Restoration of Native Oyster, Ostrea edulis, in South Wales: Options and Approaches

Restoration of Native Oyster, Ostrea edulis, in South Wales: Options and Approaches
Restoration of Native Oyster, Ostrea edulis,
                                             in South Wales: Options and Approaches

                                             A.P. Woolmer, M. Syvret & A. FitzGerald

                                                 CCW Contract Science Report No. 960




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Restoration of Native Oyster, Ostrea edulis, in South Wales: Options and Approaches
Report series:                CCW Contract Science Report
Report number:                No. 960
Publication date:             May 2011
Contract number:              253 MFG 10
Contractor:                   Dr Andrew Woolmer, Salacia Marine
Contract Manager:             Aethne Cooke
Title:                        Restoration of Native Oyster, Ostrea edulis, in South Wales:
                              Options and Approaches
Author(s):                    A.P. Woolmer, M. Syvret, A. FitzGerald
Series editor(s):             None
Restrictions:                 None


Distribution list (core):
CCW HQ Library, Bangor                         National Library of Wales
CCW North Region Library, Mold                 British Library
CCW North Region Library, Bangor               Welsh Assembly Government Library
CCW S&E Region Library, Cardiff                Joint Nature Conservation Committee Library
CCW S&E Region Library, Llandrindod            Scottish Natural Heritage Library
CCW West Region Library, Aberystwyth           Natural England Library

Distribution list (others):
Aethne Cooke, CCW                                 Colin Charman, CCW
Mike Camplin, CCW                                 Clare Eno, CCW
Anne Bunker, CCW                                  Graham Rees, WAG
Andrea Winterton, CCW                             Sue Burton, Pembrokeshire Marine SAC
Catherine Duigan, CCW                             Blaise Bullimore, Camarthen Bay & Estuaries
Lucy Kay, CCW                                     EMS
Rowland Sharp, CCW                                Bill Sanderson, Herriot-Watt University
Ziggy Otto, CCW                                   Tom Pickerell, Shellfish Association of Great
Rebecca Wright, CCW                               Britain
Kirsten Ramsay, CCW                               David Palmer, Cefas (Lowestoft)




Recommended citation for this volume:
Woolmer, A.P., Syvret, M. & FitzGerald A., 2011. Restoration of Native Oyster, Ostrea edulis,
in South Wales: Options and Approaches. CCW Contract Science Report No: 960, 93 pp.
Restoration of Native Oyster, Ostrea edulis, in South Wales: Options and Approaches
CCW Contract Science Report No. 960
CONTENTS
_
LIST OF FIGURES ......................................................................................................................iii
LIST OF TABLES......................................................................................................................... iv
CRYNODEB GWEITHREDOL .................................................................................................... v
EXECUTIVE SUMMARY ........................................................................................................... vii
1      Introduction ............................................................................................................................ 1
       1.1    The decline of Ostrea edulis in South Wales .............................................................. 1
       1.1.1 Restoration of Ostrea edulis habitats and populations ................................................ 1
       1.2    Aims and approaches .................................................................................................. 1
       1.3    Background ................................................................................................................. 2
       1.3.1 Factors implicated in the decline of Ostrea edulis populations .................................. 2
       1.3.2 Decline of Ostrea edulis supporting habitats .............................................................. 2
       1.3.3 Restoration of Ostrea edulis habitats and populations ................................................ 3
2      Methods ................................................................................................................................... 5
    2.1     Identification of broodstock restoration areas ........................................................... 5
       2.1.1 Data gathering and GIS ............................................................................................... 5
       2.1.2 Oyster bed mapping .................................................................................................... 5
       2.1.3 GIS analysis of physical environmental factors .......................................................... 5
    2.2       Review of operational practices. .................................................................................. 5
3      Results ..................................................................................................................................... 6
    3.1     Identification of broodstock restoration areas ........................................................... 6
       3.1.1 Existing and historical O. edulis distribution and locations of O. edulis beds. ........... 6
       3.1.2 GIS analysis of physical environmental factors ........................................................ 16
       3.1.3 Hydrographic and behaviour barriers to connectivity ............................................... 18
       3.1.4 Anthropogenic impacts on restocked bed and other constraints ............................... 19
    3.2     Operational practices. ................................................................................................. 26
       3.2.1 Cultch material and its management for oyster habitat restoration ........................... 26
       1.1.1 Operations normally exempt from Food and Environment Protection Act 1985
       (FEPA) license control .......................................................................................................... 29
       3.2.2 Creation of oyster reefs and banks ............................................................................ 30
       3.2.3 Cultch Management .................................................................................................. 30
       3.2.4 Pest management ....................................................................................................... 32
       3.2.5 Disease (Bonamia ostreae) management .................................................................. 36
    3.3     Sourcing of broodstock for native oyster restoration efforts .................................. 39
       3.3.1 Genetic diversity & biosecurity................................................................................. 39
       3.3.2 Sourcing options for broodstock ............................................................................... 40
       3.3.3 Relative advantages & disadvantages of broodstock sourcing options ..................... 45
       3.3.4 Summary & conclusions ........................................................................................... 46
    3.4     Harvest methods .......................................................................................................... 48
       3.4.1 Dredge fisheries (Hand hauled light dredges) ........................................................... 48
       3.4.2 Dredge fisheries (Heavy dredges) ............................................................................. 49
       3.4.3 Note on dredge development..................................................................................... 50
       3.4.4 Handgathering ........................................................................................................... 50
       3.4.5 Oyster tongs............................................................................................................... 50
       3.4.6 Diving for oysters ...................................................................................................... 51

