oK, iAM NOT SOCKEYE SPECIALIST, BUT i caught a couple 2 years ago on the Sol Duc from a drift boar. we were pulling small blue spin-a-glo's with sand shrimp.

Bang, fish hit the hooks hard, drove the hook from inside the mouth up thru the eyeball.

Jim, the guide, rowed back up and bang again, same spot and a 2nd fish, in the mouth. lines straight below the boat. Did have a bait diver to wiggle the shrimp, but these 2 definately hit the bait.

Now as to what happens, just look at chums in shallow water. They always have their mouth opening and closing, due to the fact of the change in water, from salt to fresh, they have trouble breathing enough oxygen out of fresh water, so they gasp.
I know every one has seeen a chum bite, but also most have seen a chum line itself onto a hook. If the mouth is open, well it will go into the mouth and set the hook, viola a good hit.

It is not rocket science, yes some due, at times,*******************************************************

Like I said at the top keep it to whether or not sockeye bite, J. Garcia.