GuyFromLaw spot on !
In low clear water I have come across salmon taking short or simply just following the fly with half hearted takes..the best induced method in my opinion is the 'riffle hitch' fishing the fly on the surface as a wake fly . hard solid no nonsense takes !
more about that at ..
A GHILLIE'S TALE
Basically dragging the fly across the surface..pattern is irrelevant it's the wake created by the drag in the line that attracts...
Standard practice with salmon ..feel the fish take and allow him time to turn down and begin running back to his lye..then pull into him or if he stops pull into him.
To aid in timing the strike pull a length of line 6-8 feet from the reel after the cast is made and allow it to hang as a loop at your side trapping said line gently beneath your finger and rod handle [as you would when retrieving].
Fish takes allow him to take the loop then lift into him.
Takes are often quite confident as the fish feels no resistance until the actual strike.
Fish actually rises to the fly strike before you feel him ..it works !
A fish that slaps the fly as with trout wants to take it wet ie:drowned see this happen don't strike-the fish will turn and come at the fly with confidence...but you must hesitate the secret is to give the fish a few seconds to turn once he has taken the fly..
John