Studies On Age And Growth Characteristics And Reproductive Biology Of Brachymystax Lenok Tsinlingensis

Brachymystax lenok tsinlingensis is a endemic fish and distributed in the provincesof Gansu and Shaanxi Weihe River basin of the Yellow River. The study on the ovarydevelopment and correlative coefficients could provide the basal data for breeding andproduction of Brachymystax lenok tsinlingensis.Using anatomical, histological me-thods, this article studied the ovary of annual change in the ovary of mature Brachy-mystax lenok tsinlingensis,divided stages of ovary development,divided phases of theoocytes.At the same time,recorded data,such as ovary weight,liver weight,empty bodyweight,the size of eggs and so on.This article studied the relation between the ovarydevelopment and correlative coefficients which included fullness,fecundity,LSI,GSIand so on.The main findings are as follows:1.Vertebra and dorsal fin could be used for aging the Brachymystax lenok tsinlin-gensis efficiently.Aging results of vertebra corresponded with that of dorsal fin in86.36%(95:110);Aging results of vertebra corresponded with that of scale in72.73%(80:110);Aging results of scale corresponded with that of dorsal fin in79.1%(87:110).2.Body length (L) and weight (W) of the regression equation:W=2×10-5L1.7281(R2=0.6586n=110).3. The ovary development of Brachymystax lenok tsinlingensis underwent six con-sequent stages as well as the oocytes consisted of six phases. The ovaries were instageI,while the most oocytes were in phaseI,the nucleus made up the greater part ofthe cell;The oocytes in phaseIIwere basophilic,follicle cell, outer ring and threadinessring appeared at the same time; The ovaries were in stageIII,the oocytes in this stagecould be seen, which had double follicle membranes, cortical alveoli,yolk granulesand zona radiata appeared;The ovary in stageIV,the oocytes in phaseIVwere graduallyfull of yolk granules;The ovary in stageV,the oocytes in phaseVwere divorced fromfollicle membranes, and got into abdominal cavity.The ovary in stageVI,the oocytes inphaseVIwere degraded from phaseVI.After spawning,the ovaries transferred gradual-ly from stageVIto stageII.4.The ovary appeared stage I only once all their lives, the ovary of mature Brachy-mystax lenok tsinlingensis was from stageIIto stageVI during a year. The oocytes con- sisted of six phases, too.In every stage of ovary we could almost see the remains ofoocytes.5.The concentrated spawning time of mature Brachymystax lenok tsinlingensis wasfrom April to May of following year.The breeding cycle of Brachymystax lenok tsin-lingensis was one year and the spawning type was single spawning.The absolute fe-cundity, the diameter of egg increased with advancing age before aging.6.Before the oocytes of Brachymystax lenok tsinlingensis developed greatly, LSIdecreased or couldn’t increased significantly, and their fullness increased a little.When the oocytes developed greatly, GSI increased rapidly, liver weight decreasedgreatly and LSI decreased. The body weight decreased a little or increased slowly, andtheir fullness decreased. After spawning, GSI decreased rapidly.