One of the main problems is the stock used for sampling comes from the lays up Mylor Creek and is given to Port Health who replace each bag at each Remote Monitoring Point for the next samples and so on, the bags are suspended in the top 2m of seawater that is usually the fresh water and usually the dirtiest, samples are deck washed before going into sealed bags in a cool box and sent off the Porton Down who test all the 67 sites in the South West, it takes 7 days to get the results. Sample sites must be 90% compliant with the classification. The Shellfish Harvesting Waters Classification Sampling is eactly that and NOT a Food Standards Rating for end product consumption. 

BBC News "More shellfish testing following 'devastating' ban

• 3 October 2014

Plans to revamp the testing regime which monitors water quality and the cleanliness of the shellfish in Cornwall have been announced.

One proposal is to temporarily halt shellfish harvesting when heavy rainfall is predicted.

Water testing in the spring forced the closure of the Fal mussel fishery and a high reading for E.coli in July left the oyster fishery under threat.

Some mussel harvesting has restarted and the oyster fleet is working again.

Chris Ranger, an oyster fisherman in Falmouth, said: "To be told in July you can't harvest was devastating.

"I'm a food producer. I would like to know before there's a high risk."

Ahead of the start of the season the oysters are cultivated and reared in the Fal.

The oyster season itself runs from October to March.

A shellfish flesh sample from Mylor, near Falmouth, in July contained levels of E.coli bacteria 300 times more than that permitted by the Food Standards Agency.

As yet the cause remains unexplained.

The Port Health Authority - which is responsible for the testing regime - said at the time it hoped it was a one-off.

The authority said it had now increased tests in risky areas.

It also hopes to use rainfall predictions to temporarily halt production when there is the greatest risk from run-off and sewage overflow.

David Robertson from the authority said: "It will reduce the amount of guesswork.

"As we've only taken samples once a month it's been unknown what the state of the river is at other times."

Fal oysters are said to have a distinctive sweet, fresh and delicate flavour and are popular with chefs in restaurants around the UK."