Study On The Ovary Development And Correlative Coefficients Of Rainbow Trout(Oncorhynchus Mykiss)

Oncorhynchus mykiss is an economical cold water fish with high nutritional value. The study on the ovary development and correlative coefficients could provide the basal data for breeding and production of rainbow trout (Oncorhynchus mykiss).Using anatomical, histological methods, this article studied the ovary of 4~33 months old fishes and annual change in the ovary of mature Oncorhynchus mykiss, divided stages of ovary development, divided phases of the oocytes. At the same time, this article recorded data, such as ovary weight, liver weight, empty body weight, the size of eggs and so on. This article studied the relation between the ovary development and correlative coefficients which included fullness, fecundity, LSI, GSI and so on . The main results were as follows:1. The ovary development of 4~33 months old fish underwent six consequent stages as well as the oocytes consisted of six phases. Four months old ovaries were in stageⅠ, while the most oocytes were in phaseⅠ, the nucleus made up the greater part of the cell. Eight to thirteen months old ovaries were in stageⅡ, the oocytes in phaseⅡwere basophilic, follicle cell, outer ring and threadiness ring appeared at the same time. Fifteen to twenty-six months old ovaries were in stageⅢ, the oocytes in this stage could be seen, which had double follicle membranes, cortical alveoli, yolk granules and zona radiata appeared. The ovary in stageⅣwas 28~30 months old, the oocytes in phaseⅣwere gradually full of yolk granules. The ovary in stageⅤwas 31 months old, the oocytes in phaseⅤwere divorced from follicle membranes, and got into abdominal cavity. The ovary in stageⅥwas 31~33 months old, the oocytes in phaseⅥwere degraded from phaseⅥ. After spawning, the ovaries transferred gradually from stageⅥto stageⅡ.2. The ovary appeared stageⅠonly once all their lives, the ovary of mature Oncorhynchus mykiss was from stageⅡto stageⅥduring a year. The oocytes consisted of six phases, too. The oocyte's diameter of mature Oncorhynchus mykiss was longer than its at the first sexual maturity in every phase. And in every stage of ovary we could almost see the remains of oocytes.3. The concentrated spawning time of mature Oncorhynchus mykiss was from October to January of following year, the most was in December. The breeding cycle of Oncorhynchus mykiss was one year and the spawning type was single spawning. The absolute fecundity, the diameter of egg increased with advancing age before aging.4. Before the oocytes of Oncorhynchus mykiss developed greatly, LSI decreased or couldn't increased significantly, and their fullness increased a little. When the oocytes developed greatly, GSI increased rapidly, liver weight decreased greatly and LSI decreased. The body weight decreased a little or increased slowly, and their fullness decreased. After spawning, GSI decreased rapidly.