Study On Growth,Development And Nutritional Quality Of Eriocheir Sinensis In Large Water Surface Ecological Stocking

According to the resource conditions of lakes,reservoirs and other water areas in northern China,the ecological stocking of Eriocheir sinensis on large water surface is carried out by means of"human release and natural breeding"with the main goal of realizing ecological protection and resource proliferation.Based on the long-term tracking and investigation of the growth dynamics of Eriocheir sinensis in Jiang Wan reservoir in Harbin and Nan Yin reservoir in Da Qing,the growth and gonadal development of Eriocheir sinensis in large water surface ecological stocking in northern China were studied.At the same time,the nutritional quality of the two water mature Eriocheir sinensis was analyzed and compared,so as to provide data support for the ecological breeding and fattening of Eriocheir sinensis by making full use of the freshwater water space such as lakes and reservoirs in the later stage.1.Study on water quality,plankton and growth and development of Eriocheir sinensis in Jiang Wan reservoirThe water quality,plankton resources and growth dynamics of Eriocheir sinensis in Jiang Wan reservoir were studied by means of water quality physical and chemical index analysis,plankton resource investigation,stocking experiment and anatomy.The results show that:（1）the physical and chemical indexes of water quality of Jiang Wan reservoir,SD is 0.33-0.49 m;PH is 7.44-8.19;DO is 6.93-9.57 mg/L;The alkalinity and total hardness are 70.17 mg/L and 85 mg/L respectively;NH₄⁺-N is 0.02-0.27mg/L;TN and TP were 2.73 mg/L and 0.12 mg/L respectively;NO₂-N is 0.00-0.16mg/L;COD_Mn was 7.85 mg/L.There was significant difference in Chla content between different months,and the highest Chl a content was 63.61 ug/L in August.The comprehensive nutritional status index evaluation and classification method were used to determine that the water nutrition degree of Jiang Wan reservoir was moderately eutrophic.（2）The average density of phytoplankton in Jiang Wan reservoir during the stocking period of Eriocheir sinensis was 30.12×106 ind/L,with an average biomass of 10.73 mg/L;The average density of zooplankton is 236.69 ind/L and the average biomass is 0.49 mg/L.There are significant differences in the density and biomass of plankton in different months.The density of phytoplankton is higher from July to September,and the biomass of phytoplankton is higher in May,July and September.The density and biomass of zooplankton were higher in May and July,and the density and biomass of phytoplankton began to drop sharply after October.According to the estimation of fish productivity,the total fish productivity of Jiang Wan reservoir is175.92 kg/hm².（3）The reproductive molting of Eriocheir sinensis in Jiang Wan reservoir began in August,and the reproductive molting of female crab was earlier than that of male crab.In October,all female crabs completed reproductive molting,and the reproductive molting rate of male crabs was 92%.In terms of gender differences,GSI and TEY of female crab were significantly higher than those of male crab,and CF of male crab was significantly higher than that of female crab（P<0.05）.（4）The average body weights of female and male adult crabs in Jiang Wan reservoir were（67.62±1.50）g and（74.88±2.19）g respectively.The total annual output of Eriocheir sinensis is about 15 t.During the stocking experiment,the recapture rate of Eriocheir sinensis larva was 2.06%.In conclusion,the water body of Jiang Wan reservoir is highly eutrophic,and the plankton resources in the water body are relatively rich.The average weight of adult Chinese mitten crab is low,but the total annual output is considerable.According to the fish productivity evaluation of Jiang Wan reservoir,the water resources of Jiang Wan reservoir have been fully utilized.2.Study on growth and development of Eriocheir sinensis in ecological stocking in Nan Yin reservoirThis study investigated the growth dynamics of Eriocheir sinensis in the ecological stocking stage of Nan Yin reservoir.The results showed that:（1）in the growth stage of crab,Eriocheir sinensis in Nan Yin reservoir began to appear precocious crab in September.In October,the precocious rate of female crab was 40.9%,and that of male crab was 53.62%.There were significant differences in GSI,my and CF between sexually precocious female and male crabs.The GSI of female crabs was significantly higher than that of male crabs,and the MY and CF of male crabs were significantly higher than that of female crabs（P<0.05）.From August to October,the weight of female crab is slightly higher than that of male crab.The average terminal weights of male and female normal crab were（23.65±0.99）g and（23.14±1.25）g respectively,and the average terminal weights of male and female precocious crab were（38.86±1.48）g and（38.70±1.11）g respectively.The weight of normal male crab is mainly distributed at（20.00-24.99）g,while the weight of female crab is mainly distributed at（25-29.99）g.the weight of male crab is more dispersed than that of female crab.