Shellfish waters

Status: No overall trend discernible with few or no concerns

(‘Shellfish water microbiology’ status and trend, Baxter et al, 2011)

Clean water is necessary for the production of healthy shellfish, and is especially important when the shellfish are intended for human consumption. This is important given the fact that toxins and micro-organisms can become concentrated in the flesh of shellfish, which filter water for feeding. Shellfish Water Protected Areas and Classified Shellfish Harvesting Areas are two ways in which waters can be designated to help protect human health.


Image; Oyster Fishing. © Solway Firth Partnership. Photographer; Colin Tennant

Shellfish waters

Shellfish Water Protected Areas

The Shellfish Waters Directive (2006/113/EC) was repealed in 2013 and subsumed into the Water Framework Directive (WFD) (2000/60/EC). The WFD established a legal framework for the protection, improvement and sustainable use of Europe’s water environment, based on a system of river basin management (see Transitional and Coastal waters section for more information on the WFD). The WFD established ‘shellfish water protected areas’ (SWPAs), therefore it is only a designation within transitional and coastal waters. SWPAs are ‘protected areas’ under the WFD and can be protected, or if need be, improved, through a package of measures integrated with the process of river basin management planning.

The Scottish Government designates SWPAs in Scottish waters. Loch Ryan (ID: UKS799236) is designated as a SWPA designated under the 2016 order; The Water Environment (Shellfish Water Protected Areas: Designation) (Scotland) Order 2016. The other 84 SWPAs in Scotland were designated through the earlier Water Environment (Shellfish Water Protected Areas: Designation) (Scotland) Order 2013. The Loch Ryan SWPA covers the whole of Loch Ryan, with the boundary crossing the mouth of the loch at Milleur Point. This means that part of this SWPA falls outside of the ‘Solway Marine Region’ and an area in the northeast of the loch forms part of the ‘Clyde Marine Region’. The extent of the Loch Ryan SWPA and all Scottish SWPAs can be seen in the National Marine Plan Interactive data layer here. Water quality in designated areas is monitored by the Scottish Environment Protection Agency (SEPA) in Scotland. Classified Shellfish Harvesting Areas (discussed below) often lie fully or partially within a SWPA. Legislation does not prevent sites being developed in zones outside of the designated SWPAs. The Water Environment (Shellfish Water Protected Areas: Objectives and Classification etc.) (Solway Tweed) Directions 2021 direct SEPA on setting objectives and how to classify, etc. the quality of shellfish water protected areas within the Scottish part of the Solway Tweed River Basin District, which covers the Solway.

For sites wholly in the English portion of the Solway Tweed cross border river basin district they are designated by the Secretary of State under regulation 3A of the The Water Environment (Water Framework Directive) (Solway Tweed River Basin District) Regulations 2004. The Environment Agency monitor SWPAs in England. The Silloth and Solway SWPAs in the English side of the Solway were designated by The Water Environment (Water Framework Directive) (Solway Tweed River Basin District) Regulations 2004 as amended.
The Rivers Trust online mapping has a data layer providing information on these two sites, along with the other sites in England which are designated as SWPAs, see the data here.

The ‘Silloth’ areas extends from just south of the mouth of Black Dub to Skinburness. The area extends out into the Firth approximately 7km at the widest point at the mouth of Black Dub, and narrows towards Skinburness. The ‘Solway’ area is a semi-circular area around the Solway coast at Cardurnock.

The Water Environment (Water Framework Directive) (England and Wales) Regulations 2017 outlines designation of shellfish water protected areas in river basin districts wholly in England and Wales, and straddle the two jurisdictions (not including the Solway Tweed as it is cross border with Scotland), and therefore apply to the outer part of the English Solway, which forms part of the North West River Basin District. There are no SWPAs in the outer part of the English Solway.

