On Thursday, August 2, 2012 5:34:13 PM UTC+8, M wrote:

. . . I'm fishing river for wild brown trout. So far I'm catching small
fish no more than 7" in length.
. . . The only time I catch on wet fly is when I'm retrieving at speed. I
have never yet caught by
casting up stream (and taking up the slack as the fly returns),
. . . it's quite possible I'm getting takes but never see them?

This is normal for beginners inexperienced in detecting the trout's
taking the fly. This could be by sight (the "wink under water") or
by touch -- because, notably, when you are retrieving there is no
slack in the line so you feel a take instantly.

Authors who have written usefully about this include Oliver Kite,
James Leisenring and Ray Bergman. But you may get good
advice from local anglers if you approach them the right way.

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)