How about trying to catch the American Crayfish if you are that hungry:
The law surrounding the trapping of crayfish is very strict. This is mainly due to the Seventies crash of imported farmed crayfish when many North American crayfish escaped in to native waters. Our small white-claw crayfish have been threatened ever since, as the intruders are bigger, stronger and breed faster, and they brought associated plagues to which native species are highly susceptible.
In June 2005 the Environment Agency (EA) introduced a list of crayfish by-laws that, under certain conditions, would allow the trapping of non-native crayfish in England and Wales. No one is allowed to trap native crayfish, only the larger “alien” varieties. Any fisherman who catches an alien crayfish must kill it rather than return it to the water.
You need a licence, which is free, to trap crayfish and your local EA needs to know exactly where you will be setting your trap. Permission will be dependent on the situation and the EA will take in to account the possible effect that trapping could have on other species. As many water courses run through private property it would be your responsibility to obtain permission from the landowner before you start. All traps must be inspected every 24 hours.
Give this ago, you'll be doing us all a favour.
Michael