This was copied from the AGFC trout newsletter....
We conducted our annual electrofishing sample in Dry Run Creek on August 8th. During the sample, we collected several large fish with what appeared to be angler-made notches in their tails (see attached picture). We have heard of folks doing this to "mark" trout as ones they have caught previously. We strongly advise against the practice of doing so. Injuries of this nature can cause infections in the fish and ultimately lead to their death. The additional stress of handling and clipping can also negatively affect the fish. Please leave trout marking up to us, which is typically done in a controlled setting, while fish are sedated, and their condition is monitored for several weeks prior to stocking.