If the spawning beds are shallow enough to see the fish, you should be able to see the red ear tabs - whether the water is clearer like ewest's or kind of cloudy like mine.
See here for examples. FWIW my RES were on those shallow nests for like 3 weeks, and I don't THINK I lost any to the local GBH. Certainly my redeared friends Bob, Ted, Phil, and Yellow 032 made it through spawning AOK.