I fish egg patterns behind the redds and catch the fish waiting for the eggs to drop. In my experience the spawners wouldn't hit since they have sex on the mind. However, casting to them can spook them and keep them away from the business at hand and you run a risk of snagging fish on the redd. However, there are usually plenty of non-spawning fish just below the beds. The stocked rainbows are tricked into fall spawning at the hatchery and you can see some spawning (or trying to spawn) in Sept and Oct. I fish behind these fish a fair amount, but leave the wild brown and brookie streams alone at spawning time, or maybe go just to watch how the spawn is going.