#1. Regulate that they must be left in the water?

No. First, I think it would be too hard to enforce, but more importantly, I don't think that it's a good idea. Fish, gear, river, boat, and fisherman include 100's of variables, and sometimes they line up that netting a fish is far better than anything else.

#2. Type of net?

Absolutely. This is an easy one...use a knotless mesh, of a small size. Small size spreads the impact of the net on the fish out, like the difference between being stepped on by a size 15 shoe or a size 7 high heel, with the spike end. Additionally, cnr basket nets are pretty easy to use, and really effective.

Fish on...

Todd.