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CCW Contract Science Report No. 960
       3.4.7 Impacts of harvest methods on Ostrea edulis habitats .............................................. 51
       3.4.8 The economic viability and minimum stock densities of alternative harvest ........... 53
    3.5     Improved fishery management as a means of O. edulis restoration. ...................... 58
       3.5.1 Current management ................................................................................................. 58
       3.5.2 Options for improved management regulations or voluntary measures ................... 58
    3.6     Options for Ostrea edulis restoration in South Wales .............................................. 65
       3.6.1 Option 1. Habitat restoration, broodstock concentration, and improved fishery
       management. ......................................................................................................................... 65
       3.6.2 Option 2. Promotion of ostreae resistance through broodstock concentration, habitat
       restoration through Crepidula fornicata control and improved fishery management. ......... 68
       3.6.3 Option 3. Habitat restoration, broodstock concentration, establishing population
       connectivity and improved fishery management .................................................................. 72
    3.7     Outline costings for the restoration of O. edulis in South Wales ............................ 76
       3.7.1 Construction of broodstock area/oyster bank ............................................................ 76
       3.7.2 Habitat restoration – C. fornicata control ................................................................. 76
       3.7.3 Restocking of a broodstock area or oyster bank ....................................................... 77
       3.7.4 Stock assessment of wild stocks................................................................................ 77
       3.7.5 Pest management ....................................................................................................... 77
       3.7.6 Project management and related tasks ...................................................................... 78
4      Discussion ............................................................................................................................. 79
       4.1.1 Recommended sites for O. edulis restoration............................................................ 79
       4.1.2 Recommended approaches for broodstock site restoration ....................................... 80
       4.1.3 The importance of fishery management .................................................................... 81
5      Acknowledgements ............................................................................................................... 82
6      References ............................................................................................................................. 83
Appendix 1: Data archive appendix ............................................................................................ 88




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CCW Contract Science Report No. 960
LIST OF FIGURES

Figure 1. Location of existing and historically recorded O. edulis beds and distribution in South
Wales. ............................................................................................................................................ 10
Figure 2. Location of existing and historically recorded O. edulis beds and distribution in the
Milford Haven waterway. .............................................................................................................. 11
Figure 3. Location of existing and historically recorded O. edulis beds and distribution along the
south Pembrokeshire coast............................................................................................................ 12
Figure 4. Location of existing and historically recorded O. edulis beds and distribution along the
Gower coast and offshore. ............................................................................................................ 13
Figure 5. Location of existing and historically recorded O. edulis beds and distribution in
Swansea Bay. ................................................................................................................................. 14
Figure 6. Location of existing and historically recorded O. edulis beds and distribution off
Porthcawl. ..................................................................................................................................... 15
Figure 7. An example of a chain harrow used to remove silt from oyster beds and to expose
cultch material for settlement (after Cole, 1956) .......................................................................... 31
Figure 8. Native oyster larval rearing pond shown with a butyl liner. (© Martin Syvret) ........... 43
Figure 9. Native Oyster Nursery System under construction (© Martin Syvret) ......................... 43
Figure 10. A traditional light hand hauled dredge used in the Fal & Helford oyster fishery. .... 48
Figure 11. Oyster dredges used in the Chichester Harbour and Solent oyster fisheries. . .......... 49
Figure 13b Patent tongs being recovered. © Maryland Watermans Assoc. ................................. 50
Figure 13a.Typical oyster tongs used in Crassostrea virginica fisheries in the USA .................. 50
Figure 14. Simplified model of landing value (price at 1st sale) achievable by method in relation
to oyster stock density.. ................................................................................................................. 54




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LIST OF TABLES

Table 1. Supporting information for mapping exercise of existing and historical O. edulis beds
distribution along the South Wales coast. ....................................................................................... 7
Table 2. Predicted tidal residuals data (m-s) at historical and existing O. edulis beds ................ 16
Table 3. Predicted tidal ebb current data (m-s) at historical and existing O. edulis beds ............ 17
Table 4. Depths (m) below CD at historical and existing subtidal O. edulis beds. ..................... 17
Table 5. Wave heights (m) historical and existing subtidal O. edulis beds (insufficient data
coverage). ...................................................................................................................................... 18
Table 6. Review of potential anthropogenic threats and constraining factors to restored O. edulis
broodstock areas. .......................................................................................................................... 21
Table 7. Estimates of volumes and tonnages of shell material required for different areas of
habitat restoration. ........................................................................................................................ 27
Table 8. Molluscan shell waste (cultch) quantities produced by UK shellfish processing industry
(adapted from FitzGerald, 2007) .................................................................................................. 28
Table 9. Relative advantages and disadvantages of different broodstock sourcing options ........ 45
Table 10. Minimum O. edulis densities required for economic viability of alternative harvest
methods.......................................................................................................................................... 54
Table 11. Factors and values used in hand hauled dredge economic model ................................ 55
Table 12. Analysis of stock and market conditions required to make the use of light dredges
economically viable based ............................................................................................................ 55
Table 13. Factors and values used in heavy dredge economic model .......................................... 56
Table 14. Analysis of stock and market conditions required to make the use heavy dredges
economically viable ....................................................................................................................... 56
Table 15. Factors and values used in diver gathering economic model ...................................... 57
Table 16.Analysis of stock and market conditions required to make diver collection economically
viable ............................................................................................................................................. 57
Table 17. Current WAG Statutory Instruments (translated from SWSFC Byelaws) pertaining to
the O. edulis fishery. ...................................................................................................................... 60
Table 18. Options for enhanced management measures and operational best practice of O.
edulis fisheries in South Wales.. .................................................................................................... 61
Table 19. Determining factors for the choice of Swansea Bay and adjacent area for Option 1
restoration. .................................................................................................................................... 65
Table 20. A simplified Gantt chart describing the key organisational and operational stages
involved in the initial O. edulis restoration process for Option 1................................................. 66
Table 21. Determining and constraining factors in Milford Haven influencing Option 2
restoration. .................................................................................................................................... 68
Table 22. A simplified Gantt chart describing the key organisational and operational stages
involved in the initial O. edulis restoration process for Option 2................................................. 69
Table 23 Determining factors for the choice of sites for Option 3 restoration. ............................ 72
Table 24. A simplified Gantt chart describing the key organisational and operational stages
involved in the initial O. edulis restoration process for Option 3................................................. 73
Table 25. Costs involved in the sourcing of shell cultch, transport and construction of oyster
banks and restoration of oyster beds............................................................................................. 76
Table 26. Costs involved in restoration of O. edulis habitat infested with C. fornicata. .............. 76
Table 27. Costs involved in the sourcing local broodstock for relaying in broodstock areas. .... 77
Table 28. Costs involved in undertaking a stock assessment by fishery biologists using a local
fishing vessel as a sampling platform. .......................................................................................... 77
Table 29. Costs involved in undertaking pest management using local fishing vessels. ............. 77
Table 30. Costs involved in project management and related tasks. ........................................... 78


