fish, we know that "I" marks an annulus and 

 "C" is merely a check. An incidental check (i) 

 is also present between annuli I and II. 



Two scales of adults that came from Septem- 

 ber release are shown in figures 10 and 11. In 

 figure 10, the marine growth of the first year 

 (C to I) is much reduced as compared with the 

 scale of May or July release origin (figs. 7 and 

 9). Consequently, the annulus (I) is getting 

 closer to the check (C), and the entire ocean 

 nucleus becomes much smaller in size. Because 

 of this, it is easy to determine that the check 

 (C) here is not an annulus. Further reduction 

 in the first year's marine growth is seen in the 

 second example of a September release (fig. 

 11). Here the entire nuclear zone assumes the 

 appearance of a stream nucleus. Indeed, it is 

 questionable whether there is any amount of 

 true marine growth inside the first annulus (I). 



A scale of the October release origin (fig. 12) 

 shows the same characteristics, i.e., a much 

 reduced zone between "C" and "I," and a nu- 

 clear zone that assumes the look of a stream 

 nucleus. At least, as far as age determination 

 is concerned, because the total age of this fish 

 is known to be III, it is certain that "I" is the 

 first and only annulus up to that point, much 

 as "I" in a typical stream nucleus such as that 



Figure 12. — A scale of adult chinook salmon that was 

 released as a fingerlinp in October at the Little 

 White Salmon Hatchery (October 1957 release, 1960 

 return). 



of a February release origin (fig. 8). 



From the above series of examples, it is evi- 

 dent that when the young chinook salmon were 

 released as hatch-of-the-year from May through 

 July, they entered the ocean during the grow- 

 ing season of the first year after some sojourn 

 in the river. As a result, there was a large 

 number of wide mai'ine circuli outside the cen- 

 tral zone of narrow fresh-water circuli, result- 

 ing in a large ocean nucleus. As the release 

 date became later and later in the year (Sep- 

 tember and October), however, the chinook sal- 

 mon would miss more and more of the current 

 season's marine growth, and the result was a 

 nuclear type similar in appearance to a stream 

 nucleus. Finally, when the young chinook sal- 

 mon were reared in fresh water over winter 

 and were not released until February of the 

 second year, the nuclear zone was composed 

 solely of fresh-water growth, and any marine 

 growth belonged to the following year. For all 

 practical purposes, scales from September and 

 October releases should be treated as stream 

 nucleus type, for there is no way of knowing 

 that "I" is not a stream annulus without the 

 knowledge of release date. 



Because the fresh-water growth part in an 

 ocean nucleus may not be distinguishable from 

 that of a stream nucleus, we extended our study 

 into the marine growth of the first and second 

 years of ocean life to find diff'erences between 

 these two types. In this study, 72 returns from 

 May and July releases were treated as one 

 group representing the ocean nucleus type, and 

 85 returns from October and February releases 

 were treated as another group representing 

 the stream nucleus type. 



The method consists of first locating the ap- 

 parent first marine annulus, i.e., a band of nar- 

 row circuli after a zone of wide circuli. This 

 is "I" in figures 7 and 9 and "11" in figures 8, 

 11, and 12. Then, from the midpoint of this 

 annulus band 20 circuli were counted out- 

 ward toward the edge of the scale along an 

 antero-lateral radius, and the total distance of 

 these 20 circuli was measured and repi'esented 

 by "A." This represents the major part of the 

 second year growth in ocean for both gi-oups 

 of scales. Similarly, 20 circuli were counted in- 

 ward toward the focus and the total distance 



176 



U.S. FISH AND WILDLIFE SERVICE 



