maintained  the  same  level  as  previously 
published in 2017, the fact that the abundance here has not been lower at present indicates that 
the MPA has had a positive effect on the nearby fished areas. The presence of  slightly higher 
catches  further  away  (at  around  1500  m)  9  years  after  implementation  compared  to 
values  from  4  years  after  implementation  —  and  despite  the  much  higher  expected  fishing 
pressure — are also a clear indication that protection benefits (spillover of adult individuals) are 
being felt in the fished areas.  

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The  results  of  this  extended  analysis  are  similar  to  the  findings  of  Goñi  et  al.  (2006)  on  the 
spillover of the spiny lobster Palinurus elephas, where decreased CPUE values were also attributed 
to the fishing pressure outside the MPA. A similar pattern for abundance (a decline right by the 
border followed by a plateau) was reported.  

On  the  other  hand,  while  results  of  a  few  studies  attribute  the  abrupt  decline  in  CPUE  by  the 
border to increased fishing pressure in the area, our lack of current data on fishing pressure 
in  Tvedestrand  weakens  our  argument  for  the  negative  effect  of  “fishing  the  line” 
(Kellner,  2007)  on  lobster  abundance  in  this  area.  However,  since  we  documented  that 
catches in this area were higher prior to MPA establishment, the currently lower level in this area 
outside  the  border  is  probably  attributable  to  sustained  higher  fishing  pressure  here.  Local 
fishers interviewed for this study have mentioned that they had to “move” their fishing 
areas out of the MPA when it was implemented, and it is likely that they moved to the 
closest available fishing ground just outside the border.  

The  results  obtained  from  this  case  study  highlight  the  need  for  improved  data  quality  in  the 
coming  years,  so  that  the  factors  that  influence  the  steepness  of  abundance  gradients  can  be 
examined  further.  Modelling  with  GAM  requires  good  quality  data.  It  is  hoped  that  eventually, 
with enough fishing gear survey data, we will be able to incorporate fishing pressure data into our 
existing statistical model, and possibly provide interesting insights into the dynamics at the MPA 
border.   

7  CONCLUSIONS 

This  study  shows  that  long  term  monitoring  with  a  good  design  can  detect  the  occurrence  of 
spillover for long-lived species like the European lobster.  Over time, an abundance gradient builds 
up  inside  the protected  area,  and  this builds up  expectations  as  well  for  eager  lobster  fishers. 
Increased fishing pressure at the boundaries is therefore expected, and this unfortunately erodes 
the  spillover  effect,  making  it  more  difficult  to  detect  earlier.  However,  with  longer  protection 
time, clearer abundance gradients develop, and positive effects to nearby fishing grounds happen 
eventually. In this study, we have shown that 9 years is sufficient to detect spillover at the border 
area of an MPA, despite the assumed increasing fishing pressure in adjacent fished areas.   

On the other hand, the increase in the abundance and sizes of lobsters in and around the MPA 
cannot  be  attributed  to  protection  alone,  as  it  is  only  one  of  the  tools  in  the  expanding 
conservation toolkit for lobster populations in Norway. Also, there are not sufficient data on fishing 
pressure to support a conclusion that the increased fishing pressure may have caused erosion of 
the spillover gradient that should have been observed in this area. 

This study is an extension of the work that has been published by  Nillos-Kleiven et al. in 2019. 
The BACI time series, using a relatively simple method for experimental fishing, will hopefully be 
continued for many more years to come, as it sheds light on the dynamics between spillover and 
fishing pressure in the boundaries of a relatively small  MPA. Lobsters, with their longevity and 
appeal to fishers, are in many ways the ideal species to monitor in the span or a decade or two. 
The  dynamics  of  spillover  and  fisheries  around  MPA  borders  is  an  important  mechanism  for 
sustainability and conservation  that should be  investigated further and in more detail in many 
other areas as well around the world.  

To conclude, this study demonstrates that protection for severely targeted species work, but it 
takes  a  long  period  of  time  to  be  felt  in  the  fisheries.  The  dynamics  of  spillover  and  fisheries 
around MPA borders, as well as the interaction of protection time with other fishery management 
tools are topics that should be investigated further and in more detail in many other areas as well 
as these are important in developing sustainable fisheries and conservation of marine resources. 

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8  REFERENCES 

Fiskeridirektoratet (Aug. 2023). https://www.fiskeridir.no/Yrkesfiske/Havmiljoe/Bevaringsomraader. 

Fiskeridirektoratet, Tvedestrand documents (Aug. 2023). https://www.fiskeridir.no/Areal-og-

miljo/Dokumenter/Hoeringer/Forlengelse-av-forskrift-om-bevaringssoner-i-Tvedestrand-kommunes-
sjoeomraader. 

Fiskeridirektoratet, Lobster fishing (Aug. 2023) (https://www.fiskeridir.no/Fritidsfiske/Artar/Hummarfiske) 

Fjeld,  I.E.  (2021,  April  14).  Norge  sier  havet  er  vernet,  samttidig  pågår  det  utbredt  fiske.  NRK 

https://www.nrk.no/norge/norge-sier-havet-er-vernet-_-samtidig-pagar-det-utbredt-fiske-1.15442211. 

Goñi R, Quetglas A, Reñones O. (2006). Spillover of spiny lobsters Palinurus elephas from a marine reserve 

to an adjoining fishery. Mar. Ecol. Prog. Ser. 308, 207-219. 

Kellner  JB,  Tetreault  I,  Gaines  SD,  Nisbet  RM. (2007). Fishing  the  line  near  marine  reserves  in  single  and 

multispecies fisheries. Ecol. Appl. 17, 1039-1054. 

Kleiven, A. R., Olsen, E. M., & Vølstad, J. H. (2012). Total catch of a red-listed marine species is an order of 

magnitude higher than official data. PLoS One, 7(2), e31216. 

Knutsen, J. A., Kleiven, A. R., Olsen, E. M., Knutsen, H., Espeland, S. H., Sørdalen, T. K., ...  & Moland, E. 
(2022).  Lobster  reserves  as  a  management  tool  in  coastal  waters:  Two  decades  of  experience  in 
Norway. Marine Policy, 136, 104908. 

Nillos Kleiven, P. J., Espeland, S. H., Olsen, E. M., Abesamis, R. A., Moland, E., & Kleiven, A. R. (2019). Fishing 
pressure impacts the abundance gradient of European lobsters across the borders of a newly established 
marine protected area. Proceedings of the Royal Society B, 286(1894), 20182455. 

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4.  CASE STUDY REPORT: 

THE NORTH SEA COASTAL ZONE 

THE NETHERLANDS – NORTH SEA 

Grey shrimp (Crangon crangon) 

Analysis of potential spillover effects: Shrimp 
fisheries in the North Sea Coastal Zone  

Tamara Vallina 
Wageningen Marine Research, Wageningen University and Research 

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TABLE OF CONTENTS 

1 
2 

3 
4 

5 

EXECUTIVE SUMMARY ........................................................................................... 55 
BACKGROUND ...................................................................................................... 55 
The grey shrimp in the North Sea Coastal Zone ............................................... 55 
2.1 
2.2 
The potential spillover effects ....................................................................... 57 
AIMS AND OBJECTIVES ......................................................................................... 58 
METHODOLOGY .................................................................................................... 58 
4.1  Qualitative approach .................................................................................... 58 
4.2  Quantitative approach .................................................................................. 58 
The data .................................................................................................... 58 
4.3 
The study area and MPAs ............................................................................. 58 
VMS and logbook data ................................................................................. 59 
Data processing .......................................................................................... 59 
4.4  Statistical analysis ....................................................................................... 59 
Changes in fishing effort and catches before and after MPA establishment .......... 59 
Increasing biomass since establishment of MPA ............................................... 60 
Software  .................................................................................................... 60 
RESULTS ............................................................................................................. 60 
5.1  Qualitative approach: key findings of the questionnaire .................................... 60 
5.2  Quantitative approach: changes in fishing effort, catch and CPUE ...................... 61 
Increasing biomass since establishment of MPAs, and closer to the border of 

the MPAs? ..................................................................................... 62 
DISCUSSION ....................................................................................................... 63 
6 
CONCLUSIONS ..................................................................................................... 64 
7 
8 
REFERENCES ....................................................................................................... 64 
APPENDIX ................................................................................................................... 66 

LIST OF ABBREVIATIONS 

Term 

Description 

AIC 

AIS 

BACI 

CPUE 

CSH 

Akaike information criterion 

Automatic Identification System 

Before-After Control-Impact 

Catch per unit of effort 

Grey shrimp 

GLMM 

Generalized linear mixed model 

LNV 

MPA 

NSCZ 

VMS 

Ministry of agriculture, nature, and food quality  

Marine protected area  

North Sea Coastal Zone 

Vessel monitoring system 

VIBEG 

Visserij in beschermde gebieden akkoord (NL) / Fisheries in protected areas agreement (EN) 

WWF 

World Wide Fund for Nature 

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1  EXECUTIVE SUMMARY  

The grey shrimp (Crangon crangon) fishery is one of the largest fisheries in the coastal zones of 
the Netherlands. The majority of the shrimp landed at the auctions in the Netherlands comes from 
the North Sea Coastal Zone (NSCZ). The NSCZ is a valuable area which is designated for several 
habitat  types  and  many  animal  species.  To  enable  a  combination  of  nature  conservation  and 
fisheries within the Natura 2000 areas in the North Sea, the Fisheries Protected Areas Agreement 
(VIBEG) was concluded. Four small areas, in total approximately 144 km2 were completely closed 
for bottom-disturbing fisheries, including shrimp fisheries. 

Studying  spillover  effects  holds  key  insights  into  marine  protected  areas  (MPAs)  and  their 
ecological  impact.  It  can  give  true  insight  in  the  consequences  for  the  shrimpers  previously 
operating  in  the  area  and  quantify  any  potential  benefits.  Interviews  were  conducted  via 
questionnaires with stakeholders of the NSCZ, aiming to explore their insights, expectations, and 
their experiences regarding spillover in the region. Then, basic fishery statistics were assessed 
and generalized linear mixed models (GLM) were constructed to assess biomass (in cumulative 
kilograms), fishing effort (in cumulative hours), or mean catch per unit effort (CPUE) (kilograms 
per hour) per 0.05-degree c-square annually and tested to period (before or after the fisheries 
adherence to the MPAs' restrictions).  

It  was  observed  that  shrimping  effort  significantly  decreased  within  the  NSCZ  after  the 
establishment  of  the  MPAs.  However,  the  quantity  of  shrimp  caught  did  not  show  significant 
differences before and after the establishment of MPAs. Aligning with previous findings, CPUE did 
increase significantly. The increase in CPUE does not testify for a relative increase in biomass. As 
many fishers agreed with a buy-out proposal when the protected areas were established, fishing 
effort significantly decreased. As a consequence, there was much less competition, which could 
be an explanation for the increase in CPUE.  

The indicators of potential spillover of shrimp in the four MPAs within the NSCZ were tested. In 
theory,  perfect  density-related  spillover  would  exhibit  a  gradient  of  biomass  or  abundance 
originating at the boundaries of the MPAs, diminishing as distance from the boundary increases, 
and growing stronger over time. The analysis found no significant effects related to distance to 
the nearest MPA, years since MPA establishment, or the interaction between these two variables. 
Consequently, no conclusive evidence emerged to support the existence of spillover. Interestingly, 
the observed reduced effort contradicts some questionnaire assumptions, but it aligns with the 
conclusion  of  the  absence  of  evidence  for  spillover.  There  are  various  hypotheses  on  why 
demonstrating spillover in this specific case could be difficult, ranging from the actual absence of 
spillover to the inherent difficulty in proving its existence. These findings highlight the challenges 
in attributing spillover effects to relatively small-scale MPAs, and the need for additional research 
in understanding their ecological impact. 

2  BACKGROUND 

2.1  The grey shrimp in the North Sea Coastal Zone 

The grey shrimp (Crangon crangon) fishery is one of the largest fisheries in the coastal zones of 
the Netherlands. In 2019, around 200 Dutch-flagged vessels caught grey shrimp. That year, these 
vessels landed 13 400 tonnes of shrimp with an estimated export value of 98 million euros, which 
is  estimated  to  be  80%  of  the  total  turnover  (Quirijns  et  al.,  2021)  The  auctions  around  the 
Wadden Sea in the North of the Netherlands (North Sea Coastal Zone, or NSCZ) accounted for 
82% of the total landings of grey shrimp of the Dutch fishery (Turenhout et al., 2015).  

The NSCZ is a is a rich body of water with a great diversity of marine life. The area was designated  
for  many  birds  under  the  Birds  Directive  since  2000,  and  for  many  habitat  types  and  habitat 
species since 2011 under the Habitats Directive (Natura2000). 

The potential ecological effects of the grey shrimp fishery in the shallow shelf of the North Sea 
and the Wadden Sea are currently heavily debated, especially because the fishery operates for a 
large  part in  designated  Natura2000  sites.  Fishing  with otter  and  beam  trawls  account  for  the 
major  part  of  shrimp  production,  as  these  gears  target  species  that  form  large  schools  over 
relatively level open ocean bottoms (Eigaard et al., 2017). Trawling physically disturbs the seabed 
by dragging fishing gear over the seabed to catch demersal fish and benthic invertebrates. The 
direct impacts are the physical disturbance on the habitat and on the organisms living on and in 
the seabed (Tulp et al., 2020). The shrimp fishery is known for its large amounts of bycatch of 

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benthos, flatfish (in particular plaice) and undersized shrimp. A reason for the high bycatch levels 
high the use of the smallest mesh size (20 mm) of the entire Dutch fishing industry (Jongbloed 
et al., 2015; Catchpole et al., 2008).   

The Netherlands have implemented marine protected areas (MPAs) to restore and conserve the 
environmental status and condition of the North Sea, including seafloor communities (EEA, 2018). 
In 2009/2010, the NSCZ was designated as a Natura 2000 area. This makes the area part of a 
European network of nature areas subject to special protection. To enable a combination of nature 
conservation  and  fisheries  within  the  Natura  2000  areas  in  the  North  Sea,  the  Fisheries  In 
Protected  Areas  Agreement  (VIBEG)  was  concluded  in  2011.  This  would  be  achieved  through 
closure of several areas within the NSCZ. The core of the agreement involves spatial zoning of 
areas for different types of fisheries, allowing various types of fisheries in some of these zones, 
and complete closure to shrimp fisheries in other zones. Specific area names and sizes are given 
in Table 1 and Figure 1. 

Table 1: Overview of shrimp-fishery restricted area sizes. 

Area 

Petten I 

Rottumeroog- en plaat I West 

Rottumeroog- en plaat I Oost 

Terschelling I West 

Terschelling I Oost 

Total 

Size 

30.8 km2 

25.4 km2 

34.0 km2 

18.7 km2 

34.9 km2 

143.8 km2 

Figure  1:  Overview  of  shrimp-fishery  restricted  areas  in  the  North  Sea  Coastal  zone, 
Netherlands. 

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Although areas were legally closed in 2013, January 2017 was considered as the cut-off point for 
adherence to the closure of the fishing areas. Officially, shrimp fishing was not allowed in these 
areas from 2013 onwards. At the time, shrimp fishers showed low  compliance: the majority of 
the fishers  continued to fish  in the closed  areas  (Wilkes,  2022). However,  when  the first fines 
were  handed  out  for  not  following  legal  spatial  fishing  restrictions  in  2016,  adherence  to  the 
restrictions in the areas appeared instantaneously (see Appendix). This was verified by looking at 
fishing effort in restricted areas over the years and months. In January 2017, there was a sudden 
drop in fishing effort in the restricted areas, corresponding with the time when the first fines had 
been distributed.  

Closing areas to fishing has the potential to be beneficial for fish populations in the long term. By 
designating  specific  zones  as  protected  areas,  fish  species  get  the  opportunity  to  recover  and 
replenish from  the  impacts of  fishing.  As these  fish  populations flourish within these  protected 
zones, they can attain higher biomass and increased abundance levels (Kaplan et al., 2019). The 
same might apply to shrimp. Over time, this can lead to a spillover effect, where surplus shrimp 
move beyond the protected areas and disperse to adjacent fishing grounds. Studies from other 
cases  have  demonstrated  that  well-managed  protected  areas  can  indeed  result  in  spillover, 
contributing to increased catches and yields in surrounding areas (Polacheck, 1990). This spillover 
effect not only benefits the fishing industry economically but also supports ecosystem health by 
promoting balanced populations and preserving biodiversity. Therefore, closing areas for fisheries 
can be a proactive measure to safeguard shrimp populations and enhance the sustainability of 
the  fisheries  in  the  long  run.  The  focus  of  this  study  is  to  analyse  the  presence  and  extent  of 
spillover from these closed areas and its potential benefits to fisheries. This study focuses on the 
permanently closed areas to shrimp fishing within the NSCZ. This study aims to provide insights 
into the dynamics of spillover in the NSCZ, its influence on fisheries, and about the methods to 
study them.  

2.2  The potential spillover effects 

In theory, spillover might benefit fisheries through increased or stabilized yields, making up for 
the lost fishing grounds caused by the creation of the MPA (Sanchirico, 2006; Gruss et al., 2011). 
Fish  populations  within  MPAs  contribute  to  the  harvestable  stock  through  two  primary 
mechanisms. Firstly, there is fishery spillover, which is the migration of harvestable individuals 
from the MPA into the adjacent regions, further augmenting the harvestable stock in those areas. 
Observing  or  analyzing  spillover  can  present  significant  challenges.  The  total  effects  on  fish 
populations both within the MPA and in surrounding areas can be small and exceptionally difficult 
to  detect  (Ovando  et  al.,  2021),  and  many  reasons  might  prevent  spillover  from  happening. 
Examples of these reasons are insufficient time since establishment of the MPAs (Friedlander et 
al., 2017), or ecological status of the species studied, as the chance of spillover occurring is higher 
for previously exploited species (Di Lorenzo, 2020). 

The  areas  that  were  closed  are  of  high  ecological  relevance,  and  the  focal  species  is  heavily 
exploited, which makes us think that taking out fishing pressure could have enormous ecological 
effects and conservation benefits. However, the areas were fully protected only recently. Although 
areas were legally closed in 2013, January 2017 was considered as the cut-off point for adherence 
to the closure of the fishing areas. As we will here analyse data until 2022, that gives us a time 
frame to see ecological effects that could have accumulated in 6 years only. Although this is not 
a long period of time, grey shrimp is considered a fast-growing and fast-reproducing species, with 
a relatively short life span of one-year only. They can reproduce multiple times during their life 
span. Shrimp larvae spend some time drifting with ocean currents before eventually settling to 
the seabed. Grey shrimps are generally mobile and can move between different areas in search 
of suitable habitats and food. While they might initially settle in the same general area where they 
were born, they are not strictly tied to those locations. However, the NSCZ does offer the best 
habitat for shrimp, increasing  the chances  of  them  staying there. In summary, the chances  of 
grey shrimp replenishing in the protected areas in the NSCZ to the point where they spillover is 
theoretically possible. 

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3  AIMS AND OBJECTIVES 

The main objective of this case study is to evaluate and quantify potential spillover effects around 
the closed areas in the NSCZ. We assessed changes in shrimp fisheries total catch in response to 
MPA implementation. A before-after-control impact design (BACI) observational experiment was 
set up. Changes in fishing effort, catch and catch value before and after the time at which the 
most substantial legal protections came into force were assessed, and focused in and around the 
protected areas during these two time periods. We evaluated and provided recommendations on 
the suitability and practicality of the chosen methodology for assessing spillover effects. 

4  METHODOLOGY 

4.1  Qualitative approach 

We developed a questionnaire to assess the perceptions of key stakeholders regarding the MPAs' 
potential  spillover  effects,  which  was  applied  to  the  NSCZ  area  (see  detailed  questionnaire  in 
Annex 4). Stakeholders were approached via an online questionnaire or through interviews. Four 
key stakeholder groups were targeted:  
- 
- 
- 
-  NGOs.  

commercial and recreational fishers,  
fisheries managers or government authorities,  
scientists, and  

The questionnaire aimed to gauge stakeholder perceptions on spillover effects around the closed 
areas. It had questions that covered the respondent’s relation to the protected areas and views 
on the restrictions, explored their perceptions regarding socio-economic effects resulting from the 
area  closure  and  asked  about  observed  and  expected  spillovers,  and  views  on  MPAs  as 
management tools in general.  

4.2  Quantitative approach 

The aim of our research is to investigate the potential presence of spillover effects. We examined 
the spatial distribution of biomass and abundance as indicators of density-related spillover. The 
biomass  estimates  are  deduced  from  data  obtained  from  both  logbook  and  Vessel  Monitoring 
System  (VMS)  records.  If  spillover  effects  are  present,  there  will  be  a  gradient  in  biomass, 
originating at the boundaries of the protected areas and diminishing with increasing distance from 
these  boundaries  (McClanahan  and  Mangi,  2000;  Abesamis  &  Russ,  2005).  We  compared  the 
spatial  distribution  of  biomass  before  and  after  the  establishment  of  the  protected  areas.  If  a 
gradient appeared, we additionally assessed whether this pattern strengthens with time since the 
establishment. Details on the statistical approach are given in section 4.4. 

4.3  The data 

The study area and MPAs 

This study focusses on the NSCZ (Figure 2). A range of 14 km from the coastline was used to 
delineate the study area, as this area contains around 97% of all shrimp-fisheries fishing effort 
(Wilkes, 2022). The study area had to be bordered to ensure not too many grid cells would hold 
a  0-hour  fishing  effort,  as  this  causes  challenges  in  the  analysis  such  as  failures  in  model 
convergence. Coordinates of the MPAs were provided by the Ministry of Economic Affairs (2013). 

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Figure 2: Map of the North Sea Coastal Zone (NSCZ) with the study area highlighted in 
yellow.  

VMS and logbook data 

Since  2005,  all  fishing  vessels  over  15  m  have  been  obligated  to  be  equipped  with  a  Vessel 
Monitoring  System  (VMS).  In  2012,  this  became  obligatory  for  all  vessels  over  12  m.  A  VMS 
transponder sends a signal at regular intervals to a satellite providing information on the vessel’s 
ID,  position,  time  and  date,  direction,  and  speed.  Hence,  VMS  is  a  valuable  data  source  for 
studying  the  spatial  and  temporal  distribution  of  fishing  fleet.  Wageningen  Marine  Research 
receives  VMS  and  logbook  data  from  the  Netherlands  Enterprise  Agency  (RVO)  for  scientific 
purposes. For this study, VMS and logbook data from the time period 2012 to 2021 were used. 
The VMS is coupled to fisheries logbooks, which contain information on when fishers leave the 
harbour, what gear has been used for fishing, their catch composition, and a rough estimate of 
the location of the catches for every 24 hours.  

Data processing 

First, VMS and logbook datasets were cleaned following steps of Hintzen et al (2022). They were 
then  linked  using  the  unique  vessel  identifier  and  date-time  stamp  in  both  datasets  available. 
Fishing expeditions using bottom  gear types known  to fish shrimp, beam trawlers (code TBB), 
were selected. Lastly, cumulative fishing hours were aggregated by 0.05 degree C-square, and 
separated for year (and therewith, before or after restrictions). 

4.4  Statistical analysis 

The response variable is the catch (shrimp biomass in cumulative kg), fishing effort (in cumulative 
hours)  or  mean  CPUE  (kg/h)  per  0.05  degree  c-square  per  year.  To  test  the  hypotheses, 
generalized linear mixed models (GLM) with a gaussian error distribution were fitted. The specific 
analysis and model structure is described per theme below. 

Changes in fishing effort and catches before and after MPA establishment 

To assess changes in fishing effort, total catch and CPUE before and after spatial restrictions were 
established, three models were formulated with the above response variables in relation to the 
period (before or after restrictions) (models 1 to 3). This allowed to test whether effort, biomass 
or  CPUE  changed  significantly  since  the  enforcement  of  protected  areas,  and  whether  this  is 
specific to a particular species or not. 

Fishing effort (hours) ~ Period (before vs after)  
Fishing biomass (kg) ~ Period (before vs after)  

• 
• 
•  CPUE (kg/hour) ~ Period (before vs after)  

(model 1) 
(model 2) 
(model 3) 

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Increasing biomass since establishment of MPA 

To assess if any spillover effects are present, it should be tested if there is a gradient of biomass 
or abundance  that starts at the  boundary  of  the protected  area  and decreases with increasing 
distance from the boundary. To prevent that this is a coincidental natural spatial pattern of the 
species to occur, it would be conclusive if this effect gets stronger with time since establishment 
of the protected area. We therefore tested CPUE (as this already accounts for effort) in relation 
to an interaction of years since establishment, distance to the MPA, and species, as the effects 
might be specific per species (model 4). 

•  Δ biomass (before vs after) per 0.05 c-square per year  ~ Offset (fishing effort) + Fishing 

distance from MPA  

(model 4) 

Software 

Analyses were carried out in R (R version 3.6.3, R Core Team, 2020 & R studio version 1.3.959 
(RStudio Team, 2020). The data processing used the VMStools R-package (Hintzen et al. 2012) 
and all its dependencies.  

5  RESULTS 

5.1  Qualitative approach: key findings of the questionnaire 

The  questionnaire  was  filled  in  by  three  scientists  of  Wageningen  Marine  Research,  one  Policy 
Advisor North Sea Marine Protected Areas, Ministry Agriculture, Nature, and Food Quality (LNV), 
and one senior advisor of Rijkswaterstaat (the executive agency of the ministry of infrastructure 
and water management).  

The following results were summarized from the questionnaire input. The coastal area has had a 
management  plan  in  place  since  2016,  but  it  does  not  include  spillover  in  its  conservation 
objectives. Fishing within the NSCZ MPAs is regulated through permit conditions. Specific fishing 
methods  are  permitted,  including  beam  trawl  fishing  with  tickler  chains,  shrimp  fishing,  otter 
trawling, and shellfish dredging. These regulations aim to minimize the impact on conservation 
objectives. Certain zones within the MPA have restrictions, with some allowing only shrimp fishing, 
while others are entirely closed to commercial fishing. Professional fishing activities in the MPA 
require a Nature Act permit. Fishery management authorities believe that the most effective policy 
measures to promote spillover from MPAs are fishery restrictions or even full closure within the 
MPA. 

There  is  currently  no  dedicated  research  or  monitoring  program  aimed  at  studying  spillover 
effects. While there are some related projects, most of them are ad hoc and primarily focused on 
stock  and  ecology  for  sustainable  fisheries  rather  than  the  MPA's  focus.  Research  Priorities: 
Spillover  is  not  considered  a  priority  topic  in  future  research  agendas.  However,  fishery 
management  authorities  do  suggest  collaborative  initiatives  between  research  groups,  local 
fishing communities, and fisheries management authorities to understand and manage spillover 
impacts, although such initiatives have been limited, partly due to the small scale of MPAs. 

Fishery management authorities have limited knowledge about whether fishers have experienced 
changes  in  catches  within  the  MPA.  They  also  do  not  believe  that  spillover  from  the  MPA  has 
significantly contributed to the recovery of overexploited fish stocks. They agree that there is no 
evidence of spillover of fish or larvae from the MPAs and suggest that the MPAs are too small to 
benefit fisheries. They  maintain  a neutral stance  regarding the economic benefits for fisheries. 
The fishing community does not perceive increased livelihood security due to restrictions, which 
are generally not well-received. 

Two  out  of  three  scientists  are  uncertain  if  there  have  been  changes  in  seabed  habitats, 
biodiversity,  or  structural  complexity  within  the  MPA.  One  scientist  noted  that  a  BACI-study 
showed no clear results, primarily due to fishing activity in the closed area. Two scientists have 
not  observed  changes  in  fish  abundance,  biomass,  or  species  composition,  while  one  noted 
significant within-year and between-year variations, making it challenging to determine significant 
changes. According to them, it is unlikely that spillover is occurring from fully protected areas and 
very unlikely from partially protected areas due to ongoing fishing activities, but they stress the 
need for further studies in this regard. One scientist believes that fisheries economically benefit 

60 

 
 
 
 
 
 
 
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from the MPA, as permits lead to a reduction in fishing effort, benefiting shrimp catches, provided 
shrimp  prices  remain  stable.  Scientists  have  varying  opinions  on  the  necessity  of  closures  to 
develop  commercial  fisheries,  emphasizing  the  need  for  further  research  before  implementing 
such measures. 

One scientist believes spillover is possible and highlights key factors, including the MPA's size, the 
time since its establishment, the effectiveness of total closure compared to partial closure with 
restrictions,  the  importance  of  habitat  composition,  and  pressures  around  the  MPA  borders.  A 
former  WWF  employee  involved  in  VIBEG  believes  there  is  barely  any  spillover  effect  due  to 
minimal  decreases  in  fishing  pressure.  A  scientist  acknowledges  the  challenges  of  assessing 
spillover in shrimp fishing, citing the presence of shrimp fishing in areas near the coast and the 
Dutch Natura 2000 areas. They emphasize that many factors, beyond the coastal MPAs, affect 
the  status  of  commercial  fish  species.  The  scientist  notes  that  border  effects  have  not  been 
thoroughly studied, and there is a lack of knowledge regarding the movement and distribution of 
many species. 

5.2  Quantitative approach: changes in fishing effort, catch and CPUE 

First, we assessed whether there was a change in fishing effort before and after the MPAs in the 
NSCZ were established. Fishing effort was captured as time fished per year (in days) per 0.05 c-
square.  The  model  significantly  diverged  from  the  control  model  (p<0.001).  There  was 
significantly higher effort  in the period before  the  establishment of the MPA  compared  to after 
(Intercept=24.620,  estimate  “before”=3.776,  p<0.001).  Potential  changes  in  biomass  were 
assessed similarly. Biomass is represented as the catch in kg per year per 0.05 degree C-square. 
This model did nod diverge from the control model (p=0.307). Lastly, the change in CPUE was 
tested to the period. The response variable here was catch in mean kg per day for every year per 
0.05 degree c-square. This model significantly diverged from the control model (p<0.001). CPUE 
was  significantly  lower  in  the  period  before  the  MPAs  were  established  (Intercept=1  337.70, 
estimate “before”=-187.04, p<0.001). An overview of catch statistics is given in Table 3. 

Table 2: Model output for models 1 to 3. These tables display the estimates (coefficient) 
and  p-values  for  predictor  variables  (p  variable)  and  their  sub-variables  (p  sub-
variable). P values are not shown for the intercept and lower levels if an interaction is 
significant due to limited interpretative value. The model formula is specified below: 

Model  1:  Fishing  effort  (days  per  c-square  per  year)  ~  Period  (before  vs  after) 
This model is significant (p<0.001) 

Estimate 

Standard error 

P-value 

Intercept 

Period (before) 

24.620 

3.776 

0.763 

1.080 

- 

< 0.001 

Model  2:  Fishing  biomass  (sum  kg  c-square  per  year)  ~  Period  (before  vs  after) 
This model was not significant (p=0.307) 

Model  3:  CPUE  (mean  kg/day  per  c-square  per  year)  ~  Period  (before  vs  after) 
This model was significant (p<0.001) 

Estimate 

Standard error 

P-value 

Intercept 

1 337.71 

Period (before) 

-178.04 

51.180 

72.450 

- 

< 0.001 

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Table 3: Catches, effort and mean CPUE (2012-2021) 

Year 

Protected  Total KG 

Total effort ( days)  CPUE (kg/day) 

p
m

i
r
h
S

)
n
o
g
n
a
r
c

n
o
g
n
a
r
C
(

2012 
2013 
2014 
2015 
2016 
2017 
2018 
2019 
2020 
2021 

e
r
o
f
e
b

r
e
t
f
a

7 571 238 
10 695 780 
12 393 851 
9 662 993 
9 166 405 
5 725 544 
15 402 237 
10 306 681 
10 914 527 
9 656 004 

8 803 
9 923 
11 293 
9 309 
10 196 
8 215 
8 455 
7 207 
9 768 
9 464 

914 
1 199 
1 309 
1 300 
1 024 
693 
2 016 
1 575 
1 267 
1 152 

Increasing biomass since establishment of MPAs, and closer to the border of the MPAs? 

Lastly, we assessed whether there was an increasing trend in biomass for shrimp since the date 
of adherence to the fishing restrictions, and whether this was strongest near the MPA. CPUE was 
tested to a two-way interaction with period (before and after) and distance to the border of the 
nearest MPA (as there are four smaller areas) in the NSCZ. This model did not differ significantly 
from the control model (p=0.860). Additionally, we also selected data only after establishment of 
the MPA, and tested the potential interactive effect of the interaction between distance from the 
MPA and years since establishment of the MPA. As CPUE estimates are aggregated per year, time 
since establishment was counted per year as well. Again, this model did not differ significantly 
from the control model (p=0.665). The change in CPUE is visualized in space in Figure 3.  

Figure  3:  CPUE  change  (%)  in  NSCZ.  This  map  displays  the  research  area,  with  cells 
color-coded to represent the change  in CPUE (the  difference in mean CPUE per year) 
after establishment of MPAs in the NSCZ. 

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6  DISCUSSION 

The analysis initially focused on descriptive statistics, examining changes in total effort, total catch 
biomass,  and  CPUE  of  shrimp  following  the  establishment  of  the  MPAs  in  the  NSCZ.  It  was 
observed  that  shrimping  effort  significantly  decreased  within  the  NSCZ  after  the 
establishment  of  the  MPAs.  However,  the  quantity  of  shrimp  caught  did  not  show 
significant  differences  before  and  after  the  establishment.  Aligning  with  previous 
findings, CPUE did increase significantly.  

The increase in CPUE does not testify for a relative increase in biomass. As many fishers agreed 
with  a  buy-out  proposal  when the  protected  areas  were  established,  fishing effort  significantly 
decreased, as was seen in the results. As a consequence, there was less competition, which 
could be an explanation for the increase in CPUE.  

Building on this understanding of shrimp dynamics before and after establishment  of the MPAs, 
the analysis progressed into testing specific hypotheses related to spillover effects. It sought to 
determine if there was a growing trend in shrimp biomass closer to the borders of the nearest 
MPAs and whether this trend  intensified  over the  years following MPA adherence. The  analysis 
found no significant effects related to distance to the nearest MPA, years since MPA establishment, 
or  the  interaction  between  these  two  variables.  Consequently,  no  conclusive  evidence 
emerged to support the existence of spillover in this case study. If spillover occurs on a 
very small scale or at low abundances, the spatial and temporal resolution of the current dataset, 
constructed  from  VMS  and  logbook  data,  may  be  too  coarse  to  capture  such  nuances.  A 
recommendation for future studies could involve analysing biomass changes from the MPA border 
using  non-binned  biomass  observations  (not  segmented  into  c-squares).  Alternatively, 
distributing  logbook  catch  data  along  a  finer  fishing  vessel  travel  path,  perhaps  based  on 
Automatic  Identification  System  (AIS)  data  with  more  frequent  observations  in  time,  could 
enhance the precision of the analysis. 

Comparing  the  questionnaire  responses  to  the  quantitative  results  led  to  the  following 
conclusions. Fishery management authorities exhibited limited awareness of changes in 
catches  within  the  MPAs  and  held  the  belief  that  spillover  had  not  significantly 
contributed  to  the  recovery  of  overexploited  fish  stocks.  Furthermore,  the  fishing 
community  did  not  perceive  increased  livelihood  security  resulting  from  restrictions, 
which  were  generally  met  with  resistance.  This  study  observed  an  increase  in  CPUE,  and 
even though this is most likely not a result of spillover, it contradicts the lack of changes perceived 
by  the  fishery  management  authorities.  Also,  a  significant  reduction  in  effort  was  found  after 
establishment  of  the  MPAs,  contrary  to  several  beliefs  from  the  questionees.  Therefore,  the 
absence of conclusive evidence for spillover cannot be attributed to an absence of reduced effort. 
Lastly,  our  findings  align  with  the  questionees  lack  of  observed  changes  in  earlier  research 
assessing shrimp biomass or abundance in the overall area over the last years.  

There may be several reasons why this study was unable to demonstrate spillover. It 
could be that spillover is not happening. Shrimp in the North Sea are generally abundant and not 
subject  to  significant  conservation  concerns.  It  could  be  that  for  this  species,  there  were  no 
spillover effects as fishing pressure was not a limiting factor for the species. The NSCZ had only 
recently implemented its MPAs, which might not have allowed sufficient time for spillover effects 
to become pronounced. Spillover can be a gradual process, and the relatively short timeframe of 
the study may not have captured long-term trends. The NSCZ MPAs were relatively small in scale, 
which could limit their potential to generate significant spillover effects. Larger MPAs often have 
a  greater  capacity  to  support  spillover  due  to  their  size  and  the  diversity  of  habitats  they 
encompass  (Di  Lorenzo  et  al.,  2020).  If  spillover  was  happening,  there  could  be  other 
reasons. While shrimp can move, they tend to stay within a relatively small spatial area on the 
seabed, making chances of shrimp spilling over to adjacent areas relatively small. It could be that 
our research area is inappropriate in size to capture the effect of proximity to the MPA adequately. 
It  would be  less  complicated  to  study  one  MPA  rather  than  four  smaller  MPAs  in one  research 
area. These reasons emphasize the complexity of assessing spillover.  

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7  CONCLUSIONS 

In conclusion, the analysis of shrimp dynamics in the NSCZ post-MPAs did not provide conclusive 
evidence of spillover.  Shrimping effort decreased significantly  after MPA  implementation, while 
total shrimp catch quantity remained largely unchanged. Consistently, there was an increase in 
CPUE, likely due to reduced competition following buy-out proposals, rather than due to spillover 
effects. The study aimed to test spillover hypotheses but found no significant evidence regarding 
MPA proximity or establishment duration. Interestingly, the observed reduced effort contradicts 
some questionnaire assumptions, but it aligns with the conclusion of the absence of evidence for 
spillover. There are various hypothesis on why demonstrating spillover seemed difficult, ranging 
from  the  actual  absence  of  spillover  to  the  inherent  difficulty  in  proving  its  existence  with  the 
existing data. These findings highlight the challenges in attributing spillover effects to relatively 
small-scale MPAs, and the need for additional research in understanding their ecological impact. 

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protected areas and its drivers: A meta‐analytical approach. Fish and Fisheries, 21(5), 906-915 

Eigaard,  O.  R.,  Bastardie,  F.,  Hintzen,  N.  T.,  Buhl-Mortensen,  L.,  Buhl-Mortensen,  P.,  Catarino,  R.,  ...  & 
Rijnsdorp, A. D. (2017). The footprint of bottom trawling in European waters: distribution, intensity, and 
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European  Environmental  Agency  (EEA),  Marine  protected  areas  in  Europe’s  regional  seas,  2018.  Retrieved 
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Forcada, A., Valle, C., Sánchez-Lizaso, J. L., Bayle-Sempere, J. T., & Corsi, F. (2010). Structure and spatio-
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Marine Science, 67(2), 191-203. 

Friedlander, A. M., Golbuu, Y., Ballesteros, E., Caselle, J. E., Gouezo, M., Olsudong, D., & Sala, E. (2017). 
Size,  age,  and  habitat  determine  effectiveness  of  Palau's  Marine  Protected  Areas.  PloS  one,  12(3), 
e0174787. 

Greenstreet,  S.  P.  R.,  Fraser,  H.  M.,  &  Piet,  G.  J.  (2009).  Using  MPAs  to  address  regional-scale  ecological 
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Science, 66(1), 90–100. https://doi.org/10.1093/icesjms/fsn214 

Grüss, A., Kaplan, D. M., Guénette, S., Roberts, C. M., & Botsford, L. W. (2011). Consequences of adult and 

juvenile movement for marine protected areas. Biological Conservation, 144(2), 692-702. 

Hintzen, N. T., Bastardie, F., Beare, D., Piet, G. J., Ulrich, C., Deporte, N., ... & Degel, H. (2012). VMStools: 
Open-source  software  for  the  processing,  analysis  and  visualisation  of  fisheries  logbook  and  VMS 
data. Fisheries Research, 115, 31-43. 

Jongbloed, R. H., Steenbergen, J., van Kooten, T., Turenhout, M. N. J., & Taal, C. (2015). Expert judgement 
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Kaplan, K. A., Yamane, L., Botsford, L. W., Baskett, M. L., Hastings, A., Worden, S., & White, J. W. (2019). 
Setting  expected  timelines  of  fished  population  recovery  for  the  adaptive  management  of  a  marine 
protected area network. Ecological Applications, 29(6), e01949. 

McClanahan, T. R., & Mangi, S. (2000). Spillover of exploitable fishes from a marine park and its effect on the 

adjacent fishery. Ecological applications, 10(6), 1792-1805. 

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Koninkrijk  der  Nederlanden.  Officielebekendmakingen.nl.  consulted  on  29  March  2023, 
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Ovando, D., Caselle, J. E., Costello, C., Deschenes, O., Gaines, S. D., Hilborn, R., & Liu, O. (2021). Assessing 
the population‐level conservation effects of marine protected areas. Conservation Biology, 35(6), 1861-
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Paulrud, A., Carvalho, N., Borrello, A., & Motova, A. (Eds.). (2015). The 2015 Annual Economic Report on the 
EU Fishing Fleet (STECF 15-07): Scientific, Technical and Economic Committee for Fisheries (STECF). JRC 
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Polacheck, T. (1990). Year around closed areas as a management tool. Natural Resource Modeling, 4(3), 327-

354 

Quirijns,  F.,  Beier,  U.,  Deetman,  B.,  Hoekstra,  G.,  Mol,  A.,  &  Zaalmink,  W.  (2021). Beschrijving 
garnalenvisserij:  Huidige  situatie,  knelpunten  en  kansen.  (Wageningen  Marine  Research  rapport;  No. 
C049/21). Wageningen Marine Research. https://doi.org/10.18174/547410 

Sanchirico, J. N., Malvadkar, U., Hastings, A., & Wilen, J. E. (2006). When are no‐take zones an economically 

optimal fishery management strategy?. Ecological Applications, 16(5), 1643-1659. 

Slijkerman, D. M. E., & Tamis, J. E. (2015). Fisheries displacement effects related to closed areas: a literature 

review of relevant aspects. Wageningen Marine Research report. 

Tulp, I., Glorius, S., Rippen, A., Looije, D., & Craeymeersch, J. (2020). Dose-response relationship between 
shrimp trawl fishery and the macrobenthic fauna community in the coastal zone and Wadden Sea. Journal 
of Sea Research, 156, 101829. 

Turenhout,  M.  N.  J.,  van  Oostenbrugge,  J.  A.  E.,  &  Beukers,  R.  (2015). Economische  kengetallen 
garnalenvisserij:  Aanvulling  op  ‘Expert  judgement  garnalenvisserij’.  (Nota  /  LEI  Wageningen  UR;  No. 
2015-138). LEI Wageningen UR. https://edepot.wur.nl/375414 

Wilkes, T. (2022). A statistical model for the spatial effort allocation of shrimp fishers in the Dutch coastal 
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APPENDIX 

Overview of shrimp-fishery activity in one of the restricted areas (Terschelling I Oost) in the North 
Sea Coastal zone over time, to establish when fishing regulations were adhered to by fishers. The 
variable shown is fishing hours (fhr) at a specific location, with the colour corresponding to the 
cumulative hours that  year in  that  specific location (fhr.sum  in the legend), with darker colors 
indicating more fishing hours.  Only observations within the area polygon are plotted. From 2017, 
there is a sudden drop in overall fishing activity in the restricted area (Wilkes, 2022).  

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5.  CASE STUDY REPORT: 

BORSSELE OFFSHORE WIND FARM ZONE 

THE NETHERLANDS – NORTH SEA 

Borssele Wind Farm seen from the sky. Ørsted/Sky Pictures 

Analysis of potential spillover effects around 
Borssele offshore wind farm zone 

Tamara Vallina 
Wageningen Marine Research, Wageningen University and Research 

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TABLE OF CONTENTS 

1 
2 
3 
4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ........................................................................................... 69 
BACKGROUND ...................................................................................................... 69 
AIMS AND OBJECTIVES ......................................................................................... 71 
METHODOLOGY .................................................................................................... 71 
4.1  Qualitative approach .................................................................................... 71 
4.2  Quantitative approach .................................................................................. 71 
The data .................................................................................................... 71 
4.3 
The study area ............................................................................................ 71 
VMS and logbook data ................................................................................. 71 
Data processing .......................................................................................... 72 
Identifying relevant species .......................................................................... 72 
4.4  Statistical analysis ....................................................................................... 73 
Changes  in  fishing  effort  and  catches  before  and  after  the  wind  farm 

establishment ................................................................................ 73 
Increasing biomass closer to the wind farm, since establishment? ..................... 73 
Software  .................................................................................................... 73 
RESULTS ............................................................................................................. 74 
5.1  Qualitative approach to stakeholders of the BOWFZ ......................................... 74 
5.2  Changes in fishing effort and catches in the study area before and after the 

wind farm establishment .............................................................................. 74 
Increasing biomass since establishment of wind farm? ..................................... 76 
DISCUSSION ....................................................................................................... 80 
CONCLUSIONS ..................................................................................................... 80 
REFERENCES ....................................................................................................... 81 

LIST OF ABBREVIATIONS 

Term 

AIC 

BACI 

Description 

Akaike Information Criterion 

Before-After-Control-Impact 

BOWFZ 

Borssele offshore wind farm zone 

CPUE 

Catch per unit of effort 

DAB 

EEZ 

GUU 

LNV 

NL 

Common dab 

Exclusive economic zone 

Tub gurnard 

Ministry of Agriculture, Nature and Food Quality 

Netherlands 

OECM 

Other effective area-based conservation measure 

RVO 

SOL 

TBB 

VMS 

The Netherlands Enterprise Agency 

Common sole 

Beam trawlers 

Vessel monitoring system 

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1  EXECUTIVE SUMMARY  

The Borssele offshore wind farm zone (BOWFZ) is a recently established offshore wind farm of 
344 km2, situated in the North Sea off the coast of Zeeland province in the Netherlands. The wind 
farm zone prohibits any boating activity through its wind farms, resulting in a significant loss of 
space for fishing activities. In this study, the wind farm zone is considered as an ‘other effective 
area-based  conservation  measure’  (OECM).  To  better  understand  the  consequences  on  the 
establishment  of  the  BOWFZ  for  the  local  fisheries,  there  is  a  need  to  study  the  influence  on 
fisheries catches, and examine the potential benefit of fish spillover from the BOWFZ. 

This case study assessed qualitatively and quantitatively the potential of having spillover effects 
from the BOWFZ to adjacent areas. As wind farms share aspects of traditional marine protected 
areas  (MPAs)  such  as  the  inability  to  enter  and  fish  in  the  area,  we  consider the  BOWFZ  as  a 
relevant case study. We analysed potential spillover of common sole (Solea solea), common dab 
(Limanda limanda) and tub gurnard (Chelidonichthys lucerne) biomass around the BOWFZ. This 
trio-species approach enriches our understanding of species-specific spillover dynamics.  

In  theory,  perfect  density-related  spillover  would  exhibit  a  gradient  of  biomass  or  abundance 
originating at the BOWFZ  boundary, diminishing as distance from the boundary increases, and 
growing stronger over time. To examine these hypotheses, we employed generalized linear mixed 
models (GLM). The models were constructed to assess biomass (in cumulative kilograms), fishing 
effort (in cumulative hours), or mean catch per unit effort (CPUE) (kilograms per hour) per 0.05-
degree c-square annually for the three species. The analysis considered factors such as the time 
period, species, and proximity to the BOWFZ. 

The analysis revealed a significant reduction in total effort, total catch, and  CPUE following the 
establishment of the BOWFZ for all species. This suggests lower overall productivity in the later 
years. When testing whether there was an increasing trend in biomass for the focal species since 
the  BOWFZ  establishment,  taking into  account the distance  to the  BOWFZ, no evidence  for an 
interactive effect was found. The magnitude of any effects near the borders of the BOWFZ for tub 
gurnard, sole or place were found to be biologically inconsequential. Consequently, no concrete 
evidence  to  substantiate  the  existence  of  spillover  was  found.  These  findings  are  however 
congruent to the insights gathered from the stakeholders via the questionnaires. It is reasonable 
to  attribute  the  absence  of  conspicuous  spillover  effects  in  this  study  to  the  relatively  recent 
establishment of the BOWFZ. Future research could continue monitoring and research spillover 
over a longer duration, explore non-linear responses of the species population in response to the 
BOWFZ establishment, and assess the potential long-term effects on the broader ecosystem. 

2  BACKGROUND 

The  North  Sea  has  historically  been  a  vital  fishing  ground.  In  recent  years,  the  quest  for 
sustainable energy sources has led to a sharp increase in the establishment of marine offshore 
windfarms  in the  North  Sea.  One  recently  established  wind  farm is  the  Borssele  offshore  wind 
farm  zone  (BOWFZ),  situated  in  the  North  Sea  off  the  coast  of  Zeeland  province  in  the 
Netherlands.  Throughout  its  history  and  persisting  presently,  the  province  of  Zeeland  has 
remained  an  important  centre  within  the  Netherlands'  fishing  industry  (Bennema  &  Rijnsdorp, 
2015). 

While wind farms play a pivotal role in advancing the sustainable energy agenda, they are often 
met  with  resistance  from  the  fishing  industry.  To  better  understand  the  consequences  on  the 
establishment  of  the  BOWFZ  for  the  local  fisheries,  there  is  a  need  to  study  the  influence  on 
fisheries catches,  and examine the potential benefit of fish spillover from the  BOWFZ.  As wind 
farms share aspects of traditional marine protected areas (MPAs), such as the inability to enter 
and fish in the area, this area qualifies as an ‘other effective area-based conservation measures’ 
(OECM), and we consider the BOWFZ as a relevant case study. Studying spillover effects will give 
us insight in the ecological effects of the BOWFZ. It will also give us insight in the consequences 
for the fishers previously operating in the area, and quantify any potential benefits. 

The  BOWFZ  is  home  to  two  wind  farms,  operated  by  Ørsted  and  Blauwwind  (Noordzeeloket). 
These two wind farms are divided into two sections each, known as Borssele 1 & 2 and Borssele 
3, 4, and 5, as illustrated in Figure 1. The closest point to the shore is approximately 22 km, and 
under clear conditions, the wind farm is visible from Domburg. Comprising 173 wind turbines and 
covering an area of 344 km2, the BOWFZ has been operational since 2020 and is anticipated to 
remain  so  until  2046.  Compared  to  other  existing  wind  parks,  this  represents  a  relatively 

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expansive and substantial area dedicated to offshore wind energy production. Notably, the wind 
farm zone prohibits any boating activity through its wind farms, resulting in a significant loss of 
space for fishing activities.  

The establishment of the  BOWFZ involved a top-down approach where government authorities 
collaborated with industry stakeholders to create the wind farm zone. The BFWZ does not have 
an MPA designation, but  as the  wind farm zone  prohibits any boating activity through its wind 
farm,  it  aligns  with  some  standards  of  a  no-take-zone  MPA.  These  restrictions  are  in  place  to 
safeguard the structural integrity of wind turbines, ensuring their efficient operation and the safety 
of all parties involved. Fisheries agreement varied, but their engagement is considered essential 
in  achieving  an  equilibrium  between  conservation  and  economic  interests.  Although  there  is 
ongoing research and experiments on opportunities on passive fisheries in the windfarm, fishers 
have mostly refrained from registering for this initiative (Nooitgedagt, 2021). 

Adjacent to the BOWFZ is the Belgian wind farm zone, which has been under construction since 
2007,  including  the  latest  sites  that  share  some  infrastructure  with  the  Dutch  wind  farm.  The 
combined area of the wind farm zones in both the Netherlands and Belgium currently exceeds 
600 km2 (Brasseur et al., 2022). As there was a major time gap between the construction of the 
Belgium and Dutch part of the wind farm zone, we focused here on the Dutch part only11.  

Figure 1: This map illustrates the spatial layout of the Borssele offshore wind farm zone, 
located  off  the  Zeeland  coast  in  the  North  Sea,  Netherlands  (Source:  Netherlands 
Enterprise Agency 2023).  

11 Another case study under the SPILLOVER study dealt with the Belgian wind farm zone.   

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3  AIMS AND OBJECTIVES 

The aim  of this  case  study  is to  analyse  potential  spillover of  sole  (Solea solea), common dab 
(Limanda limanda) and tub gurnard (Chelidonichthys lucerna) from the BOWFZ to adjacent areas. 
The specific objective is to compare fishing effort, total biomass of landings and CPUE for these 
species for the period before the establishment in relation to the period after the establishment, 
and  to  test  for  spillover-related  patterns  in  the  distribution  of  these  species.  This  trio-species 
approach enriches our understanding of species-specific spillover dynamics.  

4  METHODOLOGY 

4.1  Qualitative approach 

A  survey  was  designed  to  evaluate  the  perspectives  of  key  stakeholders  regarding  potential 
spillover  effects  and  was  applied  to  the  BOWFZ  area.  Several  stakeholders  were  approached 
through an online questionnaire (see questionnaire in Annex 4). The survey targeted commercial 
and  recreational  fishers,  fisheries  managers  or  government  authorities,  scientists,  and  non-
governmental organizations (NGOs). The questionnaire aimed to gauge stakeholder opinions on 
spillover effects in the proximity of the wind farm zone. The questions asked for the respondents' 
connection  to  the  area,  and  asked  for  their  perceptions  about  the  inaccessibility  to  the  zone, 
delved into their viewpoints concerning socio-economic implications arising from area closures, 
and asked for information on both observed and anticipated spillover effects. Additionally, it asked 
for their opinions on MPAs as a broader management tool.  

4.2  Quantitative approach 

Our research aims to explore the potential occurrence of spillover effects within the BOWFZ. Our 
investigation focused on analyzing the spatial distribution of fish biomass as indicators of density-
related spillover. Biomass  estimates  were  derived from  comprehensive datasets obtained from 
both  logbook  and  vessel  monitoring  system  (VMS)  records.  If  any  spillover  is  present,  we 
anticipated  observing  a  gradient  in  biomass  from  the  border  of  the  BOWFZ.  This  gradient  is 
expected to originate from the boundaries of the protected areas and decrease as distance from 
these demarcated zones increases (McClanahan and Mangi, 2000; Abesamis & Russ, 2005). We 
conducted  a  comparative  analysis  of  the  spatial  distribution  of  biomass  before  and  after  the 
establishment of the protected areas. Moreover, we evaluated whether the spatial distribution of 
the observed biomass changed over time following the establishment. Details on the statistical 
approach are given in Section 4.4. 

4.3  The data 

The study area 

This research focuses on the BOWFZ as illustrated in Figure 1.  Coordinates for the BOWFZ were 
acquired  from  the  Netherlands  Enterprise  Agency  (RVO)  (2023)  to  delineate  the  BOWFZ 
accurately. The study area was defined using a 25 km buffer from the BOWFZ boundary, chosen 
to encompass a sizeable region relevant for detecting potential spillover effects (Figure 2). 

VMS and logbook data 

Since 2005, there has been a mandate for all fishing vessels exceeding 15 meters in length to 
integrate a VMS. This requirement was extended in 2012 to encompass all vessels surpassing 12 
meters in length. A VMS transponder continually transmits data to a  satellite, providing details 
such as the vessel's identification, position, time, date, direction, and speed. Consequently, VMS 
serves  as  a  valuable  data  source,  enabling  the  examination  of  the  fishing  fleet's  spatial  and 
temporal  distribution.  For  scientific  purposes,  Wageningen  Marine  Research  receives  VMS  and 
logbook  data  from  the  RVO.  In  this  study,  we  utilized  VMS  and  logbook  data  covering  the 
timeframe from 2017 to 2022. The VMS data are complemented by fisheries logbooks, which add 
information  regarding  the  departure  times  from  the  harbour,  gear  employed  for  fishing,  catch 
composition, and approximate catch locations recorded every 24 hours by fishers. 

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Data processing 

First, VMS and logbook datasets were cleaned following steps of Hintzen (2022). They were then 
linked  using  the  unique  vessel  identifier  and  date-time  stamp  in  both  datasets  available.  Only 
trips that caught either sole (SOL) or tub gurnard (GUU) or common dab (DAB) were identified. 
Per species, the main gear catching those species were identified by analyzing logbook data of 
vessels fishing in the Dutch Exclusive Economic Zone (EEZ). For sole, beam trawlers (TBB) and 
pulse fisheries (PUL) were responsible for 86 % of the total catch. For mullet, Scottish seine (SSC) 
was responsible for 90 percent of the total catch. Trips that caught these species with other gear 
were  excluded,  to  prevent  the  chances  of  including  trips  that  were  mainly  focussing  on  other 
species but caught these focal species as bycatch. From the gear types that were filtered for, only 
vessels were selected that caught less than 1000 kg of sole in a year, and less than 100 kg of 
mullet in a year, again to prevent including trips in which these species were not the main targeted 
species. Fishing trips using bottom gear types known to fish sole or mullet were selected. Lastly, 
cumulative fishing hours were aggregated by 0.05 degree c-square, and separated for year (and 
therewith, before or after restrictions). We considered aggregation per year most appropriate as 
it averages out seasonal fluctuations. We calculated total catch, effort and CPUE.   

Figure 2: Spatial layout of the Borssele offshore wind farm zone, located off the Zeeland 
coast in the North Sea. The distinct zonation of the wind farm area is highlighted in red. 
The buffer of 25 km around the BOWFZ indicates the general study area. 

Identifying relevant species 

From the top 10 most heavily fished species in the area, we selected 3 demersal fish species for 
further analysis. By choosing the most commonly fished species (in biomass in the  BOWFZ and 
buffer zone), we know that there is a pressure on the population, which increases the possibility 
that the closure of the areas would lead to significant protection of a previously pressured species. 
To detect potential spillover effects, the species cannot be too mobile, or any potential effects of 
the  area  will  be  impossible  to  test.  That  is  reason  why  demersal  species  were  selected.  The 
selected species have varying commercial interest. Eventually, sole (Solea solea), common dab 
(Limanda limanda) and tub gurnard (Chelidonichthys lucerna) were selected (Table 1).  

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Table 1: Gear types responsible for species catch 

Code 

species (EN) 

species (NL) 

SOL 

Common sole 

Tong 

KG caught 
(2019) 
705 338 

DAB 

Common dab 

Schar 

129 104 

72 % PUL 

GUU 

Tub gurnard 

Rode poon 

70 704 

73 % PUL 

Gear type catching species 

2019 

2022 

93 % PUL 

87 % TBB 

49% TBB  
& 37 % TBS 
87 % TBB 

4.4  Statistical analysis 

The response variable is the either biomass (in cumulative kg), fishing effort (in cumulative hours) 
or mean CPUE (kg/h) per 0.05 degree c-square (approximately 4 x 4 km) per year for common 
sole, common dab, and tub gurnard separately. To test the hypotheses, generalized linear mixed 
models  (GLM)  with  a  gaussian  error  distribution  were  fitted.  The  specific  analysis  and  model 
structure is described per theme below. 

Changes in fishing effort and catches before and after the wind farm establishment 

To assess changes in fishing effort, fish biomass and CPUE before and after the  wind farm was 
established,  three  models were formulated with  the above  response  variables in relation to  an 
interaction  of  the  period  (before  or  after  restrictions)  and  species  (sole,  dab  or  tub  gurnard) 
(models 1 to 3). This allowed to test whether effort, biomass or CPUE changed significantly since 
the enforcement of the wind farm, and whether this specific to a particular species or not. 

Fishing effort (hours) ~ Period (before vs after) * species 
Fishing biomass (kg) ~ Period (before vs after) * species 

• 
• 
•  Catch per unit of effort (kg/hour) ~ Period (before vs after) * species 

(mod. 1) 
(mod. 2) 
(mod. 3) 

Increasing biomass closer to the wind farm, since establishment? 

To assess if any spillover effects are present, it was tested whether there is gradient of biomass 
or  abundance  that  starts  at  the  boundary  and  decreases  with  increasing  distance  from  the 
boundary of the wind farm zone. To prevent that this is a coincidental natural spatial pattern of 
the  species  to  occur,  it  would  be  conclusive  if  this  effect  gets  stronger  with  time  since 
establishment of the wind farm. We therefore tested CPUE (as this already accounts for effort) in 
relation to an interaction of years since establishment, distance to the BOWFZ, and species, as 
the effects might be specific per species (model 4). 

• 

biomass  (only  after)  per  0.05  c-square  per  year  ~  Distance  from  BOWFZ  *  years  since 
establishment of the MPA * species 

(mod. 4) 

Software 

Analyses were carried out in R (R version 3.6.3, R Core Team, 2020 & R studio version 1.3.959 
(RStudio Team, 2020). The data processing used the VMStools R-package (Hintzen et al., 2012) 
and all its dependencies.  

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5  RESULTS 

5.1  Qualitative approach to stakeholders of the BOWFZ 

The survey was filled in by a policy officer in fisheries at the ministry of agriculture, nature and 
food  quality  (LNV),  and  a  sea  fisheries  employee  at  the  government  service  for  entrepreneurs 
(RVO).  

The  policy  officer  asserts  that  BOWFZ  does  not  qualify  as  a  true  MPA.  However,  due  to  the 
prohibition of active fisheries like bottom trawling in the area, the circumstances are similar. Since 
the commencement of the wind park construction in 2020, fishing activities have been restricted. 
This  region  lacks  a  formal  management  plan,  and  consequently,  spillover  is  not  part  of  any 
conservation objectives. Fishing primarily occurs outside this area. Currently, there are  limited 
experiments  with  passive  fishing  techniques  within  the  zone,  which  might  become  more 
conventional in the future. Neither of the two respondents has reported any notable changes in 
fish abundance, biomass, species composition, or catches. Moreover, it is doubtful whether the 
wind farm can substantially benefit overexploited fish populations; other measures, such as effort 
limitations, would likely be more effective. 

5.2  Changes in fishing effort and catches  in the study area before and after 

the wind farm establishment 

We assessed whether there was a change in fishing effort in the study area before and after the 
BOWFZ was established, and whether this was specific for the different species that were studied. 
We tested predictor variables to fishing effort in days per year per c-square. The model including 
an interaction between the period  (before or after  the establishment) and the  species was not 
significant (p=0.645), meaning that there was no difference in fishing effort before or after the 
establishment for any of the species specifically. When the variables were analysed as separate 
predictors, the model significantly diverged from the control model (p<0.001), meaning that we 
can now interpret the predictor variables one by one. Whether it was the period before or after 
the  establishment  significantly  influenced  total  fishing  effort  in  the  area  (estimateafter=-0.843, 
p<0.001). Effort also significantly differed for species in general, where there was less effort for 
the  species  tub  gurnard  in  particular  (estimate  =-0.704,  p<0.001).  An  overview  of  the  model 
effects is shown in Table 2.  

Table 2: Model 1 – Fishing effort and predictor variables. Estimates (coefficient) and p-
values for predictor variables (p variable) and their sub-variables (p sub-variable). P 
values are not shown for the intercept and lower levels if an interaction is significant 
due to limited interpretative value. The model formula is specified below: 

Model 1: Fishing effort (days) ~ Period (before vs after) + species  
This model is significant (p<0.001) 

p 
variable 

sub-
variable 

coefficient  p sub-variable 

Intercept 

Period 

< 0.001  Period: after 

Species 

< 0.001  Species: GUU 

Species: SOL 

7.586 

-0.843 

-0.704 

-0.997 

- 

< 0.001 

< 0.001 

0.948 

Potential changes in biomass were assessed similarly. Biomass is represented as the catch in kg 
per year per 0.05 degree c-square. Again, the interaction between period and species was not 
significant, leaving us with a model assessing period and species separately. This time, there was 
no significant difference  before and after  establishment. However, there were significantly less 
catches for both tub gurnard and sole compared to mullet (estimate GUU = -0.704, SOL =-0.997, 
p<0.001). An overview of the model effects is shown in Table 3. 

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Table 3: Model 2 – Fish biomass and predictor variables. Estimates (coefficient) and p-
values for predictor variables (p variable) and their sub-variables (p sub-variable). P 
values are not shown for the intercept and lower levels if an interaction is significant 
due to limited interpretative value. The model formula is specified below: 

Model 2: Fishing biomass (kg) ~ Period (before vs after) + species  
This model is significant (p<0.001) 

p 
variable 

sub-
variable 

coefficient  p sub-variable 

Intercept 

Period 

0.326  Period: after 

Species 

< 0.001  Species: GUU 

Species: SOL 

7.586 

-0.843 

-0.704 

-0.997 

- 

0.326 

< 0.001 

< 0.001 

Lastly, the change in CPUE was tested to the same predictor variable. The response variable here 
was catch in mean kg per day for every year per 0.05 degree c-square. This time, the interaction 
between  period  and  species  was  significant,  where  CPUE  was  lower  in  the  period  after 
establishment, but more so for sole, and less for tub gurnard. An overview of the model effects 
is shown in Table 4. 

Table 4: Model 3 – CPUE and predictor variables. Estimates (coefficient) and p-values 
for predictor variables (p variable) and their sub-variables (p sub-variable). P values 
are not shown for the intercept and lower levels if an interaction is significant due to 
limited interpretative value. The model formula is specified below: 

Model 3: Catch per unit of effort (kg/day) ~ Period (before vs after) * species 
This model is significant (p<0.001) 

p 
variable 

sub-variable 

coefficient  p sub-

variable 

Intercept 

Period 

Species 

Period: after 

   Species: GUU 

Species: SOL 

Species 
* Period 

0.026  Species: GUU 

Species: SOL 

58.734 

-0.914 

1.118 

8.981 

1.127 

-0.923 

- 

0.087 

0.028 

< 0.001 

0.108 

0.283 

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Table  5:  Fish  Catches,  effort,  and  mean  CPUE  for  the  years  2017–2019  (before 
establishment)  and  2020-2022  (after  establishment)  inside  the  wind  farm  zone  (in) 
and  in  the  area  surrounding  area  within  a  25  km  radius  (out)  for  the  species  Tub 
Gurnard (top), Common Dab (middle), and Sole (bottom).  

Year  MPA  Total KG 

b
a
D
n
o
m
m
o
C

)
B
A
D
(

2017 
2018 
2019 
2020 
2021 
2022 

e
r
o
f
e
b

r
e
t
f
a

8 543.8 
6 827.4 
3 988.6 
107.7 
9.4 
10.4 

in 
Total effort 
(h) 

Out 

Total effort 
(h) 

Mean 
CPUE 
(kg/h) 

Total KG 

147.2  141 302.8 
174.3  133 316.0 
71.1  118 624.6 
86 305.8 
67 765.4 
59 156.1 

1.4 
0.7 
1.9 

2 017.6 
1 954.9 
1 782.9 
1 721.9 
1 515.8 
1 393.6 

58.6 
58.3 
59.2 
59.7 
50.6 
50.9 

Year  MPA  Total KG 

d
r
a
n
r
u
G
b
u
T

)
U
U
G
(

2017 
2018 
2019 
2020 
2021 
2022 

e
r
o
f
e
b

r
e
t
f
a

19 151.7 
6 881.9 
2 587.2 
43.7 
34.7 
65.1 

in 
Total effort 
(h) 

135.7 
145.1 
56.3 
1.2 
0.7 
1.8 

Total KG 

94 299.5 
74 247.2 
52 798.6 
59 471.6 
40 084.7 
52 082.9 

out 

Total effort 
(h) 

Mean 
CPUE 
(kg/h) 

1 491.8 
1 458.4 
1 286.6 
1 099.6 
959.9 
926.7 

91.4 
59.3 
46 
77.4 
53.8 
71.5 

Year  MPA  Total KG 

in 
Total effort 
(h) 

Total KG 

out 

Total effort 
(h) 

Mean 
CPUE 
(kg/h) 

l

e
o
S

)
L
O
S
(

2017 
2018 
2019 
2020 
2021 

2022 

  113 414.1 
e
r
o
104 089.5 
f
e
b
41 586.8 
496.6 
387.5 

r
e
t
f
a

146.8  950 810.4 
179.6  803 142.0 
77.3  663 679.7 
1.4  577 302.0 
0.7  515 274.3 

1 790.9 
1 971.5 
1 861.9 
1 748.9 
1 599.3 

988.2 

2.0  344 890.9 

1 355.8 

638 
515 
428 
449 
468 

419 

Increasing biomass since establishment of wind farm? 

We assessed whether  there was an increasing  trend  in biomass for the focal species since  the 
date of establishment, and whether this was strongest near the wind farm. We will therefore focus 
on CPUE, as that takes into account changes in effort. We tested CPUE to a three-way interaction 
from  years  since  establishment,  distance  to  the  border  of  the  BOWFZ  and  species.  As  CPUE 
estimates are aggregated per year, we counted time since establishment per year as well. This 
model with the three way interaction was significant (p <0.001). There was a negative effect of 
years since establishment, meaning CPUE decreased with the years. This effect was strongest for 
the common dab. For GUU and SOL, CPUE seems slightly higher near the borders of the BOWFZ 
in later years, but the size of the effect seems negligible (estimate GUU =  -0.003 and SOL =-
0.005, p=0.015). An overview of the model effects is shown in Table 6. The changes in biomass 
and CPUE after establishment of the BOWFZ are visualized in Figure 3 and 4. 

