There have actually been quite a few interesting findings in the last year or so indicating that fish *do* in fact feel pain..
http://news.bbc.co.uk/1/hi/sci/tech/2983045.stm
Good article, indicating that not only do the fish exhibit physiological effects from pain (modified chemical receptors, etc, similar to humans), but they also will exhibit modified behaviors based on pain stimuli..
I still eat fish though.
hmmm.