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CCW Contract Science Report No. 960
CRYNODEB GWEITHREDOL

Gwelwyd poblogaethau wystrys brodorol ledled Ewrop yn dirywio‘n ddifrifol ddiwedd y 19eg
ganrif a dechrau‘r 20fed ganrif, yn bennaf oherwydd gorbysgota a‘r colli cynefin a oedd yn
gysylltiedig â hynny, ond a waethygwyd hefyd gan bwysau anthropogenig ac amgylcheddol a
achoswyd gan lygredd, afiechyd a chyfres o aeafau oer. Mae adroddiadau hanesyddol yn nodi
bod Ostrea edulis yn ganolog i bysgodfeydd lleol pwysig yn Ne Cymru yn ôl yn ystod y cyfnod
pan gafodd Prydain ei goresgyn gan y Rhufeiniaid, ac maent yn disgrifio pysgodfa a oedd yn
cynnal 200 o gychod a ddeuai â thros 9 miliwn o wystrys i‘r lan pan oedd y diwydiant yn ei
anterth yn y 19eg ganrif.
Mae Ostrea edulis i‘w gweld ar amrywiaeth eang o gynefinoedd cadarn a sefydlog ar wely‘r
môr, lle ceir arwynebau caled a glân lle gall larfâu ymsefydlu, ond mae‘n debygol bod ffurfiau
mwy cymhleth ar gynefinoedd wedi bodoli yn y gorffennol, a oedd yn cynnwys riffiau a
phonciau wystrys. Cafodd ponciau wystrys eang eu disgrifio ym Môr y Gogledd ac o amgylch
arfordiroedd Cymru a Lloegr gan Olsen (1886), ac er na sonnir o gwbl am riffiau neu bonciau O.
edulis byw mawr yng Nghymru, mae adroddiadau anecdotaidd gan y diwydiant pysgota yn nodi
bod llawer iawn o gregyn wystrys marw wedi‘u dyddodi oddi ar arfordir gogledd Sir Benfro a
Phenrhyn Llŷn.
Mae poblogaethau O. edulis sydd wedi goroesi yn bodoli ym Mae Abertawe a dyfrffordd
Aberdaugleddau. Ar hyn o bryd mae‘r poblogaethau hyn sy‘n weddill yn dioddef llawer o
bwysau anthropogenig ac amgylcheddol sy‘n bygwth eu hyfywedd, ac mae‘r pwysau hwnnw‘n
dod o gyfeiriad pysgodfeydd wystrys masnachol, gweithredoedd porthladdoedd, rhywogaethau
estron goresgynnol (Crepidula fornicata) ac afiechyd (Bonamia ostreae).
Nod yr astudiaeth hon oedd nodi‘r cyfleoedd i adfer poblogaethau a chynefinoedd y wystrysen
frodorol yn Ne Cymru, a nodi dulliau posibl o wneud hynny. Mae‘r adroddiad yn disgrifio‘r
opsiynau ar gyfer dulliau ymarferol o adfer y wystrysen frodorol Ostrea edulis yn ei chynefin
naturiol yn Ne Cymru, er mwyn bodloni targedau Cynllun Gweithredu Bioamrywiaeth Cymru
a‘r DU ar gyfer ei hadfer.
Cafodd adolygiad o‘r ffactorau biolegol ac ecolegol sy‘n ofynnol i hybu a chynnal poblogaethau
iach o‘r wystrysen frodorol ei gynnal a‘i ddefnyddio i nodi safleoedd a fyddai‘n addas ar gyfer
ailgyflwyno cynefin y wystrysen frodorol a sefydlu ardaloedd stoc magu ar hyd arfordir De
Cymru. Roedd yr adolygiad yn cynnwys ymarfer mapio a oedd yn disgrifio lleoliad a hyd a lled
lleoliadau presennol a hanesyddol gwelyau‘r wystrysen frodorol yn Ne Cymru. Cafodd y gwaith
hwn ei lywio gan adolygiad o ddogfennau hanesyddol, cofnodion cyfredol, a gwaith ymgynghori
â physgotwyr lleol.
Datgelodd dadansoddiad System Wybodaeth Ddaearyddol o ffactorau amgylcheddol ffisegol y
caiff gwelyau‘r wystrysen frodorol eu dosbarthu mewn ardaloedd sy‘n cael eu cysgodi rhag
symudiadau tonnau, sy‘n teimlo effaith cerhyntau llanw cymedrol (1-2 kts) ond sydd â lefel isel
iawn o symudiadau gweddillol net y llanw (< 0.1-ms). Awgrymir bod rhwystr hydrograffig, a
achosir gan gerhyntau a gynhyrchir gan y llanw a‘r gwynt ym Môr Hafren, yn atal cysylltedd
rhwng poblogaethau sy‘n weddill.
Nodwyd dylanwadau a chyfyngiadau anthropogenig a allai effeithio ar waith ailgyflwyno
cynefin y wystrysen frodorol ac adfer ardaloedd stoc magu. Cyflwynir dulliau deddfwriaethol ac
ymarferol perthnasol o fynd i‘r afael â‘r bygythiadau hyn.
Nodwyd y gallai pysgodfeydd O. edulis masnachol effeithio ar waith adfer poblogaethau‘r
wystrysen frodorol. Caiff opsiynau ar gyfer dulliau diwygiedig o reoli pysgodfeydd, sy‘n hybu‘r
gwaith o adfer poblogaethau‘r wystrysen frodorol, eu cynnig gan gynnwys camau i bennu
Uchafsymiau Glanio ac ardaloedd gwirfoddol ar gyfer stoc magu. Caiff dadansoddiad

