can't say as I've ever heard of Crappie being "salad eaters" ... perhaps they are eating some type of aquatic critter that's IN the algae ??
How's the Shad population ? If there's been a big die off, like what happened in the Big Sandy area recently ... then maybe they are just subsisting on what they can.
Have you noticed the supposed transition of dominance, from White Crappie to Black Crappie, on Barkley ?? ........ cp