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Table 6: Model 5 - Biomass and predictor variables: estimates (coefficient) and p-values 
for predictor variables (p variable) and their sub-variables (p sub-variable). P values 
are not shown for the intercept and lower levels if an interaction is significant due to 
limited interpretative value. The model formula is specified below: 

Model 5: CPUE ~ years since establishment (data only after) * Distance to wind farm zone + 
species 
This model is significant (p<0.001) 

p variable  sub-variable 

coefficient 

Intercept 

Years established 

Species 

Distance to MPA 

Years * Species 

Years * Distance to MPA 

Distance * Species 

species: GUU 

Species: SOL 

Species: GUU 

Species: SOL 

Species: GUU 

Species: SOL 

Years * Distance * 
Species  

0.015 

Species: GUU 

Species: SOL 

56.55 

-9.12 

-76.573 

357.374 

0.000 

43.665 

74.152 

0.000 

0.005 

0.004 

-0.003 

-0.005 

p sub-
variable 
0.282 

0.701 

0.304 

0.000 

0.907 

0.196 

0.027 

0.815 

0.189 

0.376 

0.163 

0.004 

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Figure 3. Biomass change (%) in the Borssele offshore wind farm zone (BOWFZ). This map displays the research area, with cells color-coded to 
represent the change in biomass percentage after the establishment of the BOWFZ. 

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Figure 4: CPUE change (kg/day) in BOWFZ. This map displays the research area, with cells color-coded to represent the change in CPUE (the 
difference in mean CPUE per year) after establishment of the BOWFZ. 

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6  DISCUSSION 

An assessment was made regarding whether there were changes in total fishing effort, total catch 
biomass, and CPUE following the establishment of the  BOWFZ. It was observed that fishing 
effort  significantly  decreased  in  the  area  encompassing  the  BOWFZ  after  its 
establishment. This reduction in fishing effort was consistent across the three studied species, 
with no species showing a stronger effect. Although the quantity of fish caught did not exhibit 
significant  differences  before  and  after  establishment,  there  were,  non-surprisingly, 
significant  differences  in  biomass  caught  between  species.  Turning  our  attention  to  CPUE,  a 
significant interaction between the time period  before and after establishment and species was 
identified.  Upon  closer  examination,  it  was  found  that  CPUE  decreased  after  the  BOWFZ 
establishment  for  sole  (SOL)  and  to  a  lesser  extent  for  common  dab  (DAB),  but  this 
trend  was  not  evident  for  tub  gurnard  (GUU).  It appears that, in  general, the  later  years 
exhibited lower levels of productivity. 

With  a  clearer  understanding  of  what  happened  to  the  fish  before  and  after  the  BOWFZ 
establishment,  the  analysis  progressed  to  test  hypotheses  specific  to  spillover.  An  assessment 
was  conducted  to  determine  whether  there  was  an  increasing  trend  in  biomass  for  the  focal 
species  since  the  BOWFZ  establishment,  taking  into  account  the  distance  to  the  BOWFZ.  The 
combination of the variables ‘years since the establishment of the BOWFZ’, ‘distance to the zone’, 
and ‘species’ significantly influenced CPUE. However, there was a negative effect associated with 
the  years  since  establishment,  indicating  a  decrease  in  CPUE  over  time.  This  effect  was  most 
pronounced for common dab. While tub gurnard and sole did exhibit slightly higher CPUE 
near the borders of the BOWFZ in later years, the magnitude of this effect was deemed 
meaningless  from  a  biological  perspective.  Consequently,  no  discernible  indicators 
were found to support the conclusion of spillover. 

The quantitative results and the insights gathered from the questionnaires align in their 
scepticism  about  the  BOWFZ's  potential  as  a  true  MPA  with  substantial  benefits  for 
overexploited  fish  populations.  Both  sources  indicate  that  fishing  activities  have  been 
restricted, but neither has reported changes in fish abundance, biomass, species composition, or 
catches within the area. Moreover, both suggest that other measures, such as effort limitations, 
would  likely  be  more  effective  in  addressing  overexploitation  concerns.  This  consensus 
underscores the importance of considering a combination of management strategies to achieve 
conservation objectives effectively. 

It  is  reasonable  to  consider  that  the  absence  of  evident  spillover  effects  in  this  case 
study may be attributed to the MPA's relatively recent establishment (Friedlander et al., 
2017), which is a common occurrence in marine conservation. It would be valuable to conduct 
ongoing monitoring and research over an extended duration, and explore non-linear responses of 
the  species  population  in  response  to  the  WFZ  establishment  (Babcock  et  al.,  2010).  As  fish 
populations  within  the  BOWFZ  gradually  recover,  there  is  the  potential  for  them  to 
eventually spillover into the surrounding areas. Furthermore, it could be insightful to 
explore  the  dynamics  of  less  mobile  species  in  this  context,  particularly  given  the 
relatively confined research area (Di Lorenzo et al., 2020). One limitation of this study is that 
the  baseline  data  are  from  years  when  the  construction  of  the  WFZ  had  already  begun.  A 
consequence  of  this  could  be  that  the  data  therefore  represents  a  disturbed  spatial  temporal 
distribution of fish species. Having this as the reference frame for the current spatial temporal 
distribution of fish species could lead to faulty interpretation of what happened to the species long 
term. However, an underestimation of initial biomass could more easily result in the observation 
of ‘spillover-like effects’, which is not what we found in this study. Lastly, the proximity of the 
Belgian  wind  farm  area  adjacent  to  our  study  site  might  further  complicate  the  pattern  of 
population recovery or spillover in space and time. 

7  CONCLUSIONS 

In the research area, a reduction in fishing effort for all three studied species (sole, common dab, 
and  tub  gurnard)  was  observed  after  the  establishment  of  the  BOWFZ.  Additionally,  CPUE 
decreased for two out of three species (sole and common dab). Two indicators of spillover were 
tested: an increasing trend in biomass towards the windfarm zone border and increasing biomass 
surrounding the BOWFZ over time since establishment of the BOWFZ. Neither indicator yielded 
significant or biologically meaningful findings in this study. The absence of visible spillover effects 
might be attributed to the recent establishment of the BOWFZ. Further exploration of dynamics 
in other species within the confined research area may offer additional insights. 

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8  REFERENCES 

Abesamis,  R.  A.,  &  Russ,  G.  R.  (2005).  Density‐dependent  spillover  from  a  marine  reserve:  long‐term 

evidence. Ecological applications, 15(5), 1798-1812. 

Babcock,  R.  C.,  Shears,  N.  T.,  Alcala,  A.  C.,  Barrett,  N.  S.,  Edgar,  G.  J.,  Lafferty,  K.  D.,  ...  &  Russ,  G.  R. 
(2010). Decadal trends in marine reserves reveal differential rates of change in direct and indirect effects. 
Proceedings of the National Academy of Sciences, 107(43), 18256-18261. 

Bennema, F. P., & Rijnsdorp, A. D. (2015). Fish abundance, fisheries, fish trade and consumption in sixteenth-

century Netherlands as described by Adriaen Coenen. Fisheries research, 161, 384-399. 

Brasseur, S., Aarts, G., & Schop, J. (2022). Measurement of effects of piledriving in the Borssele wind farm 
zone on the seals in the Dutch Delta area: Changes in dive behaviour, haul-out and stranding of harbour 
and grey seals (No. C055/22). Wageningen Marine Research. 

Di  Lorenzo, M., Guidetti,  P.,  Di Franco, A.,  Calò, A.,  & Claudet,  J.  (2020).  Assessing  spillover  from  marine 

protected areas and its drivers: A meta‐analytical approach. Fish and Fisheries, 21(5), 906-915. 

Eigaard,  O.  R.,  Bastardie,  F.,  Hintzen,  N.  T.,  Buhl-Mortensen,  L.,  Buhl-Mortensen,  P.,  Catarino,  R.,  ...  & 
Rijnsdorp, A. D. (2017). The footprint of bottom trawling in European waters: distribution, intensity, and 
seabed integrity. ICES Journal of Marine Science, 74(3), 847-865. 

Friedlander, A. M., Golbuu, Y., Ballesteros, E., Caselle, J. E., Gouezo, M., Olsudong, D., & Sala, E. (2017). 
Size,  age,  and  habitat  determine  effectiveness  of  Palau's  Marine  Protected  Areas.  PloS  one,  12(3), 
e0174787. 

Hintzen, N. T., Bastardie, F., Beare, D., Piet, G. J., Ulrich, C., Deporte, N., ... & Degel, H. (2012). VMStools: 
Open-source  software for  the  processing,  analysis  and visualisation  of  fisheries  logbook  and  VMS  data. 
Fisheries Research, 115, 31-43. 

The  Netherlands  enterprise  agency  (RVO)  (accessed  2023).  Map  “windfarms  in  the  Netherlands”. 

Https://offshorewind.rvo.nl/files/view/507fdd12-0b8e-438a-a969-
4002b78af692/153537645520180824_wind%20farms%20in%20the%20netherlands_eng_def.pdf 

McClanahan, T. R., & Mangi, S. (2000). Spillover of exploitable fishes from a marine park and its effect on the 

adjacent fishery. Ecological applications, 10(6), 1792-1805. 

Nooitgedagt,  J.  K.,  Nederlandse  Vissersbond.  (2021).  Partijen  zien  voorlopig  af  van  passieve  visserij  in 
Windpark  Borssele.  https://vissersbond.nl/partijen-zien-voorlopig-af-van-passieve-visserij-in-windpark-
borssele/ 

Noordzeeloket:  Borssele  wind 

farm  zone. 
use/offshore-wind-energy/free-passage-shared-use/borssele-wind-farm-zone/ 

(n.d.).  https://www.noordzeeloket.nl/en/functions-and-

RStudio  Team  (2020).  RStudio:  Integrated  Development  for  R.  RStudio,  PBC,  Boston,  MA  URL 

http://www.rstudio.com/. 

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6.  CASE STUDY REPORT: 

THE BELGIAN OFFSHORE WIND FARM ZONE 

BELGIUM – NORTH SEA 

Belgian offshore wind farm. © ILVO 

Analysis of potential spillover effects around the 
Belgian offshore wind farm zone 

Jolien Buyse & Gert Van Hoey 

Flanders Research Institute of Agriculture, Fishery and Food (ILVO) 

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TABLE OF CONTENTS 

1 
2 
3 

4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ........................................................................................... 85 
BACKGROUND ...................................................................................................... 85 
AIMS AND OBJECTIVES ......................................................................................... 88 
Fishing intensity and catches around the Belgian OWF zone .............................. 89 
3.1 
3.2 
Investigating  spillover  effects  around  two  Belgian  wind  farms  using  beam 
trawl sampling ............................................................................................ 89 

3.3  Acoustic telemetry to study spatial movements of plaice within and in relation 

to an OWF .................................................................................................. 89 
3.4  Stakeholder questionnaire ............................................................................ 89 
METHODOLOGY .................................................................................................... 90 
Fishing intensity and catches around the Belgian OWF zone .............................. 90 
4.1 
Data description .......................................................................................... 90 
Data analysis .............................................................................................. 90 
Investigating  spillover  effects  around  two  Belgian  wind  farms  using  beam 
trawl sampling within a BACI-design .............................................................. 90 
Data collection and study design ................................................................... 90 
Data analysis .............................................................................................. 91 

4.2 

4.3  Acoustic telemetry to study spatial movements of plaice within and in relation 

to an OWF .................................................................................................. 92 
Data collection ............................................................................................ 92 
Study design .............................................................................................. 92 
Data analysis .............................................................................................. 94 
4.4  Stakeholder questionnaire ............................................................................ 94 
RESULTS ............................................................................................................. 95 
Fishing intensity and catches around the Belgian OWF zone .............................. 95 
5.1 
Fishing effort and trends .............................................................................. 95 
Spatial changes in fishing effort and LPUE ...................................................... 97 
Intrusions and spatial patterns ...................................................................... 97 
Investigating  spillover  effects  around  two  Belgian  wind  farms  using  beam 
trawl sampling within a BACI-design .............................................................. 97 
Density, biomass, biodiversity and species composition at the ecosystem level

5.2 

 .................................................................................................... 98 
Density at species level ................................................................................ 98 
Size distribution .......................................................................................... 98 
Anecdotal observations ................................................................................ 98 
Longer- term observations ........................................................................... 98 
5.3  Acoustic telemetry to study spatial movements of plaice .................................. 99 
5.4  Stakeholder questionnaire .......................................................................... 102 
Windfarm effects on ecosystem and/or spillover? .......................................... 102 
OWF as a conservation or fishery management area? .................................... 103 
DISCUSSION ..................................................................................................... 104 
CONCLUSIONS ................................................................................................... 105 
REFERENCES ..................................................................................................... 106 

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LIST OF ABBREVIATIONS 

Term 

BACI 

EEZ 

Description 

Before-after control-impact 

Exclusive economic zone 

GAMM 

Generalized additive mixed model 

LPUE 

Landing per unit effort 

MPA 

NGO 

OWF 

RI 

SPL 

VMS 

Marine protected area 

Non-governmental organisation 

Offshore wind farm 

Residency index 

Scour protection layer 

Vessel monitoring system 

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1  EXECUTIVE SUMMARY  

The Belgian offshore wind farm (OWF) zone is situated in the eastern part of the Belgian Exclusive 
Economic Zone, covering a total surface area of 238 km². The construction of nine wind farms 
started in 2008, with two completed by 2011 and the remaining seven by 2020. From the start, 
the  authorities  prohibited  fisheries  activities  within  the  OWF  zone  for  safety  reasons,  and  this 
closure was gradually implemented in tandem with construction activities. This phased closure is 
evident in fisheries activities within and around  the  OWF zone,  which  is extensively  monitored 
and researched for its effects on the marine ecosystem and potential spillover effects. This case 
study outlines three distinct studies, complemented by stakeholder interviews. 

The  first  study  utilized  vessel  monitoring  system  (VMS)  and  landing  data  of  key  commercial 
species to study changes in fishing patterns and catches around the Belgian OWF zone. Results 
indicated that fishing activity at the periphery of active OWFs predominantly reflects edge effects, 
with a reduction in fishing effort  within  the  OWF concession  areas  during  turbine  construction. 
Despite small alterations in fishing patterns near operational OWFs, the impact on fishing activities 
appeared  modest,  suggesting  adaptation  to  the  new  circumstances  and  potential  attraction  of 
fishers to OWF edges. Nevertheless, the loss of 238 km² of fishing ground was acknowledged, 
and further investigation is warranted to comprehend the potential benefits of OWFs as nursery 
or feeding grounds for targeted fish species. 

The second study investigated spillover effects from two distinct OWFs (C-Power and Belwind), 
assessing  density  changes  in  fish  and  epibenthic  species  using  a  before-after  control-impact 
(BACI)  approach.  Long-term  monitoring  data  revealed  changes  in  the  occurrence  of  several 
species, particularly 'hard substrate' species expanding their range of occurrence. These changes 
were attributed to the 'refugium effect' and 'artificial reef effect' due to the presence of the OWFs. 
Notably,  the  changes  were  not  consistent  between  the  two  wind  farms,  emphasizing  the  site-
specific nature of effects and the need for caution in extrapolating findings to other OWFs. 

The  third  study  describes  an  acoustic  tagging  study  on  plaice,  focusing  on  their  presence  and 
movements  within  and  around  the  Belwind  offshore  wind  farm.  Findings  suggested  that  OWFs 
offer protection to plaice during the feeding season, primarily due to abundant food supply around 
hard substrates, potentially enhancing local fish production. However, this protection diminishes 
during spawning migrations when plaice leave the OWF, exposing them to fishing mortality. The 
study underscores the potential of OWFs as protection areas for certain species but advocates for 
larger  OWF  zones  to  effectively  mitigate  fisheries  impacts.  The  research  also  showcases  the 
successful integration  of  data from  various acoustic telemetry manufacturers and recommends 
the  inclusion  of  archival  tags  for  three-dimensional  fish  position  tracking,  supporting  further 
exploration of movement patterns, including spawning behaviours and migrations.  

The interviews revealed a lack of communication or understanding among stakeholders regarding 
OWFs and the likelihood of spillover. Fishers perceive OWFs as a significant threat to their business 
due  to  the  substantial  loss  of  fishing  grounds.  Despite  optimism  among  scientists  and  NGOs 
regarding  spillover,  fishers  remain  unconvinced  due  to  the  perceived  absence  of  scientific 
evidence. Scientists and NGOs envision the OWF zone as a potential fishery and/or conservation 
management area based on ongoing research in the Belgian OWF. 

2  BACKGROUND 

The Belgian offshore wind farm (OWF) zone is situated in the eastern part of the Belgian Exclusive 
Economic Zone (EEZ), approximately 23 km off the coast of Zeebrugge (Figure ). Covering an 
area of 238 km², this zone comprises nine distinct OWFs. The initial planning for the entire OWF 
zone  dates  back  to  2004  and  was  subsequently  incorporated  into  the  first  marine  spatial  plan 
(2014-2020). Authorities, prioritizing safety, opted to progressively exclude all fishing activities 
within the OWF zone during the construction phase. Consequently, a 500 m safety perimeter was 
enforced  once  the  wind  farm  was  operational.  The  chronological  details  of  these  closures  are 
presented  in  Table  1.  The  initial  prohibition  of  fishing  occurred  in  2008  within  a  small  area 
surrounding  six  turbines  (C-power).  Subsequently,  Belwind,  developed  after  2011,  and  the 
surrounding wind farms expanded this restricted area. Since the completion of the entire OWF 
zone in 2020, all fishing and shipping activities, with the exception of maintenance and research, 
have been strictly prohibited (Figure ) (Verlé et al., 2023). A discernible transition in the closure 
of  the  area  is  evident  in  fishery  activities  within  the  OWF  zone.  During  2010-2013,  fishing 
persisted in and around the first two operational wind farms (C-power and Belwind), with a third 

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spot (Northwind) emerging as an unfished area from 2014 to 2017. Subsequently, the remaining 
part of the zone swiftly closed for fisheries from 2017 to 2019. Since 2020, no fishing activity has 
been  observed  within  the  entire  238  km²  area  (Figure  ).  The  Dutch  beam-trawl  fleet 
predominantly operated within this region when fishing was allowed, as the Belgian beam-trawl 
fleet  was  only  an  occasional  user.  In  Belgian  waters,  the  Belgian  fishery  primarily  operates  in 
coastal waters for brown shrimp fishing, minimally impacted by the OWF zone, particularly in the 
most southern part (Norther wind farm). 

Figure 1: Position of the Belgian OWF zone and an indication of the nine different wind 
farms and their turbines. At the east side, the Dutch Borssele OWF zone is located12. 

During the initial delineation of the OWF zone, the fisheries sector was not consulted. Although a 
consultation  process  occurred  during  the  implementation  of  the  first  marine  spatial  planning 
process, it had limited influence on the location of the planned zone or the fisheries restrictions. 
While fishers and sector representatives could offer comments on the initial marine spatial plan 
during this consultation, they had little say in location decisions, as most concessions were already 
granted. The opposition to OWFs by fishers persists due to the significant loss of fishing grounds, 
and they find it challenging to compete with the energy sector or align with green energy policy 
targets. Moreover, they have minimal influence on the location choices of OWFs and have received 
limited compensation, particularly in the context of Belgian fisheries. 

12 See also Case Study on the Dutch Borssele OWF. 

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Table 1: Overview of the nine wind farms, with indication of the moment of the fishery 
closure, in relation to construction and operability timing. 

Wind farm 

C-Power phase 1 

Start of 
sustained 
fisheries 
closure 
02/08 

Comments 

Start 
construction 

First power 
generated 

6 turbines with gravity-
based foundations (+ 500 
m safety buffer) 

05/08 

01/09 

Belwind 

06/09 

C-Power phase 2 & 3 

01/11 

Both zone A and B 

09/09 

04/11 

04/13 

05/16 

07/17 

08/18 

07/19 

01/11 

09/13 

05/14 

12/17 

01/19 

05/19 

05/20 

Northwind (NW) 

Nobelwind (NB) 

Rentel (RE) 

Norther (NO) 

Northwester 2 
(NW2) 
Seamade (MM + SS) 

01/13 

02/16 

04/17 

05/18 

04/19 

06/19 

South and north of 
Belwind 

Seastar + Mermaid 
concession areas 

09/19 

11/20 

While OWFs are not designed with the explicit goal of protecting vulnerable species or habitats as 
in the case of marine protected areas (MPAs), they may inadvertently serve a protective function 
due to the absence of fishing activities within their boundaries.  In this way, the OWF has been 
considered as an ‘other effective area-based conservation measure’ (OECM). Although the extent 
and nature of this protective function from OWFs, and its potential to trigger biomass spillover to 
adjacent areas, remain largely unknown.  

The Belgian OWF zone, particularly the two earliest wind farms, C-Power and Belwind, has been 
studied extensively to explore the impact of OWFs on the biological communities within the area. 
Through a combination of basic monitoring and targeted studies, a comprehensive understanding 
has been developed regarding the effects of OWFs on various species groups. While spillover was 
not the primary focus of the basic monitoring, some targeted studies have assessed the potential 
existence  of  spillover  from  Belgian  OWFs.  The  ensuing  results,  along  with  insights  from 
stakeholder  interviews,  are  detailed  below  to  provide  an  integrated  overview  of  the  potential 
spillover dynamics from the Belgian OWF zone. 

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Figure  2:  Total  fishing  effort  in  fishing  hours  in  the  Belgian  part  of  the  North  Sea 
between  2007  and  2022  (all  gears  combined).  Data  includes  activities of  the  Belgian 
and  Dutch  fleet  (2007-2022)  as  well  as  the  German,  Danish  and  British  fleet  (2009-
2022).  France  could  not  be  included.  The  information  is  presented  on  a  1.6  x  1.6  km 
grid.  The  Flemish  Banks  is  also  represented  along  with  the  latest  areas  where  the 
enforcement of fishing measures are planned.  

3  AIMS AND OBJECTIVES 

The general aim of this case study is to describe three separate studies each focused on a specific 
topic related to spillover effects from the Belgian OWF zone. Additionally, some interviews were 
executed to gain insight into how different groups of stakeholders perceived ecological or fishery 
spillover effects from the zone. The aims, methodology and results of each study will be described 
separately, while the discussion will integrate the findings of all three studies. 

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3.1  Fishing intensity and catches around the Belgian OWF zone 

The first study investigated changes in fishing patterns and catches around the Belgian OWF zone 
using VMS and landing data of the most important commercial species in the area. This part is 
based on the report published as De Backer et al (2019). The aims of this study were:  

• 

• 

To  study  whether  or  not  the  effort,  the  landings  and  the  landings  per  unit  effort  (LPUE) 
changed over the period 2006-2017 in relation to the presence of OWFs.  

To investigate whether spatial changes in fishing activity took place due to OWFs by comparing 
the period 2006-2007 (pre-turbines) with 2016-2017 (232 operational turbines). 

3.2  Investigating spillover effects around two Belgian wind farms using beam 

trawl sampling 

The  second  study  investigated  spillover  effects  from  two  different  Belgian  OWFs  in  terms  of 
changes in fish and epibenthic communities using traditional beam trawl sampling within a BACI 
approach. This part is based on the paper published as Vandendriessche et al (2015). The aims 
of this study were: 

• 

• 

To  investigate  whether  changes  in  species  diversity,  density,  species  composition,  size 
distribution,  and  biomass  of  the  epibenthos,  demersal  fish,  and  benthopelagic  fish  species 
could be related to the presence of offshore wind farms. 

To investigate whether such changes could be attributed to the absence of fisheries activities 
and/or the presence of hard substrates within the wind farm and whether edge or spillover 
effects could be detected. 

3.3  Acoustic  telemetry  to  study  spatial  movements  of  plaice  within  and  in 

relation to an OWF 

The third study describes an acoustic  telemetry study on plaice that investigated the presence 
and movements of plaice within  and  in  relation  to the  Belwind OWF. This part is based  on  the 
manuscript published as Buyse et al. (2023). 

The aims of this study were:  

•  To assess plaice residency within the Belwind OWF.  
•  To analyse small scale movement patterns of plaice on and near the scour protection layer13 

(SPL). 

•  To examine plaice site fidelity to the OWF after their yearly spawning migrations. 

Although this study had no direct  aim  of  studying  spillover, the presence  data within the wind 
farm can give a good idea on the residency of plaice within the closed area and whether plaice 
leaves the area during the spawning season, which would indicate spillover towards fished areas.  

3.4  Stakeholder questionnaire 

The questionnaires aimed to explore the views of different types of stakeholders in terms of both 
ecological and fishery spillover from the Belgian offshore wind farm zone.  

13 A scour protection layer in the form of rocks or  mattresses are added around turbine foundations where 
currents cannot pass through to ensure the stability of the surrounding sand, as the redirected currents 
cause turbulence in the water column that could wash away the sand (Whitehouse et al., 2011). 

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4  METHODOLOGY 

4.1  Fishing intensity and catches around the Belgian OWF zone 

Data description 

The  data  for  this  study  consist  of  VMS  data  and  logbook  data  from  2006  to  2017  within  ICES 
rectangles  31F2,  31F3,  32F2,  and  32F3,  which  overlap  with  the  Belgian  OWF  zone.  VMS  is  a 
satellite-based vessel monitoring  system  that  provides data  on the location,  time,  course,  and 
speed of vessels to the fisheries authorities at regular intervals (usually every 2 hours). Logbook 
data contains information on the daily catch composition, used fishing gear, engine power and 
visited harbours. These data were obtained for both the Belgian and Dutch beam trawl fleet, which 
includes small and large beam trawls, and Dutch pulse trawlers operational since 2011. The spatial 
resolution of the  ICES rectangles was gridded at  0.05  x 0.025 decimal degrees, referred to as 
"grid  cells."  The  processed  Dutch  data  were  provided  by  Wageningen  Marine  Research,  while 
Belgian VMS and logbook data were collected by Dienst Zeevisserij (Departement Landbouw en 
Visserij; Afdeling landbouw- en visserijbeleid) and analysed by the Flanders Research Institute 
for Agricultural, Fisheries and Food (ILVO). 

Data analysis 

Data processing of both VMS and logbook data was carried out using the "vmstools" package in 
R,  and  an  extensive  quality  control  process  was  conducted,  addressing  data  consistency, 
duplication, and the selection of VMS records indicative of actual fishing activity based on speed 
(Hintzen et al., 2012). VMS and logbook data were linked based on the vessel identity and the 
timestamp, after which a spatial overlay was performed to calculate the fishing activity and catch 
per grid cell. To entangle wind farms effects from general trends in fishing activities, yearly trends 
in fishing effort, landings, and LPUE for the top 10 species of the Dutch and Belgian beam trawl 
fleets were calculated for each ICES rectangle and for plaice and sole within each OWF concession 
area using the Geofish platform. Data for operational wind farms should be interpreted as edge 
effects, rather than infringements of fishing vessels within the concession areas. Comparisons of 
fishing effort and LPUE distribution were made between the pre-OWF period (2006-2007) and the 
period with operational and under-construction OWFs (2016-2017). The analysis focused on the 
large beam trawl segment (> 221 kW), excluding the small beam trawl segment (= < 221 kW) 
that operated primarily  outside the  OWF  area  before  2009. Deviations in proportional effort or 
LPUE were calculated, indicating relative changes in 2016-2017 compared to the reference period 
of  2006-2007.  Effort  and  LPUE  values  were  expressed  as  proportions  relative  to  the  average 
values for the study area (four statistical ICES rectangles) for each grid cell, excluding the general 
temporal trend. A negative deviation indicates reduced effort or lower LPUE in 2016-2017, while 
a positive deviation indicates increased effort or higher LPUE. 

4.2  Investigating spillover effects around two Belgian wind farms using beam 

trawl sampling within a BACI-design 

Data collection and study design 

The  study  focused  on  two  wind  farms  on  the  Thorntonbank  (C-Power)  and  the  Bligh  Bank 
(Belwind), which are located in Belgian waters. The C-Power wind farm is situated 27 km from 
the coast and consists of 54 turbines, of which 48 on jacket foundations and 6 on gravity-based 
foundations, constructed at depths between 18 and 24 m. The Belwind wind farm, located about 
40 km offshore, consists of 56 turbines constructed on monopile foundations and spans depths of 
15 to 40 m. Samples were collected within the two wind farms, specifically between turbine rows 
approximately 200 m away from the nearest turbines (Figure 3). Edge stations just outside the 
wind farm concessions and reference stations away from the concessions with comparable soft 
sediments and depths were also sampled. Sampling encompassed three ecosystem components 
(epifauna, demersal fish, and benthopelagic fish) across two seasons (autumn and spring), two 
sandbanks (Thorntonbank and Bligh Bank), and two habitats (sandbanks and gullies). Ecological 
data were gathered through beam trawl samples taken at different locations and conditions. The 
Ecological  data  collection  involved  the  deployment  of  an  8-metre  beam  trawl  equipped  with  a 
shrimp net (mesh size of 22 mm).    Samples were  collected  within  the  wind farms,  specifically 

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between  turbine  rows  approximately  200  m  away  from  the  nearest  turbines  (Figure  3).  Edge 
stations just outside the wind farm concessions and reference stations away from the concessions 
with comparable soft sediments and depths were also sampled. Monitoring in this concession area 
has  been  going  on  since  2005  (Sampling  occurred  every  6  months  (February–March  and 
September–October,  from  2005-2012  for  C-Power  and  from  2008-2012  for  Belwind),  and  the 
sampling design was slightly adapted based on previous results and wind farm developments and 
accessibility.  The  data  analysis  consisted  of  a  "Before  After  Control  Impact"  (BACI)  design,  in 
which years were  nested within periods and  sites.  The expected  changes in the OWF area  are 
attributed to the artificial reef effect and the refugium effect (exclusion of fisheries).  

Figure 3: BACI sampling design showing trawl locations before and after construction 
(2012  and  afterwards)  of  both  the  Thorntonbank  and  Bligh  Bank  wind  farms,  and 
reference stations on adjoining sandbanks. Bathymetry is indicated as grayscale (white 
<5 m; light gray 5–20 m; dark gray >20 m). Inset indicates the position of the Belgian 
part of the North Sea relative to Belgium and its neighbouring countries. 

Data analysis 

To investigate wind farm and edge effects, univariate measures density (ind./1,000 m²), biomass 
(g  WW/1,000  m²),  and  diversity  (number  of  species)  were  calculated  for  each  combination  of 
factors  (season,  sandbank,  location,  ecosystem  component).  Further,  community  structure  for 
the different ecosystem components was assessed for each combination of factors. Time-evolution 
graphs were used to check for differences between treatment groups over the years (except for 
community structure). Non-parallelisms between the trend lines between control and impact areas 
was interpreted as a  sign of  an environmental  impact (Schwarz, 1998).  Statistical significance 
was  assessed  using  two-way  crossed  PERMANOVA  analyses,  employing  a  BACI  design  that 
incorporates  the  factors  BA  (before/after),  with  years  nested  in  BA,  and  site  (control/impact). 
When interaction effects were significant, pairwise tests were conducted. Community differences 
were assessed using the Bray-Curtis similarity measure, with contributions of species differences 
calculated using the SIMPER routine. Additionally, the potential influence of temporary effects was 
considered,  and  differences  between  control  and  impact  samples  within  specific  years  were 
evaluated. The statistical analyses were run in PERMANOVA for PRIMER (Anderson et al., 2007) 
PERMANOVA  and  employed  Monte-Carlo  tests  when  appropriate.  The  BACI  design  considered 

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variations  in  the  number  of  replicates  and  observations  between  pre-  and  post-construction 
periods.  

4.3  Acoustic  telemetry  to  study  spatial  movements  of  plaice  within  and  in 

relation to an OWF 

Data collection 

The study was conducted within the Belwind offshore wind farm located in the Belgian part of the 
North  Sea  (51°39′36″  N,  2°48′0″  E).  The  wind  farm  is  situated  on  the  Bligh  Bank,  a  natural 
sandbank located 40 km offshore from the Belgian coastline, at water depths ranging from 15 to 
37 m. Construction of the wind farm began in 2009, involving the installation of 55 Vestas turbines 
(3 MW) on monopile foundations with a 5 m diameter. To mitigate sand erosion, each turbine was 
equipped with a scour  protection layer  consisting of  a filter  layer  composed of pebbles and an 
armour  layer  with  a  median  rock  size  of  370  mm  and  a  density  of  2.65  ton.m-3.  The  entire 
concession  zone  with  a  500  m  safety  perimeter  was  closed  three  months  before  construction 
began,  and  adjacent  areas  were  later  closed  for  vessel  traffic  during  the  construction  of  a 
neighbouring wind farm in 2016. 

Thirty-one plaice individuals were tagged using Thelma Biotel MP9 transmitters (69 kHz) emitting 
unique acoustic signals. The transmitters were attached externally to fish using a stainless-steel 
wire  and  secured  with  heat  shrink  tubing  and  metal  crimps.  Fish  were  caught  using  hand  line 
fishing or diving, ensuring a minimum size of 29 cm. Tags were attached anterior to the dorsal 
fin. The tagging procedure took approximately three minutes per fish. Fish were released near 
their  capture  locations  after  the  procedure.  The  tagging  protocol  was  approved  by  the  ethical 
committee of ILVO. 

Study design 

Three  successive  arrays  of  VR2AR  receivers  (69  kHz,  InnovaSea  Systems  Inc.,  USA)  were 
deployed within the southern part of the Belwind OWF from May 2020 to August 2021 (Figure 4). 
These  arrays  were  designed  to  study  the  movement  patterns  and  site  fidelity  of  plaice. 
Deployment  and  retrieval  were  conducted  by  the  research  vessel  Simon  Stevin  using  tripod 
moorings. The mooring setup comprised a receiver attached to a buoy connected to a steel tripod 
and a rope. The difficulty in using tripod moorings lies in their retrieval, as windy conditions can 
cause the ropes on the tripods to break. If this happens, the frames cannot be retrieved by winch, 
but need to be located by the use of divers. However, such a setup gave much better results in 
terms of decreased background noise compared to a surface setup using chains and buoys. The 
first  array  (May  2020-October  2020)  had  18  receivers  strategically  positioned  around  three 
turbines for the calculation of fish positions, and ten additional receivers in between the turbines 
to  investigate  plaice  presence  within  the  OWF  during  the  feeding  season.  The  second  array 
(October  2020-February  2021)  included  28  receivers  used  to  study  plaice  presence  within  the 
wind farm during the spawning period. The third array (February 2021-August 2021) featured 15 
receivers for monitoring fish returns after spawning.  

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Figure 4: (A-B) location of the Belgian part of the North Sea and the Belwind offshore 
wind farm; (C-E) spatial design of the receiver arrays during the three study periods: 
May 2020–October 2020, October 2020–February 2021, and February 2021–July 2021, 
respectively. Turbine locations are indicated with white open circles, deployed receivers 
are indicated as red triangles, lost receiver indicated as a black open triangle. 

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Data analysis  

The first array's data (May 2020-October 2020) were used to study plaice residency and small-
scale  movement  patterns.  Daily  binary  presence/absence  data  were  analysed  to  assess  the 
presence of fish in the study area. Residency index (RI) was calculated for each fish. The estimated 
positions  of  tagged  fish  were  determined  using  the  YAPS  model.  Associations  with  the  scour 
protection  were  examined  by  calculating  distances  between  fish  positions  and  turbines. 
Generalized additive mixed models (GAMMs) were used to explore relationships between distance 
from  turbines  and  environmental  variables.  Light  conditions,  bottom  current  speed,  and  tide-
related  factors  were  tested  as  explanatory  variables.  Models  were  evaluated  using  root  mean 
square error (RMSE). Binary presence/absence data from all three receiver array periods (May 
2020-July 2021) were analysed to study site fidelity and long-term presence within the wind farm 
area. Extended absences during spawning followed by returns indicated fish migration and site 
fidelity. 

4.4  Stakeholder questionnaire 

A  questionnaire  was  developed  to  assess  the  perceptions  of  key  stakeholders  on  the  potential 
spillover  effects.  The  questionnaire  consisted  of  open-ended  and  closed  questions  to  elicit 
stakeholder views and experiences  on  the different  aspects of this study  (see questionnaire  in 
Annex 4). The open-ended questions aimed to capture stakeholder opinions on, for example, how 
aware the stakeholder was of the regulations and management measures. The closed questions 
were statement-based and used Likert scale answer categories (such as: Strongly agree; Agree; 
Neutral; Disagree; Strongly Disagree) for the stakeholder to choose from. 

The  questions  were  grouped  into  four  broad  categories  to  encapsulate  the  key  issues  being 
studied. These included: 

(i)  Respondent  information.  The  first  section  required  basic  information  from  the  respondent, 
including their name, institution and the type of stakeholder category they belonged to. 

(ii)  Background  information.  The  second  section  of  the  questionnaire  gathered  background 
information from the stakeholder to understand more about the respondent and their use of the 
OWF. Questions included knowledge of when the OWF was established, the type of restrictions in 
place and how long the stakeholder has been associated with the OWF either through research, 
fishing or managing it. 

(iii) Fishery impacts of OWFs. The third section explored the respondent’s perceptions of the socio-
economic  impacts  of  spillover  from  the  OWF.  Stakeholders  were  asked  to  state  whether  the 
designation of an OWF area where fishing is limited has led to an increase in revenues for fishers, 
whether the fishing community in the area feel their fisheries livelihoods are more secure after 
the  OWF  was  established,  and  the  extent  to  which  they  believe  spillover  from  the  OWF  has 
influenced the catch composition in adjacent fishing grounds. 

(iv)  OWFs  as  management  tools.  The  fourth  section  of  the  questionnaire  focused  on  the 
respondent’s  perceptions  on  whether  OWFs  are  conservation  or  fisheries  management  tools. 
Stakeholders were asked to state whether the OWF was acting as a conservation tool, a fisheries 
management tool or both. Other questions under this section required stakeholders to state their 
agreement / disagreement on  whether  the  establishment of  OWFs  is an effective conservation 
strategy to support fish populations and commercial fisheries in their area. Respondents were also 
asked to indicate what factors they thought were contributing to spillover effects. 

Four  key  stakeholder  groups  were  targeted  under  this  consultation  including  commercial  and 
recreational fishers, fisheries managers and government authorities, scientists and environmental 
non-government  organisations  (NGOs).  Therefore,  while  the  four  sections  of  the  questionnaire 
were the same, specific questions were included for each of the four respondent groups.  

For this case study, we contacted and interviewed the four key stakeholder groups. For fishers, 
we had an interview with the producer organisation (Redercentrale) and one coastal fisher. Two 
scientists,  one  of  ILVO  and  one  of  VLIZ  were  interviewed,  both  executing  research  within  the 
Belgium OWF zone on fishery effects and fish movements. From the policy department, we had 
contact with the Flemish Fishery department, responsible for fishery management and with the 

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Federal  Department  of  Environment,  responsible  for  the  management  of  nature  conservation. 
Finally, we had 5 responses to the questionnaire for this case study. 

5  RESULTS 

5.1  Fishing intensity and catches around the Belgian OWF zone 

The study investigated the fishing effort, landings of  the top 10 species, and LPUE of sole and 
plaice in relation to the OWF development in Dutch and Belgian waters from 2006 to 2017. 

Fishing effort and trends 

Dutch and Belgian beam trawls spent an average of 108,000 hours within ICES rectangles 31F2, 
31F3, 32F2, and 32F3 from 2006 to 2017. Fishing effort in the areas surrounding the OWF area 
displayed a general decreasing trend over the years. During the construction of an offshore wind 
farm, there was a noticeable drop (up to 50%) in fishing effort within its concession area (Figure 
5). After OWFs became operational, reduced fishing effort persisted in C-Power and Northwind. 
However,  in  Belwind,  the  apparent  increase  in  fishing  effort  during  the  operational  phase  was 
attributed to grid cell resolution, wherein fishing along the edges was seen as fishing within the 
wind  farm,  largely  due  to  edge  effects.  With  the  expansion  of  non-fishing  areas  due  to  OWF 
construction  (e.g.  Nobelwind),  fishing  effort  dropped  again.  For  OWFs  in  the  pre-construction 
phase (Seastar, Northwester, Mermaid), temporal variation in fishing effort was observed, with a 
decreasing trend in the later years. 

Figure 5: Spatial changes in fishing effort based on the deviation in proportional effort 
for  Dutch  and  Belgian  large  beam  trawls  in  2016-2017  compared  to  2006-2007. 

Top 10 Species Landings 

Within the four studied ICES rectangles, Dutch and Belgian beam trawlers landed an average of 
2.8 million kg of sole and 3.4 million kg of plaice, their target species. Landings  were generally 
correlated with fishing effort. Landings of dab and cod increased during the earlier years (2006-
2009), but decreased from then on. Plaice landings showed an increase from 2006-2011, followed 
by  a  decline,  while  sole  landings  were  more  erratic  over  time  with  low  values  in  2011.  Sole’s 
landings showed a clear increase (26%) after 2012, while gurnard landings were also higher in 
2015 and 2016. Landings of other species (turbot, brill, whiting, bib) remained relatively stable 
during the study period. In the OWF area, trends in total landings for the top 10 species were 
highly correlated with fishing effort, showing a drop during construction of the OWF and remaining 
lower when operational, except for Belwind. These trends represent edge effects and not actual 
fishing effort within the concession zones of the wind farms due to the low resolution of the data.  

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LPUE for sole and plaice 

LPUE for sole in the four studies ICES rectangles increased significantly (almost 50%) from 2012 
onwards, indicating higher catch rates (Figure 6). LPUE for plaice displayed more yearly variation 
and averaged 32 kg/h. LPUE of plaice followed the landing trend, increasing towards 2011 and 
decreasing  in  later  years.  LPUE  of  sole  within  concession  areas  increased  from  2012  onwards, 
unaffected by  wind  farm  presence. For  plaice, higher catch rates were  observed in wind farms 
farther offshore compared to coastal ones. The trend in LPUE of plaice within concession areas 
showed some year-to-year variation, deviating from the general trend. 

Figure  6:  Spatial  changes  in  LPUE  of  sole  (top)  and  plaice  (bottom)  based  on  the 
deviation in proportional LPUE for Dutch and Belgian large beam trawls in 2016-2017 
compared to 2006-2007. 

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Spatial changes in fishing effort and LPUE 

Spatially, proportional fishing effort decreased around operational wind farms, with a general shift 
towards more offshore fishing activity. Fishing effort in wind farms further offshore (e.g., Belwind, 
Nobelwind) increased slightly, suggesting attraction to edges. Proportional LPUE changes did not 
clearly  indicate  a  wind  farm  effect  on  sole.  However,  for  plaice,  a  substantial  increase  in 
proportional LPUE was observed in certain wind farm areas, deviating from the general trend. 

Intrusions and spatial patterns 

The study also investigated fishing vessel intrusions within operational concession areas, which 
ranged from 0-17 per year per wind farm. Intrusions increased in later years, potentially due to 
improved detection tools. 

Overall, the study demonstrated  dynamic interactions between fishing effort, species landings, 
and LPUE in relation to OWF construction and operation, suggesting complex spatial and temporal 
patterns influenced by various factors, including fishing restrictions and fish behaviour. 

5.2  Investigating spillover effects around two Belgian wind farms using beam 

trawl sampling within a BACI-design 

The study examined the effects of edge and wind farm presence on various ecological components 
in different seasons and habitats, as summarized in Table 2.  

Table 2: Summary of the statistical results for the Thornton bank and Bligh Bank. Bold 
text indicates significant effects (p < 0.05) of the BACI interaction term. Text in italics 
indicates significant control impact (CI) effects within specific years (but BACI effect 
not significant). Arrows indicate increase  or decrease.  Source: Vandendriessche  et al 
(2015).   

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Density, biomass, biodiversity and species composition at the ecosystem level 

A significant effect on density was observed for demersal fish at the Thorntonbank top samples 
in autumn when years were nested within the Before-After treatment. However, pairwise tests 
didn't reveal specific differences within years. Biomass effects were seen at the Bligh Bank top in 
both  autumn  and  spring,  with  increases  in  biomass  after  wind  farm  construction.  Higher 
epibenthos  biomass  was  observed  at  the  Thorntonbank  top  stations  in  certain  years,  with 
significant differences found in 2009. A biomass effect was noted at the Thorntonbank edge in 
spring, but pairwise tests were not significant. Wind farm effects were detected for the number 
of species of demersal fish in the Thorntonbank samples in autumn 2008, though based on limited 
data. Differences in species composition were only observed for demersal fish at the Bligh Bank 
gullies in autumn 2012, attributed to different proportions of certain species. 

Density at species level 

Significant edge effects were observed for sole and dab at the Bligh Bank in spring 2012, with 
higher densities in edge stations. Significant BACI wind farm effects were observed for sea stars 
and sole at the Bligh Bank top in spring, mainly due to recruitment of small individuals. Effects 
within  specific  years  were  seen  for  various  species  including  sandeel,  sea  stars,  sole,  dab, 
ophiuroids, and urchins, with varying impacts. 

Size distribution 

Significant  mean  length  differences  were  found  for  whiting  concerning  edge  effects  at  the 
Thorntonbank in spring. Effects within specific years were observed for dab and other species, 
with variations in size classes. 

Anecdotal observations 

Some observations were made that were not statistically analysed but worth noting. For instance, 
plaice density increased over  the  years, but in 2012,  a decrease was observed in impact gully 
stations. Similar observations were made for turbot and sandeel, with episodic increases at wind 
farms. Lobsters, typically absent in monitoring surveys, were noted within the wind farm area in 
autumn 2012. 

Longer- term observations 

The later monitoring revealed some secondary effects with an expansion of the OWF effect beyond 
the immediate vicinity of the turbine on two fronts: (1) an expansion of the reef effect, and (2) 
signals of a refugium effect (De Backer et al., 2019). Expansion of the reef effect is suggested 
through the appearance of an increased number of hard substrate-associated species like long-
clawed  porcelain  crab  (Pisidia  longicornis),  edible  crab  (Cancer  pagurus)  and  seabass 
(Dicentrarchus  labrax)  in  the  soft  sediment  trawls.  However,  the  clearest  indication  for  reef 
expansion  was  the  significantly  increased  abundances  of  blue  mussel  (Mytilus  edulis)  and 
anemones (Anthozoa sp.), two species dominating the epifouling communities on the turbines. 
Slightly, but significantly, increased fish densities of some common soft sediment-associated fish 
species  (common  dragonet,  Callionymus  lyra;  solenette,  Buglossidium  luteum;  lesser  weever, 
Echiichthys vipera; and plaice, Pleuronectes platessa) inside the C-Power wind farm compared to 
the outside reference area seem to be the first signs of a refugium effect, probably related to a 
combination  of  fisheries  exclusion  and  increased  food  availability  (Figure  7).  More  pronounced 
effects were found for C-Power than for the more offshore Belwind OWF, stressing that effects 
might be site-specific and that extrapolation of these findings to other OWFs should be considered 
with care. 

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Figure 7: (Left) Time series plots of densities (individuals per 1000 m2). (Right) Mean 
density  values  (±  SD)  for  fish  species  in  C-Power  for  which  a  wind  farm  effect  was 
detected in the baseline (2004-2010) and operational years (2014-2019). Construction 
of the second phase of C-Power was in 2011 indicated with a grey rectangle. 

In summary, the study indicated various ecological responses to the presence of wind farms, with 
effects observed in density, biomass, species composition and size distribution. However, most 
wind farm effects were not significant and no substantial edge effects could be identified, which 
would  indicate  the  presence  of  spillover.  The  complexity  and  inconsistency  of  these  effects 
suggests the need for continued monitoring and investigation. 

5.3  Acoustic telemetry to study spatial movements of plaice 

In the initial study phase (May 2020-October 2020) lasting 150 days, we tagged and monitored 
29  fish.  Their  tracking  durations  varied  from  1  to  131  days.  Subsequently,  during  the  second 
study period, only two fish were tagged (totalling 31 tagged fish) (Figure 8). However, their data 
were omitted from the residency calculations due to the change in the study design after the first 
period. Most fish exhibited prolonged presence within the study area during summer and autumn, 
with the majority still detected at the study's end. However, three fish were briefly detected after 
release but not afterward. One fish was captured by a commercial vessel in April 2021 without 
specific identification.  

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Figure  8:  Presence  per  day  of  the  31  tagged  plaice  individuals  over  all  study  periods 
(15/05/2020-11/07/2021) in the Belwind OWF. Red squares indicate the tagging and 
release date of the fish. The red vertical lines show the change in receiver array design: 
study period 1: 15/05/2020-11/10/2020; period 2: 14/10/2020-22/02/2021; period 
3: 25/02/2021-11/07/2021. The grey box represents the yearly spawning period for 
plaice  in  the  southern  North  Sea  (December-March).  A  fish  was  considered  to  be 
present in the study area if it was at least detected two times on that particular day. 

For 24 fish detected for at least 20 days, their residency ranged from 0.09 to 1, averaging 0.78 
± 0.29 SD (Table 3). Around turbines B9, D9, and C8 in Belwind, 172,285 estimated fish positions 
were withheld for analysis. These positions had an average standard deviation of 5.1 m for the x-
coordinate and 4.9 m for the y-coordinate. 

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Table  3:  Residency  index  (RI) for  the  29 fish  that  were  tagged  during  the first  study 
period. Days at large and last detections in this table are only given for the first study 
period (15/05/2020–11/10/2020, max. 150 days). As can be seen in Figure 8, several 
of these fish were still detected in the second and third study period. 

Fish ID 

Release date 

Last detection 

Days detected 

Days at large 

RI 

9246 

9247 

9248 

9249 

9250 

9251 

9255 

9256 

9258 

9259 

9260 

9263 

9264 

9265 

9268 

9269 

9272 

9273 

9274 

9275 

9276 

9277 

9279 

9280 

9281 

9282 

9283 

9284 

9285 

15/05/2020 

28/09/2020 

15/05/2020 

27/07/2020 

19/06/2020 

11/10/2020 

15/09/2020 

07/10/2020 

17/06/2020 

11/10/2020 

19/06/2020 

11/10/2020 

14/07/2020 

11/10/2020 

14/07/2020 

25/09/2020 

15/09/2020 

19/09/2020 

14/08/2020 

11/10/2020 

19/06/2020 

11/10/2020 

17/06/2020 

11/10/2020 

16/06/2020 

10/10/2020 

17/06/2020 

21/09/2020 

10/09/2020 

14/09/2020 

15/09/2020 

11/10/2020 

17/06/2020 

10/10/2020 

17/06/2020 

31/07/2020 

16/06/2020 

11/10/2020 

15/09/2020 

09/10/2020 

16/06/2020 

16/06/2020 

17/06/2020 

11/10/2020 

13/08/2020 

06/10/2020 

10/09/2020 

11/10/2020 

17/06/2020 

29/09/2020 

19/06/2020 

11/10/2020 

17/06/2020 

12/08/2020 

14/07/2020 

11/10/2020 

17/06/2020 

06/08/2020 

131 

61 

109 

15 

115 

115 

85 

72 

5 

59 

115 

76 

71 

97 

1 

21 

103 

45 

115 

3 

1 

80 

16 

31 

103 

115 

5 

69 

11 

137 

0.96 

74 

0.82 

115 

0.95 

23 

0.65 

117 

0.98 

115 

1.00 

90 

74 

0.94 

0.97 

5 

1.00 

59 

1.00 

115 

1.00 

117 

0.65 

117 

0.61 

97 

1.00 

5 

0.20 

27 

0.78 

116 

0.89 

45 

1.00 

118 

0.97 

25 

0.12 

1 

1.00 

117 

0.68 

55 

32 

0.29 

0.97 

105 

0.98 

115 

1.00 

57 

90 

51 

0.09 

0.77 

0.22 

Plaice individuals were observed approximately 92 ± 48 m from the turbines, most frequently on 
the sand directly surrounding the SPL within about 25 meters from the turbine (Figure 9). Another 
smaller peak of detections occurred around 90 meters from the turbines. Fish-turbine distance 
was best described by a GAMM, revealing a diurnal pattern. Fish were closer to turbines during 
daylight hours compared to nighttime. During the day, fish were primarily detected on or near 
the SPL, while at night, higher densities were found on the surrounding sandy area. 

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Figure 9: All estimated positions for the 21 fish that were present at least 20 days during 
the first study period (May 2020-October 2020). White dots represent the turbines at 
true scale (diameter = 5 m). White circles indicate a distance of 150 m from the turbine 
(distance at which the receivers were positioned around turbines B9, C8 and D9). Each 
colour represents the positions of a different fish. 

Out of 31 tagged fish, eleven were detected again after a year, with seven fish remaining within 
the study area until the final two weeks. Fewer detections occurred during the winter months. 
Some fish exhibited absence for consecutive months, coinciding with plaice spawning (December-
March), followed by their return during spring. For instance, fish 9277 was absent for over 111 
days,  reappearing  twice  on  5/02/21  at  another  receiver  station  outside  the  OWF  area,  then 
returning to Belwind OWF until the study's conclusion on 17/07/21. 

5.4  Stakeholder questionnaire 

The  main  observation  is  that  there  is  a  lack  of  communication  or  understanding  between  the 
stakeholders  on  OWFs  and  the  likelihood  of  spillover.  For  fishers,  OWFs  are  perceived  a  large 
threat  to  their business,  as they lose  a lot of  fishing  grounds.  And due to the lack of  scientific 
evidence,  they  are  not  convinced  yet  of  potential  spillover  effects.  The  scientists  and  NGO 
representative, who are familiar with the research in the Belgian OWF zone, were more optimistic 
on  spillover  effects  and  see  possibilities  of  an  OWF  zone  as  a  fishery  and/or  conservation 
management area. 

Windfarm effects on ecosystem and/or spillover? 

A coastal fisherman and a fishery producer organisation were interviewed. The fishery consists of 
beam trawling and  mainly targets  sole, plaice,  and brown  shrimp, which  are landed in Belgian 
ports. They are not allowed to fish within the OWF zone and are well aware of it. Before, there 
was  only  sporadic  active  in  the  area  of  the  Belgium  OWF  zone,  more  specific  at  the  southern 
border (but not in). During the interview, also some observations were mentioned, as in the area 
of the cable corridor, a decline in brown shrimp presence was precepted and at an OWF (Thames 
estuary), the disappearance of ray in the gully system. It is anecdotal information, but it illustrates 
that they are no sure of the effects that OWFs has on the marine ecosystem. At the other side, 

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the fisher hopes that spillover will occur, but there is no evidence yet. He wants to believe in it, 
so that there is some positive effect possible (at least for a few species), but  he is very unsure 
for the moment and not aware of any positive signal. 

According to fishers, there was no apparent changes due to the wind farm. The wind farm seems 
to have  no  economic  advantages for  the  fisherman and  catches are  not higher, no increase in 
revenue or number of fishers. This is also confirmed by the study on the fishery activity within 
the Belgian part of the North Sea (Verlé et al., 2023) and the scientists feedback. At the fishery 
policy department and producer organisation, they claim that the abundance of (flatfish) species 
have  dropped  within  the  wind  farm,  based  on  feedback  they  received  from  the  sector.  This  is 
related to OWFs in general and was not specified for Belgium OWF zone. 

The scientists, doing research in the area are observing effects, but are not yet sure of possible 
spillover.  The  biodiversity  present  changes  (harder  substrate  associated  species)  as  does  the 
structural complexity of the seabed due to the artificial structures implemented. In the OWF zone, 
they found evidence of the presence of an artificial reef effect around the turbine foundations and 
scour protection. Their monitoring campaign also showed that the artificial reef effect extended 
to the soft sediment in between the turbines, resulting in higher densities of typical sessile fauna 
(e.g. mussels, anemones). They also found differences in diet, abundance increase and a change 
of habitat use of plaice (Pleuronectes platessa) within the OWF zone compared to outside. Plaice 
was found to actively use the scour protection for feeding during the day. They moved closer to 
the hard substrate during the day when feeding and moved further away during the night, possibly 
to rest in the surrounding sand. So, some species are becoming resident (or are visiting the area 
more  frequently)  since  the  implementation  of  the  OWF,  again  associated  to  the  artificial 
structures. The sea-bottom habitat differs also clear from the outside area, which has less species 
and structural habitat complexity. Scientists indicated that spillover can occur (likely), but that 
this  spillover  is  not  quantified  yet.  The  studies  show  that  there  is  a  clear  attraction  of  certain 
species, but if this led to increased biomass production for those species is still unclear. 

The NGO is well aware of the OWF research, and their view is similar as the scientists. They are 
communicating that it will deliver healthy populations and habitats in the long run, which benefit 
fisheries. However, local fishers do not ‘believe’ in the spillover effect and only see economic loss 
in closing areas. In addition, they do not ‘believe’ that our North sea nature is in a bad condition, 
so  they  don’t  see  the  benefits  in  the  long  run  from  securing  habitats  and  populations.  In  the 
questionnaire, the’ NGO was the only respondent that perceives an economic gain for the fishery.  

OWF as a conservation or fishery management area? 

The fishery policy officer thinks that because in the wind farm no fishing or other activities are 
allowed,  it  could  be  seen  as  a  conservation  tool,  but  ideally  if  fishing  activity  is  balanced  and 
adapted, it should be possible to fish even within the OWF. The scientists think that the OWF zone 
has the opportunity to act as a fisheries management tool, specifically related to fisheries-induced 
selection effects for commercial species. However, this has not been quantified yet. We don't think 
it can act as a conservation tool, because no conservation targets are linked to the establishment 
of the area. Acting as fishery management tool, because the species have a place where they can 
grow  to  adulthood  without  the  risk  of  being  fished  away,  benefitting  the  species  and  the 
population.  It  is  also  a  kind  of  conservation  tool,  as  conservation  and  fisheries  management 
always go hand in hand. There is no fishery without healthy populations. 

The NGO representative thinks along the same line, and stresses that for Belgium, it can be a 
conservation tool in the first place, because our habitats (mainly gravel beds) are in such poor 
condition and OWFs can help to restore those habitats. In the long run, it will also have a positive 
effect  on  fisheries,  because  it  keeps  populations  and  habitats  healthy.  It  could  be  useful  to 
determine  if  spillover  effects  occur  and  if  it  helps  fishers  to  compensate  the  economic  loss  of 
closing off some areas. 

The  fisherman  hopes  that  OWFs  can  be  used  as  a  fisheries  management  tool,  but  he  is  very 
uncertain. He is also wondering if the OWFs are acting as a blockage for the migration of certain 
species. For example, sole become more and more surrounded by OWF areas in Belgian waters, 
so the migration of sole might be blocked. There is no tool for the moment, as long as there is no 
scientific evidence, to prove the advantages of OWFs and MPAs in terms of spillover. Nowadays, 
the  fishery  sector  is  frequently  confronted  with  closures,  which  leads  to  high  losses  of  fishing 
grounds  and  makes  their  future  uncertain.  In  this  way,  the  balance  with  food  provision  is  not 
ensured, which creates more uncertainty for the fishery business. Fishers also believe that wind 

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farms have a more negative impact on the ecosystem and their fishing activities than the regular 
MPA management. So, OWFs might have a positive effect on fisheries, but as long as there is not 
enough  scientific  evidence,  the  sector  remains  sceptical.  Furthermore,  fishers,  together  with 
fishery producer organisations and their management authorities, are not (or poorly) involved in 
any decisions related to the designation of OWF areas or measures taken within their boundaries, 
which leads to increased tensions between the fishery and offshore renewable energy sector. It 
is clear from this that a balance between food supply, renewable energy and conservation has to 
be defined, as they all have their own targets on Member State-, region- and EU-level. 

6  DISCUSSION 

The study finds that fishing activity at the edges of active OWFs is largely representative of edge 
effects. While there was a reduction in fishing effort within Belgian OWF concession areas during 
turbine  construction,  the  Belgian  and  Dutch  beam  trawl  fleets  showed  a  "business  as  usual" 
approach  regarding  fishing  effort  and  landings  in  the  southern  North  Sea.  However,  the 
aggregated grid cell approach might have obscured potential edge effects. For more offshore wind 
farms, slight attraction towards the edges was suggested. During construction phases, reduced 
fishing effort was observed in the immediate surroundings of certain OWFs. Catch rate trends of 
target species, particularly sole, remained consistent in the presence of OWFs. Yet, there were 
indications  of  increased  catch  rates  for  plaice  in  the  vicinity  of  certain  OWFs,  aligned  with 
monitoring results that demonstrated increased plaice densities within OWFs. Notable changes in 
fishing  practices  occurred  between  2011  and  2022,  including  the  introduction  of  pulse  trawl 
vessels and shifts/loss in fishing grounds due to the fully operational OWF from 2020 onwards. 
Despite  small  changes  in  fishing  patterns  near  operational  OWFs,  the  impact  on  fishing 
activities  seems  modest,  indicating  adaptation  to  the  new  situation,  and  potential 
attraction to OWF edges. Fishers kept fishing at the edge of the OWFs as long as possible (see 
Figure 2), but in the end the entire area became lost as a fishing ground. In the overall effort and 
landings, we currently do not observe any change that could be linked to this loss. It was probably 
other factors (i.e. pulse fishery ban, fuel crisis, covid crisis) that are causing changes in effort and 
landings in period 2019-2022 (Verlé et al., 2023). However, the effects on fisheries might become 
more  pronounced  with  the  planned  further  expansion  of  operational  OWF  zones.  Further 
investigation is required to understand if the potential benefits of OWFs as nursery or 
feeding grounds for targeted fish species will contribute to healthier fish stocks. 

At the Belgium OWF, dedicated monitoring on the epibenthic and demersal fish community in and 
around  OWFs  has  been  going  on  since  2005  to  evaluate  the  potential  ‘refugium  effect’  and 
‘artificial reef effect’. This monitoring, according to a BACI design, showed that  soft sediment 
epibenthos and fish assemblages in between the turbines underwent no drastic changes 
due to the presence of the OWFs at mid/longer term. There are changes post-construction, 
with  even  a  much  higher  abundance/biomass  of  certain  species,  but  this  seems  to 
normalise afterwards. In general, the assemblages were mainly structured by temporal variability 
due  to  changes  in  temperature  and  climate  indices,  i.e.  North-Atlantic  Oscillation  and  Atlantic 
Multidecadal Oscillation, and this degree of change is proportionally much larger than the local 
effect of the present OWF areas. Nevertheless, some significant secondary effects could be 
clearly  related  to  the  presence  of  the  OWFs  pointing  to  an  expansion  of  the  OWF  effect 
beyond the immediate vicinity of the turbine on two fronts: (1) an expansion of the reef effect, 
and (2) signals of a refugium effect. 

Expansion of the reef effect is suggested through the appearance of an increased number of hard 
substrate-associated  species  (e.g.  Pisidia  longicornis,  Cancer  pagurus,  Dicentrarchus  labrax), 
mainly  by  the  significant  increased  abundances  of  blue  mussel  Mytilus  edulis  and  anemones 
Anthozoa  sp.,  two  species  dominating  the  epifouling  communities  on  the  turbines.  Although 
densities were still low,  they could increase the heterogeneity in the soft-bottom  sediments in 
between foundations in the future. First signs of a refugium effect were delineated based on the 
slight,  but  significantly,  increased  fish  densities  (Callionymus  lyra,  Buglossidium  luteum, 
Echiichthys  vipera  and  Pleuronectes  platessa)  inside  the  C-Power  wind  farm.  This  is  probably 
related to a combination of fisheries exclusion and increased food availability. More pronounced 
effects were found for C-Power than for the more offshore Belwind OWF, stressing that effects 
might be site-specific and that extrapolation of these findings to other OWFs should be done with 
care. 

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The effects of wind farms on epibenthos, demersal fish, and benthopelagic fish warrant ongoing 
monitoring with species-specific focus. A more species-specific focus was implemented in the OWF 
monitoring in Belgium on plaice, based on acoustic telemetry. The findings of the acoustic tagging 
study reveal that plaice exhibits high residency within a relatively small OWF area and 
displays specific spatial and diurnal movements. The fish tend to stay close to the turbines, 
particularly around the SPL situated approximately 25 meters from turbine foundations. Diurnal 
patterns show that plaice are more frequently detected on the SPL during the day, suggesting 
feeding  excursions  towards  this  area.  This  behaviour  aligns  with  plaice's  opportunistic  feeding 
habits and reliance on visual detection of prey (Gibson et al., 2015). During winter, plaice migrate 
away  from  the  OWF,  likely  towards  spawning  grounds  in  deeper  waters  (Solmundsson  et  al., 
2005).  However,  over  30%  of  tagged  fish  return  to  the  study  area  after  spawning, 
indicating high site fidelity. 

The study concludes that OWFs provide plaice with protection during the feeding season, primarily 
due  to  ample  food  supply  around  hard  substrates.  This  protection  might  enhance  local  fish 
production. However, the effect wanes during spawning migrations when plaice leave the OWF, 
exposing  them  to  fishing  mortality.  The  research  highlights  the  potential  of  OWFs  as 
protection areas for certain species but  suggests  that a larger, contiguous OWF zone 
might be even more effective in mitigating fisheries impacts. The study also demonstrates 
the  successful  integration  of  data  from  different  acoustic  telemetry  manufacturers  and 
recommends incorporating archival tags to capture three-dimensional fish positions and support 
further research on movement patterns, including spawning behaviors and migrations. 

Although  clear  convincing  evidence  of  spillover  effects  could  not  be  found  within  each  of  the 
studies, there were clear indications of positive wind farm effects and potential fish production 
within  the  OWF  zone.  To  assess  spillover  effects  more  effectively  within  this study,  a  gradient 
design  could  have  been  adopted  that  included  stations  at  different  distances  from  the  OWF. 
Whether the Belgium OWF zone will contribute to improving the state of the marine ecosystem 
by means of ecological or fishery spillover is not completely answered yet. This despite the very 
intense and in- depth monitoring programme within the area. Nevertheless, this has led to very 
valuable  insights  and  is  an  example  on  how  such  research  could  be  executed.  For  further 
investigating  spillover,  there  is  a  need  for  an  overall  continuous  monitoring,  combined  with 
species-specific  investigations  on  their  behaviour  and  migration  would  be  recommended.  The 
above data analyses show changes post-construction, based on BACI design, which is the best 
way  to  determine  ecological  and  /  or  fishery  spillover  effects.  This  type  of  analyses  is  not  yet 
repeated, because the focus in the further data analyses was more on describing changes within 
the farm, due to the possible ‘refugium’ and ‘artificial reef’ effects. It is planned to be done soon 
in the Belgium OWF program, based on a gradient BACI design approach, which should be most 
appropriate in determining spillover effects. 

7  CONCLUSIONS 

The  Belgium  OWF  study  demonstrates  dynamic  interactions  between  fishing  effort,  species 
landings, and LPUE in relation to OWF construction and operation, suggesting complex spatial and 
temporal patterns influenced by various factors, including fishing restrictions and fish behaviour. 
Fish  behaviour  and  potential  of  using  the  OWF  zone  is  species  dependent.  For  two  important 
commercial species within the Southern Bight of the North Sea, opposite effects were observed. 
For sole, the OWF area seems to create no additional benefits for the moment, whereas for plaice 
it creates opportunities, such as providing protection during the feeding season. Also, changes in 
the occurrence of several other epibenthic and fish species were observed based on long-term 
monitoring data, where ‘hard substrate’ species seems to extend their range of occurrence. These 
changes can be attributed to the ‘the refugium effect’ and ‘artificial reef effect’, created by OWFs. 
The  changes  were  not  consistent  at  the  two  wind  farms,  stressing  that  effects  might  be  site-
specific and that extrapolation of these findings to other OWFs should be done with care. 

At  the  Belgian  OWF  area,  benefits  for  certain  species  were  observed,  but  not  yet  any  clear 
evidence of spillover effects. Therefore, the effects of wind farms on epibenthos, demersal fish, 
and  benthopelagic  fish  warrant  ongoing  monitoring  with  species-specific  focus.  Future  edge 
effects, potentially due to fishing activities and closure benefits, could emerge as wind farm zones 
mature and integrate, influencing biomass and catch rate trends. Replication across wind farms 
and extended study durations are recommended to gain a deeper understanding of the evolving 
wind  farm  impacts  and  their  implications.  Specific  for  the  monitoring  and  gaining  evidence  on 

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spillover, a gradient sampling/data analyses, combined with species-specific research, is needed. 
The outcomes of the studies conducted within this Belgian OWF area illustrate this need clearly.  

8  REFERENCES 

Anderson,  M.  J.,  R.  N.  Gorley  &  K.  R.  Clarke  (2007).  PERMANOVA+  for  PRIMER:  guide  to  software  and 

statistical methods. PRIMER-E, Plymouth: 214 pp. 

Buyse, J., Reubens, J., Hostens, K., Degraer, S., Goossens, J., and De Backer, A.  (2023). European plaice 
movements sho w evidence of high residency, site fidelity, and feeding around hard substrates within an 
offshore wind farm. ICES Journal of Marine Science: 1–13, fsad179. 

