Shellfish

Regular samples of shellfish are obtained from the classified shellfish beds to monitor levels of contamination and to enable the classification of the beds under UK legislation.

These samples are used to find out the level of contamination present in the shellfish which then determines the classification of the beds and the level of processing required before being able to be sold.

Bivalves must only be harvested from classified areas.

Shellfish areas are classified as follows:

• Class A – for direct sale for human consumption bivalves must not exceed 230 colony forming units of Escherichia coli in 100g of flesh and intra-valvular liquid
• Class B – all bivalves must be purified before they can be sold live. A maximum limit of 4600 colony forming units of Escherichia coli in 100g of flesh and intra-valvular liquid
• Class C – the bivalves have to be relayed in designated ‘relaying sites’ for at least two months, then purified if required or subjected to heat treatment before they will be deemed fit for human consumption. A maximum limit of 46000 colony forming units of Escherichia coli in 100g of flesh and intra-valvular liquid
• Prohibited areas - Shellfish from areas with consistently prohibited level results (greater than 46000 E. coli/100g) must not be subject to production or be harvested

Maps of classified are on the CEFAS website.

More information on shellfish classification is on the Food Standards Agency website.

Flesh and sea water samples are collected as part of the Food Standards Agencies Biotoxin Monitoring programme.

Marine biotoxins are poisonous substances which can accumulate in the tissues of live bivalve molluscs. This can be as a result of feeding on biotoxin producing phytoplankton.

There are currently three groups of regulated biotoxins for shellfish. These can cause:

• Paralytic shellfish poisoning (PSP)
• Amnesic shellfish poisoning (ASP)
• Diarrhetic shellfish poisoning (DSP) caused by lipophilic toxins

The process of monitoring marine biotoxins identifies if there is an increased risk of shellfish becoming contaminated. It allows businesses to take appropriate steps to ensure the shellfish they are placing on the market are safe to eat. When biotoxins in shellfish are detected over the legal limit we take action to ensure the affected areas are closed for harvesting.

Shellfish registration documents are issued to commercial fishermen who meet the relevant standards to enable them to transport their catch to processing plants. All batches of shellfish must be accompanied by a registration document from the point of harvest until its destination.

Registration documents can be obtained from the Port Health Office 023 8022 6631 or email port.health@southampton.gov.uk

It is not recommended to eat shellfish especially bivalves (mussels, oysters, clams, razor etc.) that you have collected from the seashore.

The bivalves bought in the shops are supplied from areas that are strictly controlled by the Food Standards Agency. This ensures that the shellfish are free from contamination and that the bivalves have been depurated before they are sold.

Depuration (the process of purifying) enables the shellfish to purge themselves of toxins in a highly controlled environment.