I know where you are coming from with that Johnny and I realise I didn't word my post particularly well in relation to licences for catching non native crayfish in Scotland.
An order made under the Import of Live Fish (Scotland) Act 1978 makes it an offence to keep or release non-native crayfish. This means that it is / would be an offence to trap non-native crayfish without a license (as they would then be in a persons possession).
However licenses are not as a rule provided for this purpose and illegal harvesting is one of the main causes of spread of crayfish. The problem legally and ecologically with people trapping and eating crayfish is that some then think it's a good idea to introduce them to new ponds and streams so that they can do the same!
Sadly even among our own community not everyone has ecological morals.
not to kill all crayfish johnny,just the invasive signal crayfish i think youll find mate...we want to keep all our indigeneous ones