Cocklers have gathered to work at Lafan Sands, in north Wales

The 14 arrests were made as the cocklers left Lafan Sands at Abergwyngregyn, near Bangor.

Police staged the operation to check that those doing the cockle-picking had licences to do so.

Scores of Chinese cockle pickers have arrived in the area over the last 10 days.

Police officers set up road blocks near the A55 exit, and a police helicopter was also used in the operation.

Groups of up to 90 cocklers have been working at Lafan Sands, with fisheries officials believing they have moved to north west Wales after a cockle bed in Morecambe Bay was closed down to preserve stocks.

A force spokesman said 25 officers took part in the operation, which started at 0800 BST.

The immigration service and vehicle inspectorate were also involved.

"This area is made up of large sandbanks, which have deep channels running through them," said the police spokesman.

"The tide flow in the area is quick-flowing, which rapidly turns the banks into a perilous place for persons unacquainted with the area."

Police and immigration officials stopped three vehicles containing 70 cocklers

The force said the operation "was aimed at disrupting gangmasters who are involved in the passage of illegal immigrant workers".

An unfit vehicle was also seized and a person was arrested for driving while disqualified.

The statement added: "Police are particularly concerned about the increased activities of gang masters operating illegally, exploiting vulnerable groups of people.

"Past incidents have highlighted violent situations where there has been clear conflict between competing parties.

"Such parties visiting north Wales in the future can expect close police attention as both their personal safety and protection of the environment is of primary concern to us."

There have also been concerns for bird habitats, with Lafan Sands designated as a site of special scientific interest, as a feeding ground for up to 4,000 oystercatchers.

Inspectors, who have been monitoring the situation, say the cocklers have not breached any fisheries regulations.

Cockling became more intensive in the north west of England at the end of 2002, with the issue coming to wider attention after the tragic drowning of 21 Chinese cocklers at Morecambe Bay in February this year.

Bodies of two other cocklers still have not been recovered.