The Ministry for Primary Industries seized more than 10,000 cockles from a group of illegal harvesters. Pictured are approximately 2000 cockles.

More than 10,000 cockles have been seized from a group in Canterbury in what authorities say is the largest illegal cockle haul in recent memory.

It took four Ministry for Primary Industries (MPI) officers more than an hour to count the cockles, which had been harvested by eight people near the settlement of Waikuku beach.

The people involved were from Christchurch.

They were stopped by compliance officers on Monday after a tip-off from the public. Officers discovered 10,500 cockles stuffed in bags at the back of a van and a sports utility vehicle.

The daily limit for recreational cockle picking in Canterbury is 150 per person.

MPI was interviewing the individuals on Thursday. They could face charges after it completes its investigation.

MPI Canterbury/Westland compliance manager Peter Hyde said his staff could not recall a larger haul.

"It's nothing to celebrate, as shellfish beds can't take this sort of pressure for long," he said.

"We are delighted to get a timely tip-off from the public as the illegal activity was happening, and this allowed us to apprehend these people."

He said fishers were obligated to know the rules for the area they were fishing.

Cockles are small shellfish found in estuaries and mudflats, and are abundant in many areas of the country.

Limits are enforced on picking cockles to prevent over-harvesting.

MPI encourages people to report any suspicious fishing activity to 0800 4 POACHER (0800 476 224).