Genetic survey of crucian carp Carassius carassius populations in Hungary for a conservation project to establish live gene bank

The crucian carp (Carassius carassius Linnaeus, 1758) is a declining native European cyprinid, inhabiting small water bodies, primariliy threatened by climate change, anthropogenic impacts and invasive relative the Prussian carp. Despite conservation efforts across Europe, data on Carphatian Basin populations remain scarce. This study analyzed nine natural populations (257 individuals) in Hungary using thirteen microsatellite markers and mitochondrial DNA COI sequencing (187 individuals). Sequencing of mitochondrial DNA revealed a presumably introduced Baltic stock in addition to the Danube lineage and the presence of Prussian carp hybrids in part of the populations. Microsatellite markers also confirmed the latter, but there were populations in the southern region free of hybrids. Genetic diversity was found to be moderate (Ho: 0.49-0.61; Ar: 6.01-7.98). Depending on the genetic structure analysis method, two or three main units with low to moderate differentiation were detected (FST: 0.054-0.192). Based on gene flow, the Danube-Drava region showed a separation from the northern areas and the populations on the eastern bank of the Danube. Eight of the nine populations examined, especially the south Danube populations, could provide a good basis for the establishment of a genetically controlled gene bank of remaining crucian carp stocks, without hybrids.