10 e Each year during the summer months j, water temperatures in the 

 section of Deer Creek below the mouth of the canyon become lethal to 

 salmor.o The onset of these high water temperatures is one of the 

 factors which stop the upstream movement of spring-run salmon and cause 

 a loss of fish» From 19h5 through 19^7^ lethal water temperatures 

 killed at least 86ii salmon in the lower section of the creek. No lethal 

 temperatures have ever been recorded in Deer Creek above the mouth of 

 the canyon. Water analysis of Deer Creek showed that algal decomposi- 

 tion^ as a result of low water conditions and high temperatures, caused 

 little change in the chemical characteristics of the water. 



llo By the end of May^ nearly all of the flow in Deer Creek is 

 diverted into irrigation ditches. Resultant low flows, together with 

 high water temperatures, force an end to the upstream migration of 

 spring-run salmon„ The presence of sub-standard rotary screens on the 

 ditches causes a large loss of young salmon. The California Division 

 of Fish and Game has planned to screen adequately all ditches and one 

 such screen and by-pass has been completed. 



Low flows, high water temperatures, poorly screened irrigation 

 ditches, and the extreme difficulty salmon have in passing over the 

 Stanford-Vina Irrigation Company Dam during low water periods are the 

 factors xi*ich prevent Deer Creek from expressing its full potential 

 as a salmon producing stream. These conditions were present before 

 salmon were transferred from the Sacramento River, and since these 

 limiting factors have not been corrected, the addition into the stream 

 of salmon similar in species and habits to the native population has 

 resulted in only partial success. 



12 o The progeny of the transplanted salmon are doomed to a gradual 

 or rapid extinction unless the conditions under which both populations 

 are forced to live are changed enough to accommodate them. Improve- 

 ments necessary are (1) development of an irrigation water supply from 

 the Sacramento River for farms in the drainage which would permit the 

 natural flow of Deer Creek to reach the river, and (2) removal of all 

 dams and obstructions now impeding movement of fish upstream and down- 

 stream. 



15 



