Shifting genetic structure of Polish sea trout populations: a contemporary perspective.

The genetic structure and variability of sea trout populations in the southern Baltic Sea were shaped during the last glaciation, in parallel with the evolution of the Baltic Sea. However, human activities-particularly hydrotechnical development and the introduction of non-local genetic lines-have altered and partially reduced the original genetic diversity. In the present study, the authors describe the historical changes that have occurred and present the current level of genetic variability within Polish sea trout populations. A total of 575 sea trout from nine river populations and three hatchery broodstocks were genotyped at 13 microsatellite loci. The global F_ST obtained via AMOVA was moderate, at 0.041. The highest pairwise F_ST values were observed between the Rutki and Aquamar broodstocks and all other populations. The lowest and statistically non-significant pairwise differences were detected between the Rega and Ina river populations, as well as between the Słupia and Łupawa. Genetic structure analysis revealed geographic differentiation, identifying either four or seven distinct clusters. Additionally, neighbour-joining clustering showed that the examined populations and stocks were divided into two main subgroups: one consisting of samples related to the Vistula origin, and the other comprising clearly separated Pomeranian populations. This paper discusses the emergence of new genetic variability driven by microevolutionary processes and presents a revised approach for sea trout population management.