This is a natural phenomenon, in which planktonic algae produce biological toxins that can accumulate temporarily within the shellfish that feed on them. The toxins do not harm the algae or the shellfish, but can cause three kinds of food poisoning in humans:
- Paralytic Shellfish Poisoning (potentially fatal)
- Diarrhetic Shellfish Poisoning
- Amnesic Shellfish Poisoning
It is not easy to predict algal toxin production, it has no visible effect on shellfish and many toxins are resistant to cooking or freezing. Hence shellfish beds are sampled throughout the year, on a ‘positive release’ basis. If a sample is found to contain a toxin, fishing is suspended at the site until subsequent samples are found to be free of it.
Commission Regulation 853/2004 and subsequent regulations lay down the health conditions and methods of analysis of certain marine biotoxins, for the production and placing on the market of live bivalve molluscs. As part of the controls to protect public health, the directive requires the Competent Authority (Food Standards Agency Northern Ireland (FSA-NI)) to carry out monitoring of relaying and production areas for the presence of toxin producing plankton in water and biotoxins in shellfish tissue.
AFBI Stormont undertakes the biotoxin analysis on behalf of FSA-NI. The biotoxins specified within the legislation are Paralytic Shellfish Toxins, the Diarrhetic Shellfish Toxin Group and Amnesic Shellfish Toxin (Domoic Acid). New regulations concerning the organisation of official controls are due to be implemented in 2006.
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