I fished often when I was young, but then gradually stopped. I was thinking of fishing again, but now I am a little put off thinking that the fish are feeling pain from a hook. Is there scientific evidence for or against?
There is evidence for fish feeling pain. Obviously you cannot simply say they do feel pain, only that we can observe behaviors that could be consistent with them feeling pain, and that they have the physical chemical receptors to facilitate a pain signal.
A 2010 book by Victoria Braithwaite titled Do Fish Feel Pain argues that the "latest scientific evidence suggests that we should widen to fish the protection currently given to birds and mammals." I didn't buy the book, but this would suggest that her research indicates that they do. After all we wouldn't widen protection for animals that don't feel pain.
Her 2002 article on the matter also suggests they have pain-like feelings.
Whilst we agree with the author that fish are unlikely to perceive pain in the same way that humans do, we believe that currently available evidence indicates that fish have the capacity for pain perception and suffering.
A 2003 article by Lynne Sneddon states
Recent anatomical and electrophysiological studies have demonstrated that fish are capable of nociception, the simple detection of a noxious, potentially painful stimulus and the reflex response to this.
Administering morphine significantly reduced the pain-related behaviours and opercular beat rate and thus morphine appears to act as an analgesic in the rainbow trout. It is concluded that these pain-related behaviours are not simple reflexes and therefore there is the potential for pain perception in fish.
As for the impact this is going to have on your angling, I can't say because I'm not much of an angler. Perhaps consider numbing tipped barbs or something similar. But the actual equipment selection is the scope of another question.