They've got "noses" (well, actually "nostrils" ).... so yeah, they can smell. I believe they use their sight and vibration sensing lateral lines, first & foremost, but they can definitely smell/taste through their nostrils.
I don't know as there has been any "scientific studies" about Crappie & their ability to smell or distinguish good smells from bad, as it were ... but, a Google search for "can crappie smell scientific proof" did offer a few articles that were interesting. I particularly liked the In-Fisherman article, the 1948 School for Fishermen, and some of the Google books pages.
JUST IGNORE the "old school secrets" link ... he's just trying to sell DVD's (and you can get better info, right here, for free !! ) And I make it no secret that I have a reason for my disdain for this man & his tactics ... and that is because he "stole" my method & its name (Vertical Casting) and posted it without so much as a mention of the originator or acknowledgement that it was someone else's intellectual property.
... cp