De Backer, A., Polet, H., Sys, K., Vanelslander, B., and Hostens, K. (2019). Fishing activities in and around 
Belgian offshore wind farms: trends in effort and landings over the period 2006-2017. In Environmental 
impacts  of  offshore  wind  farms  in  the  Belgian  part  of  the  North  Sea:  Marking  a  decade  of  monitoring, 
research and innovation, p. 134. Ed. by S. Degraer, R. Brabant, B. Rumes, and L. Vigin. Brussels: Royal 
Belgian Institute of Natural Sciences, OD Natural Environment, Marine Ecology and Management.  

Gibson, R.N., Nash, R., Geffen, A.J., Van der Veer, H.W. (2015). Flatfishes: Biology and Exploitation. 2nd edn. 

542 pp. Oxford: Wiley Blackwell. 

Hintzen,  N.T.,  Bastardie,  F., Beare,  D.,  Piet,  G.J.,  Ulrich, C.,  Deporte,  N.,  Egekvist,  J.  & Degel,  H.  (2012). 
VMStools:  open-source  software  for  the  processing,  analysis  and  visualization  of  fisheries  logbook  and 
VMS data. Fisheries Research 115-116: 31-43. 

Methratta, E.T. (2020). Monitoring fisheries resources at offshore wind farms:  BACI vs. BAG designs. ICES 

Journal of Marine Science, 77: 890–900. 

Schwarz,  C.J.,  (1998).  Studies  of  uncontrolled  events.  In  Sit,  V.,  Taylor,  B.  (eds)  Statistical  Methods  for 

Adaptive Management Studies, BC Ministry of Forests: 19–40.  

Solmundsson,  J.,  Palsson,  J.  and  Karlsson,  H.  (2005).  ‘Fidelity  of  mature  Icelandic  plaice  (Pleuronectes 

platessa) to spawning and feeding grounds’. ICES Journal of Marine Science, 62: 189–200. 

Vandendriessche, S., Derweduwen, J., and Hostens, K.  (2015). Equivocal effects of offshore wind farms in 

Belgium on soft substrate epibenthos and fish assemblages. Hydrobiologia, 756: 19–35. 

Verlé, K., Pecceu, E., Polet, H., Hostens, K, Van Hoey, G., (2023). Fishing activities in the Belgian Part of the 

North Sea in the period 2007-2022. ILVO mededeling 

Whitehouse, R. J. S., Harris, J. M., Sutherland, J., and Rees, J. (2011). The nature of scour development and 

scour protection at offshore windfarm foundations. Marine Pollution Bulletin, 62: 73–88. 

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7.  CASE STUDY REPORT: 

LYME BAY MARINE PROTECTED AREA 

UK – THE ENGLISH CHANNEL 

Fishing boats moored in the Lyme Regis Harbour, Dorset, England© Pixabay 

Analysis of potential spillover effects around 
Lyme Bay Marine Protected Area 

Catherine Whitley 

MRAG Europe 

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TABLE OF CONTENTS 

1 
2 

3 
4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ......................................................................................... 110 
BACKGROUND .................................................................................................... 110 
2.1  History of the Lyme Bay MPA designation process ......................................... 111 
2.2  Management of the Lyme Bay MPA .............................................................. 112 
2.3 Monitoring of the reef .................................................................................... 112 
AIMS AND OBJECTIVES ....................................................................................... 113 
METHODOLOGY .................................................................................................. 113 
4.1  Study Area ............................................................................................... 113 
4.2 
Literature review ....................................................................................... 113 
4.3  Stakeholder survey .................................................................................... 114 
RESULTS ........................................................................................................... 115 
Literature review ....................................................................................... 115 
5.1 
Total abundance (fish biomass) ................................................................... 116 
Catch and fishing effort (CPUE) ................................................................... 117 
5.2  Stakeholder survey .................................................................................... 118 
Fishery Impacts ........................................................................................ 118 
Role of the MPA: Conservation vs. Fisheries Management ............................... 119 
Spillover effect from the Lyme Bay MPA ....................................................... 120 
DISCUSSION ..................................................................................................... 121 
CONCLUSIONS ................................................................................................... 122 
REFERENCES ..................................................................................................... 122 

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LIST OF ABBREVIATIONS 

Term 

aMER 

BACI 

BAP 

BRUV 

CPUE 

EFH 

FaSS 

IFCA 

iVMS 

Description 

applied Marine Ecosystems Research 

Before After Control Impact  

Biodiversity Action Plan 

Baited Remote Underwater Video 

Catch Per Unit Effort 

Essential Fish Habitat 

Fisheries and Seafood Scheme 

Inshore Fisheries and Conservation Authority 

Integrated Vessel Monitoring Systems 

LBFCIC 

Lyme Bay Fishermen’s Community Interest Company 

MCRS 

Minimum Conservation Reference Size 

MMO 

MPA  

NGO 

OC 

Marine Management Organisation 

Marine protected area 

Non-government organisation 

Open control 

OSPAR 

Convention for the Protection of the Marine Environment of the North-East Atlantic 

SAC 

SI 

Special Area of Conservation 

Statutory Instrument 

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1  EXECUTIVE SUMMARY  

In this case study, a qualitative and quantitative approach was used to assess the Lyme Bay MPA 
potential spillover  effects and  help  inform  a methodology to identify potential areas  where the 
designation of MPAs could lead to positive spillover effects. A combination of a literature review 
and stakeholder surveys were conducted to collect data from long-term monitoring studies and 
elicit perceptions from a range of stakeholders to understand the impact of the MPA on the marine 
environment and local fishing community.  

The  study's  primary  outcomes  highlight  an  alignment  between  evidence  obtained  from  the 
literature review and interview analysis. While it cannot be conclusively determined that spillover 
is currently occurring, there exists the possibility of future spillover into adjacent fisheries over 
an  extended  period.  This  conclusion  is  based  on  the  changes  in  fish  biomass  within  the  MPA 
showing  a  much  greater  increase  over  time,  relative  to  unprotected  sites,  indicating  potential 
spillover effects could be detected with extended monitoring. This is supported by the stakeholder 
surveys  which  reflected  general  agreement  that  there  is  a  high  likelihood  that  spillover  is 
occurring,  informed  by  the  increased  number  and  diversity  of  epibenthic  reef  species  and 
associated mobile fauna within the MPA, as well as changes in fisher catch composition. However, 
uncertainty prevails whether these changes are attributed to the MPA or external factors such as 
climate change, national legislation adjustments, or natural fish cycles. 

Regarding MPA management, contrasting perspectives emerged among stakeholders, with fishery 
managers  highlighting  the  MPA's  role  in  conserving  marine  biodiversity,  while  certain  fishers 
criticized its blunt approach and claimed increased fishing activity. Concerns focused on the lack 
of  a  comprehensive  management  plan  and  the  MPA's  location  at  the  border  of  two  managing 
authorities,  resulting  in  regulatory  disparities  and  an  absence  of  a  harmonized  whole-site 
approach  that  impacted  the  MPA's  effectiveness.  The  designation  process  through  a  Statutory 
Instrument  was  also  criticized  for  potentially  limiting  management  flexibility  and  leading  to 
unintended consequences, such as increased fishing effort from static fisheries. 

In summary, it is evident that the protection and enforcement of the Lyme Bay MPA is providing 
benefits  to  both  conservation  and  fisheries,  when  compared  to  surrounding  areas  still open  to 
bottom-towed gears. However, due to the paucity of research investigating spillover effects, there 
is a lack of evidence to confidently determine if spillover is occurring. Overall, the application of 
the Before After Control Impact (BACI) approach to assess spillover from the Lyme Bay MPA was 
successful. This was mainly due to the availability of baseline data collected before and after the 
MPA’s designation, as well as the monitoring of reference sites outside the MPA. Recommendations 
for  future  assessments  include  monitoring  additional  reference  sites  farther  from  the  MPA  and 
ensuring equal numbers of sites in each treatment area to enable better data comparability. 

2  BACKGROUND 

Located  along  the  south  coast  of  England,  Lyme  Bay  is  an  ecologically  diverse  marine  area 
renowned  for  its  unique  underwater  geology  and  rich  biodiversity.  This  expansive  bay  is 
characterised by highly varied seabed habitats and features of national conservation importance, 
such as reef habitats, sand and gravel banks, subtidal muds, submerged sea cliffs and rare chalk 
reefs. Three different types of reef habitat are found in Lyme Bay: bedrock reef, stony reef and 
biogenic reef- which are all recognised as priority habitats under Annex 1 of the European Union 
Habitats Directive 92/43/EEC. These reef features support a rich fauna of sessile species, most 
notably pink sea fans (Eunicella verrucosa), a protected species under Schedule 5 of the Wildlife 
and Countryside Act, and nationally rare sunset coral (Leptopsammia pruvoti), both of which are 
priority Biodiversity Action Plan (BAP) species. Furthermore, Lyme Bay is one of only five areas 
where the sunset cup coral is known to occur in UK waters (Natural England, 2012). Important 
commercial species also reside in these reef habitats, including the edible crab (Cancer pagurus) 
and European lobster (Homarus gammarus). Together, the structural complexity and high species 
richness  of  Lyme  Bay  has  resulted  in  the  area  being  identified  as  a  UK  “marine  biodiversity 
hotspot” (Hiscock and Breckels, 2007). 

Along the coastline, Lyme Bay extends 2,460 km2 from Portland Bill in east Devon to Start Point 
in west Dorset  (Rees et  al.,  2010) and  supports a thriving fishing community among the local 
ports of West Bay, Lyme Regis, Beer, Axmouth and Brixham. Prior to the establishment of the 
Lyme  Bay  MPA  in  2008,  the  local  fleet  consisted  of  approximately  25  trawlers  and  scallopers 
measuring over 10 m, with similar numbers of under 10 m trawlers and scallopers, and around 
90  vessels  involved  in  netting,  potting  or  “artisanal”  fishing  activities  (Andrews,  2008).  These 

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vessels  primarily  operate  within  close  proximity  of  their  respective  ports,  particularly  vessels 
stationed in the smaller ports, conducting their fishing operations predominately around the Lyme 
Bay  Reefs  (Andrews,  2008).  Within  the  bay,  King  scallop  (Pecten  maximus)  is  a  key  fishery 
resource, primarily targeted by scallop dredging. Additionally, crab, lobster and whelks (Buccinum 
undatum)  are  commercially  important  to  the  local  potting  fishery.  Most  of  the  trawling  is 
undertaken by otter trawls operating over mixed grounds targeting a diverse array of flatfish and 
demersal  species,  including  sole  (Solea  solea),  plaice  (Pleuronectes  platessa),  skate  and  rays 
(primarily thornback ray Raja clavata), bass (Dicentrarchus labrax), pollack (Pollachius pollachius) 
and cod (Gadus morhua). These species are also targeted by netting and handline fisheries.  

2.1  History of the Lyme Bay MPA designation process 

In the early 1990s, increasing concerns regarding the damaging impact of bottom towed fishing 
gear on the seabed led to local petitioning for fishery closures to protect sensitive reef features. 
Led by the Devon Wildlife Trust, surveys highlighted the destruction of reef habitats caused by 
scallop dredging and in 2001, a collaborative agreement between environmentalist groups and 
local fishers voluntarily closed two small areas, measuring approximately 4.6 km2 and 1.9 km2, 
to bottom  trawling  and scallop  dredging (Appleby, 2007).  This Agreement was successful until 
the winter of 2005-2006 when increased dredging activity led to a Ministerial Stop Order under 
the Sea Fisheries Act 1967 to close 60 square nautical miles (206 km2) to dredging to prevent 
further damage to mapped pink sea fan-dominated reef. In August 2006, the Secretary of State 
enacted a voluntary closure of four reef areas covering of 41.2 km2
, encompassing 90% of the 
habitat where pink sea fans occur (Devon Wildlife Trust, 2007, cited in Rees et al., 2010).  

However, the decision to restrict the closure to 41.2 km2, instead of the initially proposed 206 
km2,  was  deemed  inadequate  and  a  public  consultation  was  undertaken  in  2007  to  propose 
additional protection. Over 100 substantive responses and over 7000 responses from conservation 
organisation campaigns were received, of which 70% were in favour of the full 206 km2 closure 
(Defra, 2007, cited Rees et al., 2010). In June 2008, the Fisheries Minister announced the closure 
of 206 km2 of the northern part of Lyme Bay, enacting statutory measures against scallop dredging 
and demersal trawling, while permitting other static forms of fishing, such as scallop diving, static 
potting and netting. The Lyme Bay Designated Area (Fishing Restrictions) Order 2008 came into 
force on 11 July 2008 through the Statutory Instrument (SI) 158414 (Mangi et al., 2011).  

In  2010,  Natural  England  put  forward  Lyme  Bay  as  a  candidate  Special  Area  of  Conservation 
(cSAC) under the European Habitats Directive (92/43/EEC) to protect Annex I reef features. The 
Lyme Bay and Torbay SAC was later established in 2011, overlapping and  extending the SI to 
cover 312 km2 (Figure 1). The combination of the SI and the SAC form the boundary of the Lyme 
Bay MPA.  

Figure  1.  The  Lyme  Bay  Designated  Area  (black  line)  and  Lyme  Bay  and  Torbay  SAC 
(orange line) boundaries and associated ports. The dashed line indicates the boundary 
line between the two Inshore Fisheries and Conservation Authorities (IFCAs) (Sourced 
from Rees et al., 2019). 

14 https://www.legislation.gov.uk/uksi/2008/1584/contents/made  

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2.2  Management of the Lyme Bay MPA 

The Lyme Bay MPA is managed by two Inshore Fisheries and Conservation Authorities (IFCAs), 
with the Devon and Severn IFCA district to the west and Southern IFCA district to the east (Figure 
1). Despite both IFCAs having the same mandate to manage and protect designated reef features 
in  the  Lyme  Bay  MPA,  these  separate  entities  can  create  and  enforce  different  byelaws  (local 
regulations)  within  their  designated  areas  of  jurisdiction.  For  example,  while  both  IFCAs 
introduced byelaws prohibiting bottom towed fishing gear across 236 km2 of reef area in the Lyme 
Bay MPA (Southern IFCA, Devon and Severn IFCA 2014),  differences in Minimum Conservation 
Reference Sizes (MCRS) for catch landings has caused contention within the fishing industry. 

The lack in a harmonised approach to the management of the Lyme Bay MPA is exacerbated by 
the significant increase  in unregulated static forms of fishing, which emerged shortly after the 
exclusion  of  bottom  towed  fishing  gear.  Without  the  worry  of  mobile  vessels  removing  or 
damaging gear, the MPA became a magnet for static fishers operating pots and nets, resulting in 
more vessels and increased gear conflicts within and outside the MPA (Mangi et al., 2011; Rees 
et al., 2016). This escalation prompted the Blue Marine Foundation to form a collaborative working 
group in 2011, leading to the establishment of the Lyme Bay Consultative Committee. Comprising 
local  fishers,  conservation  agencies,  scientists,  IFCAs,  and  Marine  Management  Organisation 
(MMO) representatives, this Committee devised voluntary best-practice measures. Among these 
measures is a Code of Conduct, limiting gear deployment and incorporating real-time monitoring 
systems (Integrated Vessel Monitoring Systems or iVMS). 

While the Lyme Bay Consultative Committee is still operational, the most recent development has 
been the  establishment of  the  Lyme  Bay  Fishermen’s  Community  Interest  Company  (LBFCIC). 
Made up of 50 small-scale fishers from the four ports of Axmouth, Beer,  Lyme Regis and West 
Bay,  the  LBFCIC  provides  an  opportunity  for  all  industries  to  come  together  and  form  a 
representative  body  to  advocate  for  the  local  fleets.  Through  funding  from  the  Blue  Marine 
Foundation and Fisheries and Seafood Scheme (FaSS), administered by the Marine Management 
Organisation on behalf of Defra15, the LBFCIC aims to unite the local fishers and work with the 
local IFCAs and Defra to support the sustainable management of Lyme Bay’s marine resources.  

2.3 Monitoring of the reef 

Since the establishment of the SI in 2008, and subsequent designation of the SAC, the  applied 
Marine Ecosystems Research (aMER) team at the University of Plymouth has conducted annual 
monitoring to assess the ecological effectiveness of the closed area (Attrill et al., 2011; Mangi et 
al., 2011). The focus of this research is to measure the ‘recovery’ of epibenthic reef fauna, defined 
as the protected areas in the SI and SAC becoming more similar to previously protected areas 
and less similar to areas which remained open to towed demersal fishing (Sheehan et al., 2016). 
This  research  assists  in  monitoring  and  evaluating  the  effectiveness  of  conservation  measures 
and informing additional management strategies. However, the initial design of the survey limited 
the  ability  to  measure  spillover  effects  as  the  subsequent  SAC  designation  encompassed  the 
original control sites outside the  SI.  Consequently, there has been limited research specifically 
focussing on spillover effects from the Lyme Bay MPA. This indicates a notable knowledge gap 
that warrants increased attention to enhance our understanding of how MPAs may benefit fisheries 
through spillover. 

15 https://fass.marinemanagement.org.uk/Public/Home.aspx  

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3  AIMS AND OBJECTIVES 

The aim of this case study is to investigate the occurrence of spillover effects within the Lyme Bay 
MPA.  This  was  achieved  by  conducting  a  comprehensive  literature  review  to  determine  the 
presence or absence of spillover effects in areas surrounding the Lyme Bay MPA. In addition, a 
series  of  stakeholder  interviews  have  been  conducted  to  gain  an  understanding  on  whether 
spillover is perceived to be occurring and its potential ecological and socio-economic impacts.  

These aims and their associated research questions are listed below. 

1.  Conduct a literature review on the spillover effects of the Lyme Bay MPA.  
Is existing data on spillover available from the Lyme Bay MPA?  

• 
•  Are  there  currently  scientific  research  projects  underway  to  quantify  the  extent, 

occurrence and magnitude of spillover from the Lyme Bay MPA?  

•  What key factors or attributes of the Lyme Bay MPA could influence spillover dynamics?  
Is  there  any  research  on the  changes  in temporal  and  spatial patterns of  fish  biomass 
• 
after establishment of the MPA?  

•  How effective are the current methodologies for assessing spillover effects and how could 

they be improved for future assessments?  

2.  Conduct a series of interviews to gain an understanding of stakeholder perceptions of 

spillover effects associated with the Lyme Bay MPA.   
•  What level of knowledge do different stakeholders possess regarding the MPA regulations?  
• 
•  Have stakeholders observed a change in the temporal or spatial patterns of commercial 

Is the MPA acting as a conservation tool or a fisheries management tool?  

stocks after the establishment of the Lyme Bay MPA?  

•  Has  the  establishment  of  the  Lyme  Bay  MPA  generated  any  ecological  and  or  socio-

economic benefits to local fisheries?  

4  METHODOLOGY 

In this case study, a combination of a qualitative and quantitative approaches was employed to 
analyse the potential fishery and ecological spillover effects from the Lyme Bay MPA. For this case 
study,  the  methodology  used  involved  both  desk-based  research  (e.g.  literature  review)  and 
conducting a series of stakeholder interviews and online questionnaires. The following sections 
provide a detailed description of each method and subsequent data analysis. 

4.1  Study Area 

The Lyme Bay MPA was chosen as a case study due to its unique marine ecosystem, ecological 
significance,  controversial  designation  process  and  long-standing  conflict  between  the  local 
fisheries  and  conservation  efforts  to  restore  degraded  seabed  habitats  while  also  sustaining  a 
productive fishery. It is also important to note that the Lyme Bay MPA has been the focus of one 
of the longest monitoring projects in the UK, assessing the ecological effects and socio-economic 
benefits  of  removing  destructive  mobile  gears  to  protect  and  aid  the  recovery  of  nationally 
important reef habitats and reef associated species, including key commercial taxa. 

4.2  Literature review  

First,  an  in-depth  literature  review  was  conducted  to  collect  relevant  information  on  spillover 
effects.  The  review  followed  a  standard  three-stage  protocol:  (i)  collation  and  screening;  (ii) 
extraction; and (iii) critical appraisal. Literature searches were conducted in Google Scholar, which 
has been shown to be useful for both peer-reviewed and grey literature, as well as broad searches 
to obtain information from government reports and competent authority websites. Searches used 
Boolean logic to combine terms for the Lyme Bay MPA and different topics. Two simple words, 
“OR” and “AND”, were inserted between each keyword. For example, “Lyme Bay” OR “Lyme Bay 
MPA”  AND  “spillover”  OR  “fish  biomass”  OR  “fishery”.  This  resulted  in  each  search  generating 
outputs  which  included  literature  related  to  research  conducted  in  the  Lyme  Bay  MPA  which 
focused on changes in fish populations, benthic community assemblages or impacts on the local 
fishery.  

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The results from  the literature  search  were compiled  and analysed to extract data on spillover 
from the Lyme Bay MPA. However, it soon became clear that assessing spillover effects was not 
a key research priority within the existing literature and there was a lack of available raw scientific 
data with which to conduct a quantitative analysis. Nevertheless, there was a substantial library 
on research which had assessed the recovery of sessile and mobile fauna within the MPA (impact), 
compared to areas outside the MPA (control), mainly focusing on fish abundance/ biomass and 
diversity  of  taxa.  These  data  types  were  primarily  collected  using  various  underwater  video 
systems, such as towed flying array systems and baited remote camera systems.  

Using this secondary data, a comparative  analysis was conducted to analyse and interpret the 
potential occurrence of spillover from the Lyme Bay MPA. Since the prohibition of bottom towed 
gear in 2008, consistent annual monitoring of the same sites, both within and outside the MPA, 
has occurred during the summer months, with the initial survey in 2008 serving as the baseline 
'Before' data. Therefore, a before-after-control-impact (BACI) approach was used to compare the 
biomass before and after the establishment of an MPA (regarding the total biomass of the MPA 
and reference site), with potential spillover only occurring in three scenarios, as shown in Table 
1. The data results from the literature will be compared against this table to indicate if spillover 
is occurring. 

Table 1. Potential combinations of theoretic changes in biomass in the MPA site (Δ MPA) 
and in the reference site (Δ Ref) which indicate whether a conclusion can be drawn to 
indicate spillover is potentially taking place.  

Δ MPA   Δ Ref  Scenario name 

10% 
5% 
10% 

5%  Both increased, but MPA stronger 

10%  Both increased, but ref. site stronger 
10%  Mutual increased 

Biomass?  Protection?   Spillover? 
Potentially 
Increase 
Potentially 
Increase 
Potentially 
Increase 

Yes 
No 
Potentially 

4.3  Stakeholder survey 

In addition to the literature review, a questionnaire was developed to assess the perceptions of 
key stakeholders on the potential spillover effects in their nearby MPAs. The questionnaire (Annex 
4) comprised of open-ended and closed questions to elicit stakeholder views and experiences on 
the  different  aspects  of  this  study.  The  open-ended  questions  aimed  to  capture  stakeholder 
opinions on, for example, how  aware  the  stakeholder was of the regulations and management 
measures of the MPA. The closed questions were statement-based and used Likert scale answer 
categories  (such  as:  Strongly  agree;  Agree;  Neutral;  Disagree;  Strongly  Disagree)  for  the 
stakeholder to choose from.  

The  questions  were  grouped  into  four  broad  categories  to  encapsulate  the  key  issues  being 
studied. These included:  

(i)  Respondent  information.  The  first  section  required  basic  information  from  the  respondent, 
including their name, institution and the type of stakeholder category they belonged to. 

(ii)  Background  information.  The  second  section  of  the  questionnaire  gathered  background 
information from the stakeholder to understand more about the respondent and their use of the 
MPA. Questions included knowledge of when the MPA was established, the type of restrictions in 
place and how long the stakeholder has been associated with the MPA either through research, 
fishing or managing it.  

(iii) Fishery impacts of MPAs. The third section explored the respondent’s perceptions of the socio-
economic  impacts  of  spillover  from  the  MPA.  Stakeholders  were  asked  to  state  whether  the 
designation of an MPA / area where fishing is limited has led to an increase in revenues for fishers, 
whether the fishing community in the area feel their fisheries livelihoods are more secure after 
the  MPA  was  established,  and  the  extent  to  which  they  believe  spillover  from  the  MPA  has 
influenced the catch composition in adjacent fishing grounds. 

(iv)  MPAs  as  management  tools.  The  fourth  section  of  the  questionnaire  focused  on  the 
respondent’s  perceptions  on  whether  MPAs  are  conservation  or  fisheries  management  tools. 
Stakeholders were asked to state whether their local MPA was acting as a conservation tool, a 
fisheries management tool or both. Other questions under this section required stakeholders to 
state  their  agreement  /  disagreement  on  whether  the  establishment  of  MPAs  is  an  effective 

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conservation  strategy  to  support  fish  populations  and  commercial  fisheries  in  their  area. 
Respondents were also asked to indicate what factors they thought were contributing to spillover 
effects. 

Four key stakeholder groups were targeted under this consultation including commercial fishers, 
fisheries managers and government authorities, scientists, and environmental non-government 
organisations (NGOs). Therefore, while the four sections of the questionnaire where the same, 
specific questions were included for each of the four respondent groups. Prior to the distribution 
of  these  questionnaires,  the  client  provided  feedback  on  the  structuring  and  content  of  the 
questions. Once agreed, the questionnaire was set up as an online survey using LimeSurvey. 

A stakeholder mapping exercise was conducted to identify key stakeholders and an initial email 
detailing the aims and objectives of the project was circulated. In total, 20 emails were sent to 
various stakeholder groups, including, but not limited to, the Devon and Severn IFCA, Southern 
IFCA and MMO (fisheries managers), scientists affiliated with the University of Plymouth; the Blue 
Marine  Foundation  (NGO);  and  the  Lyme  Bay  Fishermen  Community  Interest  Company 
(commercial  fishers).  Once  initial  contact  was  made,  an  offer  of  a  one-to-one  interview  was 
proposed; either remotely via Microsoft Teams or face to face. Given the summer holidays and 
workload of stakeholders, every effort was made to accommodate each stakeholder’s preference, 
including a brief trip to the local ports of Beer and Axmouth to speak to some of the commercial 
fishers.  

The resulting qualitative data derived from the interviews was then analysed using comparative 
thematic analysis.  

5  RESULTS 

5.1  Literature review 

Since  the  establishment  of  the  SI  in  2008,  and  subsequent  SAC,  long-term  monitoring  of  the 
ecological effectiveness and socio-economic benefits of the closed area has been undertaken to 
measure the ‘recovery’ of epibenthic reef fauna (Rees et al., 2010; Attrill et al., 2011; Mangi et 
al., 2011; Sheehan et al., 2013a; Stevens et al., 2014; Sheehan et al., 2016; Kaiser et al., 2018; 
Rees et al., 2019; Davies et al., 2021; Davies et al., 2022). Over time, research on the closure 
of the Lyme Bay MPA to trawling and dredging has demonstrated significant positive impacts on 
the local ecosystem’s recovery. Studies indicate that the reduction in collateral damage to habitat 
complexity has led to improvements in species richness, total abundance and benthic assemblage 
composition within the Lyme Bay MPA.  

Within the literature, notable, observations reveal a resurgence in slow growing sessile species 
just three years after the closure, particularly in hydroids (229%), ross coral Pentapora fascialis 
(385%), branched sponges (414%) sea squirts (Phallusia mammillata) and pink sea fans (636%) 
(Sheehan et al., 2013a), as well as definitive evidence of significant increase in species richness, 
structural complexity of the seabed and body-size measurements of individual species compared 
to unprotected control sites still open to bottom towed fishing (Hinz et al., 2011; Sheehan et al., 
2013a;  Stevens  et  al.,  2014;  Sheehan  et  al.,  2016;  Kaiser  et  al.,  2018;  Davies  et  al.,  2022). 
These sessile organisms are fundamental to the health and development of rocky reef habitats, 
capturing and recycling nutrients through filter feeding and producing planktonic larvae, further 
supporting higher trophic species such as fish and shellfish species (Sheehan et al., 2013a; Rees 
et al., 2016). Additional  research has also observed  sessile taxa (associated with reef  habitat) 
colonising pebbly sand habitats within the Lyme Bay MPA, extending the ‘known’ boundary of the 
protected reef feature (Sheehan et al., 2013b; Pikesley et al., 2021). 

In addition, a study by Davies et al. (2021) revealed a remarkable 56.9% increase in the number 
of taxa within the MPA between 2009 and 2019, in contrast to a less substantial 15.8% increase 
in non-protected control sites. While these results were just based on video analysis from baited 
remote underwater videos (BRUVs), a similar study by Davies et al. (2022), combined the results 
of BRUV and towed video data and demonstrated 38.9% increase in the number of taxa in the 
MPA (from 31.5 ± 1.09 in 2009 to 43.7 ± 2.16 in 2018: a) and a minimal decrease in the OC 
(from  26.2  ±  1.64  in  2009  to  25  ±  1.59  in  2018:  a  4.8%  decrease).  Both  studies  highlight  a 
significant increase in diversity within the MPA. 

However, to effectively identify and quantify spillover effects, the primary types of fishery data 
suitable for potential analysis include fish abundance/biomass; larval biomass; fish size, weight 

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and  age;  and  fish  movement  patterns.  The  literature  review  revealed  a  noticeable  paucity  in 
spillover effect data from the Lyme Bay MPA, yet research into changes and potential recovery of 
fish  abundance/biomass  was  available.  To  assess  the  area’s  recovery,  prevailing  literature 
predominately  employed  remote  data  collection  methods  such  as  visual  detection  surveys, 
operating high definition video within the MPA and in adjacent sites which remained open to fishing 
(Open Controls; (OC). Monitoring of sessile and sedentary species along benthic transects were 
conducted using towed underwater video systems referred to as "towed flying arrays," while BRUV 
systems  were  employed  to  sample  reef-associated  nekton  species  and  mobile  benthic 
assemblages (Sheehan et al., 2010, 2013a). The results of the data analysis from the literature 
are detailed below. 

Total abundance (fish biomass) 

Over  the  course  of  an  11-year  study,  the  results  of  video  analysis  from  a  series  of  BRUV 
deployments  reported  the  mean  total  abundance,  calculated  using  MaxN,  within  the  MPA  had 
changed  from  1.66  ±  0.09  in  2009  to  2.13  ±  0.09  in  2019,  reflecting  a  28.9%  rise  in  total 
abundance (Davies et al., 2021). In comparison, within the OC, the total abundance shifted from 
1.98 ± 0.04 in 2009 to 2.44 ± 0.1 in 2019, marking a 23.4% increase in total abundance (Davies 
et  al.,  2021).  Based  on  these  results,  the  difference  in  percentage  increase  indicate  potential 
spillover effects could occur from the MPA into surrounding areas. However, for spillover to occur, 
it is crucial that the biomass of fish within the closed area is higher than outside it. Therefore, 
even  though  both  sites  showed  a  significant  linear  increase  in  fish  biomass,  the  mean  total 
abundance was greater in the OC and therefore spillover is unlikely at this time. Nevertheless, 
the increasing trend in total abundance was higher in the MPA, therefore, over time, there is the 
potential for spillover. 

In the same study, Davies et al. (2021) investigated the change in total abundance of exploited 
fish over time in the MPA, relative to areas that remain open to bottom towed fishing. The indicator 
species  included,  but  were  not  limited  to,  Ballan  Wrasse  (Labrus  bergylta),  Pollack  (Pollachius 
pollachius), Small-Spotted Catshark  (Scyliorhinus canicular), Sole (Solea solea), thornback ray 
(Raja clavata), Atlantic Horse Mackerel (Trachurus trachurus) and Pouting (Trisopterus luscus). 
After video analysis, the total abundance of exploited fish had increased inside the MPA by 370% 
(0.311 ± 0.09 in 2009 to 1.45 ± 0.05 in 2019), as well as within the OC by 420% (0.316 ± 0.13 
in 2009 to 1.63 ± 0.17 in 2019) (Figure 2c). From these results, it can be concluded that even 
though  the  reference  site  showed  a  greater  increase  in  total  abundance,  there  remains  the 
potential for spillover due to the overall increase in biomass.  

Concurrently,  the  diversity  of  exploited  fish  (number  of  taxa)  was  also  found  to  dramatically 
increase within the MPA by 430% (from 0.42± 0.12 in 2009 to 2.23± 0.18 in 2019) and the OC 
by 480% (from 0.28 ± 0.11 in 2009 to 1.61 ± 0.22 in 2019). This change over time was significant 
in both treatment areas, although Davies et al. (2021) observed a much greater increasing trend 
in the number of taxa within the MPA (gradient of 0.14) compared to the OC sites (gradient of 
0.03) (Figure 2a). The study suggested the slower rate seen in the OC may be due to delayed 
‘spillover  effects’  from  the  MPA  to  the  surrounding  area,  possibly  driven  by  a  combination  of 
increased larval export and direct adult migration. 

When investigating the difference in non-exploited fish, the indicator species included, but were 
not limited to, Gobies (Gobiidae spp.), Blennies (Blenniidae spp.), Whiting (Merlangius merlangus) 
and  Poor  cod  (Trisopterus  minutus).  The  results  were  very  surprising  as  they  demonstrated  a 
significant linear decrease (3.3 %) in mean total abundance within the MPA (1.46 ± 0.09 in 2009 
1.41 ± 0.1 in 2019) compared to the OC which exhibited a 37% increase in total abundance (1.14 
± 0.16 in 2009 to 1.56 ± 0.18 in 2019) (Davies et al., 2021). These results indicate the biomass 
of non-exploited mobile fish populations are decreasing within the MPA, but increasing within the 
OC. This scenario suggests spillover is not occurring but could be influenced by other drivers such 
as increased predation and competition with larger species (e.g. exploited fish) which may have 
decreased the area of favourable habitat to non-exploited fish within the MPA.  

Interestingly for invertebrate species, there was a clear difference between the increase in total 
abundance of exploited and non-exploited species within the MPA, 110% and 37% respectively, 
compared to the outside the MPA, 85% and 0.47% respectively (Davies et al., 2021). Despite the 
greater increase in exploited invertebrates within the MPA, total abundance was significantly lower 
in the MPA compared to the OC, potentially due to greater fishing effort from the static fishery. 
However, it is interesting to note that for the main species targeted by static fisheries- whelks, 
brown crab and European lobster- there was no significant temporal change in total abundance, 
regardless of potentially higher fishing levels. 

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One of the drivers influencing the increase in total abundance of mobile species within the MPA 
could be due to changes in functional richness (variety and diversity of functional traits present 
within  a  given  ecological  community  or  assemblage)  which  reportedly  increased  by  64.6%, 
relative to the unprotected areas where it decreased by 1.85% (Davies et al., 2022).  It is likely 
the increase in functional richness of the reef area, also known as Essential Fish Habitat (EFH), 
has  contributed  to  the  positive  increases in  mobile  fauna  over  time,  including  the  increases  in 
exploited  fish  species  targeted  by  the  local  fisheries  (Davies  et  al.,  2021).  This  highlights  the 
protection and enforcement of the Lyme Bay MPA is providing benefits to both conservation and 
fisheries, when compared to surrounding areas still open to bottom-towed gears. 

Figure  2  Number  of  taxa  (a)  and  total  abundance  (c)  of  Exploited  fish  by  year  and 
treatments, and number of taxa (b) and total abundance (fourth root transformed: d) 
of  non-exploited  fish  by  year  and  treatments  (marine-protected  area  [MPA]:  blue 
circles, open controls [OC]: grey triangles). Lines and equations show linear regression 
equation  coefficients.  Points with  errors  bars  show  mean  values  and  standard  errors 
(Davies et al., 2021) 

Catch and fishing effort (CPUE) 

Changes in fishing activity is an important determinant of the success of an MPA demonstrating 
spillover  effects.  Therefore,  in  addition  to  comparing  fish  biomass  before  and  after  the 
establishment of an MPA, it is also important to consider the catch landings and fishing effort to 
analyse if the local fisheries have benefited from the presence of the MPA. Catch per unit effort 
(CPUE) represents the volume of catch obtained per unit of fishing effort and is commonly used 

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as a proxy for fish abundance or biomass. However, it should not be used in isolation as other 
factors can have an influence on CPUE, such as seasonality, natural variability and fluctuations in 
market price. 

In Lyme Bay, bottom towed fishing gear is prohibited within the SI and some parts of the SAC, 
covering  an  area  of  236  km2  within  the  MPA.  The  MPA  is  therefore  recognised  as  a  “partially 
protected area (PPA)” as demersal gear is still allowed in some restricted areas, as well as static 
fisheries,  rod  and  line,  scallop  diving  and  other  recreational  activities.  Shortly  after  the 
implementation of the Lyme Bay MPA, Mangi et al. (2011) assessed the socio-economic impact of 
the closure on the local fishing community. Initial results revealed the MPA had led to decreased 
incomes for displaced towed fishers, mainly due to increased travel times to fishing sites, longer 
fishing duration and lower quality of scallops harvested outside the MPA; and increased incomes 
for static fishers due to increased fishing effort (Mangi et al., 2011). For example, brown crab and 
lobster  values  and  landing  weights  have  increased  within  the  Lyme  Bay  and  Torbay  SAC  as  a 
result of the increase in commercial potting effort (Rees et al., 2016; Rees et al., 2019).   

Reports of increased fishing effort is corroborated by a recent study which observed a significant 
increase in the number of vessels and fishing trips (per month per vessel) of fishers using static 
gear  inside  and  outside  the  MPA  (Rees  et  al.,  2021).  Between  2005/6  and  2016/17,  the 
approximate number of vessels per month increased by 7 (from 29 to 36) and 12 (from 40 to 52) 
for static gear inside and outside the MPA, respectively, while the number of fishing trips increased 
by 223 (from 58 to 281) and 185 (158 to 343) respectively, demonstrating a significant trend in 
increased fishing effort (Rees et al., 2021). 

However, over time, Rees et al. (2021) reported static gear landings had decreased by 110 kg 
per vessel per month. Despite this, the value of landings had increased, represented by a £1,452 
increase (per vessel per month) for vessels fishing inside the MPA compared to a £866 increase 
for vessels fishing outside the MPA (Rees et al., 2021). This is largely linked to catches of higher 
value species such as diver-caught scallops, with a 412 % increase in value, and crab and lobster 
landings  from  static  potting,  with  a  combined  increase  of  104  %  in  value.  For  net  fisheries, 
landings of high value species such as lemon  sole  increased by 57 kg (5700%), resulting in a 
£285 increase (4750 %). Across the study region, the landings and value of whelk were highest, 
yet  experienced  a  37  %  and  0.48  %  decline  in  landings  from  within  and  outside  the  MPA 
respectively, while the value marginally increased by 4 % and 13 %, respectively.   

Following the SI designation in 2008, there is a corresponding increase in mobile demersal gear 
effort outside the MPA. This increased effort raised the average value of landings by £2,231 per 
vessel per month during 2004/05–2007/08 and 2014/15–2016/17. Although the value of landings 
for  vessels  using  mobile  gears  outside  the  MPA  has  shown  some  return,  reaching  £9,021  per 
vessel per month for 2016/17, it is still below the peak landings values reached prior to the SI 
closure (£15,311 per vessel per month) in 2005/06 (Rees et al., 2021). This is largely due to the 
loss of scallop grounds from within the MPA which has led to a 65% increase in weight and 136% 
increase in value from scallop landings outside the MPA.  

5.2  Stakeholder survey 

In total, 9 in-depth interviews were conducted with stakeholders from three different stakeholder 
groups:  fishers  (n=5),  fishery  management  authorities  (n=1)  and  scientists  (n=3).  The 
questionnaire was divided into sections to provide a background of each respondent and their use 
of the MPA, as well as gain an understanding of their views on the fishery impacts of the MPA and 
whether  the  MPA  is  acting  as  a  conservation  or  fisheries  management  tool.  During  qualitative 
analysis, the interview transcripts were assessed to identify common themes, topics and patterns 
in stakeholder responses. The results of the qualitative analysis deriving from these interviews is 
provided below. 

Fishery Impacts 

Changes in fish biomass 

Since  the  establishment  of  the  MPA,  stakeholders  agreed  they  had  observed  changes  in  fish 
abundance and species composition, with a more diverse range of species found inside the MPA 
than outside. In particular, one scientist observed the main difference was the recovery of the 
sensitive biogenic reef and associated reef species inside the MPA, as well as an increased number 
of higher trophic level animals, such as pout, wrasse and shark and ray species, which rely more 
heavily on protection from mobile demersal  gear. A small number of fishers also agreed some 

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species  had  become  more  abundant  within  the  MPA,  primarily  lobsters,  dover  sole  and  black 
bream.  

Outside the MPA, one scientist revealed the results from grab samples found very little evidence 
of infauna residing in the muddy sediment compared to protected areas. They explained there 
was no time for species to live there as the area is constantly being trawled.  

Changes in catch and number of fishers (MPA impact) 

Since the establishment of the MPA, fishers have noticed changes in their catch, such as increased 
lobster, scallop and dover sole landings while crab catches have decreased. This was also noted 
by the fishery managers which emphasised an increase in scallop diving and netting for sole within 
the MPA, as well as decreases in crab landings which has been reported channel wide. However, 
there is uncertainty as to whether these changes are resultant from the MPA or other external 
factors such as climate change, improved national legislation for lobsters (e.g. returning berried 
lobsters and v-notching) or increased quota for dover sole. Further, two fishers attributed changes 
in catch to the natural cycles of fish species stating, “fish run a cycle of 7-10 years so yet to see 
if closure caused that or if species are running their cycle”.  

During the interviews, there were mixed views on the changes in the number of fishers operating 
within and outside the MPA. While two fishers disagreed there had been a change in the fishing 
community, three fishers agreed there were more fishers than before the MPA was established. 
One fisher explained more local vessels from Hastings, Devon and Cornwall were coming into the 
bay, in particular to target whelks due to considerable economic incentives, while another fisher 
attributed the increase in fishers to the changes in council policy on commercial moorings which 
he  perceived  had  led  to  a  huge  leap  in  commercial  boats  in  Lyme  Regis  and  West  Bay.  One 
scientist  agreed  there  had  been  an  increase  in  the  number  of  fishers  operating  in  the  MPA, 
especially  scallop  divers;  however,  the  fishery  managers  disagreed  and  stated  there  were 
generally fewer fishing vessels now from the local ports, although it was noted there has been an 
increase in nomadic static gear (netting and potting) since the MPA was established. 

Economic and social benefits  

There were mixed opinions on whether the fisheries in this area benefit economically by having 
the MPA. Out of five fishers, two agreed they had, also stating fish catches had increased, while 
three fishers expressed neutral opinions on the matter, with two fishers referencing the restriction 
on towed gear had allowed static pots and nets to increase and spread out due to increase gear 
security and reduced conflict. One fisher stated, “some would argue yes and some would say no. 
For scallop diving I would say yes, but I used to trawl so I would say no. I can’t go outside as 
there are so many nets, no room out there to fish”. Moreover, the three interviewed scientists 
strongly agreed there has been an economic uplift to the fishers since the MPA was introduced, 
based on the increase in fish landings and quality of catches, reduction in conflict between the 
static and mobile sector and increase in scallop diving which is now quite a successful industry 
since the MPA.  

When asked to comment on the impact of the MPA on revenues, three fishers agreed the MPA 
had led to an increase in revenues due to fishers changing their modes of fishing and increasing 
the amount of gear they work. However, one fisher commented that the increase in effort was 
not  as  envisioned  when  the  MPA  was  established,  while  another  fisher  stated,  “I  believe  the 
designation  of  the  Lyme  Bay  MPA  through  a  statutory  instrument  through  parliament  was  the 
wrong way to create this MPA as it limited the flexibility of the MPA management.” 

There was general agreement across all stakeholder groups that fisheries livelihoods were more 
secure after the MPA was established. However, one fisher expressed concerns about the dramatic 
increase in vessels and gear which could impact the sustainability of the fishery. In contrast, one 
scientist  strongly  agreed,  stating  that  “if  you  carry  on  business  as  usual,  the  fisheries  will 
collapse”. 

Role of the MPA: Conservation vs. Fisheries Management 

Throughout the interviews, multiple respondents emphasised the dual role of the MPA as both a 
conservation  and  a  fisheries  management  tool,  safeguarding  the  marine  biodiversity  and 
subsequently  benefitting  the  local  fishing  community.  However,  while  the  fishery  managers 
argued  it  was  mainly  a  conservation  tool,  some  fishers  argued  the  MPA  was  “too  blunt  an 

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instrument to use as a conservation tool” and contested that “there’s more fishing in here now 
than  before”.  When  queried  about  the  effectiveness  of  MPAs  as  a  conservation  strategy  for 
supporting  fish  populations  and  commercial  fisheries  in  the  region,  fishers  provided  mixed 
responses, ranging from disagreement to agreement. One fisher firmly disagreed, stating, "No, 
it's  not  effective  conservation,  it  could  be,  but  it  isn't."  This  was  later  refuted  by  the  fishery 
managers  asserting  that  the  designation  of  the  MPA  safeguards  the  benthic  habitats  and 
associated reef species through protection from damaging fishing gears, fostering collaboration 
within the fishing community and prompting discussion on management, such as the Lyme Bay 
Fishermen’s Community Interest Company. Despite bring together more stakeholders, one fisher 
countered  that  some  authorities  had  not  been  involved,  citing  the  example  of  local  councils 
altering mooring allocation, affecting the area's conservation effectiveness.  

When asked if certain areas of MPA should be closed to develop commercial fisheries, the fishery 
managers clarified, “We close fishing to protect features, not to develop fisheries. We hope as a 
benefit there will be positive impacts on the fisheries but we do not manage based on commercial 
fisheries.”  In  contrast,  all  interviewed  scientist  strongly  advocated  for  such  closures,  with  one 
scientist  emphasising  the  need  to  have  reference  areas  to  monitor  the  recovery  and  progress 
towards  achieving  conservation  goals  and  objectives.  Another  scientist  claimed,  “an  MPA  that 
doesn't have any fisheries closures is a paper park. You must close or partially close the fisheries 
that were previously occurring. Unless you do some management there is no management.” On 
the other hand, fishers strongly disagreed with the notion to permanently closed certain areas of 
the MPA, reasoning that “it’s ludicrous, there are areas which don't get fished at all, sometimes 
for years, and then come into their own. Close them off and they'll become stagnant.” This was 
supported  by  another  fisher  claiming  that  “closing  areas  entirely  to  fishing  just  doesn’t  work. 
Under belief it would harm fishing but also actual fish species as the ecosystem is a very delicate 
and balanced instrument…. closing the box could well have impacted species not to come back 
here.” By closing one area, one fisher  explained  that everyone else will go to different places, 
resulting in an “overspill of fishing activity to where it is permitted”. Another fisher agreed, stating, 
“None of it should be closed to fishing. It should be managed using flexible measures agreed by 
industry and regulators.” 

Currently,  the  MPA  does  not  have  a  management  plan  and  operates  without  a  “whole  site 
approach”, instead management is based on the status and distribution of designated “features” 
within the MPA. The fishery managers noted, “The presence of the MPA and conservation advice 
provides a direction for fisheries management”. However, many fishers advocated for the MPA to 
have  a  dedicated  management  plan.  Reflecting  on  the  MPA's  location  at  the  border  of  two 
managing authorities, fishers deemed it a failure due to disparities in regulations on each side. 
One fisher observed, “there’s an artificial line that is just the side of Lyme Regis and we can do 
certain things and it’s all different on the other side. It’s ludicrous to build box with that in place. 
It should’ve been a larger box with its own management…. If it had its own management plan it 
could work as a conservation area, until then, it will never work.” These views were shared by 
another fisher stating, “Dorset boats land smaller fish. The minimum landing size should be the 
same across the bay, government size. In Lyme Regis they have smaller catches because its legal. 
I don’t fish in southern waters now.”  

In  addition  to  the  geographic  positioning  of  the  MPA,  one  fisher  argued  that  the  designation 
process  of  the Lyme  Bay  MPA  was  also  a  failure.  They  explained,  “the designation of  the  MPA 
through a Statutory Instrument through Parliament was the wrong way to create this MPA as it 
limited the flexibility in the management of it.” Consequently, when asked if the MPA was acting 
as a conservation tool or a fisheries management tool, the fisher replied saying, “This MPA was 
created  by  people  who  didn't  know  the  area.  I  would  say  it  is  a  tool  to  constrain  the  fishing 
industry. If it had been created with the fishing industry where it was done  in a way where the 
management wasn't so rigid, then it would've been much better and more beneficial to the fishers 
and those that wanted to protect the marine environment within the area.” 

Spillover effect from the Lyme Bay MPA 

Overall, the majority of respondents concurred that spillover of fish or larvae export was 
taking place from the Lyme Bay MPA, leading to benefits for adjacent fisheries to some extent. 
Notably,  the  interviewed  scientists  collectively  expressed  the  likelihood  of  spillover,  with  two 
considering it “likely” and the third characterising it as “highly likely”. They indicated that spillover 
had  likely influenced the catch  composition in nearby  fishing grounds “to a large extent”. This 
conclusion is drawn from observed increased in species abundance and diversity, with potential 
spillover benefits, as well as findings from socio-economic studies conducted by Rees et al., (2016, 
2021). Three other respondents, spanning both stakeholder groups, also aligned with the view 

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that  fishery  spillover  was  probable,  while  two  fishers  expressed  uncertainty.  Yet,  opinions 
diverged when asked about the contribution of MPA spillover to the recovery of overexploited fish 
populations  in  adjacent  fisheries.  One  fisher  agreed  it  had  to  a  “moderate  extent”,  while  two 
acknowledged  to  a  “small  extent”,  another  admitted  uncertainty,  and  a  final  fisher  disagreed, 
asserting “not at all. Can’t see how any of it has, outside is trawler ground which now claimed by 
netters. Nothing gets outside.” 

Regarding the factors driving spillover effects, respondents identified key influences as 
“years  since  the  MPA  was  established”  (n=3),  “size  of  MPA”  (n=2),  “protection  level” 
(n=2),  “dominant  habitat”  (n=1)  and  “other”  (n=1),  specified  as  the  absence  of  scallop 
dredging in the area.  

However,  through  the  interviews,  it  became  evident  that  many  stakeholders  were  unable  to 
confidently  address  spillover-related  questions,  primarily  because  of  the  insufficient  research 
available on the topic. This was supported by the scientists confirming that investigating the 
spillover  effects  of  the  MPA  was  not  a  primary  focus  in  their  research.  Nevertheless, 
there  was  consensus  that  spillover  would  be  prioritised  in  future  research  and  it  was 
noted that ongoing research featured acoustic telemetry and tagging projects aimed at monitoring 
the movement, habitat use and residency of commercially important species like brown crab and 
lobster. A scientist noted, “spillover is a paradox where we don't know if the fish are moving inside 
to outside or outside to inside. Species may have grown inside and recruited outwards, or there 
might be an inward flow because they are safer within the MPA. It needs dedicated research such 
as  telemetry  and  tracking  fish  movements  and  duration  in  each  place  to  prove  it,  usually  a 
gradient of a fish from outside the MPA, within a buffer zone and inside, the MPAs but takes years 
to know for sure.” 

6  DISCUSSION 

From the results, it can be concluded that the data presented in the literature review and findings 
from the analysis of the interview transcripts positively correspond to  suggest that potential 
spillover effects are occurring from the Lyme Bay MPA. However, within the literature on 
the Lyme Bay MPA, it is evident there is a paucity of research focussing on spillover effects. 
Despite this, it was confirmed in the stakeholder surveys that current scientific research projects 
are underway to quantify the extent, occurrence, and magnitude of spillover from the Lyme Bay 
MPA  and  wider  English  Channel.  This  work  is  mainly  collecting  data  on  fish  movements,  using 
acoustic telemetry and tagging; larval biomass from plankton samples; and continuing to monitor 
changes in fish abundance/biomass within and outside the MPA using underwater video systems.  

Within the existing body of literature, numerous studies have evidenced the ongoing recovery of 
the benthic reef environment, leading to a significant increase in the abundance and diversity of 
reef associated species. Notably, the proliferation of sessile species which are known to be more 
sensitive and essential for reef formation, such as erect branching sponges and ross corals, has 
been  documented  within  the  MPA  (Sheehan  et  al.,  2013a;  Sheehan  et  al.,  2013b).  Moreover, 
increases in the biomass of mobile fauna, including commercially valuable taxa (~400 % increase 
over 11 years) and higher trophic-level species, have also been observed (Davies et al., 2021, 
2022). However, for spillover to occur, it is crucial that the biomass of fish within the closed area 
is higher than outside it. Therefore, even though both sites (inside and outside the MPA) showed 
a significant linear increase in fish biomass, the mean total abundance was greater outside the 
MPA  and  therefore  spillover  is  unlikely  at  this  time.  Nevertheless,  the increasing trend  in  total 
abundance was higher in the MPA, therefore, over time, there is the potential for spillover. It is 
worth noting that the total abundance of exploited fish is still increasing within the MPA, despite 
continued  fishing  activities  and  heightened  efforts  in  static  fisheries.  This  indicates  that  the 
protection and enforcement of management measures within the Lyme Bay MPA provides both 
benefits to conservation and fisheries alike.  

Notably, the exclusion of demersal gear has been a key attribute to the recovery of the benthic 
habitat, particularly the revival of biogenic reefs which are recognised as essential fish habitats. 
The  resultant  increase  in  size  and  complexity  of  the  reef  area  within  the  MPA,  relative  to  the 
observed  decrease  in  reference  sites  outside  the  MPA,  is  likely  to  be  significant  driver  in  the 
positive increase of taxa abundance and diversity over time (Davies et al., 2021). Over time, the 
greater  increase  in  fish  biomass  within  the  MPA,  compared  to  the  reference  sites,  indicates 
spillover effects could theoretically occur, subsequently benefitting the local fisheries outside the 
MPA, such as the displaced mobile demersal fisheries.  

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Within the stakeholder surveys, there was general agreement across all stakeholder groups 
that spillover could be occurring. While the scientists agreed that the number and diversity of 
fauna  within  the  MPA  had  increased,  the  fishers  also  agreed  that  their  catch  composition  had 
changed and there had been an uplift in the number of lobster, dover sole and scallop landings, 
but  also  a  downturn  in  crab  landings.  However,  there  was  uncertainty  whether  these  changes 
could be attributed to the MPA or external factors, such as climate change, national legislation or 
natural fish cycles. 

Interestingly, one of the key findings from the surveys was the difference in perception regarding 
MPA management. In particular, the absence of a dedicated management plan for the MPA and 
its location on the border of two different managing authorities raised concerns among the fishers, 
who deemed it ineffective due to disparities in regulations, such as enforcing different MCRS for 
catch  landings.  In  addition,  the  IFCAs  are  bound  by  legal  duties  to  focus  on  the  recovery  of 
designated “features” within MPAs, which then dictates fisheries management. The lack of a whole 
site  approach  of  the  Lyme  Bay  MPA,  enforced  by  one  entity,  could  be  seen  to  hinder  the 
effectiveness  of  the  site  due  to  the  lack  of  a  harmonised  approach  across  the  MPA.  This  is 
exacerbated by the fact the MPA was designated through a Statutory Instrument, which one fisher 
argued limited the flexibility of the management, closing the area to bottom towed fishing gear 
but subsequently increasing the fishing effort of static gear, particularly netting, inside the MPA.   

7  CONCLUSIONS 

Key findings from the study highlighted there is corresponding evidence from the literature review 
and interview analysis to suggest that over time, potential spillover effects could occur from the 
Lyme  Bay  MPA,  with  ongoing  scientific  research  projects  currently  focused  on  quantifying  the 
extent,  occurrence,  and  magnitude  of  these  spillover  effects.  Within  the  literature,  numerous 
studies  have  demonstrated  the  exclusion  of  demersal  gear  has  contributed  significantly  to  the 
continued recovery of epibenthic reef species, including slow growing sessile species (ross coral 
and nationally important pink sea fans), leading to significant increasing trends in mobile fauna 
biomass  over  time,  including  commercial  species  exploited  by  fishing  activities  which  are  still 
permitted in the MPA. Using the BACI approach, greater fish biomass was observed outside the 
MPA,  indicating  that  spillover  is  unlikely  to  be  occurring  at  this  time.  However,  the  increasing 
trend in total abundance was higher in the MPA, indicating the potential for spillover effects to be 
determined over a longer period of monitoring. This is supported by the stakeholder surveys which 
reflected  general  agreement  that  spillover  could  be  occurring,  informed  by  increased  fauna 
diversity within the MPA and changes in fisher catch compositions. However, uncertainty prevails 
whether  these  changes  are  attributed  to  the  MPA  or  external  factors  such  as  climate  change, 
national legislation adjustments, or natural fish cycles. 

Overall,  the  application  of  the  BACI  approach to  assess  spillover  from  the  Lyme  Bay  MPA  was 
successful. This was mainly due to the availability of baseline data collected before and after, at 
annual  intervals,  the  MPA’s  designation,  as  well  as  the  monitoring  of  multiple  reference  sites 
outside the MPA to assess the recovery of the epibenthic reef compared to sites which remained 
open  to  towed  demersal  fishing.  It  is  recommended  that  in  future  assessments  of  spillover, 
additional reference sites positioned further away from the MPA should be monitored to measure 
the magnitude of spillover, as well as using an equal number of sites in each treatment to ensure 
comparability of data between treatment areas. 

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8.  CASE STUDY REPORT: 

THE FLAMANVILLE PROTECTED AREA 

FRANCE – THE ENGLISH CHANNEL 

Lobster pots (or creel) in harbour storage © Pixabay 

Analysis of the potential spillover effects from 
the Flamanville Protected Area 

Paul Mosnier  

MRAG Europe

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TABLE OF CONTENTS 

1 
2 

3 
4 

5 

6 

7 
8 

EXECUTIVE SUMMARY ......................................................................................... 127 
BACKGROUND .................................................................................................... 127 
2.1 
Protected area designation ......................................................................... 127 
2.2  Halieutic and ecological significance ............................................................. 128 
AIMS AND OBJECTIVES ....................................................................................... 129 
METHODOLOGY .................................................................................................. 129 
4.1  Meta-analysis of monitoring projects and data related to spillover assessment

 ............................................................................................................... 129 
Larval abundance ...................................................................................... 131 
Population abundance (CPUE) and size ......................................................... 131 
4.2  Statistical analysis ..................................................................................... 131 
4.3  Before-After-Control-Impact assessment ...................................................... 132 
4.4  Stakeholder engagement surveys ................................................................ 132 
Identification of stakeholders ...................................................................... 132 
Development of the questionnaire ............................................................... 132 
Engagement of stakeholders ....................................................................... 132 
RESULTS ........................................................................................................... 133 
5.1  Meta-analysis of monitoring projects and data related to spillover assessment

 ............................................................................................................... 133 
Population abundance ................................................................................ 133 
 .................................................................................................. 137 
Size 
5.2  Stakeholder survey results ......................................................................... 141 
DISCUSSION ..................................................................................................... 141 
6.1  Assessment of Spillover ............................................................................. 141 
 .................................................................................................. 141 
CPUE 
Size (cephalothorax length (mm)) ............................................................... 142 
Larval abundance ...................................................................................... 143 
6.2  General lessons and assessment of the case study ........................................ 144 
Strengths and limitations of the data/methodology ........................................ 144 
Stakeholder engagement............................................................................ 144 
CONCLUSIONS ................................................................................................... 144 
REFERENCES ..................................................................................................... 145 

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LIST OF ABBREVIATIONS 

Term 

BACI 

CNPE 

Description 

Before After Control Impact 

Centre nucléaire de production d’électricité / nuclear power station 

CORPECUM  Comité Régional des Pêches et Cultures marines de Bretagne / Brittany Regional 

CPUE 

ISTPM 

MPA 

MSC 

NGO 

PPA 

SE 

Fisheries and Marine Cultures Committee 

Catch Per Unit of Effort 

Institut scientifique et technique des pèches maritimes / Scientific and technical 
institute for marine fisheries 

Marine Protected Area 

Marine Stewartship Council 

Non Governmental Organization 

Partially Protected Area 

Standard Error 

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1  EXECUTIVE SUMMARY  

The Zone de Cantonnement de Flamanville (also known as the Zone de Cantonnement de Dielette; 
hereinafter the Flamanville Protected Area), is a protected area situated on the Northwest coast 
of the Cotentin Peninsula in Northern France. The protected area was officially established in 2000 
with the aim to stall the declining population of lobsters (Homarus gammarus) and ensure the 
livelihoods of lobster fishers in this area. The area has been the attention of scientists from French 
state research authorities who have performed long term monitoring studies here since the 1980s, 
reporting  on  various  physico-chemical,  biological,  and  ecological  parameters.  Much  of  the 
research has been linked to monitoring of impacts from the nearby Centre nucléaire de production 
d’électricité (CNPE) de Flamanville, one of France’s largest nuclear energy plants, which interacts 
with the local marine habitat by using seawater in its functioning mechanisms and discharging 
effluents into the adjacent waters. 

The Flamanville Protected Area is unique in its designation as it is characterised by a complete 
no-entry zone within a wider partially protected area. This area is thus unique in its characteristics 
and a good candidate to investigate potential spillover effects. The current study aimed to analyse 
these potential spillover effects and to assess impacts on local fisheries.  

Given the relatively small size of the protected area (making it unsuitable for mobile pelagic and 
demersal finfish), and given its intended functioning in the conservation of lobsters, the authors 
focused their assessment of spillover impacts on four crustacean species (the European lobster 
Homarus gammarus, the brown crab Cancer pagarus, the velvet crab Necora puber and the spider 
crab Maja brachydactyla) which are of commercial importance and have been the subjects of the 
aforementioned  long  term  monitoring  projects.  The  impacts  of  spillover  on  the  fisheries  were 
assessed through (i) a comprehensive literature review and quantitative meta-analysis to identify 
potential impacts using several fishery data types, and (ii) stakeholder interviews to garner wider 
socio-economic perspectives.  

Although results were highly species specific (in addition to their variability due to potential biases 
in the sampling methodology), the meta-analysis indicated the potential occurrence of spillover 
effects (in terms of species abundance) for the European lobster (H. gammarus) and the spider 
crab (M. brachydactyla). These and other results could not be corroborated comprehensively with 
stakeholder opinions due to low levels of survey engagement. While there is evidence to support 
a spillover effect on lobsters and spider crabs, this does not automatically translate to positive 
benefits to fishers. Economic returns clearly depend on more than just an increase in abundance 
of the stocks, so other factors which influence the catch price would need to be considered. 

Overall, this case study provides clear evidence that assessment of spillover and impacts on local 
fisheries is highly species specific, and that interspecies interactions, knock on ecological impacts 
and wider socio-economic issues must be considered when assessing the effectiveness of marine 
protected areas.  

2  BACKGROUND  

2.1  Protected area designation 

The  Zone  de  Cantonnement  de  Flamanville  (officially  stated  as  the  Zone  de  Cantonnement  de 
Dielette  under  Arête  no⁰120/2019;  hereinafter  the  Flamanville  Protected  Area)  refers  to  a 
protected  marine  area  situated  adjacent  to  the  Flamanville  nuclear  power  station  (CNPE  de 
Flamanville) off the Northwest Coast of the Cotentin Peninsula in the department of La Manche 
within the Basse-Normandie region in  Northern  France. This protected  area  was established in 
2000 with the backing of the Comité Régionale de la Pêche Maritime – Normandie (the Regional 
Committee for Marine Fisheries – Normandy) following concerns about declining catches of lobster 
(Homarus gammarus) since the 1990s (Schlaich et al. (2019)).  

According to the legal regulations, this enforcement order prohibits all forms of ‘dormant’ (pots) 
and trawling fishing methods, with only hand lining for fish allowed. The area is classified as an 
IUCN Type IV (Nature Reserve) and a partially protected area (PPA) (Schlaich et al., 2019).  

Within the boundaries of the PPA, there is a complete no entry and no activity zone (measuring 
approximately  1.2  km2)  located  at  the  area  most  adjacent  to  the  CNPE  de  Flamanville.  Under 
Arête  No  51/2012,  all  forms  of  activity  (navigation,  stationing,  fishing,  anchoring,  swimming, 
scuba  diving  and  all  other  nautical  activities)  are  completely  prohibited.  This  was  likely 

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implemented for security purposes given the proximity to the nuclear power station, ultimately 
providing an additional ‘layer’ of protection for any species in this area, thus acting as a de facto 
refuge (Haines et al., 2018).  

Therefore, the Flamanville Protected Area is ultimately a PPA (area designated by the red outer 
line in Figure 1) containing an inner no entry zone and de facto Highly Protected Marine Area (pink 
area in Figure 1).  

Figure  1.  Location  within  France  (left)  and  limitations  (right)  of  the  Flamanville 
Protected Area. The outer red line indicates the limits of the Partially Protected Area, 
while the inner pink area indicates the complete no entry/no activity zone. The figure 
is a combination of the delineated zones in Arête No 51/2012 and Arête 120/201916. 

2.2  Halieutic and ecological significance 

The region has historically been home to one of the most commercially important shellfish and 
crustacean industries, contributing significantly to the total French annual landings of European 
lobster (Homarus gammarus), whelks (Buccinum  undatum) and brown crab  (Cancer  pagarus). 
Other commercially important species in this area include velvet crabs (Necora puber) and the 
spider crab (Maja brachydactyla). The northwest coast of the Cotentin Peninsula is a particularly 
important lobster nursery, contributing to supporting of stocks in surrounding area, and falls under 
the Marine Stewardship  Council  (MSC) Certified  lobster fishery (MSC  Fisheries Standard  v1.3), 
while  the  MSC  certified  whelk  fishery  also  encompasses  parts  of  this  area17.  Commercially 
important oyster and mussel farms are also located in the region.  

The marine area is located immediately adjacent to, on the western seaward side of, the CNPE de 
Flamanville. The nuclear power station draws sea water into its facility which is used in cooling 
operations  before  the  water  is  discharged  into  the  sea  again  through  an  exit  canal  at  its 
southeastern  point.  The  power  station  also  discharges  a  certain  amount  of  waste  through  a 
dispersal  pipeline  located  approximately  700m  offshore  to  west  of  the  power  station.  Despite 
treatment,  certain  amounts  of  radioactive  and  chemical  wastes  are  discharged  –  constant 
monitoring ensure that discharge does not reach environmentally impactful levels. This monitoring 
program results in the publication of an annual report by scientists at Ifremer (the French state 
scientific research group), the Surveillance écologique et halieutique du site électronucléaire de 
Flamanville (with the latest publicly available report published in 2017, referenced throughout this 
report  as  Le  Gac  et  al.  (2018)).  Monitoring  of  waters  occurs  frequently,  and  the  latest  data 
indicates that waters in the  region are  of  ‘good quality’ (Agence  Eau Seine Normandie, 2022), 

16https://www.fnpsa-normandie.net/wp-content/uploads/2021/05/fbs-NwomcFEc7Z-wSYitJeRDZu8.png 
17Although  the  Zone  de  Cantonnement  de  Flamanville  is  not  technically  located  in  Granville  Bay  (and  as  such 
would not come under the MSC Certified Granville Bay whelk fishery), the MSC notes that the certified fishery 
extends from Granville (to the south of Flamanville) and the Cap de la Hague (to the north of Flamanville). 

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with Le Gac et al. (2018) reporting no recorded effects of inputs from the CNPE de Flamanville on 
crustacean populations in the immediate vicinity of the region. This area supports a large diversity 
of flora and fauna including several cetacean species. 

3  AIMS AND OBJECTIVES 

The  overarching  objective  is  to  provide  a  stronger  understanding  of  whether  the  Flamanville 
Protected Area is generating ecological and/or economic benefits to commercial fisheries through 
spillover. 

This report set out specifically with two main aims: 

(i)  Conduct  a  review  of  studies  that  have  attempted  to  assess  fishery  spillover  effects  in  the 
Flamanville region and analyse the suitability of indicators as evidence spillover effects.  

(ii)  Conduct  stakeholder  engagement  surveys  to  gather  opinions  and  perceptions  of  key 
stakeholders in the area. The success of MPAs will ultimately depend heavily on the engagement 
of  stakeholders  in  the  process  of  establishment  and  management  of  the  protected  zones,  and 
thus it is critical to understand the direct (and perceived) impacts that these zones can have. 

4  METHODOLOGY 

This work consisted of two main parts including (1) a meta-analysis of data collected from publicly 
available scientific articles, reports and other grey literature, and (2) identification and surveying 
of key stakeholders. 

4.1  Meta-analysis  of  monitoring  projects  and  data  related  to  spillover 

assessment 

Ifremer,  the  French  state  marine  research  organisation,  has  been  conducting  sampling  in  this 
region since the 1970s, and many of the recorded parameters are applicable in the assessment 
of spillover. Two main studies (Le Gac et al., 2018 and Schlaich et al., 2019) were reviewed in 
this report (Table 1), and the data gathered was used to perform a meta-analysis to identify and 
assess potential spillover indicators in the study area.  

Le Gac et al. (2018) is the most recent publicly available annual monitoring survey which firstly 
records ecological and environmental samples collected at 4 points (Point canal, point rejet, point 
reference, point 3) within and outside the protected area. Secondly, the report provides data on 
the size (measured as the cephalothorax length (mm)) and abundance (the catch per unit effort 
of individuals) of the crustaceans Homarus gammarus (European lobster), Cancer pagarus (the 
brown  crab),  Necora  puber  (the  velvet  crab)  and  Maja  brachydactyla  (the  spider  crab)  at  15 
different sites, as well as the larval abundance of H. gammarus and M. brachydactyla. Figure 2 
below illustrates the sampling sites of this report.  

