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

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 © CCGC/CCW date You may reproduce this document free of charge for non-commercial and internal business purposes in any format or medium, provided that you do so accurately, acknowledging both the source and Countryside Council for Wales's copyright, and do not use it in a misleading context. This is a report of research commissioned by the Countryside Council for Wales. However, the views and recommendations presented in this report are not necessarily those of the Council and should, therefore, not be attributed to the Countryside Council for Wales.

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 CCW North Region Library, Mold CCW North Region Library, Bangor CCW S&E Region Library, Cardiff CCW S&E Region Library, Llandrindod CCW West Region Library, Aberystwyth National Library of Wales British Library Welsh Assembly Government Library Joint Nature Conservation Committee Library Scottish Natural Heritage Library Natural England Library Distribution list (others): Aethne Cooke, CCW Mike Camplin, CCW Anne Bunker, CCW Andrea Winterton, CCW Catherine Duigan, CCW Lucy Kay, CCW Rowland Sharp, CCW Ziggy Otto, CCW Rebecca Wright, CCW Kirsten Ramsay, CCW Colin Charman, CCW Clare Eno, CCW Graham Rees, WAG Sue Burton, Pembrokeshire Marine SAC Blaise Bullimore, Camarthen Bay & Estuaries EMS Bill Sanderson, Herriot-Watt University Tom Pickerell, Shellfish Association of Great Britain 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 i 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

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

CCW Contract Science Report No. 960 ii 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

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

CCW Contract Science Report No. 960 iii 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

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

CCW Contract Science Report No. 960 iv 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

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

CCW Contract Science Report No. 960 v 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

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

CCW Contract Science Report No.

960 vi 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.

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

CCW Contract Science Report No. 960 vii 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,

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

CCW Contract Science Report No. 960 viii 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.

CCW Contract Science Report No. 960 1 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

CCW Contract Science Report No. 960 2 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).

CCW Contract Science Report No. 960 3 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

CCW Contract Science Report No. 960 4 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.

CCW Contract Science Report No. 960 5 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.

CCW Contract Science Report No. 960 6 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.

CCW Contract Science Report No.

960 7 Table 1. Supporting information for mapping exercise of existing and historical O. edulis beds distribution along the South Wales coast. Site Name Historical Oyster Bed Notes Sources Location Confidence Outer Porthcawl No Anecdotal location of a successful haul. No other information. South and West Wales Fishing Communities Ltd members Poor Porthcawl Metz Haul Yes Area derived from local fisher‘s knowledge and Wright 1929 hauls. Area Surveyed in 2010 but inconclusive - bad visibility a rocky ground. Patches maybe currently commercially exploited.

Wright F.S. 1923; Woolmer A.P, 2010, South and West Wales Fishing Communities Ltd members Medium Kenfig Patches No Anecdotal reports of live oysters in this area. South and West Wales Fishing Communities Ltd members Good Swansea Bay Yes Location derived from local fisher‘s knowledge and Wright 1929 hauls. Surveyed 2010. Oyster shell and possible live oysters recorded. Maybe currently commercially exploited. Wright F.S. 1923; Woolmer A.P, 2010, South and West Wales Fishing Communities Ltd members, K. Naylor Swansea University RV Skipper Good Mumbles Beds Yes Location derived from Wright 1929 description.

Surveyed 2010. Oyster shell and possible live oysters recorded. May be currently commercially exploited. Wright F.S. 1923; Woolmer A.P, 2010, South and West Wales Fishing Communities Ltd members, K. Naylor Swansea University RV Skipper Good Middle Drift+Jersey Hauls Yes Historical and Anecdotal records of live oysters in this area. Survey inconclusive due to bad vis. Likely to be a series of patches.

Wright F.S. 1923; Woolmer A.P, 2010, South and West Wales Fishing Communities Ltd members Medium Helwick Ground No Anecdotal reports of live oysters in nets S of Helwick Bank in living memory South and West Wales Fishing Communities Ltd members Good Tenby Beds Yes Location derived from Wright 1929 description. Surveyed 2010. Oyster shell recorded. No live oysters. Probably not in channel (current) but S of St Catherine‘s point & E of Tenby Wright F.S. 1923; Woolmer A.P, 2010 Good Stackpole Beds Yes Location derived from Wright 1929 description. Surveyed 2010. Oyster shell recorded. No live oysters Wright F.S.

