| The red swamp crayfish(Procambarus clarkii)is the most highest-yielding freshwater crayfish in the world at present.It has become one of variations with the most rapid development,characteristic and potential in Chinese aquaculture.Crayfish are mostly coveyed by off-water transportation in the aquaculture production.The final aquaculture production and commercial benefits are directly related to the survival rate of crayfish after long-distance transportation.In this study,the juvenile and broodstock of P.clarkii were studied,and the survival and physiological function of juvenile and broodstock of crayfish were studied with different off-water time in different months.On this basis,some drug treatments were used to explore the impact of immune preparations on the survival rate of juvenile crayfish after transportation,and explore the mannose oligosaccharide type II on the survival and growth of crayfish broodstock after transportation.The main results are shown as follows:1.To understand the effect of off-water transportation time on the survival and physiological function of juvenile crayfish during transportation,the survival rate and physiological indexes of juvenile crayfish with different off-water time(1 h,2 h,3 h,4 h,5 h,6 h,7 h,8 h)were studied in April and May.The causes of high mortality and countermeasures for safe transportation were discussed.The results showed that the survival rate of juvenile crayfish could reach more than 95% in the transportation stage within eight hours.During the transportation stage in April,the SOD and GSH-px activities in the muscle of juvenile crayfish showed a trend of increasing first and then decreasing with the increase of off-water transportion time.In the temporary culture stage,the survival rate of juvenile crayfish in April showed a downward trend with the increase of off-water transportion time.The survival rate of juvenile crayfish in 1 h off-water transportion treatment was significantly higher than that in 7 h and 8 h treatments(P <0.05).And the survival rate of juvenile crayfish in April was significantly higher than that in May.The deaths of juvenile crayfish in all treatments in the temporary culture stage mainly occured within one week after stocking.It was suggested that juvenile crayfish should be screened and transported in April.To ensure the quality of the juvenile crayfish,the nearest seedling farms should be selected.and the nearest juvenile crayfish should beselected on the premise of ensuring the quality of the juvenile crayfish,so as to reduce the off-water transportation time.2.In order to understand the impact of immune preparations on the survival rate of juvenile crayfish after transportation,a two hour off-water transportation was simulated.After transportation,different immune preparations were set up for related drug treatments.The treatments involved as follows: blank treatment group,water quality treatment group,disease treatment group,feed treatment group,full treatment group.The results showed that the survival rate of juvenile crayfish after transportation in feed treatment group was significantly higher than that in blank treatment group(P < 0.05),and there was no significant difference between the other treatment groups and control group(P > 0.05).Moreover,the microecological preparations feed can significantly increase the survival rate in the temporary rearing stage after off-water transportation,and significantly promote the growth of juvenile crayfish.3.To understand the effect of off-water transportation time on the survival of crayfish broodstock during transportation,the survival rate and growth of crayfish broodstock with different off-water time(1 h,3 h,5 h,7 h,9 h)were studied in July,August and September.The causes of high mortality and countermeasures for safe transportation were also discussed.The results showed that the survival rate of crayfish broodstock could reach more than 95% in the transportation stage within nine hours.In the temporary culture stage,the survival rates of crayfish broodstock in all three experimental months showed a downward trend with the increase of off-water transportion time,the survival rate of crayfish broodstock in 1 h treatment was significantly higher than that in 7 h and 9 h treatments(P < 0.05).And the survival rates of crayfish broodstock showed significant differences among the three different transportation months,the lowest in July and the highest in September.The deaths of crayfish broodstock in all treatments in the temporary culture stage mainly occured within one week after stocking,and the mortality rate on days 2?5 after stocking accounted for 60.1% of the total mortality.Under the condition of the same off-water transportation time,the growth of crayfish broodstock in the temporary culture stage significantly differed in different months.It was suggested that crayfish broodstock should be screened and transported in September.To ensure the quality of the crayfish broodstock,the nearest seedling farms should be selected,so as to shorten the off-water transportation time.4.In order to understand the feasibility of using the new immune enhancer manno-oligosaccharide type II in P.clarkii breeding,the stocking experiment was set up at different dosage of manno-oligosaccharide type II(0,0.05%,0.1%,0.2%)after three hours' off-water transportation.We explored the effect of manno-oligosaccharide type II on survival rate and physiological function of the crayfish broodstock.The results showed that survival rates of each treatment group were significantly different after two weeks of temporary culture in pond(P < 0.05).Compared with the blank group,survival rates of the 0.05% group,0.1% group,and 0.2% group increased significantly(P < 0.05).Compared with the 0.05% group,the survival rate of the 0.1% group and 0.2% group significantly increased as well(P < 0.05).There was no significant difference in survival rates between the 0.1% group and 0.2% group(P > 0.05).For each treatment group,the activities of T-AOC,CAT,PO,ACP,and ALP in the P.clarkii broodstock increased to different degrees compared to the control group.Compared with the control group,the content of T-AOC,CAT,PO,ACP and ALP in serum,liver and pancreas incresead in the 0.05% group(P < 0.05),while only the content of ACP and ALP significantly increased in the 0.1% group(P < 0.05).With the increase of mannose-oligosaccharide type II,the activities of T-AOC,CAT,PO,ACP and ALP in crayfish broodstock showed a downward trend. |
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