Sounds like to me they might be staging themselves. Guess they could go either way depending on conditions. Deeper channel nearby or on up into shallower water to spawn. Keep an eye on them and see if they don't start stacking up more and on more of the brushpiles as the water temp gets into the upper 50's. Don't make the same mistake I did several years back watching the surface temp in the main body and around the staging areas and not checking the skinny water. It may only be in the upper 50's at the deeper staging areas when it is already well into the 60's in the skinny water spawning areas. It won't be long.