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CCW Contract Science Report No. 960
economaidd ei gyflwyno, sy‘n tynnu sylw at hyfywedd economaidd dulliau cynaeafu sy‘n fwy
cynaliadwy o safbwynt amgylcheddol, megis defnyddio cribiniau ysgafn a defnyddio plymwyr i
gasglu wystrys.
Cafodd dulliau gweithredol o adfer a rheoli gwelyau wystrys eu hadolygu a‘u trafod. Mae‘r
dulliau hynny‘n cynnwys gofyn i‘r diwydiant prosesu pysgod cregyn am gregyn glân (gwalfa) ar
gyfer gwaith adfer, a defnyddio dulliau ymarferol o gael gwared â C. fornicata a‘u rheoli.
Tynnodd adolygiad o ffynonellau posibl o stoc magu O. Edulis, at ddiben gwaith adfer ardaloedd
sydd wedi‘u diboblogi, sylw at y risg o ran bioddiogelwch a achosir gan Bonamia exitiosa, sef
afiechyd parasitig newydd a geir mewn rhai poblogaethau o‘r wystrysen frodorol.
Argymhellwyd y dylid defnyddio poblogaethau lleol nes deellir yn llawn beth yw hyd a lled yr
afiechyd hwn, a thrafodwyd y posibilrwydd o ddefnyddio silod o silfeydd.
Caiff cyfres o ddulliau gweithredu posibl eu cyflwyno, sydd wedi‘u teilwra i safleoedd penodol
ym Mae Abertawe a dyfrffordd Aberdaugleddau. Mae‘r rhain yn cynnwys camau megis adfer
cynefin drwy lunio ponciau wystrys, a chael gwared â C. fornicata, sefydlu ardaloedd ar gyfer
stoc magu, a diwygio dulliau o reoli pysgodfeydd mewn partneriaeth â rhanddeiliaid
pysgodfeydd lleol. Caiff costau dangosol eu cyflwyno‘n fodwlar ar gyfer gweithredoedd unigol,
megis y rhai sy‘n ymwneud â dod o hyd i walfa, cludo a dyddodi. Bydd y dull gweithredu hwn
yn hwyluso‘r gwaith o ddatblygu prosiectau adfer y wystrysen frodorol yn y dyfodol.




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EXECUTIVE SUMMARY
Native oyster populations throughout Europe suffered a serious decline in the late 19th and early
20th centuries due predominantly to over fishing and associated habitat loss, but exacerbated by
anthropogenic and environmental pressures of pollution, disease and a series of cold winters.
Historic accounts place Ostrea edulis at the centre of important local fisheries in South Wales
back to the Roman occupation of Britain and describe a fishery supporting 200 vessels landing
over 9 million oysters at its peak in the 19th century.
Ostrea edulis are found on a wide variety of firm and stable seabed habitats where clean hard
surfaces exist for larval settlement but it is likely that more complex habitat forms have
historically existed including oyster banks and reefs. Extensive oyster banks were described in
the North Sea and around the coasts of England and Wales by Olsen (1886) and, although no
accounts of large living O. edulis banks or reefs are reported in Wales, anecdotal reports from
the fishing industry place large deposits of dead oyster shell off of the north Pembrokeshire coast
and Llyn Peninsular.
Surviving O. edulis populations exist in Swansea Bay and the Milford Haven waterway. These
relic populations are currently subject to a number of anthropogenic and environmental pressures
that threaten their viability including commercial oyster fisheries, port operations, invasive non-
native species (Crepidula fornicata) and disease (Bonamia ostreae).
The aim of this study was to identify the scope and potential approaches for restoration of native
oyster populations and habitats in South Wales. The report describes the options for practical
approaches for restoration of the native oyster Ostrea edulis in its natural habitat in South Wales
to meet UK and Welsh BAP targets for recovery.
A review of the biological and ecological factors required to promote and maintain healthy
native oyster populations was undertaken and used to identify sites suitable for native oyster
habitat reinstatement and the establishment of broodstock areas along the South Wales coast.
The review included a mapping exercise describing the location and extent of current and
historical locations of native oyster beds in South Wales. This was informed by a review of
historical documents, existing records and consultation with local fishermen.
A GIS analysis of physical environmental factors revealed that native oyster beds are distributed
in areas sheltered from wave action, subject to moderate tidal currents (1-2 kts) but with a very
low net residual tidal movement (< 0.1-ms). A hydrographic barrier to connectivity between relic
populations posed by tidal and wind generated currents in the Bristol Channel is suggested.
Anthropogenic impacts and constraints that may affect native oyster habitat reinstatement and
restored broodstock areas were identified. Relevant legislative and practical approaches
addressing these threats are presented.
Commercial O. edulis fisheries were identified as having the potential to affect the restoration of
native oyster populations. Options for revised fisheries management that promote the restoration
of native oyster populations are proposed including the establishment of Maximum Landing
Sizes and voluntary broodstock areas. An economic analysis is presented that highlights the
economic viability of more environmentally sustainable harvest methods such as light weight
dredges and diver collection.
Operational methods for oyster bed restoration and management were reviewed and discussed.
These include the sourcing of clean shell material (cultch) for habitat restoration from the
shellfish processing industry and practical approaches of C. fornicata removal and control.
A review of potential sources for O. edulis broodstock for restoration of depopulated areas
highlighted the biosecurity risk posed by Bonamia exitiosa, a newly identified parasitic disease
found in some native oyster populations. Until the extent of this disease is fully understood,


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sourcing from local populations was recommended and the option of hatchery sourced spat
discussed.
A series of potential approaches are presented tailored to specific sites in Swansea Bay and the
Milford Haven waterway. These include such measures as habitat restoration by construction of
oyster banks and removal of C. fornicata, establishment of broodstock areas and a revision of
fishery management in partnership with local fishery stakeholders. Indicative costs are presented
in a modular manner for individual operations such as cultch sourcing, transport and deposition.
This approach will facilitate the development of future native oyster restoration projects.




