Genetic Quality Monitoring And Genetic Identification Of Hatchery-reared Individuals For Stock Enhancement

Due to the overfishing and increasingly serious environmental pollution,fishery resources was generally recessing in China.In the late 1950 s,China began to implement the fishery stock enhancement.Years of practice has proved that stock enhancement was an effective pattern to restore the fishery resources.On the other hand,the rapid development of China’s stock enhancement has base on the extensive scale,and lacks scientific guidance.The two conspicuous aspect were the shortage of monitoring methods for fingerling genetic quality and difficulties of Genetic identification of releasing individuals.There were two cases of Acanthopagrus schlegelii and Lutjanus erythopterus in this research.The microsatellite markers were developed and selected to compose the "molecular marker group".The fingerling stock and the natural stock were contrasted from four aspects(genetic divergence,genetic diversity level,inbreeding degree,genetic information retention ability),and the genetic quality of the fingerlings were evaluated.The releasing individual genetic identification method were established by parentage analysis,and the method was applied in stock enhancement of A.schlegelii.This research will be introduced as follows:(1)The development of "molecular marker group"A total of 9 125 microsatellite sequences more than 250 bp of A.schlegelii were obtained using the "high-throughput sequencing method".180 microsatellite primers were designed and manufactured.The primers were screened and tested using a wild population(N = 48).Finally 46 microsatellite markers were successfully developed.Thirteen markers were selected to make up a "molecular marker group".The average number of alleles per locus was 9.31.The average value of observed and expected heterozygosity were 0.732 and 0.747,respectively.All the sites were in Hardy-Weinberg equilibrium.There was no linkage disequilibrium among the loci.According to the previous development of microsatellite markers of L.erythopterus,11 markers were selected to compose of "molecular marker group".The average number of alleles per locus was 8.The average value of observed and expected heterozygosity were 0.746 and 0.789,respectively.Two loci showed significant deviations from HardyWeinberg equilibrium.There was no linkage disequilibrium among the loci.The results showed that two marker groups were high polymorphism.(2)Establishment of genetic quality monitoring method for fingerlingA fingerling stock and a natural stock of A.schlegelii and L.erythopterus were contrasted from four aspects(genetic divergence,genetic diversity level,inbreeding degree,genetic information retention ability),and the genetic quality of the fingerlings were evaluated.The results showed that a faint genetic divergence existed between the two stocks(FST of A.schlegelii = 0.0247,FST of L.erythopterus = 0.016),genetic diversity level and effective population size of the two fingerling stocks were lower than that of the natural stock,inbreeding coefficient mean and FIS of the two fingerling stocks were higher than that of the two natural stocks.The above comparisons proved that the genetic constitution of the two fingerling stocks were inferior to the two natural stocks,and the genetic quality of the two fingerling stocks was not meet the requirements of releasing.Effective population size was the major genetic quality defect,due to the maximum deviation rate of this indicator(the deviation rate of A.schlegelii =-77.85%,the deviation rate of L.erythopterus =-35.34%).(3)Genetic identification of releasing individualsThe DNA of 102 A.schlegelii broodstock population were genotyped using the genetic marker group.The genotyping data was inputted to the parentage analysis software.A parentage assignment simulation was conducted to evaluate the assignment ability of the marker group and determine the critical LOD value which was 5.46.The A.schlegelii broodstock population was isolated to oviposit,the fertilized eggs were hatched.The juveniles were cultured to standard longht for releasing.In the Daya Bay,25 million A.schlegelii were released.Six months later,240 A.schlegelii were caputered within three months.Seven releasing individuals were identified in 240 recaptured individuals by parentage analysis,and the resource contribution rate was 2.92 %.The supplemental effect of this stock enhancement on natural resources is limited.This research can provide a scientific guidance for the establishment of the genetic quality monitoring methods for the fingerling,and provide a technical basis for the accurate assessment of proliferation effect of stock enhancement programs.