AETIFICIAL PROPAGATION OF PACIFIC SALMONS. 23 



In a temperature <if 50° F. the eggs will hatch iu 50 days. Every additional 

 degree of warmth lessens the incubation period by 5 days, and every degree 

 lower than 50 prolongs it 5 days. 



Salmon eggs are very hardy during the first few days, and while 

 in this condition they are thoroughly gone over for the removal of 

 the dead ones. At some stations it is customary after doing this to 

 cover the eggs and leave them undisturbed until the spinal column 

 is well formed, when the delicate stage has passed. This is not ab- 

 solutely necessary, however, where skilled operators are employed. 

 Men experienced in the work can handle the eggs throughout the en- 

 tire period of incubation, and this is the most efficient method to pur- 

 sue. When the number of unimpregnated eggs is great enough to 

 warrant, they may be most advantageously removed by means of a 

 salt solution, which should be applied only after the spinal column 

 is well formed. 



By means of this solution, which should consist of one part salt 

 to nine parts of water, one is able to distinguish dead or unfertilized 

 eggs at an early stage of development. The solution is held in a 

 water-tight box or trough of 1-inch lumber, 40 inches long, 18 inches 

 wide, and 12 inches deep. Inside of it is a second box of one-half 

 inch luml^r 3 inches less in width, 3 inches deeper, and provided 

 with handles and a screen bottom. The dead eggs arc removed with 

 a net or scoop made of basket wire. The trough or outer box is filled 

 to within a few inches of the top with water, and salt is added grad- 

 ually and dissolved until the proper density is attained, this being 

 determined by testing a few good and bad eggs in a small portion 

 of the solution each tlpie salt is added. This has been demonstrated 

 to be a more satisfactory method than weighing or measuring, as salt 

 readily absorbs moisture and varies in purity. 



The box with the screen bottom is placed in the solution, wedged 

 down, and a full basket of from 35,000 to 60,000 eggs poured into it. 

 In less than one minute the good eggs will settle to the bottom, and 

 the bad ones can be removed with the wire scoop. The inner box 

 can then be lifted out and the good eggs returned to the basket and 

 to fresh water, the whole process not recjuiring over three minutes. 

 One solution can 1)6 used over and over again by adding sufficient salt 

 to maintain a uniform density. 



The box or trough was adopted because of convenience in handling 

 and because it furnished the necessary amount of surface, a very 

 important feature to consider, as the l)ad eggs, if crowded, would 

 cause the good ones to float by mingling! with them. Quite an ex- 

 tensive use of this methwl of cleaning the eggs has shown no delete- 

 rious results, and where there are over a thousand dead eggs in the 

 basket at the time the empties are turned, the use of the solution will 

 effect a saving of labor. 



PACKING SALMON EGGS FOR SHIPMENT. 



Cases made of 1-inch lumber and of suitable size for packing on 

 horses or mules are used for moving eyed salmon eggs over rough 

 mountain trails from the collecting fields. The bottom of the case 

 is lined with a thick layer of moss and covered with a piece of nios- 

 fjuito netting. On this a layer of eggs is spread and covered with 

 netting. Successive layers of moss, netting, and eggs are thus ar- 

 ranged up to the middle line of the case, where a firm wooden parti- 



3.528fj°— 21 11 