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1 INTRODUCTION
1.1 The decline of Ostrea edulis in South Wales
Historically the native or flat oyster Ostrea edulis formed extensive beds, shell banks and formed
cohesive shell reefs around the European coasts. Olsen, (1886) describes large oyster banks in
the North Sea and around coasts of England and Wales.
The wild fishery for O. edulis was the basis of an important shellfish industry in South Wales;
records date commercial fisheries at Mumbles and Oystermouth stretching back to Roman times.
The Duke of Beaufort described the oyster beds at Oystermouth as the most prolific in Britain in
1684 (Baker, 1864). These fisheries were supplied with wild stock from beds along the Gower
coast, around Tenby and Caldey Island, and off Stackpole Head. Owen‘s 1603 ―Description of
Pembrokeshire‖ presents detailed accounts of extensive oyster beds and associated fisheries
occurring in the Milford Haven waterway. In the late 19th century the local oyster fishery
employed many hundreds of people, supported 200 vessels landing over 9 million oysters many
of which were transported to the London markets and beyond to the continent.

1.1.1 Restoration of Ostrea edulis habitats and populations
Large scale oyster habitat and population restoration projects have been undertaken in the USA
for C. virginica. These initiatives have included a number of approaches including the formation
of extensive artificial reefs, the establishment of broodstock sanctuaries and community
involvement in ‗oyster gardening‘ (Brumbaugh et al., 2006).
Attempts of O. edulis restoration in the UK are in their initial stages. A number of attempts have
been made to restore habitat and regenerate stocks at sites in Strangford Lough, the Solent and
Chichester Harbour. Initial results in some areas have been promising indicating increases in O.
edulis densities (Roberts et al., 2005). Unfortunately the long-term success of some of these
projects have been affected by disease and unregulated fishing activity.

1.2 Aims and approaches
The aim of this study is to identify the scope and potential approaches for restoration of the
native oyster in South Wales. The report attempts to describe the options for practical
approaches for restoration of the native oyster Ostrea edulis in its natural habitat in South Wales
to meet UK and Welsh BAP targets for recovery.
The study has focused on 5 key subject areas:
    The identification of areas for the laying of broodstock in the wild (for larval supply
     to a wider area and self-recruitment)
    Anthropogenic impacts and threats to restocked beds
    Harvesting methods
    Sourcing of broodstock
    Operational practices
From these it was possible to describe a series of costed options for future restoration projects.
This study drew upon a wide range of existent information in primary and grey literature. The
authors were assisted by members of the Shellfish Association of Great Britain whose members
collectively hold a great deal of practical experience operating oyster cultivation businesses,
fisheries and hatcheries. Members of the South West Wales Fishing Communities Ltd., a local
fisherman‘s association, and independent local oyster fishermen provided valuable insights into


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current and historical locations of O. edulis beds in South Wales and provided some valuable
insights into operational practices and suggestions for future management.

1.3 Background

1.3.1 Factors implicated in the decline of Ostrea edulis populations
Native oyster populations throughout Europe suffered a serious decline in late 19th and early 20th
centuries due to over fishing and associated habitat loss, combined with the environmental and
anthropogenic pressures of pollution and disease. Although subject to exploitation for many
centuries, the boom in popularity of oysters after the Napolionic Wars in the early 18th Century,
assisted by improved communications brought about by railways, subjected wild O. edulis
populations to increasingly unsustainable exploitation. This boom peaked between 1850-1860
with estimates of 500 million oysters being sold through Billingsgate alone (Mayhew, 1851 in
Neild, 1995). An estimate for oyster production in 1866 of 40 million oysters illustrates the
rapidity of the collapse of the populations. Wright (1923) describes a ‗depletion‘ of the O. edulis
population along the South Wales coast and attributed this to a combination of over fishing,
paucity of recruitment and disease. An unidentified disease was thought to be responsible for
mass mortalities in practically all European oyster population including those in England and
Wales in 1920 and 1921 (Orton, 1923; Cole 1954).
More recently the introduction of the parasitic haplosporidian Bonamia ostreae has caused high
levels of mortality in wild and cultivated populations across Europe. Mortality tends to be
highest in 2-3 year old oysters and is associated with stress. Transmission between individuals is
thought to be density dependent necessitating close proximity for infection to take place;
stocking densities are carefully monitored in cultivated beds and farm operations.       Bonamia
ostreae was found in Milford Haven by Cefas in 2006. Shellfish movements from infected areas
are thought to be the main vector of B. ostreae and there is no short-term solution for infected
populations. Other non-native pest species affecting the viability of O. edulis populations are the
slipper limpet Crepidula fornicata and the American whelk tingle Urosalpinx cinerea.
Crepidula fornicata competes with O. edulis for both space and food and have no natural
predator in the UK which results in their occurrence in very high densities at some sites. In high
densities C. fornicata is able to modify the underlying habitat by rapid deposition of pseudo
faeces which forms a cohesive mud that inhibits O. edulis larval settlement and smothers the
living oysters. Crepidula fornicata is present in Milford Haven and Swansea Bay. Urosalpinx
cinerea can occur in high densities on infested beds and is reported to be responsible for heavy
mortalities of young O. edulis in the Essex rivers and north Kent oyster beds but is not recorded
in Wales (Cole, 1942; Hancock, 1954; Hancock, 1969).

1.3.2 Decline of Ostrea edulis supporting habitats
Ostrea edulis are currently found on a wide variety of firm and stable habitats where clean hard
surfaces exist for larval settlement. These vary from high density oyster beds with underlying
substrata of dead shell and gravel to muddy sand with occasional shell and gravel where oysters
occur in low numbers.
It is well established that mobile fishing gears change the physical nature of seabed habitats and
influence the structure and function of the associated benthic communities (Dayton et al., 1995;
Jennings and Kaiser, 1998; Watling and Norse, 1998). The use of heavy oyster dredges and the
incidental use of other mobile gears are widely acknowledged to have had devastating effects on
oyster reefs in the USA (deAlteris, 1988; Rotheschild et al., 1994; Lenihan and Peterson, 1998).
The action of gears on these banks and reef acts to reduce their height and redistribute the oyster
shells over a wider area. A recent study reported that dredging over a reinstated American oyster
(Crassostrea virginica) bank reduced its height by 30% in a single season
(Lenihan & Peterson, 2004).

