loud noise will scare fish fast. if you can be quiet or whisper, you have a better shot of catching any fish that come near you.
be extra careful when you wade through the water. when wading through a river and fishing, walk carefully. this will not only keep you safe, but it will also help prevent you from making noise that will frighten the fish away. try not disturbing the river bed and be patient.
if you want to return the fish that you caught to the water, and are worried about having a souvenir to take with you to show people the prize you caught you should take a camera. 