Abstract
The northern pike (Esox lucius L.) is a commercially important fish that forms freshwater and brackish populations. While the first ecotype is still quite abundant, the second has suffered rapid declines in recent years. Populations inhabiting the Baltic coastal waters of Poland have been supported by stocking programs since the late 1990s. This study describes a multiplex microsatellite (msDNA) assay consisting of 12 loci divided conveniently into two amplification sets (Elu78, Elu87, B451, Elu37, B457, B16, B25, and Elu19, Elu76, B422, Elu2, Elu7). The assay was optimized for genetic analyses of freshwater and brackish populations. These multiplexes were successfully executed to obtain the genetic profiles of 668 individuals from 16 populations (Poland and Germany). The average number of alleles was equal to 10.4, whereas the observed heterozygosity per locus ranged from 0.18 to 0.89, with the average value of 0.64. The probability of the identity of the marker sets indicated the high power of identification of unique genotypes. Therefore, this molecular tool can be used to describe the genetic variability of populations, select the proper source of breeding material, and monitor the progress of stocking efforts in genetic conservation projects of this species.