786 



BULLETIN OF THE BUREAU OF FISHERIES. 



The fish soon accustomed themselves to the race, and at the spawning time 

 about a dozen pairs of the larger trout conducted their spawning in it. Owing to 

 the aggressive disposition of some of the males, the race proved to be too small 

 for all the fish, and some of them nested in the ponds, as in previous seasons. 



tya/er/ey,^/ 



JTA- f^ ^/r^t^^^y' ^ 



Cross section. 



Longitudinal section. 



Fig. 2. — Spawning race. 



Note. — Screen is used to prevent the clogging of the riffles, but with properly proportioned quantities of gravel and 

 coarse sand the screen may be omitted. The eggs and milt of the fish should sink into the riffles with the liner particles 

 of sand, to prevent fish from devoiu'ing the eggs during the spawning period. 



The race was in the open air, covered at intervals with strips of burlap laid 

 over wire netting to afford shaded portions. The spawners showed no preference 

 as to the shaded or the open spaces, nesting in both. In some instances they 



Fig. 3. — Suggested arrangement of a stream for the control of trout or salmon at the spawning season, and for the col- 

 lection or rearing of the fry after the eggs have been naturally deposited and hatched. Sketch shows side channel, 

 canal or prepared race, with flow of water regulated and controlled by dams, weirs, and gates. Under favoring condi- 

 tions both channels might be available. 



spawned in water too shallow to cover their backs, and in the open sunlight. 

 Wire netting was stretched over the race to protect it from disturbance by birds 

 and domestic animals, but it had no further attention until the fish abandoned 



