Background. Recent genetic analyses of fish remains, obtained from archaeological sites, revealed that more than 2000 years ago the Baltic Sea was inhabited by sturgeons closely related to the Atlantic sturgeon, Acipenser oxyrinchus Mitchill, 1815. As some wildlife populations of the Atlantic sturgeon are still present in Canadian rivers, we decided to use those fish to restore the extinct Baltic population. Materials and methods. Fin clips of 50 A. oxyrinchus were collected from fry representing two hatcheries. At the hatchery  No. 1 sturgeons were reared from fertilized eggs received from the Acadian Sturgeon and Caviar Inc., Canada. At the hatchery No. 2, larvae provided by the Regional Research Institute for Agriculture and Fisheries (Germany) were reared for several months until they were released into rivers. The molecular data of 22 and 28 specimens from hatcheries  No. 1 and No. 2, respectively, were compared with homological D-loop sequences and some microsatellite loci derived from two museum specimens of sturgeons from the Tadas Ivanauskas Museum of Zoology, Kaunas, Lithuania. Signs of possible introgressive hybridization between Acipenser sturio Linnaeus, 1758 and A. oxyrinchus in two museum specimens were checked by comparison of alleles at loci AoxD161, AoxD188, AoxD297, AoxD242, and AoxC30. A possible affinity of between sturgeons released in Lithuanian rivers in 2015 and samples representing hatcheries  No. 1 and No. 2 was estimated based on multi-locus genotyping data using the Structure software, version 2.3.4. Results. The same D-loop haplotype H1 characteristic for the museum specimens (MK637525 and MK637526) was also found as the only haplotype distributed among sturgeons reared in hatcheries and used for population re-establishment. A possible hybridisation between A. sturio and A. oxyrinchus was not confirmed for two museum specimens studied. The first results of genetic application undertaken in Lithuania also revealed the possibility to discriminate the individuals obtained from different hatcheries based on the set of 13 microsatellite loci Aox45, AoxD54, AoxD161, AoxD297, AoxD188, AoxD234, AoxD242, AoxC45, AoxC30, AoxD241, AoxD64, AoxD186, and Ls-68. The analysis of A. oxyrinchus specimens representing F1 generation of parental individuals reared in two separate hatcheries in Canada and Germany revealed significant differences in the allele composition and high probabilities for individuals released into the natural environment to be assigned to the hatchery of their origin. Conclusion. The results of the molecular analysis will be useful for identification of age, pedigree, and for initiating genetic monitoring of the restored population of the Atlantic sturgeon in the Baltic Sea.

Acipenser oxyrinchus, genetic diversity, D-loop, DNA microsatellites