Schlaich et al. (2019) report the same (but more recently updated) data as the second part of Le 
Gac et al. (2018) and consider an additional sampling point within the protected zone (point 16) 
(Figure 3).  

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Figure  2.  Illustration  of  the  sampling  sites  of  larval  abundance  (zooplankton), 
microbiology and hydrology (Point canal, Point rejet, Point reference, Point 3) and the 
crustacean sampling sites 1-15 (Figure adapted from Le Gac et al. (2018)).  

Figure  3.  Locations  (1-16)  where  crustacean  samples  were  collected,  noting  the 
additional  sampling  point  (point  16).  The  Zone  de  Cantonnement  is  delimited  by  the 
area surrounded by the black line (noting this is a rough outline of the area) (adapted 
from Schlaich et al. (2019)). 

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Table 1. Summary of the main data available  and assessed as a spillover indicator in 
the case study region. 

Fishery Data Type Analysed 

Species 

Source 

Larval abundance 

Size (cephalothorax length, orbital or 
transversal width depending on 
weight (g)) 

Catch Per Unit Effort 

Homarus gammarus 
Maja brachydactyla 
Homarus gammarus 
Cancer pagarus 
Necora puber 
Maja brachydactyla 
Homarus gammarus 
Cancer pagarus 
Necora puber 
Maja brachydactyla 

Le Gac et al. (2018) 

Le Gac et al. (2018) 
Schlaich et al. (2019) 

Le Gac et al. (2018) 
Schlaich et al. (2019) 

Larval abundance  

The four locations (Point canal, Point rejet, Point reference, Point 3) were surveyed twice a year 
since 1987, and since 1997 are now sampled four times per year. M. brachydactyla samples were 
collected using a submerged bongo net (following the methodology of Smith & Richardson, 1997) 
brought to the surface at a speed of 2 knots. H. gammarus were collected using a neuston net 
(following the methodology of Nichols et al. 1980) along a line pulled at a speed of 2 knots. All 
collected  samples  were  stored  in  2  litre  flasks  containing  0.9%  formaldehyde  solution  for 
conservation.  For  each  species,  the  number  of  larvae  at  each  stage  of  development  (3  for  M. 
brachydactyla,  4  for  H.  gammarus)  were  counted  under  a  microscope,  and  the  number  of 
individuals per volume of sampled water (extrapolated to number of individuals per m3 of water) 
was calculated.  

Population abundance (CPUE) and size  

Size and abundance of the crustacean species have been reported in this area since 1987 during 
a twice-annual campaign (June and September) whereby 20-30 pots are dropped at each of the 
16 points in Figure  3. Over  a 4-day period, pots are  lifted, and  the  number of each species is 
counted. For each species of crustacean, the number of individuals and size (mm) (cephalothorax, 
orbital or transversal length depending on the species) are recorded. The former is then used to 
calculate the Catch Per Unit Effort (CPUE; the number of individuals per 80 pots) and the latter 
to calculate the weight (g) using a length-weight formula developed by local fisheries biologists18. 

4.2  Statistical analysis  

To compare data across the different areas (sampling site location within or outside the protected 
area), the time period (before or after the implementation of the protected area), the sampling 
point and the sampling campaign, a generalised linear model was adapted to the specific data. 
Zone and time period were considered fixed effects, while sampling point and sampling campaign 
were considered variables. For cephalothorax length (mm), an adjusted linear mixed model was 
used to assess variance. CPUE was analysed using an adjusted linear mixed model with a log link 
and negative binomial distribution. A Chi2 test was conducted to test for statistically significant 
differences  between  samples  before  and  after  implementation  of  the  protected  area  for  each 
species,  for  both  size  (cephalothorax  length  (mm))  and  CPUE.  Data  were  analysed  using  R 
statistical programming software.  

18 This calculation was developed by biologists at the Comité Régional des Pêches et Cultures marines de Bretagne 
(CORPECUM), the Comité Local des Pêches de Blainville and the Stations ISTPM de Roscoff et de Ouistreham in 
1983 and has been used in the Manche Ouest region since. The equation is W=aLcb, where W is the weight (g), 
Lc = cephalothorax length/width.  

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4.3  Before-After-Control-Impact assessment 

Due  to  the  data  availability,  a  Before-after-control-impact  (BACI)  assessment  could  only  be 
conducted  using  the  abundance  (CPUE)  and  size  (cephalothorax  length  (mm))  as  reported  in 
Schlaich et al. (2019) for each of the four species. A BACI assessment using larval abundance 
and weight (g) was not conducted.  

4.4  Stakeholder engagement surveys 

Identification of stakeholders 

Stakeholders were categorized according to four main groups: (1) commercial and recreational 
fishers, (2) fishery managers and government authorities, (3) scientists and (4) environmental 
NGOs. It was determined that this classification would cover a diversity of stakeholders and ensure 
different opinions were heard. 

Overall,  7  scientists  (from  two  different  research  organisations),  2  environmental  NGOs,  2 
commercial and recreational fishers (2 different representative groups through which fishers could 
be  engaged)  and  8  fisheries  managers/governing  authorities  were  contacted  regarding  the 
survey. 

Development of the questionnaire 

The  questionnaire  consisted  of  approximately  20  questions  which  were  designed  to  elicit 
stakeholder views and experiences on different study aspects. Questions were structured in both 
open-ended and closed form. Open-ended questions aimed to capture stakeholder opinions more 
qualitatively, such as their general awareness of regulations and management measures of the 
protected area. The closed answer questions were generally required either a YES or NO response 
or  required  the  respondent  to  select  an  answer  from  a  Likert  scale  (e.g.:  Strongly 
Agree/Agree/Neutral/Disagree/Strongly  Disagree),  which  ensured  that  answers  could  be 
quantified. The questionnaire was translated to French and uploaded to an online questionnaire 
platform. 

The  questionnaire  consisted  of  four  categories,  which  were  adapted  slightly  depending  on  the 
category of stakeholder (see Annex 4), and consisted of:  

a.  Respondent  information.  Name,  institution,  and  the  type  of  stakeholder  category  they 

belonged to. 

b.  Background  information.  Collected  in  order  to  understand  more  about  the  respondent  and 
their use of the MPA. Questions included knowledge of when the MPA was established, the 
type of restrictions in place and how long the stakeholder has been associated with the MPA 
either through research, fishing, or management. 

c.  Fishery impacts of MPAs. Perceptions of the socio-economic impacts of spillover from the MPA. 
Stakeholders were asked to state whether the designation of an MPA / protected area has led 
to an increase in revenues for fishers, whether the fishing community in the area feel their 
fisheries livelihoods are more secure after the MPA was established, and the extent to which 
they believe spillover from the MPA has influenced the catch composition in adjacent fishing 
grounds. 

d.  MPAs  as  management  tools.  Perceptions  on  whether  MPAs  are  conservation  or  fisheries 
management tools. Stakeholders were asked to state whether their local MPA was acting as 
a conservation tool, a fisheries management tool or both. Other questions under this section 
required stakeholders to state their agreement / disagreement on whether the establishment 
of  MPAs  is  an  effective  conservation  strategy  to  support  fish  populations  and  commercial 
fisheries  in their  area.  Respondents  were  also  asked  to  indicate  what  factors  they  thought 
were contributing to spillover effects. 

Engagement of stakeholders 

Key stakeholders were identified through the  scientific and grey literature, word of mouth and 
general  internet  searches  using  the  search  terms  “Flamanville  MPA”,  “spillover  Flamanville”, 
“fisheries spillover Flamanville”, “spillover Manche Ouest”, “Flamanville Fisheries”. Initial contact 
was  established  with  stakeholders  via  email  and  later  by  phone.  Potential  respondents  were 
provided with a summary of the project and were invited to participate in the survey through a 
video call. Upon confirmation, respondents were invited to an online conference call where the 

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session was recorded so the answers provided could be reviewed. Participants were made aware 
of privacy policies and confidentiality agreements and were asked to state their permission for 
interviews to be recorded. The respondent was asked the questions and responses were noted by 
the interviewer. In cases where stakeholders did not have the availability or desire to participate 
in an online call, they were sent a link to the survey to complete directly. 

5  RESULTS  

5.1  Meta-analysis  of  monitoring  projects  and  data  related  to  spillover 

assessment 

Population abundance 

Homarus gammarus (European Lobster)  

Results indicate an increasing trend of lobster abundances both inside and outside the protected 
zone since 2000 (Figure 4) and is corroborated by statistically significant increases (p < 0.001) 
in CPUE before and after implementation of the protected zone, both inside and outside across 
both sampling periods (Figure 5). 

Figure 4. Abundance (CPUE) (number of individuals per 80 pots) of European lobsters 
(H. gammarus) between 1987 and 2017 inside and outside the protected area in June 
(left) and September (right). The  red dotted line  indicates total abundances, and the 
blue  dotted  line  indicates  the  year  of  implementation  of  the  protected  area  in  2000 
(adapted from Le Gac et al. 2018). 

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Figure  5. Abundance  (mean  CPUE  ±  SE)  of  European  lobsters  (H.  gammarus)  in  June 
(left)  and  September  (right)  inside  and  outside  the  protected  area  sampling  location 
before (red) and after (green) its implementation (adapted from Schlaich et al. 2019) 

Cancer pagarus (Brown crab) 

Figure 6  illustrates  a  much  higher  abundance  of  individuals  outside  and  a  marked  decrease  in 
abundance inside of the protected area following implementation of the protected zone, but results 
were not statistically significant (Figure 7).  

Figure 6. Abundance (number of individuals per 80 pots) of brown crab between 1987 
and 2017 inside and outside the protected area in June (left) and September (right). 
The red dotted line indicates total abundances, and the blue dotted line indicates the 
year of implementation of the protected area in 2000 (adapted from Le Gac et al. 2018). 

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Figure 7. Abundance (mean CPUE ± SE) of brown crab (Cancer pagarus) in June (left) 
and September (right) inside and outside the protected area sampling site before (red) 
and after (green) its implementation (adapted from Schlaich et al. 2019). 

Necora puber (Velvet crab) 

Abundance of individuals has been declining since the implementation of the protected zone at 
sampling  sites  within  the  zone  (Figure  8)  with  a  slight  non-significant  increase  in  populations 
outside the zone (Figure 9). 

Figure 8. Abundance (CPUE) of velvet crab (N. puber) between 1987 and 2017 inside 
and outside the protected area in June (left) and September (right). The red dotted line 
indicates  total  abundances,  and  the  blue  dotted 
indicates  the  year  of 
implementation of the protected area in 2000 (adapted from Le Gac et al. 2018). 

line 

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Figure 9. Abundance (mean CPUE ± SE) of velvet crab (Necora puber) in June (left) and 
September (right) Inside and outside the protected area sampling site before (red) and 
after (green) its implementation (adapted from Schlaich et al. 2019). 

Maja brachydactyla (Spider crab) 

Figure  10  and  Figure  11  illustrate  a  general  trend  toward  increasing  populations  of 
M. brachydactyla  both  inside  (p  <  0.001)  and  outside  (p  <  0.001)  the  zone  following 
implementation of protection.  

Figure  10.  Abundance  (number  of  individuals  per  80  pots)  of  spider  crab  (M. 
brachydactyla) between 1987 and 2017 inside and outside the protected area in June 
(left) and September (right). The  red dotted line  indicates total abundances, and the 
blue  dotted  line  indicates  the  year  of  implementation  of  the  protected  area  in  2000 
(adapted from Le Gac et al. 2018). 

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Figure 11. Abundance (mean CPUE ±SE) of spider crab (M. brachydactyla) in June inside 
and  outside  the  protected  area  sampling  site  before  (red)  and  after  (green)  its 
implementation (adapted from Schlaich et al. 2019). 

Size  

Homarus gammarus (European lobster) 

Following  implementation  of  the  protected  zone  in  2000,  average  size  (cephalothorax  length 
(mm)) (Figure 12) of lobsters increased, but a decreasing trend in size is seen between 2006 – 
2017 for all times of the year. 

Figure 12. Average size (cephalothorax length (mm)) (mean ± SE) of European lobsters 
(H.  gammarus)  between  1985  –  2017  in  June  (left)  and  September  (right)  (adapted 
from Le Gac et al. 2018). 

Despite this downward trend, the average size (cephalothorax length (mm)) of lobsters increased 
significantly inside the protected zone (p < 0.001), while it has decreased outside the protected 
zone across both months (Figure 13).  

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Figure 13. Average cephalothorax length (mm) (mean ± SE) of European lobsters (H. 
gammarus) in June (left) and September (right) inside and outside the protected area 
sampling site before (red) and green (after) its implementation (adapted from Schlaich 
et al. 2019). 

Cancer pagarus (Brown crab) 

Brown  crab  size  (cephalothorax  length  (mm))  appears  to  have  peaked  between  1993  –  1995. 
Cephalothorax length appears to have been on a downward trajectory across all sampled months 
between 1995 and 2017 (Figure 14). Since the implementation of the protected zone, average 
cephalothorax length of crabs caught inside the zone has increased strongly, while outside the 
zone, average size has decreased (Figure 15), though non-significantly.  

Figure  14.  Average  size  (mean  cephalothorax  length  (mm)±  SE)  of  brown  crab  (C. 
pagarus) between 1985 – 2017 in June (left) and September (right) (adapted from Le 
Gac et al. 2018). 

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Figure 15. Average size (cephalothorax length (mm)) (mean ± SE) of brown crab (C. 
pagarus) in September inside and outside the protected area sampling site before (red) 
and green (after) its implementation (adapted from Schlaich et al. 2019) (data for June 
was not available). 

Necora puber (Velvet crab) 

Velvet crab size (in terms of cephalothorax length) (Figure 16) on average, has been decreasing 
since  sampling  began  across  all  the  sampling  sites  during  both  sampling  periods.  Significant 
decreases  (p  <0.001)  within  and  outside  of  the  protected  area  sampling  site  following 
implementation of protection are seen at both sampling periods (Figure 17).  

Figure 16. Average size (cephalothorax length (mm))  (mean ± SE) of velvet crab (N. 
puber) between 1985 – 2017 in June (left) and September (right) (adapted from Le Gac 
et al. 2018). 

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Figure 17. Average size (cephalothorax length (mm)) (mean ± SE) of velvet crab (N. 
puber)  in  June  (left)  and  September  (right)  inside  and  outside  the  protected  area 
sampling site before (red) and green (after) its implementation (adapted from Schlaich 
et al. 2019). 

Maja brachydactyla (Spider crab) 

Average  size  (cephalothorax  length  (mm))  (Figure  18)  of  spider  crabs  decreased  between 
beginning of sampling times before levelling off and seemingly remaining stable until 2017, when 
the  average  size  appears  to  have  peaked  again.  Within  the  protected  area  sampling  site,  the 
average cephalothorax length has decreased significantly (for the sampling month of September 
at least) (p <0.001), while a smaller average decrease has also been seen outside the protected 
area following implementation of protection in 2000 (Figure 19)  

Figure 18. Average size (cephalothorax length (mm)) (mean ± SE) of spider crab (M. 
brachydactyla) captured between 1985 – 2017 across all sampling sites in June (left) 
and September (right) (adapted from Le Gac et al. 2018). 

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Figure 19. Average size (cephalothorax length (mm)) (mean ± SE) of spider crab (M. 
brachydactyla) in September inside and outside the protected area sampling site before 
(red) and green (after) its implementation (adapted from Schlaich  et al.  2019) (data 
for June was not available). 

5.2  Stakeholder survey results 

Of the total number of stakeholders contacted (N = 23 ), only one was successfully engaged. The 
scientific stakeholder, who authored the paper Schlaich et al. (2019) referred to throughout this 
paper,  provided  a  corroboration  of  the  results  presented  in  the  paper,  with  some  additional 
insights, perspectives and opinions on the study and to spillover more generally. A key insight 
provided  was  that  pots  have  a  maximum  capacity  of  approximately  6  crustaceans,  and  thus 
results of species densities may be underestimated.   

6  DISCUSSION 

6.1  Assessment of Spillover  

Based on a BACI approach, an assessment was carried out using the data (in section 5 Above) to 
assess  whether  the  results  showed  the  occurrence  of  spillover.  Both  the  fishery  data  types 
abundance  (measured  in CPUE)  and  size  (measured  as  the  cephalothorax  length  (mm)),  were 
used. The author of this report  notes that the changes (delta) were not quantified numerically 
due to the unavailability of raw data for analysis but were based on observations of data in Figures 
5, 7, 9, 11, 13, 15, 17 and 19 (above) from Schlaich et al. (2019).  

CPUE 

A summary of the relevant information to assess spillover occurrence using the BACI method in 
terms of species abundance can be seen in Table 2. The abundance of lobsters increased both 
inside  and  outside  the  protected  area  following  implementation  of  protection,  with  a  stronger 
increase seen within the  protected  area. This indicates that there may be a level of protection 
conferred  on  the  populations  inside,  thus  the  potential  for  spillover  to  be  occurring.  This  was 
consistent during both sampling periods.  

Populations of M. brachydactyla demonstrated the same trend as H. gammarus, with an overall 
increase  in  populations  following  implementation  of  the  protected  area.  The  data  demonstrate 
that  some  level  of  protection  is  being  afforded,  and  thus  an  augmentation  of  abundance,  and 
potential  spillover  of  these  populations  is  occurring.  Data  was  only  available  for  June,  which 
reflects  possible  confounding  variables  of  seasonality  and  species  behaviour  which  were 
mentioned  during  the  scientist  stakeholder  interview.  This  species  demonstrates  a  seasonal 

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migration  and  is  generally  quite  elusive  in  comparison  to  H.  gammarus,  while  data  seem  to 
indicate a possible spillover in terms of abundance.  

Both  N.  puber  and  C.  pagarus  abundances  declined  inside  the  protected  area  but  showed  an 
increase in abundance  outside the zone  following  protected area  implementation. This is likely 
due to an effect of competition driving them out of the protected area as it became dominated by 
H. gammarus and M. brachydactyla. This was consistent across both sampling periods. This theory 
was supported by the scientist  interviewed,  who  outlined the ecological impacts that a sudden 
change in protection level could have and demonstrates how anthropogenic influences ultimately 
lead to changes in species ecology.  

Table 2. BACI determination using CPUE as a spillover indicator (Δ MPA = the change 
in CPUE at internal sampling sites after implementation of the protected area; Δ Ref = 
the change in CPUE at reference point after implementation of the protected area). 

Species  Month 

Reference 
Figure 

Δ MPA 

Δ Ref 

Scenario 
Description 

Pro-
tection? 

Spillover
? 

H. 
gammar
us 

June 

Figure 5 

Strong 
increase 

Increase 

September 

Figure 5 

Strong 
Increase 

Increase 

M. 
brachyda
ctyla 

June 

Figure 11 

Strong 
Increase 

Increase 

September 

n/a 

n/a 

N. puber 

June 

Figure 9 

Decrease 

Increase 

September 

Figure 9  

Decrease 

Increase 

C. 
pagarus 

June 

Figure 7 

Decrease 

Increase 

September   Figure 7 

Decrease 

Increase 

Yes 

Potentially 

Yes 

Potentially 

Yes 

Potentially 

No 

No 

No 

No 

No 

No 

No 

No 

Population 
abundance 
increased in 
both 
locations, a 
stronger 
increase 
inside 

Population 
abundance 
increased in 
both 
locations, a 
stronger 
increase 
inside 

Population 
abundance 
increased in 
both 
locations, a 
stronger 
increase 
inside 

Decrease in 
CPUE in MPA, 
increase 
outside. 

Decrease in 
CPUE in MPA, 
increase 
outside 

Decrease in 
CPUE in MPA, 
increase 
outside. 

Decrease in 
CPUE in MPA, 
increase 
outside 

Size (cephalothorax length (mm)) 

Table 3 provides a summary  of  the  key  information  used to assess the  occurrence  of spillover 
using size (cephalothorax length  (mm)) as a potential indicator. Average size of  H. gammarus 
sampled within the protected area showed a strong increase following protection implementation, 

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and a decrease outside of the protected area. Some level of protection is granted, but clearly no 
migration of larger individuals outside the protected area is occurring at either sampling period. 

M. brachydactyla populations, in June (the only month of available data) significantly decreased 
in  average  size  in  the  internal  sampling  area  after  protection  implementation  and  decreased 
moderately outside the protected area. One must note there is a potential confounding variable 
caused by the species and its migratory/mobile behaviour, which as the author of the scientific 
study admitted, may have influenced the data somewhat.  

N. puber average size decreased strongly across both sampling periods in both sampling locations 
following the implementation of the protected area.  

Where data were available for the month of June, C. pagarus size decreased moderately within 
the internal sampling area, while populations increased in average size in areas outside the area 
after protection implementation.  

Table 3. BACI determination using the size (cephalothorax length (mm)) as a spillover 
indicator (Δ MPA = the change in cephalothorax length at internal sampling site after 
implementation of the protected area; Δ Ref = the change in cephalothorax length at 
reference point after implementation of the protected area) 

Species 

Month 

Reference 
Figure  

Δ MPA 

Δ Ref 

Scenario 
Description 

H. 
gammarus 

June 

Figure 13 

Strong 
increase 

Decrease 

September 

Figure 13 

Strong 
increase 

Decrease 

Lobster size 
increased strongly 
inside the zone, 
but decreased 
outside 

Lobster size 
increased strongly 
inside the zone, 
but decreased 
outside 

Pro-
tection 
? 

Spillov
er ? 

Yes 

No 

Yes 

No 

M.brachyd
actyla 

June 

Figure 19 

Strong 
decrease 

decrease   Spider crabs got 

No 

No 

September 

N. puber 

June 

Figure 17 

n/a 

n/a  

Strong 
decrease 

Strong 
decrease 

September 

Figure 17  

Strong 
decrease 

Strong 
decrease 

C. pagarus 

June 

Figure 15 

decrease 

increase 

September  

Figure 15 

n/a 

n/a 

Larval abundance  

much smaller 
inside the zone, 
and smaller 
outside 

A strong decrease 
in size both in and 
out 

A strong decrease 
in size both in and 
out 

Crabs got smaller 
inside, but larger 
outside 

No 

No  

No 

No 

No 

No 

Due to a lack of raw data, assessing spillover using larval abundance as an indicator type could 
not  be  fully  conducted.  The  data  assessed  indicate  greater  abundance  of  larvae  of  both  M. 
brachydactyla and H. gammarus along an increasing gradient further from the sampling points 
within  the  protected  area.  However,  no  statistical  analysis  could  be  conducted  due  to  the 
unavailability of raw data collected in each sampling location to determine BACI.  

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6.2  General lessons and assessment of the case study 

Overall, this case study demonstrates how a protected area can confer protection and 
possible  spillover  effects  but  provides  a  clear  example  of  the  species  specificity  and 
parameters to consider in the assessment of potential effects on local fisheries.  

Strengths and limitations of the data/methodology  

While access to raw data sets would have permitted the authors to provide further analysis and 
draw more accurate conclusions, the data provided from the long-term monitoring projects in the 
Flamanville area (described by IFREMER scientists through Schlaich et al. (2019) and Le Gac et 
al. (2018)) are strong to support an accurate assessment of spillover through a BACI approach. 
Two different data types (abundance (CPUE) and size (mm) allowed a bidimensional assessment 
of  spillover.  Having  been  conducted  since  the  1980s,  the  sampling  programs  conducted  in 
Flamanville  provide  a  comprehensive  and  long-term  data  set  which  provide  for  more  accurate 
deductions. Considering the effects of spillover might only be visible and/or quantifiable 10 years 
after  implementation  (Smallhorn-West  et  al.  2020),  the  long  timeframe  here  provides  a  clear 
picture of what has happened on a long-term basis. Additionally, multiple sampling sites inside 
and  outside  the  protected  area  provide  a  large  sample  size  which  supports  deductions  and 
inferences.  

The  sampling  methodology  is  crustacean-specific  in  its  design  (the  small  area  is  suited  to  the 
relative sedentary nature of crustaceans, when compared to pelagic fish for example), and thus 
extrapolating results to more mobile species would not be accurate. Additionally, as highlighted 
by  the  scientist  interviewed,  possible  biases  exist  in  data  collection  which  may  result  in 
underestimations of species densities. 

Stakeholder engagement 

Despite multiple reminders via email and phone calls, the authors noted difficulties in engaging 
stakeholders in this area. One of the common responses was a lack of awareness of the existence 
of this protected area, as well as confusion as to the location and/or designation of the area.  

It was not clear to the author who was responsible for the management of the protected area. 
Several government bodies/agencies were contacted, but the authors were often told that it was 
not under the jurisdiction of the local government there.  

Fisher  representatives  were  hesitant  to  provide  responses  and  concerns  were  raised  by  them 
about  the  use  of  the  fisher’s  data  and  how  the  survey  might  impact  them.  Although  initially 
engaged and receptive to the authors explanations of data management and clear outlining of the 
aims and objectives of the study, the main fisher’s organisation in the area became disengaged.  

Further discussion and interview with a wider range and greater number of stakeholders would 
be needed to validate the results of the meta-analysis and to provide comprehensive insight to 
the wider socio-economic implications of spillover and protected areas.  

7  CONCLUSIONS  

Answers to the question of whether spillover is occurring and/or if it is having an effect on fisheries 
in the Flamanville Protected Area are not black and white. While there is strong evidence to 
support a spillover effect on lobsters and spider crabs (in terms of an increase in species 
abundance), this does not automatically translate to positive benefits to fishers. Economic 
returns clearly depend on more than just an increase in abundance of the stock, so other factors 
which influence the catch price would need to be considered (market demand, fisher operating 
costs, taxes). Moreover, the positive effects that the protected area has on one species may be 
outweighed  by  negative  impacts  on  others.  In  Flamanville,  while  H. gammarus  appear  to  be 
benefiting  from  the  implementation  of  protection,  C.  pagarus  stocks  have  been  negatively 
impacted. Could possible increased revenue from higher lobster abundance be simply outweighed 
by the converse in relation to brown crabs? The case study also demonstrates potential impacts 
of seasonality which can influence species’ presence, abundance and/or activity, adding further 
to the clear species specificity of a protected area. Considering these variables demonstrate that 
the occurrence of spillover, and whether it has an impact on fishers, is somewhat fluid.  

In terms of future management of protected  areas,  the  Flamanville  Protected  Area  case  study 
demonstrates the need to assess potential knock-on effects (mostly ecological, which can lead to 
other socio-economic impacts), which should be closely considered before, during and after MPA 

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implementation. For example, recent news reports19 have highlighted problems of the increasing 
spider  crab  populations  on  mussel  farms  in  the  Manche  region:  while  we  can’t  say  that  the 
protected  area  in  Flamanville  is  directly  responsible  for  this,  changes  in  the  ecology  and/or 
behaviour of a species can cause wider impacts. This indicates that MPA implementation requires 
caution considering the potential to influence the abundance, ecology and thus behaviour of an 
individual species.  

8  REFERENCES  

Haines, R., Verstraeten, Y., Papadopoulou, L., Hattam, C., Pantzar, M., Russi, D., Chaparro, L., Hoffman, J., 
Van Dijk, E., Vindigni, G., Peri, I., David, M., (2018). Study on the economic benefits of marine protected 
areas  -  Task  5  case  studies  -  Final  report,  Publications  Office  of  the  European  Union,  p.  312.  DOI: 
10.2826/243122. 

Le Gac, C., Antajan, E., Courtay, G., Hernandez Farinas, T., Lamort, L., Loots, C., Rabiller, E., Ropert, M. & 
Schlaich, I. (2018) Surveillance écologique et halieutique du site électronucléaire de Flamanville. Année 
2017.  RST 
Technique 
(ODE/LITTORAL/LER/BO/18.01) Ifremer, France.  

de  Recherche  Scientifiques 

de  Resultats 

-  Rapports 

et/ou 

Nichols, J.H., Bennet, D.B., Lawrence, A. (1980). A study of some problems relating to quantitative sampling 
of lobster larvae, Homarus gammarus (L.) - Cons. Inter. Explor. Mer, Comité des Crustacés, L: 14, 8 pp 
(mimeo). 

Schlaich,  I.,  Ernande,  B.  &  Normand,  J.  (2019)  Etude  de  l’effet  du  cantonnement  de  Flamanville  sur  la 
communauté des crustacés. RST - Rapports de Résultats de Recherche Scientifiques et/ou Technique (RST 
/RBE/HMMN/LRHPEB-19.04) Ifremer, France.  

Smallhorn-West, P.F., Weeks, R., Gurney, G. & Pressey, R, L. (2020). Ecological and socioeconomic impacts 
of marine protected areas in the South Pacific: assessing the evidence base. Biodiversity Conservation, 
29: 349–380. 

Smith, P.E., Richardson, S. (1977). Standard techniques for pelagic fish egg and larval surveys. FAO Fisheries 

Technics Pap. 175:100 pp. 

19https://www.ouest-france.fr/mer/peche/proliferation-des-araignees-de-mer-dans-la-manche-leffarouchement-est-

desormais-autorise-55603f08-15cb-11ee-ae57-25b1d1d54a03 

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9.  CASE STUDY REPORT: 

THE ÉCRÉHOUS AND THE MINQUIERS 

JERSEY – THE ENGLISH CHANNEL 

Jersey, Channel islands. © Pixabay 

Analysis of potential spillover effects around the 
Écréhous and the Minquiers Marine Protected Areas in 
Jersey, Channel Islands 

William Peat 

MRAG Europe 

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TABLE OF CONTENTS 

1 
2 
3 
4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ......................................................................................... 148 
BACKGROUND .................................................................................................... 148 
AIMS AND OBJECTIVES ....................................................................................... 151 
METHODOLOGY .................................................................................................. 152 
4.1 
Literature Review ...................................................................................... 152 
4.2  Stakeholder survey .................................................................................... 152 
RESULTS ........................................................................................................... 153 
5.1 
Literature Review ...................................................................................... 153 
5.2  Stakeholder survey .................................................................................... 155 
Ecological changes after MPA designation ..................................................... 155 
Changes to catches after MPA designation .................................................... 155 
Fisheries management issues...................................................................... 156 
Spillover  .................................................................................................. 156 
DISCUSSION ..................................................................................................... 157 
CONCLUSIONS ................................................................................................... 158 
REFERENCES ..................................................................................................... 160 

LIST OF ABBREVIATIONS 

Term 

BACI 

BoGA 

BRUV 

CPUE 

LPUE 

MLS 

MPA 

NGO 

Description 

Before After Control Impact  

Bay of Granville Agreement 

Baited Remote Underwater Video 

Catch Per Unit Effort 

Landings Per Unit Effort 

Minimum Landing Size 

Marine Protected Area 

Non-Governmental Organisation 

NPPZ 

No Parlour Pot Zone 

NTZ 

TCA 

TAC 

iVMS 

VMS 

No-take Zone 

Trade and Cooperation Agreement  

Total Allowable Catch 

Inshore Vessel Monitoring System 

Vessel Monitoring Systems 

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1  EXECUTIVE SUMMARY  

In 2017, the Government of Jersey designated two  marine protected areas (MPAs) within their 
territorial waters. One to the Northeast of the island, the  Écréhous, and one to the South, the 
Minquiers.  Both  MPAs  protect  relatively  shallow  water,  consisting  of  a  matrix  of  rocky  reefs, 
sandbanks, and intertidal areas as well as biogenic habitats in the form of seagrass and maerl 
beds. The Minquiers MPA covers an area of 47.5 km2 while the Écréhous covers a much smaller 
area of 15 km2. Both MPAs ban the use of any mobile fishing gear in their boundaries, with some 
separate  Parlour  Pot  restrictions  in  place  in  parts  of  their  waters  and  help  Jersey  government 
towards its goal of 30% protection of its marine space by 2030. Despite the ban on mobile fishing, 
static  fishing  is  permitted  along  with  hand  diving  for  scallops.  This  case  study  assesses  the 
potential for fisheries and ecological spillover of commercial target species from both the Minquiers 
and the Écréhous MPAs into their surrounding waters. 

Typically, studies investigating the occurrence of spillover will apply a Before After Control Impact 
(BACI) approach. Here, data from sites within and outside the MPAs (control sites) are compared 
across years before and after the designation of the MPAs. This case study could not access any 
raw data from before the designation of the MPAs. For this case study, a literature review of all 
relevant studies that might indicate evidence of spillover was combined with a stakeholder survey.  

Given the recent designation of both MPAs, relatively few studies have been completed on them. 
This  meant  the  literature  review  needed  to  be  supplemented  by  more  extensive  stakeholder 
engagement,  including  a  visit  to  Jersey  to  interview  those  closest  to  the  MPA  who  had  not 
responded to the remote survey. The literature review found no direct evidence of spillover, with 
abundances of crustaceans above Minimum Landing Size (MLS) generally declining at both MPAs. 
Typically,  crustacean  abundances  were  comparable  to  historical  surveys  that  have  shown 
declining stocks,  indicating  these  species (lobster,  brown crab, and spider crab)  may be being 
overexploited. However, high abundances of below MLS lobsters were seen at the  Écréhous as 
well as low abundances of above MLS lobsters. This may be evidence that the  Écréhous MPA is 
helping the area to act as a nursery for lobsters. A Baited Remote Underwater Video (BRUV) study 
assessing  spider  crab  abundance  also  reported  higher  abundances  at  open  control  sites  than 
within the Écréhous MPA. This may be evidence that potting vessels are preferentially targeting 
the MPAs as no mobile fishing is permitted in them. This has been observed at both Lyme Bay 
and the Isle of Skomer where increased static fishing effort has followed the banning of mobile 
fishing gear. Further management of crustacean fisheries may be required to curb this decline in 
stocks.  

Despite no studies being carried out on scallop populations, stakeholder responses indicated that 
scallop stocks are healthy in Jersey’s waters. Some stakeholders stated that some fishers were 
switching gear type to dredging or diving specifically to target them. Respondents generally felt 
scallop populations were likely being bolstered by net larval export from both the Minquiers and 
the  Écréhous.  However,  one  scientist  respondent  stated  that  detecting  spillover  would  be 
challenging due to nearby scallop seeding projects taking place in French waters. Larvae may be 
exported from these projects into Jersey waters, giving the impression that this is due to larval 
export from the MPAs. As was found in the literature review, stakeholders were sceptical of any 
spillover of commercial crustacean stocks from the MPAs, with some stakeholders citing a lack of 
management of crustacean stocks.  

Future studies should look to assess evidence for spillover of scallop populations within the MPAs. 
These have been reported to be more numerous, and larger in size – potentially pointing towards 
greater  larval  production.  The  designation  of  other  MPAs  in  Jersey’s  waters  should  also  be 
preceded by baseline surveys into all commercially important populations, both inside and outside 
the boundaries of the intended MPA. Finally, without strict fisheries control measures in MPAs it 
is  highly  unlikely  that  spillover  will  be  observed.  For  both  the  Minquiers  and  the  Écréhous  to 
benefit neighbouring crustacean populations, further fisheries control measures should be applied 
to the gear types that target them.  

2  BACKGROUND 

Jersey  is  a  self-governing  dependency  of  the  United  Kingdom  located  off  the  north  coast  of 
Brittany, France. With a marine territory  of  around 2,500km2, fisheries are  both culturally  and 
economically important to Jersey’s 103,000 inhabitants. The marine environment surrounding the 
island is predominantly shallow coastal waters consisting of rocky reef, boulders, cobbles, gravel, 
sand, and biogenic habitats such as maerl and seagrass. Jersey’s large tidal range of up to 12m 

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creates  a  large  intertidal area  with  a  wide  range  of  habitats  that  support  diverse  communities 
(Blampied  et  al.,  2022).  The  shallow  waters  around  Jersey  support  a  fishery  dominated  by 
shellfish, particularly lobster (Homarus gammarus) and crab (Cancer pagurus and Maja squinado) 
which form around 70% of landings (by value). Whelks (Buccinum undatum) and Scallops (Pecten 
maximus) also account for 22% of landed value with wetfish and other species making up 8% 
(Marine Resources, 2021).  

As a signatory of numerous conventions, agreements, and treaties for the protection of the marine 
environment  (OSPAR,  The  Bern  Convention,  the  Convention  on  Biological  Diversity,  and  the 
Ramsar  Convention),  Jersey  is  committed  to  protecting  its  marine  habitats  in  its  waters 
(Government of Jersey, 2013). Historically, protection of Jersey’s waters has been complex, with 
a divisional sea boundary known as the A-K line denoting where French and Jersey vessels may 
fish. This, as well as a three nautical mile exclusion zone around the Island for French vessels, 
were part of the wider Bay of Granville Agreement (BoGA) (Chambers et al., 2020).  

In the wake of Brexit, most of Jersey’s waters were fished by vessels from both France and Jersey. 
This was in line with the EU-UK Trade and  Cooperation Agreement (TCA) that ensured vessels 
with a history of fishing in Jersey or France could continue to apply for temporary permits, so long 
as they provided evidence of fishing in the respective waters between February 2017 and January 
2020. However, today Jersey controls the fishing activities of EU vessels in its waters through a 
permit system which may specify the number of allowed fishing days (up to 170 per year), target 
species, and gear types. As of March 2022, 131 French vessels were licenced to fish within Jersey’s 
waters (Chambers et al., 2020). Before the TCA, historical fishing agreements between France 
and  Jersey  such  as  the  BoGA  have  made  fisheries  management  challenging,  particularly  the 
designation of MPAs (Blampied et  al., 2022). However, in 2017 two MPAs were designated off 
Jersey’s coasts, the Minquiers to the south of the Island and the Écréhous to the northeast. 

Both  the  Minquiers  and  the  Écréhous  are  shallow  subtidal  plateaus  that  consist  of  a  matrix  of 
rocky reefs, sandbanks, and intertidal areas. The Minquiers is located 18 km offshore and covers 
an area of around 47.5 km2, while the Écréhous covers a smaller area of 15 km2 roughly 9 km 
offshore (Figure 1). The reefs themselves have small terrestrial areas (0.1 km2 for the Minquiers 
and  0.6km2  for  the  Écréhous)  with  no  permanent  inhabitants  despite  the  small  huts  found  on 
them.  Historically,  both  reefs  have  been  subject  to  sovereignty  claims  from  both  Jersey  and 
France.  This  was  eventually  resolved  by  the  International  Court  of  Justice  that  declared 
sovereignty of both areas to Jersey (Chambers et al., 2020).  

In  2013,  at  a  meeting of  the  Bay  of  Granville  Agreement  (BoGA),  the  States  of  Jersey  Marine 
Resources team (that manages inland fisheries) expressed a desire to designate MPAs at both the 
Minquiers  and  the  Écréhous.  This  was  to  protect  the  sensitive  biogenic  habitats  found  at  both 
locations such as seagress (Zostera spp.) and maerl (Lithothamnion and Phymatolithon spp.) from 
mobile fishing gears such as dredging and bottom trawling (Blampied, 2015); both of which have 
been shown to damage and disturb benthic habitats (National Research Council, 2002). At the 
time, both the Minquiers and the Écréhous fell under the management framework associated with 
the BoGA. The designation of MPAs was not written into the agreement, and so the proposed ban 
on  mobile  fishing  gears  was  assessed  through  the  existing  management  procedures.  Jersey’s 
position  was  that  the  significant  seabed  habitats  at  both  sites  required  protection  in  line  with 
Jersey’s  commitment  to  OSPAR,  the  Ramsar  Conventions,  and  the  Convention  of  Biological 
Diversity. The opposition to the MPAs designation cited immediate negative economic impacts to 
several vessels, and limited evidence both in favour of banning mobile fishing and concerning the 
location and extent of the seabed habitats at both sites. This discussion continued at following 
BoGA meetings until February 2014 when both parties agreed that strong supporting evidence 
was  required  to  demonstrate  both  the  need  for  the  MPAs,  along  with  what  the  potential  MPA 
boundaries would be (Chambers et al., 2020).  

Coincidentally,  both  the  states  of  Jersey  and  a  local  NGO  called  Société  Jersiase  had  begun 
collecting  offshore  environmental  data  since  2012.  These  studies  were  combined  to  produce  a 
coalition of over fifty professional and amateur researchers with their own respective aspects of 
the reefs which they were to study and report to a central team that coordinated the project. The 
entire study took three years to complete and covered several major research disciplines ranging 
from geology and political history to more relevant studies into the marine environment and the 
ecosystem services provided by both areas (Chambers et al., 2020).  

In  January  2016  the  study  into  both  candidate  MPAs  was  completed,  providing  baseline  data 
across  the  wide  range  of  disciplines  that  were  assessed.  The  study  concluded  that  both  the 

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Minquiers  and  the  Écréhous  possessed  both  high  biological  productivity  and  key  habitats, 
principally seagrass and maerl beds which act as nurseries for shellfish and fish species. It was 
also  concluded  that  these  nurseries  likely  play  an  important  role  as  a  source  for  population 
recruitment, thereby  helping  to sustain  stocks that are  exploited in the surrounding waters  off 
Jersey.  It  was  recommended  that  protecting  both areas  to  conserve  the  habitat  in  both  areas 
would provide economic benefit to the whole Bay of Granville (Chambers et al., 2016; 2020).  

Figure  1:  shows  the  location  of  all  MPAs  within  Jersey's  territorial  waters,  with  the 
Écréhous shown in pink and the Minquiers in green (source: Blampied et al., 2022). 

The results of the joint study were presented to BoGA participants with the recommendation that 
mobile  fishing  gear  be  banned  at  both  the  Minquiers  and  the  Écréhous.  This  proposal  was 
discussed and eventually accepted for both areas, after an intensive dive survey of the Écréhous 
was prompted by objections. These were mainly from French scallop dredgers over the loss fishing 
grounds containing maerl beds which they viewed as a viable fishing ground. A compromise was 
eventually found resulting in the removal a planned buffer zone, bringing the park boundary closer 
to the edge of the maerl beds. The law creating both MPAs came into force on October 4th, 2017, 
prohibiting any form of mobile fishing in either MPA at the Minquiers or the Écréhous (Hall-Spencer 
et al., 2008; Chambers et al., 2020).  

It should be noted that separate static gear restrictions banning parlour pots are in place at both 
the Minquiers and the Écréhous. The boundaries of these restrictions do not directly match the 
MPA boundaries, with one No Parlour Pot Zone (NPPZ) covering all of the Minquiers and the other 
covering  over  half  the  Écréhous,  with  areas  to  the  east  of  the  Erehous  having  no  potting 
restrictions (Figure 2). the Minquiers’ NPPZ has been in place since 2007, while the NPPZ at the 
Écréhous  was  established  after  the  designation  of  the  MPA,  in  2018  (Blampied  pers  comms., 
2023).  

This  study  attempts  to  assess  the  potential  for  ecological  and  fishery  spillover  from  both  the 
Minquiers  and  the  Écréhous  MPAs.  Given  both  protected  areas  relatively  recent  designation, 
detecting spillover directly is unlikely. However, this study draws on the most up-to-date research 
into both areas, while also engaging with stakeholders closest to both MPAs to understand their 
opinions on spillover from the MPAs. Demonstrating the occurrence of spillover from  protected 
areas can play a crucial role in ensuring stakeholder acceptance of marine protected areas like 
the Minquiers and the Écréhous.  

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Figure 2: shows the No Parlour Pot Zones (NPPZs) in Jersey's waters (source: Blampied 
pers comms, 2023). 

3  AIMS AND OBJECTIVES 

Spillover is an important factor to assess when measuring the success of an MPA in relation to 
both  ecological  and  socio-economic  goals.  Success  on  both  fronts  helps  secure  positive 
engagement from and between stakeholders, leading to a common goal of sustainable fisheries 
management  under  an  ecosystem-based  approach.  This  case  study  of  the  Minquiers  and  the 
Écréhous aims to inform whether spillover has been detected at both MPAs, whether it is perceived 
to be occurring by local stakeholders, and what methodologies are used for its assessment. These 
aims and their associated objectives are listed below: 

1.  Assess spillover effects at the Minquiers and the Écréhous 

• 
• 

Investigate any potential ecological or fishery spillover in areas surrounding both MPAs; 
Identify any key factors that may influence spillover dynamics such as MPA design, 
fishing practices, and habitat characteristics; 

•  Assess changes in temporal or spatial patterns of commercial stocks after the 

establishment of the MPAs. 

2.  Gain an understanding of stakeholder perceptions of spillover associated with both MPAs 

•  Understand local stakeholder perceptions of the MPAs and their associated restrictions; 
•  Gather information on changes to catches before and after the designation of both MPAs 

in proximity to MPA boundaries. 

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3.  Evaluate any current or previous studies investigating spillover effects at both MPAs 

•  Assess the suitability, practicality, and effectiveness of methodologies used to assess 

• 
• 

spillover; 
Identify any limitations associated with the methodology; 
Provide recommendations for refining or improving the methodology for studies into 
spillover at similar MPAs. 

4  METHODOLOGY 

4.1  Literature Review 

Initially, contact was made with researchers that had a history of studying both the Minquiers and 
the Écréhous, with any available raw data being requested. Due to a lack of available raw data 
on either site, a qualitative approach to spillover assessment was employed. It was hoped that a 
before, after, control, impact analysis (BACI) could be undertaken using outputs from previous 
studies, however, all monitoring of the MPAs came after their designation, meaning no data from 
before 2017 could be used as a benchmark for comparison. As a result, a literature review of all 
relevant scientific and grey literature relating to the ecology of the MPAs and their surrounding 
waters, and the fisheries that operate both inside and outside the MPAs. Literature searches used 
Boolean  logic  to  combine  terms  for  the  Minquiers  and  the  Écréhous  and  different  topics.  For 
example, “Les Minquiers” OR “Les Écréhous” AND “spillover” OR “fish biomass” OR “fishery”. This 
produced searches that provided literature relating to research conducted in both MPAs focusing 
on changes in commercially exploited populations, fish community assemblages or impacts on the 
local fishery. Searches used ResearchGate, Google Scholar, and Science Direct, with all relevant 
literature being stored and managed in a Zotero library. Direct contact was also made with several 
people  that  were  particularly  familiar  with  the  study  sites,  this  produced  some  more  relevant 
publications.  

4.2  Stakeholder survey 

We  developed  a  questionnaire  to  assess  the  perceptions  of  key  stakeholders  on  the  potential 
spillover  effects  in  their  nearby  MPAs.  The  questionnaire  comprised  of  open-ended  and  closed 
questions to elicit stakeholder views and experiences on the different aspects of this study (Annex 
4). The open-ended questions aimed to capture stakeholder opinions on, for example, how aware 
the  stakeholder  was  of  the  regulations  and  management  measures  of  the  MPA.  The  closed 
questions  were  statement-based  and  used  Likert  scale  answer  categories  (such  as:  Strongly 
agree; Agree; Neutral; Disagree; Strongly Disagree) for the stakeholder to choose from.  

The  questions  were  grouped  into  four  broad  categories  to  encapsulate  the  key  issues  being 
studied. These included:  

(i)  Respondent  information.  The  first  section  required  basic  information  from  the  respondent, 
including their name, institution and the type of stakeholder category they belonged to. 

(ii)  Background  information.  The  second  section  of  the  questionnaire  gathered  background 
information from the stakeholder to understand more about the respondent and their use of the 
MPA. Questions included knowledge of when the MPA was established, the type of restrictions in 
place and how long the stakeholder has been associated with the MPA either through research, 
fishing or managing it.  

(iii) Fishery impacts of MPAs. The third section explored the respondent’s perceptions of the socio-
economic  impacts  of  spillover  from  the  MPA.  Stakeholders  were  asked  to  state  whether  the 
designation of an MPA / area where fishing is limited has led to an increase in revenues for fishers, 
whether the fishing community in the area feel their fisheries livelihoods are more secure after 
the  MPA  was  established,  and  the  extent  to  which  they  believe  spillover  from  the  MPA  has 
influenced the catch composition in adjacent fishing grounds. 

(iv)  MPAs  as  management  tools.  The  fourth  section  of  the  questionnaire  focused  on  the 
respondent’s  perceptions  on  whether  MPAs  are  conservation  or  fisheries  management  tools. 
Stakeholders were asked to state whether their local MPA was acting as a conservation tool, a 
fisheries management tool or both. Other questions under this section required stakeholders to 
state  their  agreement  /  disagreement  on  whether  the  establishment  of  MPAs  is  an  effective 
conservation  strategy  to  support  fish  populations  and  commercial  fisheries  in  their  area. 

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Respondents were also asked to indicate what factors they thought were contributing to spillover 
effects. 

Four  key  stakeholder  groups  were  targeted  under  this  consultation  including  commercial  and 
recreational fishers, fisheries managers and government authorities, scientists and environmental 
non-government  organisations  (NGOs).  Therefore,  while  the  four  sections  of  the  questionnaire 
where the same, specific questions were  included  for each of the four respondent groups. The 
questionnaire was set up as an online survey to improve ease of response for stakeholders.  

The link was sent to three local scallop divers, the Jersey Fisher’s association, individuals in the 
States  of  Jersey  Fisheries  and  Marine  Resources  team,  the  Jersey  Inshore  Fishermen’s 
Association,  three  local  marine  conservation  NGOs  operating  in  the  area,  a  marine  resources 
consultancy, and a local dive centre that frequently dives the MPAs. After poor uptake from remote 
stakeholder engagement via the survey link, the decision was made to visit Jersey for two nights, 
conducting  in-person  interviews,  using  the  survey  as  a  template  so  that  responses  were 
comparable.  

5  RESULTS 

5.1  Literature Review  

Given the recent designation of both MPAs in 2017, few studies have investigated their effects on 
local fisheries or the ecosystems within their boundaries. However, there have been two studies 
that  formed  part  of  a  PhD  thesis  published  in  March  2022.  These  assessed  the  responses  of 
epibiotic  and  infaunal  assemblages,  mobile  species  biodiversity,  and  commercial  crustacean 
populations  to  the  removal  of  bottom-towed  fishing  within  the  Minquiers  and  the  Écréhous 
(Blampied, 2022).  

The  study  into  epibiotic  and  infaunal  assemblages  assessed  how  the  proportion  of  structure-
forming organisms had changed inside both the Écréhous and the Minquiers, and at control sites 
outside of the MPAs (Figure 3). While this is not an assessment of spillover, understanding how 
habitat-building organisms’ coverage (such as that of maerl and seagrass) is changing may be a 
good indicator of areas’ ability to act as a nursery to commercially important species (Blampied, 
2022). The three organisms studied were seagrass (Zostera marina), species of maerl, and Lanice 
conchilega. At the Écréhous, maerl alone was the only organism assessed, while at the Minquiers 
seagrass and Lanice conchilega were assessed.   

Figure  3:  shows  the  mean  (and  standard  error  bars)  proportion  of  structure-forming 
organisms for Year, Location, and Treatment (whether sites were in the MPAs or were 
control sites) (source: Blampied, 2022). 

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While mean values for the proportion of structure-building organisms are not quoted in the paper, 
Generalised  Linear  Mixed  Effects  Models  showed  the  proportional  cover  of  structure  building 
organisms  to  be  significantly  greater  in  the  MPAs  compared  to  their  open  controls.  This 
proportional value decreased for the MPAs between 2018 and 2019, before stabilising in 2020. In 
comparison,  a  decline  was  observed  at  the  open  control  sites  throughout  the  study,  with  a 
significant decline being observed in 2020 compared to 2018 and 2019 (Blampied, 2022) (Figure 
3).  

The assessment of mobile species biodiversity (Blampied et al., 2022) acted as a baseline survey 
for total diversity and total abundance of all mobile species that were detectable via baited remote 
underwater  video  (BRUV).  Of  these  species,  spider  crab  Maja  brachydactyla  was  the  only 
commercially  important  species  recorded.  Black  bream  Spondyliosoma  canthurus  was  also 
observed  and  assessed,  however  this  species  is  not  caught  in  large  quantities  by  commercial 
vessels.  

Figure  4:  shows  the  total  number  (and  standard  error  bars)  of  spider  crab  (Maja 
brachydactyla) recorded via BRUVs in sites across three of Jersey's MPAs (including the 
Minquiers and Écréhous) and associated control sites (source: Blampied et al., 2022). 

Spider crab M. brachydactyla were recorded in greater abundance in open control sites (2.5 ± 1.8 
individuals  per  BRUV  deployment)  compared  to  MPAs  (1.9  ±  2.4  individuals  per  deployment) 
(Figure 4). Abundance of M. brachydactyla was greater at the Minquiers compared to the Écréhous 
(Blampied et al., 2022). This may be the result of the Écréhous being more accessible to fishers 
and thereby experiencing greater fishing effort. 

The study investigating the recovery of commercial crustaceans after the removal of towed fishing 
gear measured species abundance inside and outside both the Minquiers and the Écréhous. One 
MPA site was used at the Minquiers, with two open control sites outside the MPA, whereas at the 
Écréhous,  two  MPA  sites  were  used  and  one  open  control  site.  Pots  used  in  this  survey  were 
modified to prevent escape of undersized individuals to allow individuals under minimum landing 
size  (MLS)  to  be  recorded,  giving  a  reading  for  individuals  in  younger  age  classes  (Blampied, 
2022).  

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The results from this study show that responses of crustaceans to management strategies may 
vary greatly across species and size classes. Each species’ response to the removal of bottom-
towed fishing gear is varied, with many seeing a gradual decrease in abundance. At the Minquiers, 
there was no significant difference in abundance of lobsters between the MPA test site and the 
control site outside the MPA. At the Écréhous, abundance was significantly greater inside the MPA 
than at the control site, this was largely due to the high abundance of below MLS lobsters inside 
the MPA. Spider crab showed no increased abundance in either of the MPAs over the study period, 
although the Écréhous did show a significant difference in abundance between the MPA site and 
the control site. This was caused by a steady decline in abundance at the control site while the 
MPA spider crab abundance remained stable. Finally, brown crab abundance was only significantly 
greater in the MPA site at the Minquiers in 2019, with all other years and locations showing no 
significant  difference.  The  generally  decreasing  abundances  seen  across  the  three  commercial 
crustacean species is in keeping with historical potting surveys carried out by the States of Jersey. 
Spider  crab  were  the  only  exception  to  this,  with  their  overall  abundance  in  Jersey’s  waters 
increasing in historical surveys (Figure 5), yet in this study the observed abundances were lower 
than  those  in  the  historical  survey  apart  from  a  spike  in  abundance  in  2019  at  the  Écréhous 
(Blampied, 2022).  

Figure  5:  shows  catch  per  unit  effort  (CPUE)  data  from  historic  potting  surveys 
conducted  by the States of Jersey Marine  Resources team between 2014-2020. Lines 
represent  mean  values  of  lobster,  brown  crab,  and  spider  crab  (source:  Blampied, 
2022). 

5.2  Stakeholder survey 

Across in-person interviews and remote survey responses, eight survey scripts were returned for 
analysis,  summarising  the  responses  of  ten  stakeholders.  These  ten  respondents  included  one 
NGO employee, two local Scientists, two local recreational divers, two scallop divers, one full-time 
commercial fisher, and two part-time commercial fishers.   

Ecological changes after MPA designation  

Scientists  have  observed  improvements  in  maerl  and  seagrass  coverage  since  the  MPAs  were 
designated. This has been anecdotally reported to them by divers and has been reflected in their 
video analyses of the sites. They also highlighted that much of the research undertaken on the 
MPAs involved data from the first three years after designation, and so it is unlikely to yield highly 
significant results, but it will act as a baseline study for the sites. Scientists also responded that 
scallop abundance and size of individuals have both increased in the MPA – this is consistent with 
responses from local divers that frequently dive the Écréhous. A scallop diver that also operates 
in and around the  Écréhous  also responded that spider crab, skate,  and  sole  all  seemed to be 
more abundant since the designation of the MPA.  

Changes to catches after MPA designation 

Scientist respondents stated that scallop dredger landings per unit effort (LPUE) outside of the 
MPAs has increased since their designation. Both scallop divers have seen high catches but are 
hesitant to attribute these to the MPAs, with both divers stating that scallop stocks have been 
healthy for several years as conditions have been ideal (low algae levels, correct temperatures, 

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and high light levels in the water column). One scallop diver referenced French seeding projects 
as a factor that has contributed to high catches. The full-time commercial fisher has not heard of 
any of the fleet seeing increased catches as a result of either MPA. One part-time fisher suggested 
that bass catches have slightly increased and that the Minquiers is a bass nursery, however they 
did not think there was a strong direct link between the MPA and bass catches.  

According to fisher responses, catches by static gear fishers have not increased and seem to be 
gradually declining with the exception of spider crab catches. One respondent stated that this was 
a result of no strong regulations on potting, save for the parlour pot restriction zones.  

Fisheries management issues 

The  reported  changes  to  the  fishing  community  in  Jersey  differs  depending  on  gear  type. 
According to the scallop divers that responded, more people are beginning to dive for scallop and 
more fishers are shifting their mobile gear to fish scallop dredging gear. This is due to the high 
market value of scallops combined with their stock in Jersey’s waters being healthy. According to 
part-  and  full-time  commercial  fishers,  the  fleet  is  decreasing.  One  scientist  cited  numerous 
factors that have negatively impacted fishers including Brexit, the Covid-19 pandemic, rising fuel 
costs,  and  dwindling  stocks.  Responses  highlighted  diverging  views  on  closed  areas  between 
scientists and fishers. Fishers typically held the view that no take zones (NTZs) were not effective 
tools for sustainable fisheries management. One scallop diver responded that sustainable fisheries 
practices have very little impact on the marine environment, referencing his ability to pick and 
choose individuals as he surveys the seafloor. Numerous fishers emphasized that they were not 
opposed  to  measures  that  reduce  fishing  effort  (e.g.  MPAs),  but  stated  that  they  felt  these 
measures often ignore economic needs of the fishing community and that they were not always 
based on scientific findings. Two fishers felt that Jersey’s management strategies lacked baseline 
surveys  with  which  new  data  could  be  compared  with.  One  scallop  diver  responded  that  the 
majority of the waters in the Minquiers MPA were already unfished due to being too shallow and 
that the MPA was in fact not acting to reduce fishing effort there. Part-time fishers felt certain 
measures  could  be  tailored  for  larger  vessels  and  that  fleet-wide  measures  took  their  toll  on 
smaller vessels in particular. These same fishers also felt that more parlour pot restrictions should 
be extended to the Écréhous in the summer. Views on MPA compliance differed between scientists 
and fishers, with scallop divers reporting that  regulations are  often broken while scientists felt 
that the fleet were mostly compliant with regulations.  

Spillover 

Scientist respondents both stated that  fishery  spillover  would be difficult  to detect at both  the 
Minquiers and the Écréhous. This is due to both the composition of Jersey’s fleet and the previous 
vessel monitoring systems (VMS) regulations. Currently, all but two of the Jersey commercial fleet 
are under 12m in length and so do not require VMS (and MPAs do not align with logbook reporting 
zones). The result of this is that live fishing effort data cannot be extracted from most of the fleet. 
In future, the entire fleet will be fitted with VMS which will better facilitate tracking of the fleet 
and  fishing  effort.  Another  issue  with  detecting  spillover  that  was  raised  by  scientists  was  the 
restrictions in place at both MPAs do not prevent fishing of any species. Potting effort inside the 
MPAs, particularly at the Écréhous, may have even increased after the MPAs designation according 
to a local fisher. Another fisher stated that more scallop divers are diving at the Écréhous since it 
was protected in 2017. The size of the MPA was also referenced by a scientist who stated that it 
is  difficult  to  attribute  increased  catches  to  such  small  areas  as  the  MPAs.  Another  important 
consideration raised by a scientist was scallop seeding projects, particularly in the Bay of  Saint 
Breiuc. These seeding projects have the potential to supply scallop larvae as far as Jersey (up to 
70km dispersal), and so act as a source population for scallop stocks around the island, thereby 
masquerading as spillover from local MPAs. Scallop dredge surveys are currently being completed 
by  the  fisheries  and  marine  resources  of  the  States  of  Jersey.  These  should  provide  more 
information on scallop stocks and any potential spillover from MPAs; however, spillover was not 
reported to be a topic of high priority for the States of Jersey.  

Fishers’ responses on whether spillover was occurring were sceptical of baseline data and stated 
that so far, only  anecdotal evidence  from  scallop divers existed. Around half the fishers in the 
survey  responded  that  they  were  unsure  whether  spillover  was  occurring  with  the  other  half 
stating that they did not believe it to be occurring. Two fishers said that they did think the MPAs 
were  helping  biodiversity,  but  that  the  only  fisheries  that  were  seeing  a  positive  benefit  were 
those targeting scallops.  

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6  DISCUSSION 

The few studies that have been completed at both the Minquiers and the Écréhous MPAs 
since  their  designation  in  2017  have  shown  no  signs  of  spillover.  This  is  perhaps 
unsurprising given none of them set out to directly assess it. Unfortunately, the lack of a baseline 
survey into commercially important species before 2017 means the BACI approach to assessing 
spillover cannot be taken. This, paired with the inability to access raw data meant this case study 
relied  on  a  literature  review  of  the  few  published  studies  into  the  MPAs  since  their  recent 
designation in 2017, as well as stakeholder engagement assessing stakeholder perceptions of the 
MPAs.  

The  results  of  the  literature  review  show  no  evidence,  direct  or  indirect,  of  spillover 
occurring  at  either  MPA.  The historical  pattern of  commercially  important  crustacean stocks 
declining around Jersey seems to hold true at both MPAs (Blampied, 2022; Blampied et al., 2022). 
These results appear to show heavily exploited stocks, with little positive effect observed in the 
Minquiers  MPA,  however  conversely,  the  Écréhous  did  show  greater  abundances  of  lobsters, 
especially for individuals below the MLS. This high abundance of below MLS lobsters, paired with 
low abundances of above MLS lobsters inside the MPA at the  Écréhous, point towards the  MPA 
being a nursery for lobsters rather than an area experiencing low fishing effort (Blampied, 2022). 
Spider crab abundance was shown to be greater in control regions than in either MPA, with greater 
abundances being observed at the Écréhous than at the Minquiers (Blampied et al., 2022). The 
generally stable or decreasing abundances of crustaceans inside the MPAs is perhaps unsurprising 
given potting is permitted in both protected areas, with no TACs in place for any of the three main 
target species. This fishing effort likely  masks  any  potentially positive effect of the removal of 
bottom-towed fishing gear within the MPAs. Overall, no direct or indirect evidence of spillover is 
detected across all commercial crustacean species at both sites in this study. 

The  results  from  the  BRUV  study  into  mobile  species  biodiversity  only  assessed  one 
commercially  targeted  species,  the  spider  crab.  Their  greater  abundances  at  the 
Écréhous  open  control  site  than  at  the  MPA  point  towards  a  lack  of  fisheries 
management of crustaceans within the MPA (Blampied et al., 2022). It is possible that the 
Écréhous are preferentially fished by potters as dredging is not permitted. This increase in static 
fishing effort after the banning of mobile fishing gears has been observed at both Lyme Bay (Mangi 
et al., 2011; Rees et al., 2021) and the Isle of Skomer Marine Conservation Zone (Burton et al., 
2016). If this is the case, it seems highly unlikely that spillover from the spider crab population 
in  the  Écréhous  would  be  occurring.  The  greater  abundances  seen  in  the  Minquiers 
compared to open control sites (Blampied, 2022) may be a result of the entire Minquiers 
MPA  falling  within  an  NPPZ.  They  may  also  be  a  symptom  of  a  lower  fishing  effort  at  the 
Minquiers MPA due to its shallow waters making navigation challenging. The Minquiers MPA is also 
further from  Jersey than  the  Écréhous, meaning more fuel  is used to reach it making it a less 
popular fishing ground, particularly for Jersey’s inshore fleet. Further study is required on both 
fishing effort and other ecological factors that affect crustacean abundances inside and  outside 
the MPAs.  

While no evidence of fishery spillover has been found at either MPA, the study assessing 
benthic  assemblage  changes  found  significantly  higher  proportions  of  structure-
building organisms in the MPAs than at control sites. This could be an early sign of habitat 
recovery in the MPAs,  which could in turn  lead to habitats that support greater abundances of 
commercially important species. However, the short time-series of just three years since 
designation  will  need  to  be  further  built  upon  to  examine  longer-term  patterns 
associated with commercial species and the benthic communities in the MPAs. Ten years 
since designation has been found to be an important milestone in the ecological recovery of MPAs. 
This meta-analysis of 52 studies found  the  mean  percentage  of positive impacts for MPAs less 
than ten years old was 36%, compared with 67% after the ten-year mark (Smallhorn-West et al., 
2020). It should also be noted that the observed significant difference in proportion of structure-
forming organisms in Blampied, (2022) may be the result of MPA site selection targeting seabed 
with greater abundances of these organisms.  

Future  study  into  the  Minquiers  and  the  Écréhous  should  include  assessments  of  the 
scallop populations in and around both MPAs. The general view of stakeholders on spillover 
from both MPAs was that if it is occurring it will likely be for scallops. Stakeholders reported recent 
catches to have been high for several years to the point that fishers are switching to dredging or 
hand diving scallops. Currently, all evidence on the scallop populations in the area seems to be 
anecdotal,  with  local  divers  reporting  that  scallops  inside  the  MPAs  are  both  larger  and  more 

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abundant. If this is the case, it’s possible that spillover may be occurring; providing this increase 
in  size  has  also  resulted  in  increased  reproductive  biomass.  Detecting  this  spillover  in  future 
research  will  be  challenging  as  seeding  projects  taking  place  in  French  waters  may  also  be 
facilitating larval export into nearby Jersey waters. One scientist respondent stated that scallop 
surveys are currently taking place outside of protected areas and that there are plans to survey 
inside both MPAs as well. This will provide a better understanding of how the MPAs are affecting 
the scallop population.  

The  overarching  perception of  stakeholders  about  the  MPas  at  the  Minquiers  and  the 
Écréhous  is  that  they  act  more  as  a  tool  for  conservation  than  they  do  as  one  for 
fisheries management. It seems their designation has been born out of concerns around habitat 
degradation and ecosystem health than concerns about declining commercial stocks. Respondents 
were sceptical of spillover of crustacean stocks occurring, given the lack of management measures 
applied  to  static  fisheries  inside  the  MPAs.  However,  there  was  a  consensus  that  scallop 
populations  in  Jersey’s  waters  could  be  benefitting  from  the  lack  of  dredging  inside  the  MPAs. 
Those  respondents  with  a  scientific  background  felt  detecting  fishery  spillover  would  be  very 
difficult  given  Jersey’s  current  regulations  on  VMS  (it  is  not  required  on  vessels  under  12m  in 
length).  The  same  respondents  explained  that  this  changing,  with  VMS  being  installed  on  all 
commercial  vessels.  This,  when  paired  with  catch  reports,  could  allow  the  States  of  Jersey  to 
better detect spatial variations in catches that may be the result of spillover – such as increased 
CPUE in proximity to MPA boundaries. Stakeholders also stated that the protected areas were too 
small to see significant spillover from mobile species, with less mobile  species such as scallops 
and whelks being more likely to show signs of spillover from them.  

Generally, stakeholder responses were well aligned with the results from the literature 
review.  Stakeholders  were  not  optimistic  about  long-term  crustacean  trends,  apart  from  for 
spider  crab,  and  generally  did  not  feel  there  was  any  evidence  of  spillover  of  any  crustacean 
populations. Unfortunately, their positive views on scallop stocks could not be confirmed due to 
lack of literature. Acceptance of the MPAs was relatively neutral across stakeholders. Scientists 
and NGO respondents were more positive about the MPAs typically, with fishers presenting more 
sceptical views. However, none of the fishers that responded were ardently against MPAs and all 
believed they have their place in conservation and fisheries management. One fisher stated that 
much of the Minquiers MPA waters were not fished before designation, as they were too shallow 
for some vessels to navigate in. They also cited Jersey’s goal of protecting 30% of its waters by 
2030 as a reason for this – so protection could be afforded with less resistance from the fishing 
community.   

There are a number of lessons that can be learnt from this case study to help direct future MPA 
designation and assessment of spillover. However, the small body of literature, paired with a lack 
of access to raw data, mean these are not based on a large body of scientific evidence but are 
based on relatively few studies and the perceptions of stakeholders closest to the MPAs. Firstly, 
constant monitoring of all species of commercial interest is crucial to detecting spillover. Where 
no  baseline  surveys  exist  and  data  is  lacking,  it  will  not  be  possible  to  attribute  any 
increase  in  catches  to  spillover.  Secondly,  spillover  requires  strict  fishing  control 
measures.  This  is  clearly  illustrated  by  the  low  abundances  of  crustaceans  in  both  MPAs, 
especially of individuals larger than MLS. No TACs are in place for any crustacean species in jersey, 
and the removal of mobile fishing from both MPAs may have increased the effort of static gear 
fishing that targets crustaceans (Blampied, 2022; Mangi et al., 2011). Finally, this case study 
illustrates the difficulty in detecting spillover. Not only are the characteristics of an MPA 
crucial to spillover occurring (e.g. size, time since designation, and fishing restrictions), 
but  the  monitoring  regime  employed  by  those  who  study  it  must  also  be  exact;  with 
ideally baseline surveys required before designation, the surveying of control sites, and 
fine-scale monitoring of the local fleet and its catches. While monitoring is taking place at 
both MPAs, the lack of a baseline survey including control sites means that the BACI approach is 
not possible.  

