the hand fishing would only impact a certain area or areas, like small streams, slow flowing rivers, and human nature being what it is, it would be over fished and these areas would no longer be able to support a population of fish to catch. big lakes, it would be hard to over fish the deep water areas, feeder creeks would get hurt the worst. on the big rivers, I do not think there would be a problem on fish populations, but alas I am not a fisheries biologist and my two cents is worth only a lick and a promise.