Scale Loss: If you see a lot of loose scales floating amid the live bait, it's a sure sign your bait might not be healthy and will be short‑lived.
Dry Skin: Pick up one of the baits and feel it. Healthy baitfish sport a nice coat of slime, but if the skin feels dry and raspy, the bait esta no bueno.
Red Noses: Chafed, blood-red noses is an indication that the bait has been beat up, either in a net through improper handling or due to improper water flow in the livewell. Red-nosed bait might last a while, but it's not as desirable as bait with natural-looking snouts.
Failure to Mill: Healthy bait should settle down and exhibit a relaxed milling behavior soon after you put them in the livewell. If they dart about or swim with their noses against the sides of the tank, it's usually a sign of too much water flow. Try turning it down a bit to see if they will begin milling. If not, fish quickly, because your bait is not long for this world.