SUMMARY 



1. The U\ S. Fish and Wildlife Service carried on investigations 

 in the Sacramento-San Joaquin Delta from 19^6 to 19h9 in order to deter- 

 mines (1) the magnitude, composition and occurrence of populations of 

 king salmon, striped bass, and shad that occur in or utilize Delta waters j 

 (2) the effects of changes in Delta hydrodynamics on these populations 

 that would result from project operation; (3) the effects of various 

 other environmental factors ; and (h) ways and means of protecting and 

 maintaining these populations if damage to them was indicated. 



2. Young stages of anadromous fishes were found in Delta waters 

 in all months of the year. King salmon were dominant from February 

 through May, with peak numbers occurring in March. Large numbers of 

 salmon remained in the Delta to the middle of July. The juveniles of 

 striped bass and shad were dominant during the period June through 

 September, with peaks of abundance occurring in July and August. The 

 juveniles of all three species were present in quantity during the months 

 of June and July. 



3° In 19U8 and 19h9 striped bass and shad spawned in the Delta from 

 early April to the end of June, with peak activity occurring in the month 

 of May, and with some shad spawning as late as the end of August. Occur- 

 rence and abundance of the larval forms of these species paralleled that 

 of spawning activity. 



lio Eggs, larvae, and juveniles of striped bass and shad were dis- 

 tributed throughout the Delta, with heavy concentrations occurring in the 

 central area, particularly in the channels of the lower Mokelumne River, 

 San Joaquin River between its confluences with Middle River and Seven 

 Mile Slough, and Old and Middle Rivers. King salmon juveniles entered the 

 Delta from Sacramento River through Georgiana Slough, Three Mile Slough, 

 and, by tidal action, up the mouth of San Joaquin River. They distributed 

 themselves throughout the Delta in a manner similar to that noted above 

 for striped bass and shad. Juvenile king salmon entered the Delta from 

 San Joaquin River principally through the channels of Middle River, Old 

 River, and Grant Line Canal, all of which converge on the southwest corner 

 of the Delta. Their dispersal from this point was quite uniform and 

 seemed to follow a definite seaward movement. 



5. It was observed that the early life stages of salmon, striped 

 bass, and shad occurred in abundance in relation to water volume, and it 

 was further observed that populations of fish tended to pile up in large 

 open-water areas most susceptible to tidal action. As a corollary to 

 this principle, evidence was obtained to show that distribution was in 

 proportion to flow, 



60 When the project is in operation, drastic changes in existing 

 Delta flow patterns will occur, particularly during the months of June, 

 July, August, and September, when project demand will be high. Water 



1*5 



