What's the difference between sprats and sardines?

[meinNYC]

We just had a can of smoked sprats from Russia and were wondering why they tasted so differently
from the sardines in the supermarket. Are sprats just sardines that have been smoked or is a different fish or is a sprat a baby sardine? Please explain.... thanks

[pj26]

Google is your friend! Good explanation here http://en.wikipedia.org/wiki/Sprattus

So, they are actually two different genus but sometimes sprats are passed off as sardines