Suspected black market activity in stolen shellfish is raising fears that people may be poisoned.

A spate of thefts from valuable oyster beds, and from marine sources of mussels, scallops and clams, is alarming Port Health Authority experts who regulate one of Cornwall’s oldest traditional industries.

Port health officers believe the scale and frequency of reports and incidents indicates organised black market activity.

This may also have been driven by disruption to normal supplies caused by the coronavirus lockdown.

There is an open investigation into shellfish taken from the Helford on July 6, but there has been an upswing in intertidal beach and estuary ’poaching’ across the south west.

The illegal gathering of shellfish risks serious food poisoning for consumers and goes against conservation efforts to control stock sizes and quality.

Cornwall’s port health manager Tim Bage said: “From a food safety point of view, most people aren’t aware that most of our shellfish goes through a purification process to purge out unwanted bacteria which otherwise could cause very nasty food poisoning.

"The areas that are classified are those where shellfish and water quality are monitored for bacteria levels or dangerous toxins.

“If harvesters operating illegally sell on stock from unclassified areas there is a genuine risk of toxin poisoning, since these are not reduced by cooking, and the results can be extremely unpleasant.

“Additionally, by taking undersized stock they are undermining the viability and sustainability of a fragile Cornish seafood product.”

Read more: Fal Fishery Cooperative ready to start hatching 1,000,000 Cornish Native Oysters

Poaching is happening in unclassified, as well as private areas.

Rob Nolan, Cornwall Council’s cabinet member for environment and public protection said: “We would strongly advise people to check that the area they are harvesting in is classified for the species they are collecting.

"Additionally, they are encouraged to ensure they are allowed to take from the area, because to take from an area with a private lease is deemed an act of theft.”

Whilst picking shellfish from foreshores is allowed only for personal consumption, the quantities being taken recently suggest harvesting at a commercial level.

Port health officers are asking the public to be their ‘eyes and ears’ on their behalf to protect Cornish shellfish.

If you are suspicious of any shoreline gatherings of large groups, please contact Cornwall Port Health on 01872 323090 or email with as much detail as you can on the location, and any vehicles used by the gatherers.”

There is no accreditation scheme for shellfish, but restaurants, cafes and fish mongers are strongly advised to buy only from reputable sources that they can verify.

Shellfish bought at retail level should normally carry a health mark (an oval).

Some direct boat-to-retail trade is permitted on a small scale, but please contact Port Health to check that any supplier of bivalve shellfish is reputable and operating legally.