[ThomasWinwood]

For the benefit of future readers who don't get it, if nothing else: the "salmon problem" (in German Lachsargument) is an old argument that the origin of the Indo-European language family should be in the Baltic region, because the word for "salmon" is found in both the Germanic and Balto-Slavic branches. Later research in the Caucasus found that the reflexes of the word referred to trout, which is found in rivers on the Eurasian steppe. (They're both species in the genus Salmo, so it makes sense that semantic drift would occur in populations moving to a new area.)