Study On The Effects Of Turbulent Flow On The Incubation Of Hypophthalmichthys Molitrix Eggs

Under natural conditions,the hatching quality of fertilized eggs of drifting fish is of decisive significance to its species reproduction.However,the complex flow patterns and turbulent flow conditions in rivers inevitably lead to differences in embryonic development of drifting fish eggs.This study focuses on the impact of different turbulent flows on the hatching process and outcomes of the representative Hypophthalmichthys molitrix eggs.Firstly,the hatchability,deformity rate and hatching duration of six developmental stages of Hypophthalmichthys molitrix eggs were studied using a vortex oscillator with different vibration intensities and durations.The impact of flow vibration on the hatching of drifting fish eggs was quantified from the perspective of external energy input.Secondly,a circular fish egg incubation tank was designed to investigate the effects of flow velocity and turbulence intensity on the hatching of Hypophthalmichthys molitrix eggs.The developmental status and damage degree of fish eggs at different developmental stages were observed regularly,and the mortality rate,hatching time,hatching rate and deformity rate of the fish larvae were recorded.The main research results are as follows:(1)As the intensity or duration of water disturbance increases,cracks on the surface of fish eggs increase and deepen.The embryonic body inside the eggs during the blastula,gastrula,and neurula stages was stretched,while there was no significant change of the embryonic body during other stages.The hatching rate of Hypophthalmichthys molitrix eggs gradually decreases with the increase of water disturbance intensity or duration,while the deformity rate of larvae gradually increases and the incubation time shortens.Among all stages,the neurula stage was the most sensitive to water disturbance.The shortening of incubation time is probably an environmental induction,which indirectly proves the plasticity and diversity of the hatching mechanism of semi-buoyant fish eggs.In addition,a methodology is proposed to convert water disturbance into energy input into the fish eggs,providing a quantitative approach to study the effect of current stimulation on fish embryo development.(2)Hypophthalmichthys molitrix eggs are more suitable for development in still or slow-flowing waters.The hatching rate of Hypophthalmichthys molitrix eggs first increases and then decreases as flow velocity increases,while the deformity rate gradually increases,reaching the highest hatching rate at an average flow velocity of0.5m/s.The hatching rate of Hypophthalmichthys molitrix eggs gradually decreases with the increase of turbulence intensity,while the deformity rate gradually increases.The hatching rate could be higher under the turbulence intensity of less than0.0968m/s.During the hatching process while drifting,Hypophthalmichthys molitrix eggs primarily die due to embryonic development stagnation during the early stage,and mechanical impacts during the later stage,with the most sensitive developmental stage being the neurula stage.(3)Hypophthalmichthys molitrix eggs that shed their membranes during or after the neurula stage can successfully hatch into larvae,with the hatching rate increasing with the delayed shedding of membranes while the deformity rate decreases.Hypophthalmichthys molitrix eggs shed their membranes before the neurula stage cannot develop into larvae,but the survival time after shedding their membranes increases with the delay of the developmental stage.These results can provide reference and guidance for the study and protection of drift fish egg proliferation.