Bluegill

As stated, it's a young Bluegill. You can already see the dark gill spot developing. While White Crappie also have this spot, the mouth doesn't extend back to the eye as it does with crappie and there are more then 6 dorsal fins, which rules out White Crappie. They look healthy for young fish. BG won't generally start to fill out until they get larger, IMO, due to competition for food at that age.

EDIT: Also, they are probably last years hatchlings, and some of the larger ones even from the year before.

They do make good bait for crappie when they're 1-2 inches long, they can be quite a bit larger and be good bait for bass. Make sure to use a small, light wire hook when you're crappie fishing because they will die very easily if you use to big of a hook.

What size hook....like a #2 alberdeen?

I like octopus style hooks because they are thin and short so the bait looks very natural. If I'm fishing only for crappie I'll use a #6 or even a #8, it doesn't take much to hook and hold a crappie. If you're fishing a bigger bait or where you might come across a big bass I'd probably go with a #2 or 1/0 assuming you're fishing light tackle that won't straighten a small hook.