From the foregoing it is evident that a clear understanding of the 

 entire problem demands consideration of the sums of the juvenile popu- 

 lations of salmon., striped bass, and shad in relation to the flow patterns 

 that will occur in the Delta when the Tracy Pumping Plant and Delta Cross- 

 Channel are operating. It is also clear that a proper relationship can 

 only be visualized by utilizing information obtained on the fishes in 19U8 

 and 19h9 in conjunction with project operation schedules calculated in 

 accordance with Delta inflows for the years 19^8 and 19^9- These operation 

 schedules were obtained from the U. S. Bureau of Reclamation and concern 

 initial Central Valley Project operation and that project operation as 

 modified by increased storage at Folsom Reservoir now under construction 

 on the American River. They do not, however, show flow conditions that 

 would have prevailed in the Delta in 19U8 and 19^9 with the project in 

 full operation. Under full operation, the Tracy Pumping Plant would 

 deliver a maximum flow of li,600 cubic feet per second to the Delta-Mendota 

 Canal. Data on this operation were not available at the time of prepa- 

 ration of this report and accordingly their inclusion was impossible. 

 However, the relationship of Delta fish populations to flow patterns that 

 would have existed in 19li8 and 19U9 with the project operating at its 

 maximum level is a matter of primary importance. A critical study of 

 Figure 11 should be conditioned by this fact. 



The relationships between fish populations and flow are shown dia- 

 grammatically in Figure 11 for the various months during which juvenile 

 fish were studied in 19l|8 and 19h9^ The data presented and used in the 

 formulation of the various diagrams are presented in Appendix Tables 20, 

 21,23,25,26, and 27. The relative magnitude of the sums of juvenile 

 populations of striped bass, salmon, and shad is illustrated by circles, 

 and is proportional to the area of the circles in each case. The propor- 

 tion of the total population represented by each species in each month is 

 given in percentum. The percent, of abundance of each species is shown 

 by a segment of the circle as well as by a figure within the segment. 

 Water flows into and out of the Delta are designated by single lines or 

 pairs of parallel lines radiating from the circumference at each major 

 point of entry and exit. These points are named, and arrows indicate 

 the direction of flow. Mean monthly flows are given in each case and the 

 distance between parallel lines is drawn to scale according to volume of 

 flow to assist in their comparison. The outflow point at the bases of 

 the circles is designated, Delta-Mendota Demand , and represents outflow to 

 the Tracy Pumping Plant. In each figure, the total volume of water carried 

 from the Delta via this route is shown and the sources and volumes making 

 up this flow are given. 



An examination of the monthly diagrams in Figure 11 clearly shows 

 that juvenile fish are most abundant in Delta waters in the months of 

 June, July, and August. They also show that the population is dominated 

 by striped bass and shad in the months of July and August. Salmon con- 

 stituted only a small fraction of the total in June of 19^9 but were more 

 abundant in that month in 19lj8. They show, too, that seaward migrant 

 salmon made up the entire population of juvenile fish in the Delta in 

 the spring months preceding June. 



38 



