Effects Of Riverbed And Mechanical Shock On The Hatching Of Drifting Fish Eggs

In order to deeply implement the Yangtze River protection and restore fish resources,the most important thing is to improve the egg production and its hatching rate from the source.During the transportation of drifting fish eggs in rivers,they can encounter various kinds of high velocity impacts or low velocity stagnation and burial,resulting in egg defeat and broodiness.Therefore,the main content of this paper is to design and carry out indoor flume tests and field field experiments.First,in order to study the suspended velocity values of drifting fish eggs on different riverbed under low velocity,three kinds of bed surfaces,smooth glass,pebble and dense aquatic grass,are used for quantitative judgment based on the binary suspension screening criteria,and the suspended velocity of fish eggs under the three kinds of bed surfaces is obtained by analyzing the vertical and vertical aspects respectively,To ensure the suspension of fish eggs and improve the hatching rate;The second is to study the impact on the hatching process of drifting fish eggs after they are subjected to instantaneous mechanical impact in the process of migration with the water.Through the field fishing eggs and eggs in the spawning ground as the research objects,the design experiments are conducted from four aspects:the instantaneous impact speed of fish eggs,the falling substrate,the development period and different sources,and are analyzed and verified by the mixed orthogonal test method of various factors,Further explore the external conditions required to ensure the smooth hatching of drifting fish eggs;Third,as an organism,the physical and chemical properties of fish eggs will be different in the growth process,so relevant tests are carried out.The main findings of this thesis are as follows:(1)With a density of 1.002 g/cm~3,the suspension velocity of the simulated fish eggs under different riverbed sediments with low flow velocity is:the suspension velocity on the smooth glass surface and dense turf bed is 0.20 m/s,and the suspension velocity on the pebble bed is 0.25 m/s.Therefore,the velocity value of keeping the floating fish eggs in suspension is related to the bed sediment.(2)The conclusion that the hatching rate is taken as the research objective after the drifting fish eggs are impacted instantaneously under the conditions of different influencing factors is as follows:1)In the sensitivity study of drifting fish eggs with different falling height,it is found that the larger the falling distance is,the faster the falling speed is.For the fish eggs themselves,the higher the impact damage degree of the fish eggs is;2)The order of the impact of the substrate on the damage of fish eggs is rock>Sand>water;3)The drifting eggs in cleavage stage are more sensitive to instantaneous impact than those in other developmental stages;4)Fish eggs in the farm are more likely to be aborted than natural fish eggs in the Yangtze River after being impacted instantaneously.Similar studies should consider the differences in the sources of fish eggs;5)The results of mixed orthogonal test showed that the fish eggs in the cleavage stage had the highest abortion rate when the velocity was>4.4 m/s.(3)The three test results of drifting fish eggs are as follows:the egg membrane pressure limit of drifting fish eggs is:organogenesis stage(0.503N)<cleavage stage(0.625N)<the early neurula stage(0.737N);Grass carp eggs contain 16 water-soluble amino acids,the composition and types of which do not change throughout development,and the amino acid content shows a trend of"low-high-low".