MANUAL OP FISH-CULTURE. 21 



the tray at intervals, care being taken not to raise tliem out of the 

 water, as at this tender age a sliglit pressure against the wire of the 

 tray will often produce fatal injuries. On this account too much caution 

 can not be exercised in regard to handling them out of water during 

 the first stages of the yolk-sac period, for the injuries can not be seen 

 at first, and often the death of the fry is the first warning that they 

 have been injured. 



After the eggs are all hatched and the young fish are safely out of 

 the trays and in the bottom of the troughs their dangers are few and 

 they require comparatively little care. Almost the only thing to be 

 guarded against now is suflbcation. Even where there is an abun- 

 dance of water and room, with a good circulation, they often crowd 

 together in heaps or dig down under one another until some of them die 

 from want of running water which is not an inch away from them. The 

 best remedy in such a case is to thin them out. 



Eight thousand gallons of water an hour is suflQcient for ten lines of 

 troughs 64 feet in length, containing altogether a little over 1,000,000 

 young salmons in the yolk-sac stage. This gives in round numbers 

 800 gallons of water to each 100,000 fry every hour, or 1C§ gallons per 

 minute, which is a safe minimum. 



When the yolk-sac has become nearly absorbed the fish rise from the 

 bottom of the trough, where they have previously remained, and hold 

 themselves up in the water. It is now almost time to begin to feed 

 them, and they have become comparatively hardy and require very 

 little care. 



Close attention is required again, however, as soon as they commence 

 to feed. They will show when they are ready to feed by darting to one 

 side or the other when small i^articles of food are dropped in the water 

 and floated past them. From this time, for several weeks, the necessity 

 for care and vigilance never ceases. 



The young fish should, for the first few weeks, be fed regularly and 

 as often as six times a day, and the earlier in the day the feeding begins 

 and the later it continues at night the better. Two hours after feeding 

 they will be found to be ravenously hungry, and they grow much faster 

 for frequent feeding and get that growth in their infancy which is 

 indisi)ensable to their ultimately attaining the largest possible size. If 

 they are not fed very often they will bite at one another's fins and so 

 cause more or less mortality among themselves. 



ARTIFICIAL FOOD. 



The best food for salmon fry is some kind of meat, finely pulverized. 

 Boiled liver is especially good for this x)urpose, partly because it is 

 inexpensive and easily obtainable, and also because it can be separated 

 into very fine particles. Eaw liver is also an excellent food for fry, 

 and may be reduced into as fine particles as the cooked liver by grind- 

 ing or chopx^ing and then properly straining it through a fine-mesh 



