Went to Union Saturday for a look around - didn't see much of anything but some small rises which may have been crappie or bass off the boat ramp.
Like fishfiend saw at Douglas, these small shad (in photo) were in certain places on the shore and sometimes swimming about close to shore. Last time I boated Union before it closed to boating, I saw many many balls of these baitfish on the fishfinder. Which leads me to believe there's a shad boom on Union. They're about an inch and a quarter long.
I took this pic with the intent of tying up some fly imitations. Rob at Rocky Mountain Anglers beat me to it, and has tied up a nice imitation - stop in and see them in Boulder when you can to check it out.