THIRTY-EIGHTH BIENNIAL REPORT ' ' 39 



In 1943 no one was available to make a count on the Tuolumne River. 

 An estimate of the number of fish that ran up the San Joaquin River and 

 spawned below Friant was again made. Approximately 7,000 fish were 

 counted on the spawning- beds in this area. From similar counts made 

 in other streams where check counts at weirs were available indicate that 

 this must be considered a minimum estimate of the numbers of fish present 

 in the upjier San Joaquin. 



A trap was installed on the American River below the spawning 

 grounds and the run in that stream was estimated by tagging fish at this 

 trap and later comparing proportions of tagged and untagged fish on the 

 spawning beds. Heavy spring and fall freshets preclude the possibility 

 of obtaining complete counts of migrants remaining below Folsom Dam. 

 The 1943 run was estimated to total 7,000 fish by this method. 



Fyke Net Work 



Fyke nets were operated to determine the numbers of salmon fr}^ lost 

 in various diversion canals. Nets were also run in the rivers near the 

 intake of those canals tested to check the time and size of the downstream 

 migration. 



From May 1st to June 9, 1943, nets were operated in the Sacramento 

 River (near Chico), the Glenn-Colusa Canal, the Feather River (near 

 Oroville), the Sutter-Butte Canal, and the Great Western Canal. The 

 movement of 3'oung salmon was evidently early, and most of them had 

 moved out of the rivers by the time the ditches began taking water. 

 Results obtained can not therefore be considered significant. 



In 1944 the work was started earlier with an earlier start of the 

 irrigation season. On the Feather River (near GridlejO nets were 

 operated from January 23d to May 31st. The heaviest downstream 

 movement of young salmon occurred during March and April. The 

 Sutter-Butte Canal opened early in April and moderate numbers of 

 salmon were taken in the canal between mid- April and the end of May. 

 The Great Western Canal opened in mid-April and took very few salmon. 

 These catches were again affected by variations in stream flow and the 

 difficulty of operating fyke nets in irrigation canals. They must be 

 repeated to determine the significance of the results obtained. Both of 

 these canals divert water from the Feather River. 



On the San Joaquin River near Mendota the fyke nets were operated 

 from January 19tli to July 16th. Four large canals and one small one 

 leave the river at this point. At least one canal diverts water at all 

 times. By March 7th of 1944 all canals Avere operating. 



The migration of young salmon down the San Joaquin was heavj' 

 from January 27th through ^larch, and reached its peak on February 

 24th. The canals diverting water at Mendota did no appreciable damage 

 until February 11th, but from that time on the loss of young salmon was 

 heavy. On February 18th one fyke net took 3,000 young salmon from 

 one canal. 



Shasta Salvage Operations 



In November of 1942 the fall run of adult salmon was blocked for the 

 first time at Shasta Dam when construction reached the point where it 

 was no longer possible to take the fish over. From that time on the 

 salvage program of the U. S. Bureau of Reclamation was in full operation. 



