I tried circle hooks for my Pike flies...and lost just about every fish.
The trouble with circles is that they were originally designed for commercial tuna fishing with longlines.
With a standard hook, the tuna would swallow the bait and the hooks would stick deep down, sometimes causing bleeding and the death of the tuna before it could be brought onboard. A dead tuna is worthless. Also, the hook would be difficult to retrieve, and when the longliners have 2000 hooks to deal with, it would take hours to sort.
Circle hooks are still taken deep, but they do not catch into anything until the fish swims off. As it swims away and the leader tightens, it drags the hook out of the throat of the fish, it then flips over as the line is pulled across the corner of its mouth, and digs in. The hooks always ctch in the scissors, This way the tuna stays alive longer and the hook can be retrived for the next "shot".
So, for a circle hook to work with a fly 100% of the time, the fly would have to be taken deep, and then the line held tight so the fly comes back up and flips. Also, it would need to be independent of the tube to work properly.
Circles will catch, but certainly from my experiments with them, they are not the answer.
