Limited studies in the San Joaquin Delta during 19u7 yielded in- 

 complete information as to the movements of the seaward migrants from 

 the' San Joaquin River drainage. The total number of young salmon re- 

 covered was small. However, the results showed that the most signifi- 

 cant downstream movement occurred in May. 



In 19l*8 seaward migration of king salmon from the Sacramento drain- 

 age was influenced by drought conditions prevailing in the area from 

 mid-January through the middle of March. An initial movement of down- 

 stream migrants to the delta in early January was noted from fyke net 

 results. This influx diminished with the river runoff so that by Jan- 

 uary 23rd. no salmon were observable. Increasing water flows resulting 

 from late March rains flushed the young salmon from the upper streams 

 so that by the end of that month the seasonal peak of abundance was 

 reached. The numbers and monthly percentages of king salmon migrants 

 sampled by fyke net at Isleton during the 19u8 downstream movement are 

 summarized below: 



~19W 



Month 



No. of Salmon 



Percent of Total 



Mean Monthly Runoff c.f.s. 



Studies by Rutter and Hatton of the seaward movement of young salmon 

 were limited to the periphery of the Delta and up-river locations. Knowledge 

 of the salmon dispersal in the Delta was fragmentary, although Hatton did 

 observe salmon movements near Martinez. One of the objectives of the pre- 

 sent investigation was to determine the migratory habits of the salmon 

 within the Delta. To this end tow-netting operations at the twenty-five 

 stations established in the Delta began on April 9, 19u8. 



Delay in the start of tow-netting prevented observation of the 

 initial pattern of dispersion of the young salmon from the Sacramento 

 River into the Delta. A total of 1,19k salmon migrants was captured 

 in towing operations from April 9 to August 3, 19U8, and all individuals 

 were measured. Data collected for each station during the season are 

 given in Appendix Table 5, and are further summarized in Appendix Table 

 1. The catch data for 19U8 are shown graphically in Figure 3, which il- 

 lustrates the distribution of king salmon migrants in the Sacramento- 

 San Joaquin Delta as determined from tow-netting results. 



Although a major segment of the young salmon moved down the Sacra- 

 mento River toward the bay, a significant proportion was diverted via 

 Georgiana Slough into the central San Joaquin Delta. There is evidence 

 of further transfer of migrants by tidal action to the San Joaquin Delta 

 through Three Mile Slough and Sherman Lake. The proportion of salmon 

 migrants is assumed to be in direct relation to the amount of Sacramento 



lU 