7  CONCLUSIONS 

This case study has not been able to detect any direct evidence of ecological or fishery spillover. 
The main limitations of the study are a lack of raw data and a small body of literature on either 
MPA – this is largely due to the recent designation of both MPAs. In place of quantitative analyses 
stakeholder surveys were carried out to gauge perceptions of both MPAs with respect to spillover. 
The results from both the literature review and the stakeholder survey point towards little chance 
of spillover from any crustacean species. A lack of management measures in both MPAs, despite 

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some restrictions on parlour pot usage, mean populations have not increased since  both MPAs’ 
designation. However, there was evidence of an increase in the number of lobsters below MLS at 
the Écréhous, indicating that it could be a nursery for lobsters. Stakeholder perceptions typically 
reflected  the  literature  on  crustaceans  but  were  largely  positive  that  scallop  catches  could  be 
increasing,  partially  due  to  the  establishment  of  the  MPAs.  Stakeholders  also  cited  a  potential 
increase in the number of fishers targeting scallops through dredging and diving. However, no 
reports based on scallop surveys have been released so these claims are merely anecdotal at this 
stage.  This  case  study  highlights  the  need  for  fine-scale  fleet  monitoring,  a  sound  monitoring 
methodology that permits ideally a BACI approach to assessing spillover, and the need for strong 
management measures within MPAs to allow commercial species’ abundances to increase. All of 
these are important prerequisites that are required to help detect spillover.  

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8  REFERENCES 

Blampied,  S.R.  (2022).  A  socio-economic  and  ecological  approach  to  informing  sustainable  marine 
management  in  Jersey,  Channel  Islands.  The  University  of  Plymouth,  School  of  Biological  and  Marine 
Sciences.  

Blampied, S. R., Rees, S. E., Attrill, M. J., Binney, F. C. T. and Sheehan, E. V. (2022). Removal of bottom-
towed  fishing  from  whole-site  Marine  Protected  Areas  promotes  mobile  species  biodiversity.  Estuarine, 
Coastal and Shelf Science, 276 (2022) 108033.  

Burton, M., Lock, K., Newman, P. and Jones, J. (2016). Skomer MCZ Scallop Survey 2016 (Issue 196). 

Chambers, P., Binney, F & Jeffreys, G. (2016). Les Minquiers: A natural history. Charonia Media. 

Chambers, P., de Gruchy, C., Morel, G., Binney, F., Jeffreys, G., Blampied, S. and McIlwee, K. (2020). Chapter 
21  –  Crossing  Jurisdictions:  the  implementation  of  offshore  marine  protected  areas  in  an  international 
fishery. Marine Protected Areas: 411-436. Marine Protected Areas: Science, Policy and Management. 

Government of Jersey (2013). Marine Resources Strategy Consultation.  

Hall-Spencer,  J.,  Kelly,  J.  and Maggs, C.  A.  (2008). Assessment  of Maerl  Beds  in  the OSPAR Area  and  the 

Development of a Monitoring Program. Department of the Environment, Ireland. 

Mangi, S. C., Rodwell, L. D. and Hattam, C. (2011). Assessing the impacts of establishing MPAs on fishermen 
and fish merchants: The case of Lyme Bay, UK. Ambio, 40(5), 457–468. DOI: 10.1007/s13280-011-0154-
4 

Marine Resources (2021). Government of Jersey Marine Resources Annual Report 2021.  

National  Research  Council  (2002).  Effects  of  Trawling  and  Dredging  on  Seafloor  Habitat.  Committee  on 
Ecosystem Effects of Fishing: Phase 1 – Effects of Bottom Trawling on Seafloor Habitats, National Research 
Council. 

Rees, A., Sheehan, E. V. and Attrill, M. J. (2021). Optimal fishing effort benefits fisheries and conservation. 

Scientific Reports, 11(3784), 1–15. DOI: 10.1038/s41598-021-82847-4 

Smallhorn-West P. F., Weeks, R., Gurney, G. and Pressey, R. L. (2020). Ecological and socioeconomic impacts 
of marine protected areas in the South Pacific: assessing the evidence base. Biodiversity Conservation, 
29: 349–380. 

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10. 

CASE STUDY REPORT: 

LAMLASH BAY AND SOUTH ARRAN 

UK – CELTIC SEA 

Analysis of potential spillover effects around the 
Lamlash Bay no-take zone and the South Arran Marine 
Protected Area 

Isle of Arran © Pixabay 

William Peat 

MRAG Europe 

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TABLE OF CONTENTS 

1 
2 
3 
4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ......................................................................................... 163 
BACKGROUND .................................................................................................... 164 
AIMS AND OBJECTIVES ....................................................................................... 165 
METHODOLOGY .................................................................................................. 166 
Literature review ....................................................................................... 166 
4.1 
4.2  Stakeholder survey .................................................................................... 166 
RESULTS ........................................................................................................... 167 
Literature Review ...................................................................................... 167 
5.1 
Assessment of scallop abundance and biomass changes in Lamlash Bay NTZ .... 167 
Assessment of Crustacean CPUE, size, and fecundity in Lamlash Bay NTZ ........ 170 
Assessment of observed changes since South Arran MPA designation .............. 171 
5.2  Stakeholder Survey ................................................................................... 172 
Ecological change after NTZ/MPA Designation ............................................... 172 
Management Issues ................................................................................... 172 
Spillover  .................................................................................................. 172 
DISCUSSION ..................................................................................................... 173 
CONCLUSIONS ................................................................................................... 176 
REFERENCES ..................................................................................................... 177 

LIST OF ABBREVIATIONS 

Term 

BACI 

Description 

Before After Control Impact 

COAST 

Community of Arran Seabed Trust 

CPUE 

Catch per Unit Effort 

HPMA 

Highly Protected Marine Area 

MLS 

MPA 

NGO 

NTZ 

Minimum Landing Size 

Marine Protected Area  

Non-governmental Organisation 

No-Take Zone 

SACFOR 

Super-abundant, Abundant, Common, Frequent, Occasional, Rare (abundance scale) 

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1  EXECUTIVE SUMMARY  

In 2008, after persistent campaigning from locals on the Isle of Arran, the Lamlash Bay no-take 
zone (NTZ) was designated. Covering an area of 2.67 km2 between the Holy Isle and Lamlash on 
the  Isle  of  Arran,  the  NTZ  is  protected  against  all  types  of  fishing  that  is  not  carried  out  for 
scientific  purposes  which  requires  a  permit  from  Marine  Scotland.  The  MPAs  designation  was 
prompted by local concerns that nephrops trawlers and scallop dredgers were degrading habitat 
and  decreasing  the  biodiversity  found  in  the  waters  around  Arran.  Much  of  this  local  pressure 
came  from  the  Community  of  Arran  Seabed  Trust  (COAST)  –  an  NGO  that  advocates  for  and 
monitors the  recovery of the seabed  and biodiversity in  the waters of Lamlash Bay and South 
Arran. Continued monitoring of the NTZ by COAST and the University of York has occurred since 
2010,  21  months  after  the  MPA’s  establishment.  Evidence  of  recovery  in  the NTZ,  paired  with 
further advocacy for seabed protection, led to the designation of the South Arran Marine Protected 
Area (MPA) which protects a wider area of 250 km2 around the NTZ from bottom trawling and 
dredging. This study assesses the potential for fisheries and ecological spillover of commercially 
important target species from  both  the  Lamlash  Bay NTZ and the wider South Arran MPA into 
their surrounding waters. 

Ideally,  a  Before After Control Impact  (BACI) approach to  assessing  spillover  could have  been 
used, however monitoring for the NTZ did not take place prior to designation meaning no “before” 
data exists for comparison with changes after the designation. Similarly for the wider MPA,  all 
baseline sites sampled before designation were contained in the eventual MPA, meaning no control 
sites existed from before the MPA was designated. In the absence of these raw data from both 
protected areas, a literature review was completed covering all relevant studies and grey literature 
pertaining to the MPAs. To supplement this, a stakeholder survey was also attempted, with the 
views  of  those  closest  to  the  MPAs  being  surveyed  relating  to  changes  since  designation, 
management of the MPAs, and spillover.  

Results  from  both  the  literature  review  and  the  stakeholder  surveys  found  potential  indirect 
evidence  of  spillover.  For  king  scallop,  densities,  reproductive  and  exploitable  biomasses  were 
shown to have increased inside the NTZ relative to those outside of the MPA in 2014. Increased 
reproductive biomass of king scallops also points towards increased larval export from the NTZ, 
potentially resulting in spillover. Furthermore, a negative gradient of scallop densities and distance 
from  the  NTZ  boundary  was  found.  This  could  be  evidence  of  spillover,  with  larval  dispersal 
decreasing with distance from the NTZ. However, this may be evidence of a phenomenon termed 
the “Halo effect”, where fishing effort increases with distance from a MPA.  

Results for lobster populations were mixed, with catch per unit effort (CPUE) patterns fluctuating 
between 2012-2018. A slight increase was observed between 2015-2017, before decreasing in 
2018. However, CPUE was higher for the NTZ than surrounding controls. The decrease observed 
in 2018 is thought to be the result of density dependence as very large individuals were found in 
the MPA. These are thought to hold larger territories and potentially deter smaller lobsters and 
brown crabs from occupying nearby seabed. CPUE of above MLS lobsters was found to decrease 
with distance. Again, this may be evidence of spillover but may also be the result of the “halo 
effect”. The greater lobster size found in the NTZ may also be indirect evidence of spillover as 
lobster fecundity is directly related to size. Larger individuals within the NTZ are likely contributing 
to a net export of larvae into the surrounding waters; potentially supporting sink populations in 
fished areas. Tagging studies of lobsters showed movement of  individuals both into and out of 
the NTZ but no significant net movement was observed.  

Future  studies  into  spillover  from  both  the  NTZ  and  the  MPA  should  look  to  assess  catch  data 
where  possible,  providing  more  insight  into  whether  catches  changed  before  and  after  the 
designation of either protected area. More directed research could also employ genetic methods 
to assess whether juveniles in surrounding waters were the sprat of adults inside the MPAs. For 
lobsters, acoustic tagging could reveal more fine-scale movement to determine whether there is 
significant net migration out of the MPA.  

Despite the evidence for spillover identified in this study being indirect, it should be noted that 
monitoring of both the NTZ and the MPA has shown habitat recovery, increased biodiversity in 
benthic assemblages, and significant changes in abundance of some commercially fished species. 
MPAs  can  take  many  years  to  recover  from  intense  bottom  trawling  and  these  results  are 
encouraging  that  both  protected  areas  may  be  able  to  support  commercial  populations  that 
spillover into surrounding fisheries in the future.   

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2  BACKGROUND 

Arran is an island off the west coast of Scotland, situated in the Firth of Clyde. With an area of 
432km2 and a coastline stretching over 100km, Arran’s marine resources are important to both 
its inhabitants and to fishers operating in its waters from mainland Scotland. The wider Firth of 
Clyde  has  long  supported  diverse  and  productive  finfish  fisheries  for  Herring,  Cod,  Haddock, 
Turbot, and Flounder (Thurstan and Roberts, 2010). However, poor management strategies have 
caused  these  stocks  to  dwindle  from  the  1980s  onwards  (Mesquita  et  al.,  2016).  One  of  the 
important  decisions  affecting  these  stocks  was  the  lifting  of  the  ban  on  trawling  within  three 
nautical miles of the shore in 1984 (Stewart et al., 2020; Thurstan and Roberts, 2010). As finfish 
stocks declined, fishers shifted target species towards  shellfish, particularly Dublin Bay prawns 
(Nephrops  norvegicus),  king  scallops  (Pecten  maximus)  to  a  lesser  extent  European  lobster 
(Homarus gammurus) and brown crabs (Cancer pagurus) (Thurston and Roberts, 2010). Today, 
this shellfish fishery accounts for 98% of commercial landings throughout the Clyde, filling the 
economic gap left by dwindling fish stocks (Howarth et al., 2016). Lobster and crab are typically 
caught by potting from smaller vessels, prawns are mostly caught by otter trawls, and scallops 
are  mainly  caught  by  Newhaven  dredges  with  some  being  collected  by  divers  (Stewart  et  al., 
2020). The bottom-towed fishing gear used to catch prawns and scallop have a significant effect 
on benthic ecosystems, with organisms either being caught or damaged by the heavy gear being 
towed  over  them  (Kaiser  et  al.,  2006).  This homogenizes  habitat,  reducing  its  complexity  and 
thereby reducing its ability to act as a nursery for juvenile fish, molluscs, and crustaceans.  

The Community of Arran Seabed Trust (COAST) was established in 1995 by Howard Wood and 
Don MacNeish; two local divers from the Isle of Arran who were concerned about this decline in 
local  habitat  complexity  caused  by  bottom-towed  fish  gear.  COAST  and  its  members  set  up  a 
grassroots campaign that, after 12 years, led to the establishment of the Lamlash Bay No-take 
Zone (NTZ) in September 2008. The 2.67 Km2 site is located in the north of Lamlash Bay between 
the Holy Isle and the northern shore of the bay (Figure 1). This zone prohibits all types of fishing 
except for that which is part of scientific surveys under a Marine Scotland permit. The NTZ has 
been surveyed since 2010, with the amount of research and output being based on the funding 
that has been available to COAST, the University of York, and to a lesser extent the University of 
Glasgow.  

In  September  2010  further  concerns  raised  by  COAST  about  the  degradation  of  the  marine 
ecosystems in the Firth of Clyde led to meetings with  the Scottish Cabinet-Secretary  for Rural 
Affairs  and  the  Environment,  Richard  Lochhead.  This  meeting  led  to  the  Scottish  Government 
commissioning their own research into the state of the area. The findings of this report confirmed 
findings of marine degradation within the Clyde (Thurstan and Roberts, 2010). Following this, a 
summit was held in April 2014 bringing  together Scottish Ministers and  over  100 stakeholders 
from the Clyde to discuss how the marine management of the area could be improved. Later that 
year in August 2014, the South Arran Marine Protected Area (MPA) became one of 30 MPAs that 
were designated in Scottish waters. Covering an area of 250km2 including Lamlash Bay, the MPA 
had no specific management measures in place at the time of its designation. However, in 2016, 
off the back of consultations by the Scottish Government on potential management measures in 
which results from the Lamlash Bay NTZ were presented, scallop dredging was banned throughout 
the MPA. Trawling was allowed to continue in certain outer regions, with potting being permitted 
across much of the MPA, except where particularly seabed habitats were found (Stewart et al., 
2020) (Figure 1).  

The managing and enforcement of the both the NTZ and the MPA at south Arran are technically 
the responsibility of the Scottish Government, however most monitoring is undertaken by COAST, 
University of York and University of Glasgow. The designation process of both protected areas has 
largely  been  bottom-up,  with  very  strong  campaigning  by  the  local  community  on  Arran.  The 
South Arran could be viewed as an example of top-down designation, as the MPA is one of 30 
MPAs  designated  under  obligations  from  the  UK  Marine  and  Coastal  Access  Act  of  2009  (HM 
Government, 2009). However, without local involvement from COAST and the people of Arran, 
this MPA would likely not have been designated.   

Given the Lamlash Bay NTZ was established over 15 years ago, it seems likely that some spillover 
effects might have been observed by studies or by the local fishing community of Arran. Up to 
this  point  in  time,  no  study  has  collated  all  available  data  and  evidence  on  the  occurrence  of 
spillover at the Lamlash  Bay NTZ and  the  South Arran MPA. This study applies the findings of 
historical research with stakeholder surveys to assess whether spillover is occurring, or whether 
it is thought to be occurring in the eyes of those closest to both protected areas.   

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Figure 1: map of the Lamlash Bay no-take zone (shaded red) with the various zones of 
the South Arran MPA in the surrounding waters (Stewart et al., 2020). 

3  AIMS AND OBJECTIVES 

Spillover is an important factor to assess when measuring the success of an MPA in relation to 
both  ecological  and  socio-economic  goals.  Success  on  both  fronts  helps  secure  positive 
engagement from and between stakeholders, leading to a common goal of sustainable fisheries 
management under an ecosystem-based approach. This case study of the Lamlash Bay NTZ and 
the South Arran MPA aims to inform whether spillover has been detected at both MPAs, whether 
it  is  perceived  to  be  occurring  by  local  stakeholders,  and  what  methodologies  are  used  for  its 
assessment. These aims and their associated objectives are listed below: 

1.  Assess spillover effects associated with the Lamlash Bay NTZ or the South Arran MPA 

• 

• 

Investigate  any  potential  ecological  or  fishery  spillover  in  areas  surrounding  both 
protected areas; 
Identify any key factors that may influence spillover dynamics such as MPA design, fishing 
practices, and habitat characteristics; 

•  Assess  changes  in  temporal  or  spatial  patterns  of  commercial  stocks  after  the 

establishment of the respective protected areas. 

2.  Gain  an  understanding  of  stakeholder  perceptions  of  spillover  associated  with  both  the 

Lamlash Bay NTZ and the South Arran MPA 
•  Understand local stakeholder perceptions of the MPAs and their associated restrictions; 
•  Gather information on any changes to catches before and after the designation of both 

areas in proximity to MPA boundaries. 

3.  Evaluate any current or previous studies investigating spillover effects from either the Lamlash 

Bay NTZ or the South Arran MPA  
•  Assess  the  suitability,  practicality,  and  effectiveness  of  methodologies  used  to  assess 

• 
• 

spillover; 
Identify any limitations associated with the methodology; 
Provide  recommendations  for  refining  or  improving  the  methodology  for  studies  into 
spillover at similar MPAs. 

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4  METHODOLOGY 

4.1  Literature review 

Due to a lack of available raw data on either the  Lamlash Bay NTZ or the South Arran MPA, a 
qualitative approach to spillover assessment was employed. It was hoped that a before, after, 
control,  impact  analysis  (BACI)  could  be  undertaken  using  outputs  from  previous  studies, 
however, all monitoring of the MPAs came after their designation, meaning no data from before 
2017 could be used as a benchmark for comparison. As a result, a literature review of all relevant 
scientific and grey literature  relating  to the ecology of the MPAs and  their surrounding  waters, 
and the fisheries that operate both inside and outside the MPAs. Literature searches used Boolean 
logic to combine terms for the Lamlash Bay NTZ and South Arran MPA and different topics. For 
example, “Lamlash Bay No-take zone” OR “South Arran MPA” AND “spillover” OR “fish biomass” 
OR “fishery”. This produced searches that provided literature relating to research conducted in 
both protected areas focusing on changes in commercially exploited populations, fish community 
assemblages or impacts on the local fishery. Searches used ResearchGate, Google Scholar, and 
Science Direct, with all relevant literature being stored and managed in a Zotero library. Direct 
contact was also made with several people that were  particularly familiar with the study sites, 
this produced some more relevant publications.  

4.2  Stakeholder survey 

We  developed  a  questionnaire  to  assess  the  perceptions  of  key  stakeholders  on  the  potential 
spillover  effects  in  their  nearby  MPAs.  The  questionnaire  comprised  of  open-ended  and  closed 
questions to elicit stakeholder views and experiences on the different aspects of this study (Annex 
4). The open-ended questions aimed to capture stakeholder opinions on, for example, how aware 
the  stakeholder  was  of  the  regulations  and  management  measures  of  the  MPA.  The  closed 
questions  were  statement-based  and  used  Likert  scale  answer  categories  (such  as:  Strongly 
agree; Agree; Neutral; Disagree; Strongly Disagree) for the stakeholder to choose from.  

The  questions  were  grouped  into  four  broad  categories  to  encapsulate  the  key  issues  being 
studied. These included:  

(i)  Respondent  information.  The  first  section  required  basic  information  from  the  respondent, 
including their name, institution and the type of stakeholder category they belonged to. 

(ii)  Background  information.  The  second  section  of  the  questionnaire  gathered  background 
information from the stakeholder to understand more about the respondent and their use of the 
MPA. Questions included knowledge of when the MPA was established, the type of restrictions in 
place and how long the stakeholder has been associated with the MPA either through research, 
fishing or managing it.  

(iii) Fishery impacts of MPAs. The third section explored the respondent’s perceptions of the socio-
economic  impacts  of  spillover  from  the  MPA.  Stakeholders  were  asked  to  state  whether  the 
designation of an MPA / area where fishing is limited has led to an increase in revenues for fishers, 
whether the fishing community in the area feel their fisheries livelihoods are more secure after 
the  MPA  was  established,  and  the  extent  to  which  they  believe  spillover  from  the  MPA  has 
influenced the catch composition in adjacent fishing grounds. 

(iv)  MPAs  as  management  tools.  The  fourth  section  of  the  questionnaire  focused  on  the 
respondent’s  perceptions  on  whether  MPAs  are  conservation  or  fisheries  management  tools. 
Stakeholders were asked to state whether their local MPA was acting as a conservation tool, a 
fisheries management tool or both. Other questions under this section required stakeholders to 
state  their  agreement  /  disagreement  on  whether  the  establishment  of  MPAs  is  an  effective 
conservation  strategy  to  support  fish  populations  and  commercial  fisheries  in  their  area. 
Respondents were also asked to indicate what factors they thought were contributing to spillover 
effects. 

Four  key  stakeholder  groups  were  targeted  under  this  consultation  including  commercial  and 
recreational fishers, fisheries managers and government authorities, scientists and environmental 
non-government  organisations  (NGOs).  Therefore,  while  the  four  sections  of  the  questionnaire 
where the same, specific questions were  included  for each of the four respondent groups. The 
questionnaire was set up as an online survey to improve ease of response for stakeholders.  

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The link was sent to three scientists that have researched the MPAs, several individuals from a 
local marine conservation NGO on the isle of Arran, two local fishers, two local scallop divers, and 
one  fisher  association  from  the  wider  Firth  of  Clyde  area.  To  ensure  that  more  stakeholders 
respond, interviews were conducted over the phone with two key stakeholders using the survey 
as a template so that responses were comparable.  

5  RESULTS 

5.1  Literature Review 

Monitoring of the Lamlash bay NTZ first began in July 2010, roughly two years after the MPA was 
designated. These surveys were carried out by a combination of researchers and students from 
the University of York, local volunteers from COAST, and local commercial fishers. Unfortunately, 
as no baseline survey was carried out prior to the NTZ’s designation, it is inherently very difficult 
to  produce  concrete  evidence  of  spillover  as  the  Before,  After,  Control  and  Impact  (BACI) 
approach (the best model analysis for detecting spillover) is not possible. However, the following 
section outlines studies that have taken place in and around the Lamlash Bay NTZ and the wider 
South Arran MPA. These can offer some insight into the state of the marine ecosystems and stocks 
within the MPAs from which spillover may be occurring.  

Assessment of scallop abundance and biomass changes in Lamlash Bay NTZ 

Initial Lamlash Bay surveys in 2010 involved photo-quadrats and transects as well as dissections 
of scallops  (Howarth, 2014). These  showed higher mean  abundance of juvenile scallops within 
the NTZ than outside of it (Figure 2) as well as a positive correlation between these abundances 
and greater macroalgae and hydroid coverage (Figure 3). This was thought to be the result of 
reduced predation pressure in areas with habitat that provide greater cover for juveniles (Howarth 
et al., 2011; Lambert et al., 2011).  

Figure 2: mean (and standard error) estimated abundance of juvenile scallops (using 
SACFOR) within and outside of the Lamlash Bay no-take zone (Howarth et al., 2011). 

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Figure 3: shows the significant trend in juvenile scallop abundance with (a) Macroalgal 
cover and (b) Hydroid abundance (source: Howarth, 2014). 

Despite this relative increase in juvenile scallop abundance, surveys running up to 2014 showed 
no significant difference between adult scallop density inside and outside the NTZ. However, king 
scallop age, size, and exploitable and reproductive biomass were all significantly greater inside 
the NTZ than outside (Figure 4). Furthermore, incorporating government data on size composition 
of king scallops landed in the Firth of Clyde region showed individuals of legal landing size were 
largest in the NTZ, followed by those sampled directly outside the NTZ (Howarth, 2014). 

Figure 4: mean (and standard error) exploitable  (a) and reproductive (b) biomass of 
king scallops at sites inside and outside the NTZ for years 2010-2013 (source: Howarth, 
2014). 

Further study on data up to 2014 (Howarth, 2014) also revealed a significant difference in scallop 
density along a distance gradient from the NTZ boundary (Figure 5), with densities inside the NTZ 
being  up  to  three  times  greater  than  those  seen  at  sites  up  to  2km  from  the  MPA  boundary 
(Howarth, 2014).  

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Figure 5: shows mean (and standard error) density of king scallops for the years 2010-
2013 along a distance gradient from the NTZ boundary, distances of 0 represent sites 
located inside the NTZ boundaries (source: Howarth, 2014). 

More  recent  surveys  carried  out  in  2019  found  that  over  a  decade  on  from  designation,  king 
scallop density had increased dramatically inside the NTZ with a density 3.7 times higher than it 
was  in  2013  (Figure  6)  (James,  2019).  The  results  showed  densities  inside  the  NTZ  to  be 
significantly higher than those seen at sites outside the wider MPA that were open to dredging. 
Scallop  densities  at  the  near-control  site  within  the  South  Arran  MPA  were  also  high  and  not 
significantly different from those seen inside the NTZ. Figure 6 shows the mean density of king 
scallops across the four different site types surveyed in 2019 (James, 2019).  

Figure 6: shows mean (with standard error) scallop densities within the NTZ, at near- 
and far- control sites within the wider South Arran MPA, and at sites that are open to 
dredging (source: James, 2019) 

Published studies for the effects of the NTZ on crustaceans used survey data collected between 
2012 and 2018. These assessed population dynamics of two commercially important species: the 
European Lobster Homarus Gammarus and the Brown Crab Cancer pagurus. Surveys consisted 
of potting and measuring both catches, and measurements of individuals caught, with some being 
tagged.  

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Assessment of Crustacean CPUE, size, and fecundity in Lamlash Bay NTZ 

For most survey years, lobster CPUE was significantly higher inside the NTZ, with the greatest 
differences in catch rates being for lobsters above Minimum Landing Size (MLS) (e.g., roughly 4 
times higher CPUE inside the NTZ than outside in 2018) (Figure 7). Howarth et al., (2016) also 
observed a decrease in lobster CPUE with increased distance from the NTZ boundary up to 20km 
away (Figure 8) (Howarth et al., 2016). Tagging and recapture studies showed that lobsters were 
moving  both  into  and  out  of  the  NTZ.  This  is  not  direct  evidence  of  spillover,  but  evidence  of 
lobsters  leaving  the  NTZ  could  indicate  some  density  dependence  at  play  in  the  NTZ  lobster 
population (Howarth et  al., 2016).  Finally, lobsters within the NTZ had  consistently larger size 
measurements which is directly linked to egg production. This, paired with increased survivorship 
of mature individuals, likely contributed to lobsters inside the NTZ having 5.7 times more eggs 
than those in an unprotected sampling site of equal size in 2018 (Stewart et al., 2020).) (Howarth 
et al., 2016). Tagging and recapture studies showed that lobsters were moving both into and out 
of the NTZ. This is not direct evidence of spillover, but evidence of lobsters leaving the NTZ could 
indicate some density dependence at play in the NTZ lobster population (Howarth et al., 2016). 
Finally, lobsters within the NTZ had consistently larger size measurements which is directly linked 
to  egg  production.  This,  paired  with  increased  survivorship  of  mature  individuals,  likely 
contributed to lobsters inside the NTZ having 5.7 times more eggs than those in an unprotected 
sampling site of equal size in 2018 (Stewart et al., 2020). 

Figure 7: mean CPUE of lobsters, lobsters above MLS, brown crab, and velvet swimming 
crab within the NTZ and at control sites over a 6-year study period (2012-2018). Data 
from 2016 is missing because no surveys took place that year (source: Stewart et al., 
2020). 

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Figure 8: mean CPUE of both lobster and brown crab for individuals above and below 
MLS plotted against distance from the boundary of the NTZ, combined for years 2012-
2015. Distance = 0 represents sampling sites within the NTZ (source: Howarth et al., 
2016). 

Research  into  brown  crab  population  dynamics  yielded  very  differing  results  to  those  seen  for 
lobster. Throughout the crustacean survey period, catches of brown crab were consistently higher 
in surrounding sites than those inside the NTZ and CPUE increased with distance from the NTZ. 
It was hypothesized by Howarth et al., (2016) that brown crab abundance is negatively affected 
by lobsters through inter-specific competition, causing them to be driven from the NTZ which has 
high densities of large lobsters.  

Assessment of observed changes since South Arran MPA designation 

Monitoring  in  the  waters  of  South  Arran  began  before  the  MPA  was  designated  in  2016.  This 
offered an ideal baseline for comparison when assessing the effectiveness of the MPA as both a 
conservation  tool  and  a  fisheries  management  tool.  Unfortunately,  all  baseline  surveys  were 
carried out in what is now the MPA meaning that, as with the NTZ, it is not possible to use the 
BACI approach to assess spillover due to a lack of a control site prior to the designation of the 
MPA. As with the NTZ, spillover assessment must rely on the outputs from previously completed 
studies and not on raw data.  

Around 40 dive surveys were completed throughout 2014 and 2015 in the waters of the South 
Arran MPA prior to its designation. These typically involved videoed transects where recordings 
were kept for future reference against newly completed transects. Currently, the most recently 
published results are from the 2019 surveys (James, 2019). While no crustacean results are in 
the public domain, results on scallop densities show a rapid recovery of the king scallop population 
after  only  three  and  a  half  years  of  protection  from  dredging.  Results  show  densities  of  king 
scallops within the MPA to be over six times those seen in previous surveys carried out in 2015 
as part of the baseline study (James, 2019). Finfish studies have also been completed in the South 
Arran MPA via drop-down camera surveys, however these assessed behaviours in juvenile gadoids 
which do not represent commercially important species in the Firth of Clyde anymore. 

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5.2  Stakeholder Survey 

Despite  efforts  to  organise  a  visit  to  Lamlash  Bay  for  interviews  with  stakeholders,  it  was  not 
possible to carry out any in-person stakeholder engagement. This was primarily due to scientists 
and  NGOs  working  at  the  site  being  too  busy  conducting  their  summer  surveys.  Also,  despite 
numerous emails and phone calls to fisher associations in the Firth of Clyde, no survey responses 
were given by fishers of any kind. This is potentially the result of a combination of stakeholder 
fatigue and current political tension surrounding the now scrapped highly protected marine areas 
(HPMAs) plan by the Scottish Government. Overall, three stakeholders responded to the survey 
in full, with two being part of a local NGO, and one being a scientist that has researched the NTZ 
since 2010.  

Ecological change after NTZ/MPA Designation  

Respondents all concurred that significant ecological change occurred in the years after the NTZ 
was designated. For the NTZ, these changes were difficult to detect in the first few years after 
designation  with  one  respondent  citing  no  prior  monitoring  before  designation  as  a  potential 
explanation.  Increases  in  abundance,  complexity,  and  functional  biodiversity  were  cited  in  the 
early stages of protection with very large examples of monkey-puzzle bryozoans that build habitat 
complexity.  Furthermore,  biological  traits  analyses  of  benthic  organisms  showed  significant 
differences between the NTZ and the South Arran MPA and areas that are open to dredging. One 
NGO  respondent  also  stated  that  there  had  been  anecdotal  evidence  of  increased  numbers  of 
juvenile gadoids in the NTZ.   

Responses stated that scallop densities were initially slow to recover in the NTZ but are now 3.7 
times the levels seen in 2010 surveys. For South Arran MPA sites, scallop densities increased far 
more rapidly, with current densities being seven times those seen in 2016 when the MPA was first 
designated.  According  to  the  scientist  respondent,  scallops  inside  the  protected  areas  had 
significantly larger gonads than those outside. 

Changes  to  crustacean  populations  have  been  more  complex  according  to  the  scientist 
respondent.  Lobster  populations  increased  within  the  NTZ  after  designation  in  initial  years  of 
protection. However, in recent years the high lobster abundance has decreased and given way to 
lower densities with some very large individuals (with carapace measurements of up to 230mm 
–  nearly three times the  MLS).  Brown crab  densities have been consistently low since  surveys 
began in 2010. According to the scientist respondent, this may be the result of high interspecific 
competition with lobsters for habitat and prey in what is a small protected area.  

Management issues 

All  three  responses  agreed  with  the  following  statement:  “in  order  to  develop  commercial 
fisheries,  certain  areas  of the  MPA  should  be  permanently  closed to  fishing”.  Stakeholders  felt 
that if the correct habitats that harbour and protect exploitable stocks are protected, there will be 
benefits to neighbouring fisheries. It was stressed by the scientist respondent that these protected 
areas  are  better placed  where  sensitive habitat  is present such as maerl or seagrass beds.  All 
respondents felt the NTZ and MPA act as both a conservation tool and a fisheries management 
tool, and that the MPA favoured lower impact fishing methods using static gear or picking scallops 
by hand. In terms of collaboration with the fisheries industry, stakeholders felt local collaboration 
with fishers from the Isle of Arran had been very important in the success of the NTZ and MPA. 
However, they responded that the wider fishing industry had strongly opposed both the NTZ and 
the MPA, particularly since the attempted introduction of the HPMAs by the Scottish Government.  

Spillover 

The  importance  of  commercial  fishery  spillover  was  a  topic  of  high  priority  for  the  scientist 
respondent but was of less importance to the NGO respondents, with seabed and habitat recovery 
and ecological spillover being of more interest to them. All responses stated that, in their opinion, 
spillover of either commercially fished species or their larvae was occurring from the protected 
areas. This was largely in reference to king scallop, with one NGO respondent stating that scallop 
diver  catches  were  said  to  be  higher  since  the  designation  of  the  South  Arran  MPA  reduced 
competition with scallop dredgers. When asked about whether spillover from the protected areas 
has influenced catches of adjacent fisheries, all respondents were unable to answer due to a lack 
of data on local catches.  

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Regarding survey data on the NTZ and MPA, the scientist responded that there is a possibility of 
spillover from the scallop population inside protected areas around Arran. This is based on results 
showing larger gonad biomass inside the NTZ than outside and based on the high scallop densities 
seen in both the NTZ and the MPA. The respondent cited density as an important factor in the 
fertilisation rate of broadcast spawners. The higher densities inside both protected areas should 
lead to greater production and export of larvae from inside the protected areas than outside.  

According  to  the  scientist  respondent,  no  concrete  evidence  of  spillover  has  been  found 
throughout the survey years. Tagging surveys did show movement of lobsters into and out of the 
NTZ,  however  there  was  no  significant  net  movement  that  would  indicate  spillover.  There  is 
interest in carrying out  more  detailed  acoustic tagging surveys that use  receivers to give fine-
scale  spatial  data,  but  this  is  subject  to  further  funding.  The  respondent  also  cited  previous 
research  that  assessed  CPUE  of  lobsters  along  a  distance  gradient  from  the  NTZ  boundaries. 
Initially this showed a negative correlation between CPUE and distance from the NTZ boundary 
which may have been the result of spillover, however this pattern has since broken down.  

The scientist respondent noted that little is understood about marine ecosystem succession after 
the establishment of a protected area in temperate waters. They also said that while little changes 
may be observed at the levels of some commercial  stocks, once the habitat recovers the area 
may be able to support greater abundances of commercially important species. When asked if the 
NTZ  and  the  MPA  were  benefitting  from  spillover  all  stakeholders  responded  positively,  in 
particular when referring to scallop fisheries. 

6  DISCUSSION 

Based  on  results  from  both  the  literature  review  and  the  qualitative  stakeholder 
surveys,  there  is  no  direct  evidence of  spillover  occurring  from  either the  NTZ or  the 
MPA. This does not mean no spillover is occurring, in fact stakeholder responses were 
unanimous  in  their  opinions  that  spillover from  both  protected  areas  was  benefitting 
neighbouring fisheries. Despite a lack of concrete evidence, some results found in the 
literature may be indirect evidence of spillover. These results are summarized in Table 1.  

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Table 1: summarizes the results of the literature review and any potential evidence of spillover in each studied species. 

Species 

Reference 
Figure 

Metric  

Time frame 

Δ MPA 

Δ Ref 

Scenario Description 

Spillover? 

P. maximus 

Figure 4 

Exploitable Biomass 

2010-2013  
(two years  
since NTZ designation) 

Increase 

Slight decrease 

N/A 

Reproductive 
Biomass 

2010-2013 

Relative increase 
compare with 
control site 

Relative  
decrease 
compared with  
NTZ site 

Figures 5  
and 6 

Density (per 100m2 

2010-2013  
(two years  
since NTZ designation) 

Relatively  
higher 

Relatively  
lower 

Exploitable  
biomass  
increased in the 
NTZ while  
decreasing at  
control sites  
outside the NTZ 

Reproductive  
biomass was up to 
2.5 times greater  
inside the NTZ than  
outside 

Mean density  
of scallops  
decreased  
with distance  
from NTZ boundary 

No 

Potentially, greater 
reproductive biomass may  
increase likelihood of 
larval export 

Potentially  
from NTZ, but may be  
result of  
“Halo effect”) 

H.  
gammarus 

Figure 7 

CPUE 

2012-2018 

Complex  
pattern,  
potential 
slight increase 

Decrease 

CPUE fell from 2012 – 2015, 
before increasing for 2017 and 
decreasing slightly in  
2018 

No 

Figure 7 

CPUE of lobsters  
over MLS 

2012-2018 

Increase 

Decrease 

Figure 8 

CPUE of  
lobsters at  
sites with distance  
from  
the NTZ 

2012-2018 

High for above  
legal lobsters,  
low for 
sublegal lobster 

Mixed depending 
on  
age class 

CPUE inside 
NTZ increased 
gradually with a 
slight drop 
in 2015. CPUE fell in control  
sites 

CPUE of legal  
lobsters decreased  
with distance from NTZ  
while sub- 
legal  
increased  
with distance 

Potentially – fecundity 
increases  
with size. Large individuals 
inside the MPA may export 
larvae. 

Potentially, but 
may be the result of the  
“Halo effect” 

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Dissections  from  Howarth  (2014)  found  both  the  exploitable  and  reproductive  biomass  of 
king  scallops  inside  the  NTZ  to  be  18%  and  39%  greater  respectively  than  those 
dissected from sites outside the MPA. By 2013,  this disparity  in  biomass had  increased so 
that exploitable biomass inside the  MPA was twice that outside, and reproductive biomass was 
2.5  times  greater  than  outside  (Howarth,  2014).  While  this  result  is  not  direct  evidence  of 
spillover, the greater  reproductive  biomass readings inside the NTZ, paired with the broadcast 
spawning  strategies  seen  in  scallops  do  point  towards  high  potential  for  larval  export  from 
individuals inside the NTZ. This may supply scallop sprat to other areas around the Firth of Clyde 
that may be fished, thereby providing a benefit to surrounding fisheries.  

In  the  same  research,  Howarth  found  that  density  of  king  scallops  declined  significantly 
with  increasing  distance  from  the  NTZ,  with  sites  inside  and  adjacent  to  the  NTZ 
supporting scallop densities of up to three times those seen at sites over 2km from the 
NTZ (Howarth, 2014). This result further supports the notion that high larval export from the NTZ 
is  occurring.  A  higher  density  of  scallops  in  an  area  will  increase  the  output  from  broadcast 
spawning, resulting in a higher number of fertilisations and larvae produced. This result may also 
be evidence of spillover as the decrease in the density of scallops from the NTZ boundary may be 
due to decreased larval supply from NTZ as distance increases.  However, this result should 
be presented with caution as it may be the result of an exploitation pattern referred to 
as the “halo effect” that gives similar results to those created by spillover.  

The halo effect occurs where fishing effort increases with distance from an MPA where that fishing 
method is prohibited (Howarth, 2014). In the case of Lamlash Bay, this might be caused by more 
dredging in sites further away from the boundaries of the NTZ as fishers are deterred from fishing 
close  to  the  MPA  boundary.  This  may  be  because  of  concern  from  fishers  around  incidental 
encroachment into the NTZ while hauling gear or due to some mechanical malfunction, thereby 
incurring a fine or penalty. In these results, scallop densities were similar outside the NTZ to those 
inside up to 1km from the boundary, before dropping to a lower level at 1.5km and remaining 
similar for sites greater than 2km away. This may be an indication of the halo effect occurring up 
to  1.5km  away  from  the  MPA  where  increased  fishing  effort  by  bottom-trawlers  is  observed. 
Further examination of dredging effort is required to overlay spatial patterns in fishing effort with 
scallop densities. 

The evidence for spillover occurring in lobster stocks largely reflects those seen for king scallops. 
Individual lobsters within the NTZ were both larger, and more likely to be carrying eggs 
(berried  female  lobsters)  (Howarth,  2014).  The  size-fecundity  relationship  from  Lizárraga-
Cubedo et al. (2003) suggested that the mean potential reproductive output per female lobster 
in number of eggs was 27.3% higher inside the NTZ than outside (Lizárraga-Cubedo et al., 2003). 
Considering European lobster larvae spend considerable time in the water column, it is likely that 
dispersal of larvae from these large lobsters facilitates net larval export from the NTZ.  

As with king scallops, lobster CPUE was also found to decrease with distance from the NTZ 
boundary,  in  particular  legal  sized  lobsters  (Howarth  et  al.,  2016).  Again,  this  may  be 
another case where results are confounded by the halo effect. On the other hand, creeling vessels 
do not face the same challenges as bottom-trawlers when hauling their gear. Setting and hauling 
creels on the edge of the NTZ should be more feasible than trawling along its boundary, meaning 
this observed decrease in CPUE may be the result of spillover of legal lobsters (Howarth et al., 
2016). T-bar tagging surveys carried  out  on  lobsters in  the same  year did show movement of 
individuals across the boundary, but with no significant net direction (Stewart et al., 2020). One 
stakeholder involved in the monitoring of the NTZ and the MPA stated that they were hopeful of 
conducting an acoustic tagging assessment of crustaceans, but this is subject to the availability 
of funding.  

The  results  from  the  stakeholder  survey  align  very  strongly  with  results  from  the 
literature  review.  This  is  primarily  because  all  respondents  to  the  stakeholder  survey  are 
involved in the monitoring and assessment of the NTZ and MPA. Repeated attempts were made 
to gain responses  from  those  in the  fishing  industry,  but none were submitted. This is likely a 
reflection of the highly charged political debate around the Scottish Government’s HPMAs which 
have now been scrapped.  

With respect to the detection of spillover, the surveys completed at both the Lamlash 
Bay NTZ and the South Arran MPA have a number of limitations. This is not the result of a 
poor  survey  strategy  by  those  involved  in  the  monitoring  of  the  MPAs,  but  more  due  to  the 
different  research  questions  the  monitoring  sought  to  address.  Monitoring  by  COAST  and  the 
visiting researchers assessed how recovery of the habitats and their associated biodiversity in the 

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MPA has progressed since designation. For the NTZ, this did not include a baseline survey prior 
to its designation meaning the use of a BACI approach to assess spillover around the NTZ could 
not be undertaken. For BACI to be possible, a baseline survey of both the NTZ and a number of 
control sites (ideally increasing in distance from the MPA) would have been required before the 
establishment  of  the  NTZ.  Similarly,  the  data  collected  on  the  South  Arran  MPA  also  does  not 
allow the use of the BACI approach to assessing spillover. However, unlike the monitoring of the 
NTZ, this is not because of the lack of a baseline survey. Surveys of the area occurred in both 
2014  and  2015,  but  all  sites  that  were  sampled  in  this  period  would  go  on  to  fall  within  the 
boundaries  of  the  new  South  Arran  MPA  (Stewart  et  al.,  2020).  This  means  that  no  “before” 
control  site  was  sampled prior  to  the  MPAs  designation,  meaning  no  comparison  can be  made 
with a control site that was sampled alongside the baseline survey of sites inside the MPA. Again, 
this is not a criticism of the survey methodology employed by those around Arran, but simply an 
illustration of the different research questions being asked to the ones in this study.  

Another  issue  with  detecting  spillover  is  the  lack  of  CPUE  data  from  commercial 
fisheries  around  the  MPAs  both  before  and  after  their  designation.  Detecting  actual 
commercial  fishery  spillover  from  the  NTZ  and  the  MPA  requires  the  analysis  of  commercial 
landings, no studies have analysed this data specifically for the purposes of detecting spillover 
from South Arran. This would require accurate VMS data which does not exist for many vessels 
below 12m, as well as highly specific catch records that allow the assessment of catches along a 
distance gradient from the NTZ and MPA.  

This case study highlights how difficult it is to obtain results that unequivocally show spillover. 
However, there are several lessons that can be learned should MPA managers in other regions 
wish to assess spillover. Firstly, to assess spillover using the BACI approach it is crucial to 
have baseline data at both the site that is to be  protected, and control sites that will 
not  be  protected.  Unfortunately,  in  the  case  of  Lamlash  Bay  these  data  do  not  exist  and 
therefore do not allow the approach to be used. Secondly, detecting spillover often requires 
methods that produce fine-scale data patterns that cannot be affected by the uneven 
distribution of fishing effort. Examples of these may include the tagging and live tracking of 
stocks, using acoustic tags, or the introduction of a genetic marker that can be tracked through 
generations,  allowing  the  detection  of  larval  dispersal  beyond  MPA  boundaries.  Unfortunately, 
these  methods  are  expensive  in  terms  of  their  financial  cost,  the  resources  and  equipment 
required, and the time they take. Those managing and monitoring MPAs typically have low funding 
and few staff. Potentially the best approach to assessing spillover is to make it the number one 
research priority of a select few MPAs that can afford to carry out the arduous research involved.   

7  CONCLUSIONS 

This case study has assessed all available evidence of spillover of commercially important species 
from both the Lamlash Bay NTZ and the wider South Arran MPA. The lack of a baseline survey 
prior  to  the  NTZ  designation  means  it  is  impossible  to  carry  out  a  BACI  approach  to  assess 
spillover. Instead, a review of the literature and a stakeholder survey were completed to assess 
whether spillover is occurring in the fisheries surrounding both the NTZ and the MPA. The changes 
observed in commercially targeted populations after the designation of the NTZ in Lamlash Bay 
have not followed a clear pattern. Initially, lobster abundances increased drastically before falling 
to give way to a lower abundance of very large and fecund individuals. This is thought to be the 
result  of  intra-  and  inter-specific  density  dependence,  with  very  large  individuals  driving  out 
smaller lobsters and brown crab.  

Stakeholder responses from those involved in the monitoring of the MPAs believe this pattern is 
changing once again. Crustacean tagging studies showed lobsters to be moving both into and out 
of the NTZ, with no significant net direction. It seems likely that larval export is occurring from 
Lamlash Bay’s NTZ from highly fecund individual lobsters. This has the potential to benefit the 
local  lobster  fishery  outside  the  MPA  through  spillover,  however  this  has  not  been  directly 
measured. The same evidence of larval export was found for king scallops, with individuals in the 
NTZ and the MPA having significantly higher reproductive biomass. Abundances for both scallops 
and lobsters were also negatively correlated with distance from the MPA boundaries. This may be 
evidence of spillover of both populations; however, it is impossible to tell whether this is a result 
of the “halo effect” or of spillover without doing a BACI analysis.  

This study highlights the need for sound monitoring practices, ensuring a methodology that will 
allow ideally a BACI approach to be used. It also highlights the complex inter- and intra-specific 
interactions that can arise after protection is afforded to an area of seabed. Various aspects of an 
ecosystem  will  need  to  recover  before  spillover  of  certain  commercially  targeted  species  is 

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observed. It appears scallop populations are able to recover faster around Arran, with crustaceans 
taking  longer.  Future  studies  of  the  NTZ  and  MPA  should  look  to  examine  fine-scale  spatial 
patterns of catches by the local fleet, and should continue to monitor abundance, exploitable and 
reproductive biomass, and if possible, the fine-scale movement of individuals into and out of the 
MPAs.  

8  REFERENCES 

H.M. Government (2009). Marine and Coastal Access Act 2009. HMSO: London. 

Howarth,  L.  M.  (2014).  Measuring  the  Effects  of  Scotland’s  First  Fully  Protected  Marine  Reserve.  Doctoral 

Thesis, University of York. 

Howarth, L. M., Wood, H. L., Turner, A. P., and Beukers-Stewart, B. D. (2011). Complex habitat boosts scallop 
recruitment in a fully protected marine reserve. Marine Biology. 158, 1767–1780. doi: 10.1007/s00227-
011-1690-y 

Howarth, L. M., Pickup, S. E., Evans, L. E., Cross, T. J., Hawkins, J. P., Roberts, C. M., and Stewart, B. D. 
(2015). Sessile and mobile components of a benthic ecosystem display mixed trends within a temperate 
marine reserve, Marine Environmental Research, 107, pp. 8-23. doi: 10.1016/ j.marenvres.2015.03.009. 

Howarth, L. M., Dubois, P., Gratton, P., Judge, M., Christie, B., Waggitt, J. J., Hawkins, J. P., Roberts, C. M., 
and Stewart, B. D. (2016). Trade-offs in marine protection: multispecies interactions within a community-
led temperate marine reserve. ICES Journal of Marine Science, 74: 263–276.  

James L. (2019). The recovery of the commercially valuable scallop species, Pecten maximus, Under Different 

Forms of Protection Around the Isle of Arran. MSc Thesis, University of York, North Yorkshire, 54. 

Kaiser,  M.,  Clarke,  K.,  Hinz,  H.,  Austen,  M.,  Somerfield,  P.,  and  Karakassis,  I.  (2006).  Global  analysis  of 
response  and  recovery  of  benthic  biota  to  fishing.  Mar.  Ecol.  Prog.  Ser.  311,  1–14.  doi: 
10.3354/meps311001 

Lambert, G. I., Jennings, S., Kaiser, M. J., Hinz, H., and Hiddink, J. G. (2011). Quantification and prediction 
of the impact of fishing on epifaunal communities. Marine Ecology. 430, 71–86. doi: 10.3354/meps09112 

Lizarraga-Cubedo, H. A., Tuck, I., Bailey, N., Pierce, G., and Kinnear, J. A.  (2003). Comparisons of size at 
maturity  of  two  Scottish  populations  of  the  European  lobster,  Homarus  gammarus. Fisheries Research, 
65: 137–152. 

Mesquita,  C.,  Dobby,  H.,  and  Mclay,  A.  (2016).  Crab  and  lobster  fisheries  in  Scotland:  Results  of  stock 

assessments 2009–2012. Scottish Marine and Freshwater Science, 7: 73. 

Stewart, B. D., Howarth, L. M., Wood, H., Whiteside, K., Carney, W., Crimmins, E., O’Leary, B.C., Hawkins, 
J.  P.  and  Roberts,  C.  M.  (2020).  Marine  Conservation  Begins  at  Home:  How  a  Local  Community  and 
Protection of a Small Bay Sent Waves of Change Around the UK and Beyond. Frontiers in Marine Science. 
7:76, 14 pp. doi: 10.3389/fmars.2020.00076 

Thurstan, R. H. and Roberts, C. M. (2010). Ecological meltdown in the Firth of Clyde, Scotland: two 
centuries of change in a coastal marine ecosystem. PloS One 5:e11767. doi: 10.1371/journal.pone.0011767 

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11. . CASE STUDY REPORT: 

ATLANTIC ISLANDS NATIONAL PARK OF GALICIA 

SPAIN – THE IBERIAN COAST 

Small-scale fishing vessel operating in the waters of the 
Atlantic Islands National Park. © Bouzas 

Analysis of potential spillover effects around the 
Atlantic Islands National Park of Galicia 

Martin Aranda and Ainhize Uriarte 

AZTI 

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TABLE OF CONTENTS 

1 
2 

3 
4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ......................................................................................... 180 
BACKGROUND .................................................................................................... 181 
2.1  Description of the MPA and fisheries measures .............................................. 181 
2.2  Description of the fishing sector in the MPA .................................................. 183 
AIMS AND OBJECTIVES ....................................................................................... 183 
METHODOLOGY .................................................................................................. 183 
4.1 
Literature review ....................................................................................... 184 
4.2  Stakeholder questionnaire .......................................................................... 184 
RESULTS ........................................................................................................... 184 
5.1  Results of the literature review ................................................................... 184 
5.2  Results of the online survey ........................................................................ 187 
DISCUSSION ..................................................................................................... 187 
CONCLUSIONS ................................................................................................... 188 
REFERENCES ..................................................................................................... 190 

LIST OF ABBREVIATIONS 

Term 

Description 

AINP 

MPA 

MR 

POM 

SCI 

SAC 

SPA 

VMS 

Atlantic Islands National Park 

Marine protected area 

Marine reserve 

Particulate organic matter 

Site of Community Interest 

Special Area of Conservation 

Special Protection Area 

Vessel monitoring system 

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1  EXECUTIVE SUMMARY  

The Atlantic Islands National Park (AINP) of Galicia in Spain, comprises four archipelagos: Cíes, 
Onsa,  Savora  and  Cortegada.  They  are  classified  under  Natura  2000  as  Sites  of  Community 
Interest  (SCI),  Special  Areas  of  Conservation  (SAC)  and  Special  Protection  Areas  (SPA).  This 
group of four archipelagos is classified by the Spanish government as a national park, an official 
designation for terrestrial or marine areas of high natural and cultural value that are recognised 
as  part  of  the  country's  natural  heritage.  Professional  fishing  activities,  including  fishing  and 
shellfish gathering, are not excluded in this  marine protected area (MPA). In fact, a very large 
small-scale  fleet  operates  in  its  waters.  The  only  fishing  activity  prohibited  in  the  MPA  is 
recreational  fishing.  This  report  provides  a  description  of  the  AINP,  the  fleet  operating  in  its 
waters, the conservation and fisheries management measures implemented by the administration 
in  this  area,  the  governance  mechanisms  involving  the  fishing  sector  that  are  in  place,  and  a 
review  of  the  scientific  and  grey  literature  with  the  aim  of  informing  about  potential  spillover 
effects to the surrounding areas of the MPA. 

This work used both a literature review and a questionnaire-based method to gather insights from 
local stakeholders. The literature review identified a small number of references focusing on the 
Cíes archipelago. These references found little research on the potential ecological effects of the 
MPA and no research providing direct evidence of spillover effects beyond the boundaries of the 
MPA. Two studies analysed the effects of recreational fishing restrictions on the trophic structure 
and dynamics inside and outside the MPA. Both studies found no significant differences between 
protected  and  non-protected  areas  on  the  trophic  structure  of  carnivorous  fish  assemblages. 
However, findings of  one the study  revealed a higher biomass of  carnivorous  fishes within the 
MPA compared to the outside areas open to fishing. As the trophic structure is not influenced due 
to  the  restrictions,  it  is  unlikely  to  have  some  spillover  effects.  Indeed,  before  spillover  takes 
place, populations of fish within an MPA must recover to make it possible for them to spill across 
the MPA boundaries. This implies that MPAs should be properly enforced, suggesting that these 
non-significant  effects  on the trophic structure  may be the result  of  the lack  of restrictions on 
commercial  fishing  activity,  which  the  authors  argue  hinders  the  consistency  of  conservation 
outcomes.  

Conservationists emphasise the need for stricter regulation of commercial fishing activities for the 
sake of bird conservation. In the survey questionnaire, one small-scale fisherman felt that closing 
certain  areas  of  the  MPA  to  commercial  fishing  could  be  beneficial  for  the  development  of 
commercial fishing. This fisherman felt that current measures only improve the conservation of 
non-target species and that this MPA is only a biodiversity conservation tool and not a fisheries 
management tool. Regarding the recovery of fish populations in adjacent areas, he felt that there 
may have been a very limited improvement due to the reduction in fishing activity in the MPA. 
However, this is not the result of restrictions on commercial fishing, but rather the result of the 
expansion  of  the  Port  of  Vigo,  pollution  in  the  area  and  climate  change.  A  recent  scientific 
assessment of the fishing pressure in this MPA found that the level of fishing effort was lower than 
expected, leaving open the question of whether it would be necessary to impose restrictions on 
commercial fishing.  

The literature review and stakeholder input through the questionnaire have shown that there is 
very  limited  data  and  high  uncertainty  about  fishing  pressure  and  the  impacts  of  commercial 
fishing  in  the  area.  There  is  therefore  a  need  for  regular  monitoring  of  fishing  activity  and 
assessment  of  its  impact  on  the  status  of  fish  stocks  in  the  area.  Once  the  monitoring  and 
assessments are in place, it would be up to managers and decision-makers to decide whether to 
restrict commercial fishing in the MPA or not. A restriction seems unlikely, because of the high 
economic  dependence  on  small-scale  fishing  in  the  area.  According  to  the  literature  review, 
spillover would occur and could be assessed if commercial fishing were restricted in part or all of 
the MPA. 

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2  BACKGROUND 

2.1  Description of the MPA and fisheries measures 

The ‘Parque Nacional marítimo-terrestre de las Islas Atlánticas de Galicia’, hereinafter the Atlantic 
Islands National Park (AINP), was created the 1st of July 2002 by Law 15/2002 of the kingdom of 
Spain20. The purpose of national parks in Spain is to ensure their conservation and public use, to 
improve scientific knowledge  of  their  natural  and cultural values, to promote a conservationist 
social conscience, to exchange knowledge and experience in terms of sustainable development, 
among others. These are areas of high natural and cultural value, little altered by human activity, 
which,  because  of  their  exceptional  natural  values,  the  uniqueness  of  their  flora,  fauna  or 
geomorphological formations, deserve priority attention for conservation and are declared to be 
of general interest to the nation, being representative of Spain's natural heritage21.  

The AINP extends across the provinces of Pontevedra y A Coruña of the Autonomous Community 
of Galicia. The national park is predominantly maritime and has a total area of 8 333 hectares: 
out of which 1 195 hectares are terrestrial, and 7 285 hectares are maritime. The national park 
comprises four archipelagos: Cíes, Ons, Sálvora, and Cortegada (Figure 1). These archipelagos 
have the following designation types:  

-  Cíes and Ons are special protection areas (SPA) since 1988 and 2001, respectively; 
-  Cíes, Ons, and Sálvora are sites of community interest (SCI) since 2004;  
-  Cíes, Ons, and Sálvora are special areas of conservation (SAC) since 2019.  

In addition, in 2008, the maritime sector of the national park was incorporated into the marine 
protected area (MPA) network of the ‘Convention for the Protection of the Marine Environment of 
the North-East Atlantic’ (OSPAR). The Cíes, Ons, and Sálvora archipelagos were declared sites of 
special protection of natural values22, as per Decree 72/200423. Conservation in the national park 
is regulated by the Governing Plan of the park, as per Decree 177/201824. 

20 Law 15/2002, of July 1, which declares the Atlantic Islands National Park (AINP) of Galicia. 
21 https://www.miteco.gob.es/es/parques-nacionales-oapn/red-parques-nacionales.html. 
22 They are spaces where conservation is necessary due to their natural, cultural, scientific, educational or 

landscape values. 

23 Decree 72/2004, of April 2, by which certain spaces are declared as Areas of Special Protection of Natural 

Values. Council of Environment of the Autonomous Government of Galicia. 

24 Decree 177/2018, of December 27, which approves the Governing Plan for the use and management of 

the AINP. 

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Figure 1:   Geographic location of the Atlantic Islands National Park. From da Costa et 
al. (2022). PNG stands for the Atlantic Islands National Park. 

The designation process of this MPA was conducted on a top-down basis from the general State’s 
administration in coordination with the Government of Galicia. The fishing sector is engaged as 
members  of  the  patronage  of  the  park,  where  two  representatives  of  the  fishing  guilds  are 
present. The function of the patronage, which is established by the law for all national parks in 
Spain, is to supervise  the  fulfilment  of  the  conservation objectives established for the national 
park.  

This patronage is subject to the conservation of nature and the fulfilment of the objectives of Law 
15/2002. This law prohibits recreational underwater fishing and recreational fishing in general in 
the  national  park.  Professional  fishing,  on  the  other  hand,  is  not  prohibited  in  the  park  and  is 
subject  to  the  fishing  regulations  of  the  Fisheries  Council  of  the  Autonomous  Government  of 
Galicia.  The  current  regional  law  on  fishing  is  Law  11/2008  of  the  Autonomous  Community  of 
Galicia25, enacted in 200826. Law 11/2008 in turn derogated from Law 6/1993 of 1993. As can be 
seen, fishing in Galicia was already regulated before the designation of the National Park (in 2002) 
and  is  independent  of  the  MPA.  Law  11/2008  also  regulates  recreational  fishing  activities  and 
explicitly  prohibits  recreational  underwater  fishing  in  MPAs  (Article  23),  and  states  that  the 
regulation of fishing activities of any kind in MPAs shall be established by the Fisheries Council of 
Galicia and shall be subject to the fishing regulations in force. Therefore, measures for professional 
fishing in this MPA are not imposed by the management plan of the AINP which was enacted in 
2018  as  per  decree  177/2018,  but  are  strictly  subject  to  the  Regional  Fisheries  Law.  A  study 
commissioned by the Council of Vigo highlighted that there is not a specific fisheries management 
plan for this MPA with fisheries measures that considers the specific characteristics of this MPA 
(Fernandez et al. 2020). 

25 Law 11/2008 of the 3 of December of Fisheries in Galicia. 
26 Modified by Law 6/2009, of December 11, modifying Law 11/2008, of December 3, on fishing in Galicia. 

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Therefore, professional fishing in this MPA is regulated in the same way as in any other marine 
area in Galicia. Furthermore, the Governing Plan of the Park (Decree  117/201827), in its article 
6.2.3,  considers  that  professional  fishing  and  shellfish  gathering  are  compatible  with  the 
conservation  of  the  Park,  provided  that  they  are  duly  regulated  by  the  fisheries  regulatory 
framework.  The  management  plan  of  the  MPA  has  been  challenged  in  court  by  conservation 
stakeholders, such as the Galician Ornithological Society, who consider that it lacks restrictions 
on  professional  fishing  for  the  sake  of  bird  conservation.  The  Supreme  Court  of  Galicia  has 
dismissed the case, stating that bird conservation measures do not fall within the remit of the 
management plan.  

2.2  Description of the fishing sector in the MPA 

The  abundant  resources  found  in  the  waters  and  seabed  of  the  AINP  have  contributed  to  the 
livelihoods  of  the  island  populations  through  fishing  and  shell  fishing  (Bouzas,  2017).  These 
activities are of small-scale nature and more respectful of the environment, as the catches are 
smaller and more selective. The regulation of fishing in the national park allows for conservation 
and  sustainable  use,  while  providing  economic  and  social  benefits  to  the  entire  surrounding 
community (Bouzas, 2017). 

The region of Galicia, and in particular its coastal communities, is highly dependent on fisheries. 
In fact, the region depends heavily on small-scale fishing activities for income, employment, and 
food  security  (Garcia-Negro,  2018;  Villasante  et  al.,  2021).  Parada  and  Nieto  (2024)  estimate 
that around 2,326 small-scale fishing vessels may operate in the four archipelagos of the national 
park.  Considering  that  3,139  small-scale  vessels  are  registered  in  Galicia,  around  74%  of  the 
regional small-scale fleet operate in the park waters. Cambiè et al. (2012) estimate the number 
of  vessels  fishing  around  the  Cíes  archipelago  at  565  for  at  least  one  month  per  year.  The 
professional fishing activity that takes place around the different archipelagos of the park is of a 
multi-species  and  multi-métiers  nature.  Of  particular  importance  is  the  octopus  fishery,  the 
shellfish fishery, which mainly catches bivalves, the barnacles fishery and the shellfish fishery, 
which involves diving, e.g. for razor clams. There is an important multi-species fleet fishing with 
pots and gillnets.  

The fact that these activities take place in a protected area requires careful management to avoid 
over-exploitation of resources, the impact on the seabed of certain gear used in the park, or the 
by-catch of seabirds or cetaceans in gillnets. According to Bouzas (2017), the administration of 
the park  works  in  collaboration  with  the  Department  of  the  Sea of  the  Government  of  Galicia, 
which has competences on fishing in these interior waters, in order to reconcile fishing activity 
and  biodiversity  conservation.  Shellfish  exploitation  plans  are  drawn  up  by  the  fishing  guilds 
(cofradías) and approved by the Administration. Fishing and shellfish gathering exploitation plans 
are  published  every  year  by  the  government  of  Galicia.  Bouzas  (2017)  adds  that  park  agents 
collaborate  in  surveillance  with  fisheries  inspection  agents  to  ensure  compliance  with  the 
normative. 

3  AIMS AND OBJECTIVES 

Spillover is an important process to assess when measuring the success of an MPA in relation to 
both  ecological  and  socio-economic  goals.  This  case  study  aims  to  inform  whether  the 
implementation  of  the  MPA  yields  spillover  effects  on  the  surrounding  areas  of  the  AINP  and 
whether it is perceived to be occurring by local stakeholders.  

4  METHODOLOGY 

Through  a  literature  review  and  a  questionnaire,  information  was  obtained  for  our  analysis  of 
potential spillover from the MPA.  

27 Decree 177/2018, of December 27, which approves the Governing Plan for the use and management of 

the Atlantic Islands National Park of Galicia. 

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4.1  Literature review 

We identified a list of papers related to the AINP by searching scientific references using the Web 
of  Science  and  Google  Scholar  platforms.  The  Web  of  Science  platform  gives  access  to  the 
databases  of  the  Institute  for  Scientific  Information  (Thomson  Reuters),  covering  all  fields  of 
academic knowledge. The Google platform is a US multinational company specialising in services 
and products related to software, the Internet, electronic devices and other technologies. Google 
Scholar is a search engine  specialised in  searching for scholarly articles, scientific  reports, and 
technical  papers,  as  well  as  theses,  books  and  abstracts  from  a  variety  of  sources  (university 
publishers,  professional  associations,  preprint  repositories,  universities  and  other  academic 
organisations).  

The string of words used in the bibliographic search was a combination of five words (Table 1): 
marine reserve (MR), marine protected area (MPA), spillover, fish, Galicia, and Atlantic Islands 
National Park (AINP). The term "Galicia" is preferable to "Spain" because it is more concise and 
avoids information relating to MPAs in the Mediterranean  Sea and the Canary Islands. In Spain 
there are many protected areas under the term "marine reserve", so a search  was also carried 
out using this terminology.  

4.2  Stakeholder questionnaire 

We  developed  a  detailed  questionnaire  to  assess  the  perceptions  of  key  stakeholders  on  the 
potential  spillover  effects  from  the  MPA  to  the  surrounding  areas  (see  Annex  4).  The 
questionnaires originally drafted in English were translated into Spanish.  

The  questionnaires  were  distributed  by  e-mail  between  July  and  early  September  2023.  Ten 
stakeholders,  comprising  3  administrators,  2  associations  of  fishers,  3  scientists,  and  2 
conservationist groups were invited to fill in the questionnaire. 

5  RESULTS 

5.1  Results of the literature review 

The number of bibliographic references obtained according to Web of Science and Google Scholar 
and using the combination of five terms are presented in Table 1. The literature review revealed 
that very little research has been carried out to assess the potential effects of the establishment 
of the AINP. Only two papers, Blanco et al. (2021) and Cardona et al. (2023), were written about 
research  on  the  effects  of  the  AINP,  of  which  one  referred  to  potential  spillover  effects  in  the 
discussion. A synthesis of the results of these two pioneering studies are provided below. 

Table 1. Number of bibliographic references obtained according to Web of Science and 
Google Scholar. Results obtained by combining 5 terms. (+) indicates “not relevant” for 
the study purpose.  

