There are calls to ban cocklers from a wildlife site near Bangor, Gwynedd.
The four-wheeled motorbikes are damaging the area say the CCW
The Countryside Council for Wales (CCW) are increasingly concerned the cocklers are damaging Traeth Lafan with the use of four-wheeled motorbikes.
The CCW has written to the North West and North Wales fisheries committee asking them to close the beds.
One fisherman refuted the claim on the effect on wildlife but said there were more cocklers this year than in the past.
"The damage caused by the quad bikes is quite serious and we have written to the sea fisheries committee to close the cockle beds so that transport can be discussed," said Helen Evans from the CCW.
"The mud flats are of international importance particularly for the oyster catchers and of course the quad bikes are churning up the mud which is an important habitat."
Local people claim up to 100 cocklers, many from eastern Europe, can be seen at the beds at any one time, working both day and night.
Gwynedd county councillor John Jones said he was "disgusted" at the mess they were making.
"This is supposed to be a nature reserve for people to enjoy.
"Who's going to foot the bill for clearing up this mess?
"There are no public toilets here, and you find them relieving themselves in public."
A spokesman for the North West and North Wales Fisheries Committee said they consistently monitor the activities at Traeth Lafan.
The cockles are fetching a good price say fishermen
They had agreed an appropriate route for the cocklers to take out to the beds on their quad bikes which should not affect birdlife, said their spokesman.
"The harvesting has not had a detrimental effect on the beds," he added.
One of the cocklers, John Bellfield from Llanfairfechan, said he could not see how collecting the cockles could damage the wildlife.
He said it was up to individuals to be careful with their rubbish and skips had been provided for any refuse.
Mr Bellfield warned however that some of the cocklers from outside the area were not sorting the cockles out by size whilst they were out at the beds, leaving smaller ones in the car park instead.
This could affect the beds next year and even the year after, he added.