Jackie you totally had it right. This is what I read about them...
"White suckers spawn from April to early May when they run upstream, usually starting at night. They seek areas with swift water and a gravel substrate to randomly spread their eggs. Females can lay between 20,000 to 50,000 eggs. The young hatch and remain in the gravel for one to two weeks before migrating downstream at night. Larval white suckers feed on protozoa, diatoms, and small crustaceans. As the young grow, the mouth moves to the underside of the fish and allows the fish to feed on the bottom."
That creek (and every aquarium I own) is LOUSY with diatoms and scuds (lil shrimp thingies). Cool!