Abbreviations: AINP: Atlantic Islands National Park; MR: Marine Reserve; MPA: Marine Protected 
Area 

ID  Terms 

Web of Science  Google Scholar 

1  Marine Reserve (MR) 

144 246 

47 200 

2  Marine Protected Area (MPA) 

16 810 

150 000 

3 

4 

Spillover 

Fish 

5  Galicia 

6 

Atlantic Islands National Park (AINP) 

7  MR & spillover 

8  MPA & spillover 

9  MR & fish 

184 

40 894 

1 100 000 

1 137 146 

4 750 000 

40 141 

1 110 000 

650 

409 

360 

214 

4 340 

5 200 

36 926 

40 300 

 
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ID  Terms 

10  MPA & fish 

11  Spillover & fish 

12  MR & spillover & fish 

13  MPA & spillover & fish 

14  Galicia & MR  

15  Galicia & MPA  

16  Galicia & Spillover  

17  Galicia & fish 

18  Galicia & MR & spillover  

19  Galicia & MPA & spillover  

20  Galicia & MR & fish 

21  Galicia & MPA & fish 

22  Galicia & Spillover & fish 

23  Galicia & MR & spillover & fish 

24  Galicia & MPA & spillover & fish 

25  AINP & MR 

26  AINP & MPA 

27  AINP & spillover 

28  AINP & fish 

29  AINP & MR & spillover 

30  AINP & MPA & spillover 

31  AINP & MR & fish 

32  AINP & MPA & fish 

33  AINP & spillover & fish 

34  AINP & MR & spillover & fish 

35  AINP & MPA & spillover & fish 

Web of Science  Google Scholar 

9 601 

903 

360 

336 

718 

78 

41(+) 

2 202 

1(+) 

0 

215 

44 

0 

0 

0 

72 

53 

2(+) 

221 

1 

1 

29 

32 

2 

1 

1 

54 600 

71 900 

5 060 

5 090 

1 350 

1 930 

13 900 

105 000 

148 

169 

1 260 

1 760 

2 370 

145 

164 

9 

13 

3(+) 

123 

1 

1 

9 

13 

2 

1 

1 

Blanco  et  al.  (2021)  estimated  benthic  trophic  levels  to  assess  the  effectiveness  of  MPA 
management in the AINP. The study provides the first multi-species information on stable isotope 
values  throughout  the  boundaries  of  this  MPA  and  surrounding  areas.  The  authors  underscore 
that there are no specific fishing restrictions in this MPA, and only recreational fishing is prohibited 
in the area. The MPA was designated in 2002 to provide ecosystem resilience while allowing for 
artisanal commercial fishing. Blanco et al. (2021) focused only on the three archipelagos facing 
the open sea (from north to south): Sálvora Island, the Ons and Onza Islands and the Cíes Islands. 
Sampling was carried out seasonally between March 2019 and September 2020. Four sites were 
sampled inside the MPA and another four sites were sampled outside the MPA as reference sites. 
Samples included particulate organic matter (POM), plankton, algae, filter feeders, omnivores and 
carnivores. Muscle samples were collected from all macroinvertebrates and fish for stable isotope 
analysis. The effects of protection on stable isotope composition and trophic level of each species 
were analysed using linear mixed effects models with size as a covariate and site (8 sites) as a 
random effect. Significance was assessed by ANOVA.   

No  differences  in  stable  isotope  composition  were  found  between  MPA  and  non-MPA  waters  at 
either the community or species level, even for species targeted by artisanal fisheries both inside 
and outside the MPA, namely Paracentrotus lividus, Mytilus galloprovincialis, Maja sp., Polliceps 
pollicipes, Necora puber and Octopus vulgaris. The results of the study showed that, despite some 
limitations of the study, the protection had no effect on the lower levels of the trophic web in the 

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MPA studied. As an example, the  Figure  2  below  shows results at the  community  level,  stable 
isotope values of δ13C and δ15N were not significantly affected by the protection measures in place 
at this MPA (p = 0.55 and p = 0.35, respectively). The authors conclude that the observed limited 
effects of protection suggest that fishing regulations within the MPA do not affect the trophic level 
at the base of the food web in areas inside the MPA compared to areas outside the MPA. As the 
trophic  level  is  not  yet  influenced  or  changed  due  to  the  MPA  measures,  it  is  unlikely  to  have 
already spillover effects at those archipelagos.  

Figure 2:  Biplot of δ13C and δ15N values in ‰ (mean± SD) of the main trophic guilds 
(primary  producers,  POM,  zooplankton,  herbivores,  filter  feeders,  and  primary  
consumers) inside (blue) and outside (orange) of the MPA. From Blanco et al. (2021). 

In turn, Cardona et al. (2023) assessed the effects of protection from fishing on the food web 
structure  of  shallow  rocky  bottoms  in  two  Spanish  national  parks:  the  National  Park  of  the 
Archipelago of  Cabrera on the Mediterranean  (Balearic Islands)  and the  AINP.  These  MPAs are 
currently the two only maritime national parks in Spain. The authors assessed the abundance and 
biomass of nektobenthic fishes at two sites inside each national park, and two sites outside each 
park for control purposes. For the AINP, they used visual censuses carried out between June and 
July 2017. The fishes were measured, and their size was used to estimate the biomass. Once the 
censuses  were  completed,  the  researchers  sampled  several  species  of  primary  producers, 
macroinvertebrates, and fish at each site for stable isotope analysis. Generalized linear models 
were used to compare the effect of protection on the density and biomass of carnivorous fish, as 
well as on the isotope values and trophic level of the different species groups studied. 

Findings revealed a higher biomass of carnivorous fishes within the AINP compared to the outside 
areas  open  to  fishing  (Figure  3).  Results  also  showed  an  impact  on  the  size  structure  of 
nektobenthic carnivorous fish. However, those changes did not modify the trophic structure.  The 
authors  suggest  that  MPAs  with  stricter  fishing  restrictions  may  allow  for  rebuilding  the 
populations of nektobenthic carnivorous fish and restoring their size structure. Nonetheless, they 
are unlikely to restore the trophic structure to that of pre-fished ecosystems.  

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Figure 3. Descriptors of the fish communities inhabiting the shallow rocky bottom sites 
in the areas open to fishing (OFA, grey) and the MPA (green). The horizontal bar inside 
the box is the mean; the limits of the box are the upper and lower quartiles; and dots 
denote outliers. From Cardona et al. (2023). 

5.2 

 Results of the online survey 

From the ten invited stakeholders that were approached to participate in the online survey, only 
one response was received from a professional shellfish gatherer. We suspect that this is mainly 
due to the summer holidays of scientists, NGOs and administrators, especially in August, and their 
return  to  work  in  early  September.  The  stakeholder  consultation  process  overlapped  with  the 
summer season. The lack of responses occurred despite the fact that two reminders asking for 
cooperation  had  been  circulated  among  these  stakeholders.  August  is  the  high  season  for  the 
HORECA sector in Spain and small-scale fishermen supply fish to this sector during the summer 
holidays. They are therefore unable to devote time to this. In general, it is possible that the lack 
of response from the different stakeholder approaches could also be due to stakeholder fatigue 
with requests to participate in this type of study. 

The fisherman confirmed that there are no restrictions on commercial fishing inside the MPA. He 
commented that there are some differences between the yield of shellfish harvesting inside and 
outside the MPA. For example, catches of shellfish outside the park appear to be higher, but this 
is due to stricter monitoring of shellfish harvesting inside the park. In terms of shellfish species, 
he commented that he did not have data on catches. Regarding spillover effects on the recovery 
of fish populations in adjacent areas due to conservation measures, he replied that these may 
have improved, but to a very limited extent. In fact, he emphasised that commercial fishing was 
continuing at the same level as before the MPA was designated, albeit with a little more control. 
In general, he felt that there were fewer fishers than before the MPA, but this was probably the 
result of factors other than the MPA measures. Likely factors are a lower fish production due to 
the  expansion  of  the  port  of  Vigo,  pollution  and  climate  change.  He  argued  that  the  MPA  is 
primarily  a  biodiversity  conservation  tool  and  not  a  fisheries  management  tool.  He  also 
commented that in order to develop commercial fishing, some MPA areas should be permanently 
closed  to  fishing.  He  argued  that  the  AINP  was  not  an  effective  strategy  for  supporting  fish 
populations and commercial fisheries because there were no restrictions on commercial fishing. 
Finally, he highlighted that this MPA only contributed to the conservation of non-target species. 

6  DISCUSSION  

There are only two papers that have used methodologies to assess potential ecological effects of 
the  AINP.  First,  Blanco  et  al.  (2021)  assessed  the  effects  on  benthic  trophic  levels  due  to  the 
implementation  of  conservation  measures  in  the  MPA.  The  authors  suggest  that  the  lack  of 
differences  in trophic  level  may be due to  similar fishing pressure  inside and outside the MPA, 
resulting  from  the  very  limited  restrictions  on  fishing  in  the  MPA,  only  affecting  recreational 
fishing. Thus, the lack of comprehensive fishing restrictions in the MPA makes it difficult 
to see differences in the low trophic level between unprotected and protected areas. In 
turn,  Cardona  et  al.  (2023)  conducted  a  comparison  between  two  MPAs;  one  with  fishing 
restrictions on commercial and  recreational  fishing  (Cabrera MPA) and one with restrictions on 

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recreational fishing only (AINP). They found that changes in biomass and size structure did not 
modify the trophic structure. The results presented by Blanco et al. (2021) provide evidence (no 
changes in food web structure) that spillover has a limited probability to occur around the 
AINP, as no comprehensive fishing restrictions are in place. Before spillover takes place, 
populations of fish or other organisms within an MPA must recover to make it possible for them 
to spill across the MPA boundaries. This implies that MPAs should be properly enforced (Edgar et 
al. 2014; Guidetti et al. 2008). Spillover in MPA science is a density-dependent mechanism where 
an  increased  competition  within  the  MPA  triggers  a  movement  of  individuals/biomass  towards 
adjacent  areas  outside  MPAs  (Kramer  &  Chapman,  1999;  Roberts  &  Polunin,  1991).  In  turn, 
Cardona et al. (2023) found evidence that fishing restrictions in MPAs may  allow for rebuilding 
the  populations  of  carnivorous  fish  and  restoring  their  size  structure,  but  they  are  unlikely  to 
restore the trophic structure to that of pre-fished ecosystems. It should be added that the lack of 
restrictions on professional fishing might be the result of social pressure, as it has been observed 
in other MPAs (Cadiu et al. 2009; Parada and Nieto, 2024). The AINP is in particularly highly 
dependent on small-scale fishing activities, as two thirds of Galician small-scale fishing takes 
place in these waters. However, it should be noted that, according to one fisher, the number of 
fishers in the area has decreased. This reduction seems to be the effect of external factors such 
as pollution, growth of port infrastructure and climate change, rather than fishing restrictions. 

Villegas-Ríos  et  al.  (2013)  provide  another  reason  for  the  set-up  of  fishing  restrictions.  These 
authors  applied  acoustic  telemetry  to  provide  information  on  fish  movements  of  the 
ballan wrasse (Labrus bergylta) within and around the AINP. This species is heavily targeted 
by the artisanal fleet in Galicia. The movements of a number of individuals were monitored in this 
MPA between September and November 2011. Fish were present in the monitored area for more 
than  92%  of  the  time  monitored,  indicating  a  high  degree  of  site  fidelity.  The  sedentary 
behaviour of this species highlights the potential use of MPAs as a management tool to ensure 
sustainable fisheries for this species. However, it should be added that the MPA approach is not a 
fisheries  management  tool  per  se,  and  ad  hoc  fisheries  management  measures  could  be 
considered  by  decision-makers  to  protect  species  with  high  zonal  fidelity.  One  may  wonder 
whether  fishing  restrictions  for  low-mobility  finfish  species  may  have  spillover  effects.  If 
population biomass of these species within these zones increases, density-dependent factors may 
force small and intermediate-sized fish to migrate and relocate their home range outside the MPA 
(Kramer & Chapman, 1999) thus being accessible to the fishery.  This would require  a rigorous 
scientific assessment. 

However,  there  may  be  opposition  to  the  implementation  of  fishing  restrictions  and  decision-
makers should have their decisions supported by the best available science. One key aspect to 
determine is the level of fishing effort in the area. Parada and Nieto (2024) assessed fishing effort 
in terms of fishing effort density, i.e. number of vessels per km2 and number of sets per km2 in 
the area  and found that fishing effort density  was not  as high as expected and in many cases 
lower than in other MPAs with no-take zones. For example, these authors found that fishing effort 
density in terms of vessels per km2 was lower than in the Cortegada and Tabarca MPAs (Forcada 
et al. 2010), similar to the Medes MPA (Stenzelmuller et al. 2008). The authors report that effort 
densities in terms of sets per km2 are lower than in some areas of the fully protected MPAs of 
Banyuls  and  Medes,  and  lower  than  in  Cabo  de  Palos  (Stenzelmuller  et  al.  2008).  Given  the 
finding  that  fishing  effort  was  not  as  high  as  expected,  the  authors  leave  open  the 
question  of  whether  restrictions  on  commercial  fishing  in  this  MPA  are  necessary.  In 
particular, they consider that the establishment of a no-take zone could increase the intensity of 
fishing near the boundaries of the MPA. The authors also point to the lack of data on fishing effort 
and state that it is essential to carry out regular monitoring of fishing activities, preferably using 
vessel monitoring system (VMS) data. This will be useful in assessing the impact of commercial 
fishing on fish stocks. There appears to be a need for research to determine whether or not fishing 
restrictions should be applied in this MPA. It appears that some species have a site fidelity that 
may require ad hoc management  measures,  but  these  measures should be based  on  scientific 
evidence. 

7  CONCLUSIONS  

The AINP lacks restrictions on commercial fishing. In addition, as noted in the background section, 
conservation  groups  are  calling  for  restrictions  on  commercial  fishing  to  conserve  birds  in  this 
MPA. This case study shows that there is a paucity of studies assessing the  potential effects of 
the  limited  fishing  restrictions  in  place,  and  no  studies  assessing  directly  spillover  effects  and 
different potential scenarios of more extensive fishing restrictions.  

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According to the literature review and questionnaire results, the removal of recreational fishing 
pressure  in  this  MPA  has  not  been  sufficient  to  induce  significant  changes  in  fish  communities 
within the MPA. Therefore, spillover effects outside the MPA appear to be unlikely, as populations 
of fish must recover first within the MPA to make it possible for individuals to spill across the MPA 
boundaries. A limitation of this study is the low number of stakeholders surveyed. In the future, 
engaging  more  stakeholders  could  potentially  offer  a  more  comprehensive  representation  of 
perspectives regarding the roles of the AINP as a fishery management tool and the perception on 
potential spillover effects toward the adjacent areas.  

Further data could be collected, both on biological and socio-economic variables, to improve the 
current  state  of  knowledge  of  fish  resources  and  associated  fisheries.  This  may  also  allow  for 
better assessments in the future, e.g. comparing abundance and richness of fish species using a 
distance  gradient  sampling  scheme  (from  the  MPA  to  the  outside  areas)  integrated  over  time 
using catch data and/or scientific surveys. In addition, tagging studies and / or the application of 
acoustic  telemetry  for  additional  commercial  species,  could  provide  useful  information  on  fish 
movements within and outside the AINP which would allow a more robust assessment of spillover.  

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8  REFERENCES 

Blanco, A., Beger, M., Planes, S., Miller, M., & Olabarria, C. (2021). Estimating benthic trophic levels to assess 
the effectiveness of marine protected area management. Science of the Total Environment, 790, 148234. 

Bouzas, J. A. F. (2017). Gestión ambiental y desarrollo turístico en el parque nacional de las islas atlánticas 

de Galicia. nuevos retos. Sociedad de Ciencias de Galicia. MOL No 17. Diciembre 2017.  

Cadiou, G., Boudouresque, C. F., Bonhomme, P., & Le Diréach, L. (2009). The management of artisanal fishing 
within the Marine Protected Area of the Port-Cros National Park (northwest Mediterranean Sea): a success 
story?. ICES Journal of marine science, 66(1), 41-49. 

Cambiè, G., Ouréns, R., Vidal, D. F., Carabel, S., & Freire, J. (2012). Economic performance of coastal fisheries 

in Galicia (NW Spain): case study of the Cíes Islands. Aquatic Living Resources, 25(2), 195-204. 

Cardona, L., Reñones, O., Gouraguine, A., Saporiti, F., Borrell, A., Aguilar, A., & Moranta, J. (2023). Effects 
of  fishing  on  the  trophic  structure  of  carnivorous  fish  assemblages  from  shallow  rocky  bottoms  of  the 
Mediterranean Sea and the temperate Atlantic Ocean. ICES Journal of Marine Science, 80(4), 751-765. 

da Costa, J. F., Ramil-Rego, P., Guitián, M. A. R., Castro, H. L., Rey, C. O., Gómez-Orellana, L., & Bouzas, J. 
A. F. (2022). Galician Atlantic Islands National Park: Challenges for the Conservation and Management of 
a Maritime-Terrestrial Protected Area. In Protected Area Management-Recent Advances. IntechOpen. 

do Carme García-Negro, M., Rodríguez-Rodríguez, G., & González-Laxe, F. (2018). A importancia económica 

da pesca en Galicia. Revista Galega de Economía, 27(3), 35-48. 

Edgar, G. J., Stuart-Smith, R. D., Willis, T. J., Kininmonth, S., Baker, S. C., Banks, S., et al. (2014). Global 
conservation outcomes depend on marine protected areas with five key features. Nature, 506, 216–220. 

Fernández,  E.;  Barañano,  C.;  Alejo,  I.;  Barreiro,  R.;  Bellas,  J.;  Besada,  V.;  Calviño-Cancela,  M.;  Cordero-
Rivera, A.; González, A.; Méndez, G.; Navarro, L.; Piñeiro-Corbeira, C.; Planas, M.; Prego, R.; Ramil, F; 
Saborido, F.; Sánchez, J.M.; Troncoso, J.S.; A; Velando, A; Villasante, S. (2020). Islas Cíes: un ecosistema 
en la frontera. Ed. Concello de Vigo. Vigo. 240 páginas. 

Forcada, A., Valle, C., Sánchez-Lizaso, J. L., Bayle-Sempere, J. T., & Corsi, F. (2010). Structure and spatio-
temporal dynamics of artisanal fisheries around a Mediterranean marine protected area. ICES Journal of 
Marine Science, 67(2), 191-203. 

Guidetti, P., Milazzo, M., Bussotti, S., Molinari, A., Murenu, M., Pais, A., et al. (2008). Italian marine reserve 

effectiveness: does enforcement matter? Biological Conservation, 141, 699–709.  

Kramer,  D.  L.,  &  Chapman,  M.  R.  (1999).  Implications  of  fish  home  range  size  and  relocation  for  marine 

reserve function. Environmental Biology of Fish, 55, 65–79.  

Parada, J. M., & Nieto, B. (2024).  Quantification of the fishing effort of the artisanal fleet in the Maritime-
Terrestrial  National  Park  of  the  Atlantic  Islands  of  Galicia  in  the  absence  of  vessel  monitoring  system. 
Regional Studies in Marine Science, 103435. 

Roberts, C. M., & Polunin, N. V. C. (1991). Are marine reserves effective in management of reef fisheries? 

Reviews in Fish Biology and Fisheries, 1, 65–91. 

Stelzenmüller, V., Maynou, F., Bernard, G., Cadiou, G., Camilleri, M., Crec’hriou, R., Criquet, G., Dimech, M., 
Esparza, O., Higgins, R., Lenfant, P., Pérez-Ruzafa, Á. (2008). Spatial assessment of fishing effort around 
European  marine  reserves:  implications  for  successful  fisheries  management.  Marine  Pollution  Bulletin, 
56(12), 2018-2026. 

Villasante, S., Tubío, A., Gianelli, I., Pita, P., & García-Allut, A. (2021). Ever changing times: sustainability 

transformations of Galician small-scale fisheries. Frontiers in Marine Science, 1006. 

Villegas-Ríos, D., Alós, J., March, D., Palmer, M., Mucientes, G., & Saborido-Rey, F. (2013). Home range and 
diel  behavior  of  the  ballan  wrasse,  Labrus  bergylta,  determined  by  acoustic  telemetry. Journal  of  Sea 
Research, 80, 61-71. 

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12. 

CASE STUDY REPORT: 

PROFESSOR LUIZ SALDANHA MARINE PARK 

PORTUGAL – THE IBERIAN COAST 

Fishing and recreational vessels at the Sesimbra port. © Sérgio Abreu 

Analysis of potential spillover effects around the 
Professor Luiz Saldanha Marine Park 

Sérgio Abreu 

MRAG Europe 

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TABLE OF CONTENTS 

1 
2 
3 
4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ......................................................................................... 193 
BACKGROUND .................................................................................................... 193 
AIMS AND OBJECTIVES ....................................................................................... 196 
METHODOLOGY .................................................................................................. 196 
4.1 
Literature review ....................................................................................... 196 
4.2  Stakeholder survey .................................................................................... 197 
RESULTS ........................................................................................................... 198 
5.1 
Literature review ....................................................................................... 198 
5.2  Stakeholder perceptions ............................................................................. 202 
DISCUSSION ..................................................................................................... 203 
CONCLUSIONS ................................................................................................... 204 
REFERENCES ..................................................................................................... 205 

LIST OF ABBREVIATIONS 

Term 

Description 

BRUV 

Baited remote underwater videos 

CPA 

INE 

MPA 

NGO 

PNA 

PPA 

TPA 

UVC 

Complementary protection area 

Instituto Nacional de Estatística 

Marine protected area  

Non-governmental organization 

Parque Natural de Arrábida 

Partially protected area 

Total protection area 

Underwater visual census  

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1  EXECUTIVE SUMMARY  

The Professor Luiz Saldanha Marine Park, a marine protected area (MPA) located on the south-
west  coast  of  Portugal,  represents  a  critical  effort  in  marine  conservation,  aiming  to  balance 
ecological preservation with the socio-economic realities of the surrounding communities. MPAs 
are established with the dual goals of protecting biodiversity and enhancing the sustainability of 
local  fisheries  through  the  spillover  effect,  where  protected  areas  potentially  contribute  to 
replenishing fish stocks outside their boundaries. However, the effectiveness of MPAs in achieving 
these objectives has been a subject of debate, reflecting the need for comprehensive studies that 
consider both ecological and socio-economic perspectives.  

The  main  aim  of  this  case  study  is  to  explore  the  perspectives  of  local  stakeholders  and  the 
available literature on spillover effects in the Professor Luiz Saldanha Marine Park. An extensive 
literature  review  and  a  questionnаire-bаsed  method  were  used  to  target  а  wide  range  of 
stakeholders, including commercial and recreational fishers, fisheries managers and government 
authorities, scientists, and environmental non-government organisations.  

The  existing  literature  on  the  MPA  and  the  stakeholder  responses  from  researchers  and 
governmental  authorities  demonstrated  that  this  MPA  can  promote  marine  biodiversity  and 
generate positive spillover effects. Findings from the literature review further substantiate claims 
of effective ecological recovery promoted by the establishment of the MPA. For example, several 
significant ecological changes in terms of fish diversity, species numbers and biomass have been 
observed  by  authors  since  the  MPA  implementation,  both  within  its  boundaries  and  in  its 
surrounding  areas.  In  addition,  research  observe  that  fish  species  may  venture  beyond  MPA 
borders, potentially benefiting external fishing grounds. In contrast, other studies highlighted the 
potential  socio-economic  implications  due  to  of  a  reduction  in  fish  abundance  post-MPA 
establishment. 

Our study encountered limited stakeholder раrtiсiраtion, with a total of five respondents – two 
researchers, two fishers and one government authority. Academic and governmental stakeholders 
corroborate positive ecological shifts and population improvements in fish owing to the spillover 
effect of the MPA regulations, citing improved biodiversity and fish abundance. This is in line with 
prevailing academic literature on the topic. On the other hand, the fishing sector expressed doubts 
and concerns regarding the MPA's advantages both eсonomiсаlly and in terms of overall benefits.  

The study shed light on the сontrаst between the enсourаging eсologiсаl results gathered though 
several  scientific  studies  аnd  the  doubts  рrevаiling  within  the  fishing  seсtor.  Flexible  аnd 
сollаborаtive mаnаgement аррroасhes аre needed to tасkle eсologiсаl аnd soсio-eсonomiс issues 
in  a  holistic  way.  The  literature-based  evidence,  in  tandem  with  the  inputs  from  various 
stakeholders, provide a comprehensive perspective on the potential advantages and challenges 
of  the  MPA.  The  reрort  underscores  the  necessity  of  bаlаnсing  soсio-eсonomiс  аnd  eсologiсаl 
рreservаtion goаls in MPAs by  рromoting the  inсlusion  of  аll stаkeholders, inсluding fishers, in 
MPA  deсision-mаking  рroсesses.  The  study  confirms  the  potential  for  positive  spillover  effects 
from  the  Professor  Luiz  Saldanha  Marine  Park  on  marine  biodiversity  and  fish  resources, 
emphasizing the importance of further research to optimize these benefits alongside addressing 
socio-economic challenges. 

2  BACKGROUND 

Located on the south-west coast of Portugal, the Professor Luiz Saldanha Marine Park is a marine 
protected area (MPA) contained within the Arrábida National Park (‘Parque Natural de Arrábida’; 
PNA). The marine park is situated at the northern edge of the northeast-Atlantic upwelling zone 
and covers an area of 53 km2, extending 38 km along the coast between Cabo Espichel and the 
Sado  estuary.  This  transitional  oceanographic  and  biogeographic  area  makes  it  a  biodiversity 
hotspot, being the northern habitat for subtropical species and the southern habitat for certain 
temperate species (Wooster et al., 1976; Henriques et al., 2009). Historically, the rich biodiversity 
in  the  area  has  been  an  important  resource  for  small-scale  artisanal  fisheries  operating  from 
Sesimbra and Setúbal. 

The MPA is characterized by a varied subtidal rocky seabed with formations of rock blocks and 
boulder fields, reaching depths of 20-25 meters. Adjacent to the rocky base at the eastern section 
of the marine park (east of Sesimbra), sandy bottoms can be found up to 30 meters deep whereas 
in deeper sections of the park, muddy sediments  remain a dominant feature (Henriques et al., 
2014; Henriques et al., 2015). In 2006, the MPA was included in the Natura 2000 network and 

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includes three habitats listed in the Habitats Directive: (i) 1110: Sandbanks partially covered with 
seawater; (ii) 1170: Reefs; and (iii) 8330: Submerged or partially submerged sea caves.  

Created in 1998 under the Regulatory Decree No23/98 and following approval of a zoning plan in 
2005, the marine park became fully operational in 2009 with the implementation of a designated 
no-take  zone.  It  is  designed  to  ensure  marine  conservation  while  facilitating  certain  fishing 
activities. The management plan defines three levels of protection within the MPA (Figure 1):  

(i) 

(ii) 

(iii) 

Total  Protection  Area  (TPA).  This  area  spans  4.3  km²,  acting  as  a  no-take  and  no-
access zone, prohibiting all human activities.  

Partially  Protected  Areas  (PPA).  Four  areas  covering  21  km²  and  permitting 
commercial fishing with specific gear types, such as octopus traps, jigging, and handlining.  

Complementary  Protection  Areas  (CPA).  Three  areas  account  for  28  km²,  are  less 
restrictive, allowing recreational and traditional small-scale fishing methods under specific 
constraints, including licensing vessels under 7 m in length.  

Figure  1.  Map  of  the  Professor  Luiz  Saldanha  Marine  Park  with  the  three  protection 
levels:  Total  Protection  (orange),  Partial  Protection  (blue)  and  Complementary 
Protection (green) (Source: Instituto da Conservação da Natureza). 

Fishing activities like trawling,  dredging, purse-seining,  spearfishing, and discarding  of fish  are 
banned  throughout  the  MPA.  Commercial  fishing,  restricted  to  vessels  from  Sesimbra  port, 
requires a permit and its renewal is dependent on the vessel's continued activity in the area. In 
PPAs, fishing is constrained to zones beyond 200 meters from the coast and solely permits traps 
and jigs. 

Annual landings from small-scale vessels operating in the region between 1995 and 2022 have 
shown  significant  fluctuations.  For  example,  annual  landings  in  Sesimbra  were  lowest  in  2001  
(11 226 tonnes) and peaked in 2019 (36 003 tonnes), whereas in Setúbal landings have been 

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consistently declining since 1995, reaching a significant low in 2013. Overall, Sesimbra generally 
had  higher  landing  values  than  Setúbal,  especially  post-2005.  More  recently,  while  both  ports 
showed slight variances from 2020 to 2022, Setúbal's total landings decreased in 2022.  

Importantly, catch data reported by the Instituto Nacional de Estatística (INE) do not distinguish 
between  different  types  of  fishing  gear.  Instead,  the  aggregated  data  include  both  multi-gear 
fishing (which is allowed in the MPA) and seine and trawl fishing (which are not permitted within 
the MPA). However, a considerable volume of the multi-gear and seine fishing catches is likely 
sourced  from  the  MPA  or  its  nearby  areas,  suggesting  these  numbers  provide  a  good 
representation of the trends in the MPA's landings. Given that Sesimbra also serves as a trawl 
fleet  port,  which  does  not  operate  within  or  in  proximity  to  the  MPA,  the  data  require  careful 
interpretation. However, the increasing trend in Sesimbra's landings, pointed out by Batista et al. 
(2011), seems to continue in later years as shown in Figure 2. 

Figure 2. Annual nominal catch (tonnes) landed in Sesimbra and Setúbal ports between 
1995 and 2022 (source: Instituto Nacional de Estatística). 

Cunha et al. (2014) highlighted the performance of the MPA protection measures in each area, 
noting  that  the  TPA  showed  higher  species  richness,  indicating  a  diverse  range  of  species 
compared  to  the  other  areas.  The  PPA,  meanwhile,  showed  a  high  species  diversity  index, 
indicating a balanced species presence without any dominating. Finally, the CPA scored lower in 
terms of both species diversity and richness. Further research by Abecassis (2015)  highlighted 
potential weaknesses in the operation of the MPA no-take zone. For example, highly mobile fish 
may not be fully protected within the MPA, thus putting them at risk. In this case, the small size 
of the no-take zone within the marine park might not be sufficient to encompass all essential fish 
habitats, which could present challenges to the park's natural diversity and well-being. A separate 
study by Pereira (2018) on the Portuguese MPA, Parque Natural do Sudoeste Alentejano e Costa 
Vicentina, illustrated the benefits of implementing buffer zones around no-fishing areas, providing 
a boost in both the spillover effect and fisheries productivity in less than five years. 

The  MPA  in  Arrábida  witnessed  significant  conflicts  with  stakeholders  upon  the  introduction  of 
fishing restrictions. To address this, a systematic three-phase approach was carried out. The initial 
phase  (2008-2011)  saw  the  implementation  of  the  MARGov  project,  aiming  to  engage 
stakeholders and foster knowledge co-production. The subsequent phase (2012-2014) introduced 
the PostMARGov Group, which focused on deliberations regarding the MPA's regulation. By 2014, 
the  PNA  Strategic  Council  incorporated  the  PostMARGov  Group  as  the  Group  of  the  Sea,  a 
committee dedicated to marine matters. 

Over a decade after implementing the MPA's plan and regulations, positive ecological signs are 
visible,  but  opinions  on  socio-economic  effects  are  mixed.  An  external  assessment  of  the  PNA 
regulation  was  concluded  in  2016  and  discussed  within  the  Strategic  Council  of  PNA  in  2017, 

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providing an opportunity for further dialogue and potential adjustments to the management of 
the protected area (Stratoudakis et al., 2019). 

Stakeholder involvement in the MPA changed significantly from the 2008 MARGov project to the 
2017 Group of the Sea phase. This transformation shifted from the politically driven MARGov to 
a more institutionally anchored Group of the Sea, as described by Vasconcelos et al. (2012) and 
Carneiro (2011). Key findings from the Stratoudakis study revealed an increased establishment 
and  consolidation  of  mutual  understanding,  trust,  and  responsibility  among  the  stakeholders 
(Stratoudakis et al., 2019). As time progressed, understanding process rules and strengthening 
of networks led to new forms of collaboration. Eight measures were proposed regarding changes 
to the fishing rights in the MPA (Stratoudakis et al., 2019). Out of them, three found common 
agreement among stakeholders. These consisted of allowing a passage corridor through the MPA 
during inclement weather, formalizing an exemption for traditional beach seines of Sesimbra for 
touristic purposes, and permitting the use of nets and longlines to fish in areas of partial protection 
(Cunha et al., 2014). However, other proposals such as granting MPA licenses to purse seiners 
from Sesimbra, provision of MPA licenses to all Sesimbra vessels less than 10 meters, distinction 
of management approach between smaller and larger vessels, and the development of stricter 
buffer areas didn't reach an agreement due to clear antagonism in perspective (Horta E Costa et 
al., 2016). These рroрosаls showed сhаnging views аmong stаkeholԁers during the engаgement 
рroсess, highlighting both the diffiсulties аnd oррortunities when everyone works together in аn 
MPA (Stratoudakis et al., 2019). 

3  AIMS AND OBJECTIVES 

The general aim of this study is to better understand the potential spillover effects of the Professor 
Luiz Saldanha Marine Park on local fisheries and conservation efforts. This involves analyzing the 
extent to which the MPA contributes to ecological well-being and socio-economic benefits for the 
surrounding communities. 

To respond to this general aim, we had the following specific objectives: 

•  Undertake a literature review on the spillover effects of the Professor Luiz Saldanha Marine 
Park.  This helps  to contextualize  the study  within the  broader field of  marine conservation 
and fisheries management, identifying gaps in current knowledge and setting a foundation for 
primary research. 

•  Utilize tailored questionnaires to collect data on stakeholder perceptions specifically related 
to the spillover effects of the Marine Park, aiming to understand its influence on conservation 
efforts and local fisheries. This method seeks to uncover the perceived benefits, challenges, 
and  knowledge  gaps  associated  with  these  spillover  effects,  to  inform  strategies  for 
maximizing positive ecological and socio-economic impacts.  

4  METHODOLOGY 

4.1  Literature review 

The literature review in this study was conducted using a thorough approach to provide an in-
depth look at the spillover effects associated with the Professor Luiz Saldanha Marine Park. The 
research  methodology  included  searching  databases  like  ScienceDirect,  SpringerLink  and  also 
Google Scholar using specific keywords. Additionally, academic journals grey literature, websites 
and  recommendations  from  renowned  researchers  were  considered  to  identify  relevant 
publications related to the Professor Luiz Saldanha Marine Park. To ensure that both historical and 
current viewpoints were covered, no time constraints were applied. After an initial scan of titles 
and abstracts, the literature was narrowed down to studies that focused directly on the Professor 
Luiz Saldanha Marine Park and that delved into key themes such as spillover effects and fisheries, 
stakeholders. Consistency in the overall narrative was maintained through ongoing evaluations 
and  the  cross-referencing  of  sources.  Each  article  was  then  critically  analysed  to  identify  its 
strengths and weaknesses and the findings from the different studies were contrasted with one 
another. 

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4.2  Stakeholder survey 

We  developed  a  questionnaire  to  assess  the  perceptions  of  key  stakeholders  on  the  potential 
spillover  effects  in  their  nearby  MPA.  The  questionnaire  comprised  of  open-ended  and  closed 
questions to elicit stakeholder views and experiences on the different aspects of this study (see 
questionnaire in Annex 4). The open-ended questions aimed to capture stakeholder opinions on, 
for example, how aware the stakeholder was of the regulations and management measures of 
the  MPA.  The  closed  questions  were  statement-based  and used  Likert  scale  answer  categories 
(such  as:  Strongly  agree;  Agree;  Neutral;  Disagree;  Strongly  Disagree)  for  the  stakeholder  to 
choose from.  

The  questions  were  grouped  into  four  broad  categories  to  encapsulate  the  key  issues  being 
studied. These included:  

(i)  Respondent  information.  The  first  section  required  basic  information  from  the  respondent, 
including their name, institution and the type of stakeholder category they belonged to. 

(ii)  Background  information.  The  second  section  of  the  questionnaire  gathered  background 
information from the stakeholder to understand more about the respondent and their use of the 
MPA. Questions included knowledge of when the MPA was established, the type of restrictions in 
place and how long the stakeholder has been associated with the MPA either through research, 
fishing or managing it.  

(iii) Fishery impacts of MPAs. The third section explored the respondent’s perceptions of the socio-
economic  impacts  of  spillover  from  the  MPA.  Stakeholders  were  asked  to  state  whether  the 
designation of an MPA / area where fishing is limited has led to an increase in revenues for fishers, 
whether the fishing community in the area feel their fisheries livelihoods are more secure after 
the  MPA  was  established,  and  the  extent  to  which  they  believe  spillover  from  the  MPA  has 
influenced the catch composition in adjacent fishing grounds. 

(iv)  MPAs  as  management  tools.  The  fourth  section  of  the  questionnaire  focused  on  the 
respondent’s  perceptions  on  whether  MPAs  are  conservation  or  fisheries  management  tools. 
Stakeholders were asked to state whether their local MPA was acting as a conservation tool, a 
fisheries management tool or both. Other questions under this section required stakeholders to 
state  their  agreement/disagreement  on  whether  the  establishment  of  MPAs  is  an  effective 
conservation  strategy  to  support  fish  populations  and  commercial  fisheries  in  their  area. 
Respondents were also asked to indicate what factors they thought were contributing to spillover 
effects. 

fishers, 

Four  key  stakeholder  groups  were  targeted  under  this  consultation  including  commercial  and 
recreational 
fisheries  managers  and  government  authorities,  scientists,  and 
environmental non-government organisations (NGOs). Therefore, while the four sections of the 
questionnaire where the same, specific questions were included for each of the four respondent 
groups. The questionnaire (in Portuguese) was set up as an online survey.  

To gather stakeholder perceptions regarding potential spillover effects in nearby MPAs, various 
stakeholders affiliated with the MPA were approached during July and August of 2023. A total of 
17  stakeholders  were  contacted  via  email,  with  10  subsequently  receiving  follow-up  emails  to 
stimulate participation. Additionally, 8 phone calls were made across the stakeholder spectrum to 
enhance  engagement.  When  disaggregated  by  category,  three  representatives  from  fisher 
associations were approached, three from governmental bodies, eight individuals who identified 
as  researchers  from  different  institutes,  and  three  from  NGOs.  Regarding  the  stakeholder 
responses,  six  did  not  provide  any  feedback,  despite  the  engagement  efforts.  Another  two 
stakeholders  submitted  their  responses  to  the  survey  with  the  content  blank.  A  segment 
comprising two stakeholders indicated their unavailability due to holidays or mentioned potential 
engagement at a later date. Additionally, three stakeholders, recognised the intent of the study 
but deemed themselves less relevant, and proposed that other individuals be contacted for more 
pertinent insights. 

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5  RESULTS 

5.1  Literature review 

The literature review in this study explored the role of the Professor Luiz Saldanha Marine Park in 
improving marine biodiversity and fisheries’ sustainability. Its results show that spillover from the 
Professor Luiz Saldanha Marine Park affects both ecological and socio-economic outcomes.   

Several  studies  have  examined  how  the  MPA  in  Arrábida  аffeсts  loсаl  communities,  primarily 
focusing  on  the  fishing  sector.  Every  study  emphasized  how  vitаl  it  is  for  аll  stakeholders, 
especially the local fishers, to be involved in the decision-making аnd management procedures of 
the  MPAs.  Vаsсonсelos'  research  (2012)  examined  the  adoption  of  а  collaborative  governance 
model within the MPA (MARGov), а response to the disagreements initiated by the establishment 
of the park. The MARGov project instigated a participatory approach among stakeholders, notably 
the direct users of the MPA, cultivating a sustainable and constructive exchange (Vasconcelos et 
al., 2012). The project utilized negotiation techniques and collective decision-making to encourage 
the  development  of  'pedagogic  development’,  thus  enhancing  the  process  with  the  input  and 
learning  experiences  of  all  involved  parties.  This  methodology  matured  across  four  phases  - 
identifying stakeholders,  initiating individual meetings,  organizing collective sessions, and joint 
planning - leading to, as per Vasconcelos et al. (2012), more effective and enduring solutions in 
managing protected areas. The 2013 study by Marques pointed out that when MPA rules were 
imposed  top-down,  it  led  to  conflicts,  especially  among  the  local  fishers  who  depend  on  the 
protected region for their livelihood. While both recreational boaters and commercial fishers, who 
depended heavily on the area for their economic well-being, showed some resistance against the 
MPA  restrictions,  the  researchers  also  highlighted  a  mutual  recognition  of  the  MPA's  role  in 
protecting coastlines, safeguarding biodiversity, and ensuring ongoing fishery resources (Marques 
et al., 2013). 

Stratoudakis  et  al.  (2015a)  assessed  the  effects  of  the  MPA  on  the  local  small-scale  fishing 
community, several years after the phased introduction of regulation. They gathered information 
and  viewpoints  from  MPA  fishers  regarding  the  ecological,  socio-economic,  and  governance 
conditions in the MPA. Ecologically, most indicators remained unchanged, and there was a non-
significant decline in the abundance of target species. The socio-economic and governance results 
indicated  a  general  sense  of  pessimism,  although  the  reasons  for  this  pessimism  or  potential 
solutions were not explicitly identified. Interestingly, despite the majority of fishers expressing a 
reluctance  for  their  descendants  to  pursue  fishing  and  indicating  a  preference  for  the  pre-
regulation conditions, they  also recognized the significance  of the MPA license. Moreover, they 
were aware of others' interest in obtaining this license and believed that co-management with the 
MPA  authority  was  the  most  effective  approach  to  fishery  management  (Stratoudakis  et  al., 
2015a). Another study by Stratoudakis et al. (2015b) explored the perspectives of users regarding 
the evolution of the MPA  and its relationship with small-scale fisheries up to 2012, revealing a 
generally positive perception. However, some socioeconomic concerns emerged, particularly as 
perceived  advancements  in  understanding  and  disseminating  information  about  the  MPA  were 
counteracted  by  a  perceived  decline  in  the  excluded  fishers'  ability  to  sustain  their  livelihoods 
from fishing, along with a diminished appeal of fishing as a career for the younger generation. 
Stratoudakis et al. (2015b) also observed a disparity in perceptions regarding ecological matters, 
with MPA fishers failing to recognize the improvements noted by other users. Nonetheless, there 
was  consensus  on  socioeconomic  and  governance  issues,  encompassing  both  indicators  of 
progress and signs of deterioration (Stratoudakis et al., 2015b). 

Pita  et  al.  (2020)  recently  investigated  fishers'  perceptions  within  the  Professor  Luiz  Saldanha 
Marine Park, comparing attitudes before and after full park management implementation. They 
found that despite an increase in fishers' knowledge about the MPA, dissatisfaction persisted over 
the years.  Many fishers believed  their fishing  activities were  negatively affected, with a rise  in 
fishing  days  and  a  drop  in  catches  reported  by  around  42%  of  them.  Fishers’  acceptance  and 
support for the MPA did not increase: the proportion of fishers unhappy with the park's creation 
rose from 65% in 2007 to 73% in 2015. The proportion of fishers reporting a negative impact of 
the MPA on their fishing interests decreased from 96% in 2005 to 85% in 2015, but only a small 
percentage believed the park improved fisheries management, and this percentage declined over 
time.  Fishers  raised  multiple  concerns  during  the  MPA's  implementation:  a  perceived  negative 
impact  on  their  fishing  opportunities,  poor  fishery  management,  overcrowding,  excessive  park 
regulations, and limited participation in the decision-making process. Changes in fishing behaviour 
and concerns about exclusive access for local fishers were also major sources of contention. These 

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findings underscore the need for fishers to have a more significant role in decisions, given their 
perceived lack of benefits from the MPA. 

Between  2003  and  2022,  there  was  a  fluctuation  in  the  number  of  fishers  in  Sesimbra  port 
registered for multi-gear, permissible in specific zones of the MPA (Figure 3). The data indicate 
an initial increase up to 980 fishers in 2005, the year the MPA was implemented. After 2005, the 
number of fishers decreased down to 732 in 2012. A temporary rise occurred between 2013 and 
2015, peaking at 952. By 2022, the number had significantly decreased to only 416, a substantial 
reduction  compared  to  the  number  of  fishers  in  2005.  Concurrently,  the  declining  number  of 
registered  fishers  in  Sesimbra  port  from  2005  to  2022  post-MPA  inception  underscores  the 
potential  conservation  measures'  effects  on  fishing,  corroborating  the  fishers’  dissatisfaction 
identified by several authors such as Stratoudakis et al. (2015a) and Pita et al. (2020). 

Figure 3. Number of fishers registered for multi-gear fishing in the Sesimbra port (Nº) 
per Year (Source: Instituto Nacional de Estatística) 

Creating  no-take  MPAs  that  restrict  fishing  can  change  fish  community  structures,  as  seen  in 
studies  by  Halpern  (2003)  and  Claudet  et  al.  (2008).  Such  shifts  become  apparent  within  a 
relatively brief period, often within 4 to 6 years, as outlined by Sousa's 2011 study concerning 
the Professor Luiz Saldanha Marine Park. In understanding the human responses, Horta e Costa 
et al. (2013) explored how artisanal fishers adapt to MPAs.  

The research found that fishers adjust their efforts, picking new spots to fish and shifting closer 
to the boundaries of restricted zones. The study also showed that the choice of fishing gear is 
affected by many factors, ranging from the preference for specific species and proximity to ports 
to modifications in MPA regulations. Furthermore, every fishing group responded differently to the 
MPA  rules,  adjusting  their  operations  to  align  with  the  new  guidelines.  Looking  closely  at  the 
Arrábida  region,  Horta  e  Costa  et  al.  (2013)  dug  into  the  complex  relationships  among  the 
different fisheries. Factors such as the vicinity of ports, climatic conditions, and distance from the 
coast  played  pivotal  roles  in  dictating  fishing  behaviours.  For  example,  buoy-directed  nets, 
influenced by their efficiency and environmental restrictions, saw prominent use close to home 
ports.  In  contrast,  traps,  owing  to  their  adaptability  to  weather  changes,  found  utilization  in 
diverse locations. The research highlighted how closeness to the coast plays a role in the choice 
of fishing gear, noting that jigs are mainly used closer to shore, showcasing the strategies of local 
fishers (Horta e Costa et al., 2013). 

For  more  than  a  decade,  the  Professor  Luiz  Saldanha  Marine  Park  has  been  a  focal  point  for 
extensive  research.  Between  2010  and  2019,  the  park  underwent  14  experimental  fishing 
expeditions  as  a  part  of  various  monitoring  programs  like  BIOMARES,  BUFFER,  and 
INFORBIOMARES, aimed at observing the soft-substrate demersal fish community (with a break 
from 2015 to 2018 due to funding constraints) (Figure 4). 

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Figure 4. Timeline of events associated with the Professor Luiz Saldanha Marine Park 
(Source: Pita et al., 2020). 

Borges (2006) pointed out that the MPA serves as  a breeding ground for many nearshore and 
shelf-dwelling species such as sardines. The author speculated that the conservation efforts in the 
park might increase  larval supply by encouraging spawning  from  adults, which could indirectly 
benefit external fishing grounds. Henriques et al. (2014) examined the rich biodiversity of benthic 
assemblages, pointing out that environmental factors play an important role in the distribution of 
these assemblages. 

The establishment of the MPA had various impacts, as explored by Abecassis et al. (2015) and 
Batista  et  al.  (2011),  affecting  from  individual  species  to  entire  fisheries.  Multiple  studies, 
including those by Gonçalves et al. (2003), Sousa (2011), and Henriques et al. (2013), agree that 
there was an increase in fish diversity and species count in the protected zones. In concurrence, 
Martínez Ramírez et al. (2021) observed certain reserve effects when categorizing fish by their 
commercial value and size. Their research divulges a decline in fish abundance following the MPA's 
implementation,  pinning potential  reasons on socioeconomic factors. Parallel to these  findings, 
Batista et al. (2015) tackled the impact of MPAs on fisheries, surmising that the recovery of coastal 
fisheries  remains  uncertain  due  to  practical  challenges  and  the  nature  of  the  protected  areas. 
Meanwhile,  Horta  e  Costa  et  al.  (2013b)  researched  the  MPA's  influence  on  fish  density  and 
biomass.  The  authors  suggested  that  the  "reserve  effect"  positively  impacts  the  sizes  and 
densities  of  certain  commercial  species  within  the  protected  area.  Lastly,  Sousa  et  al.  (2018) 
found that after full MPA implementation, there was a notable increase in fish biomass within the 
MPA, demonstrating the positive impact of reduced fishing mortality and prolonged fish longevity. 

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Figure 5.  Patterns of spatial utilization for fish tagged with passive acoustic telemetry 
within the MPA (Adapted from Gonçalves et al., 2015) 

Abecassis  et  al.  (2014b)  used  passive  acoustic  telemetry  to  show  that  some  species,  like  the 
Senegalese sole (Solea senegalensis), often venture beyond MPA borders. They underscored the 
need to look at individual species when evaluating the effectiveness of an MPA. Gonçalves et al. 
(2015) reported on the beneficial ecological effects of conservation, particularly for fish such as 
the white seabream (Diplodus spp). Seabreams occupy relatively small areas within the Marine 
Park, showing high fidelity to specific sites and remaining in the same zones for periods exceeding 
a year (within areas of higher protection) (Figure ). Abecassis et al. (2014a) also engaged in a 
discourse  on  spillover  effects,  noting  that  while  larger  fish  might  venture  out  of  MPAs,  this 
phenomenon  might  not  extend  universally.  This  is  corroborated  by  Gandra  et  al.  (2018),  who 
further  revealed  that  some  soles  benefit  directly  from  MPAs  due  to  their  sedentary  nature, 
suggesting that small no-take areas could be protective, while more mobile soles might indirectly 
benefit from the spillover effect. Sousa (2019) also leveraged acoustic telemetry to determine the 
differential benefits of the MPA for the endangered white skate and emphasized the differential 
benefits of MPAs, highlighting that protective measures may not uniformly benefit all individuals 
within a species. 

From  a  zoning  perspective,  Cunha  et  al.  (2014)  discerned  that  species  size  and  biomass  are 
considerably  influenced  by  different  protection  levels.  Sousa's  2011  research  highlighted  how 
different substrate types play a key role in shaping marine biodiversity and explored the potential 
impact  of  fishing  methods  on  species  diversity.  Both  Cunha  et  al.  (2014)  and  Sousa  (2011) 
emphasized how the park's designated zones affect marine life. They pointed out that the variety 
and number of fish are tied to the level of protection, the kind of habitat, and the fishing methods 
used. Despite indicating a possible spillover effect, these studies highlighted the need for more 
research to verify this hypothesis. Interestingly, the notion of the spillover effect is also discussed 
in other studies including those by Abecassis et al. (2014a) and Abecassis et al. (2015). These 

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works suggest that while spillover could alleviate the pressure of fishing, its realization may vary 
depending on the species and their respective home ranges. 

5.2  Stakeholder perceptions 

For this study, several stakeholders were invited to participate through a questionnaire, sharing 
their  insights  on  the  spillover  effects  in  the  MPA.  The  response  rate  was  low,  as  only  five 
respondents completed the questionnaire. The main reasons for non-participation were most likely 
holidays,  perceived  irrelevance  of  the  stakeholder's  knowledge  of  the  survey  topic,  or 
unavailability during the survey period. The five respondents comprised of two respondents from 
the research sector, two from the fisheries sector and one from a government authority. 

One of the researchers who participated gave a general overview and highlighted that the MPA's 
management plan has specific rules, particularly around commercial fishing, and mentioned that 
these restriction zones were created based on research studies regarding the characteristics  of 
the area and species distribution patterns. He stated that he had used underwater visual census 
(UVC)  and  statistical  analysis  methods  to  analyse  changes  in  biodiversity  and  fish  abundance 
numbers  within  the  MPA.  He  mentioned  that  after  the  establishment  of  the  MPA,  noticeable 
ecological changes were observed, and the habitats within the MPA had become more complex, 
with  a  notable  increase  in  the  density  and  diversity  of  algae  coverage.  Additionally,  larger 
individual organisms are predominantly found in zones where fishing is prohibited. Despite these 
habitat changes, the stakeholder considered that there had been no discernible alteration in fish 
abundance or biomass either within or outside the MPA but he considered that it was likely that 
spillover was occurring from both fully protected and partially protected areas and that 
it had a moderate influence on the catch composition. Regarding the impact on fishers' catches 
post-MPA establishment, his response is neutral, with the stakeholder mentioning a lack of specific 
data to make a concrete assessment. 

The  second  researcher  discussed  both  the  size  of  the  park  and  its  management  strategies.  In 
addition to the UVC, this stakeholder also utilized Baited Remote Underwater Videos (BRUV) in 
his studies which facilitated data collection on fish species within the marine park. His findings 
showed an increase in the diversity, biomass and abundance of fish species which he attributed 
to  the  fishing  restrictions  currently  in  place  in  the  protected  area.  For  him,  there  is  a  high 
probability  that  spillover  from  the  fully  protected  areas  is  occurring  and  that  this 
phenomenon  seems  to  have  greatly  influenced  the  catch  composition  in  neighbouring  fishing 
grounds, as data indicates a significant increase in catches at the Sesimbra auction following the 
MPA's implementation. Furthermore, according to him, the establishment of zones with limited 
fishing has undeniably raised the revenues for fishers. Yet, on the subject of whether the fishing 
community  feels  more  secure  about  their  livelihoods  post-MPA,  his  opinion  is  neutral.  He  also 
added that the MPA's implementation was faced with criticism because it was imposed with force 
but that fishers have been recognizing its benefits over the last decades. 

Two representatives from the Sesimbra fishing community described their fishing practices and 
target species. The first fisherman explained that his fishing methods included the use of traps, 
trammel nets, gillnets, hooks and lines, and jigs. He targeted species like the red mullet (Mullus 
surmuletus), breams (Diplodus spp), octopus (Octopus vulgaris), skates (Raja spp), and seabass 
(Dicentrarchus labrax). The stakeholder showed that he knew the rules and management of the 
MPA  very  well  and  highlighted  changes  in  fishing  areas  after  the  MPA  was  set  up.  He  also 
expressed doubts about the idea that catches were better after the MPA and disagreed 
with  the  view  that  the  local  fisheries  had  gained  economically  from  the  MPA.  He  was 
sceptical about the usefulness of MPAs as conservation tools, believing that the MPA did not help 
the local fishing industry or the jobs connected to it. The second response from the fisheries sector 
described similar fishing methods but added species like the Common cuttlefish (Sepia officinalis), 
Squid (Loligo spp.), Sole (Solea spp.), hake (Merluccius spp.), Brill (Scophthalmus rhombus), and 
some other flatfishes and crustaceans to the list of targeted species. This fisherman also knew 
the MPA rules and management well and described the changes he noticed after the MPA started. 
He mentioned shifts in fishing areas and a decrease in active licenses which is in accordance with 
the INE data. Like the first stakeholder from the fisheries sector, he also did not believe that the 
MPA necessarily led to more catches or better economic outcomes for fishers and was doubtful 
about  the  overall  effectiveness  of  MPAs  for  conservation.  Both  individuals  representing  the 
fisheries sector expressed their concerns regarding the effects of recreational and tourism-related 
fishing within the MPA and that these activities could create potential challenges. These outcomes 
suggest that these stakeholders  have a negative perception of the  MPA's influence on fisheries 
and livelihoods. 

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The  Portuguese  governmental  authority  response  confirmed  that  there  is  a  comprehensive 
management  plan  for  the  MPA,  dating  back  to  2005,  in  which  'spillover'  is  not  explicitly 
incorporated into the conservation objectives. The stakeholder acknowledges the MPA’s vital role 
in species conservation  and activity regulation  despite  the restrictions zones currently in place 
still permitting specific fishing  activities within the MPA. He said that the MPA has witnessed a 
positive impact, with observed increases in species diversity, individual counts, and biomass, all 
of  which  highlight  the  potential  benefits  of  the  protected  area.  The  fisheries  management 
authority supports the efficacy of MPAs as a conservation strategy and believes in the 
presence of spillover effects, attributing these effects to factors such as MPA size, years since 
establishment,  protection  level,  and  habitat  type.  The  stakeholder  also  mentions  that  the 
magnitude of the spillover effects is detectable a few kilometres from the border of the MPA. 

6  DISCUSSION 

Our  case  study  on  the  Professor  Luiz  Saldanha  Marine  Park  corroborates  previous  research, 
offering valuable insights on the presence and occurrence of spillover. By analyzing the literature 
and  the  views  of  researchers,  government  officials,  and  fishers,  we  investigated  the  potential 
spillover effects of the MPA. 

Several  significant  ecological  changes  in  terms  of  fish  diversity,  species  numbers  and  biomass 
have  been  observed  since  the  MPA  implementation,  both  within  its  boundaries  and  in  its 
surrounding  areas.  The  significant  increase  in  these  variables  within  the  protected  zones,  as 
confirmed by Gonçalves et al. (2003), Sousa (2011), and Henriques et al. (2013), confirms the 
positive  influence  of  the  MPA.  Martínez  Ramírez  et  al.  (2021)  found  that  fish  abundance 
experienced a decline following the MPA's implementation, suggesting a possible link with socio-
economic factors. Nonetheless, the notion of the "reserve effect," as explored by Horta e Costa 
(2013)  and  Sousa  (2011),  seems  to  indicate  that  MPAs  can  have  positive  outcomes,  such  as 
increased sizes and densities of certain commercial fish species. 

There are different perspectives from various stakeholders including researchers and local fishers 
on how fishers' catches changed. The consensus among researchers and the government 
official  surveyed,  is  that  the  MPA  has  brought  positive  ecological  results,  especially 
spillover.  For  instance,  a  respondent  underscored  that  his  studies  within  the  Professor  Luiz 
Saldanha  Marine  Park  have  consistently  demonstrated  positive  shifts  in  species  diversity  and 
abundance, corroborating the overall effectiveness of MPAs in fostering ecological recovery. These 
insights are rooted in studies that showcase increased species richness and diversity indices within 
MPAs, corroborated by works like Halpern (2003), Claudet et al. (2008), and Sousa (2011). 

Conversely, local fishers express scepticism and dissatisfaction, echoing the findings of Pita 
et al. (2020). Concerns about reduced catches and negative economic consequences post-MPA 
align  with  these  stakeholders'  viewpoints.  The  drop  in  the  number  of  registered  fishers  in  the 
Sesimbra port after the MPA's inception supports the idea that conservation measures influenced 
fishing activity. These outcomes underscore the need to reconcile differing viewpoints to develop 
efficient management approaches. 

Fisheries management within the MPA has been a topic of debate and disagreement. Vasconcelos 
et al. (2012) and Marques et al. (2013) highlight the challenges arising from top-down imposition 
of  MPA  rules,  leading  to  conflicts  with  local  fishers.  The  lack  of  recognition  of  the  MPA's 
benefits among fishers also points to the importance of stakeholder engagement. While 
some stakeholders acknowledge the potential conservation advantages of the MPA, the inherent 
difficulties in balancing conservation goals with the socioeconomic needs of local fishers persist. 
The cooperative governance framework suggested by Vasconcelos et al (2012) presents a viable 
resolution, advocating for the inclusion of all stakeholder voices in the decision-making process. 

The spillover regarding the MPA, whereby the positive effects of MPAs extend to nearby areas, is 
an important concept that has been discussed extensively in the literature (Abecassis et al. 2014a, 
Abecassis et al. 2015) as well as the necessity of creating strategies that consider specific species, 
habitats, and external elements. Spillover effects, often a major focus when talking about how 
the MPA impacts local fisheries, are still a topic of debate. Some researchers argue its existence 
and potential benefits while others, like Abecassis (2014b), caution against assuming it applies 
universally to all species. The studies by Abecassis et al. (2014b) and Gandra et al. (2018) on 
species like  the  Senegalese  sole  and  the  white  seabream  suggest  that  some  fish  may  venture 
beyond MPA borders, potentially benefiting external fishing grounds, a point also raised by Borges 
(2006).  The  divergent  perspectives  of  stakeholders  further  emphasize  this  dichotomy.  While 

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scientists highlight the probable advantages of spillover for nearby fishing areas and 
local economic benefits, fishers voice scepticism about its efficacy. One fisherman voiced 
that  MPAs  can  be  a  double-edged  sword  for  them:  although  they  might  help  fish  populations 
recover, they restrict fishers’ access to traditional fishing zones. This raises questions about the 
specific species and scenarios for which spillover might be relevant and highlights the importance 
of considering context and ecological nuances. 

The evolution of MPA governance models, as demonstrated by studies by Horta e Costa et al. 
(2013),  Vasconcelos  et  al.  (2012),  and  Marques  (2013),  underscores  the  shift  towards  more 
inclusive  decision-making.  One  fisherman  suggested  that  collaboration  with  local  fishing 
communities in designing MPA regulations could be a way forward. The study from Pita 
et al.  (2020)  also corroborates this, emphasizing  that fishers desire  a greater role in decision-
making.  This  suggestion  to  collaborate  with  local  fishing  communities  in  designing  MPA 
regulations, in line with Vasconcelos et al. (2012) and Stratoudakis (2015), highlights a potential 
solution. This way, their input could be considered, and the negative impacts on their livelihoods 
minimized.  In  order  to  enhance  strategies,  for  managing  MPAs  it  would  be  advantageous  to 
promote  authentic  collaboration  that  effectively  addresses  ecological  and  socio-economic 
concerns.  

As  our  case  study  notes,  and  as  further  corroborated  by  Cunha  et  al.  (2014),  there  are  also 
overarching  challenges  in  the  practical  implementation,  monitoring,  and  enforcement  of  MPA 
regulations.  A  governmental  stakeholder  cautioned  that  the  practical  implementation  of 
regulations is an  ongoing  challenge  and that  effective  enforcement and compliance monitoring 
remain elusive. 

A potential limitation of this study is the  low number of stakeholders surveyed and  the lack of 
participation from a non-governmental organization. In future, engaging more stakeholders could 
potentially offer a more comprehensive representation of perspectives. 

7  CONCLUSIONS 

The way  well-structured MPAs can  promote  marine biodiversity  and generate positive spillover 
effects was demonstrated in both the existing literature on the MPA and the stakeholder responses 
from  researchers  and  governmental  authorities.  Yet,  stakeholders  from  the  fishing  community 
shared their concerns about the potential socio-economic repercussions of MPAs. Although MPAs 
are understood to potentially enhance fish populations, there is a concurrent sentiment that they 
might  negatively  influence  commercial  fishing  methods  and  the  related  economic  dynamics. 
Stakeholders in the fishing community stressed the importance of creating MPA regulations with 
their views and needs in mind and highlighted issues introduced by fishing activities associated 
with tourism within MPAs. It is understood that MPAs serve a dual purpose, functioning not only 
as a conservation tool but also as a tool for managing fisheries. However, there seems to be a 
division in opinions about which role should be emphasized more. The ecological benefits of the 
Professor  Luiz Saldanha Marine  Park  are  evident, but  this area  must be  managed in  a manner 
that  balances  both  conservation  needs  and  socio-economic  considerations.  Although  some 
scientific evidence has been identified on spillover in the literature, future research is necessary 
in  order  to  gain  a  comprehensive  understanding  of  the  spillover  effects  of  the  Professor  Luiz 
Saldanha Marine Park.  

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13. . CASE STUDY REPORT: 

FORMIGAS MARINE PROTECTED AREA 

PORTUGAL – MACARONESIA 

Analysis of potential spillover effects around the 
Formigas Marine Protected Area 

Sérgio Abreu 

MRAG Europe

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TABLE OF CONTENTS 

1 
2 
3 
4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ......................................................................................... 209 
BACKGROUND .................................................................................................... 209 
AIMS AND OBJECTIVES ....................................................................................... 211 
METHODOLOGY .................................................................................................. 211 
Literature review ....................................................................................... 211 
4.1 
4.2  Stakeholder questionnaire .......................................................................... 212 
RESULTS ........................................................................................................... 212 
Literature review ....................................................................................... 212 
5.1 
5.2  Stakeholder perceptions ............................................................................. 213 
DISCUSSION ..................................................................................................... 214 
CONCLUSIONS ................................................................................................... 215 
REFERENCES ..................................................................................................... 216 

LIST OF ABBREVIATIONS 

Term 

AMN 

BALA 

DLR 

DRA 

Description 

Autoridade Maritima Nacional 

Biodiversity at Azores' Lava Formations 

Decreto Legislativo Regional (Regional Legislative Decree) 

Direção Regional do Ambiente (Regional Directorate for the Environment) 

DRAM 

Direção Regional dos Assuntos do Mar (Regional Directorate for Sea Affairs) 

EU 

European Union 

GAMPA 

Grupo de Ação para o Mar dos Açores (Azores Marine Action Group) 

GNR 

IUCN 

IRP 

MPA 

Guarda Nacional Republicana (National Republican Guard) 

International Union for Conservation of Nature 

Inspeção Regional das Pescas (Regional Fisheries Inspection) 

Marine Protected Area 

MONIAVES 

Programa  de  monitorização  de  populações  de  aves  marinhas  dos  Açores 
(Monitoring Program of Marine Birds in the Azores) 

MONIZEC 

Monitoring of Marine Fish and Invertebrates in the Azores 

MSFD 

eNGO 

PAF 

PIMA 

SCI 

SAC  

Marine Strategy Framework Directive  

Environmental Non-Government Organisation 

Prioritized Action Framework 

Projecto Invasoras Marinhas (Marine Invasive Species Project) 

Site of Community Importance 

Special Area of Conservation 

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1  EXECUTIVE SUMMARY  

This  case  study  aims  to  investigate  whether  spillover  effects  have  been  detected  around  the 
Formigas Marine Protected Area (MPA) in the Azores region. This work utilised both a literature 
review of the available research and a questionnаire-bаsed method. The questionnaire tаrgeted 
а  wide  rаnge  of  stakeholders:  commercial  and  recreational  fishers,  fisheries  managers, 
government authorities, scientists and environmental non-government organisations.  

The  literature  review  revealed  that  the  Formigas  MPA,  due  to  its  unique  underwater  mountain 
habitat and geographical isolation, holds distinct  ecological features and  an overall  low  human 
impact. Findings showed that there is little direct evidence that the Formigas MPA has substantially 
impacted the marine communities within it, and no quantitative evidence that spillover effects are 
occurring from this MPA. Despite a limited range of studies on the MPA, there is likely the existence 
of potential spillover effects on another MPA in the Azores, with minor migration of fish from MPA 
to adjacent (non-MPA) areas.  

There  was  a  lack  of  response  to  the  questionnaire  by  stakeholders  that  were  approached. 
Nevertheless,  some  valuable  information  was  obtained  through  a  few  stakeholders.  A  key 
governmental authority that was interviewed mentioned the potential spillover effects of the MPA 
on adjacent fisheries and the recovery of overexploited fish populations within and surrounding 
the  MPA.  In  contrast,  one  diving  school  stakeholder  expressed  concerns  about  the  decline  in 
marine resources within the MPA over the past decade and the lack of enforcement.  

Future research on the Formigas MPA should concentrate on quantitatively measuring spillover 
effects, utilizing statistical models to track biomass and diversity changes in adjacent areas. This 
focus will enable a precise evaluation of how protected zones influence surrounding ecosystems 
and  fisheries,  providing  a  clear  metric  for  conservation  efficacy  and  resource  management. 
Overall,  this  work  highlighted  the  potential  interdependence  between  marine conservation  and 
socio-economic  benefits  associated  with  the  MPA,  but  also  highlight  the  need  for  further 
examination of the ecological and fisheries effects of the MPA.  

2  BACKGROUND 

The Azores is a volcanic archipelago composed of nine volcanic islands. These islands hold limited 
shallow-water habitats, are impacted by strong tidal currents and swell, and  are structured by 
substantial  ecological  isolation  of  its  island  habitats  and  the  populations  utilising  such  habitat 
(Santos et al., 1995; Tempera, 2008). 

The Azores have achieved notable recent success in marine conservation, with substantial growth 
and strengthening of protection efforts in the last decade. According to Abecassis et al. (2015), 
the evolution of marine protected areas (MPAs) in the Azores has undergone three stages: the 
1980s marked the initial creation of isolated MPAs, the 1990s saw the influence of international 
initiatives  fostering  research  and  conservation  policies,  and  the  2000s  saw  the  adoption  of  a 
holistic  approach,  acknowledging  the  necessity  to  incorporate  MPAs  into  a  broader  marine 
management strategy.  

Since  the  1980s,  the  Azores  have  led  the  way  in  seamount  ecosystem  conservation.  The  first 
European offshore MPA was established here, specifically encompassing the Formigas Islets and 
the  Dollabarat  Reef  (Santos  et  al.,  1995).  Following  this,  in  2004  a  crucial  coastal  zone 
management instrument gained approval, setting the stage for more comprehensive conservation 
efforts. Within 2006, the Natura 2000 network sectorial plan was enforced within the Azores. Then 
in  2007, a thorough review of the Azores  protected  areas network  took place, resulting  in  the 
improvement  of  conservation  strategies.  Between  2008  and  2011,  the  establishment  of  nine 
island natural parks was undertaken, with each island in the archipelago being allocated a park. 
2010  saw  the  creation  of  the  Regional  Directorate  for  Sea  Affairs  (DRAM),  established  by  the 
Regional Decree no.17/2010/A of September 21, which emerged as the environmental authority 
for the Azores. In  2011, the Marine Park  of  the  Azores was created, while  in 2012, the  region 
introduced  a  detailed  regional  biodiversity  law,  merging  both  conservation  and  biodiversity 
initiatives. The same year also saw the approval of the final coastal zone management instrument, 
ensuring  that  all  islands  had  a  robust  framework  in  place.  In  2013  the  implementation  of  the 
Prioritized Action Framework (PAF) of Natura 2000, further  amplified conservation endeavours. 
Emphasizing  a  broader  perspective,  2014  witnessed  the  full  implementation  of  the  Marine 
Strategy  Framework  Directive  (MSFD)  in  the  Azores,  indicating  the  region's  commitment  to 

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aligning  with  conservation  directives.  In  2016,  the  Marine  Park  of  the  Azores  underwent  an 
extensive review which led to a 122 % enlargement of its area.  