SWPAs have three classifications on the basis of E.Coli concentrations in sampled shellfish; Good, Fair and Insufficient, with ‘insufficient’ being the automatic classification if the shellfish water does not meet ‘good’ or ‘fair’ water quality standards in the Solway Tweed River Basin. The objective of the SWPA designation is for the waters to reach ‘good’ status, with the timeline to achieve this status in all SWPAs by 2027.

SEPA’s Water Environment Hub details the 2014/15 condition for designated SWPAs, however Loch Ryan is not included in the list of SWPAs. The ‘Solway’ and ‘Silloth’ SWPAs are included. Both Silloth and Solway SWPAs are ‘At target objective’ according to the SEPA water environment hub, and expected to remain ‘at target objective’ in 2021.


Image; The Loch Ryan Oyster Fishery Company Ltd. © Solway Firth Partnership. Photographer; Colin Tennant

Shellfish waters

Monitoring Shellfish

Official Controls

Live bivalve molluscs (LBM) are filter feeders known to accumulate contaminants in the marine environment. When LBMs are intended for human consumption, there are official controls in place to ensure that they are safe for consumption before being sold, in addition to the SWPAs designated as ‘protected areas’ as discussed above.

A ‘competent authority’ is responsible for the classification and official controls related to monitoring Classified Shellfish Harvesting Areas (CSHAs). In Scotland the competent authority is Food Standards Scotland (FSS), and Food Standards Agency (FSA) is the competent authority in England.

The Official Controls in (retained) Regulation (EU) 2017/625 (which has been amended post-EU exit) cut across the entire agri-food chain to ensure competent authorities in EU member states are adhering to rigorous and impartial controls. Along with its Delegated and Implementing regulations, it establishes an integrated approach to official control requirements. This ensures the safety of shellfish products across Europe before they are placed on the market.

These controls are summarised by the FSS website; ‘FSS [and FSA] is required, by European legislation, to undertake an extensive programme of Official Control monitoring of LBMs and marine phytoplankton (algae) from LBM harvesting waters. The results of this programme are used to determine whether an area should be open or closed for harvesting depending on the levels of microbiological and chemical contaminants, including marine biotoxins’ (Food Standards Scotland, n.d.).

CSHAs define the waters which are monitored for the above indicators of an unsafe product. CSHAs do not always lie within SWPAs.

Classification of CSHAs is one of the responsibilities of FSS and FSA, measuring the levels of E.coli present per 100g of flesh as laid out in Annex III of the (retained) EU Regulation 853/2004 and Articles 53, 54 and 55 of (retained) Regulation (EU) 2019/627.


Process of classifying CSHAs

Sanitary surveys are required under (retained) EU regulation (2017/625) before classifying a new CSHA, but may not be required under other circumstances. FSS and FSA will determine whether or not one is necessary for the production area. If required, a sanitary survey looks at pollution sources impacting the shellfish harvesting area, and establish the most appropriate ‘representative monitoring point’, as well as determining the most appropriate sampling plan for the area. As these surveys look at pollution sources they are highly relevant for information about continuous and intermittent waste water outfalls located in the vicinity of survey sites (see Waste water and industrial outfalls).

For more information on the process of conducting sanitary surveys and where to find previously published sanitary surveys for Scotland and England, see the FSS website here, or the FSA website here.

The classification of an area is based on E.coli concentrations impacting the actions a harvester must take in order to send their product to the consumer market. Shellfish samples are collected from CSHA sites and a classification is awarded on the basis of the data over the previous 3 years (if insufficient data, 1-year data is sufficient to award classification). Regulation (EU) 2017/625 allows additional, supplementary, harvester samples to be considered in the official monitoring programme for classification.

Classifications are from ‘A’ to ‘C’ with combined classifications ‘A/B’ and ‘B/C’. The full classification criteria and action for each category is outlined in tables on the FSA and FSS websites. The classification criteria and actions are the same for Scotland and England. CSHAs with a classification of ‘A’ are able to send harvested shellfish directly to market, with ‘B’ subject to purification, relaying in Class A area, or need to be cooked by an approved method, and classification ‘C’ subject to relaying for at least 2 months and approved method cooking. Harvesting is not permitted in any area with E.coli numbers above the criteria for classification ‘C’, where there is over 46,000 E. coli/100g of flesh.

