Research On The Key Technology Of Artificial Propagation And Seed Breeding Of Polyscaly Shovel Jaws

Varicorhinus macrolepis belong to Cyprinidae,Barbinae and Varicorhinus,also known as stone mouth fish,Onychostoma macrolepis,money fish and red scaly fish.They mainly inhabit in the mountains of western Hubei province,Qinba mountain areas and Taihang Mountains.They are also listed as provincial protected animals in Shandong,Gansu and other places with natural distribution in Taishan areas in Shandong Province.In Chongqing,Varicorhinus macrolepis are distributed in the Daning River of Wushan County.Before,Varicorhinus macrolepis were mainly wild,and there were no artificial breeding.Due to the effects of water pollution,climate change,artificial overfishing and other factors,wild resources have sharply decreased.At present,Varicorhinus macrolepis have been listed as provincial protected animals in Shandong,Shanxi,Gansu and other places.In order to protect and multiply the resources of Varicorhinus macrolepis,it is imperative to develop artificial breeding and improve pond cultivation techniques.The materials for experiments in this paper are all taken from the Daning River Basin in Wushan County,Chongqing City,and the experiments are conducted at the local Jinwawa Andrias davidianus Culture Co.,Ltd.In this paper,taking Varicorhinus macrolepis broodstock in the Daning River Basin of Wushan County,Chongqing City as the research object,artificial breeding technology,microscopic technology and others are adopted to study Varicorhinus macrolepis broodstock,embryos and so on.And then the effects on artificial reproduction of Varicorhinus macrolepis are explained under different conditions related to nature spawning,different induced drugs and different induced doses.Artificial Breeding of Varicorhinus macrolepisUnder the condition of water temperature of 17 ?,Varicorhinus macrolepis will have labor induction comparison experiments with different doses of artificial induction and the oxytocin used is as the following: Carp pituitary gland(PG),luteinizing hormone-releasing hormone analogue(LRH-A?)and chorionic gonadotropin(HCG).The experiment includes three parts: single injection group,double injection group.On March 31,2019,the first group of Varicorhinus macrolepis have natural spawning and as for the second group,double injections are adopted to induce laying.And on April 2,Varicorhinus macrolepis also use double injections pattern for artificial induction.And on April1,April 4,April 12 and April 27,single injection will be respectivelly used to achieve artificial induction.According tothe comparision,the effects of using double infection pattern are better(the first injection: LRH-A? 4?g/kg+PG 20mg/kg;the second infection: LRH-A?10?g/kg+HCG 1000IU/kg+PG 8mg/kg).In this artificial reproduction experiment,624 females and 1,384 males are used.322 females are successfully induced.The fertility rate is 51.60%,the fertilization rate is 72.00%,the hatching rate is 61.33%,and the number of emergence is 243840.Embryo Development of Varicorhinus macrolepisThe mature fertilized eggs of Varicorhinus macrolepis are spherical and belong to the sinking egg,which are sticky,generally golden or white,relatively transparent,full and round,and the diameter of the egg after water expansion is(2.87 � 0.36).On the contrary,the unfertilized eggs are grayish white and opaque.Under the condition of water temperature of 17.2 ? � 0.5 ?,the embryos of Varicorhinus macrolepis hatch out after 147 hours and 30 mins,and are divided into the following 7 stages:Fertilized egg formation period(0-1 h48 min),cleavage period(3 h38 min-7 h38 min),blastocyst stage(9 h32 min-22 h02 min),gastrointestinal embryo stage(33 h15min-45 h19 min),neuroblastogenesis period(50 h24 min-53 h55 min),organ formation and the membrane break period(56 h-147 h30 min).Early Larvae Breeding of Varicorhinus macrolepisThe larvae of Varicorhinus macrolepis hatched at the beginning have a total length of(8.86 � 0.52)mm and a weight of(0.00444�0.00014)g.Eye pigment begins to appear at 2 d and gradually deepens.On the 8th day,a chamber of swim bladder appears in the abdominal cavity of the larvae,and the second chamber of swim bladder appears on the 21 st day.Meanwhile,the yolk of the larvae is completely absorbed and completely depends on exogenous nutrition.When the scales begin to appear on the 34 th day,it means that the postlarva stage comes.On the 70 th day,the scales spread all over the body.Their body shape and color then are close to those of adult fish,and they enter the larvae stage.In this experiment,the larvae of Varicorhinus macrolepis are cultivated for 85 days,and a total of 244,000 larvae of Varicorhinus macrolepis are obtained.And the survival rate is more than 60% and the average body length is 40.17 mm.It is in the southwestern region that the cultivation of Varicorhinus macrolepis fries are firstly successfully achieved.Except for the linear growth of body length,body weight and days,the growth of body length,body weight and days was polynomial.Some daily breeding equipment are required for the cultivation,which are easy to operate,andguarantee the survival rate of the larvae.Thus,it is a cultivating model of Varicorhinus macrolepis larvae which is worthy of extensive promotion and application.