The natural park of the island of Santa Maria, with its marine component, includes two natural 
reserves  -  the  Formigas  Islets  and  the  Vila  Islet,  and  three  protected  areas  for  resource 
management - São Lourenço Bay, the North Coast and the South Coast. The establishment of the 
natural park of the island of Santa Maria was motivated by the necessity to protect the island's 
distinct biological and geological attributes, as well as its paleontological heritage (Lopes et al., 
2019).  

The Formigas MPA, also known as the Reserva Natural dos Ilhéus das Formigas, is situated in 
the northeastern part of the Azores, approximately 43 kilometres northeast of Santa Maria Island 
(Figure 1).  The  MPA  encompasses  the  Formigas  Islets  and  a  submerged  seamount  named  the 
Dollabarat Bank. The MPA is divided into two zones:  

1.  the core zone, which includes the Formigas Islets and the surrounding waters up to a depth 
of 100 meters, where no-take restrictions are enforced to preserve marine biodiversity; and  

2.  the buffer zone, which extends from the edge of the core zone to the outer boundary of the 
MPA (DRAM, 2022). This buffer zone is subject to specific regulations that manage activities 
such  as  fishing  and  vessel  traffic,  aiming  to  minimize  human  impact  while  allowing  for 
sustainable use of the area's resources (DRAM, 2022). 

Figure  1.  Geographic  location  of  the  Azores  Islands  and  the  Formigas  MPA  (Source: 
Christiansen and Tempera, n.d.). The dark blue area is the core zone (Nature Reserve), 
the light blue area is the buffer zone (Special Area of Conservation). 

Established in 1988, the Formigas MPA is a vast marine sanctuary, spanning 57.4 km2 (Regional 
Decrete n° 11/88/A). This MPA is home to a diverse array of habitats, from deep bathyal plains 
at the seamount's base, around 2,300 m deep, to shallow rocky outcrops. The seamount's shallow 
reefs alone, which are less than 50 m deep, cover an area of 3.26 km2. The Formigas MPA is also 
characterized by its rich  marine  biodiversity,  holding  coastal  and oceanic marine communities. 
Species  which  have  been  identified  within  the  MPA  include  loggerhead  sea  turtles  (Caretta 
caretta),  cetaceans,  tuna,  pelagic  sharks  (e.g.,  the  smooth  hammerhead,  Sphyrna  zygaena), 
whale shark (Rhincodon typus), and a range of ray species (Lopes et al., 2019).  

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Initially, fisheries restrictions within the MPA only encompassed coastal habitats less than 200 m 
deep; fishing was still permissible in habitats deeper than 200 m for vessels under 11 m. However, 
a regulatory revision in 2003 led to a substantial expansion of the MPA's boundaries, which now 
encompass the entire seamount down to its base. The protection status was also bolstered, with 
fishing within the MPA restricted to just pelagic pole-and-line fishing for tunas. Importantly, the 
MPA's  management  plan  includes  measures  to  protect  the  area's  biodiversity,  regulate  human 
activities,  and  monitor  the  health  of  the  ecosystem  (DRAM,  2022).  In  this  MPA,  the  following 
activities  are  strictly  prohibited:  (a)  underwater  spearfishing,  harvesting,  or  collecting  marine 
organisms,  with  or  without  the  aid  of  a  vessel;  (b)  disturbance  of  nesting  seabirds;  (c)  waste 
disposal; and (d) fishing, except for commercial handline or pole-and-line fishing targeting tunas 
by vessels equipped with the MONICAP continuous fishing activity monitoring system, subject to 
prior binding approval from the Regional Fisheries Inspection. 

The Formigas MPA is internationally recognized under the RAMSAR convention and is part of the 
Natura  2000  network  (European  Commission,  2021).  Within  this,  the  Formigas  Islet  Natural 
Reserve  is  classified  as  an  International  Union  for  Conservation  of  Nature  (IUCN)  Category  Ib 
protected area, an MPA - SMA01, a Site of Community Importance/Special Area of Conservation 
(SCI/SAC – PTSMA0023), and a Ramsar site (No. 1804 — Ilhéus das Formigas e Recife Dollabarat) 
and covers a 0.30 km² area within the territorial sea. The SMA01 area's protection is justified by 
its inherent natural value and its significance for safeguarding protected species, habitats, and 
ecosystems,  as  it  includes  the  objectives  and  territorial  boundaries  defined  for  SCI  Ilhéus  das 
Antas and Recife Dollabarat (PTSMA0023) (Lopes et al., 2019). 

This  study  is  propelled  by  the  critical  need  to  understand  how  MPAs  can  enhance  ecological 
networks  and  increase  fish  populations  outside  their  boundaries,  providing  lasting  benefits  for 
fisheries  management  and  surrounding  communities.  This  research  endeavours  to  better 
understand the spillover phenomenon and its wider consequences by combining findings from the 
literature  and  feedback  from  stakeholders.  We  aim  to  bridge  the  gap  between  theoretical 
understanding  and  practical  application,  contributing  significantly  to  marine  conservation 
discussions. However, it is important to clarify that the evaluation of policy frameworks was not 
included in the scope of this study. 

3  AIMS AND OBJECTIVES 

The main aim of this case study is to investigate whether spillover effects have been identified 
within and around the Formigas MPA. To achieve this, a multifaceted approach has been devised. 
Firstly, we examined the presence or absence of spillover effects within the Formigas MPA utilising 
a  comprehensive  review  of  existing  literature.  Subsequently,  we  then  identified  and  compiled 
evidence from the literature that substantiates the occurrence of spillover effects, if any, within 
and around  the  Formigas MPA.  Additionally,  we  sought  to  gather and  analyse  the  perceptions, 
opinions, and experiences of key stakeholders, including fishers, fisheries managers, scientists, 
and  environmental  organizations,  regarding  spillover  effects  in  the  Formigas  MPA  through  a 
questionnaire-based  approach.  More  specifically,  we  assessed  the  level  of  stakeholders' 
knowledge concerning the regulations governing the  Formigas MPA, with a particular emphasis 
on fishing restrictions. We also evaluated  how stakeholders perceive  the roles  of the  Formigas 
MPA,  specifically  as  a  conservation  tool  and  a  fisheries  management  instrument.  Finally,  we 
identified and explored the key factors that stakeholders associate with the occurrence or absence 
of spillover effects in the Formigas MPA.  

4  METHODOLOGY 

4.1  Literature review 

The literature review in this study was conducted using a thorough approach to provide an in-
depth  look  at  the  potential  spillover  effects  associated  with  the  Formigas  MPA.  The  research 
methodology  included  searching  in  databases  like  ScienceDirect,  SpringerLink  and  also  Google 
scholar  using  specific  keywords.  Additionally,  academic  journals  as  well  as  grey  literature, 
websites  and  recommendations  from  key  researchers  were  considered  to  identify  relevant 
publications  related  to  the  Formigas  MPA  and  the  region.  After  an  initial  scan  of  titles  and 
abstracts, the literature was narrowed down studies that focused directly on the Formigas MPA 
and that covered key themes, including spillover effects, fisheries and stakeholders.  

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4.2  Stakeholder questionnaire  

We  developed  a  detailed  questionnaire  to  assess  the  perceptions  of  key  stakeholders  on  the 
potential  spillover  effects  in  their  nearby  MPAs.  The  questionnaire  comprised  open-ended  and 
closed questions. Open-ended questions were developed to capture stakeholder opinions, while 
closed questions were statement-based and used Likert scale answer categories. Questions were 
grouped into four broad categories to encapsulate the key issues being studied (see Annex 4):  

•  Respondent  information:  Basic  information  on  the  name,  institution  and  role  of  the 

respondent requested. 

•  Background information: Background information requested to understand the respondent 
and  their  (potential)  use  of  the  MPA.  Questions  included  knowledge  of  when  the  MPA  was 
established, the type of restrictions in place and how long the stakeholder has been associated 
with the MPA either through research, fishing or managing it. 

•  Fishery  impacts  of  MPAs:  Respondent’s  perceptions  of  the  socio-economic  impacts  of 
spillover from the MPA were requested. Stakeholders were asked whether the designation of 
an MPA / area where fishing is limited has led to an increase in revenues for fishers, whether 
the fishing community in  the area  feel  their fisheries livelihoods are  more secure after the 
MPA  was  established,  and  the  extent  to  which  they  believe  spillover  from  the  MPA  has 
influenced the catch composition in adjacent fishing grounds. 

•  MPAs  as  management  tools:  The  respondent’s  perceptions  on  whether  MPAs  are 
conservation or fisheries management tools was requested. Stakeholders were asked to state 
whether their local MPA was acting as a conservation tool, a fisheries management tool or 
their 
both.  Other  questions  under 
agreement/disagreement on whether the establishment of MPAs is an effective conservation 
strategy to support fish populations and commercial fisheries in their area. Respondents were 
also asked to indicate what factors they thought were contributing to spillover effects. 

this  section  required  stakeholders 

to  state 

Four key stakeholder groups were targeted: (i) commercial and recreational fishers; (ii) fisheries 
managers and government authorities; (iii) scientists; and (iv) environmental non-government 
organisations (eNGOs). Further, to gain insights into the possible spillover effects, we engaged 
with  several  stakeholders  linked  to  the  Formigas  MPA.  We  emailed  23  stakeholders  and  sent 
follow-up  emails  to  14  to promote  their  involvement.  We  also  made  phone  calls  to  incentivise 
participation  among  various  stakeholder  categories.  Specifically,  we  reached  out  to  six 
representatives from regional fisher associations, five from governmental bodies, three academic 
researchers, four members of eNGOs, and five diving schools active within the MPA. Our outreach 
was conducted during July and August 2023. 

5  RESULTS 

5.1  Literature review 

Between 2014 and 2019, a range of scientific studies and monitoring initiatives were carried out 
in the Formigas MPA. These focused on various areas, including marine birds (MONIAVES), fish 
and  invertebrates  (MONIZEC  and  the  BALA  project  in  2016),  coastal  marine  biodiversity,  non-
native  species  (PIMA  project  in  2016),  as  well  as  work  examining  biodiversity,  sediments, 
cetaceans, and turtles within the Azores, reflecting the region's commitment to preserving marine 
ecosystems (Governo dos Açores, 2020). Importantly, the 2019 report from Grupo de Acção para 
o Mar dos Açores (GAMPA) emphasizes the uniqueness of the Formigas region. Formigas stands 
out for its distinct fish community, distinguished by the presence of rare pelagic and mesophotic 
species, attributed to the high cover of underwater mountain habitat. The Formigas MPA contains 
a very high species diversity, and while its macroinvertebrate diversity aligns with other regions, 
its high sea urchin abundance is remarkable. Uniquely, lacking a port, Formigas experiences fewer 
intrusions from non-native species than the Azores mainland.  

Despite the limited range of studies that have examined the Formigas MPA, there is a substantial 
dearth  of  studies  focusing  (or  even  encapsulating)  studies  that  examine  fishery  or  ecological 
spillover  from  the  MPA.  Despite  this,  there  is  evidence  from  the  Azores  (but  outside  of  the 
Formigas MPA), to show that at least one fisheries finfish species may show MPA site specificity 
for, but also potential spillover from  that MPA. Afonso et al. (2011) employed passive acoustic 
telemetry to examine the movement of dusky grouper (Epinephelus marginatus) within and across 
the Monte da Guia Marine Reserve (MGMR) located on the island of Faial in the Azores, which is 
approximately  366  kilometres  northwest  of  the  Formigas  MPA.  This  work  revealed  that  dusky 
grouper  displays  strong  site-specificity  to  this  MPA,  while  there  is  the  potential  for  a  spillover 

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effect  within  these  fish,  with  individuals  migrating  from  the  MPA  to  nearby  fishing  areas.  This 
small coastal marine reserve enforces full protection (no-take reserve) within two small sunken 
calderas (8 ha), while the immediate volcano perimeter enjoys partial protection.  Despite such 
movement of species, such behaviour was found to be limited to a 5 km radius from the  MPA. 
While this suggests that marine reserves may have limitations as a fisheries management tool for 
increasing harvestable yield through fish migration, the study ultimately underscores the crucial 
role small reserves play in protecting endangered species like the dusky grouper. 

The most recent examination of the Formigas MPA was undertaken as part of a wider study of the 
effects of MPAs, to determine the MPA impact on fish populations (Afonso et al., 2018). However, 
the  study  faced  a  significant  limitation  in  attesting  the  impacts  of  the  MPA,  as  there  was  no 
"before" data, with sampling started after the MPA was established, while there was no control 
area, as the full seamount is protected with no comparable unprotected habitat (Afonso et al., 
2018). The study focused on two of the main shallow reefs within the Formigas MPA, the Formigas 
islets  and  the  Dollabarat  reef.  These  two  sites  are  separated  by  6  km  and  a  stretch  of  water 
exceeding 80 m in depth (Afonso et al., 2018). The researchers were able to compare fish metrics 
between the two reefs over time, including “before” and “after” new 2003 restrictions came into 
place. This work showed that, although overall fish abundance showed a negative or unclear trend 
over time within the Formigas MPA, abundances of fish were significantly higher at the Dollabarat 
reef for both medium and large home range fishes. Lastly, the average size ratio in the Formigas 
MPA  was  only  significantly  different  in  the  case  of  benthopelagic  fishes,  indicating  a  potential 
reduction in size in this group after the revised protection. 

5.2  Stakeholder perceptions 

Two stakeholders were willing to take part in the study, one from the governmental authority and 
another from the fishing sector. Given the limited engagement from such traditional stakeholders, 
the consortium extended the outreach efforts to include established diving centres that have been 
operating within the MPA for an extended period. This approach aimed to gather insights from a 
different  angle  and  capture  the  perspective  of  entities  closely  connected  to  the  marine 
environment. In addition, a marine scientist representing a diving centre and the maritime tourism 
sector  also  provided  his  insights  on  the  MPA.  Interestingly,  the  fishing  sector  stakeholder 
inadvertently provided insights on another MPA within the Azores - the Marine Protected Area of 
Condor.  This  MPA  encompasses  the  Condor  Seamount,  an  underwater  mountain  located 
southwest of Faial Island, designated as a protected area within the Azores Marine Park in 2016.  

Of all the stakeholders contacted, eighteen stakeholders remained unresponsive. One stakeholder 
chose  not  to  contribute,  advising  us  to  seek  wider,  more  relevant  input.  Additionally,  two 
stakeholders visited the questionnaire site but chose not to fill out the questionnaire. Interestingly, 
the sole stakeholder from the government who participated proactively shared the link with five 
other  stakeholders,  some of  whom  we  had  previously  reached  out  to.  Despite  this,  even  after 
being prompted by a governmental authority, these stakeholders did not respond. The timing of 
our  outreach  conducted  during  July  and  August  2023,  which  are  typical  vacation  months  in 
Portugal, might have played a role in the unexpectedly low participation rate. 

The governmental authority that replied to the questionnaire mentioned that the Formigas MPA 
has had a management plan in place since 1988. This allows some level of fishing, with special 
authorization  for  pole  and  line  fishing  gear  at  the  MPA  border.  According  to  this  stakeholder, 
fishing primarily occurs at the MPA border. The extent of spillover effects from the MPA on 
adjacent  fisheries  is  perceived  to  be  significant  in  contributing  to  the  recovery  of 
overexploited fish populations, but the magnitude of such spillover and contributing factors 
which may lead to such spillover remain unspecified. The stakeholder strongly agrees that fishers' 
catches in the area are higher post-establishment of the MPA, resulting in economic benefits for 
local fisheries. The governmental authority believes that the MPA not only contributes to marine 
conservation but it also aids in fisheries management; this stakeholder was strongly in favour of 
permanently closing certain areas of the MPA for commercial fisheries development.  

Both  the  governmental  authority  and  fisheries  sector  stakeholders  consider  that  the  MPA 
contributes to both biodiversity protection and fisheries. The fisheries sector stakeholder, 
although inadvertently addressing the Condor MPA rather than the intended Formigas MPA, shed 
light with his insights on the dynamics of marine conservation within the Azores. The stakeholder’s 
observations noted marked shifts in fish abundance, biomass, and species composition within the 
MPA of Condor. He mentioned the migration of juvenile individuals from the MPA to other 
areas,  indicating  potential  spillover  effects.  This  stakeholder  expressed  a  strong 

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disagreement with the notion of increased revenues for fishers and improved livelihood 
security post-MPA establishment and diverged from the governmental authority's perspective. 
This difference in perspectives emphasises the complexity of assessing the socioeconomic impacts 
of MPAs.  

The diving school representative stressed the significant role that maritime tourism operators play 
in understanding the marine ecosystem. He pointed to the decline in marine resources that has 
been observed by operators and their clients for over a decade. The stakeholder observed that 
fishing activity is more intense during the off-season when diving operators are less active. He 
mentioned that in his perspective a larger MPA with stricter enforcement of regulations would be 
more effective. The respondent also believes the MPA is acting neither as an effective conservation 
tool  nor  a  fisheries  management  tool  due  to  its  inadequate  implementation.  Furthermore,  the 
respondent does not consider investigating spillover to be a research priority due to the 
MPA's current ineffectiveness and rates the likelihood of spillover as "very unlikely".  

The diving school representative pointed out that the MPA's supposed inefficiency and decline are 
due to poor management. The comparison of the MPA to areas outside of it further highlights the 
severity of the issue, as the external  areas were described as being “even worse”.   Within the 
MPA, the respondent notes a reduction in fish abundance and biomass, although the decline is 
comparatively  slower  than  in  the  surrounding  areas.  The  stakeholder  also  mentioned  the 
emergence  of  urchin  barrens  in  specific  zones  as  a  notable  transformation  within  the  MPA's 
ecosystem. 

6  DISCUSSION 

The Formigas MPA showcases unique ecological characteristics, including a diverse array of fish 
species and an exclusive underwater mountain habitat. The MPA's relative isolation from human 
impact could be allied to its geographical isolation and the absence  of a port, which limits the 
introduction of invasive species. However, challenges related to effective fisheries management, 
enforcement, and multi-stakeholder collaboration are evident. 

There  is  little  direct  evidence  that  the  Formigas  MPA  has  substantially  impacted  the  marine 
communities within it, and no quantitative evidence that spillover effects are occurring from this 
MPA. This ‘underperformance’ of the Formigas MPA (relative to other coastal MPAs) highlights the 
potential  need  to  further  develop  fisheries  management  procedures  within  this  MPA.  Deficient 
enforcement,  exacerbated  by  exceptions  for  pelagic  tuna  fishing  via  handline  or  pole-and-line 
methods exclusively by vessels integrated within the MONICAP system, despite the MPA's "no-
take"  status,  may  then  be  potentially  undermining  the  conservation  objectives  of  the  MPA. 
Despite such lack of quantitative evidence to show that the designation of the Formigas 
MPA is resulting in spillover, recent work has shown that MPAs within the Azores, can 
play a crucial role in preserving sensitive reef fish species) (Afonso et al., 2018).  Studies 
such as Afonso et al. (2011) and Afonso et al. (2018) provide valuable insights into the behaviour 
of marine species within MPAs, such as the dusky grouper in the Monte da Guia Marine Reserve, 
and the potential for spillover effects. These studies, while not directly focused on the Formigas 
MPA,  illustrate  the  importance  of  considering  the  ecological  dynamics  and  species-specific 
behaviours  in  understanding  and  managing  MPAs.  The  findings  suggest  that  while  MPAs  like 
Formigas can play a crucial role in protecting sensitive species, their design, management, and 
enforcement  need  to  be  carefully  evaluated  to  maximize  their  conservation  and  fisheries 
management benefits. 

In comparison to the lack of quantitative data on fish stocks within and around the MPA, 
stakeholder  perceptions  acknowledge  the  MPA’s  role  in  biodiversity  protection. 
However, such stakeholders also expressed concerns about the impacts of fishing restrictions on 
their  livelihoods.  The  resurgence  of  fisher  registrations  in  the  Azores  indicates  that  fisheries 
management has to consider evolving social and economic dynamics.  In addition, the response 
from the governmental authority stakeholder indicates a belief that the Formigas MPA contributes 
significantly to the recovery of overexploited fish stocks through spillover. Despite this, the diving 
stakeholder was more critical of the MPA's effectiveness, believing that it is no longer an effective 
conservation tool and points to the decline in marine resources observed over the past decade. 
The governmental authority is more positive about the MPA's effectiveness, believing that it has 
been successful in protecting marine resources and providing benefits to local fisheries. There is 
a  consensus  among  stakeholders  that  there  is  an  existing  need  for  stricter  enforcement  of 
regulations around the MPA. 

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The governmental stakeholder highlighted the dual role that the MPA has as a conservation tool 
and  fisheries  management  tool.  In  this  respect,  recent  work  (Afonso  et  al.,  2020)  has 
referenced  the  Formigas  MPA  as  one  of  the  locations  known  to  host  multiple  marine 
megafaunas,  and  the  authors  mentioned  that  places  like  the  Formigas  MPA  might 
prosper  under  better  protective  measures,  perhaps  through  updated  laws  and  MPA 
zoning. In a similar perspective, the stakeholder's idea to close off certain MPA zones aligns with 
the proposal to establish designated areas that might serve as refuges for fish stock and lead to 
increased spillover benefits and sustainable fishing methods. 

Collaborative  initiatives  between  stakeholders  are  acknowledged  by  the  respondents  from  the 
government and the fisheries sector as effective tools for understanding and managing spillover 
impacts. The stakeholder from the diving school is more concerned about the lack of collaboration 
between stakeholders, mentioning the lack of communication and cooperation among the different 
stakeholders involved in the management of the MPA. 

The  low  questionnaire  response  rate  in  this  study  introduces  a  potential  source  of  bias  in  the 
collected data and information since the perspectives were gathered from only three participating 
stakeholders,  and  may  not  accurately  represent  the  broader  range  of  perspectives  within  the 
stakeholder community. The timing of the survey, during the months of July and August, coincides 
with the typical holiday period in Portugal and this could potentially account for part of the reduced 
engagement among stakeholders who might have been unavailable due to vacation schedules. 
Moreover, the absence of responses could be attributed to the specific nature of the topic, as the 
Formigas  MPA's  spillover  effects  appear  to  have  very  limited  existing  research.  In 
addition, the responding governmental authority acknowledged, when asked in conversation, that 
researchers  and  governmental  authorities  lacked  knowledge  about  spillover  effects  in  the 
Formigas MPA and suggested that this could be the reason why many did not participate in the 
survey. 

7  CONCLUSIONS 

The study of the Formigas MPA in the Azores, through the review of the available literature and 
stakeholder  engagement,  showed  important  details  about  its  potential  spillover  effects.  It  is 
apparent that the  Formigas MPA  is a  region  of  ecological significance. The isolation,  due to its 
geographical and infrastructural limitations, has likely contributed to its relatively low exposure 
to  human  impacts,  enabling  it  to  maintain  its  distinctive  ecological  features.  Despite  these 
substantial ecological benefits, there is still little work that has examined the MPA and the long-
term effects of protection on the associated marine communities. In addition, studies like Afonso 
et al. (2011) and (2018) showcase the intricate relationship within this region between the MPA, 
the associated fish populations, and the adjacent fishing grounds.  

Despite this, the significance of spillover effects is acknowledged by the governmental authority 
stakeholder,  who  emphasizes  the  role  of  the  MPA  in  aiding  the  recovery  of  overexploited  fish 
populations. Quantitative data to support such claims are lacking. In fact, despite its "no-take" 
status, quantitative analyses of the Formigas MPA have shown that it may underperform (in terms 
of  enhancing  fish  populations)  in  comparison  to  coastal  MPAs,  due  to  potential  deficiencies  in 
enforcement and allowances for pelagic tuna fishing.  

While  the  governmental  authority  stakeholder  views  the  MPA  as  a  dual-purpose  tool  for  both 
conservation  and  fisheries  management,  the  diving school  representative holds  a  more  critical 
stance,  indicating  a  decline  in  marine  resources  over  the  past  decade  and  a  need  for  stricter 
enforcement and improved protective measures. All of the stakeholders are in consensus about 
the necessity for stronger enforcement of the MPA. The significance of collaborative projects and 
the MPA's dual role in both conservation and fisheries management was also recognized.  

Any future work would benefit from a higher participation rate among stakeholders to ensure a 
broader  representation  of  perspectives.  To  evaluate  the  effectiveness  of  the  Formigas  MPA, 
continuous monitoring and research are imperative given that existing studies on spillover effects 
within and around this MPA are currently limited to non-existent. Future research on the Formigas 
MPA should concentrate on quantitatively measuring spillover effects, utilizing statistical models 
to  track  biomass  and  diversity  changes  in  adjacent  areas.  This  focus  will  enable  a  precise 
evaluation of how protected zones influence surrounding ecosystems and fisheries, providing a 
clear  metric  for  conservation  efficacy  and  resource  management.  Such  targeted  studies  are 
essential for validating the MPA's role in promoting marine biodiversity and enhancing fish stocks 
beyond its boundaries. 

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Afonso,  P.,  Schmiing,  M.,  Fontes,  J.,  Tempera,  F.,  Morato,  T.,  &  S.  Santos,  R.  (2018).  Effects  of  marine 
protected  areas  on  coastal  fishes  across  the  Azores  archipelago,  mid-North  Atlantic.  Journal  of  Sea 
Research, 138, 34–47. https://doi.org/10.1016/j.seares.2018.04.003  

Christiansen,  S.,  Tempera,  F.  (n.d.).  The  Formigas  Bank—A  Potential  MPA.;  WWF  World  Wildlife  Fund: 

Washington, DC, USA. Online PDF, consulted in March 2024 

Decreto  Legislativo  Regional  11/88/A,  de  4  de  Abril  (1988).  Accessed  on  27/07/2023.  Available  at 

https://dre.tretas.org/dre/434/decreto-legislativo-regional-11-88-A-de-4-de-abril. (n.d.). 

Direção  Regional  dos  Assuntos  do  Mar.  (2022).  Reserva  Natural  dos  Ilhéus  das  Formigas.  Retrieved  from 

https://www.azores.gov.pt/Portal/pt/entidades/srrn-dram/. (n.d.). 

European 

(2021). 
https://ec.europa.eu/environment/nature/natura2000/index_en.htm. (n.d.).  

Commission. 

Natura 

2000. 

Retrieved 

from 

Governo dos Açores (2020). Relatório do 2.o Ciclo das Estratégias Marinhas PARTE B | ATIVIDADES, PRESSÕES 

E IMPACTES SUBDIVISÃO DOS AÇORES. 

Instituto Nacional de Estatística (2023). [Statistical database]. https://www.ine.pt/ 

Lopes I, Silva A, Jiménez S, Rodriguez JE, Jiménez Jaén A, Herrera RiveroI, Jorge V. (2019). Marine Protected 
Areas  in  Macaronesia.  Deliverable  D.3.3.,  under  the  WP3  of  MarSP:  Macaronesian  Maritime  Spatial 
Planning project (GA nº EASME/EMFF/2016/1.2.1.6/03SI2.763106). (n.d.). 

Santos, R. S., Hawkins, S., Monteiro, L. R., Alves, M., & Isidro, E. J. (1995). Marine research, resources and 
conservation  in  the  Azores.  Aquatic  Conservation:  Marine  and  Freshwater  Ecosystems,  5(4),  311–354. 
https://doi.org/10.1002/aqc.3270050406 

Tempera  F.  (2008).  Benthic  habitats  of  the  extended  Faial  island  shelf  and  their  relationship  to  geologic, 
oceanographic  and  infralittoral  biologic  features.  PhD  dissertation,  University  of  St.  Andrews.  Available 
from http:// research-repository.st-andrews.ac.uk/handle/10023/726 

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14. . CASE STUDY REPORT: 

SELVAGENS ISLANDS MARINE PROTECTED AREA 

PORTUGAL – MACARONESIA 

Port of Funchal with examples of small scale fishing vessels. © Nuno Castro 

Analysis of potential spillover effects around the 
Selvagens Islands Marine Protected Area 

Sérgio Abreu 

MRAG Europe 

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TABLE OF CONTENTS 

1 
2 
3 
4 

5 

6 
7 
8 

EXECUTIVE SUMMARY ......................................................................................... 219 
BACKGROUND .................................................................................................... 219 
AIMS AND OBJECTIVES ....................................................................................... 222 
METHODOLOGY .................................................................................................. 222 
4.1 
Literature review ....................................................................................... 222 
4.2  Stakeholder questionnaire .......................................................................... 222 
RESULTS ........................................................................................................... 223 
5.1 
Literature review ....................................................................................... 223 
5.2  Stakeholder perceptions ............................................................................. 225 
DISCUSSION ..................................................................................................... 226 
CONCLUSIONS ................................................................................................... 227 
REFERENCES ..................................................................................................... 228 

LIST OF ABBREVIATIONS 

Term 

Description 

EEZ  

IBA  

MPA 

Exclusive Economic Zone 

Important Bird and Biodiversity Area 

Marine Protected Area  

PCIML 

Permanent Commission of International Maritime Law 

POGIS  

Selvagens Islands' Management and Development Plan 

RNS 

SAC  

SPA  

Selvagens Natural Reserve 

Special Area of Conservation 

Special Protection Area 

UNCLOS 

United Nations Convention on the Law of the Sea 

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1  EXECUTIVE SUMMARY  

This case study focuses on the Selvagens Islands Marine Protected Area (MPA) which is located 
in the North Atlantic and forms  part of Madeira's Autonomous Region.  In 2021, the  Selvagens 
Islands MPA became Europe's largest MPA. This study examined whether spillover effects have 
been  detected  or  not  around  the  MPA  by  conducting  a  literature  review  and  stakeholder 
engagement. The engagement utilised a questionnаire-bаsed methodology, targeting commercial 
and  recreational  fishers,  fisheries  managers  and  government  authorities,  scientists  and 
environmental non-government organisations.  

The literature review underscores the Selvagens Islands MPA's critical role in marine biodiversity 
conservation. No evidence was found in the literature for spillover effects of the MPA, however 
with  the  richness  of  the  area  there  is  a  probability  that  spillover  takes  place.  The  stakeholder 
engagement showed that there is a marked divergence in stakeholders' opinions in terms of the 
impact of the Selvagens Islands MPA, notably between representatives from  the governmental 
authority  and  the  fisheries  sector.  The  governmental  authority  emphasized  the  benefits  of 
conservation, while concerns were raised by the fisheries sector regarding impacts on livelihoods 
due to fishing restrictions. This duality in opinion also resulted in a divergence in viewpoints on 
the likelihood of spillover effects, with the  governmental authority expecting positive outcomes 
and the fisheries sector expressing marked scepticism.  

This  divergence  in  opinions  underscores  the  need  for  comprehensive  discussions  on  MPA 
management optimization,  aiming  to  merge  conservation  initiatives  with  the  tangible needs  of 
local  fishers.  In  addition,  future  research  should  combine  a  qualitative  approach  with  a 
quantitative approach, to elucidate the multifaceted impacts of the MPA. A quantitative approach 
could  entail  fish  stock  surveys,  species  movement  tracking,  and  analysis  of  fisheries  data,  to 
quantitatively evaluate the spillover effects and socio-economic implications of the MPA.  

2  BACKGROUND 

The Selvagens Islands and their surrounding sea zones, are situated in the North Atlantic and are 
part  of  the  Autonomous  Region  of  Madeira.  They  represent  the  southernmost  boundary  of 
Portuguese land, situated between distinct latitudes and longitudes. These islands, which mark 
the  most  southern  extent  of  Portugal's  maritime  domain,  are  positioned  in  the  temperate-
subtropical northeast Atlantic. They are closer to Spain's Island Tenerife than to Madeira and are 
about 600 km from the Moroccan coast. 

The Natural Reserve of the Selvagens Islands, covering 9 471 hectares, is bounded by the 200-
metre isobath and includes Selvagem Grande Island, Selvagem Pequena Island, Fora Islet, and 
other smaller islets (Figure 1). In November 2021, its protected area expanded significantly from 
95 to 2 677 km2. 

Figure 1: Map of the Madeira Region and the Selvagens Islands (Source: Instituto das 
Florestas e Conservação da Natureza [IFCN], 2022). 

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The Selvagens Islands have witnessed a dynamic history of discovery, ownership changes, and 
conservation  efforts.  The  islands  were  officially  found  in  the  15th  century  by  the  Portuguese 
explorer Diogo Gomes. These lands became a source of income through plant collection for dyes 
and tannery uses. Ownership shifted in the 16th century among private individuals. In the 18th 
century,  the  "urzela"  trade  flourished,  providing  rich  colour  to  textiles.  The  sovereignty  of  the 
Selvagens Islands, settled by the Permanent Commission of International Maritime Law in 1938, 
remains a contentious issue between Portugal and Spain. Central to this dispute is whether the 
islands qualify as "islands" or "rocks" per the United Nations Convention on the Law of the Sea 
(UNCLOS) Article 121, impacting the southern boundary of the Portuguese Exclusive Economic 
Zone (EEZ). Spain asserts the islands should be designated as rocks, positioning them within the 
Spanish EEZ and granting Canary Islands' fisher access. Portugal points to permanent habitation 
and stationed research and ranger facilities, advocating for a 200-nautical-mile EEZ around the 
archipelago (Friedlander et al., 2016). At the start of the 20th century, the islands moved from 
private  to  regional  administration,  accompanied  by  the  establishment  of  lighthouses. 
Conservation took centre stage in the 21st century, with the islands becoming part of Natura 2000 
and hosting scientific missions (Instituto das Florestas e Conservação da Natureza [IFCN], n.d.). 

The Selvagens Islands were designated as a Strict Nature Reserve in 1971 by Decree No. 458/71, 
imposing  usage  restrictions  in  both  marine  and  terrestrial  zones  (Regional  Government  of 
Madeira,  1971).  They  were  later  reclassified  as  a  Natural  Reserve  under  Regional  Decree  No. 
15/78/M  (Regional  Government  of  Madeira,  1978),  which  still  stands  today,  albeit  with 
modifications  introduced  by  Regional  Decree  No.  11/81/M  (Regional  Government  of  Madeira, 
1981). The Selvagens Islands were initially intended to protect its native fauna, flora, and marine 
ecosystems. An essential trigger for this was the conservation of the vulnerable Cory’s shearwater 
colony (Calonectris spp). The Selvagens Islands are recognized as the world’s largest breeding 
ground  for  Cory’s  shearwaters  (Granadeiro  et  al.,  2006).  Recent  regulations  included  the 
establishment  of  the  Natural  Monument  of  the  volcanic  structures  in  the  islands  via  Regional 
Legislative  Decree  No.  7/2021/M  (Regional  Government  of  Madeira,  2021).  This  covers  the 
emerged sections of Selvagem Grande Island and Selvagem Pequena Island’s volcanic formations 
and their submarine pedestals, highlighting them as areas of scientific interest.  

In 2021, the Madeira regional government initiated a vast marine conservation project, framing 
the Selvagens Islands Nature Reserve as Europe’s largest MPA (Alves et al., 2022). This measure 
resulted  in  the  extension  of  the  protective  zone  to  2  677  km2,  ensuring  protection  against 
extractive  activities,  while  aiming  to  protect  diverse  habitats  and  species,  including  bottlenose 
dolphin (Tursiops truncatus) and blue shark (Prionace glauca) (Alves et al., 2022). An updated 
legal  framework  for  the  MPA  was  then  endorsed  by  Regional  Legislative  Decree  No.  8/2022/M 
(Regional Government of Madeira, 2022).  

In May 2022, the extension of the MPA highlighted its significance as a no-take zone, which has 
an IUCN 1A designation. Reflecting its ecological importance and the unique species and habitats 
it hosts, the Selvagens Island Nature Reserve is incorporated into the EU Natura 2000 Network, 
aligning  its  boundaries  with  the  Natural  Reserve.  This  MPA  encompasses  a  Special  Area  of 
Conservation (SAC, PTSEL0001) and an overlapping Special Protection Area (SPA, PTZPE0062) 
covering 124 530 hectares, as dictated by Regional Regulatory Decree No. 3/2014/M on March 3 
(Figure 2). 

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Figure  2:  Map  of  the  Selvagens  Islands  MPA  with  three  protection  areas:  Selvagens 
Natural  Reserve,  Natura  2000  Special  Conservation  Area  and  Natura  2000  Special 
Protection Area (Instituto das Florestas e Conservação da Natureza, n.d.) 

The management of the Selvagens Islands MPA, including its Natura 2000 sites, falls under the 
Selvagens  Islands’  Management  and  Development  Plan  (POGIS).  Initially  approved  by  the 
Regional  Government  Council  Resolution  No.  1292/2009  on  October  2,  it  was  revised  in  2017 
through Resolution No. 303/2017 on May 15 to address contemporary trends in various sectors 
(Presidência  do  Governo  Regional,  2009)  (Instituto  das  Florestas  e  Conservação  da  Natureza, 
n.d.).  Notably, the updated plan  addresses the  creation and regulation of nature and scientific 
tourism  on  the  islands.  The  MPA  Management  Plan  covers  terrestrial  and  marine  regions  of 
significant natural value and areas of socioeconomic activity, resulting in varying protection levels 
and usage permissions.  

Following  the  enactment  of  Decree-Law  No.  8/2022/M  on  May  3,  2022,  the  Selvagens  Islands 
Natural  Reserve  has  been  consolidated  under  a  new  legal  framework,  thereby  superseding 
previous zoning  distinctions, such  as the Total Protection Area and the Partial  Protection  Area. 
The  decree  establishes  the  Selvagens  Islands  Natural  Reserve  as  a  singular  zone  of  integral 
protection, encompassing all terrestrial and marine areas up to a depth of 200 meters around the 
Selvagem Grande, Selvagem Pequena, Fora Islet, and adjacent islets. This zone is now subject to 
comprehensive  conservation  measures,  with  human  activities  strictly  limited  to  research, 
monitoring, and conservation efforts. Notably, the decree has introduced a total ban on fishing 
within  the  entire  Marine  Reserve  area  of  the  Selvagens  Islands,  reflecting  a  significant  shift 
towards stronger environmental protection. The management of the reserve and its adherence to 
conservation goals are under the purview of the Regional Secretariat for Environment and Natural 
Resources,  in  collaboration  with  relevant  authorities,  to  ensure  the  preservation  of  its  unique 
ecological  value.  Activities  within  the  reserve  are  meticulously  regulated,  with  a  focus  on 
promoting  scientific  research,  environmental  education,  and  sustainable  nature-based tourism, 
thereby aligning with global conservation objectives and the safeguarding of marine biodiversity 
(Regional Government of Madeira, 2022).  

Currently, the Madeira Natural Park Service supervises the management and surveillance of the 
islands (Friedlander et al., 2016; UNESCO, 2019). Two full-time rangers and two maritime police 
officers  are  stationed  year-round  on  Selvagem  Grande.  Selvagem  Pequena  typically  hosts  two 
rangers from May to October, marking them as the islands’ sole inhabitants (Friedlander et al., 

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2016). However, as indicated by Friedlander et al. (2017), insufficient protection in the deeper 
waters exposes species to risks arising from intensive fishing activities. 

There is a need to better understand the role of MPAs in fostering biodiversity conservation and 
socio-economic growth through  spillover effects. By  focusing  this case study  on the Selvagens 
Islands  MPA,  we  aim  to  assess  how  MPAs  may  enhance  ecological  connectivity  and  boost  fish 
stocks  beyond  their  boundaries,  offering  sustainable  benefits  for  fisheries  management  and 
surrounding communities. The combination of a literature review and a stakeholder engagement 
survey  provides  a  nuanced  perspective  on  spillover  effects  and  their  wider  implications.  This 
research  goes  beyond  academic  inquiry,  aiming  to  inform  strategic  management  and  policy 
decisions for the long-term sustainability of marine resources. By bridging theory with practice, 
the  study  seeks  to  contribute  to  future  conservation  strategies  and  enhance  stakeholder 
involvement in MPA governance, thus adding valuable insights to the global marine conservation 
dialogue and offering evidence-based strategies to maximize MPAs' ecological and socio-economic 
advantages. 

3  AIMS AND OBJECTIVES 

The main aim of this case study is to investigate whether spillover effects have been detected 
around the Selvagens Islands MPA. To achieve this, a multifaceted approach has been devised. 
Firstly, we aimed to determine the presence or absence of spillover effects within the Selvagens 
Islands MPA through a comprehensive review of existing literature. Subsequently, we identified 
and compiled evidence from the literature that substantiates the occurrence of spillover effects, 
if  any,  within  and  around  the  Selvagens  Islands  MPA.  Additionally,  we  sought  to  gather  and 
analyse the perceptions, opinions, and experiences of key stakeholders, including fishers, fisheries 
managers,  scientists,  and  environmental  organizations,  regarding  spillover  effects  in  the 
Selvagens Islands MPA through a questionnaire-based approach. More specifically, we assessed 
the level of stakeholders’ knowledge concerning the regulations governing the Selvagens Islands 
MPA,  with  a  particular  emphasis  on  fishing  restrictions.  We  also  evaluated  how  stakeholders 
perceive the role of the Selvagens Islands MPA, specifically as a conservation tool and a fisheries 
management  instrument.  Finally,  we  identified  and  explored  the  key  factors  that  stakeholders 
associate with the occurrence or absence of spillover effects in the Selvagens Islands MPA.  

4  METHODOLOGY 

4.1  Literature review 

The literature review in this study was conducted using a thorough approach to provide an in-
depth  look  at  the  potential  spillover  effects  associated  with  the  Selvagens  Islands  MPA.  The 
research methodology included searching in databases like ScienceDirect, SpringerLink and also 
Google Scholar using specific keywords. Additionally, academic journals as well as grey literature, 
websites  and  recommendations  from  key  researchers  were  considered  to  identify  relevant 
publications related to the Selvagens Islands MPA. After an initial scan of titles and abstracts, the 
literature  was  narrowed  down  to  studies  focusing  directly  on  the  Selvagens  Islands  MPA  and 
covering the key themes of spillover effects, fisheries and stakeholders.  

4.2  Stakeholder questionnaire  

We  developed  a  detailed  questionnaire  to  assess  the  perceptions  of  key  stakeholders  on  the 
potential  spillover  effects  from  the  MPA  to  adjacent  areas.  The  questionnaire  comprised  open-
ended  and  closed  questions.  Open-ended  questions  were  developed  to  capture  stakeholder 
opinions, while closed questions were statement-based and used Likert scale answer categories. 
Questions were grouped into four broad categories to encapsulate the key issues being studied 
(see Annex 4):  

•  Respondent  information:  Basic  information  on  the  name,  institution  and  role  of  the 

respondent requested. 

•  Background information: Background information requested to understand the respondent 
and  their  (potential)  use  of  the  MPA.  Questions  included  knowledge  of  when  the  MPA  was 
established, the type of restrictions in place and how long the stakeholder has been associated 
with the MPA either through research, fishing or managing it. 

•  Fishery  impacts  of  MPAs:  Respondent’s  perceptions  of  the  socio-economic  impacts  of 
spillover from the MPA were requested. Stakeholders were asked whether the designation of 
an MPA / area where fishing is limited has led to an increase in revenues for fishers, whether 

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the fishing community in  the area  feel  their fisheries livelihoods are  more secure after the 
MPA  was  established,  and  the  extent  to  which  they  believe  spillover  from  the  MPA  has 
influenced the catch composition in adjacent fishing grounds. 

•  MPAs  as  management  tools:  The  respondent’s  perceptions  on  whether  MPAs  are 
conservation or fisheries management tools was requested. Stakeholders were asked to state 
whether their local MPA was acting as a conservation tool, a fisheries management tool or 
both.  Other  questions  under 
their 
agreement/disagreement on whether the establishment of MPAs is an effective conservation 
strategy to support fish populations and commercial fisheries in their area. Respondents were 
also asked to indicate what factors they thought were contributing to spillover effects. 

this  section  required  stakeholders 

to  state 

Four key stakeholder groups were targeted: (i) commercial and recreational fishers; (ii) fisheries 
managers and government authorities; (iii) scientists; and (iv) environmental non-government 
organisations (eNGOs).  We  engaged  with several  stakeholders  linked  to the  Selvagens Islands 
MPA: 23 stakeholders were contacted through email and 13 of them received follow-up emails as 
an incentive to participate. Several phone calls were also made to promote engagement from the 
stakeholders  of  the  different  groups.  Breaking  it  down  by  category:  we  approached  two 
representatives from Fishermen’s Associations, 12 from governmental entities, four researchers 
from various institutes, and five individuals from NGOs.   

5  RESULTS 

5.1  Literature review 

While a considerable amount of research within the Selvagens Islands MPA has focused on the 
conservation  of  marine  bird  species,  investigations  into  marine  (intertidal  and  subtidal) 
communities are also present, albeit to a lesser extent. This conservation priority is evident in the 
establishment  of  the  MPA,  which  was  originally  intended  to  maintain  the  islands’  ecosystems, 
protect natural habitats, and counterbalance the impacts of unchecked human activities.  In this 
context, a range of institutions and organizations have conducted research on the islands’ ecology 
and wildlife, ranging from ornithological studies to geological research and ecosystem monitoring 
(Instituto  das  Florestas  e  Conservação  da  Natureza,  n.d.).  The  Selvagens  Islands’  marine 
environment remains relatively unexamined, which has been attributed to its remote location and 
challenging sea conditions (Friedlander et al., 2017).  

Despite the lack of research on marine species, the Selvagens Islands MPA comprises a variety of 
endemic, threatened, and vulnerable marine fish species, while also showcasing pristine habitats 
and  globally  rare  marine  species  (Friedlander  et  al.,  2017).  Furthermore,  these  islands  act  as 
stepping stones for species colonization (Almada et al., 2015). Notably, the Selvagens Islands are 
home to a vast array of fish species, some of which hold commercial importance (Almada et al., 
2015; Friedlander et al., 2017). Comprehensive studies by the M@rbis Project and the National 
Geographic Society have identified a rich ecosystem (UNESCO World Heritage Centre, n.d.). For 
example, the Selvagens 94 Expedition identified 115 marine molluscs, with 32 being new records 
for  the  islands.  Additionally,  the  EMEPC/M@rBis/Selvagens  2010  mission  discovered  29  new 
coastal fish species.  

Recent research, although not focused on spillover effects of the Selvagens Islands MPA, was able 
to show the high abundance and diversity of fishes within the MPA (Friedlander et al., 2017). This 
work  showed  that  total  fish  biomass  was  3.2  times  larger  at  Selvagens  than  within  Madeira 
mainland, with the biomass of top predators more than 10 times larger at Selvagens Islands MPA. 
In addition, this study showed that there are a range of  commercially important species (e.g., 
groupers, jacks), known to be overfished throughout the region, that were relatively common and 
of larger size at Selvagens Islands MPA than found within mainland Madeira. Lastly, this work also 
showed that a range of sea urchin predators (e.g., hogfishes, triggerfishes) were also in higher 
abundance at Selvagens Islands MPA compared to Madeira (Friedlander et al., 2017).  

The waters surrounding the  Selvagens Islands MPA also comprise a range of large and diverse 
marine fauna. Cetaceans, including minke whales, sperm whales, bottlenose dolphins, and pilot 
whales,  some  of  which  are  listed  as  “Vulnerable”  or  “Endangered”,  have  been  identified.  In 
addition,  the  nearshore  marine  ecosystem  of  the  Selvagens  Islands  MPA  holds  a  diverse  algal 
collection of at least 47 taxa, while the limited presence of sea urchin barrens, covering just 8% 
of the seabed, attests to the region’s health. While large molluscs like the spiny pen shell, top-
shell snail, and African thorny oyster are prevalent in Selvagens Islands, they are under threat 
elsewhere  in  Macaronesia due to overfishing,  habitat  degradation,  and  pollution.  The intertidal 

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ecosystems around these islands remain largely untouched, with the sun limpet, nearly extinct in 
other parts of Macaronesia, thriving in abundance at Selvagens Islands (Friedlander et al., 2017). 

Geologically, Madeira's narrow platforms, sharp slopes, and low-productivity oligotrophic waters, 
restrict the habitats for demersal species and the range of viable fishing methods (Delgado, 2007). 
As  a  result,  Madeira's  fisheries  have  been  focused  on  a  limited  number  of  species,  largely 
encompassing deep-water, large pelagic migratory, and small pelagic fishes. Fisheries landings in 
Madeira have shown high variability (Santos, 2010). The period from 1990 to 1998, peaking in 
1995, is recognized as the golden era. Although 2019 was an exceptional year in recent times, 
2020 saw a downturn with a slight recovery (6.7 %) in 2021 (Figure 4. ).  

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Figure 4. Economic Value of Fish Landings in Madeira from 2000 to 2022 (in Thousands 
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Tuna and black scabbardfish have predominantly dominated catches (Figure 5). Fish species like 
mackerel  and  horse  mackerel,  enjoyed  popularity  until  the  late  '90s,  before  facing  substantial 
drops.  The  catch  numbers  for  tuna  experienced  a  revival  between  2017  to  2019,  while  black 
scabbardfish numbers dwindled in 2021 (Figure ).  

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Figure 5. Annual landings by weight (t) for the four main target species in the Madeira 
Region: Tuna, mackerel, horse mackerel and black scabbard fish (Instituto Nacional de 
Estatística, 2023) 

There has been a decrease in both fishing vessels and licenses from the mid-2000s, with licensed 
vessels  declining  from  145  in  2006 to  96  in  2021.  Yet,  the  number  of  licenses  issued  in 2021 
slightly  surpassed  the  figures  from  2010  (Instituto  das  Florestas  e  Conservação  da  Natureza, 
n.d.). 

5.2  Stakeholder perceptions 

There was little engagement with the majority of stakeholders identified and contacted. In this 
respect, despite numerous attempts at engagement, only two key stakeholders, representing the 
governmental  authority  and  the  fisheries  sector,  participated  in  the  study.  Twenty-one 
stakeholders  did  not  provide  any  response.  Of  these,  three  of  the  contacted  stakeholders 
mentioned  holidays  as  the  reason  they  were  unavailable,  with  some  hinting  at  possible 
participation  in  the  future.  Four  stakeholders,  understanding  the  intent  of  the  study,  advised 
contacting  other  individuals  for  more  appropriate  insights  and  chose  not  to  participate.  Three 
stakeholders visited the online questionnaire website but opted not to complete the questionnaire.  

The two stakeholders who filled out the questionnaire exhibited a degree of scepticism regarding 
the immediate positive outcomes of the Selvagens Islands MPA on fisheries. The governmental 
authority  stakeholder  implied  that  the  relatively  recent  implementation  of  the  no-take  MPA 
(2022), led to limited data on changes in fish abundance and species composition. Similarly, the 
fisheries sector stakeholder indicated that the establishment of the MPA has resulted in reduced 
catches and restricted fishing zones. Furthermore, this stakeholder also emphasized the economic 
challenges faced by local fishers due to restricted fishing zones within the MPA, shedding light on 
the practical complexities of implementing conservation measures. The fishers pointed out, "We 
fish less and are more limited" indicating the constraints imposed by the MPA. Similarly, the same 
stakeholder notes, "The captures, essentially of small tuna species, ceased to exist" showcasing 
the immediate impact on fishing activities within the MPA.  

Notably, opinions diverged when considering the likelihood of spillover effects. The governmental 
authority stakeholder rates the likelihood as "Agree" for spillover from fully protected areas, while 
the  fisheries  sector  stakeholder  rates  it  as  "Strongly  Disagree".  The  governmental  authority 
stakeholder expresses optimism, believing that the MPA will enrich biodiversity within and beyond 
the MPA. This stakeholder stated that "the MPA works primarily as a conservation tool… it must 
also be a fisheries management tool", emphasizing the potential dual role of the MPA. However, 
the  fisher's  perspective  is  more  sceptical,  expressing  "The  type  of  fishing  practised  here  is 

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sustainable, catching fish one by one… it is not a conservation tool." The fishers appear to suggest 
with this comment that the  pole and line fishery targeting tuna, which was allowed before the 
creation of the recent no-take area, has a very low bycatch and high species selectivity, which is 
corroborated by several authors.  

Different  opinions  were  also  observed  regarding  the  collaborative  initiatives  between  research 
groups,  fishing  communities,  and  management  authorities.  The  governmental  authority 
stakeholder  considers  such  collaborations  moderately  successful,  stating,  "The  importance  and 
advantages  of  reserves  should  be  communicated…  involving  fishing  communities  should  be 
prioritized." Nonetheless, the fishers’ representative is less convinced, mentioning, "The MPA does 
not bring any benefit" and highlighting the fishers’ opposition to the MPA. 

6  DISCUSSION 

The  Selvagens  Islands  MPA  in  the  North  Atlantic  is  of  considerable  historical,  ecological,  and 
geopolitical  significance  within  the  context  of  the  Madeira  Region.  Nevertheless,  the  islands’ 
remoteness and rough surrounding sea conditions have likely caused limitations to the extent of 
research activities being undertaken within the surrounding waters.  

Friedlander’s research underscores the Selvagens Islands MPA's ecological significance, revealing 
marked disparities in fish biomass and the abundance of commercially critical species compared 
to  the  Madeira  mainland.  Notably,  the  total  fish  biomass  within  the  MPA  is  approximately  3.2 
times that of the mainland,  with  top predator biomass exceeding tenfold. Additionally, species 
like groupers and jacks, often overfished regionally, were observed to be both common and larger 
in size within the MPA (Friedlander et al., 2017). These findings highlight the MPA's crucial 
role  in  sustaining  vital  marine  species,  supporting  both  biodiversity  and  potential 
spillover effects that could replenish fish stocks in neighbouring fishing areas. The presence of 
a  healthy,  diverse  marine  environment  within  the  MPA  indicates  a  strong  potential  for  such 
spillover,  emphasizing  the  need  for  future  research  to  monitor  and  quantify  these  effects. 
Understanding the movement of species and the socio-economic impact on local communities will 
be critical in assessing the MPA's broader ecological and economic contributions. 

In this work, we explored also the perceptions of the stakeholders involved with the  Selvagens 
Islands  MPA  as  well  as  the  available  ecological  and  fisheries  literature  focused  on the  MPA.  In 
terms of the ecological implication of the MPA, a consistent theme from both the literature 
and  stakeholder  responses  is  the  preservation  of  biodiversity  and  the  potential  for 
ecological change both inside and outside the Selvagens Islands MPA (despite no data 
being  available  to  test  such  changes).  In  this  respect,  the  governmental  authority 
stakeholders  stated  the  belief  that  the  MPA  had  the  potential  to  enhance  local  and  regional 
biodiversity. Importantly, they also stated that such biodiversity could be further enhanced with 
better  MPA  enforcement.  Despite  this,  the  implementation  of  the  Selvagens  Islands  MPA  has 
resulted in shifts in fishing patterns. This shift was criticised by the fisheries sector stakeholder, 
who focused on the reduction of available fishing areas and the negative effects on community 
livelihoods.  

Notwithstanding the reported decline in catches, MPAs such as the one in Selvagens Islands 
may  be  pivotal  for  preserving  marine  biodiversity.  Findings  from  M@rbis,  the  National 
Geographic Society and limited ecological research show that the Selvagens Islands MPA may 
be  important  in  preserving  regionally  threatened  species  and  biodiverse  marine 
ecosystems.  This  is  despite  the  lack  of  data  on  how  the  MPA  has  impacted  the  surrounding 
marine  communities  (aside  from  shielding  them  from  fishing  effects);  it  can  be  inferred  from 
stakeholder feedback and existing research that MPAs may face a reduced range of anthropogenic 
threats, such as overfishing and pollution, showcasing their implied ecological importance.  

Despite no quantitative data available, the limited stakeholder engagement  indicated 
that at least one stakeholder group (government) believes that MPA designation may 
lead to ecological and fishery spillover. Despite this, stakeholder opinions diverge: while the 
governmental authority stakeholder expects a positive spillover effect, the fishers’ representative 
strongly disagrees, suggesting the need for more context-specific research. 

This study had limitations. The viewpoints shared by these two stakeholders offer just a fraction 
of  the  diverse  perspectives  needed  to  comprehensively  grasp  the  intricacies  of  the  Selvagens 
Islands MPA. Both previous studies and our qualitative work agree that more targeted research 

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is needed to better understand the so-called "spillover effects" in the Selvagens Islands 
MPA.  

7  CONCLUSIONS 

This  study  aimed  to  exрlore  the  рersрeсtives  of  stаkeholders  and  the  available  literature  on 
sрillover effeсts within and around the Selvagens Islands MPA. Importantly there is no research 
(either qualitative or quantitative) that has examined ecological or fishery spillover related to the 
Selvagens  Islands  MPA.  Research  has  been  primarily  focused  on  surveying  and  assessing  the 
abundance and diversity of marine communities between the Selvagens Islands MPA and MPAs 
within mainland Madeira. Therefore, the perspectives obtained from the stakeholders regarding 
the Selvagens Islands MPA, although limited, were useful in understanding the impact of the MPA 
on marine communities.  

Interestingly,  the  perspectives  varied  significantly  between  stakeholders  highlighting  the 
complexities  and  challenges  associated  with  managing  the  MPA  (as  well  as  the  very  limited 
stakeholder  engagement).  The  single  government  official  who  responded  to  the  questionnaire 
sees the MPA as a tool for conservation that could also benefit fishing through spillover effects. 
The single fisher that responded to the questionnaire, on the other hand, thought the MPA was a 
restriction  to  their  work.  In  this  respect,  the  MPA  no-take  policy  has  resulted  in  economic 
difficulties  for  the  fishing  community  in  the  Madeira  region,  leading  to  scepticism  about  its 
immediate positive impact. In addition, the fisheries sector stakeholder’s concerns regarding the 
immediate economic challenges posed by the MPAs no-take policy reflect the tangible impact of 
such  measures  on  local  fishing  communities,  a  point  supported  by  historical  data  indicating 
fluctuations in landed catch over the years. The fact that the opinions between government bodies 
and fishers  diverged considerably emphasizes the need  for comprehensive discussions on MPA 
management  optimization.  Such  discussions  should  aim  to  harmoniously  merge  conservation 
initiatives with the tangible needs of local fishers.  

Future research must adopt a comprehensive approach, integrating both qualitative insights and 
rigorous quantitative analyses, to  elucidate the multifaceted impacts of the MPA.  Although the 
qualitative data collected from a limited number of stakeholders has provided initial insights, it is 
imperative  to  expand  our  investigation  through  systematic  quantitative  methodologies.  This 
includes  conducting  detailed  ecological  and  socio-economic  assessments,  such  as  fish  stock 
surveys, species movement tracking, and analysis of fisheries data, to quantitatively evaluate the 
spillover effects and socio-economic implications of the MPA.  

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8  REFERENCES 

Almada, F., Abecasis, D., Villegas-Ríos, D., Henriques, 228iomPais, M. P., Batista, M., Costa, B. H. E., Martins, 
J., Tojeira, I., Rodrigues, N. V., Araújo, R., Souto, M., Alonso, H., Falcón, J. M., Henriques, F., Catry, P., 
Cabral, H., Biscoito, M., & Almada, V. C. (2015). Ichthyofauna of the Selvagens Islands. Do small coastal 
areas  show  high  species richness  in  the  northeastern  Atlantic? Marine  Biology  Research,  11(1),  49–61. 
https://doi.org/10.1080/17451000.2014.889306 

Alves, F., Monteiro, J. G., Oliveira, P., & Canning-Clode, J. (2022). Portugal leads with Europe’s largest marine 

reserve. Nature, 601(7893), 318–318. https://doi.org/10.1038/d41586-022-00093-8 

Delgado,J. (2007) Ictiofauna demersal das zonas sublitoral e batial superior do arquipélago da Madeira. Um 

estudo biológico e ecológico (M.Sc. Thesis), University of Madeira, Portugal.. 

DREM Direcao Regional de Estatistica da Madeira (2022). Estatisticas da Agricultura e Pesca. Retrieved July 
20, 2023 from https://estatistica.madeira.gov.pt/download-now/ambiente-territorio/mar-territorio/em-
foco-mar/send/696-mar-em-foco/15398-em-foco-estatisticas-do-mar-2021.html.  

Friedlander,  A.  M.,  Ballesteros,  E.,  Clemente,  S.,  Gonçalves,  E.  J.,  Estep,  A.,  Rose,  P.,  &  Sala,  E.  (2017). 
Contrasts  in  the  marine  ecosystem  of  two  Macaronesian  islands:  A  comparison  between  the  remote 
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e0187935. 
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https://doi.org/10.1371/journal.pone.0187935 

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Geographic Pristine Seas, pp. 1–64). 

Granadeiro,  J.  228iomDias,  M.  P.,  Rebelo,  R.,  Santos,  C.  D.,  &  Catry,  P.  (2006).  Numbers  and  Population 
Trends of Cory’s Shearwater Calonectris Diomedea at Selvagem Grande, Northeast Atlantic. Waterbirds, 
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Instituto Nacional de Estatística. (2023). [Statistical database]. https://www.ine.pt/ 

Instituto das Florestas e Conservação da Natureza. (n.d.). Programas de conservação, estudos e projetos nas 
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Instituto  das  Florestas  e  Conservação  da  Natureza  (IFCN).  (n.d.).  Historial  das  Ilhas  Selvagens.  Retrieved 

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of  Madeira. 

(1971). 

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Regional  Government  of  Madeira.  (1978).  *Decreto  Regional  No.  15/78/M*.  Retrieved 
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Regional  Government  of  Madeira.  (1981).  *Decreto  Regional  No.  11/81/M*.  Retrieved 
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Regional  Government  of  Madeira.  (2021).  *Decreto  Legislativo  Regional  No.  7/2021/M  sobre  a  Rede  de 
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Naturais*. 

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Regional  Government  of  Madeira.  (2022).  *Decreto  Legislativo  Regional  No.  8/2022/M*.  Retrieved  from 

https://ifcn.madeira.gov.pt/images/Doc_Artigos/IlhasSelvagens/DLR_8_2022_M.pdf  

Santos  F.  (2010).  A  pesca  na  Historia  da  Madeira:  Estado  dos  conhecimentos  e  problematicas  futuras  de 

analise. Anuario 2010, Centro de Estudos de Historia do Atlantico, 354-397. (n.d.). 

UNESCO  (2019)  World  Heritage  Centre.  Selvagens  Islands—Tentative  List.  Retrieved  from  946  URL: 

https://whc.unesco.org/en/tentativelists/6217. (n.d.). 

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15. . CASE STUDY REPORT: 

LA GRACIOSA MARINE PROTECTED AREA  

SPAIN – MACARONESIA 

La Graciosa Island © PixaBay 

Analysis of potential spillover effects around the 
Marine Reserve of Graciosa Island and the 
Northern Islets of Lanzarote 

Rupert Stacy 

MRAG Europe 

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TABLE OF CONTENTS 

5 

1 
2 
3 
4 

EXECUTIVE SUMMARY ......................................................................................... 231 
BACKGROUND .................................................................................................... 231 
AIMS AND OBJECTIVES ....................................................................................... 235 
METHODOLOGY .................................................................................................. 236 
4.1 
Literature review and data collection ............................................................ 236 
4.2  Quantitative assessment of focal studies ...................................................... 237 
4.3  Stakeholder survey .................................................................................... 238 
RESULTS ........................................................................................................... 239 
Literature review and quantitative assessment of spillover effects ................... 239 
5.1 
Quantitative assessment of abundance data presented in Salz (2015) .............. 239 
Quantitative assessment of abundance and biomass data, Brito et al (2006) .... 241 
Population abundance indicator ................................................................... 244 
Population biomass indicator ....................................................................... 245 
5.2  Stakeholder perceptions ............................................................................. 245 
DISCUSSION ..................................................................................................... 246 
6.1  Quantitative assessment ............................................................................ 246 
6.2  Stakeholder perceptions ............................................................................. 247 
6.3  Summary ................................................................................................. 247 
CONCLUSIONS ................................................................................................... 247 
7 
REFERENCES ..................................................................................................... 248 
8 
SUPPLEMENTARY INFORMATION .................................................................................. 250 

6 

LIST OF ABBREVIATIONS 

Term 

BACI 

CPUE 

IEO 

Description 

Before-after control-impact 

Catch per unit effort 

Spanish Institute of Oceanography 

IUCN 

The International Union for Conservation of Nature 

MPA 

NGO 

UVC 

Marine protected area 

Non-Governmental Organisation 

Underwater visual census 

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1  EXECUTIVE SUMMARY  

The "Marine Reserve of Graciosa Island and the Northern Islets of Lanzarote" hereafter called La 
Graciosa Marine Protected Area (MPA), is a 707 km2, category VI MPA, featuring a 12 km2 fully 
protected  area.  With  no  commercial  fleet  active  in  the  MPA  since  its  establishment  in  1995, 
artisanal  and  recreational  fishing  activity  occurs  within  regulated  zones  outside  of  the  fully 
protected area.  

This  case  study  utilised  two  research  initiatives  to  obtain  quantitative  data  on  abundance  and 
biomass of six fish species however only one was used as a major focus paper, due to providing 
more  comprehensive  data  (Brito  et  al.,  2006).  Metrics  of  abundance,  and  to  a  lesser  extent 
biomass, were collated from  the latter study utilising underwater visual census surveys carried 
out before (1994) and after (2005) the establishment of the  MPA. Sampling sites were located 
within the MPA, including the fully protected (integral) area, and outside of it, ranging 12-50 km. 
Data were assessed against a Before After Control Impact (BACI) design to determine whether 
data aligns with indicators of spillover effects. In total, six species were assessed using abundance 
data, while two of those six, also were assessed using biomass data.  

Results suggest spillover indicators for three of the six species assessed after a 10-year period of 
protection. Two species identified as indicator species that are also targeted (Sparisoma cretense 
and Serranus atricauda) both indicate many potential spillover effects across reference sampling 
sites for both abundance and biomass, and in some cases are in agreement with each other (7 
out of 13 comparisons). S cretense had more spillover effect indications within the MPA (<21km) 
than S. atricauda, which showed more spillover indications at sites outside of the MPA. Of the four 
non-indicator  species  assessed  for  abundance  only,  one  indicated  a  potential  spillover  effect 
(Mycteroperca fusca) at two sites, both within the MPA (12 – 20 km). Neither of the two bycatch 
species studied were found to show indications of spillover effects. Furthermore, while S. cretense 
increased in abundance by 250%, its biomass increased only 2%, possibly alluding to ecological 
effects outside the scope of this case study. 

The implications of these results suggest that when studied from the perspective of quantitative 
biomass  and  abundance  data,  spillover  effects  between  species  appear  nuanced.  Even  species 
with similar life histories, and that are both targeted, show variation in response to protection. 
While  some  species  seem  to  exhibit  spillover  effects,  others  do  not,  indicating  varied  species 
response to the level of protection afforded within the MPA. Reference sites within the MPA, within 
<20km of the fully protected area, had more indicators of potential spillover than outside it. These 
results may point to the greatest benefits being found close to the fully protected area, inside the 
MPA.  This  may  be  due  to  the  overall  large  size  of  the  MPA.  Other  explanations  of  the  varied 
response could be the low level of fishing that occurred there in the years following establishment 
or the limited temporal sampling that was available (n=2 years). Unfortunately, no sampling was 
found from the partially protected buffer zone, which is missed opportunity to compare between, 
especially given their proximity.  

Based  on  these  findings,  further  examination  of  additional  species  is  recommended,  ideally 
incorporating  biomass  values  relative  to  those  where  abundance  values  are  already  available. 
Furthermore, updated biomass and abundance estimates are now well overdue, and would not 
only add deeper level of understanding to the results presented by Brito et al., (2005), but would 
shed  light  on  the  contemporary  status  of  the  MPA.  The  author  also  notes  that  in  light  of  the 
variation  in  increases  of  abundance  to  biomass  of  S.  cretense,  that  fishery  spillover  be 
investigated further (i.e. the proportion of this biomass that can be fished, taking into account 
regulations and accessibility). 

2  BACKGROUND 

Situated in the Azores, Canaries and Madeira ecoregion and found north of Lanzarote in the north-
east  of  the  Canary  Islands,  the  Chinijo  Archipelago  hosts  the  marine  protected  area  (MPA) 
“Reserva Marina de la Isla Graciosa y de los Islotes del Norte de Lanzarote”, hereafter called “La 
Graciosa”.  Established  by  local  and  national  authorities  in  a  somewhat  top-down  approach 
(Chuenpagdee  et  al.,  2013),  La  Graciosa  was  implemented  in  1995  and  contributes  to  Spain’s 
national network of marine reserves, of which it is the largest (Goni et al. 2023).  

La Graciosa marine reserve, is a category VI MPA in  accordance  with the IUCN Protected area 
categories (Rodríguez-Rodríguez et al. 2019), the primary objective of which is “to protect natural 
ecosystems and use natural resources sustainably, when conservation and sustainable use can 

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be mutually beneficial” (Day et al. 2012). As well as being part of a national network of MPAs, the 
site  is  in  part  covered  by  the  Natura  2000  sites  “Islotes  del  norte  de  Lanzarote  y  Famara”, 
designated  in  1989  and  “Espacio  marino  del  oriente  y  sur  de  Lanzarote-Fuerteventura”, 
designated in 2015, protected under the Birds Directive and Habitats Directive, respectively. 