The E.coli classification protocol from FSS, and the protocol for classification of shellfish production areas in England from the FSA, contain information about sanitary surveys and the entire classification process.


Solway Classifications

Classifications do not need to be annual, and can be preliminary, provisional, seasonal or even partial years. This can be seen in the 2021/2022 classification of Loch Ryan, where the classification provided is not for the full year 2021/2022, and is instead classified as ‘B’ up to December 2021, then will be classified as ‘A’ Jan to March 2022.

Loch Ryan, Wigtown Bay, Fleet Bay, and Kirkcudbright Bay are CSHAs in the Scottish Solway. Razor shells (Ensis spp.) are the species sampled for E.coli monitoring for all Scottish Solway sites, apart from Loch Ryan where Native Oysters (Ostrea edulis) are sampled. The classifications detailed below cover Scottish SWPAs for the period from 1 Apr 2021 to 31 March 2022.

Classified Shellfish Harvesting Area Species Period covering Classification
Loch Ryan Native Oysters (Ostrea edulis) 2021
2022 (Jan – March)
Wigtown Bay Razors (Ensis spp.) 2021/2022 A
Fleet Bay Razors (Ensis spp.) 2021/2022 A (Dormant)
Kirkcudbright Bay Razors (Ensis spp.) 2021/2022 A

Fleet Bay CSHA is currently ‘dormant’, this may be due to lack of harvesting activity, but other information on sites being labelled as ‘dormant’ are available in part 11 of the FSS protocol for classification, available here.

Classification documents are available on FSS here. The full details of the results of the E.coli monitoring are available on Scotland’s aquaculture website and on the FSS website.

Data for Loch Ryan, Wigtown Bay, Fleet Bay, and Kirkcudbright Bay for biotoxin, microhygiene, phytoplankton monitoring and area classification data are available by clicking on each location through Scotland’s aquaculture website.

Sample dates and specific concentrations of E.coli per 100g of samples are displayed in a simple table and included in a graph with trend lines through the Centre for Environment, Fisheries and Aquaculture (Cefas) for Loch Ryan, Wigtown Bay, Fleet Bay, Kirkcudbright Bay.

In England, FSA 2020- 2021 (1 September 2020 – 31 August 2021) classifications are available here. Silloth- South (Lees Scar) is the only CSHA in the English Solway in 2020/2021. It is classified for mussel (Mytilus spp.) harvesting and has the 2020/2021 classification ‘B’. The Lees Scar ‘B’ classification is also ‘Long Term’ meaning that the area has been stable with compliance over at least 5 years.

Silloth – Dubmill Scar was declassified as of Sept 2020 (Pacific Oysters, Crassostrea gigas). This may be because an insufficient number of samples were received. For class B and C there must be at least 8 samples per year, and 10 for class A classifications. The Dubmill Scar site had 4 samples provided in 2018, no samples in 2019, and 6 in 2020 according to the samples listed in Cefas’s shellfish monitoring results for the site (available here). Prior to declassification Dubmill Scar had been classified as ‘B’ Long Term. Silloth South -Catherinehole Scar is also listed in the 2020-2021 classifications, as a site which is a prohibited area, and must not be harvested or subject to harvesting. Data for the monitoring of Dubmill Scar, and the currently classified Lees Scar are available through Cefas.



Other strands of monitoring

Other strands of the official control programme of monitoring are Biotoxin and Phytoplankton, Chemical contaminant Monitoring Programmes.

As already mentioned, shellfish are filter feeders and are highly susceptible to accumulating marine biotoxins, resulting from feeding on biotoxin producing phytoplankton, and chemical contaminants such as heavy metals, polycyclic aromatic hydrocarbons, and dioxin and dioxin-like PCBs.

