Genetic Diversity Analysis And Migration Research By Pedigree Tracing Of Chinese Shrimp (Fenneropenaeus Chinensis) During Stock Enhancement

Chinese shrimp(Fenneropenaeus chinensis) is an important migratory marine species of significant commercial value to the Chinese aquaculture and fishing industries, which are concentrated mainly in the Bohai and Yellow Seas. Chinese shrimp resource is very abundant in the history of China, however, worsening pollution, overfishing, and increasing demand for spawning shrimp accelerated the collapse of the wild shrimp fishery. Stock enhancement through artificial release has become an important way to restore Chinese shrimp in the wild and the natural population was largely reliant on released shrimp to maintain its size. After several decades continuous practice, hatchery release enhancement was proven to be an alternative strategy for natural population recovery of Chinese shrimp, by the same time, from which, the fishing industry also benefited gradually. During this periods, different kinds of methods were developed to assess the recapture rate, a very important index in assessing whether a release activity has been successful. in which, marker-recapture method, especially physical markers, including eye tag, visible implant elastomer(VIE), code wire tags(CWT) and radio frequency identification(RFID), was the most commonly used, due to several deficiencies of these mentioned physical marker in common, such as labor-intensive tagging process, damageable to tagging individuals, impractical for large-scale application, which all made against to calculate a precise recapture rate for release effect assessment. The simple sequence repeat(SSR) was distinguished from previous physical tagging methods, which was based on individual identification and pedigree tracing using SSR marker and was successfully applied in release effect assessment.In this study, we evaluated the different level of genetic diversity of the two populations and suggest the number of shrimp spawners needed for resource enhancement and release of Chinese shrimp. Then, we recognized the “internal standard” individuals in the recapture species to study the distribution of released Chinese shrimp, Fenneropenaeus chinensis, provides a scientific basis for recapture ratio assessment of Chinese shrimp hatchery releases and discussing the enhance and release management strategy.For spawner and recaptured populations of Chinese shrimp(Fenneropenaeus chinensis) during stock enhancement in Bohai Bay in 2013, Fis values were positive at seven loci and the inbreeding coefficients(F) of the two populations estimated by trioML were 13.234% and 11.603%, suggesting that there was a relatively high degree of inbreeding. A certain level of inbreeding depression had occurred in the Chinese shrimp population. Effective population sizes(3060.2 and 3842.8) were higher than the minimum number suggested for retaining the evolutionary potential to adapt to new environmental conditions. For enhancement activity in Bohai Bay in 2014, the ideal number of captured shrimp spawners should have ranged from 7686 to 19214 to maintain genetic diversity and effective population size. For spawner and recaptured populations of Chinese shrimp(Fenneropenaeus chinensis) during stock enhancement in Laizhou Bay in 2015, Fis values were positive at six loci and the inbreeding coefficients(F) of the two populations estimated by trioML were 11.3% and 10.3%, suggesting that there was a relatively high degree of inbreeding. A certain level of inbreeding depression had occurred in the Chinese shrimp population.. Effective population sizes(3572.1 and 2752.7) were higher than the minimum number suggested for retaining the evolutionary potential to adapt to new environmental conditions. For enhancement activity in Laizhou Bay in 2016, the ideal number of captured shrimp spawners should have ranged from 5505 to 13764 to maintain genetic diversity and effective population size.842 from Bohai Bay in 2013 and 288 from Laizhou Bay and Bohai Bay in 2015 were recaptured in the fisheries resource enhancement and releasing of Fenneropenaeus chinensis. For Bohai Bay populations, these 8 SSR loci crossing the whole 1726 samples were involved in single parent parentage identification analysis between 884 spawners and 842 recapture samples by using Cervus 3.0 software, the results were: total 448 offspring from 842 recapture samples were traced to their 337 maternities from 884 spawners with an LOD value > 3.0, the identified maternity-offspring relationship comprised of these six following cases: among most of traced maternities(253), only one of offspring was detected; in 62 traced maternities, each have two offspring were detected. The other three minor cases were 18 maternities corresponding three traced progenies each, 3 maternities corresponding four progenies each and 1 maternity corresponding five progenies. For Laizhou Bay populations, total 155 offspring from 288 recapture samples were traced to their 135 maternities from 1016 spawners with an LOD value > 3.0, among most of traced maternities(116), only one of offspring was detected; in 18 traced maternities, each have two offspring were detected. The other three minor cases were 1 maternities corresponding three traced progenies. In the combination with details of sampling batches of F. chinensis in 2015, the distribution of release shrimps population in Laizhou bay was similar to natural population. A certain percentage of the Laizhou bay release population was detected in Bohai bay. The Laizhou bay release population had the characteristics of widespread distribution and active in migration.