Observation On Molting,growth And Fattening Of Chinese Mitten Crab In The “crab Palace” Individual Culture System

Chinese mitten crab(Eriocheir sinensis),commonly named as river crab,is a kind of importantly valuable aquatic animal in China.This crab is aggressive and like snatching food with each other,which result in the low survival rate and whole production during the cultivation.Therefore,it tends to make people pay attention to the individual cultivation.However,a few studies have be conducted on individual cultivation for Chinese mitten crab because of some restricted condition such as the specific facility to raise it and domestic experiments to rare it.In this paper,by using of the “palatial” Chinese mitten crab individual cultivation system— “crab palace” developed by our group and the Shanghai Hongxun Environment Technology Company Ltd,which is fully enclosed and has automatic temperature control of circulating water,we observed the individual molting,growth,maturity and fattening characteristics of the Chinese mitten crab.The aims were to assesses the feasibility of the individual cultivation with “crab palace”,and to provide some related data and information for individual cultivation of other aquatic animals in this system.Related results are as follows.Part 1.Observation on growth characteristics of Chinese mitten crab reared in “crab palace” with one-molting cycleIn this chapter,we observed the individual molting and growth of Chinese mitten crab in a single molting cycle,and analyzed the characteristics of related hormones and gene expression of the crabs reared in the “crab palace” system.The results showed that the survival rate of the crabs reached 79.00% and the average molt-interval period was 54 d,the increment rates after molting for body weight,carapace length,carapace width and body height were 30.51%,8.46%,9.96% and 10.19%,respectively.The average ecdysone hormone(EH)content at the premolt stage was 18.14 IU/m L.Meanwhile,the expression levels of Ec R and CHH genes were high and the expression level of MIH gene was low at the premolt stage.There was not significant correlation between molt-interval,increment rates and EH content(P>0.05).Similarly,no significant correlation were found between molt-interval,increment rates and expression levels of Ec R,CHH,MIH genes(P>0.05).The results indicated that it was feasible for molting and growth of Chinese mitten crab reared in “crab palace” system.Part 2.Observation on growth characteristics of Chinese mitten crab reared in “crab palace” with multiple-molting cyclesIn order to investigate growth characteristic of Chinese mitten crabwith multiple-molting cycles reared in the “crab palace” system,we conducted molting and growth observation on the crab under three molting cycles.The results showed that the survival rate of the third to fifth molting cycle was 95.60%,83.52% and 69.23%,respectively.The average increment rate for body weight were 40.35%,38.03% and 36.76%,respectively.The average increment rate for carapace length was 12.22%,11.29% and 11.65% respectively.The average increment rate for carapace width was 11.77%,10.29% and 11.34% respectively.The average increment rate for body height was 12.24%,13.49% and 13.90%,respectively.Furthermore,the average molt-interval period for the third to fifth molting stages was 44,66,and 56 d,respectively,indicating extremely significant difference(P<0.01)between the third and fourth molting stage,and significant difference(P<0.05)between the third and fifth molting stage.The average conditional factors for the three molting stages was 64.55%,61.13 % and 61.27%,respectively,showing extremely significant difference(P<0.01)between the third and the fourth,fifth molting stages.After the fifth molting,the hepatopancreas index was 3.55% and the gonadosomatic index was 0.83%.We also found a large amount of mature sperm in male testis and large growth oocyte in female ovaries under histological observation.This study showed that Chinese mitten crab reared in “crab palace” system could normally molt,grow and reach mature.Part 3.Observation on individual nursing and fattening of Chinese mitten crab reared in “crab palace”In order to investigate the feasibility and effectiveness of individual nursing of Chinese mitten crab(Eriocheir sinensis),This chapter carried out the experiment of individual crab raising and fattening of the crab,and two kinds of preservation styles were employed,namely,preservation A group was added 1‰ of glucose and 1‰ of sodium glutamate as the nutrient solution in the circulating water and preservation B group was not added the nutrient solution.The results showed that the survival rate was 71.43 and 73.21% for A,B groups,respectively.Compared with before preservation,the weight,fatness and redness degree of carapace were significantly increased(P<0.01),and sweetness in hepatopancreas from the preservation A group was also significantly improved.There was no significant difference for the contents of amino acids and fatty acids in the hepatopancreas between before and after perservation,but the content of amino acids in the gonads was significantly increased by preservation.The essential amino acids,aromatic amino acids and total amino acids in gonads raised 32.10-49.11%,51.75-89.99% and 50.70-80.71% by preservation.There was significantly decreased in monounsaturated fatty acid(MUFA)after preservation(P<0.01),and no significant differences were found in saturated fatty acids(SFA)and polyunsaturated fatty acids(MUFA)between before and after preservation(P>0.05).This study indicated that the “Individual breeding system” is feasible in carrying out individual culture,fattening and improving the amino acid nutrition quality in gonad of Chinese mitten crab.