Robertson. — Hatching Fry in Gravel 153 



HATCHING FRY IN GRAVEL IN CONTAINERS. 



Having thus demonstrated to the best of my ability that the 

 predominating features of natural reproduction are the production 

 of strong fry and lack of protection, while the reverse obtains in 

 the hatchery method, I now proceed to show how these defects 

 may be overcome. 



In a general way, what I advocate is to take the eggs in the 

 customary way and place them in their soft state in a container 

 where no movement can take place, where they are in complete 

 darkness, and subject to a direct flow of water which is under 

 control and not of a fluctuating surface nature. 



I have been compelled for lack of room in the hatchery to bury 

 eggs in streams and beaches, but several years ago came to the 

 conclusion that it was impracticable and not as good as the 

 fish could do it themselves. Owing to their buoyant nature it is 

 next to impossible to bury eggs under water, and when it was done 

 it did not eliminate any of the faults of natural spawning with 

 perhaps the exception of overseeding. 



I then turned my attention to burying in whitefish jars, 

 gasoline cans and boxes, and found after trying ten different 

 forms of containers that the one I built first, a cut of which is 

 appended, was the best of all. In the whitefish jar, where the 

 water is conducted to the bottom through a tube and rises up 

 through the mass of eggs, the principle of direct circulation is 

 clearly illustrated, and all the other containers are merely modifica- 

 tions of this principle. 



Gasoline cans, with a tube connected to a distributing board 

 are practically the same thing. The water, however, may just 

 as well be used going down as coming up and the wooden con- 

 tainers embody this feature. The use of whitefish jars is only 

 recommended for experimental purposes as they allow a clear view 

 of what is transpiring, but they are costly, easily broken and no 

 better in operation than boxes made of common one inch lumber 

 and lacquered. 



If spring water is used danger from freezing is obviated and the 

 boxes need not be in a building. They should be set up where 

 the overflow spills into a creek or pond, which should purposely 

 be left in its rough state to provide hiding places for the fry, 

 or brush and rock added if cover is lacking. 



