Sounds a lot less lethal, throat pump V stomach pump. There are times when sampling a trout's throat does give the fly fisherman an advantage. Ethical, harmful, no harm, legal, proper? Let your conscience be your guide.
I have to wonder if studies on resulting mortality have ever been done.
Also proper? and improper use guidelines.
I guess there's always the good old fashioned 'gut one and keep it' method where allowed.
Seriously, I think discussing this is a good topic that goes along with c&r and proper handling.