http://www.nytimes.com/roomfordebate/2010/08/08/should-fly-fishers-catch-and-always-release/the-fish-feel-little-pain
I personally am a barbless, fast fight/quick release, small-medium fly, thermometer carrying guy. I fish with lightweight gear and cut off embedded flies, etc. But I think it would be easy to overestimate the angling threat to the small brook trout that live in infertile PA mountain streams. Fishing pressure is typically not high, and its threat is probably a fraction of the high annual rates of natural mortality in such environments. So habitat, more than our visits, determines populations. And big picture, the only thing that is really unethical is lip-synching the national anthem, uh just kidding...