both spring and fall and to spawn throughout 

 the overlapping spawning periods. The status 

 of the spring run in the mainstem is thus 

 speculative. Suffice it to state that spring-run 

 Chinook salmon have not been noted to have 

 been abundant in mainstem Sacramento River 

 during the summer holding period of recent 

 years. Small runs of spring-run fish still as- 

 cend such tributaries as Mill and Deer Creeks, 

 however. 



TIMING OF DOWN-MIGRATION 



The downstream migration of young winter- 

 run Chinook salmon has not been intentionally 



studied. Netting operations conducted under the 

 author's direction on the Sacramento River at 

 Balls Ferry in November and December 1951 

 provided suggestive evidence. Among 3,048 

 young Chinook salmon taken during about 45 

 nights of fyke-net fishing, 25 fish ranged in 

 fork length from 58 to 90 mm., averaging 68.1 

 mm. Of the other 3,023 young chinooks, 3,011 

 were 41 mm. or shorter (table 4) and are 

 considered to have been spring-run and fall- 

 run fry. 



The 58-90-mm. group fits expectations for 

 winter- run fish based on growth of the other 

 races. At the time of capture, these 25 fish 



Table 4. — Downstream migrant chinook salmon caught at Balls Ferry, 1951-1952 



The numbers of fish in these rows include measured fish only; total numbers including un- 

 measured fish were as follows: Feb 29-Mar 9, 3,654; Mar 10-19, 2,517^ Mar 20-29, 2,315. 



Distribution by sizes not available; the numbers shown by 10-day periods are total numbers. 

 The total for the March 30-April 8 period includes the 73 fish described in footnote 3. 



' Record shows 73 fish in the range 49 to 120 mm. were taken; detailed distribution is not 

 ivailable. 



* Distribution by sizes not available; the average size for the 30-day period was 52.4 mm. 

 vhich may be contrasted with the 40.9-mm. average size of the 30-day period preceeding it. 



