AMATEUE FISH CULTUEE 



about six weeks, and before the yolk-sac is com- 

 pletely absorbed. The rearing boxes should be 

 kept partly covered, and the alevins will crowd 

 into a pack in the darker parts at the bottom 

 of the hatching tray. 



The shells of the ova must be removed from 

 the hatching trays. As they are lighter than 

 the alevins, the current will generally carry 

 them to the lower end of the tray, whence they 

 may be removed with a piece of gauze spread 

 on a wire ring, or by raising and lowering the 

 tray gently in the water in alternately slanting 

 directions. 



The alevin stage is the stage in which the 

 least mortality should be expected, and the little 

 fish give but little trouble. There are, however, 

 several diseases besides fungus (of which I have 

 spoken already when dealing with the ova) from 

 which the alevins may suffer. 



I was, I believe, the first to describe (in the 

 "Eainbow Trout") a peculiar disease from which 

 alevins suffered. When hatched out and kept in 

 water containing a very large quantity of air in 

 solution, I found that sometimes alevins developed 

 an air bubble in the yolk-sac. On developing 

 this bubble they are unable to stay at the bottom 



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