| Fenneropenaeus chinensis is one of the important economic species in Bohai Sea.Due to the influence of many factors such as overfishing,habitat water pollution,frequent diseases and long-term large-scale stock enhancement,the indicated resource fluctuates greatly,From a peak of 39,000 tons（in 1979）to less than 500 tons（in 1998）.After 38years of stock enhancement and releasing,its resources once recovered to about 10,000tons（in 2016）.It can be seen that enhancement and releasing is an important measure to protect and restore F.chinensis resources.In the process of population reestablishment after the crisis of resource decline,what has happened to population biology and population genetics of F.chinensis?And what effect did the changes produce to the other Fisheries biology in Bohai Sea?To answer these two questions,the article takes F.chinensis in Bohai Sea as the research object,summarized the evolution of biological characteristics and genetic diversity of F.chinensis,illuminate its influence on fishery resources.To provide reference for effective protection and sustainable utilization of F.chinensis and fishery resources in Bohai Sea.Firstly,we summarized the evolution of biological characteristics of F.chinensis and illuminate its influence on fishery resources.The research show that the average body length of female and male increased from 201mm and 163.5mm in 1981 to 240mm and184mm in 2012,respectively,and the growth factor decreased from 0.018 and 0.0168 to0.0102 and 0.0015,respectively.There was a trend of increasing body length and prolongation of growth cycle.The feeding characteristics of F.chinensis did not change significantly.Juvenile mainly fed on phytoplankton,while adult mainly fed on small benthic animals,as well as zooplankton and small swimming fish.In addition,F.chinensis was the dominant species of fishery resources in Bohai Sea in 1959,accounting for 14.6%of the biological resources.But according to a survey report in 2015,F.chinensis accounted for less than 3%in the economically important invertebrates in the Bohai Sea,while Oratosquilla oratoria accounted for 61%.It can be seen that the dominant position in crustaceans of F.chinensis has been completely replaced by Oratosquilla oratoria in Bohai Sea.The resourses of harmful organisms of F.chinensis such as Lateolabrax maculatus,Larimichthys polyactis and Hexagrammos otakii have been sharply reduced since the 1980s,the spring CPUE decreased from more than 25kg/h in 1982 to less than5kg/h in 2013.The resource density of feed organisms including phytoplankton,zooplankton and benthic organisms decreased in Bohai Sea.Secondly,the mitochondrial Cyt b gene and mitochondrial D-loop region sequences were selected as molecular markers to analyze the genetic structure of the population of F.chinensis.A total of 344 individuals were collected from Laizhou Bay,Bohai Bay,Liaodong Bay and Changdao.The haplotype diversity based on Cyt b was 0.8270 and nucleotide diversity was 0.0018,while the haplotype diversity based on D-loop was0.9380 and nucleotide diversity was 0.0085,showing the characteristics of high haplotype diversity and low nucleotide diversity.Neighbor-joining tree was constructed and found that the four populations of F.chinensis clustered into one branch,and there was no obvious genetic structure variance.Molecular analysis of variance（AMOVA）showed that the genetic variation was mainly from within the population.The neutral test values of Tajima’s D and Fu’s Fs were both negative and statistically significant（P<0.05）.Combined with the nucleotide mismatch distribution proved that F.chinensis had experienced population expansion.Compared with previous studies based on D-loop sequence,the nucleotide diversity of F.chinensis decreased from 0.0198 in 1999 to0.0085,indicating a decrease in genetic diversity.Finally,to master the evolution trend of F.chinensis in Yellow Sea and Bohai Sea population,the effects of releasing population on natural population genetic resources were explored.In this study,whole genome resequencing（WGS）technology was used to analyze population genetics of 115 samples of F.chinensis,including two releasing populations（from Bohai Bay and Laizhou Bay,respectively）and three natural populations（from Liaodong Bay,Bohai Bay and Laizhou Bay,respectively）collected in2021 and another natural population collected from the Yellow Sea in 2010.A total of492,847 high-quality SNPs were screened.NJ tree and genetic structure analysis showed that there was slight differences in genetic structure between Liaodong Bay natural population,Yellow Sea population and the other four populations.The results of principal component analysis（PCA）showed that although the natural populations in Liaodong Bay gathered,but there was no obvious clustering phenomenon.Some individuals of the populations in the Yellow Sea dispersed from the clusters,showing a trend of variation and separation,and the other samples clustered together.The results the historical effective population size of F.chinensis populations showed that there had been a maximum effective population size distribution in the history,among them,the effective population numbers of the three natural populations collected from the Bohai Sea were significantly lower than those of the Yellow Sea populations in 2010.In addition,FSTselective elimination analysis was between two populations.The results showed that the three natural populations collected from Bohai Sea in 2021 had obvious genetic differentiation compared with the 2010 Yellow Sea wintering population. |
