Figure 13. — Saliuon eggs in basket raised 



eggs several inches into water, with 

 the result that infertile or undevel- 

 oped eggs turn white. These eggs, 

 which would eventually become 

 dead tissue and encourage fungus 

 growth, are removed. 



Shocked eggs are replaced on the 

 stacked trays in the water or, if they 

 were in baskets, they may now (or 

 later) be placed on trays, to re- 

 main there until hatching is com- 

 plete and the fry have absorbed 

 most of the yolk sac. The young 

 fish are then placed directly in the 

 troughs, where they are fed finely 

 ground meats. In some salmon 

 hatcheries the eggs are permitted 

 to hatch in the baskets, and the fry 

 drop through the wire mesh to the 

 trough bottom. 



Dead eggs provide the tissue for 

 the growth of fungus that, if not 

 controlled or removed, will spread 

 over and smother surrounding eggs. 

 In view of the delicacy of the eggs 

 during the green stage, it is not de- 

 sirable to attempt to remove the 

 dead eggs because adjacent eggs 

 might be injured. It is possible to 

 prevent or inhibit growth of fungus 

 by routine chemical treatments of 

 the eggs, and during the green stage 

 such treatments are a weekly rou- 

 tine at many hatcheries. Burrows 

 (1949) describes this treatment. 



Silt carried in the water supply 

 can also coat and smother eggs. 

 For this reason and others a clean 

 water supply for the hatchery is 

 desirable. Silt can be removed by 

 passing the water through a filter 



29 