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There are no current records supporting the existence of O. edulis reefs or relic reef fragments.
Accounts of oyster reef habitat degradation on the scale reported in the USA has not been
reported in Europe, this may be due to the fact that such habitats have been exploited for much
longer periods rather than a single century. Olsen (1886) describes oyster banks and oyster beds
around European coasts and contemporary accounts of the time describe oysters as living or
being fished from banks, beds or grounds. It is likely that reefs or substantial banks, where they
existed, were modified many hundreds of years ago by the long-term action of sail and hand-
hauled dredges. There is some evidence of significant habitat modification on more recent
times; the extensive oyster banks that existed in the North Sea and which gave rise to areas such
as the Central Oyster Grounds and Dutch Oyster Grounds no longer exist and have been replaced
by muddy sediments. No accounts of large living O. edulis banks or reefs are known to exist in
Wales but anecdotal reports from the fishing industry suggest large deposits of dead oyster shell
off of the north Pembrokeshire coast and off the Llyn Peninsular (pers. comm. Sean Ryan, Welsh
Seafoods).
Ostrea edulis exhibits a series of behavioural and functional adaptations that promote spawning
aggregations may also function to promote reef building. Larval dispersal in O. edulis is not
wholly dictated by the wind and tides but also by the behaviour of the individual larvae which
display vertical migrations in the water column that can influence their ultimate settlement site.
In addition to their ability to select suitable settlement surfaces, larvae have been reported to
exhibit chemically mediated gregarious behaviours during settlement that favours their
settlement with conspecifics (Walne, 1974; Bonar et al, 1990; Morse, 1990; Pawlik, 1992;
Zimmerfaust, 1994). Walne (1974) describes extensive settlement of larvae on older individuals
and as O. edulis larvae concrete a single time it is presumed that this behaviour does not confer a
selective disadvantage. These behaviours are common in other marine invertebrates where they
promote spawning aggregations and reduce the risk of Allee effects of a widely dispersed
population (Allee et al. 1949; Gascoigne & Lipcius, 2004).
Reef building may enable populations to avoid the risk of siltation in muddy estuarine
environments where elevation into the water column increases current flow over the surface of
the bank or reef. The location of the Central Oyster Grounds in the North Sea is in a
depositional area of low tidal energy which is now characterised by muddy sediments; clearly
the elevated banks conferred some refuge against smothering. Settlement with dense
aggregations of conspecifics may provide a refuge from predation during early growth stages;
observations on Modiolus modiolus reefs have recorded juveniles settled amongst the reef matrix
and unavailable to predators (pers. comm. Bill Sanderson, Herriot-Watt University).
The formation of banks and reefs may not be reliant solely on larval recruitment and may form in
high energy environments as simple aggregations of O. edulis through the downstream
movement and sorting of individuals by tidal currents and wave action. The large tidal range and
associated currents in the Bristol Channel may have been instrumental in the formation of
offshore beds and banks reported by Wright (1928, 1932).
The natural formation of oyster reefs and banks is a long-term process reliant of the successive
recruitment of many generations (Lenihan & Peterson, 2004). Existing wild populations of O.
edulis now exist on a variety of habitats and associated fisheries associate oysters with oyster
beds, areas of shell material distributed over relatively wide areas of seabed and estuaries
reflecting the long-term decline in more complex or elevated reef habitats. Many cultivated
oyster beds require regular deposition of cultch material and management to prevent siltation and
to manage C. fornicata numbers in order for O. edulis to thrive.

1.3.3 Restoration of Ostrea edulis habitats and populations
 Large scale oyster habitat and population restoration projects have been undertaken in the USA
for C. virginica. These initiatives have included a number of approaches including the formation

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of extensive artificial reefs, the establishment of broodstock sanctuaries and community
involvement in ‗oyster gardening‘ (Brumbaugh et al., 2006).
Attempts of O. edulis restoration in the UK are at their initial stages. A project to restore habitat
and regenerate stocks in Strangford Lough carried out extensive cultch deposition and reseeded
these areas with seed and broodstock oysters. Initial results were promising with an increase in
inter-tidal O. edulis densities (Roberts et al., 2005). Unfortunately the project period was short-
lived and subsequent surveys have reported a decline in O. edulis numbers which has been
attributed to unregulated fishing activity.
An industry led restoration project was undertaken in the Solent in the Stanswood Bay Several
Order where cultch and broodstock oysters were deposited in order to increase the larval supply
to the surrounding areas. This attempt was affected by a series of factors including disease and
habitat changes.
A partnership approach between the fishing industry, conservation and fishery managers has
been adopted in the restoration of a commercial fishery in Chichester Harbour. The Chichester
Harbour Oyster Partnership Initiative (CHOPI) aims to establish a series of broodstock areas at
designated site within the harbour. Broodstock oysters are obtained from local stocks through a
‗buy-back buy-in‘ scheme where fishermen donate a bag of oysters for each one purchased for
the project. Initial reports are promising with 1,964 kg of O. edulis re-laid in 3 days at the
beginning of November 2010 (pers. comm., Belinda Vause Sussex SFC). In addition to re-
laying broodstock CHOPI partners are to undertake dredging to remove C. fornicata which
occurs in large densities on traditional oyster beds, this will be undertaken cost free by fishermen
in early summer prior to O. edulis larval settlement. A similar approach has been proposed to
take place in the Fal oyster fishery in Cornwall.




