Fi(.L];l lb. — ltc;\(jl\iii„ ^LiLL'U 111 wuLlt sui)i)l\ Hume diverts fish and debri.s baeli tu 

 stream at Little White Salmon Hatchery of the Fish and Wildlife Service. 



]Mpe or from a head trough or flume, 

 lu the latter case, adjustable open- 

 ings or spigots control the flow of 

 water into each pond or trough. 

 The manner of introduction of the 

 water determines the extent of 

 increase of bound oxygen. 



If circular ponds or other types 

 of j)onds in which the water is re- 

 circulated are in use, it is necessary 

 to have enough force or head behind 

 the entering water to circulate the 

 pond water properly. Here, for best 

 results, the water is introduced from 

 a pipe. 



Water may be used more than 

 once, that is, it may be passed from 

 one pond or trough into a second 

 pond or trough and thence into 

 others. There should be sufficient 

 fall of the water from the foot of 

 one pond into the upper end of the 

 next pond to assure adequate dis- 



solved oxygen. One serious diffi- 

 culty when passing the same water 

 through a series of ponds or troughs 

 is the possible spread of disease 

 throughout the series, whereas 

 l^onds supplied with individual wa- 

 ter would limit the disease to the 

 single pond except where the source 

 of water for the entire hatchery is 

 atfected, or tools and equipment are 

 contaminated. There apparently 

 are no advantages to reusing water 

 \7hen an adequate quantity is avail- 

 able. 



Experience has shown the neces- 

 sity of selecting a water supply suit- 

 able for the propagation of salmon 

 a] id locating the hatchery at that 

 point. The disadvantages of many 

 such locations as to isolation are tol- 

 erable, but an inadequate or unsuit- 

 able water supply will prevent suc- 

 cessful production of fish. 



41 



