THE USE OF SALT IN SEPARATING UN- 

 FERTILIZED FROM EYED EGGS 



By G. H. Thomson, 

 Estes Park, Colo. 



The use of salt for the separation of dead eggs has 

 been tried successfully in the Government salmon hatch- 

 eries on the Pacific coast, but I have never heard of this 

 method being applied to the eggs of the Brook Trout. 

 Any method that will avoid the tedious picking out of in- 

 dividual eggs, which is the usual way of getting rid of 

 them, is desirable to save labor and time. The results of 

 my experiments with the eggs of the trout may therefore 

 be of interest to fish culturists. 



During the last winter the hatchery was filled with 

 brook trout eggs, and when these reached the stage when 

 the embryos began to show and the eggs could be handled 

 without danger, I began these experiments. When the 

 dead eggs have reached a certain stage and with the salt 

 solution at the proper density, the separation becomes a 

 very simple matter. As the living eggs settle to the bot- 

 tom while the white eggs remain at the top, the latter 

 can be removed in a dipnet by the hundreds instead of 

 one at a time. The live eggs may then be returned to 

 their trays without injury. 



The white eggs cannot be separated by this method 

 when they begin to turn, for then they have nearly the 

 same specific gravity as the live eggs, but if they are 

 left for three or four days, according to the temperature 

 of the water, they will float readily. 



With the aid of a hydrometer I found 36 degrees to be 

 about the right density for the salt solution and then by 

 making a preliminary test of a few eggs the water could 

 quickly be brought to the proper density for use. If the 

 salt solution is too dense all the eggs will float, but if the 

 density is too low they will all settle to the bottom. 



