Temporal genetic variation of the Chinese longsnout catfish (Leiocassis longirostris) in the upper Yangtze River with resource decline

We investigated the temporal dynamics of population genetics of the Chinese longsnout catfish (Leiocassis longirostris) given wild population decline due to anthropogenic disturbances such as overfishing in the upper Yangtze River. We compared genetic variation and structure between five age classes (1, 2, 3, 4 and 5 years old) using the mitochondrial DNA (mtDNA) control region and 12 microsatellite markers. The five age classes had high haplotype diversity (h = 0.8743) and nucleotide diversity (π = 0.0082) inferred from the control region, and observed heterozygosity (HO = 0.7342) and polymorphism information content (PIC = 0.6764) inferred from microsatellites. Low genetic distances based on the control region and the median-joining network representing a widespread distribution of haplotypes identified close genetic relationships between age classes. The results of AMOVA and pairwise fixation index (FST) using microsatellites demonstrated the significant genetic differentiation between age classes and FST was mostly low but significantly different between age classes (P < 0.05). Overall, L. longirostris in the upper Yangtze River has maintained considerable genetic diversity, but temporal genetic instability was detected between age classes. With the implementation of a ten-year fishing ban in the Yangtze River from 2021, it is expected that genetic differentiation between age classes will gradually decrease with the recovery of fish resources, and future genetic monitoring of L. longirostris populations is recommended.