Study On The Influence Of Predators On High Mortality In The Early Stage Of Bottom-released Pacific Abalone

Pacific abalone（Haliotis discus hannai Ino）is an important fishery resource and cultured species in China.Since the 1970s,the resources of wild Pacific abalone have declined rapidly to nearly depletion.With the development of artificial breeding technology,Pacific abalone bottom-seeding culture has developed rapidly in the 1990s,but the problem of high mortality in the early stage after release is a long-term challenge.In this study,based on the resource survey in the bottom release sea area of Pacific abalone,the relationship between the density of abalone and the abundance of algae and predators after bottom-seeding was discussed.Furthermore,the predation effects of predatory organisms（Japanese sturgeon,starfishes）on Pacific abalone of different sizes were studied.Finally,the transcriptome method was used to preliminarily explore the differential genes under short-term and long-term predatory stress.The details of the research contents and results are as follows:1.In this study,resource density such as abalone,algae,and predatory organisms were investigated in Pacific abalone bottom release areas in Changdao,Shandong.Using the SCUBA underwater camera survey method,the survey site included the sea area where the bottom-seeded abalone is released for about 2 weeks.The survey results showed that the resource of abalone in Changdao is 0.93-1.04 inds/m^2,and the density of Asterias amurensis/Asterina pectinifera is 6.67-7 inds/m²,Charybdis japonica density is 0.05-0.35 inds/m²,abalone population density was significantly negatively correlated with predators（P<0.05）.This study preliminarily revealed the correlation between the early mortality of abalone and the predatory predation.2.In this study,two tagging methods,metal clip and glued plastic labels,were used to systematically compare the differences in physiology,and survivals to predator of Pacific abalone.Compared with the glued plastic label stagging method and the controls,the metal clip tagging has a significant impact on the early physiological performances of Pacific abalone,including the appearance of mucus,heart rate,etc.,especially on the small size group（shell length<3cm）,which causes a decrease in growth and an increase in mortality.Compared with the glued plastic tagging and controls,there’re no differences on survivals to predators after 60days after the large-size on abalones（shell length>3cm）with clip tagged metal clips.Compared with the untagged control group,there’re no significant differences of the plastic labeling method on Pacific abalone performance.This study verifies the effectiveness and applicability of the two labeling methods at the individual level of the abalone,and provides relevant technologies and methods for the next study of predatory indoor predation simulation.3.The predation selectivity and the bait selection coefficient of three predatory species,Charybdis japonica,Asterias amurensis,and Asterina pectinifera,on different sizes of Pacific abalone were compared.Results showed that Asterias amurensis,and Asterina pectinifera did not have significant predation behaviors on the abalone.However,the result might also be related to the experimental water temperature and other conditions.While,Charybdis japonica of different sizes prefers small size abalone,and the predation efficiency of large size Charybdis japonica is significantly higher than that of small size Charybdis japonica（P<0.05）.In addition,when using 5 kinds of biological food to trap Charybdis japonica,chicken breast had the best trapping effect and was significantly higher than other biological food（P<0.05）.This study verifies the predation behavior of the predatory creatures,especially the Japanese sturgeon on Pacific abalone.4.In order to reveal the molecular mechanism of the response to predatory stress of abalone,the transcriptome sequencing of the abalone samples under different stress times（1days,15 days and control）was performed.The results of transcriptome sequencing,assembly and comparison showed that there were 253 and 30 differentially expressed genes between short-term stress and control group in gill and muscle tissue,and 562 and 329 differentially expressed genes between long-term stress and control group.GO functional enrichment results showed that the functions of differentially expressed genes between different groups were divided into biological process,cellular component,and molecular function;KEGG enrichment analysis showed that differentially expressed genes were concentrated in endocrine and Metabolic pathways such as calcium reabsorption and thiamine metabolism regulated by other factors.The results of this study provide basic information for the determination of gene functions related to hostile stress response in the future.This paper has 22 figures,6 tables and 119 references.