was measured as "B" (fig. 13), which repre- 

 sents the first year growth in ocean for both 

 groups of scales. Then we computed the ratio 



Figure 13. — The measurement of circulus spacing. 

 Left, Chinook scale with an ocean nucleus; right, 

 Chinook scale with a stream nucleus. 



30 

 20 



10 



30 

 20 

 10 



LITTLE WHITE SALMON RIVER HATCHERY 

 MAY AND JULY RELEASES 



N = 72. x= i,;o 



^ 



-^- 



■ 



-ES- 



LITTLE WHITE SALMON RI\ER HATCHERY 

 OCTOBER AND FEBRUARY RELEASES 



-^ 



I 



i 



N= 85, X=l 22 



f^^ , 



1.0 1.1 1.2 1.3 1.4 1,5 16 1.7 1.8 

 RATIO OF SECOND TO FIRST YEAR OCEAN GROWTH (j) 



of A/B, which is the ratio of second year marine 

 growth to the first year marine growth. 



We found that in the May to July release 

 group, circuli of the second year marine growth 

 (A) were, on the average, nearly 50 percent 

 wider than the first year marine growth (B) ; 

 whereas in the October to February release 

 group, "A" was only 22 percent wider than 

 "B". The frequency distribution of the ratio 

 A/B of these two groups of scales is shown in 

 figure 14. It is obvious that the two groups 

 are distinctly different in the value of A/B, but 

 there is also enough overlap so that not all 

 scales can be identified to their nuclear growth 

 type on this character alone. 



DIFFERENTIATION OF FALL CHINOOK AND 



SPRING CHINOOK SCALES BY 



MARINE GROWTH 



The fall chinook scales normally have a 

 typical ocean nucleus (sub-one age), and the 

 spring chinook scales normally have a typical 

 stream nucleus (sub-two age). The nuclear 

 growth part of these two types of scales cannot 

 always be distinguished. So in order to identify 

 these two groups of fish, we applied the method 

 of comparing first and second year's marine 



15 



I 

 :: 10 



o 5 



z 



60 



40 



20 



FALL CHINOOK FROM SPRING CREEK HATCHERY 



N= SO. X= 142 



-Ea 



i 





f^ 



[ M I 



-PSSJ- 



SPRING CHINOOK FROM CARSON HATCHERY 



N = 109. X= 1.04 



I 



£3- 



0.9 1.0 11 1.2 13 1.4 15 1.6 1.7 1.8 1.9 



Figure 14. — Frequency distribution of the ratio of 

 second to first year marine growth (A/B) of little 

 white salmon Hatchery recaptures of May and July 

 releases, and October and February releases. 



FIGURE IS 



Figure 15. — Frequency distribution of the ratio of 

 second to first year's marine growth (—A/B) of fall 

 chinook and spring chinook. 



SCALES OF CHINOOK SALMON 



177 