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2 METHODS
2.1 Identification of broodstock restoration areas
2.1.1   Data gathering and GIS
A review of the biological and ecological factors required to promote and maintain healthy
native oyster populations was undertaken in order to identify sites suitable for native oyster
habitat reinstatement and the establishment of broodstock areas. This information was compiled
and tabulated drawing upon key reference works and specifically those that present this
information in a UK context (Table 1). A series of physical environmental factors were
identified and optimum conditions were either identified or where these were not reported, a
range of conditions were suggested. Anthropogenic activities may affect the success of future
restoration projects and therefore a review of likely impacts was undertaken. Where available,
spatial data was imported into a MapInfo GIS for analysis.
2.1.2   Oyster bed mapping
Mapping of historical and existing O. edulis beds and distribution drew upon a wide range of
information sources including survey reports, historical accounts, data from the National
Biodiversity Network database and local knowledge of commercial fishermen. The latter,
produced using a rapid mapping approach developed by Woolmer (2009 a), proved to be the
most extensive with information being provided for a variety of un-surveyed sites. Historical
information was provided by historical accounts, local knowledge and Wright‘s 1923 and 1932
reports and note books, which when produced in the early 20th century, drew upon fishermen‘s
local knowledge from the late 1800‘s (Wright, 1923; 1932). The locations of O. edulis beds and
the distribution of O. edulis was plotted in MapInfo, each record was annotated with a
description of the bed or area and referenced with the source of information. An assessment of
locational confidence was also made.
2.1.3   GIS analysis of physical environmental factors
The objective of the analysis was to identify common environmental factors at sites of historical
and existing O. edulis beds by drilling down through the available datasets. The outputs of this
analysis could then be utilized to identify unreported areas. The analysis focused on the
hydrodynamic environmental factors (tidal and wave climate) and bathymetry taking advantage
of available spatial datasets from the Bristol Channel Marine Aggregates Resources and
Constraints Project (ABP-Research, 2000). These data included tidal residuals (m-s), ebb and
flood peak (m-s), wave height (m-s) and bathymetry (m).
2.2 Review of operational practices.
Wild fisheries for native oysters occur in other areas of the UK and Europe, and a number of
these are actively managed as enhanced fisheries through a series of operational practices to
promote oyster stocks. These operational practices may have a role in the reinstatement of
habitat, restoration of oyster beds and their on-going management. A review of common and
traditional operational practices was undertaken including types and sources of shell cultch
material, operational approaches to restoration and the management of pests and diseases on
restored oyster beds.




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CCW Contract Science Report No. 960
3 RESULTS

3.1 Identification of broodstock restoration areas
3.1.1 Existing and historical O. edulis distribution and locations of O. edulis
beds.
The mapping exercise of compiled information and survey data on existing and historical O.
edulis beds revealed an extensive distribution along the South Wales coast (Figure 1). Table 1
provides supporting information including a confidence assessment of the information on
location of oyster beds. Ostrea edulis beds were recorded at sites in inshore areas but also
sporadically offshore:
   Milford Haven waterway. Ostrea edulis is widely distributed in the Milford Haven
    waterway where extensive oyster beds have been historically recorded. The main oyster
    beds are situated subtidally along the edge of the channel in the lower estuary including
    Pwllcrochan Flats and Pennar Gut. The whole area between Pennar Flats and Hazelbeach
    and including Dockyard bank is thought to have areas of oyster bed according to local
    fishermen. Oyster beds were previously common above the Cleddau road bridge and
    some areas still remain important for commercial fishermen although C. fornicata is said
    to be particularly common (Figure 2).
   South Pembrokeshire. A number of historic oyster beds were recorded along this stretch
    of coast at St Govan‘s Head (Abyssinia Haul), Stackpole, and Tenby. A single record
    indicates that O. edulis may occur offshore south of Old Castle Head (Figure 3).
   Gower coast and offshore sites. Information gleaned from sketch maps in Wright‘s 1923
    and 1932 reports and original note books provided the approximate location of a series of
    offshore sites south of the Gower Peninsular. Oysters have been reported in a large area
    south of the Helwick Bank by fishermen operating in the area prior to 1990 but the actual
    locations and densities are unknown (Figure 4).
   Swansea Bay. Ostrea edulis is distributed in two main areas of Swansea Bay at Mumbles,
    in the centre of the Bay east of the fairway. Historic beds existed south of the Mixon sand
    bank off Mumbles lighthouse and anecdotal accounts suggest further grounds around the
    Kenfig Patches (Figure 5).
   Porthcawl. The main oyster bed at Porthcawl is reported between the Nash Sands bank
    and Tusker Rock. Recent video surveys have been inconclusive but anecdotal accounts
    from fishermen suggest that O. edulis is still present in this area. A second area is
    anecdotally reported west of the Tusker Rock (Figure 6).
The locations of inshore sites have a higher confidence assessment due to better historic accounts
and more recent survey data. The size and distribution of offshore sites suggest that a series of
smaller oyster beds exist in deeper water. The confidence assessment of the offshore sites is low
for all records due to insufficient locational information.
It is recommended that restoration projects should be sited within known O. edulis beds inshore
where locational confidence is highest and where more detailed habitat information is available.




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CCW Contract Science Report No. 960