Sampling of shellfish flesh is undertaken from fixed monitoring points in CSHAs (and for scallops harvested from unclassified offshore waters at commercial processors). The samples are tested for Paralytic Shellfish Poisoning, Amnesic Shellfish Poisoning, and Lupophillic Shellfish Toxins, to identify if there is an increased risk of shellfish becoming contaminated and being unsafe for consumption. When exceeding the legal limits set by (retained) EU legislation, action is taken to close the harvesting areas through temporary closure notices and, if necessary, warning notices for casual gatherers and the wider community. For more information on biotoxin monitoring in Scotland click here, for more information on biotoxin monitoring in England click here.

Water samples are collected from CSHAs to determine phytoplankton concentrations as some phytoplankton are toxin producing and monitoring can provide an early indication of toxic events. Phytoplanktons monitored include Alexandrium, Dinophysis and Prorocentrum lima, and pseudo-nitzschia.

Where ‘alert’ concentrations are found harvesters can still harvest LBMs but should take the necessary precautions. For more information on phytoplankton monitoring in Scotland click here, for more information on biotoxin monitoring in England click here. Note that according to the FSA and FSS websites (links provided above), the ‘alert’ concentration for Pseudo-nitzschia is three times more (150,000 cells/litre) in England than in Scotland (50,000 cells/litre).

The latest results for biotoxin and phytoplankton monitoring are available for Scotland through the FSS website here, all historic monitoring data (prior to the latest results) is available through Scotland’s Aquaculture website, here. Biotoxin and phytoplankton monitoring results for England can be found through Cefas, available here.

Legislation also requires that CSHAs are monitored for chemical contaminant concentrations due to the potential risk of bio-accumulation. The EU set levels of chemical contaminants are the same in Scotland and England. Levels should not exceed those laid out in (retained) EC Regulation 1881/2006, as amended.

For more information on phytoplankton monitoring in Scotland click here, for more information on biotoxin monitoring in England click here.


Image; Mussels. ©  N. Coombey/ Solway Firth Partnership.

Shellfish waters


Baxter, J.M., Boyd, I.L., Cox, M., Donald, A.E., Malcolm, S.J., Miles, H., Miller, B., Moffat, C.F., (Editors), (2011). Scotland’s Marine Atlas: Information for the national marine plan. Marine Scotland, Edinburgh. pp 191. Available here. (Accessed: 22.07.19)

Food Standards Agency (2020). Protocol for Classification of Shellfish Production Areas, England and Wales. Available here. (Accessed: 06.04.21)

Food Standards Agency (n.d.) Biotoxin and phytoplankton monitoring. Available here. (Accessed: 06.04.21)

Food Standards Agency (n.d.) Shellfish Classification. Available here. (Accessed: 06.04.21)

Food Standards Agency (n.d.) Shellfish Official Controls. Available here. (Accessed: 06.04.21)

Food Standards Agency (n.d.) Shellfish production area assessments. Available here. (Accessed: 06.04.21)

Food Standards Scotland (Revised 2019). Shellfish Classification Protocol. Available here. (Accessed: 06.04.21)

Marine Management Organisation. (n.d.). Marine Planning Evidence Base. Available here. (Accessed: 14.05.18)

Marine Scotland (n.d.). Scotland’s National Marine Plan Interactive. Available here. (Accessed: 06.08.19)

Mills, F., Sheridan, S. and Brown S. (2017). Clyde Marine Region Assessment. Clyde Marine Planning Partnership. pp 231, Available here. (Accessed: 14.05.18)

Scottish Environmental Protection Agency (n.d.). Water Environment hub. Available here. (Accessed: 06.04.21)

Solway Firth Partnership (1996). The Solway Firth Review, Solway Firth Partnership, Dumfries. Available here. (Accessed: 23.07.19)


In-Text References;

Food Standards Scotland (n.d.) Shellfish Safety and Sanitation. Available here. (Accessed: 04.04.21)


Image; Razor Clam ©  N. Coombey/ Solway Firth Partnership.