theres no need for a permit although some species are protected and must be put back in the water with as little fuss and damage as possible. I think Ruffe come under this.
WITHOUT WISHING TO APPEAR RUDE, OR JUDGEMENTAL, IT IS IMPORTANT, THAT THE FOLLOWING COMMENTS ARE TAKEN ONBOARD.
YOU WILL FIND THIS QUOTED INFO TO BE WRONG, IN EVERY REGARD, OTHER THAN THE REFERENCE TO PROTECTED SPECIES, OF WHICH THE RUFFE IS CERTAINLY NOT ONE, CONSTITUTING A MAJOR MENACE TO ALL OTHER SPECIES DUE TO EXPLOSIONS IN NUMBERS, AND SEVERE EGG PREDATION UPON OTHER SPECIES.
CHECK OUT ANY SCIENTIFIC LITERATURE ON LOCH LOMOND, AND YOU WILL REALISE THE DEPTH OF FEELING DIRECTED AGAINST THE INTRODUCTION OF RUFFE TO THE CATCHMENT.
A ROD LICENCE TYPE OF ARRANGEMENT HAS BEEN INTRODUCED RECENTLY, IN ORDER TO CONTROL FISHING FOR ALL AND ANY SPECIES WITHIN THE LOCH AND SURROUNDS.