Population Ecology And Genetic Diversity Of Parabramis Pekinensis In The Lower Reaches Of Yangtze River

Parabramis pekinensis belongs to the genus of Parabramis Bleeker,the subfamily of Culterinae,the family of Cyprinidae and the order of Cypriniformes,widely distributed in the rivers and lakes across the country,is one of the important economic fish,also is one of the dominant species of Yangtze river multiple.Few scholars on the study of Parabramis pekinensis now,mainly concentrated in the genetic diversity,pathological disease,ecology,etc.,for the Yangtze river downstream group reported for the first population ecology research,nowadays people on the destruction of the ecological environment worsening,fish habitat in jeopardy,fishery resources has drastically reduced,In this experiment,the population of Parabramis pekinensis in the lower reaches of the Yangtze river was taken as the research object,and the population ecology and genetic diversity were studied in order to provide scientific basis for the understanding of the status quo and resource protection of roach in the lower reaches of the Yangtze river.1.Parabramis pekinensis scale was used as age material to identify age ring characteristic,and otolith weight was used to verify the accuracy of identification.The age structure of female fish is 1-4 years old,and the fish of 2 years old accounts for65.3%of the female fish,followed by the fish of 3 years old,and the fish of 4 years old accounts for 4.10%of the female fish.For male fish,the age structure is 1-6 years old,and focus on Parabramis pekinensis of 2 years old,accounting for 60.90%of the total male population,followed by 3 years old,and the smallest is 5 years old and 6years old,accounting for 1.18%of the total male population.The average body length is also increasing with the increase of age.2.The body length range of the Parabramis pekinensis in the lower reaches of the Yangtze river is 27.16-330.00mm,with an average body length of154.01±44.63mm,and the dominant body length range of 100.00-199.99mm,accounting for 75.78%of the total individuals.The range of body weight was0.24-723.00g,the average weight was 79.42±75.03g,and the range of dominant weight was 0.24-99.99g,accounting for 73.20%of the total individual.The relation between body length and body weight was fitted by power exponential function:y=1.0×10^-5x^3.0674?R²=0.973?;The fitting relation y?female?=49.429x+29.424?R²=0.7968?,y?male?=39.252x+60.501?R²=0.6486?,von Bertalanffy growth equation L_t=325.26[1-e^{-0.21?t+0.51?}],the inflection point ages of females and males were 3.57years,4.83 years,224.84 mm,163.74 g,219.28 mm and 151.63 g,respectively.3.Parabramis pekinensis population sex radio was 1:0.91.Females are slightly more than males,and the neutral ratio varies in different age groups and body length.The female was the smallest sexually mature individual,with body length of113.15mm,weight of 26.14g and age of 1 year.The smallest sexually mature male was137.59mm in length,37.26g in weight and 1 year in age.The egg diameter rang0.559-1.15mm,with an average of 0.85 0.16mm,absolute fecundity?F?of1630.34-154247.31,an average of 35792.16 39380.64,relative weight fecundity?FW?of 10.99-383.70/g,and an average of 120.06 89.68/g.4.The sequencing results of three geographic groups in the lower reaches of the Yangtze river were compared and processed to obtain sequences with a length of855bp,and the data homology was more than 99%compared with the NCBI database.50 haplotypes were found,and the number of haplotypes in different river sections ranged from 19 to 23.Polymorphic bit number 22-28,nucleotide diversity range0.00565-0.00586,overall nucleotide diversity?Pi?0.00556±0.00025,belonging to high genetic diversity,low nucleotide diversity;The genetic distance within the population was 0.0055-0.0057,the genetic distance between geographic groups ranged from 0.0055-0.0057,and the genetic differentiation coefficient ranged from0.00198-0.01379.The gene flow was at a high level,indicating frequent gene exchanges between groups and low degree of genetic differentiation.5.Zhenjiang section Parabramis pekinensis open body length and age were 234.81 mm,1.49 a,shows that Parabramis pekinensis larvae and group as the main target of the fishing,while a large number of young fish individual loss to cause a decline in fish resources and breeding among individuals,according to population complement model can protect added about 62.35%of the population,further extended to the end of August,if the closure can protect 88.22%supplement group,this to promote Zhenjiang section Parabramis pekinensis and other economic fish resources conservation and sustainable use has positive significance.