A highly lucrative underground trade in shellfish is putting the health of consumers at risk with tonnes of potentially contaminated seafood feared to be entering the food chain. That's the worrying finding of a joint investigation by The Ecologist magazine and The Independent newspaper.
Our probe into the illegal harvesting of clams, cockles and oysters - amongst other fish - for sale to restaurants and wholesalers has alarmed health officials and fisheries protection bodies who say they lack the resources to effectively tackle the problem.
Highly organised gangs, some operating directly on behalf of fish merchants, others run by gangmasters, have targeted shellfish stocks in Sussex, Hampshire, Dorset, Merseyside, Lancashire, Cumbria and Teeside. Parts of north Wales and Scotland have also been affected.
The gangs target known shellfish beds at day or night, depending on the tides. Many arrive in transit vans or 4x4 vehicles and, using spades - or in some cases small boats fitted with dredging equipment - extract the lucrative molluscs before transferring them to chill boxes.
From there, the shellfish are delivered to waiting merchants, or are offered for sale speculatively to traders, to restaurants or even via the internet. Some of the shellfish end up in markets for sale to the public, but most is thought to pass through processors or wholesalers who in turn sell to restaurants, pubs or other caterers, or export it abroad.
It is a highly lucrative trade with a tonne of clams fetching up to £1,000 (although prices have recently fallen). In a two month period last year, cockles worth some £6m were harvested from the Dee estuary in the Wirral.
Legitimately gathered shellfish are subject to strict purification treatments to ensure they are fit for human consumption, but fish taken from prohibited or unclassified sources, or sold before being properly treated, put the public at risk of serious illnesses caused by the E.coli, novovirus or salmonella bugs, which can all be found in contaminated molluscs.
In 2011, a deadly E.coli outbreak - first blamed on cucumbers, later linked to German grown bean sprouts - killed at least 22 people and poisoned more than 2000 across Europe.
Strict rules are supposed to ensure traceability of any consignment of shellfish moved or sold on a commercial basis, with each batch accompanied by appropriate paperwork. But our investigation established that in the event of a major health scare officials would be unable to verify the origin of some shellfish because of the illegal trade, undermining efforts to pinpoint the source of contaminated produce.
One police officer working with the Environment Agency to tackle the problem said the major concern was that cockles gathered illegally could be mixed in with legitimately caught shellfish: 'It's like the E.coli case [with beansprouts], in the event of a health scare, the cockle industry would have no idea where some of them came from.'
Last year, research by the Food Standards Agency found traces of novovirus - or winter vomiting bug - in more than three-quarters of shellfish tested from UK beds, much of which is eliminated by treatment and cooking.
In 2009, the Michelin-starred Fat Duck restaurant, owned by celebrity chef Heston Blumenthal, was forced to close after more than 450 people fell ill with norovirus. Raw oysters and clams were later identified by the Health Protection Agency as being the main source of the contamination. (There's no suggestion shellfish from unlicensed sources were to blame).
The Health Protection Agency says that at least 163 food poisoning outbreaks recorded between 1992 and 2010 were linked to shellfish. And it pointed to research published in the journal Emerging Infectious Diseases in 2005 which claimed that more than 77,000 cases of food-borne disease were linked to consumption of shellfish between 1996 and 2000.
According to those involved in tackling the illicit trade, much of the blame from the growing problem lies at the squarely at the feet of unscrupulous fish dealers happy to take shellfish on a no-questions-asked basis. Whilst the market is there, the gangs involved are going to exploit it, say enforcement bodies.
Recent months have seen a stepping up of action to thwart the gangs involved in the trade. Only this month the Gangmasters Licensing Authority, the body set up to regulate and enforce the shellfish picking trade in the wake of the 2004 Morecambe Bay tragedy which claimed the lives of 23 Chinese cocklers, completed the successful prosecution of two gangmasters who were illegally organising shellfish harvesting in on the Isle Skye and Merseyside. And there's more believed to be in the pipeline.
But there's much still to be done. And in the meantime, consumers might be wise though to ask where their clams, oysters - or other seafood treats - come from before tucking in.
Follow Andrew Wasley on Twitter: www.twitter.com/@the_ecologist