HATCHING APPARATUS. 6 1 



brook. To prepare the gravel for use, you should 

 have two screens, one to sift out the sand, and another 

 to hold the coarse gravel. The residue which remains 

 in the first and goes through the second screen is 

 what you want for the hatching troughs. 



Having obtained the right size of gravel, the next 

 thing is to wash it. This should be thoroughly done. 

 Then you can boil it, if you wish, to kill the insect 

 larvse in it ; and I would advise you to do this by all 

 means, for the larvae in unboiled gravel often produce 

 insects that are very destructive to the eggs and young 

 fish. It is not absolutely necessary to use gravel in 

 charcoal troughs, as the eggs will hatch safely on the 

 charcoal bottom. Twenty thousand salmon-eggs w^ere 

 placed directly on the bottom of the charred troughs, 

 at the writer's establishment on the Mirimichi River, 

 by way of experiment, and they did as well as the 

 others hatched on gravel. A thin layer of gravel, 

 however, is recommended. The gravel, if used, should 

 be evenly placed in the troughs to the depth of about 

 half an inch. According to the old method of hatching 

 on wood in its natural condition, the gravel was placed 

 an inch and a half deep, to prevent the fungus from 

 growing up through it ; but in charcoal troughs, where 

 there is no fungus, half an inch in depth, and even 

 less, is sufficient. Be careful to level it off evenly, 

 and leave no holes or depressions, or the eggs will 

 surely collect in them deeper than they ought to. 



There is always so much use for gravel about trout- 

 breeding works, that it is a good plan to save all kinds, 

 and what has been used once, and not washed, put 



