Hatchery release programme modified the genetic diversity and population structure of wild Chinese sucker (Myxocyprinus asiaticus) in the upper Yangtze River

Abstract

Abstract The Chinese sucker (Myxocyprinus asiaticus) is an endangered and threatened fish species in China. To augment wild populations, millions of captive‐bred Chinese sucker have been released into the upper Yangtze River in recent years, with little evaluation of the genetic impact. The genetic diversity of 112 wild M. asiaticus from different reaches of the Yangtze River was examined, and the population structure among them and three artificially bred populations was determined using 12 microsatellite markers. Genetic data from the wild M. asiaticus populations before the hatchery release programme were synthesized and compared to detect fine‐scale variation in genetic structure together with spatiotemporal changes in the wild population. The results showed that the genetic diversity of wild M. asiaticus was relatively high (observed heterozygosity = 0.604–0.609, polymorphic information content = 0.442–0.496), even though a moderate decrease in total diversity was detected when compared with previous studies. M. asiaticus from the Wanzhou reaches, which showed low genetic variation before the stocking programmes, displayed the highest level of genetic diversity (observed heterozygosity = 0.609, polymorphic information content = 0.496) in this study. Insignificant differences in genetic structure among wild populations, with low genetic differentiation (Fst = 0.035–0.083), as well as close genetic relationships between wild and hatchery populations were observed. Current genetic diversity and population structure of wild M. asiaticus were strikingly different from those before the hatchery release programme, which indicated that stocking activities have altered the genetic character of the populations in the upper Yangtze River. The conservation of M. asiaticus requires legal protection for the fish and its habitat. Genetic monitoring of the wild populations and accurate evaluation of genetic divergence is imperative. In addition, the results of this study should be used to provide scientific guidance for an effective hatchery release programme for M. asiaticus.