Notices have been erected along the estuary warning people cockle picking has been banned.
The one at Newcastle University's farm, Cockle Park, in Morpeth, Northumberland is the most north-westerly in Europe.
The cockle bed at Foulnaze, near Lytham, attracts about 600 cocklers a day.
Half of the island is a national park, with Picnic Bay, Cockle Bay and Rocky Bay among the major attractions.
BBC: SPORT | Rugby Union | Rugby World Cup | Venues Guide | City guide: Townsville
In July hundreds of fisherman returned legally to the Dee Estuary when the cockle beds were opened for three days.
BBC: NEWS | UK | Wales | North East Wales | Night clampdown on cockle pickers
"We are working with all the relevant enforcement agencies and the main cockle buyers to address these concerns, " said Mr Winstone.
The coastguard agency has dealt with 23 incidents involving cockling in Lancashire's Ribble estuary since its cockle beds opened in September.
He also made the extraordinary assertion that a restrictive immigration policy would help downtrodden illegal immigrants, such as the Morecambe Bay cockle-pickers.
Before that, cockle picking had been suspended for two years on the Dee Estuary because of a decline in numbers of the shellfish.
BBC: NEWS | UK | Wales | North East Wales | Night clampdown on cockle pickers
Cockle beds in all parts of the Three Rivers estuary in Carmarthenshire have been closed because of "significantly high" levels of E. coli.
Six hundred licences were issued for Thursday's harvesting but the agency confirmed there would be no further cockle fishing in the Dee Estuary this year.
On about 1% of the Thurstaton bed there is a "large quantity of algae which appears to have caused high cockle mortalities, more than 90%".
In October last year, cockle beds on the Swansea side of the Burry Inlet were temporarily closed after shellfish samples tested positive for E. coli.
It was set up in the wake of the 2004 Morecambe Bay cockling disaster, in which at least 21 Chinese cockle pickers drowned in rising tides.
But Councillor Patrick Heesom, who represents the Mostyn area of Flintshire, said allowing so many cockle pickers out on to the beds is "a recipe for chaos".
BBC: NEWS | UK | Wales | North East Wales | Cocklers descend as ban is lifted
The Gangmasters Licensing Authority (GLA), a statutory watchdog, was set up in 2005 following the drowning of 21 Chinese cockle-pickers led into dangerous waters by their boss.
Hundreds of licences were issued to the cocklers but the environment agency confirmed at the time that there would be no further cockle fishing in the estuary this year.
BBC: NEWS | UK | Wales | North East Wales | Night clampdown on cockle pickers
No matter how it began, today the 189sqm of mosaic grotto is a chance to gawp at the 4.6 million cockle, mussel, oyster and whelk shells festooned in elaborate mosaics covering every surface.
应用推荐