The variations in abundance and composition of juvenile populations 

 are paralleled by a variety of flow patterns. The most significant of 

 these are the patterns of inflow and outflow that prevail during the 

 months of greatest population density. Inflow is reduced during these 

 months and consequently outflow to the sea is similarly reduced , But 

 the outflow pumped to the Delta-Mendota Canal reaches peak levels in 

 June, July, and August. Outflow to the Dumps sometimes exceeds the 

 amount of water flowing from the Delta to the sea. This would have been 

 the case in July of 19^9 with project operation modified for increased 

 storage at Folsom Reservoir. In that month, the outflow to the sea would 

 have been 3,000 cubic feet per second while the pump demand would have 

 been 3,0u0 cubic feet per second. Generally, pump demand for the months 

 under consideration in 19U8 and 19U9 would have ranged from one-third to 

 over one-half that of the volume of flow passing to the sea. The effect 

 of flow on fish in these instances needs no further elaboration. 



As previously stated, the population of juvenile fish in the Delta 

 from February to June is composed entirely of seaward migrant king 

 salmon. It has also been pointed out that these fish enter the Delta in 

 peak numbers during periods of heavy run-off. Thus, inflow to the Delta 

 is at peak levels during most of the period that these salmon are in the 

 area. Similarly, outflow to the sea is at peak levels while pump demand 

 is low. This situation appears to be favorable to the bulk of king 

 salmon seaward migrants from Sacramento River. 



Seaward migrant king salmon of San Joaquin River origin must face 

 an entirely different set of circumstances, most of which are detrimental 

 with the project in operation. They arrive in the Delta six weeks to two 

 months later than the Sacramento River fish; their point of entry into 

 the Delta is in close proximity to the Tracy Pumping Plant; their avenues 

 of migration through the Delta converge on the intake to the pump channel; 

 and up to 70 percent of the entire San Joaquin River flow is destined for 

 the pumps during their period of migration. 



It is evident, therefore, that king salmon migrants of Sacramento 

 River origin are more secure than those of San Joaquin River origin. 

 Nevertheless, migrants from both sources that are in the central Delta 

 area in June and July will be influenced by the current patterns pre- 

 vailing at that time. Striped bass and shad juveniles in the central 

 delta will be subject to the same influences. 



FISH PROTECTION 



Preceding sections of this report have shown that important segments 

 of the immature populations of king salmon, striped bass, and shad enroute 

 through and within the Sacramento-San Joaquin Delta will be endangered by 

 the conditions created by the Tracy Pumping Plant and the Delta Cross- 

 Channel. The information gathered is sufficient to support recommendation 



39 



