| When high dams discharge flows of high velocity will lead to the total dissolved gas supersaturation,which will threats the survival of aquatic organisms,especially those valuable and rare fishes.So the problem caused by dam discharge has become a focus for researchers and protectors of the ecological environment,and has become one of the problems in assessing the ecological risk of water environment.The study of gas supersaturation started earlier abroad,which has achieved a lot of research results in terms of the mechanism of gas supersaturation,the factors affecting the supersaturation of water bodies,the measures to slow down and reduce the dissolved gas supersaturation in water,and the effect of gas supersaturation on fishes.Domestic studies started relatively later,which mainly focused on prototype observations,mechanism of occurrence,fish tolerance,avoidance behavior,and the influence of gas supersaturation on related enzyme activity of fish.However,the effect of gas supersaturation on early development and blood gas of fish have rarely been reported.Based on the above research,the fertilized egg,the early juvenile fish and a young adult Hypophthalmichthys molitrix as the research object in this study to research the effect of the different supersaturated water on fertilized egg,larvae,and blood gas of silver carp.The different supersaturated water was generated with the supersaturated water generating device.The purpose of this study is to evaluate the influence of Total Dissolved Gas(TDG)supersaturation water and change of blood physiological in fertilized egg and larvae,to enrich the research data of the gas supersaturation effect on fish,and to provide reference for the development of ecological protection measures for fish that are in jeopardy.The main research results are as follows:1.The different concentration of TDG supersaturation changed the hatching time,hatching rate of fertilized eggs in different levels at the same temperature.The most notable was fertilized eggs in 110% supersaturated water,whose hatching time was the shortest at 21±0.5°C water temperature.The peak time for hatching emergence was approximately 38.5h in 110% supersaturated water,which was about 3 hours earlier than the control group,and the hatching rate was 92.3%,which significantly higher than the control group 88.7%.At the same temperature,the total dissolved gas supersaturation water had no significant effect on the developmental rate and deformity rate of the fertilized egg,and did not cause fertilized egg getting the gas bubble disease.2.Further observation of post-embryonic incubation revealed that both the experimental and control groups experienced about 5 days of post-embryonic development,and there was no significant difference in development time and development speed.Counting the number of fries deaths in post-embryonic development,the results showed that the fries mortality of 110% experimental group was significantly increased compared with the control group and other experimental groups(P<0.05),which caused the hatching rate of 110% experimental group was significantly lower than other groups(P<0.05).The final survival rate of the control group was 97.8%,while the 110% test group final survival rate was 71.5%.The final survival rate of 120%,130% and 140% experimental group were all higher than 110% in the experimental group,and the survival rate increased slightly as the supersaturated concentration increased.The survival rate of 120%,130%,and 140% experimental group were 92.4%,93.4%,and 93.9%,respectively,and there was a significant difference compared with the control group(P<0.05).The deaths of the fries in the experimental groups were mainly concentrated on the 2nd to the 3rd days after the hatch was taken out.The average mortality of the 110% test group on the 2nd day of the film was 13.6%,and on the 3rd day was 13.7%,which were all higher than other groups(P<0.05).3.The tolerance of silver carp larvae and juveniles at 15 d,25d,35 d,45d,and 120 d growing time in different TDG saturation water was observed.It was found that fries with shorter growth time have higher tolerance to supersaturated water,and the 96-hour mortality rate showed that the mortality of 15 d fries was only 0.9%-2.5%,but the mortality of fingerlings grown for 120 days was as high as 86%-100%.The tolerance of the same fries in different concentrations of supersaturated water decreased basically as concentration of supersaturated water increased.4.The analysis results of blood gas of silver carp exposed to dissolved gas supersaturated water for 4 hours showed that all the p H of silver carp in the experimental group was lower than the control group,and there was a significant difference between the severe exposed group and the control group(P<0.05).The levels of BEecf,AB,and TCO2 in the experimental group were lower than the control group,and a significant difference existed between the severe exposure group and the control group(P<0.05),while p CO2,p O2 were higher than control group,and the p CO2 level was significantly higher in the severe exposure group than in the control group(P<0.05).SO2 decreased with the increase of TDG supersaturation,and the severe exposure group was significantly lower than the control group and moderate exposure group(P<0.05).The above results indicated that the supersaturated water caused the silver carp acidosis. |
PDF Full Text Request