Basically the Piddle and Frome will be 'owned' waters, either by private or club owners. You have to draw a line somewhere, and the tidal influence makes no difference- clay pool in xchurch is a good example of this.
Yes, they are trying to stop illegal fish removal, ie Sea Trout etc, but more importantly, someone is paying to fish / own the water, so people encrouching and fishing illegally are not welcome.
Anyway - since when has using nets become 'fishing'!!!!