

Figure 3. — A scale of Spring Creek Hatchery chinook 

 salmon that was released as marked fry. Note the 

 relatively wider spacing between circuli in the first 

 year of marineg rowth. 



Figure 4. — A scale of Spring Creek Hatchery chinook 

 salmon that was released as a marked fingerling. 

 Note the relatively narrower spacing between circuli 

 in the first year of marineg rowth. 



study first-year marine growth, because these 

 10 circuli always represent the major but not 

 the entire part of the first summer growth in 

 the ocean. Using the 10 circuli enables us to 

 have more consistent measurements than we 

 would obtain by measuring the entire first sum- 

 mer growth, because we cannot delimit exactly 

 the first and last circuli of summer growth. 

 Circuli 11 through 15 were purposely skipped, 

 for they may represent some transitional 

 growth and therefore are quite variable as a 

 group. 



In reference to scale graphs, the initial 10 cir- 

 culi are represented by the first two and a half 

 units on the abscissa; and circuli 16 to 25, by 

 units 4 to 6. In essence, the measuring method 

 enables us to check on the graphing method, for 

 we can tabulate the data and subject the results 

 to statistical tests. 



The results of the measurements and statis- 

 tical tests are shown in table 1. In all the tests 

 between the paired .sample means, we first 

 tested for the variances (s-) and then applied 

 the appropriate f-test. 



In the comparisons of the fii\st 5 circuli and 

 of the first 10 circuli, the variances of the 

 paired samples are significantly difi'erent, and 

 f-test shows that the sample means are not sig- 

 nificantly different. This is to say that although 

 circulus spacing in the initial 5 or 10 circuli is 

 more variable in the group released as fry 

 (larger variance) than in the group released as 

 fingerlings, the average values do not differ 

 significantly between these two groups. The 

 latter point confirms the results of the scale 

 graph method 



In the comparison of the 10 circuli counted 

 from 16th to 25th circulus, the variances are 

 not significantly different, and t-test shows that 

 the sample mean of "A" (fry relea.ses) is sig- 

 nificantly larger than that of "B" (fingerling 

 releases). This is to say that the groups re- 

 leased as fry and as fingerlings have a similar 

 amount of variation in circulus spacing for 

 circuli 16 to 25, but that the average spacing 

 of circuli in the group released as fry is larger 

 than that in the group released as fingerlings. 

 The latter point also confirms the results of the 

 scale graph method. 



170 



U.S. FISH AND WILDLIFE SERVICE 



