Idunno fersure, but with [link|http://www.thefreedictionary.com/sprats|an English dictionary calling sprats] Clupea sprattus and [link|http://sv.wikipedia.org/wiki/Ansjovis|the Swedopedia talking about our fakechovies] as Sprattus sprattus, "of the family Clupeidae", I'd guess they're different variants of Latin name for the same critter; wouldn't be the first time that's happened.
Checking the [link|http://en.wikipedia.org/wiki/Sprats|English-language Wikipedia on Sprats] and [link|http://en.wikipedia.org/wiki/Herring|on Herring], it doesn't seem to recognise any "Clupea sprattus"; seems more like it follows the same Latin-name system as the Swedish-language Wikipedia.
So yes, it seems your "sprats" and our "ansjovis" are at least mostly overlapping groups of actual species. (N.B: Our "ansjovis" are invariably smaller than the ones sold as "sardines" [or, nowadays, "brislings"]; they are, to connect back to the start of this thread, usually about as long as a Key lime [and thin for their length; the canned fish fillet is just a sliver of flesh, just like the real anchovy]. :-)