Studies On Fish Resources And Genetic Diversity As Well As Genetic Variation Of Representative Species In The Jiaomuzu River

The present status of fish resources in Jiaomuzu River was studied by two consecutive years' investigation in 2016 and 2017,and the sequence of mitochondrial DNA control region in Hucho bleereri and Schizopygopsis malacanthus chengi was analyzed in order to understand the genetic background of the population and provide information for the effective protection of population resources.The main conclusions are as follows:11 species of fish were collected from the Jiaomuzu River,belonged to three orders,four families and six genera.Among these fish,Cypriniformes which contained 8 species was the most dominant order,accounting for 72.73% of the total species in Jiaomuzu River,followed by 2 species of Siluriformes and 1 species of Salmoniformes.The dominant species were S.malacanthus chengi,Schizothorax(Schizothorax)prenanti and Triplophysa markehencnsis,which accounted for 29.54%,27.94% and 13.77% of the total catch respectively.Euchiloglanis davidi,E.kishinouyei,Triplophysa stoliczkae,T.orientalis and Paracobitis variegatus were the common species in the river section,and H.bleereri was a rare species.There was no obvious difference in the distribution of fish composition along the river,but there were obvious differences in fish resources and individual size of catches in different reaches.The river section from Kehe to Shejiang,which was less disturbed by human activities,was relatively abundant in fish resources and had larger individual catches.It was also the main distribution area of H.bleereri.The habitat of fish such as H.bleereri shrinked gradually because of human activities,and the rate of habitat lose was more than 90%.The Jiaomuzu River was the last distribution area of H.bleereri which is critically endangered in the Dadu River Basin.The fish in the Jiaomuzu River can be divided into three Fauna Complex,namely,the Northern Mountain Fauna Complex,the Central Asian Mountain Fauna Complex and the Southern Mountain Fauna Complex.Among them,the Central Asian Mountain Complex is the most complex.The fish of the Jiaomuzu River mostly were adapt to the torrent,and the demand for flow pattern was relatively simple.They can be divided into flow-water cavern gap group,flow-water adsorption group,flow-water bottom group and flow-water upper group.The spawning types of fish can be divided into three types: submerged egg,sticky egg and floating egg.Among them,there were relatively more fish spawning sticky egg.The short-distance reproductive migration habits of H.bleereri,S.(Schizothorax)prenanti,S.(Racoma)davidi and S.malacanthus chengi were observed.The analysis of the population structure of the main economic fish in the Jiaomuzu River showed that the age composition of the S.malacanthus chengi population was 2-8 years old,and the dominant age group was 4~5 years old.The age composition of the S.(Schizothorax)prenanti population was 2~10 years,and 3~4 age was the dominant age group.The age composition of the S.(Racoma)davidi population was 2~6 years,and 3~4 age was the dominant age group.The relationship between body length and body weight was power function for some fish,such as S.malacanthus chengi,S.(Schizothorax)prenanti,S.(Racoma)davidi and E.davidi.The genetic diversity was analyzed in the endemic species.A total of 19 polymorphic loci(S)and 36 haplotypes(H)were detected in 72 individuals of S.malacanthus chengi.The haplotype diversity(Hd)was 0.969,nucleotide diversity(Pi)was 0.01393 and average nucleotide variations(K)was 3.42684.The haplotype diversity and nucleotide diversity were both at relatively high levels,implying the wild population of Schizopygopsis malacanthus chengi was still in a state of high genetic diversity.The phylogenetic tree analysis showed that 72 individuals were divided into two branches.It was speculated that the S.malacanthus chengi population in the Jiamuzu River Basin might originate from two ancestors with different genetic backgrounds.A total of 1 polymorphic loci(S)and 2 haplotypes(H)were detected in 15 individuals of H.bleereri.The haplotype diversity(Hd)was 0.133,nucleotide diversity(Pi)was 0.00023 and average nucleotide variations(K)was 0.13333.Its haplotype diversity and nucleotide diversity were at an extremely low level.The results showed that the H.bleereri was in an urgent position to be protected in terms of population size and genetic diversity.It was suggested that it should be considered as a priority species to be protected in the Jiaomuzu River Basin.In this study,high-throughput RAD(restriction Association site DNA)sequencing was further carried out for H.bleereri,resulting in Clean data between 2.08 G and 2.61 G.Sequencing quality was Q20 ? 97.25%,Q30 ? 92.98%,GC content was 41.97%,and the sequence depth was above 10×.The above results indicated that the results of RAD sequencing were acceptable and reliable.In addition,690559 SNP loci were detected in the three individuals,and the proportion of heterozygous loci was 50.77%.In summary,the RAD genome sequencing was carried out in three individuals of H.bleereri in the Jiaomuzu River Basin,and high-quality sequencing data were obtained.A large number of SNP markers were obtained,which laid a theoretical foundation for further study on population genetic structure and evolution,construction of genetic map and QTL mapping of important traits.