Developing novel means for unravelling population structure, provenance and migration patterns of European whitefish Coregonus lavaretus s.l. in the Baltic Sea

•Assignment framework for determining population structure of European whitefish.•Finnish origin stocked individuals accounted for 50% of the adults sampled in Estonia.•Wild anadromous and sea-spawning individuals accounted for 35 and 14% of the adults sampled in Estonia.•Highly distinct otolith natal fingerprints in reared juveniles.•Up to 15 distinct sources of adults stocked as fingerlings were identified.