Research report

​Monitoring Programme for Algal Toxins in Shellfish from Scotland

Details

Davidson, K., Miller, P.I., Wilding, T., Shutler, J., Bresnan, E., Kennington, K. & Swan, S. (2009)
A large and prolonged bloom of Karenia mikimotoi in Scottish waters in 2006.
Harmful Algae, 8, 349-61.

FRS Marine Laboratory
Howard, F

Marine biotoxins produced by certain species of phytoplankton can be accumulated in the tissues of filter feeding bivalve molluscs. If these molluscs are then consumed by humans, toxin related illness may occur. United Kingdom and European Community food safety regulations stipulate the levels of toxin permitted in products placed on the market for human consumption, and also require that monitoring for the presence of toxins be undertaken to ensure that no potentially hazardous shellfish are placed on the market for human consumption. A monitoring and surveillance programme is undertaken in Scotland, and samples of bivalve molluscs are tested for the presence of Amnesic Shelfish Poisons (ASP), Diarrhetic Shellfish Poisons (DSP), and Paralytic Shellfish Poisons (PSP). The maximum toxin levels permitted are ASP: 20 mg/g flesh, DSP; No toxins permitted, PSP: 80 mg/100 g flesh.

Fisheries Research Services (FRS) has conducted an extensive monitoring and surveillance programme for marine biotoxins in bivalve mollusc flesh in Scotland since 1991, and for the causative phytoplankton since 1995. The monitoring programmes are operated to comply with the requirements of the shellfish hygiene directive, 91/492/EEC, and with the current UK implementing legislation, The Food Safety (Fishery Products and Live Shellfish) (Hygiene) Regulations 1998, as amended.

The programmes are undertaken on behalf of the Food Standards Agency (Scotland) (FSAS).

The monitoring is carried out on bivalve mollusc samples from classified harvesting areas, and from offshore scallop fishing grounds; sampling is undertaken throughout the year. The programme is based upon a sampling frequency of monthly during the period October to March, and weekly, fortnightly or monthly during the period April to September. The sampling frequency is based on a risk assessment of each site, which takes account of the shellfish production and the historical occurrence of toxins. Sampling frequency is increased if toxins are detected, and species other than bivalve molluscs may be tested.

In the period 1 April 2001 to 31 March 2002, shellfish from 56 primary inshore production areas, 56 secondary areas and 10 offshore fishing areas were examined. A total of 6,300 mollusc samples were analysed; 2,029 for PSP, 1,145 for DSP and 3,126 for ASP.

In the inshore productions areas, PSP toxins were found in 80 samples from 32 sites, DSP toxins were found in 146 samples from 35 sites, and ASP toxins, above the Limit of Detection (LOD) were found in 96 samples from 18 sites. Voluntary Closure Agreements (VCAs) were made with affected aquaculture site operators, and warning notices erected where public access and harvesting could take place.

The site location and the result of samples with detected toxins above the permitted level, which resulted in harvesting restrictions being imposed, is shown below:

Site Date No of samples Species Toxin PSP (mg STX equiv/100g) DSP ASP (mg DA/g) Action taken
St Abbs May
Aug-Sept
1
3
Mussels
Mussels
142 Positive Warning notices erected
Scapa Flow May-June
June-Nov
5
11
Mussels
Mussels
88 -245 Positive Restrictions imposed
Kirkwall June
Sept
1
1
Mussels
Mussels
299 Positive Restrictions imposed
Mill Sands June 1 Cockles 152 Restrictions imposed
Whalefirth Sept-Oct 2 Mussels Positive Closure order
Ura Firth Sept 1 Scallop W 20 Closure order
Olna Firth June
July/Oct
1
2
Mussels
Mussels
184
Positive
Closure order
Busta Voe June 1 Mussels 163 Closure order
Clift Sound October 1 Mussels Positive Closure order
Clousta Voe May 1 Mussels 164 Closure order
East Burra Firth Jul-Oct 5 Mussels Positive Closure order imposed
Linga Voe May
Jul/Oct
1
2
Mussels
Mussels
211 Positive Closure order imposed
Mid Yell Voe May 1 Mussels 130 Closure order
Ronas Voe May 1 Mussels 86 Closure order
Uyea Voe Sept 1 Mussels Positive Closure order
Loch Eriboll July-Oct 4 Mussels Positive Closure order
Loch Inchard May-June
July-Oct
2
11
Mussels
Mussels
112,
277
Positive Closure order
Loch Laxford Aug - Oct 8 Mussels Positive Closure order
Kylesku August 1 Mussels Positive Closure order
Loch Kirkaig Sep/Mar 2 Mussels Positive Warning notices
Dornoch Firth Sept-Oct 3 Mussels Positive Closure order
Little Loch Broom Aug-Oct 5 Mussels Positive Closure order Imposed
Loch Broom October 1 Mussels Positice Warning notice
Loch Ewe Jun-Aug
Apr-Mar 02
7
23
26
Mussels
Scallop G
Scallop W
Positive
LOD – 43
10 - >100
Closure orders Imposed
Loch Torridon May-June
Jun/Sept
4
6
Mussels
Mussels
80- 220 Positive Closure orders Imposed
Loch Toscaig Sept 1 Mussels Positive Restrictions imposed
Loch Kishorn Aug-Oct 4 Mussels Positive Closure order
Broadford Bay Aug-Dec
Jun-Sept
May
Aug-Sep
4
5
1
3
Mussels
Queens
Scallop G
Scallop W
Positive
Positive

