Operations in the Sacramento-San Joaquin Delta were accelerated 

 in 19i-i9 when tow-netting began on January 25th. During the period of 

 downstream migration, February 22 to July 22, a total of 3,1*10 salmon 

 were taken in tow-net catches and a random sample of 2,978 individuals 

 were measured for length. Data collected for each station during the 

 season are given in Appendix Table 6 and are further summarized in 

 Appendix Table 2. Distribution of the king salmon migrants in the 

 Delta as determined from the tow-net operations is illustrated graphi- 

 cally in Fig. ho 



The first four weeks of tow-net sampling failed to show the presence 

 of king salmon seaward migrants in the Delta. Initial appearance of 

 Sacramento River salmon migrants was observed in the fifth towing cycle 

 with specimens taken February 23rd. in the lower Mokelumne River, station 

 20, and Georgiana Slough, station 21. The following day, February 2l*th, 

 several salmon migrants were taken in Sacramento River, stations 22, 2k, 

 and 25. 



The appearance of young salmon in the Delta prompted several ex- 

 ploratory tows during the fifth cycle to observe the rate of downstream 

 movement of the Sacramento migrants through the Delta. These explora- 

 tory tows revealed a steady but light migration of young salmon down 

 Sacramento River and the transfer of some migrants to the San Joaquin 

 River through Three Mile Slough. The first evidence of Sacramento 

 River salmon entering San Joaquin River from Georgiana Slough was 

 observed February 28th. at station lit. 



The peak of seaward salmon migration from Sacramento River sources 

 reached the Delta during the sixth towing cycle, March 1-U, 19l;9 (Fig. 

 U). This peak of abundance coincided with an increase in Sacramento River 

 runoff which doubled over the previous week's mean flow of 15,600 second feet, 

 The major portion of the seaward escapement was down Sacramento River with a 

 proportionate diversion down Georgiana Slough. By the end of the sixth cycle 

 some scattering of the young salmon was observed in central Delta waters. 



Although the Sacramento River runoff was increasing, a decline in 

 the number of salmon migrants entering the Delta occurred during the 

 7th. towing cycle, March 8-10, 19^9. The Sacramento River salmon mig- 

 rants were becoming well distributed throughout the central part of the 

 Delta and some seaward movement of these fish was evident down the San 

 Joaquin River. Dispersion of immature Sacramento River salmon toward the 

 southern part of the Delta was noted, with recoveries of individuals 

 from San Joaquin River at station 13, and Old River at station 6. Succeed- 

 ing towing cycles (8 and 9) showed that the major segment of the Sacramento 

 River salmon population had entered the Delta and escaped seaward by the end 

 of March, principally down Sacramento River. A number of the juvenile salmon 

 diverted via Georgiana Slough into the central Delta had penetrated up the 

 San Joaquin Delta as far as the Borden Highway Bridge at Middle River , 

 station 9, and the Santa Fe Railway Bridge at Old River, station 5. 



17 



