Morphological Variation And Genetic Diversity Of Five Populations Of Small Yellow Croaker(Larimichthys Polyactis)

Small yellow croaker (Larimichthys polyactis) is an economically important marine fish in China. Though the resource of small yellow croaker increased gradually since the rule of Summer Closed Fishing has been implemented from1980s, the population of small yellow croaker is still weak due to overfishing and environmental pollution. In this paper, we collected five populations of small yellow croaker in China Sea, i.e. Shacheng(SC) in Fujian province, Taizhou(TZ) in Zhejiang province, Lianyungang(LYG) in Jiangsu province, Yantai(YT) in Shandong province, and Donggang(DG) in Liaoning province, and analysed the population morphological variation and genetic diversity by using morphological truss data and mitochondrial DNA cytochrome b and control region complete sequences. This study may be useful for effective management and sustainable ustilization of small yellow croaker resource.The results are as follows:1. A total of186individuals of five populations were measured. Each individual was measured the bodylength and18truss network data. After deleting the extreme values by using statistical software, we got the truss system data of185valuable individuals at last for this research. We have compared these morphological characters by using the multivariate statistical analysis, ie.cluster ananlysis and discriminant analysis. The results suggested that SC, YT, DG, and TZ gathered together first, and finally formed a robust cluster with LYG. Discriminant analysis showed that the total identification accuracy was98.9%.2. A total of114individuals of five populations were measured, and the complete mitochondrial Cytochrome b(Cytb) gene of1141bp was collected. There were no idels in these sequences.94haplotyes were found, and the ancestor was hap39. The indice of haplotypes diversity (Hd=0.992) and nucleotide diversity (π=0.45%) showed that all these five populations have high haplotypes diversity and a bit lower nucleotide diversity. The genetic distance between and among these five populations were0.375%～0.574%and 0.386%～0.540%by using Kimura-2-parameter model, this result indicated that the difference between and among these five populations were not significant; The results of Neighbor-joining tree, median-joining network showed that the individual distribution of these five populations were discrete; the Fst among these populations were0.00019～0.02474, which suggested that the genetic divergence were hardly exist and result of analysis of molecular variance (AMOVA) indicated that the genetic divergence were insignificant, the variation were most within but not among population. Tajima’D and Fu’s Fs neutral tests suggested that all of the populations may suffer from population expansion or bottleneck.3. A total of115individuals of five populations were measured, and the complete mitochondrial control region (D-loop) of796-798bp were collected. There were two idels in DG and one idels in TZ.107haplotyes were found, and the ancestor was H33. The indice of haplotypes diversity (Hd=0.998) and nucleotide diversity (π=1.075%) showed that all these five populations have high haplotypes diversity and slightly lower nucleotide diversity.The genetic distance between and among these five populations were0.927%～1.359%and0.993%～1.227%by using Kimura-2-parameter model,this results indicated that the difference between and among these five populations were not significant;The results of Neighbor-joining tree, median-joining network showed that the individual distribution of these five populations were discrete; the Fst among these populations were0.001～0.017, which suggested that the genetic divergence were hardly exist and result of analysis of molecular variance (AMOVA) indicated that the genetic divergence were insignificant, the variation were most within but not among population. Neutral tests suggested that the populations may suffer from population expansion or bottleneck.