1923; Woolmer A.P, 2010 Good Abyssinia Haul Yes Location derived from Wright 1929 description. Surveyed 2010. No live oysters and oyster shell found only at northern extent. ?Location may be further to SE? Wright F.S. 1923; Woolmer A.P, 2010 Medium Pwll-Du Haul Yes Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late 1800's - early 1900's.

Wright F.S. 1923 Poor Pitton Slade Haul Yes Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late 1800's - early 1900's. Possibly located on a transect when Pitton opens South of Slade Wright F.S. 1923 Poor White Oyster Ledges Hauls Yes Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late 1800's - early 1900's. Nomenclature may be misleading. Wright F.S. 1923 Poor Star Haul Yes Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late 1800's - early 1900's.

Wright F.S. 1923 Poor Bantham Haul Yes Location derived from Wright 1929 sketch maps of oyster fishermen's worked in the late 1800's - early 1900's.

Wright F.S. 1923 Poor

CCW Contract Science Report No. 960 8 Site Name Historical Oyster Bed Notes Sources Location Confidence Dale Bay Yes Location derived from fisher‘s knowledge. CCW survey and NBN records record live oysters. pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database Good Angle Bay No Location derived from fisher‘s knowledge and observations. Not commercially exploited but possible historically. pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members Medium West Angle Bay No Location derived from fisher‘s knowledge and observations.

Not commercially exploited but possible historically.

pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members Medium Stack Rock and Dale Bed Yes General location derived from Wright 1932 sketch maps of oyster fishermen's worked in the late 1800's - early 1900's. Wright F.S. 1932 Low Milford Shelf/South Hook No Location derived from fisher‘s knowledge and observations. Some survey records confirm oysters in this area. Not currently commercially exploited but may have been historically. Not a main bed.

pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database Medium Pwllcrochan Flats Yes Location derived from fisher‘s knowledge and observations.

Survey records confirm oysters in this area. Area off Outfall Buoy currently commercially exploited. This and adjacent areas are historic beds. pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database, Wright 1923, 1932 High Pennar Gut Yes Location derived from fisher‘s knowledge and observations. Survey records confirm oysters in this area. Area off Outfall Buoy currently commercially exploited. This and adjacent areas are historic beds.

pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database, Wright 1923, 1932. Saurel & Richardson, 2003 High Pennar Flats Yes Location derived from fisher‘s knowledge and observations. Survey records confirm oysters in this area. Area off Outfall Buoy currently commercially exploited. This and adjacent areas are historic beds. pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database, Wright 1923, 1932. Saurel & Richardson, 2003 High Dockyard Bank Yes Location derived from compiled fisher‘s knowledge and survey information.

Survey records confirm oyster in this area. Possibly a large shell deposit/relic bed. Considered part of historic Hazelbeach Beds pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database, Wright 1923, 1932. Saurel & Richardson, 2003 High Hazelbeach Beds Yes Location derived from compiled fisher‘s knowledge and survey information. Survey records confirm oyster in this area. Possibly a large shell deposit/relic bed. Considered part of historic Hazelbeach Beds pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database, Wright 1923, 1932.

Saurel & Richardson, 2003 High Neyland/Hobbs Point No Location derived from fisher‘s knowledge and observations. Not commercially exploited but likely historically. Currently waiting for shellfish classification to enable exploitation. pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, Medium

CCW Contract Science Report No. 960 9 Site Name Historical Oyster Bed Notes Sources Location Confidence River Cleddau Grounds (L) Yes Location derived from compiled fishers knowledge, survey and historic information. Survey records confirm oyster in this area. Historically commercially important oyster beds. Currently commercially exploited. High densities of C fornicata are reported within this area. pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database, Wright 1923, 1932.

High River Cleddau Grounds (M) Yes Location derived from compiled fishers knowledge, survey and historic information.

Survey records confirm oyster in this area. Historically commercially important oyster beds. Currently commercially exploited. High densities of C fornicata are reported within this area. pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database, Wright 1923, 1932. Saurel & Richardson, 2003 High River Cleddau Grounds (U) Yes Location derived from compiled fishers knowledge, survey and historic information. Survey records confirm oyster in this area. Llangwm beds historically commercially important oyster beds. Not commercially exploited.

High densities of C fornicata are reported within this area.

pers. comm. Fen Duke (skipper of Emily Rose, Milford Haven), South and West Wales Fishing Communities Ltd members, NBN Database, Wright 1923, 1932. Saurel & Richardson, 2003 High Old Castle Head Offshore Yes Location derived from historical record NBN Database record from 1899 Low

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