The Standing Crop And Growth Characteristics Of Larvae In Early Life History Stages Of Gprzewalskii Przewalskii In Shaliu River

G.przewalksii is endemic to the qinghai lake,the core position of qinghai lake ecosystem,only distributed in qinghai lake and the surrounding water tributaries,low fertility,bad living environment,slow growth.And early due to overfishing,spawning young field the destruction of the influence of factors such as climate,G.przewalksii resources a serious recession,even dried up.Discharge work in recent years,with the proliferation and migration route of repair,G.przewalksii resources gradually recover,but has yet to be restored to the resources of historic period as an adromous fish,Shaliu River is an important spawning channel of G.przewalksii,and the second largest of the five freshwater tributaries of Qinghai Lake.It is very important to supplement the resources of G.przewalksii.This study investigated the fish in early life stages of G.przewalksii in Shaliu River from 2019 to 2020,and analyzed the spatial and temporal distribution characteristics,the influence of environmental factors on the fish in early life stages,and the resource supplement amount of G.przewalksii in Shaliu River.We also studied the otolith microstructure in 2020,observed the otolith morphological characteristics,confirmed the otolith deposition law,studied the change law of the ring spacing,and the otolith and larva growth characteristics.The main research results are as follows:1.A total of 3831 eggs and 7097 larvae of G.przewalksii were collected from Qinghai Lake from 2019 to 2020.The survey found that the parent fish started to migrate from the end of May,the eggs appeared in early June,reached the peak in July,then gradually decreased,and basically disappeared in the middle of August.The number of larvae increased in a fluctuating way from early July,reached a peak in August,and disappeared in early September.According to the estimation,the fish egg runoff and larva runoff in 2019 are 25.58×10~6and 62.00×10~6respectively.In 2020,the runoff of fish eggs and larvae will be 11.93×10~6and 30.99×10~6respectively,and the runoff of eggs and larvae will decrease greatly.The abundance of eggs decreased from the estuary to the river mouth,but the abundance of eggs in section 2 was higher because of more spawning grounds.The horizontal distribution of the cross section is usually the center of<on the right bank<the left bank,but it will change under the influence of hydrodynamics.Test showed that there were significant differences in egg abundance between day and night in 2019(P<0.05).The abundance of larvae was significantly different between day and night(P<0.01),and the drift peak of larvae was concentrated at night.There was a significant positive correlation between egg abundance and flow velocity(P<0.05),larvae abundance was significantly positive correlation with flow velocity(P<0.01),and daily runoff rate was significantly positive correlation(P<0.01).2.The study of 300 otoliths dissected by random selection of 150 fish samples from Saliu River in 2020 found that the micro otoliths of 20 days old were elliptical,and with the increase of day age,the external characteristics were not obvious.The sagittal otoliths of 17-27 days old fish changed from near ellipse to mussel shape,and the morphology changed obviously and the characteristics were distinct;and the morphology changed obviously and the characteristics were distinct.Among the 150lapilli,34.00%could be clearly identified and 5.33%could not be clearly identified.Among the 150 sagitta,10.00%could be clearly identified and 19.33%could not be clearly identified.It is found that the deposition of otolith diurnal cycle is daily.The average age of wild larva was 19.47±3.58 days based on the number of rings N+1.The larva was mainly distributed between 15 and 22 days of age,and the larva was the largest at 20 days of age.It was inferred that the 10-day-old wild larva had formed a swim bladder and could leave the spawning ground voluntarily,the 20-day-old wild larva had certain swimming ability and could search for food independently,and the34-day-old wild larva had returned to the lake to fatten up.The incubation period of wild larva in Shaliu River in 2020 was calculated from June 5 to August 14 by combining the age and sampling date,and the incubation time was more than two months,but mainly concentrated in the middle of July and early August,so the reproduction time of parent fish could be determined more accurately.3.2-8 rounds of impaction Shaliu River wild grain spacing increases gradually,different temperature gradient farmed larvae of 2-5 rounds of grain spacing increases gradually,after all to 24 rounds of grain spacing showed a trend of decrease,but with the rise of temperature gradient,the space becomes larger round lines,followed by to10?7.87±0.89 um<15?8.59±0.72 um<20?9.49±0.82 um,round grain spacing decrease trend gradually narrowed,analysis shows that 2-5 rounds as endogenous feeding period,5-8 rounds for mixed nutrition period,after the eighth round of exogenous feeding period,The deposition of otolith is greatly influenced by temperature and nutrition.Regression analysis found that the G.przewalksii carp fry has significant linear correlation with age,otolith diameter has significant linear correlation,impaction and farmed the fit of the larvae were higher than wild series,growth speed impaction as temperatures rise,the total length of the average growth rate of impaction gradient temperature were 0.128 mm/d and 0.167 mm,0.175 mm/d/d,Shaliu River wild an average growth rate of 0.155 mm/d impaction,faster than the low temperature impaction farmed,slow in high temperature artificial breeding,impaction and silver fish otolith diameter and length of 15?relevance is strongest,fitting degree is highest.