The Preliminary Study Of Growth Of Chinese Mitten Crab(Eriocheir Sinensis)in Larval And Juvenile Stages

The specific growth pattern of Chinese mitten crab Eriocheir sinensis during the juvenile stages was investigated under an individual rearing system for a total of 180 d,including parent crab selection,hatchery management,larval stages and juvenile cultivation.The crabs developed from megalopa to juvenile crab stage 10?C10?with a mean accumulated survival of 38?.The survival rate in different moulting times was relatively lower in the early stages than in the late stages.From megalopa to juvenile stage 3?C3?,survival remained at less than 80%.The intermoult duration sharply increased in a logarithmic manner from 4 ± 0.54 d to 38 ± 6.26 d.The increases in wet weight,carapace width and carapace length?WW,CW and CL,respectively?per moult were recorded throughout the entire experiment.These primary growth parameters?WW,CW and CL?followed certain patterns with progressing moulting time.In addition,the WW gain??WG?varied at a high level from C1 to C6 with a minimum increment of 108.09%.Meanwhile,the specific growth rate?SGR?markedly increased in the early stages and subsequently decreased,mainly due to the significant increase in intermoult duration starting from C6 stage.Males and females can be differentiated at C4 according to the shape of the abdomen and other morphological differences.Effects of stocking densities and diets on growth and survival of Chinese mitten crab?Eriocheir sinensis?during its larval stages?C1-C3?were tested under laboratory conditions.Four stocking densities D1?75 ind/m₂??D2?150 ind/ m₂??D3?300 ind/ m₂?and D4?450 ind/ m₂?were designed.The result shows that the body weight obtained the highest value in D2,and was significantly higher than D3 and D4 in C1 and C2 satges?P<0.05?.Survival rate declined significantly with the increasing larval stages,and obtained the highest result in D1 and D2,followed by D3 and D4.In addition,the relative contents of HUFA and n-3PUFA in C1 stage reared with lower stocking densities D1 and D2 are significantly higher than D3 and D4?P<0.05?.As to dites experiment,larval crab fed with formula diet obtained highest body weight compared to mixed diet and live diet,especially in C1 and C3 stages?P<0.05?.Survival rate reached the highest in F1,followed by F2 and F3 and larva crabs fed woth live diet obtained the lowest survival rate in C2 and C3 stages?P<0.05?.The relative content of total lipid was the lowest in larval crabs fed with live diet,which was the same variation trend as HUFA,n-3PUFA and n-6PUFA?P<0.05?.The results proved that stocking densities and diets had significant effects on growth and survival in larval stages,which may provide some basic information to improve the production of larval mitten crabs.Effects of different types of shelter on growth and survival of Chinese mitten crab?Eriocheir sinensis?during its larval stages?C1-C3?were tested under laboratory conditions.Four shelter types S1?Alternanthera philoxeroides??S2?PVC??S3?mixed shelters?and S4?unsheltered?were designed.The result shows that body weight varied greatly in different shelter conditions,which obtained highest value in S1 and S3,followed by S2 and S4.Body weight obtained in S4 in C1 and C2 stages was significantly lower than S1 and S3?P<0.05?,while the body weight in C3 obtained in S3 was significantly higher than that in rest treatments.The carapace in S3 was significantly higher than the rest groups?P<0.05?and obtained lowest value in S4.Survival rate declined significantly with the increasing larval stages,and obtained the highest result in S3,followed by ohter treatments.In general,mixed shelters obtained a better performence to improve the survival rate of larval crabs.Result of DO presented that the DO was higher in daytime than that in night,and the DO obtained highest value in S1 and S3 was significantly higher than S2 and S4 in the daytime?P<0.05?,while the DO was lowest in S1 in the night and was significantly lower than S2 and S3.This present study proved that the growth and survival of larval stages obtained in S3 was better than rest shelter conditions,which provided adirections in further study on laval crab stages.