To improve things, if the fishing needs to be C&R ... Then just make it C&R ... don't fool around with coupons and adult fish, slot limits, etc ... If you have a fish out of the water for more than a quick picture ... fine them $200 per fish and be done with it.
Here in Michigan on the Pere Marquette River there was an area of "quality fishing" where you could keep one fish (Salmon or Steelhead) per day ... more than once I saw guys walking out with a fish ... only to be back on the river fishing five minutes later after putting that one on ice in the trunk of their car. They have now made the area flies only / C&R ... you can not have any fish in your possession or the DNR will give you a ticket. Guess what ... no one takes any fish from the area. I love it ... Oh did I mention I was a C&R fisherman ... I haven't kill a fish in years ... Love 'em and Leave 'em