（2）In the growth stage of adult crab,Eriocheir sinensis in Nan Yin reservoir began reproductive molting in July.The GSI of female and male crabs increased significantly from July to October,and the increase of GSI of female crabs was the highest from August to September.HSI of female crab reached the highest in August,and then decreased gradually.The HSI of male crab reached the highest in September,and then began to decline.There was significant difference between the average weight of female and male crabs in August and September（P<0.05）.The average weight of male crabs was significantly higher than that of female crabs.The average body weight of female and male crabs were（84.76±1.50）g and（99.31±2.65）g respectively,and the average body weight at the end was mainly（85.00-99.99）g.In conclusion,the precocious rate of crab in Nan Yin reservoir is high,and there is no significant difference in the total edible rate TEY.The reproductive molting time of adult crab is earlier,the development time of male and female gonads is not synchronous,and the average final weight of adult crab is higher.3.Analysis on nutritional quality of Eriocheir sinensis in ecological stocking in large water surfaceThe nutritional quality of sexually mature crab in Nan Yin reservoir and Jiang Wan reservoir was compared by means of stocking experiment,anatomy,biochemical composition analysis,fatty acid and free amino acid analysis.It mainly includes the total edible rate,plumpness,conventional nutrients,fatty acids and free amino acids of NY precocious,NY normal and Jiang Wan normal crabs.The results showed that:（1）there were significant differences in edible rate and plumpness between NY precocious crab,NY normal crab and Jiang Wan normal crab.Among the three groups of sexually mature crabs,there was significant difference in HSI among female crabs（P<0.05）.From high to low,the order was NY precocious crabs>NY normal crabs>Jiang Wan normal crabs.There were significant differences in MY and TEY between NY precocious female crab and NY normal female crab and Jiang Wan normal female crab（P<0.05）.There were significant differences in HSI and MY between NY precocious male crab and NY normal male crab and Jiang Wan normal male crab（P<0.05）.Except for GSI of male crab,there was no significant difference in edible rate and plumpness between NY normal crab and Jiang Wan normal crab.（2）In terms of routine nutrition,there are many differences between NY normal crab and NY precocious and Jiang Wan normal crab.The contents of crude protein and total fat in hepatopancreas,gonad and muscle of female crab were significantly different,while the contents of water and total fat in hepatopancreas of male crab were significantly different（P<0.05）.The contents of water,crude protein and total fat in muscle of Jiang Wan normal male crab were significantly different from those of NY precocious and NY normal crab（P<0.05）.（3）The differences of fatty acids among the three groups of sexually mature crabs mainly exist between Jiang Wan normal crabs and NY precocious and NY normal crabs.ΣSFA in hepatopancreas and gonads of Jiang Wan normal crab was significantly lower than that of NY precocious and NY normal crab,whileΣPUFA was significantly higher than that of NY precocious and NY normal crab（P<0.05）.C20:5n3（EPA）,c22:6n3（DHA）,Σn-3PUFA andΣHUFA in the gonads of Jiang Wan normal crabs were significantly higher than those of NY precocious and NY normal crabs,and c16:1n7 andΣMUFA in the gonads of Jiang Wan normal female crabs were significantly lower than those of NY precocious and NY normal crabs（P<0.05）.Except for SFA,there was no significant difference inΣMUFA,c20:5n3（EPA）,c22:6n3（DHA）andΣPUFA among the three groups（P>0.05）.（4）Except arginine Arg,there was no significant difference in the content of free amino acids in the muscle between NY normal and Jiang Wan normal female crabs（P>0.05）.There were many differences between NY precocious crab and NY normal crab and Jiang Wan normal crab.There were significant differences in Asn,Glu,Gln,ala,met,Leu and Phe in female crab（P<0.05）.Except for Gln and Ala,there was no significant difference in the content of free amino acids between NY precocious and NY normal male crab muscles（P>0.05）.The contents of Asp,Glu,Trp,ile and Tyr in Jiang Wan normal crab were significantly higher than those in NY precocious crab and NY normal crab（P<0.05）.The main flavor amino acids in muscle are Ala,Arg and Gly,and the main flavor amino acids in female crab and male crab muscle are the same.