Table 1. Supporting information for mapping exercise of existing and historical O. edulis beds distribution along the South Wales coast.
                      Historical
      Site Name                                                              Notes                                                            Sources                        Location Confidence
                      Oyster Bed
                                                                                                                              South and West Wales Fishing Communities Ltd
Outer Porthcawl           No       Anecdotal location of a successful haul. No other information.                                                                                   Poor
                                                                                                                              members
                                   Area derived from local fisher‘s knowledge and Wright 1929 hauls. Area Surveyed in         Wright F.S. 1923; Woolmer A.P, 2010, South
Porthcawl Metz Haul       Yes      2010 but inconclusive - bad visibility a rocky ground. Patches maybe currently             and West Wales Fishing Communities Ltd              Medium
                                   commercially exploited.                                                                    members
                                                                                                                              South and West Wales Fishing Communities Ltd
Kenfig Patches            No       Anecdotal reports of live oysters in this area.                                                                                                  Good
                                                                                                                              members
                                                                                                                              Wright F.S. 1923; Woolmer A.P, 2010, South
                                   Location derived from local fisher‘s knowledge and Wright 1929 hauls. Surveyed 2010. and West Wales Fishing Communities Ltd
Swansea Bay               Yes                                                                                                                                                       Good
                                   Oyster shell and possible live oysters recorded. Maybe currently commercially exploited. members, K. Naylor Swansea University RV
                                                                                                                              Skipper
                                                                                                                              Wright F.S. 1923; Woolmer A.P, 2010, South
                                   Location derived from Wright 1929 description. Surveyed 2010. Oyster shell and possible and West Wales Fishing Communities Ltd
Mumbles Beds              Yes                                                                                                                                                       Good
                                   live oysters recorded. May be currently commercially exploited.                            members, K. Naylor Swansea University RV
                                                                                                                              Skipper
                                                                                                                              Wright F.S. 1923; Woolmer A.P, 2010, South
Middle Drift+Jersey                Historical and Anecdotal records of live oysters in this area. Survey inconclusive due to
                          Yes                                                                                                 and West Wales Fishing Communities Ltd              Medium
Hauls                              bad vis. Likely to be a series of patches.
                                                                                                                              members
                                                                                                                              South and West Wales Fishing Communities Ltd
Helwick Ground            No       Anecdotal reports of live oysters in nets S of Helwick Bank in living memory                                                                     Good
                                                                                                                              members
                                   Location derived from Wright 1929 description. Surveyed 2010. Oyster shell recorded. No
Tenby Beds                Yes                                                                                                 Wright F.S. 1923; Woolmer A.P, 2010                   Good
                                   live oysters. Probably not in channel (current) but S of St Catherine‘s point & E of Tenby
                                   Location derived from Wright 1929 description. Surveyed 2010. Oyster shell recorded. No
Stackpole Beds            Yes                                                                                                 Wright F.S. 1923; Woolmer A.P, 2010                   Good
                                   live oysters
                                   Location derived from Wright 1929 description. Surveyed 2010. No live oysters and oyster
Abyssinia Haul            Yes                                                                                                 Wright F.S. 1923; Woolmer A.P, 2010                 Medium
                                   shell found only at northern extent. ?Location may be further to SE?
                                   Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late
Pwll-Du Haul              Yes                                                                                                 Wright F.S. 1923                                      Poor
                                   1800's - early 1900's.
                                   Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late
Pitton Slade Haul         Yes                                                                                                 Wright F.S. 1923                                      Poor
                                   1800's - early 1900's. Possibly located on a transect when Pitton opens South of Slade
White Oyster Ledges                Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late
                          Yes                                                                                                 Wright F.S. 1923                                      Poor
Hauls                              1800's - early 1900's. Nomenclature may be misleading.
                                   Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late
Star Haul                 Yes                                                                                                 Wright F.S. 1923                                      Poor
                                   1800's - early 1900's.
                                   Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late
Bantham Haul              Yes                                                                                                 Wright F.S. 1923                                      Poor
                                   1800's - early 1900's.



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CCW Contract Science Report No. 960

                      Historical
      Site Name                                                              Notes                                                                 Sources                        Location Confidence
                      Oyster Bed
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from fisher‘s knowledge. CCW survey and NBN records record live
Dale Bay                 Yes                                                                                                       Milford Haven), South and West Wales Fishing          Good
                                   oysters.
                                                                                                                                   Communities Ltd members, NBN Database
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from fisher‘s knowledge and observations. Not commercially exploited
Angle Bay                No                                                                                                        Milford Haven), South and West Wales Fishing        Medium
                                   but possible historically.
                                                                                                                                   Communities Ltd members
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from fisher‘s knowledge and observations. Not commercially exploited
West Angle Bay           No                                                                                                        Milford Haven), South and West Wales Fishing        Medium
                                   but possible historically.
                                                                                                                                   Communities Ltd members
Stack Rock and Dale                General location derived from Wright 1932 sketch maps of oyster fishermen's worked in
                         Yes                                                                                                       Wright F.S. 1932                                      Low
Bed                                the late 1800's - early 1900's.
                                   Location derived from fisher‘s knowledge and observations. Some survey records confirm pers. comm. Fen Duke (skipper of Emily Rose,
Milford Shelf/South
                         No        oysters in this area. Not currently commercially exploited but may have been historically. Milford Haven), South and West Wales Fishing             Medium
Hook
                                   Not a main bed.                                                                                 Communities Ltd members, NBN Database
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from fisher‘s knowledge and observations. Survey records confirm
                                                                                                                                   Milford Haven), South and West Wales Fishing
Pwllcrochan Flats        Yes       oysters in this area. Area off Outfall Buoy currently commercially exploited. This and                                                                High
                                                                                                                                   Communities Ltd members, NBN Database,
                                   adjacent areas are historic beds.
                                                                                                                                   Wright 1923, 1932
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from fisher‘s knowledge and observations. Survey records confirm
                                                                                                                                   Milford Haven), South and West Wales Fishing
Pennar Gut               Yes       oysters in this area. Area off Outfall Buoy currently commercially exploited. This and                                                                High
                                                                                                                                   Communities Ltd members, NBN Database,
                                   adjacent areas are historic beds.
                                                                                                                                   Wright 1923, 1932. Saurel & Richardson, 2003
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from fisher‘s knowledge and observations. Survey records confirm
                                                                                                                                   Milford Haven), South and West Wales Fishing
Pennar Flats             Yes       oysters in this area. Area off Outfall Buoy currently commercially exploited. This and                                                                High
                                                                                                                                   Communities Ltd members, NBN Database,
                                   adjacent areas are historic beds.
                                                                                                                                   Wright 1923, 1932. Saurel & Richardson, 2003
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from compiled fisher‘s knowledge and survey information. Survey
                                                                                                                                   Milford Haven), South and West Wales Fishing
Dockyard Bank            Yes       records confirm oyster in this area. Possibly a large shell deposit/relic bed. Considered part                                                        High
                                                                                                                                   Communities Ltd members, NBN Database,
                                   of historic Hazelbeach Beds
                                                                                                                                   Wright 1923, 1932. Saurel & Richardson, 2003
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from compiled fisher‘s knowledge and survey information. Survey
                                                                                                                                   Milford Haven), South and West Wales Fishing
Hazelbeach Beds          Yes       records confirm oyster in this area. Possibly a large shell deposit/relic bed. Considered part                                                        High
                                                                                                                                   Communities Ltd members, NBN Database,
                                   of historic Hazelbeach Beds
                                                                                                                                   Wright 1923, 1932. Saurel & Richardson, 2003
                                                                                                                                   pers. comm. Fen Duke (skipper of Emily Rose,
                                   Location derived from fisher‘s knowledge and observations. Not commercially exploited
Neyland/Hobbs Point      No                                                                                                        Milford Haven), South and West Wales Fishing        Medium
                                   but likely historically. Currently waiting for shellfish classification to enable exploitation.
                                                                                                                                   Communities Ltd members,




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