Unravelling the Past: Genetic Structure and Species Diversity of Ancient Sturgeon in Lake Ladoga

ABSTRACT Aim Taxonomic identification, population demographics and genetic structure reconstruction of the historical Lake Ladoga sturgeon population, followed by assessment of admixture and gene flow of Atlantic and European sturgeons within the Baltic and broader European context. Location Archaeological site at Staraya Ladoga (Zemlyanoe Gorodishche), encompassing samples from Lake Ladoga and the Volkhov River in north‐western Russia. Taxon Atlantic ( Acipenser oxyrinchus ) and European ( A. sturio ) sturgeons. Methods A total of 7130 sturgeon bones dated to the 9th–10th centuries CE were morphologically examined to determine their species identity. Age ( n = 51) and catch season ( n = 33) were reconstructed. Genetic analyses of remains from Ladoga ( n = 45) and other European localities ( n = 48) were conducted using three mitochondrial DNA (mtDNA) fragments, seven microsatellite loci (STRs), and one SNP‐informative microsatellite locus ( Aox 23) to assess species composition, ancestry, admixture, and gene flow with other sturgeon populations, including published historical Baltic ( n = 62) and contemporary samples from France and Canada ( n = 184). Results Age analysis showed a bias toward large, older individuals that were likely caught during spring‐early summer spawning migrations. The Atlantic sturgeon was the dominant species, based on both morphology (83%) and genetic analysis. None of the individuals were identified as pure European sturgeon or first‐generation hybrids. Only 5% of STR alleles showed European sturgeon ancestry, and 11% of individuals carried its diagnostic mtDNA haplotype. Admixed samples were found in the Ladoga region, Baltic Sea and North Sea. Main Conclusions Our findings revealed the historical dominance of the Atlantic sturgeon in Lake Ladoga and across Northern Europe including the North Sea. It also sheds new light on the colonisation process, suggesting a rapid Atlantic sturgeon expansion into north‐eastern Europe with minimal hybridization with European sturgeon during this phase. This study highlights past connectivity among sturgeon stocks in Europe and underscores the importance of preserving migration routes and habitats to maintain gene flow, which is critical for effective sturgeon restoration.