. . that the Swedes, Lithuanians and Latvians would be fishing in the Baltic Sea".

Yes, also the North Sea, but what they do with Sprats can be quite different. Latvia is the most dependent on the Sprat fishery. They heavily smoke most of their catch, put them up in 4 inch diameter cans with oil, and sell them as "Riga Sprats". These would be useless for something like Jansson's Temptation.

The Lithuanians don't seem to do much smoking, but pickle most of their Herring and Sprats, packing them in brine or oil - oil predominating.

The Swedes do mostly Herring, put up in little jars a dozen different ways, but I've seen those only at IKEA.

The three non-Asian multi-ethnic markets I shop at have many fish products from Lithuania and Latvia, along with some from Estonia and Russia, but nothing from the Scandinavian countries - they probably have a domestic shortfall.

Norway used to be big in Sardines and the like, but the fishing and canning facilities have mostly been replaced with refineries for North Sea oil.

Russia's big product is dried fresh water fish, Caspian Roach and similar, under the name "Vobla". I have published instructions on how to eat a Vobla - Caspian Roach - patience and much beer are the basic requirements.