Cockle picking is a long-established and traditional industry.
The industry is a draw for casual workers
In Morecambe Bay, local people have long used the beach for fishing, but there has recently been an influx of outsiders hoping for rich pickings.
The beach opened in December for cockle picking and there are more than £6m worth of shellfish to be collected.
But locals have complained that people have flocked to Morecambe Bay, eager to get their hands on the lucrative cockles.
The industry is a draw for casual workers - and the rewards can be good. It has been reported that cockle pickers can earn up to £500 a day.
Mark Swiston, the managing director of the Penclawwd Shellfish Processing in south Wales, said the cockle industry is worth about £4m in his area.
The cockles are exported to Holland, where they are processed, and then shipped on to Spain.
"I'd say 90% of our trade is for export and 10% is local trade," he said.
"I'm the fifth generation of my family in the cockle job. We are probably the biggest producer in south Wales. No-one is earning £500 a day.
"I know fishermen who go elsewhere and they could possibly have earned £100 a day. You can earn as much at home.
"The Dee Estuary was open last year but that was short lived - it was only open for nine days. It might have been achievable to earn £500 then."
Cockle picking in England and Wales is regulated by 12 local Sea Fisheries Committee. They monitor stocks, control raking and dredging and issue licenses and permits.
Traditional areas include Swansea Bay, the Burry Inlet, the Dee Estuary, the Wash, the Thames, Morecambe Bay and the Solway Firth. There are also cockle fisheries in sea lochs around Scotland.
The Dee Estuary in Merseyside was opened for just over a week in July last year.
The industry in the Morecambe bay area is regulated by the North Wales and North West Sea Fisheries Committee, which has introduced permits to collect cockles in the area.
In December, cockle beds on the coast of Lancashire were re-opened. So far 815 permits have been issued.
Robin Bamber, from Bolton le Sands, said there could be up to 300 cocklers heading out onto the sands at a time.
He said: "Part of the reason that people come here is because they were cockling at
the Dee Estuary and the bed got closed because of a disease in the cockles, so
they had to find somewhere else to come."
However, Morecambe and Lunesdale Labour MP Geraldine Smith said there had been concerns about unregulated fishing activities in the area for some time.
She told the BBC that although cockle picking on the beach was supposed to be regulated, it was impossible to police.
She said: "Morecambe Bay is a public fishery, so basically once the cockle beds opened in December anyone can go down to that beach and fish for cockles.
"People were supposed to have a permit and they would turn up and give their
name and address and National Insurance number.
"But obviously if people go on to the beach and aren't part of the permit scheme, it is virtually impossible to impose.
"You can't stop people turning up and going on the beach at eight o'clock on
a dark winter's night, especially as there was about £6m worth of cockles
just lying in the middle of Morecambe Bay on the beaches."
Residents in the area have long been concerned that groups of un-licensed pickers have been combing the beach.
In August 2003, immigration officials launched a crackdown on people working illegally as cockle pickers.
More than 200 officials and police swooped on cockle beds on the River Dee.
It followed a similar operation in Morecambe earlier in the month, in which 37 suspected Chinese illegal immigrants were detained.