Netting a river fish, where the scales have likely set pretty good, does them no harm, and actually is easier on them than tiring them out enough for them to be tailed or hooked by hand, or even dragged up on the bank. Ocean fish are another thing - those scales fall off real easily and it's best not to touch them unless you have a net built for C&R. You can build one of these easily enough - get some soft nylon 1/4 inch "smelt" mesh and sew up a bag. Keep it wet and you can net and release fish with minimal scale loss and without wearing them out.