| Coilia nasus is a kind of typical migratory fish species,mainly distributed in the Bohai sea,yellow sea,east China sea,the middle and lower reaches of the Yangtze river and its subsidiary lake,is one of the Yangtze river important economic fish.living in offshore at ordinary times,every year in mid-february Coilia nasu starts spawning migration by sea into the river,in general,do not eat during the migratory.Fully rely on the accumulation of energy to complete the long distance migration,migration process with the development of the gonads,the accumulation of energy before migratory is essential to the smooth completion of the spawning migratory process.In recent years,the resource quantity of Coilia nasus has been seriously declining,the flood season time has been reduced or even unable to form fishing floods,and the migration distance has been shortened.A series of serious problems,such as the protection of Coilia nasus,are imperative.The study of energy ecology in the process of Coilia nasus migration can explore the change rule of main energy carrier in the process of Coilia nasus reproductive migration and understand the energy utilization in the process of Coilia nasus migration.The fat and protein stored in fish body are the main energy sources to support their migration to spawning ground and development.In this study,the content and components of fatty acids in the main energy-storing tissues(liver,muscle and ovary)during the migration process were analyzed to further analyze the transfer of fatty acids in various tissues during the development of ovary.The analysis of energy substances in serum is helpful to explore the metabolic process of fat,protein and other main energy substances in the migration of Coilia nasus from the aspect of hematology.Reference to relevant research methods,this study with a Coilia nasus as the research object,in 2019～2020 in the Yangtze river downstream of Chongming,Zhenjiang,Dangtu,Anqing section to collect the required test samples,whole fish of Chongming and Anqing section acquisition main energy carrier and can measure value of samples,analyzes the main energy carrier and Coilia nasus can value the characteristics of space and time;The energy index of serum samples collected from Chongming,Zhenjiang and Anqing River sections was measured to analyze and compare the changes of serum energy substance in each section and each development stage.Method of using methyl boron trifluoride Coilia nasus liver,muscle and ovary tissue for determination of fatty acids,analyzed the migration distance and puberty(Ⅱ,III and IV period)and different length specifications(250±10、300±10 and 350±10mm)fatty acid content and composition change trend between organizations,discusses the Coilia nasus fatty acid transfer law between organizations in the process of migration.From two aspects of energetics and hematology study systematically,in order to find out the Coilia nasus whole fish reproductive migratory process main energy carrier,blood energy index and fatty acid content and composition change rule,for the Coilia nasus nutrition composition and energy ecology provides basic data,enrich its basis of hematology indexes,and provide theoretical basis for further Coilia nasus breeding work.The main results are as follows:1.During the migration from Chongming to Anqing,the whole body fatness coefficient,water content,dry matter weight,crude protein content,crude fat content and energy content of whole body were 0.31%-0.42%,69.15%～72.61%,35.92g～22.69g,60.15%～63.29%,31.77%～22.77%and 1720.46kJ～1098.09kJ.When Coilia nasus migrated from Chongming to Anqing section,the body fatness,dry matter weight,crude fat and whole body energy value decreased significantly(P<0.05),by 26.19%,36.83%,28.33%and 36.17%,respectively.Two batches of experimental samples from the beginning and end of June in Anqing section.The whole body fatness coefficient,water content,dry weight,crude protein content,crude fat content and whole body energy content were between 0.31%～0.32%,14.45g～15.05g,73.10%～73.77%,61.49%～62.79%,27.65%～28.64%and 705.36kJ～756.55kJ,respectively.There were no significant differences in water,dry matter weight,crude fat,crude protein,fatness and energy of whole fish(P>0.05)from the beginning of June to the end