| Due to the characteristics of slow growth and late sexual maturity of Schizothorax waltoni,as well as the overfishing and invasion of alien species,its population resources have plummeted.In order to better protect and exploit the resources of the population of Schizothorax waltoni.Firstly,the serum levels of sex hormones and gonadal tissue development were measured each month;The data of age,body length,total length,absolute fecundity and pearl Star development of the breeding population and the non-breeding population were compared;Different combinations of three kinds of propagation drugs were designed to injected on Schizothorax waltoni;The reproductive performance of reproductive parental fish induced by artificial propagation was compared with that without artificial propagation.The mortality rate at different periods of embryo under continuous vibration was calculated to determine the sensitive period,and compared the hatching effect before the sensitive period and after the sensitive period under flowing water;In the end,the saprolegniasis of the postpartum parent fish was isolated and identified,and its life cycle and growth at different temperatures,salinity and pH values were observed.The minimum inhibitory concentration of 8 Chinese herbal medicines and 3 fishery drugs were tested in vitro.The final test results are as follows:1.The annual changes of sex hormones and gonadal tissuesThe content of estradiol in females of Schizothorax waltoni was highest in March,and the lowest value in September;the highest value of male testosterone in March,the lowest in July.Within a year,the GSI of female and male showed only one peak in April.There will be 5periods in the ovarian and testis period within a reproductive cycle.2.Artificial breeding technology of split-bellied fish in LhasaIn the female brood stock samples of Schizothorax waltoni,the minimum age is 7 and the maximum age is 31.Among them,the age group was mainly from 11 to 19 years,with 117 tails,accounting for 68.02%of the total sample,The absolute fecundity of females increases with age,body length and body weight.Among the male,the youngest sample was 6 years old and the oldest was 29 years old,and the number of samples was distributed evenly in all age groups.There were no significant differences in the age,weight,body length,and full-length data between that could not participate in reproduction and that could participate in reproduction.When use（LHRH-A2+HCG+DOM）three kinds of propagation drugs which the dosage is 10ug/kg+1500IU/kg+10 mg/kg to induce spawning of Schizothorax waltoni,The effect time was 40 h,which was significantly lower than that of other treatment groups（p<0.05）,while the oxytocin rate was 80%,the fertilization rate was 83.78%,and the incubation rate was 75.05%,that was significantly higher than that of other treatment groups（p<0.05）.the effect time is shorter than other groups,and the fertility rate,hatching rate and fertilization rate are higher than other groups.Although the number of eggs per unit body weight and eggs per unit body length of females Schizothorax waltoni who lay eggs without propagation drugs injection was lower than that females who lay eggs per unit body length,their fertilization rate and hatching rate were higher than those of the latter.3.The sensitive period of embryo under continuous vibration,and hatching method improvementUnder the 12℃,vibration frequency of 100 r/min,the death of embryo Schizothorax waltoni was mainly concentrated before the sarcomere period,that is,within 96h after fertilization,accounting for about 1/3 of the total incubation time（277 h）;the mortality rate after the sarcomere period was extremely low.The highest mortality rate of embryo in the middle of gastrula stage is66.11±7.88%,which is significantly higher than other test groups（p<0.05）,the cause of death of the embryo is rupture of the yolk sac.The hatching time of the test group was 24h later than that of the control group.The survival rate of Schizothorax waltoni embryo hatching in cylindrical incubator before sarcoid stage was significantly lower than that in the incubation plate（p<0.05）.After the sarcomere stage,there was no significant difference between the hatching rate and the hatching rate of the larva in the cylindrical incubator and that in the incubation plate（p>0.05）.4.preliminary study on Saprolegniasis of Schizothorax waltoni after spawnedA fungal strain named LY01 was isolated from the spawned Schizothorax waltoni.Combined ITS gene sequencing and morphological characteristics,the strain LY01 was identified as Saprolegnia australis.After culturing the strain LY01 at 25℃for 24 h,the hyphae can be observed,and a large number of spores can be seen in the hyphae at 48 h;new sporangia appear on the hyphae at 72 h,and some sporangia have been excreted as zoospores;after 120 h,due to the evaporation of water,the PDA medium began to dry and agglomerate,and the sexual structure of a spherical ovipositor appeared on the mycelium.At the same time,some of the zoospores had been discharged from mycelium.The optimal temperature range for the LY01 strain is 25～30℃;the LY01 strain is very sensitive to salinity.When the salinity is>1%,the hyphae length is significantly inhibited;When pH>9,the hyphae length was significantly inhibited.The minimum inhibitory concentration of strain LY01 against ethanol extracts of Melia toosendan Sieb was 99 mg/L;the minimum inhibitory concentration of ethanol extracts of pseudolarix kaempferi and gallnut was 296 mg/L;The minimum inhibitory concentration of ethanol extract of Notopterygium incisum Ting and Syringa oblata were 889 mg/L;the minimum inhibitory concentration of Sophora flavescens,chrysanthemum and Belamcanda chinensis was2667 mg/L,2667 mg/L and 8000 mg/L,respectively.5.ConclusionThe suitable artificial breeding season of Schizothorax waltoni is from early April to late may.The female parent fish should be more than 11 years old,and the pearl star of male parent fish should be better developed.The best effect was achieved when the dose of propagation drugs was LHRH-A2:10 ug/kg+HCG:1500 IU/kg+DOM:10 mg/kg.The embryo were incubated for 96hours under the condition of microfluidus and then incubated in a fluidus incubator barrel.The Melia toosendan Sieb,pseudolarix kaempferi and gallnut had a good prospect in preventing and controlling the occurrence of spawned fish. |
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