Robertson. — Hatching Fry in Gravel 147 



Having demonstrated, to my own satisfaction, that there was 

 room for great improvement, I have since then experimented 

 in various ways to ascertain the good features of both methods, 

 with the view of combining them. 



Nature is prodigal and only the fittest survive, and this fitness 

 is the only redeeming feature of natural incubation. The produc- 

 tion of a greater number of fry from a given number of eggs, and 

 the greater protection afforded these fry up to the time of libera- 

 tion, are the strong points in favor of the hatcheries. 



While it cannot be denied that the eggs, as laid by the female 

 fish over an extended period of time, are more susceptible to virile 

 impregnation, which never can be equalled by human agency, still 

 it is doubtful whether the present methods of taking the eggs 

 from the fish, when ninety-five per cent or over are fertilized, will 

 ever be improved on and need not be discussed here. From this 

 stage on, however, the divergence in procedure has great effect 

 and the object of this paper is to point out the shortcomings and 

 merits of both systems as they appear to me. 



WATER CIRCULATION IN THE GRAVEL. 



Spawning salmon seek out beds where seepage occurs and 

 ignore seemingly suitable spots where this condition is lacking, 

 and experiments in connection with this prove that eggs will not 

 survive under the water without circulation. 



I made four tubes of basket wire twelve inches long and one inch 

 in diameter, filled them with eyed eggs, and buried them under one 

 foot of water and one foot of gravel, with water running over them. 

 After a lapse of four days I dug one up and found the eggs in an 

 advanced state of suffocation, which, though not enough to kill, 

 was sufficient to seriously impair the strength of the resulting 

 fry. Each succeeding day I dug up another with increasing bad 

 results, and that on the seventh day was ninety per cent dead. 

 A tube of eggs, buried similarly, fifty feet away where the fish did 

 spawn, hatched successfully. I also filled several glass jars six 

 inches high with eggs, placing same under running water in a 

 trough, and found that they died from the bottom up at the rate 

 of approximately an inch per day, and eggs buried in gravel in a 

 dish one inch deep, placed similarly, died in a week. This may 



