Females will definately have a bulge. During the peak of the spawn, they sometimes even "drip" eggs out. Males are usually darker than females especially when they are on the bed. Coloration has a lot to do with location too. On Reelfoot male white crappie can get so dark they look purple. You may notice too that males will have frayed and sometimes bloody tail fins from fanning. I still occasionally get a surprise when I cut one open.
You'll get a hundred different opinions on "responsible" management. My personal code is to take only what I'll eat and stay within the legal limits. Some days I put em back- some days I don't.
It's fun to get the younguns on some fish for sure. I've got a 4 year old nephew I'm training. He has the story telling part down already. :D