La Graciosa MPA is 70,764ha and covers a range of habitats including rocky shores, caves, maerl, 
seagrass beds, sandy substrates and open ocean environments that extend down to 1000m (Goni 
et al. 2023; Vandeperre et al, 2006). The MPA contains areas that are both fully protected and 
partially protected. There are further delineation of internal and external waters (Figure 1). These 
delineations  represent  shared  management  of  the  MPA  as  a  whole,  with  the  General  State 
Administration  (Spanish  State)  managing  the  external  waters  (60%)  and  the  internal  water 
managed locally by the Autonomous Community of the Canary Islands (40%) (Vandeperre et al, 
2006).  

The fully protected area (or integral reserve) is 1,225ha in size, represents less than 2% of the 
overall size, and is established within an area of circle that extends 1 mile from the centre on the 
island Roque del Este in the east of the Chinijo archipelago. The fully protected area restricts all 
activities, with any  type of maritime  fishing or extraction of marine living resources  prohibited 
and  access  to  the  integral  zone  is  authorised  by  the  General  Secretariat  of  Maritime  Fisheries 
(BOE, 1995). The buffer zone, which extends 2 mile from the outer perimeter of the fully protected 
integral reserve area, is around 8,480ha and proportionately is 12% of the total marine reserve 
area. The buffer zone forbids recreational fishing but allows professional fishing with hook and 
line tackle, as well as traditional gears targeting Sarpa salpa and migratory species. The rest of 
the marine reserve, in both internal and external waters, regulates fishing activity by permitting 
only hook and line fishing, aimed at targeting Sarpa salpa and migratory species (Planes et al. 
2008).  

The MPA is zoned, with fisheries activity restricted across the whole reserve. The fully protected 
area (integral reserve) sits within a one mile circle radius of Roque del Este. The legal text that 
defines the restriction  of  fisheries activities is worded  in a way that prohibits the  extraction  of 
marine flora and fauna, with certain exceptions (BOE, 1995). These are: 

• 

• 

• 

The activity of professional sea fishing with hook tackle, and also with gears that have been 
traditionally used in the area for the capture of Salemas (Sarpa salpa) and migratory pelagic 
species;  
Fisheries activities from the aforementioned point must be conducted by vessels who’s base 
port is from the island of La Graciosa, or by fisher that habitually fish in the MPA, which must 
be demonstrated/evidenced; 
The activity of recreational fishing using trolling methods targeting migratory pelagic species, 
which must not take place within 2nm from the outer perimeter of the fully protected  area 
(integral zone) (essentially creating the buffer zone); 

•  Sampling marine flora and fauna for scientific purposes, which is authorised by the General 

Secretariat of Marine Fisheries. 

According  to  Chuenpagdee  et  al.  (2013),  the  designation  of  the  MPA  occurred  in  a  top-down 
approach  by  national  and  regional  government.  The  president  of  the  local  cofradia,  initially  in 
support of the MPA, then changed their mind and spoke against it. Local fishers were apparently 
sceptical about the plan, due to the lack of formal discussions and confusing information by the 
cofradia. The MPA was established anyway, through a decree stating the proposal had the support 
of  the  fisheries  sector  (BOE,  1995).  One  group  affected  by  its  establishment  was  the  female 
shellfish gatherers who were not permitted to use the area - presumably as they were not included 
within at the design stage of the protected area. Chuenpagdee et al. (2013) also states that the 
establishment process was difficult due to resource competition between fishers and other users. 
The process was also entwined in a political struggle when local figures used the implementation 
of the MPA as a stage to confront with national government. As a result of these establishment 
issues,  the  MPA  continued  to  be  a  source  of  contention.  A  socio-economic  study  found  that 
professional fishers generally perceived the MPA negatively, despite having a generally positive 
perception that the MPA is good for the local economy (Alban et al., 2008). This same study also 
found  that  professional  fishers  displayed  a  majority  of  negative  responses  when  asked  about 
spillover effects.   

The  management  body  for  the  MPA,  “Management  and  Monitoring  Joint  Commission”  includes 
managers,  political  representatives  and/or  technical  staff  from  the  state,  regional,  and  local 
fisheries  administrations,  a  technician  from  IEO  and  representatives  from  the  local  fishers 

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association  (“Cofradía  de  Pescadores”).  Running  in  parallel,  there  is  also  a  “Scientific  and 
Consultative  Committee”  made  up  of  the  manager  from  the  Canary  Government  as  well  as 
representative  from  Canary  research  institutions  (University  of  La  Laguna,  University  of  Las 
Palmas de Gran Canaria, Canary Institute of Marine Sciences) and IEO. However, the committee 
is  referred  to  as  a  ‘paper’  committee,  as  it  has  never  held  a  meeting  (EMPAFISH  consortium, 
2008). Other shortcomings of the MPA include; non-participation of local representatives from the 
research institutions at Joint Commission meetings; public participation in the Commission; low 
frequency of Commission meetings; a lack of established monitoring programmes other than the 
IEO fisheries monitoring; insufficient funding for surveillance; and lastly, the largely failed role of 
the “Cofradía de Pescadores” which left fishers without sufficient representation and leadership 
on their behalf (EMPAFISH consortium, 2008). 

No commercial vessels operate in the area since the 1990s, after the abundance of their target 
species decreased (Vandeperre et al., 2008). Since the MPA establishment only the artisanal fleet 
operate within the MPA. Allowed fisheries activities within the zones is documented within Article 
4 of the establishing legal document published in 1995 (BOE, 1995). Subsequently, two Orders 
and  a  Resolution  were  passed  in  1999,  2001  and  2022,  respectively  (BOE,  1999;  BOE,  2001; 
BOE, 2022). The order of 1999 specifies regulations regarding diving, while the 2001 order adds 
an  additional  article,  Article  8.  Article  8  sets  rules  regarding  recreational  fishers  being  in 
possession  of  a  relevant  licence  while  in  the  MPA,  as  well  as  authorisation  for  the  practice  of 
recreational fishing, issued from the General Secretariat for Maritime Fisheries. Further limitations 
to the number of recreation vessels are stated – with 30 vessels per day simultaneously allowed 
access between May and October, and 15 per day between November and April. The most recent 
update to the management of La Graciosa MPA, is the 2022 Resolution.  

The  resolution  was  passed  on  December 7th  2022  by  the  General  Secretariat of  Fisheries,  and 
updates the census of vessels authorised to carry out professional maritime fishing in the MPA. 
(BOE, 2022). This resolution states that the maximum number of boats permitted to be authorised 
to operate within the MPA is set at 50 vessels and they must come from a base port of Caleta del 
Sebo, Orzola, Arrecife or Puerto del Carmen (Figure 1). The 2001 list of authorised vessels had a 
maximum of 73 (Vandeperre et al., 2006). The 2022 resolution includes a requirement for vessels 
to  also  be  registered  on  the  General  Registry  of  the  Fishing  Fleet  –  Spain’s  new  national  fleet 
register encompassing their outer territories. Exclusion criteria from La Graciosas authorised list 
of 73 vessels includes; a) removal from the General Registry of the Fishing Fleet; substitution by 
another vessel; selling capture through unauthorised first sale ports; change of base port to one 
other  than  listed  as  authorised;  failure  to  provide  catch  information;  do  not  carry  out  fishing 
activity within the scope of the marine reserve (with an exclusion clause for force majeure); and 
lastly, failure to comply with the rules of marine reserve or that the skipper or shipowner have 
firm administrative sanctions in the previous two years. 

With only the artisanal and recreational fleet operating in the MPA, few gears are utilised and are 
mainly hook and line based, with purse and beach seining also occurring all year round. Of the 24 
species  targeted,  Sparisoma  cretense,  Merluccius  merluccius,  and  Sarpa  salpa  are  the  major 
species  targeted  (by  weight),  landing  25,  12  and  11  tonnes  landed  in  2005,  respectively 
(Vandeperre et al, 2006).  Details of the methods used, their seasonality, as well as the target 
and bycatch species can be seen in Table 1. 

Since  its  establishment in  1995,  the La  Graciosa  MPA  has  likely  influenced  the  area's  ecology, 
potentially leading to the recovery of fish populations and their subsequent spillover beyond the 
protection boundaries. Although monitoring efforts are in place, there is currently a lack of specific 
studies addressing ecological and/or fishery spillover. This research fills this gap by incorporating 
previous studies, monitoring data,  and stakeholder  insights to assess whether the La Graciosa 
MPA is indeed fostering spillover effects. 

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Figure  1.  Map  of  the  La  Graciosa  MPA,  including  ports  of  the  islands  included  within 
authorised list of base/home port (Arrecife or Puerto del Carmen are not within scope 
of map). 

234 

 
 
 
 
Diplodus vulgaris, 
Phycis phycis, 
Scorpaena spp., 
Mycteroperca fusca, 
Balistes capriscus, 
Diplodus sargus, 
Bodianus scrofa, 
Pseudocaranx dentex, 
Pontinus kuhlii, Pagrus 
auriga, Diplodus 
cervinus, 
Parapristipoma 
octolineatum 
- 

Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Table 1. Table showing the gears, seasonality of their use, target and bycatch species 
caught within the zones of La Graciosa MPA (Vandeperre et al, 2006). 

Area 

Gear 

Seasonality 

Target species 

Bycatch species 

Fully 
protected 

- 

- 

- 

- 

Handline 

Depends on 
species 

Sparisoma cretense, 
Pagrus pagrus, 
Spondyliosoma cantharus, 
Serranus atricauda, 
Pagellus erythrinus, 
Epinephelus marginatus 

)
s
r
e
t
a
w

l

a
n
r
e
t
n
i
(

r
o
i
r
e
t
n
I

e
s
U
d
e
t
c
i
r
t
s
e
R

Exterior (external 
waters) 

Pole and 
line 
Pole and 
line with 
live bait 

Jig 

Purse 
seine 

Beach 
seine 

Shellfish 
seeking 
Octopus 
long-
handled 
tool 
Trap 

Electric 
reel hook 
and line 

April-Oct 

Sparisoma cretense 

April-Nov 

Seriola spp., Mycteroperca 
fusca, Sphyraena 
viridensis, Dentex dentex 

- 

May-Oct 

Loligo vulgaris 

Sepia officinalis 

All seasons 

Sarpa salpa, Boops boops, 
Sardina pilchardus, 
Engraulis encrasicolus 

All seasons 

Atherina presbyter 

Mar-Nov 

Patella spp. 

Oblada melanura, 
Trachinotus ovatus, 
Sardinella spp., Belone 
belone 

Sardina pilchardus, 
Sardinella spp., Belone 
belone, Boops boops 
Osilinus spp. 

All seasons 

Octopus vulgaris 

- 

Mar-Nov 

All seasons 

Scorpaena spp., Dentex 
spp., Phycis phycis, Pagrus 
pagrus 
Merluccius merluccius, 
Polyprion americanus 

Muraena helena, 
Gymnothorax spp., 
Conger conger 
Pagellus bogaraveo, 
Schedophilus ovalis, 
Mustelus mustelus 

3  AIMS AND OBJECTIVES 

The  objective  of  this  case  study  is  to  determine  whether  spillover  may  be  occurring  in  the  La 
Graciosa MPA. Established in 1995, having now 28 years of protection, the aim of this study is to 
test  the  assumption  that  the  protection  has  allowed  fish  species  within  the  MPA  to 
recover/increase in comparison to when it was unprotected, and is now producing a net emigration 
of fish to the outside of the protected area, i.e., the MPA, and the protection it affords, is causing 
spillover effect. 

To address whether spillover may or may not be occurring in La Graciosa, this case study aims to 
address the following specific objectives: 

• 

• 

• 

Evaluate  whether  the  perceptions  of  stakeholders  indicate  a  likelihood  of  spillover  effects 
occurring as a result of the MPA establishment; 
If and where appropriate, use a quantitative approach to evaluate the spillover effects that 
could be occurring, using metrics found through literature review; 
Provide  recommendations  for  refining  or  improving  the  methodology  for  future  spillover 
assessments. 

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4  METHODOLOGY 

This case study uses both quantitative and qualitative methodologies to address the question of 
whether spillover might be occurring within the La Graciosa MPA. A combination of both desk-
based research (literature review) and subsequent quantitative assessment of metrics found in 
the literature, and stakeholder interviews using an online questionnaire was used.  

4.1  Literature review and data collection 

Firstly, to collect background information and identify any quantitative sources of data a literature 
review was conducted. The literature review used a three-step assessment protocol which entails: 
(i) collation and screening;  (ii)  extraction; and (iii) critical appraisal.  Searches were conducted 
using  Google  Scholar  which  has  been  shown  to  be  useful  for  both  peer-reviewed  and  grey 
literature,  as  well  as  broad  searches  to  obtain  information  from  government  reports  and 
competent authority websites. Searches used Boolean logic to combine terms for the La Graciosa 
and different topics. For example, “La Graciosa” OR “la Isla Graciosa y de los islotes del norte de 
Lanzarote” AND “spillover” OR “fish biomass” OR “fishery”. This resulted in searches that provides 
literature  relating  to  research  conducted  in  the  La  Graciosa  MPA  focusing  on  changes  in  fish 
populations, fish community assemblages or impacts on the local fishery.  

The  resultant  articles  obtained  from  the  literature  search  were  then  compiled  and  analysed  to 
extract any data regarding spillover from the La Graciosa MPA. All literature were first screened 
by  title,  and  then  by  abstract  to  ensure  only  relevant  literature  was  assessed.  Articles  were 
omitted based on relevance of both title and abstract. Literature in Spanish was considered, but 
not fully translated as this would have taken too much time. Those articles with what appeared 
to be relevant information was translated as needed. 

To perform a quantitative assessment of spillover, further criteria were added to the literature 
review to identify metrics that indicate whether spillover may be occurring. These data types and 
collection methods are highlighted in Table 2. 

Table 2. Overview of main data types from which spillover effects could potentially be 
analysed, followed by the variety of methods with which these can be collected. 

Fishery data type 

Collection methods 

Fish abundance / biomass 

AIS/VMS data and/or logbook data 

Small-scale fisheries logbook data 

Visual detections (by transect) 

Capture-Recapture / Mark-Recapture  

Marine biological surveys 

(Light) traps 

Larval biomass 

Plankton samples 

Fish size, weight, and age 

Fish movement 

Market sampling 

Marine sampling (surveys) 

Acoustic telemetry network 

Tagging 

Where literature contained information such as those indicated in Table 2, data from these articles 
were collated. Values were then compared against the framework highlighted in Table 3 (see the 
spillover assessment advisory protocol in Annex 5), which provides an indication of whether or 
not the data may indicate spillover based on a BACI (Before, After, Control, Impact) approach. 

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Table 3. This table provides an overview of the conclusions that can be drawn from the 
classic  MPA  BACI  approach  in  assessing  spillover.  The  examples  presented  are 
theoretical. The first two columns describe the difference in biomass before and after 
establishment of the MPA in the MPA site (Δ MPA) and in the reference site (Δ Ref). The 
potential  combinations  of  changes  in  biomass  were  named  in  the  column  scenario 
name. The last three columns indicate  whether a conclusion can be drawn from each 
scenario regarding the total biomass of the MPA and reference site, whether the MPA 
provides protection benefits, and whether the results indicate spillover.  

Δ MPA  Δ Ref  Scenario name 
0%  Stable 

0% 
0%  10%  Ref. site increased 

10% 
10% 

0%  MPA increased 
5%  Both increased, but MPA stronger 

5%  10%  Both increased, but ref. site stronger 

10%  10%  Mutual increased 
-10% 

0%  MPA decreased 

Biomass?  Protection?  Spillover? 
Consistent  No 
Increase  No 
Yes 
Increase 
Yes 
Increase 
Increase  No 
Increase 
Decrease  No 

No 
No 
No 
Potentially 
Potentially 
Potentially 
No 

Potentially 

-10% 

5% 

-5%  10% 

-10%  10% 

Ref. site increased, but MPA 
decreased stronger 
MPA decreased, but ref. site 
increased stronger 
MPA decreased as strong as ref. site 
increased 

Decrease  No 

Increase  No 

Consistent  No 

-10% 

0%  -10%  Ref. site decreased 

-5%  Both decreased, but MPA stronger 

Decrease  Yes 
Decrease  No 
-5%  -10%  Both decreased, but ref. site stronger  Decrease  Yes 
Decrease  No 

-10%  -10%  Mutual decreased 

10% 

-5% 

5%  -10% 

10%  -10% 

Ref. site decreased, but MPA 
increased stronger 
MPA increased, but ref. site 
decreased stronger 
MPA increased as strong as ref. site 
decreased 

Increase 

Yes 

Decrease  Yes 

Consistent  Yes 

No 

No  

No 

No 
No 
No  
No 

No 

No 

No  

4.2  Quantitative assessment of focal studies 

Since before the establishment of the La Graciosa MPA the Ministry of Fisheries of the Government 
of the Canary Islands has been conducting monitoring and research alongside the University of 
La Laguna. Two studies, Salz (2015) and Brito et al., (2006) are the main sources of quantitative 
data used for this case study, as the reports provide abundance and or biomass data that could 
be used assess against. Additionally, Brito et al., (2006) provides Figure 2, providing locations of 
sampling sites for additional context. 

Within  a  status  review  of  Island  Grouper  (Mycteroperca  fusca),  Salz  (2015)  references  data 
published  by  Falcón  et  al.  (2007),  which  is  not  publicly  available  online.  Salz  (2015)  provides 
Figure  3  –  mean  density  of  island  grouper  per  100  m2,  within  the  integral  reserve  and  two 
unknown reference sites across four years (1994, 1995, 2004 and 2005). The earlier years were 
treated as before and the latter two years as after the MPAs establishment. The data was collected 
via SCUBA using Underwater Visual Census (UVC) (Salz 2015). It is noted by the author here that 
it is likely that these data are based the same data as provided in Brito et al., (2006). Values were 
extracted  from  Figure  3  using  ‘Web  Plot  Digitizer’  and  were  used  to  assess  against  the  BACI 
assessment  criteria  shown  in  Table  3.  ‘Web  Plot  Digitizer’  enables  the  accurate  and  precise 
estimation  of  values  by  calibrating  graphical  plots’  axes  within  the  tool  and  measuring  bars, 
distances etc (Rohatgi, 2022). 

The report by Brito et al., (2006) studies multiple fish populations, and is carried out “in-situ”, 
with data collected using UVC. It’s very likely that the methodology used is the same reported by 
Salz,  (2015).  The  method  uses  a  stationary  visual  count  method  from  a  fixed  point,  which  is 
suitable for rocky bottoms of great heterogeneity (Harmelin-Vivien et al., 1985; Bohnsack and 
Bannerot, 1986). This technique was later modified by Falcón et al. (1993), whereby a diver is 
located in the centre of an imaginary circle that has a radius of 5.6 m (100 m2 of surface area) 

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which is marked by a rope, at which a diver positions themselves at the end of. After five minutes 
of counting the observer switches side and repeats, after which they spend some time looking for 
cryptic  species  that  may  have  gone  unnoticed.  All  fishes  that  enter  the  imaginary  circle  are 
counted;  if  a  group  of  fish  partially  enters,  all  the  fish  of  that  group  are  counted;  no 
groups/individuals that re-enter the circle are counted again (Brito et al., 2006). Both the number 
of specimens and their size are recorded for each species, as precisely as possible. Despite many 
replicates being conducted at each site, only six were chosen to conduct their analysis, as they 
were  all  collected  by  the  same  observer,  reducing  bias  and  improving  power  for  comparison. 
Values are provided as a mean abundance, standardised as number of individuals per 100 m2, for 
each sampling location (N= 12; Figure 2) for both 1994 and 2005. Sampling occurred within the 
No-take integral reserve (n=2), within the wider MPA (n=4) and outside of the MPA (n=6). Values 
of biomass are also recorded (presumably in grams, however the metric is not stated) for two 
species S. cretense and S. atricauda. 

Figure 2. Sampling locations as provided in Brito et al., (2006) 

4.3  Stakeholder survey 

To address the topic of spillover at La Graciosa, an open-ended questionnaire was developed to 
capture stakeholder opinions on, for example, how aware the stakeholder was of the regulations 
and management measures of the MPA (see the questionnaire in Annex 4). The closed questions 
were statement-based and used Likert scale answer categories (such as: Strongly agree; Agree; 
Neutral; Disagree; Strongly Disagree) for the stakeholder to choose from.  

The  questions  were  grouped  into  four  broad  categories  to  encapsulate  the  key  issues  being 
studied. These included:  

I. 

Respondent information. The first section required basic information from the respondent, 
including their name, institution and the type of stakeholder category they belonged to. 

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II. 

III. 

IV. 

Background information. The  second section of  the questionnaire gathered background 
information from the stakeholder to understand more about the respondent and their use 
of the MPA. Questions included knowledge of when the MPA was established, the type of 
restrictions in place and how long the stakeholder has been associated with the MPA either 
through research, fishing or managing it.  
Fishery impacts of MPAs. The third section explored the respondent’s perceptions of the 
socio-economic  impacts  of  spillover  from  the  MPA.  Stakeholders  were  asked  to  state 
whether the designation of an MPA / area where fishing is limited has led to an increase 
in  revenues  for  fishers,  whether  the  fishing  community  in  the  area  feel  their  fisheries 
livelihoods are more secure after the MPA was established, and the extent to which they 
believe spillover from the MPA has influenced the catch composition in adjacent fishing 
grounds. 
MPAs  as  management  tools.  The  fourth  section  of  the  questionnaire  focused  on  the 
respondent’s  perceptions  on  whether  MPAs  are  conservation  or  fisheries  management 
tools.  Stakeholders  were  asked  to  state  whether  their  local  MPA  was  acting  as  a 
conservation tool, a fisheries management tool or both. Other questions under this section 
required  stakeholders  to  state  their  agreement/disagreement  on  whether  the 
establishment of MPAs is an effective conservation strategy to support fish populations 
and  commercial  fisheries  in  their  area.  Respondents  were  also  asked  to  indicate  what 
factors they thought were contributing to spillover effects. 

Four  key  stakeholder  groups  were  targeted  under  this  consultation  including  commercial  and 
recreational fishers, fisheries managers and government authorities, scientists and environmental 
non-government  organisations  (NGOs).  Therefore,  while  the  four  sections  of  the  questionnaire 
where the same, specific questions were  included  for each of the four respondent groups. The 
questionnaire (in English) was translated into Spanish and set up as an online survey. 

To gain details of stakeholders particular to the  La Graciosa MPA, stakeholders were identified 
through speaking with team members from project partners (Spanish Institute of Oceanography 
(IEO)/Spanish National Research Council (CSIC)). Names, position, sector and contact details of 
stakeholders who have had previous or current experience of La Graciosa were provided. These 
contacts formed the base from which to target specific stakeholders. Additional stakeholders were 
contacted after it had become apparent the stakeholders contacted originally had not responded 
or provided any perceptions through the questionnaire. Initial requests to stakeholders were made 
in July 2023, with subsequent reminders sent twice in August. 

5  RESULTS 

5.1  Literature review and quantitative assessment of spillover effects 

Quantitative assessment of abundance data presented in Salz (2015) 

When compared against the framework for a BACI design in Table 3, these results do not conform 
to  within  the  stated  trends  of  change  between  5  and  10%.  However,  taking  these  values  as 
general trends and evaluating against the name/description does indicate that reference site R1 
would fit against scenario name and descriptor of both increasing, but MPA increased stronger, 
potentially indicating a spillover effect (NT (no-take integral reserve) %Δ = 222; R1 %Δ = 277). 
This may also indicate a protective functioning of the MPA, as abundance is greater in the fully 
protected area than in the reference site R1. The other reference site, R2, would fit against the 
descriptor  of  both  increasing,  but  MPA  increasing  stronger  (R2  %Δ  =  70),  also  potentially 
indicating a spillover effect.  

Due  to  not  having  access  to  the  raw  dataset,  it  is  unknown  whether  R1  and  R2  are  differing 
distances away from the fully protected area, as this information is not disclosed  in Salz 2015. 
The study by Falcon et al. (2007), where this data originated, is not publicly available.  

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Figure 3. Mean density (±SE) of island grouper (fish/100m2) recorded in years before 
(1994  and  1995)  and  after  (2001  and  2005)  reserve  implementation  in  different 
management  zones:  NT  =  no-take  integral  reserve;  R-based  sites  (R1  and  R2)  = 
traditional  commercial  gears,  recreational  shore  fishing  and  SCUBA  allowed  (Source: 
Falcon et al., 2007). Based on restricted use zone/outside the buffer. 

Table  4.  Estimated  values  of  fish/100m2  extracted  from  Figure  3  using  ‘Web  Plot 
Digitizer’ (Falcon et al., 2007; Salz 2015), included calculated average fish per 100m2 
for before and after, percent change  (%Δ) comparing before and after for each zone 
for M. Fusca. 

Zone 

Year  Period 

fish/100m2 

SE 

Average fish / 
100m2 

%Δ 

ΔMPA vs Δref 
Scenario 

No take  1994  before 

No take  1995  before 

No take  2001 

After 

No take  2005 

after 

R1 

R1 

R1 

R1 

R2 

R2 

R2 

1994  before 

1995  before 

2001 

After 

2005 

after 

1994  before 

1995  before 

2001 

After 

0.33 

0.51 

2.01 

0.69 

0.42 

0.33 

0.76 

2.09 

1.00 

0.34 

1.42 

0.48 

0.87 

3.23 

0.86 

0.69 

0.61 

1.13 

3.34 

1.31 

0.53 

2.16 

R2 

2005 

after 

0.86 

1.09 

0.42 

1.35 

0.38 

1.43 

0.67 

1.14 

222.62 

NA 

277.63 

70.63 

Both increased, 
but ref. site 
stronger - 
Potential Spillover 
indicator 

Both increased, 
but MPA stronger 
- Potential 
Spillover indicator 
and an indicator 
of protective 
functioning. 

Values taken from both Brito et al. (2006) and Salz, (2015), who both report on M, fusca, both 
indicate similar results. However, a question mark remains over the sampling locations reported 
in Salz (2015), but given results presented in Figure 5, its entirely plausible (and likely) the two 
sites R1 and R2 correspond to the sites Punta de la Mareta and Punta Fariones, respectively, given 
the similarity of results. Given these similarities, and without knowing reference locations of  R1 

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and R2, these results will not be discussed further other than where the data is thought to match 
values presented by Brito et al. (2006). 

Quantitative assessment of abundance and biomass data, Brito et al., (2006) 

In total, data for six species were extracted and assessed against the standards provided in Table 
3 using values provided in the Annex of Brito et al. (2006). The species selected for assessment 
against  the  BACI  approach  are  Sparisoma  cretense,  Diplodus  cervinus,  Centrolabrus  trutta, 
Mycteroperca fusca, Sarpa Salpa, and Serranus atricauda, as they provide a mix of trophic levels 
(Table 5). Two species which are not target species are also included as this can act as a control 
for other changes in the ecosystem (Table 5). Another factor in the choice of these species was 
data coverage across all sites and years, as for many species data was not available throughout. 
These species enabled a comprehensive coverage. 

Results from this assessment are tabulated in a similar format as those in Table 4 and included 
in  this  case  study  as  supplementary  material.  The  results  of  the  BACI  assessment  have  been 
graphically plotted to present a comparison between the integral reserve and all the sites surveyed 
by Brito et al., (2006) (Figure 4 and Figure 5).  

Table 5. Species, trophic level, whether or not the species is targeted in the region, as 
well as an indication of whether abundance and/or biomass data was extracted for a 
quantitative assessment of potential spillover (Froese and Pauly, 2023). 

Species 

Trophic level 

Target 

Biomass and/or abundance 

Centrolabrus trutta 

Diplodus cervinus 

Mycteroperca fusca 

Sarpa Salpa 

Serranus atricauda 

Sparisoma cretense 

3.5   ± 0.4 

3.4   ± 0.1 

4.3   ± 0.8 

2.0   ± 0.0 

4.3   ± 0.6 

2.9   ± 0.3 

Bycatch 

Bycatch 

Target 

Target 

Target 

Target 

Abundance 

Abundance 

Abundance 

Abundance 

Abundance and Biomass 

Abundance and Biomass 

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Figure  4.  A  tiled  plot  representing  sites  that  indicate  potential  spillover  when  using  a  BACI  approach  to  compare  %  Δ  between  the  integral 
reserve  and  all  other  surveyed  sites.  Details  included  are  a  description  of  the  scenario  which  fits  the  %  Δ  most  appropriately  and  includes 
assessments of both abundance and biomass for two species. Empty cells occur when no values are present to be able to make an assessment. 
Sites are ordered based on distance from integral fully protected area. 

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Figure 5. A tiled plot representing sites that indicate potential spillover when using a BACI aproach to compare % Δ between the Integral 
reserve and all other surveyed sites. Using only abundance, included are a description of the scenario which fits the %Δ most appropriately for 
four species. Empty cells occur when no values are present to be able to make an assessment. Sites are ordered based on distance from 
integral fully protected area

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Population abundance indicator 

Sparisoma cretense  

The results presented in Figure 4 indicate that S. cretense had the highest number of potential 
spillover indicators based on percent change (% Δ) between the fully protected integral zone and 
all  other  sites  sampled.  Based  on  an  average  from  the  two  sampling  sites  within  the  integral 
zones, the % Δ was 250. All sites from within the boundaries of the MPA indicate that spillover 
could be occurring (Punta Fariones %Δ = 908, Cuevas Coloradas %Δ = 233, Montaña Amarilla 
%Δ = 166 and Punta de la Mareta %Δ = 261), but do not suggest any kind of gradient based on 
detail descriptors and distance from integral reserve. Interestingly, where there is an indication 
of potential spillover from a site located outside of the MPA, detail descriptors indicate that while 
both increased, the MPA increased stronger in all cases. While within the MPA, all possible detail 
descriptors of potential spillover are indicated (Figure 4; Table 3). The fact the closest reference 
site to the integral reserve actually increased more than the integral reserve itself may indicate 
that density dependence within the integral reserve has been hit, and spillover has occurred into 
a more suitable habitat with a higher density dependence. 

Serranus atricauda 

For S. atricauda, results shown in Figure 4 point to fewer indicators of possible spillover based on 
abundance. Data provided allowed comparison of two reference locations within the MPA with the 
integral zone (Cuevas Coloradas and Punta de la Mareta). Where potential spillover is indicated 
in these two locations, both detail descriptors indicate that while both increased in abundance, 
the MPA saw a greater increase (IR%Δ= 757; Cuevas Coloradas %Δ= 366; Punta de la Lareta 
%Δ= 134). Outside of the MPA, five locations provided abundance metrics to compare against. 
These locations indicate that that three of five reference locations outside the MPA experienced a 
decrease in abundance for the reference site, while the MPA increased stronger (La Juradita %Δ 
=-34; Veril de Puerto del Carmen 2 %Δ = -48; Mala % Δ = -75).  

Centrolabrus trutta 

For C. trutta, average % Δ within the integral reserve was -87.  Only one comparison between 
the integral reserve and reference points within the MPA could be made, finding no indication of 
spillover (Cuevas Coloradas %Δ = -90, a mutual decrease). A decrease within the integral reserve 
for  a  nontarget  species  indicates  some  sort  of  confounding  variable,  whether  that  might  be 
ecological in terms of competition or local environment is unknown. But with a high resilience, 
and a population doubling time less than 15 months, an increase and/or an indication of spillover 
or  protective  functioning  would  otherwise  be  expected  from  a  species  with  such  parameters 
(Froese et al., 2017).  

Mycteroperca fusca 

In terms of the species with the highest frequency of spillover indicators, M. fusca would be ranked 
third, with two indications. Abundance metrics provided for M. fusca enabled comparison with all 
sites within the MPA boundary, with the integral reserve estimated to have experienced a %Δ of 
100% (0.67 average fish/100 m2 in 1994 versus 1.34 in 2005). Potential spillover for M. fusca is 
indicated at two sites within the wider reserve boundary - Punta Fariones (%Δ = 49) and Punta 
de la Mareta (%Δ = 1112), which are 12 and 20 km away from the integral reserve, respectively. 
In the case of Punta Fariones both increased, but the MPA increased stronger, while at Punta de 
la Mareta both increased, but the reference site increased stronger. The only two reference sites 
outside  the  MPA  that  were  able  to  be  assessed  both  indicate  that  M.  fusca  populations  have 
remained stable at these locations when compared with the integral zone (Mala %Δ = 0; Veril de 
Puerto del Carmen 2 %Δ = 0).  

Sarpa salpa 

Values of abundance provided for S. salpa enabled comparison between the integral reserve and 
four  reference  sites,  however  only  one  was  within  the  boundary  of  the  MPA.  None  of  these 
comparisons indicate potential spillover. The comparison between the integral reserve and Punta 
Fariones (12 km away from the IR) found that the MPA(IR) decreased (IR %Δ = -82) while the 
reference site increased stronger (Punta Fariones %Δ = 650). Mala, the next closest reference 
site, outside the MPA but 21 km away from the IR, had the same result. Mala, however, saw a 
24,705 % change in abundance (0.17fish/100 m2 in 1994 to 42.17 fish/100 m2 in 2005). Playa 

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del Tío Joaquín, situated very close to Mala (Figure 2) saw abundance decrease in both sites, but 
stronger in the reference site (Playa del Tío Joaquín %Δ = -100).  

Diplodus cervinus 

Values extracted allowed the comparison of the integral reserve to all four sites within the MPA, 
and one outside it (Figure 5). The integral reserve saw a decrease of  – 36%, while the closest 
reference point, Punta Fariones also declined (%Δ = -66). Both sites decreasing, but the reference 
site  decreasing  more  is  a  descriptor  of  potential  protection.  However,  this  assessment  of 
protective functioning comes from both the integral reserve (-36%) and the reference site (-66%) 
decreasing in abundance, but the reference site decreasing more. This could suggest ecological 
effects, such as potential competition with  S. cretense, which from data presented in this case 
study, appears to have hit a density dependence limit and could be having spillover effect in other 
parts within the MPA. However, the next closest reference site, Cuevas Coloradas, saw an increase 
of 194%, i.e. the MPA decreased but the reference site increased stronger. 

Population biomass indicator 

Sparisoma cretense 

In total for S. cretense comparisons of %Δ of biomass was able to be conducted for nine reference 
sites,  four  of  which  are  within  the  MPA  (IR  %Δ  =  2).  Of  the  four  sites  within  the  MPA,  three 
indicate potential spillover and all display the same scenario descriptor – both increased, but the 
reference site increased stronger. These are Punta Fariones (%Δ= 504); Cuevas Coloradas (%Δ 
= 62); and Punta de la Mareta (%Δ = 137). Of the five reference sites outside the MPA that are 
compared,  potential  spillover  is  indicated  in  one  (Mala  %Δ  =  4)  where  the  same  scenario 
descriptor is applicable as those above. The other reference sites that were able to be compared 
that do not indicate spillover all fit the descriptor of an increase within the MPA, but the reference 
site decreased stronger (Montaña Amarilla %Δ = -20; Playa del Tío Joaquín %Δ = -100; Veril de 
Puerto del Carmen %Δ = -4; Punta Gorda %Δ= -44; La Juradita %Δ = -30).  

Serranus atricauda 

For  S. atricauda, comparison of %Δ of biomass was  conducted for  eight reference  sites, three 
within the MPA, the other five outside the MPA. The IR itself is estimated to have had a %Δ of 
766 (64 g/100 m2 to 559 g/100 m2). Comparisons made with the IR and reference sites within 
the MPA indicate potential spillover in two - Cuevas Coloradas (%Δ = 28) and Punta de la Mareta 
(%Δ  =  23).  For  comparisons  made  with  reference  sites  outside  the  MPA  (n=5),  four  indicate 
possible spillover (Playa del Tío Joaquín %Δ = 425; Veril de Puerto del Carmen 2 %Δ = 27; Punta 
Gorda %Δ =277; La Juradita %Δ =407). Interestingly, of the eight comparisons made to the IR, 
all  those  that  indicate  spillover  fit  to  the  descriptor  of  both  increasing  biomass  but  the  MPA 
increasing  stronger.  Similarly,  all  those  points  that  do  not  indicate  potential  spillover  but  did 
contain  data  to  compare  exhibit  the  same  descriptor  of  a  reference  site  decreasing,  but  MPA 
increasing stronger (Punta Fariones %Δ = -3 and Mala %Δ = -47). 

5.2  Stakeholder perceptions  

Despite reminders via email and phone calls, the author notes difficulties in engaging stakeholders 
in this area throughout the stakeholder engagement period. Out of the 50 stakeholders contacted 
14% responded with answers to the survey. The remaining contacts  were Out-of-Office replies 
(18%), provided no reply (58%), indicated interest but did not respond to the survey (4%), or 
responded that the study was not applicable to them (6%). Given the low sample size (n = 7), 
the responses from this case study were combined with responses from  another case study by 
Alban et al, (2008) and presented in the main report. 

Among  the  seven  responses  gathered,  four  were  deemed  incomplete  or  unhelpful,  while  the 
remaining three encompass contributions from two fisheries management authority stakeholders 
and a  single  scientist. The limited  number  of responses, coupled with inconsistent provision  of 
answers for each question, restricts the ability to compare perceptions across stakeholder groups 
for most questions. Notably, both fisheries management authority stakeholders indicate observed 
changes  in  fishers'  catches,  note  increases  in  catch  per  unit  effort  (CPUE)  within  the 
MPA,  and  express  moderate  agreement  regarding  spillover  effects  contributing  to  the 
recovery of overexploited fish populations in adjacent fisheries. Conversely, the scientist 
presents a slightly divergent perspective, contending that there is  no discernible spillover of 

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either fish or larvae from the MPA benefiting fisheries, citing concerns over the size and 
placement of the no-take integral reserve. Despite these disparities, both fisheries management 
authority  and  scientist  stakeholders  concur  that  the  MPA  has  elicited  diverse  biological 
responses  in  fish  populations,  leading  to  varied  benefits  for  fisheries,  alongside 
acknowledging the economic advantages brought about by the MPA. 

6  DISCUSSION 

Using a BACI approach, an assessment was carried out using data provided in Salz (2015) and 
Brito et al., (2006) to assess whether their results indicate the potential occurrence of spillover.  

6.1  Quantitative assessment 

In total, six species of fishes were assessed against a BACI design for assessing spillover, using 
both abundance and biomass of fish per 100 m2. Findings indicate that the response to 10 years 
of protection of biomass and abundance varies greatly between species and sites. Given the 10 
years of protection this MPA has provided, some indications of spillover were expected, although 
no prior assumptions of which species or sites would yield more spillover effects were made. While 
the  data point to being fairly certain  that some species are  displaying  spillover indicators, this 
cannot be said for all species. Results presented here point to potential spillover effects 
occurring for three out of six species assessed, across a number of sites, both within the 
MPA, and to a lesser extent, outside it. 

Species identified as indicator species by Brito et al., (2006) (S. cretense and S. atricauda) appear 
to  be  living  up  to  their  standard,  as  these  two  species  produced  more  indications  of  potential 
spillover than all four of the other species combined when looking at abundance. S. cretense is a 
species  of  high  local  economic  importance,  with  25  tonnes  landed  in  2005  (Vandeperre  et  al., 
2006) and methods allowing their capture (Handline and Pole & Line) written into the establishing 
legal text (traditional gears; BEO, 1995). It is possible to suggest that the MPA has a protective 
functioning that is potentially causing spillover effects for this species in particular. The author 
notes that this indication of potential spillover effects is largely indicated from within the MPA, 
from the integral zone to the reference zones within the MPA. 

One potential confounding variable not taken into account is ecological effects caused by effects 
such  as  density  dependence  within  the  food  web,  which  may  explain  the  variation  in  effect 
responses between species. Both S. atricauda and M. fusca have similar trophic levels (Table 5). 
While S. atricauda had many positive spillover indications and had an increase in abundance of 
757% at the integral reserve, M. fusca had much fewer, and abundance only rose 100%. This is 
despite almost identical trophic levels and exactly the same resilience (Low, minimum population 
doubling time 4.5 - 14 years, Froese et al., 2017). Whether this difference is related to fishing 
pressure, or other ecological effects is unknown but what is certain is that M. fusca has a slightly 
higher fishing vulnerability and fetches a higher price when compared with S. atricauda (Cheung 
et al., 2005; Sumaila et al., 2007). This provides an example of the confounding variables that 
may  be  occurring  when  assessing  spillover  indicators  using  metrics  such  as  fish  abundance  or 
biomass. 

Comparing the results between the two species where both abundance and biomass are assessed 
provides an interesting comparison. S. atricauda increased in 757% in abundance and 766% in 
biomass within the integral reserve. While S. cretense increased 250% in abundance and only 2% 
in biomass. This points to  S. cretense  increasing in number, but actually  their overall biomass 
(size) has decreased, which would affect marketable catches for fishers. This data warrants further 
explanation as it may suggest that despite the spillover indicators, actual fishable spillover may 
not be occurring. Assessing the proportion of fishery spillover (i.e. the proportion of this biomass 
that  can  be  fished,  taking  into  account  regulations  and  accessibility)  relative  to  the  spillover 
indicators may be more informative than from a fisheries perspective (Di Lorenzo et al., 2016). 
Unfortunately, no sampling was found from the partially protected  area (buffer zone), which is 
missed  opportunity  to  compare  between,  especially  given  their  proximity  and  differences  in 
regulated activities. Other studies found partially protected areas to be a useful tool (Sciberras et 
al., 2013), and collecting data to contribute towards the research behind partial protection areas 
would be beneficial.  Additionally, it should be  noted that this study used  a fairly  small  sample 
sizes. 

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6.2  Stakeholder perceptions 

The quantitative data from Brito et al. (2006) are now 18 years old, so when comparing these 
results to a socio-economic survey conducted around the same time, Alban et al, (2008) found 
that 48% of fishers ‘fully disagree’ when asked whether they think the MPA helps to enhance fish 
abundance outside the protected area i.e. spillover. While some fishers did ‘fully agree’ (29%) 
with this statement, which does align with some of the results presented here, it is interesting to 
note how the question is worded. “Outside the protected area” could mean outside of the MPA as 
a whole, or outside of the integral reserve. Given some professional fishers are permitted to fish 
within the MPA, but not the integral reserve, the “protected area” could mean the integral reserve 
to them, but to others could mean the MPA as a whole. Regardless of this uncertainty, fishers of 
La  Graciosa  largely  disagree  that  the  MPA  help  enhance  abundance  inside  the  protected  area 
(29% rather disagree; 36% fully disagree). On the other hand, 36% do agree with this statement. 
Given these statements and results presented here, it would be interesting to know which fishers 
agree and disagree with these statements based on their chosen metier or target species. This 
would enable cross referencing and validation of the effects assessed here. Furthermore, Brito et 
al. (2006) indicates that poaching is likely occurring within the integral reserve due to an absence 
of  Epinephelus  marginatus  in  the  2005  survey,  when  previously  they  had  been  present.  It’s 
possible that many fishers don’t feel that the MPA does protect species abundance, particularly 
when the most numerous metier is handline fishing that specifically target E. marginatus, amongst 
five others species (Vandeperre et al., 2006). The largely negative views of fishers towards the 
MPA are interesting in the context of the history referenced in the background of this case study, 
as 71% of fishers fully agree the MPA helps protect biodiversity. It appears perceptions are split 
within  the  fisher  community,  with  a  larger  proportion  of  fishers  believing  the  MPA  is  not 
functioning as it should in terms of providing elevated fish levels within and outside the MPA, but 
the  majority  believing  it  protects  biodiversity.  From  a  more  contemporary  view,  stakeholder 
perceptions collected for this study tentatively suggest similar outcomes (albeit not from fishers), 
with  the  one  scientist  having  opposing  views  to  the  two  fisheries  authority  managers  when  it 
comes their perception of whether spillover is occurring or not. With that said, there is general 
agreement between these two stakeholder groups with regard to economic benefits provided by 
the MPAs protection, as well as varied biological responses with associated variation in catches. 

6.3  Summary 

These findings demonstrate a variation in ecological spillover responses that appear to depend on 
the  species  chosen  to  assess,  as  no  site  within  the  MPA  seems  to  dominate  where  spillover 
indication  occur.  It  is  entirely  possible  these  results  could  be  confounded  by  species  with 
preferences  to  habitat  types  found  at  different  sites  too.  Nevertheless,  both  abundance  and 
biomass seem to be in fairly similar agreement when compared for a species (Figure 4). These 
findings highlight the importance of continued monitoring of basic biological data. The author of 
this case study notes that it was very helpful to have stakeholder perceptions that were taken 
around the same time as the quantitative data was published. Having stakeholder perceptions to 
compare with the quantitative data taken at the same time enabled a useful contrast. These data 
are now more than 18 years old, with the MPA now providing nearly 30 years of protection.  It 
would be very informative to have updated values for both abundance and biomass. If this was 
possible, coupled with contemporary stakeholder perceptions and further indicators such as those 
found Table 2, a much more comprehensive comparison of spillover indicators may be achieved. 
Failing this, a raw dataset for the values provided in Brito  et al., (2006), with more values for 
biomass relative to those available for abundance, would allow a deeper understanding of spillover 
effects and possibly confounding variables such as those highlighted when comparing delta % of 
biomass and abundance between species. A further critique of the methods used here is the use 
of reference sites >50 km away from the fully protected area and whether spillover effects could 
be observed at this distance. 

7  CONCLUSIONS 

To answer the question of whether spillover could be occurring at the La Graciosa MPA, is not a 
straightforward question. There is evidence to suggest spillover effects are occurring for 
both  the  indicator  species  Serranus  atricauda  and  Sparisoma  cretense  based  on 
indicators  of  increased  biomass  and  abundance.  Only  one  non-indicator  species  showed 
indications of spillover - Mycteroperca fusca - occurring at two sites within the MPA but 20 km 
away from the fully protected area. Spillover effects are established with comparisons of metrics 
before  and  after  the  impact  of  MPA  establishment  from  sites  within  and  outside  the  protected 
area. In this case study potential spillover indications are limited to reference points largely within 

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the MPA boundary itself, each separated by a minimum of 12 km from the fully protected (integral) 
area. For S. cretense spillover effects were more associated with sites within 25 km of the fully 
protected area, largely within the MPA. Fewer comparisons could be made for  S. atricauda but 
still indicate spillover effects at 17 and 20 km to sites within the MPA. Given the size of La Graciosa 
(707 km2) it is questionable whether comparison between sites more than 50 km away is justified, 
particularly when the highest level of protection is afforded to such a small portion of the total 
MPA site. The data used for the assessment is of good quality, but updated abundance values and 
corresponding values of biomass would provide a more balance view of spillover effects. Assessing 
more species may illude to which confounding variables such as competition, were responsible for 
the variation between responses of species to spillover effects. 

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SUPPLEMENTARY INFORMATION 

Site 

Protection 
status 

Roque del Este 
norte 

Roque del Este 
norte 

Roque del Este sur 

Roque del Este sur 

Roque del Este 
Average 

Roque del Este 
Average 

Punta de la Mareta 

Punta de la Mareta 

Cuevas Coloradas 

Cuevas Coloradas 

Montaña Amarilla 

Montaña Amarilla 

Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 

Distance 
to 
Integral 
(Km) 
0 

0 

0 

0 

0 

0 

Trophic 
level 

Species 
group 

4.3   ±0.8 

Targeted 

4.3   ±0.8 

Targeted 

4.3   ±0.8 

Targeted 

4.3   ±0.8 

Targeted 

4.3   ±0.8 

Targeted 

4.3   ±0.8 

Targeted 

20 

4.3   ±0.8 

Targeted 

20 

4.3   ±0.8 

Targeted 

17.5 

4.3   ±0.8 

Targeted 

17.5 

4.3   ±0.8 

Targeted 

19 

4.3   ±0.8 

Targeted 

19 

4.3   ±0.8 

Targeted 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Mycteroperca 
fusca 

Species 

Year 

Abundance 

Biomass 

% Δ 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

1994 

0.5 

0.55 

34.00 

2005 

0.67 

0.52 

1994 

0.17 

0.41 

294.12 

2005 

0.67 

0.82 

1994 

0.67 

2005 

1.34 

- 

- 

1994 

0.33 

0.52 

2005 

4 

5.62 

100.00 

1112.12  MPA increased 
but ref site 
stronger 

Potentially 

1994 

0.5 

1.22 

-66.00 

2005 

0.17 

0.41 

1994 

1.33 

1.21 

-49.62 

Ref. site 
decreased, but 
MPA increased 
stronger 

Ref. site 
decreased, but 
MPA increased 
stronger 

No 

No 

2005 

0.67 

1.03 

250 

 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Site 

Protection 
status 

Punta Fariones 

Punta Fariones 

Mala 

Mala 

Veril de Puerto del 
Carmen 2 
Veril de Puerto del 
Carmen 2 
Roque del Este 
norte 

Roque del Este 
norte 

Roque del Este sur 

Roque del Este sur 

Roque del Este 
Average 

Roque del Este 
Average 

Punta de la Mareta 

Punta de la Mareta 

Cuevas Coloradas 

Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 

Distance 
to 
Integral 
(Km) 
12 

Trophic 
level 

Species 
group 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

4.3   ±0.8 

Targeted 

Mycteroperca 
fusca 

1994 

0.67 

0.82 

49.25 

Both 
increased, but 
MPA stronger 

Potentially 

12 

4.3   ±0.8 

Targeted 

21.5 

4.3   ±0.8 

Targeted 

21.5 

4.3   ±0.8 

Targeted 

50 

50 

0 

0 

0 

0 

0 

0 

4.3   ±0.8 

Targeted 

4.3   ±0.8 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

20 

2.9   ±0.27 

Targeted 

20 

2.9   ±0.27 

Targeted 

17.5 

2.9   ±0.27 

Targeted 

Mycteroperca 
fusca 

Mycteroperca 
fusca 
Mycteroperca 
fusca 
Mycteroperca 
fusca 
Mycteroperca 
fusca 
Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

2005 

1 

0.63 

1994 

0.33 

0.82 

0.00 

Stable 

No 

2005 

0.33 

0.52 

1994 

0.17 

0.41 

0.00 

Stable 

No 

2005 

0.17 

0.41 

1994 

7.33 

4.18 

209.28 

2005 

22.67 

8.21 

1994 

4.67 

1.97 

313.92 

2005 

19.33 

21.1 

1994 

12 

2005 

42 

250.00 

1994 

0.83 

1.6 

261.45 

Mutual 
increased 

Potentially 

2005 

3 

2.52 

1994 

1.5 

1.76 

251 

233.33 

Both 
increased, but 
MPA stronger 

Potentially 

 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Site 

Protection 
status 

Cuevas Coloradas 

Montaña Amarilla 

Montaña Amarilla 

Punta Fariones 

Punta Fariones 

Mala 

Mala 

Playa del Tío 
Joaquín 
Playa del Tío 
Joaquín 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 2 
Veril de Puerto del 
Carmen 2 
Punta Gorda 

Punta Gorda 

La Juradita 

La Juradita 

Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 

Distance 
to 
Integral 
(Km) 
17.5 

Trophic 
level 

Species 
group 

2.9   ±0.27 

Targeted 

19 

2.9   ±0.27 

Targeted 

19 

2.9   ±0.27 

Targeted 

12 

2.9   ±0.27 

Targeted 

12 

2.9   ±0.27 

Targeted 

21.5 

2.9   ±0.27 

Targeted 

22.5 

2.9   ±0.27 

Targeted 

24 

24 

50 

50 

50 

50 

58 

58 

62 

62 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

2005 

5 

9.38 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

1994 

1.5 

3.21 

2005 

4 

8.37 

166.67 

Both 
increased, but 
MPA stronger 

Potentially 

1994 

2 

2.53 

908.50 

2005 

20.17 

17.71 

1994 

0.83 

0.75 

221.69 

Potentially 

Both 
increased, but 
ref. site 
stronger 

Both 
increased, but 
MPA stronger 

Ref. site 
decreased, but 
MPA increased 
stronger 
Both 
increased, but 
MPA stronger 

Potentially 

No 

Potentially 

-91.50 

88.67 

-24.02 

23.88 

Ref. site 
decreased, but 
MPA increased 
stronger 
Both 
increased, but 
MPA stronger 

No 

Potentially 

2005 

2.67 

3.93 

1994 

2 

4.43 

2005 

0.17 

0.41 

1994 

1.5 

0.84 

2005 

2.83 

2.32 

1994 

2005 

0.17 

0.41 

1994 

4.83 

6.49 

2005 

3.67 

3.5 

1994 

0.67 

1.21 

2005 

0.83 

1.17 

252 

 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

2705.64 

1196.44 

-27.40 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

Site 

Protection 
status 

Roque del Este 
norte 

Roque del Este 
norte 

Roque del Este sur 

Roque del Este sur 

Roque del Este 
Average 

Roque del Este 
Average 

Punta de la Mareta 

Punta de la Mareta 

Cuevas Coloradas 

Cuevas Coloradas 

Montaña Amarilla 

Montaña Amarilla 

Punta Fariones 

Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 

Distance 
to 
Integral 
(Km) 
0 

0 

0 

0 

0 

0 

Trophic 
level 

Species 
group 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

20 

2.9   ±0.27 

Targeted 

20 

2.9   ±0.27 

Targeted 

17.5 

2.9   ±0.27 

Targeted 

17.5 

2.9   ±0.27 

Targeted 

19 

2.9   ±0.27 

Targeted 

19 

2.9   ±0.27 

Targeted 

12 

2.9   ±0.27 

Targeted 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

Sparisoma 
cretense 

1994 

2005 

1994 

2005 

1994 

2005 

1994 

2005 

1994 

2005 

1994 

2005 

1994 

253 

1964.42 

1413.55 

1924.33 

1499.09 

43.58 

2763.02 

3072.8 

4629.97 

- 

2.11 

4727.44 

- 

423.28 

849.69 

137.33 

1004.56 

1007.35 

Potentially 

Both 
increased, but 
ref. site 
stronger 

839.29 

1174.88 

62.91 

Potentially 

Both 
increased, but 
ref. site 
stronger 

1367.25 

3073.78 

778.54 

1602.82 

617.12 

1363.24 

-20.73  MPA increased, 
but ref. site 
decreased 
stronger 

No 

549.54 

922.73 

504.35 

Potentially 

Both 
increased, but 
ref. site 
stronger 

 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Species 

Year 

Abundance 

Biomass 

% Δ 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

3321.17 

2323.07 

Distance 
to 
Integral 
(Km) 
12 

Trophic 
level 

Species 
group 

2.9   ±0.27 

Targeted 

21.5 

2.9   ±0.27 

Targeted 

22.5 

2.9   ±0.27 

Targeted 

Sparisoma 
cretense 

Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sparisoma 
cretense 
Sarpa Salpa 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.9   ±0.27 

Targeted 

2.0   ±0.0 

Targeted 

2005 

1994 

2005 

1994 

2005 

1994 

2005 

1994 

2005 

1994 

2005 

1994 

2005 

Site 

Protection 
status 

Punta Fariones 

Mala 

Mala 

Playa del Tío 
Joaquín 
Playa del Tío 
Joaquín 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 2 
Veril de Puerto del 
Carmen 2 
Punta Gorda 

Punta Gorda 

La Juradita 

La Juradita 

Roque del Este 
norte 

Roque del Este 
norte 

Roque del Este sur 

Roque del Este sur 

Roque del Este 
Average 

Roque del Este 
Average 

Partial 
protected - 
exterior 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 

24 

24 

50 

50 

50 

50 

58 

58 

62 

62 

0 

0 

0 

0 

0 

0 

1994 

221.67 

206.92 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

10.33 

20.02 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

27.83 

39.94 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

221.67 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

38.16 

- 

- 

-82.79 

254 

849.32 

703.86 

884.81 

1939.79 

700.23 

1601.67 

0.5 

1.22 

992.34 

1057.79 

951.86 

605.82 

4.18 

Both 
increased, but 
ref. site 
stronger 
-99.93  MPA increased, 
but ref. site 
decreased 
stronger 
-4.08  MPA increased, 
but ref. site 
decreased 
stronger 

111.1 

272.13 

1442.34 

2599.78 

801.53 

658.95 

27.11 

48.54 

18.92 

24.39 

-44.43  MPA increased, 
but ref. site 
decreased 
stronger 
-30.21  MPA increased, 
but ref. site 
decreased 
stronger 

-95.34 

Potentially 

No 

No 

No 

No 

 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
Site 

Protection 
status 

Punta de la Mareta 

Punta de la Mareta 

Cuevas Coloradas 

Cuevas Coloradas 

Montaña Amarilla 

Montaña Amarilla 

Punta Fariones 

Punta Fariones 

Mala 

Mala 

Playa del Tío 
Joaquín 
Playa del Tío 
Joaquín 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 1 

Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Outside of 
reserve 
Outside of 
reserve 

Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 

Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Distance 
to 
Integral 
(Km) 
20 

Trophic 
level 

Species 
group 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

20 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

17.5 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

17.5 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

51.67 

126.56 

19 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

19 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

50 

122.47 

12 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

1 

2.45 

650.00 

12 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

7.5 

12.55 

21.5 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

0.17 

0.41 

22.5 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

42.17 

101.82 

24 

24 

50 

50 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

18.83 

46.13 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

1.5 

0.84 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

2.83 

2.32 

255 

MPA 
decreased, but 
ref. site 
increased 
stronger 

24705.9 

-100.00 

MPA 
decreased, but 
ref. site 
increased 
stronger 
Both 
decreased, but 
ref. site 
stronger 
88.67  MPA decreased 
as strong as 
ref. site 
increased 

No 

No 

No 

No 

 
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Trophic 
level 

Species 
group 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

0.17 

0.41 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2005 

2 

4.9 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

2.0   ±0.0 

Targeted 

Sarpa Salpa 

1994 

2005 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

0.33 

0.82 

454.55 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

1.83 

1.47 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

1 

1.1 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

0.33 

757.58 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

2.83 

Distance 
to 
Integral 
(Km) 
50 

50 

58 

58 

62 

62 

0 

0 

0 

0 

0 

0 

20 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

0.5 

0.55 

20 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

1.17 

0.75 

17.5 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

0.5 

0.55 

17.5 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

2.33 

0.52 

134.00 

Both 
increased, but 
MPA stronger 

Potentially 

366.00 

Both 
increased, but 
MPA stronger 

Potentially 

Site 

Protection 
status 

Veril de Puerto del 
Carmen 2 
Veril de Puerto del 
Carmen 2 
Punta Gorda 

Punta Gorda 

La Juradita 

La Juradita 

Roque del Este 
norte 

Roque del Este 
norte 

Roque del Este sur 

Roque del Este sur 

Roque del Este 
Average 

Roque del Este 
Average 

Punta de la Mareta 

Punta de la Mareta 

Cuevas Coloradas 

Cuevas Coloradas 

Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 

256 

 
  
  
  
  
 
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Site 

Protection 
status 

Montaña Amarilla 

Montaña Amarilla 

Punta Fariones 

Punta Fariones 

Mala 

Mala 

Playa del Tío 
Joaquín 
Playa del Tío 
Joaquín 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 2 
Veril de Puerto del 
Carmen 2 
Punta Gorda 

Punta Gorda 

La Juradita 

La Juradita 

Roque del Este 
norte -Biomass 

Roque del Este 
norte -Biomass 

Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 

24 

24 

50 

50 

50 

50 

58 

58 

62 

62 

0 

0 

Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Distance 
to 
Integral 
(Km) 
19 

Trophic 
level 

Species 
group 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

19 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

1.33 

0.52 

12 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

12 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

21.5 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

1.33 

1.75 

22.5 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

0.33 

0.52 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

0.17 

0.41 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

0.17 

0.41 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

0.33 

0.52 

-75.19 

Ref. site 
decreased, but 
MPA increased 
stronger 
0.00  MPA increased 

No 

No 

No 

Potentially 

No 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

0.33 

0.52 

-48.48 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

0.17 

0.41 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

0.17 

0.41 

194.12 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

0.5 

0.5 

0.55 

0.84 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

0.33 

0.52 

-34.00 

Ref. site 
decreased, but 
MPA increased 
stronger 
Both 
increased, but 
MPA stronger 

Ref. site 
decreased, but 
MPA increased 
stronger 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

64.53 

158.06 

586.73 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

443.15 

411.97 

257 

 
  
  
  
  
 
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Site 

Protection 
status 

Roque del Este sur 
- Biomass 

Roque del Este sur 
- Biomass 

Roque del Este 
Average - Biomass 

Roque del Este 
Average - Biomass 

Punta de la Mareta 
-Biomass 

Punta de la Mareta 
-Biomass 

Cuevas Coloradas 
-Biomass 

Cuevas Coloradas 
-Biomass 

Montaña Amarilla -
Biomass 

Montaña Amarilla -
Biomass 

Punta Fariones -
Biomass 

Punta Fariones -
Biomass 

Mala -Biomass 

Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Outside of 
reserve 

Distance 
to 
Integral 
(Km) 
0 

0 

0 

0 

Trophic 
level 

Species 
group 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

116.07 

154.32 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

64.53 

766.60 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

559.22 

20 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

91.75 

147.95 

23.71 

20 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

113.5 

144.03 

17.5 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

106.22 

142.14 

28.80 

17.5 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

136.81 

61.57 

19 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

19 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

126.84 

80.84 

12 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

20 

7.07 

-3.35 

12 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

19.33 

5.13 

21.5 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

41.09 

60.67 

-46.99 

Both 
increased, but 
MPA stronger 

Potentially 

Both 
increased, but 
MPA stronger 

Potentially 

Ref. site 
decreased, but 
MPA increased 
stronger 

Ref. site 
decreased, but 

No 

No 

258 

 
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Site 

Protection 
status 

Mala -Biomass 

Playa del Tío 
Joaquín -Biomass 
Playa del Tío 
Joaquín -Biomass 
Veril de Puerto del 
Carmen 1 -
Biomass 
Veril de Puerto del 
Carmen 1 -
Biomass 
Veril de Puerto del 
Carmen 2 -
Biomass 
Veril de Puerto del 
Carmen 2 -
Biomass 
Punta Gorda -
Biomass 
Punta Gorda -
Biomass 
La Juradita -
Biomass 
La Juradita -
Biomass 
Roque del Este 
norte 

Roque del Este 
norte 

Roque del Este sur 

Roque del Este sur 

Roque del Este 
Average 

Roque del Este 
Average 

Punta de la Mareta 

Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 

Outside of 
reserve 

Outside of 
reserve 

Outside of 
reserve 

Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Partial 
protected - 

Distance 
to 
Integral 
(Km) 
22.5 

24 

24 

50 

Trophic 
level 

Species 
group 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

21.78 

38.24 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

6.14 

15.05 

425.41 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

32.26 

79.03 

ΔMPA vs Δref 
Scenario 
name 

MPA increased 
stronger 
Both 
increased, but 
MPA stronger 

Spillover? 

Potentially 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

50 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

35.24 

77.9 

50 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

12.29 

19.04 

27.18 

50 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

15.63 

38.3 

58 

58 

62 

62 

0 

0 

0 

0 

0 

0 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

15.63 

38.3 

277.48 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

59 

77.24 

4.3   ±0.6 

Targeted 

Serranus atricauda 

1994 

9.44 

15.59 

407.42 

4.3   ±0.6 

Targeted 

Serranus atricauda 

2005 

47.9 

80.64 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

1.83 

2.86 

-90.71 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

0.17 

0.41 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

1 

2.45 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

1.83 

-36.07 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

1.17 

Both 
increased, but 
MPA stronger 

Potentially 

Both 
increased, but 
MPA stronger 

Both 
increased, but 
MPA stronger 

Potentially 

Potentially 

20 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

0.33 

0.52 

-48.48 

Both 
decreased, but 

No 

259 

 
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Site 

Protection 
status 

Distance 
to 
Integral 
(Km) 

Trophic 
level 

Species 
group 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

Punta de la Mareta 

Cuevas Coloradas 

Cuevas Coloradas 

Montaña Amarilla 

Montaña Amarilla 

Punta Fariones 

Punta Fariones 

Mala 

Mala 

Playa del Tío 
Joaquín 
Playa del Tío 
Joaquín 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 2 
Veril de Puerto del 
Carmen 2 

exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 

20 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

0.17 

0.41 

17.5 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

0.17 

0.41 

194.12 

17.5 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

0.5 

0.84 

19 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

1.17 

1.17 

70.94 

19 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

2 

2.19 

12 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

1.5 

1.22 

-66.67 

12 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

0.5 

1.22 

21.5 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

0.33 

0.52 

22.5 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

NA 

24 

24 

50 

50 

50 

50 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

1 

1.55 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

NA 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

0.17 

0.41 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

NA 

NA 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

11.83 

28.99 

260 

Spillover? 

No 

No 

No 

ΔMPA vs Δref 
Scenario 
name 

ref. site 
stronger 

MPA 
decreased, but 
ref. site 
increased 
stronger 

Ref. site 
increased, but 
MPA decreased 
stronger 

Both 
decreased, but 
ref. site 
stronger 

 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
 
  
  
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Distance 
to 
Integral 
(Km) 
58 

Trophic 
level 

Species 
group 

Species 

Year 

Abundance 

Biomass 

% Δ 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

0.33 

0.83 

-48.48 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

0.17 

0.41 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

1994 

0.67 

0.82 

3.4   ±0.1 

Bycatch 

Diplodus cervinus 

2005 

NA 

Spillover? 

No 

ΔMPA vs Δref 
Scenario 
name 

Both 
decreased, but 
ref. site 
stronger 

Site 

Protection 
status 

Punta Gorda 

Punta Gorda 

La Juradita 

La Juradita 

Roque del Este 
norte 

Roque del Este 
norte 

Roque del Este sur 

Roque del Este sur 

Roque del Este 
Average 

Roque del Este 
Average 

Punta de la Mareta 

Punta de la Mareta 

Cuevas Coloradas 

Cuevas Coloradas 

Montaña Amarilla 

Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Fully protected 
- Integral 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 

58 

62 

62 

0 

0 

0 

0 

0 

0 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

20 

3.4   ±0.1 

Bycatch 

20 

3.4   ±0.1 

Bycatch 

17.5 

3.4   ±0.1 

Bycatch 

17.5 

3.4   ±0.1 

Bycatch 

19 

3.4   ±0.1 

Bycatch 

Centrolabrus 
trutta 

1994 

261 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

1994 

30.67 

26.23 

-89.14 

2005 

3.33 

3.27 

1994 

26.83 

30.62 

-85.72 

2005 

3.83 

30.62 

1994 

57.5 

-87.55 

2005 

7.16 

1994 

2005 

1994 

9.17 

5.64 

-90.95 

Mutual 
decrease 

No 

2005 

0.83 

2.04 

 
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
Assessing spillover from marine protected areas to adjacent fisheries 
Annex 6 - Case Study Reports 

Site 

Protection 
status 

Montaña Amarilla 

Punta Fariones 

Punta Fariones 

Mala 

Mala 

Playa del Tío 
Joaquín 
Playa del Tío 
Joaquín 
Veril de Puerto del 
Carmen 1 

Veril de Puerto del 
Carmen 1 
Veril de Puerto del 
Carmen 2 
Veril de Puerto del 
Carmen 2 
Punta Gorda 

Punta Gorda 

La Juradita 

La Juradita 

Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Partial 
protected - 
exterior 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 

Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 
Outside of 
reserve 

Distance 
to 
Integral 
(Km) 
19 

Trophic 
level 

Species 
group 

3.4   ±0.1 

Bycatch 

12 

3.4   ±0.1 

Bycatch 

12 

3.4   ±0.1 

Bycatch 

21.5 

3.4   ±0.1 

Bycatch 

22.5 

3.4   ±0.1 

Bycatch 

24 

24 

50 

50 

50 

50 

58 

58 

62 

62 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

3.4   ±0.1 

Bycatch 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 

Centrolabrus 
trutta 
Centrolabrus 
trutta 
Centrolabrus 
trutta 
Centrolabrus 
trutta 
Centrolabrus 
trutta 

Centrolabrus 
trutta 
Centrolabrus 
trutta 
Centrolabrus 
trutta 
Centrolabrus 
trutta 
Centrolabrus 
trutta 
Centrolabrus 
trutta 
Centrolabrus 
trutta 

Species 

Year 

Abundance 

Biomass 

% Δ 

ΔMPA vs Δref 
Scenario 
name 

Spillover? 

Fish / 
100 m2 

se 

Fish / 
100 m2 

se 

2005 

0.17 

0.41 

1994 

0.17 

0.41 

0.00 

2005 

0.17 

0.41 

1994 

3.17 

5.46 

2005 

4 

6 

1994 

0.67 

1.63 

2005 

0.33 

0.82 

1994 

0.5 

0.84 

2005 

0.67 

1.03 

1994 

2005 

26.18 

-50.75 

34.00 

Ref. site 
increased, but 
MPA decreased 
stronger 
Both 
decreased, but 
MPA stronger 

Ref. site 
increased, but 
MPA decreased 
stronger 

Both 
decreased, but 
MPA stronger 

Both 
decreased, but 
ref. site 
stronger 

1994 

0.83 

2.04 

-79.52 

2005 

0.17 

0.41 

1994 

0.33 

0.52 

-100.00 

2005 

262 

No 

No 

No 

No 

No 

 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
 
 
 
Getting in touch with the EU 

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