conditions^ it has been determined by the U. So Bureau of Reclamation 

 that the entire discharge of the San Joaquin River would flow into the 

 pumping plant (USER Hydraulic Laboratory Report No, 1U5)<- If the entire 

 flow of the San Joaquin River can be expected to flow into the pumping 

 plant,, it is reasonable to state that all seaward migrating fish from the 

 San Joaquin River will be endangered by the pumping plant operations. 



Striped Bass (Roccus saxatalis ) 



In determining the status of striped bass in the Sacramento-San 

 Joaquin Delta, the Fish and Wildlife Service has been concerned chiefly 

 with the breeding distribution and early life stages of the juvenile 

 bass in Delta waters in relation to the Tracy Pumping Plant and the 

 Delta Cross-Channel. No direct sampling of the adult population was 

 attempted in this study. 



Observations of immature striped bass during the first year and a 

 half, August 20 , 19l;6 through December, 19u7, were dependent on fyke 

 net operations. The results showed trends in the abundance and rate 

 of growth cf the juvenile bass in the areas where the nets were fished. 

 The San Joaquin River fyke net located below Antioch Bridge was fished 

 continuously for three and a fraction years. 



A late start in fyke-net sampling in 19M3 obviated any analysis 

 of trends for that year. In 19u7 the fyke net was fished continuously 

 through the year. The initial appearance of juvenile bass was in the 

 last week of May. The period of peak abundance occurred during June 

 23-27, when 17 bass per hour were taken, averaging 32.8 mm (1.3 inches) 

 in length. During 19U8 and 19U9 the fyke-net sampling continued as a 

 supplement to the tow-net operations. The first significant fyke-net 

 catch in 19U8 was made June 16-30, followed by a period of peak abundance 

 on July 2H> to August U, when 12 .U fish per hour were captured, averaging 

 31. U mm in length (1.2 inches). In 19U9 the initial fyke net catch of 

 juveniles was made June 2=10, with the period of peak abundance occurring 

 from June 29 to July 8 when 2U.2 fish per hour were taken. These fish 

 averaged 32. h mm in length (1.3 inches). Thus 19^9 was the best year of 

 striped bass production in the Delta during the period 19u7 to 19u9° 



The introduction in I9ii8 of tow-net sampling at selected stations 

 located throughout the Delta provided a quantative method of determin- 

 ing abundance and dispersion of striped bass eggs, larvae and post- 

 larval juveniles. 



In 19ii8 sampling for striped bass eggs and larva? was limited to 

 standard surface plankton net hkuls of five and ten minutes duration. 

 Tables 7 and 8 give a summary of the bass eggs and larvae taken in the 

 plankton haul -. The spawning distribution of adult striped bass in 





