Robertson. — Hatching Fry in Gravel 155 



The water at the rate of about one gallon per cubic foot per 

 minute is then turned on, and thereafter no attention other than 

 seeing the water is kept running is necessary. The eggs need not 

 be actually in the water until the filling is completed, but this 

 should be done as expeditiously as possible. To the uninitiated 

 this may appear rough treatment for fragile fish eggs, but they may 

 rest assured that no harm will ensue if the eggs are soft. To 

 attempt it with hardened eggs is disastrous, but eyed eggs may be 

 safely buried, and as an expedient this may be done with eggs 

 eyed in the troughs and then transported and buried in suitable 

 places. 



In 1915 I had one container in operation. In 1916 seventy, 

 and in 1917 ninety of ten different types, with a combined capacity 

 of over two million eggs. Fifty of these are at Cultus Lake and 

 were filled with sockeye eggs, all hatched successfully with the 

 exception of two which were later found to have running pitch 

 seams in the wood. This distressed the fry and they emerged with 

 the sac on. The gravel in all these boxes with the exception of 

 the two mentioned was found to be clean and free from dead 

 eggs or fry when they were emptied. 



In the course of my duties I visited this station in the day 

 time once a week, and was struck by the fact that no fry were to 

 be seen emerging. I mentioned this to the man in charge and he 

 laughed and said: "If you were here after dark with a lantern 

 you would find the top a squirming mass of fry. " This peculiarity 

 was later corroborated at Harrison Lake and indicates that fry 

 planting should be done at night. 



If the water in one of these boxes stops running, the fry will 

 attempt to emerge, but if handicapped by too much sac they are 

 unable to do so; on the other hand, if not distressed, they will 

 descend as far into the gravel as they possibly can. I filled a jar 

 half full of gravel and placed a quantity of eggs on top and when 

 they hatched they all went down into the gravel. 



I built a trough twelve inches square and twelve feet long, 

 with single riffles two feet apart extending alternately tw d inches 

 from the top and bottom, and filled it with gravel and eggs its 

 entire length, afterwards nailing a cover on. When the fry 

 ceased coming out I emptied the trough and in it found the large 

 fry mentioned previously, all the others were gone, some of them 