of Anqing section,and they all maintained a relatively stable state.12 groups of Coilia nasus samples with body length ranging from 230 mm to 350mm were collected in Anqing section.The whole fish fullness coefficient was 0.27%～0.35%,with an average value of 0.31%.The water content ranged from 67.51%to 76.39%,with an average of 73.30%.The dry matter mass ranged from 11.48g to 39.87g,with an average of 15.98g.Crude protein content ranged from 52.44%to 71.27%,with an average of 60.64%.The crude fat content ranged from 15.92%to 36.97%,with an average of 27.97%;The emergy of whole fish ranged from 637.13 kJ to 2388.63 kJ,with an average value of 866.94 kJ.2.The contents of total protein and triglyceride in Chongming to Zhenjiang section were significantly decreased(P<0.05),by 19.36%and 29.29%,respectively;The contents of high density lipoprotein and free fatty acid were significantly increased(P<0.05),by 60.38%to 23.65%;There were significant changes in lipid related indexes such as triglyceride,high-density lipoprotein and free fatty acid in serum samples of Coilia nasus(P<0.05),indicating that lipid metabolism was active in the early period of migration,and fat should be the main energy supply substance for its migration and development.From Zhenjiang to Anqing section,the contents of serum total protein,triglyceride,high-density lipoprotein and free fatty acid had no significant difference(P>0.05).The metabolic level gradually adapted to the energy demand of migration and gonad development,so the serum energy index of Coilia nasus tended to be stable in the later period of migration.The results showed that the triglyceride content of Coilia nasus at stage Ⅳ was significantly higher than that of stage Ⅱ and stage Ⅲ(P<0.05),increased by 67.24%and 53.75%respectively,and there was no significant difference in other indexes among the samples at different stages(P>0.05).3.28 kinds of fatty acids were detected in liver,muscle and ovary tissues of Coilia nasus migratory to different river sections,different development stages and different length of migratory body,including 8 SFA,6 MUFA and 14 PUFA.With the extension of migration distance,the total fatty acid content of liver showed an upward trend,from 526.61 mg/g in Chongming section to 587.21 mg/g in Anqing section,increased by 60.60 mg/g,and did not reach significant difference(P>0.05).On the contrary,the contents of total fatty acids in muscle and ovary decreased significantly(P<0.05).The total fatty acid content of muscle decreased by 9.09%from 584.35 mg/g in Chongming to 531.23 mg/g in Dangtu,and decreased by 26.33%from 531.23 mg/g in Dangtu to 391.36 mg/g in Anqing.The total fatty acid content in ovary decreased significantly from 811.82 mg/g in Chongming to 348.38 mg/g in Anqing(P<0.05),which was reduced by 28.84%in Chongming to Dangtu and 39.70%in Dangtu to Anqing.With the development of Coilia nasus gonad from stage Ⅱ to stage Ⅳ,the total fatty acid content in muscle decreased from 435.72 mg/g in stage Ⅱ to 338.12 mg/g in stage Ⅳ,in which the content decreased by 14.27%from stage Ⅱ to stage Ⅲ and 9.48%from stage Ⅲ to stage Ⅳ(P>0.05);the total fatty acid content in liver decreased from 558.98 mg/g to 293.14 mg/g,in which the content decreased by 8.21%from stage Ⅱ to stage Ⅲ and 42.87%from stage Ⅲ to stage IV(P<0.05).In contrast to muscle and liver,the total fatty acid content in ovary increased from 364.17mg/g to 418.95mg/g,with an increase of 10.59%from stage Ⅱ to stage Ⅲ and 3.93%from stage Ⅲ to stageⅣ(P>0.05).There was no significant difference in the total fatty acid content in liver,muscle and ovary among the three body length groups(250±10 mm,300±10 mm and 350 ± 10 mm)(P>0.05).The total fatty acid content in muscle increased from 351.24 mg/g of 250 ± 10 mm body length to 450.57 mg/g of 350 ± 10 mm body length The total fatty acid content in liver decreased first and then increased,from 536.61 mg/g to 469.14 mg/g,decreased by 12.57%,and then increased from 469.14 mg/g to 496.25 mg/g,increased by 5.78%;on the contrary,the total fatty acid content in ovary and liver increased first and then decreased,from 432.07 mg/g 33 mg/g,increased by 2.84%,and then decreased from 444.33 mg/g to 410.27 mg/g,decreased by 7.67%. |
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