Figure 20. — Interior view of Quilcene, W;i8ii., Hatchery of the Fish ami Wihllife 

 Service. Double-deep-type troughs contain baslvets of salmon eggs. 



have been tried, but the wood 

 troughs continue predominant, 

 ])rincipally for economy. 



Trays for the incubation of 

 sahnon eggs are of various sizes (for 

 the deep troughs, 14 inches by 16 

 inches) ; most have a wood frame 

 (11/2 inches by % inch) on the bot- 

 tom of which is fastened a screen 

 of suitable mesh. The eggs are 

 phiced on the trays in a single or 

 double layer, and the trays are 

 stacked and placed in the troughs. 

 An arrangement of metal dam 

 boards directs the flow of water up 

 through a stack of trays, back to 

 the bottom of the trough, and up 

 through the next stack of trays. 

 The trays stacked in a deep-type 

 trough have a capacity of about 

 200,000 chinook-salmon eggs, run- 

 ning 50 to 80 eggs per fluid ounce. 



When the young fish are free 

 swimming and capable of taking- 

 food, they are taken from the trays 

 and i^laced directly in the troughs 

 (from which the dam boards have 

 been removed ) . A wire-mesh screen 

 or a perforated plate at the lower 

 end of the trough prevents the es- 

 cape of fish. The water level of the 

 tiough usually is maintained by a 

 standpipe inserted between the 

 screen and the lower end of the 

 trough. The pipe can be removed 

 readily to facilitate cleaning of the 

 trough. 



Water for the trough is intro- 

 duced either from a head trough or 

 by pipe, and the water may be 

 passed from one to another of a 

 series of troughs to conserve water, 

 but with the disadvantages men- 

 tioned previously. Troughs usu- 



43 