27
43 - 67
Closure ordersImposed
Loch Ainort October 1 Scallop W >100 Restrictions imposed
Loch Sligachan May-Dec
Aug/Feb
8
2
Scallop G
Scallop W
LOD- 64
29, >100
Closure orders imposed
Loch Greshornish Jun-Jul
Jul-Oct
2
5
Mussels
Mussels
148,122
Positive
Closure ordersImposed
Loch Dunvegan June
Oct-Nov
1
2
Mussels
Mussels
405
Positive
Closure ordersImposed
Loch Harport Jul/Oct 2 Mussels Positive Closure order
Loch Eishort July 1 Mussels 89 Closure order
Badicaul



Sep-Oct
July
May/Aug/Dec/Feb
June/Feb
2
1
4
2
Queens
Scallop W
Scallop G
Scallop W
Positive
Positive
27,26,38,2326,70 Closure order and restrictions imposed
Loch Hourn Jun-JulAug-Nov 310 Mussels 214 121, 98 Positive Closure orders imposed
Loch Leven May 1 Mussels Positive Closure order
Loch Roag Jun-Jul
October
Sept
2
1
1
Mussels
Mussels
Mussels
101, 127
Positive


22
Closure orders imposed
Loch Creran October 1 P.oyster Positive Closure order
Loch Crinan Jun-Feb 6 Scallop W 56 - >100 Closure order
Loch Coalisport Sept 2 Scallop W >100 Closure order
Barmore Aug/Oct-Nov 3 Queens Positive Closure orders imposed
Ardkinglass Aug -Nov 5 Mussels Positive Closure order
Loch Striven Aug/Oct-Nov 3 Mussels Positive Closure order
Loch Scridain Jul/Sep 3 Mussels Positive Closure order
Fairlie Aug-Oct
December
October
8
1
Mussels
P.oyster

Positive
Positive
Closure orders imposed

In the offshore scallop fishing areas, PSP toxins were found in both scallop gonad and whole scallop samples in the East Coast, Moray Firth, Orkney, Shetland, Hebrides, and the North and South Minches. PSP toxins were found only in whole scallops in the Sound of Jura, and none were found in the Clyde or Irish Sea. DSP toxins were found, using the bioassay, in whole scallops in all areas except Shetland, while ASP toxins were found in both gonad tissue and whole animals in all areas. In Shetland, Clyde and Irish Sea areas, detected ASP levels in gonad tissue were below the action level.

For the offshore scallop fishing areas, PSP toxins at or above the action level were found in 18 (3%) gonad tissue samples, and 55 (10%) whole animals. DSP was found in 81 whole animal samples (47%) by bioassay. ASP toxins at or above the action level were found in 111 (10%) gonad tissue samples, and in 786 (71%) whole animal samples.

Fishing restrictions by means of a closure order under the Food and Environment Protection Act 1985 (FEPA) or shucking requirements (whereby only the processed adductor muscle and gonad are permitted to enter the marketplace) were imposed where appropriate.

Project Code: S02007

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