SEAWARD MIGRATION OF CHINOOK SALMON. 



49 



This is shown by the close correspondence in estimated size of the yearlings at the time 

 of beginning the more rapid growth of the second year. This correspondence also 

 indicates that the yearlings migrating in the spring are a homogeneous lot and that the 

 check preceding the intermediate growth (in Groups i and 2) is the same as that pre- 

 ceding the new growth (in Group 4) ; that is, that this check in both instances is in reality 

 the winter band. (See discussion on p. 57.) The mode at 100 mm. undoubtedly repre- 

 sents, in the fall migrants, the size at the time of entering the estuary. It is possible 

 that these differences in the estimated size at which the intermediate growth begins may 

 be of value in determining, from the adult scales, the time at which migration took place. 



June July Aug. Sept. Oct. Nov. Dec. Jan. Feb, Mch, Apr. Mqu June 

 ^r^- Yeor It ngs. 



Graph 2. — Estimated length at time of beginning intermediate growth (groups i, 2, and 

 3) and new growth (group 4). Figures at left of graph indicate length of fish in mm.; a» 

 group i; 6, group 2; c. group 3; d, group 4; «, creek at Seufert, Oreg.; /, McKenzie River; 

 and solid line, growth curve for group 1 (from fig. i). 



The rate of growth of the migrating fry in the Sacramento River is given in Table 47 

 and is shown in graph 3. 



Table 47. — Migrating Fry from Sacramento River. 



Date. 



Mar. 5. . 

 Mar. 8.. 

 Apr. 3.. 

 Apr. 9 . . 

 Apr. 13  



Apr. 19 



Apr. 29 



May 8 and 9. . 

 May 9 



Locality. 



Brookdale 



Sisson 



do 



Walnut Grove 



Sacramento River 30 miles above 

 Sacramento. 



Cache Slough 



Prospect Slough 



Butte Slough 



Pond near Butte Slough 



May IS 



May j6 



May 27 



May 38 



June 3 



June 5 and 6. . 



Junes 



June 24 to 36. . 



June 30 



July 9 



Locality. 



Shag Slough 



Hass Slough 



Sausalito 



Prospect slough 



Elkhom 



Woods Break 



Pond near Butte Slough 



Tisdale wier 



Ponds near Knights Landing 

 Pond near Butte Slough 



Length. 



Mm. 



77.0 



7S-a 

 81.0 

 68.0 

 76.8 

 7I-0 

 95-6 

 ;8.8 

 X07.0 

 9a- J 



