Studies on the Improvement of Artificial Propagation in Trout Culture-II

It is very difficult to extrude the eggs from the ripe female without breaking some of them during the artificial fertilization of the trout cultured. It is known by the culturist that the broken eggs in any amount will seriously interfere with fertilization. To prevent it the following method was devised ; the eggs are extruded on the net receiver and washed by the isotonic salt solution from the shower bath (disolved NaCl 55.05g., KCl 1.97g. and CaCl2•2H2O 3.14g. in 7.5l. water). The eggs are poured into the pan which contained a small quantity of isotonic salt solution and fertilized in the same manner as the usual dry method. We designate it “Egg washing method” for convenience. The authors studied the interference of the broken eggs in the fertilization of rainbow trout eggs and compared the number of eyed eggs obtained between the dry method and the egg washing method. The results obtained are as follows: 1) When more than 25 broken eggs were contained in 100 cc. coelomic fluid, all the sperm coagulated and did not move. 2) No eyed eggs were obtained when the broken eggs were present at the rate of 3% in the normal stripped eggs. In order to obtain above 80% of eyed eggs, the number of broken eggs should be less than about 0.15% in the normal eggs (Fig. 1 and Table 1). 3) The egg washing method is more useful than the dry method in the fertilization of trout eggs when broken eggs are present among the stripped eggs (Tables 2 and 3).