freezing is extremely painful to fish. fish do not fall asleep like humans do. their cells crystalize causing extreme pain. it is also illegal in some states to freeze fish as it is inhumane. same goes for flushing down the toilet.
Dropping them in boiling water works on small fish (2 inches or less). I use clove oil to knock them out and then put them in a bag with the clove water into the freezer. Works like a charm. Or a quick chop to the head. I prefer clove oil.
You will find that there are many ways for many people to define "Humane" But generally everone sides on the "Humane" Side that causes themselves less pain.
sorry, im not trying to sound like a know-it-all. i just happened to read an article about this 2 days ago. i think i might have found that thread here.