SEAWARD MIGRATION OF CHINOOK SALMON. 



29 



Table 23. — Young Chinooks From Lower Columbia River, Dec. 3 to 8, 1915 — Continued. 



TWENTY-ONE SPECIMENS WITH INTERMEDIATE GROWTH. 



Length. 



Number. 



Scale record. 



Average number of 

 rings — 



To inter- 

 mediate 

 growth. 



Total. 



Average length of 

 anterior radius — 



To inter- 

 mediate 

 growth. 



Total. 



Average 

 estimated 

 length of 

 fish at 

 beginning 

 of inter- 

 mediate 

 growth. 



126 to 130 mm. 

 121 to 125 mm. 

 116 to 120 mm. 

 Ill to IIS mm. 

 106 to no mm. 

 loi to 10s mm. 

 96 to joo mm. , 

 91 to 95 mm. . . 

 86 to 90 mm. . . 

 81 to 8$ mm. . . 

 76 to 80 mm. . . 



Av. 95,1 mm. 



18.0 

 14- 7 

 14- o 

 14- 5 

 18.0 

 14-2 

 13- S 

 13.0 



32- O 



1S.7 

 18.0 



18. s 

 33. o 

 18.3 

 17-5 

 14. o 



58.0 

 43- o 

 43-0 

 36.7 

 33- o 

 36.7 

 39- o 

 33- o 



14. 7 



18.7 



38.6 



68.0 

 58.0 

 53- o 

 50.5 

 48.0 

 46.7 

 44.0 

 38.0 



50.4 



98.0 

 81.3 

 78.0 

 T1 

 73- o 

 68. o 

 63.0 

 68.0 



72.8 



Owing to the unusual severity of the winter of 191 5-1 6, no more collections were 

 made after the one just considered until the following March and April. The fry taken 

 during the spring and early summer have already been considered, and it remains now 

 to discuss the yearlings which were taken during the second year after hatching. 



During the course of the seining on the lower river in March and the early part of 

 April, 1916, a total of 47 yearlings were captured. (See p. 7.) Although these were 

 obtained from several different localities, separate tabulation shows no special difference 

 in the fish from different places, and the entire collection is here tabulated together. 

 There are 26 males in the collection averaging 97.6 mm. in length and 21 females 

 averaging 93.2 mm. The average length of the entire collection is 95.6 mm. Thirteen 

 of the specimens do not show the wider rings at the margins of the scales, but narrow', 

 typically winter rings. The remaining 34 specimens have the wider marginal rings 

 which are characteristic of the young migrating fish. It has been previously indicated 

 that the marginal band of wider rings in these yearlings which were captured in the 

 spring are probably in large measure indicative of the new growth of the second year. 

 The term "intermediate growth " is retained, however, for the reasons given on page 25. 

 The following table (24) presents the data for this collection; 



Table 24. — Chinook Yearlings from Lower Columbia River, Mar. 31 to Apr. 2, igi6. 

 SPECIMENS WITHOUT intermediate growth. 



75412°— 22- 



