I agree with Hamish, im not sure i like the cat 1 classification.
How many rivers can really sustain the 'take as many as you like' classification ? And how does this look to the public ?
Now, on highly managed rivers like the spey and findhorn , despite the cat 1 status i cant see people chapping everything - as the gillies have an eye on what is going on.
On less managed rivers i think it is a different story.
lets face it - you should not need to take more than 2 to 4 fish a season for personal consumption.
When the don was in much better fettle i would take 2 fish (6-7lbs) a season for cold smoking and that kept us very well supplied.
lets move to carcase tagging with a limit set per person per river per year
im not sayign that it would stop the fishmongers, but it would make life a lot more difficult for them