Figure 25. — Salmon trapinng and spawning installation by tlie Fish and Wildlife 

 Service on Wind River, Wasli. Adult salmon enter the enclosure through a small 

 opening in the far rack and are seined from the area. 



ciete apron with permanently fixed 

 pipe-rack supports to replace the 

 tripods. At the conclusion of the 

 spawning period, the racks and the 

 plank walkway across the top are 

 removed and the individual pipe 

 supports, attached by swivel joints 

 at each end, are lowered to the apron 

 surface. For the next spawning pe- 

 riod these are caught with a hook 

 and raised to a vertical position, and 

 the walkway and rack sections are 

 placed. This is purely a rack to stop 

 salmon from further ascent of the 

 river and to divert them into pre- 

 pared holding ponds. 



Another type of diversion struc- 

 ture is that placed permanently in 



Battle Creek, tributary to the Sacra- 

 mento River, to divert adult salmon 

 into the holding ponds of the Cole- 

 man station of the Fish and Wild- 

 life Service. (See fig. 24.) This 

 structure is a low concrete dam with 

 a downstream sloping surface and 

 apron over which the water pours in 

 a sheet and in which salmon cannot 

 secure a "foothold" to attempt a 

 jump. During the salmon runs the 

 fish are diverted to a fish ladder 

 leading to large holding ponds. 

 Tliroughout the rest of the year, a 

 fish ladder in the dam itself is open 

 to permit ascent of trout and some 

 salmon to the stream above. 



The type of rack installation for 



50 



