6o 



BULLETIN OF THE BUREAU OF FISHERIES. 



Tables 50 and 51 and graph 8 show that, as in the case of the rate of growth, 

 the general features of scale development are not conspicuously different in the Sacra- 

 mento River from those found in the Columbia River. As a result of the earlier 

 begiiming of the growth (noted on p. 50) the scale development also starts earlier. 



So far as can be judged by the available data, none of the fry migrating in the 

 spring will show a distinct narrowing preceding the intermediate growth. Inasmuch as 

 the water of the Sacramento River becomes so warm during the summer that young 

 salmon can not survive in it, it seems probable that the collections studied represent 

 quite completely the migrating fry, and therefore it may be concluded that few, if any, 

 of these will show a band of narrow rings preceding the intermediate band. There is 

 very little evidence to show when the yearlings rnigrate, if at all, or whether there is 

 any migration of fry during the late fall or winter. It would be logical to expect to find 

 that fish older than the fry migrating in their first spring do migrate, and it seems prob- 

 able that many, if not all, of such older migrants would show a band of narrower winter 

 rings preceding the intermediate band. The evidence for this is given in Table 52, in 

 which it is seen that none of the fish taken later than August has scales whose marginal 

 rings belong to the first summer's growth. None of the fry collected in the lower part 

 of the Sacramento shows scales whose marginal rings are of the winter type. There have 

 been entered, therefore, in the following table (52) only the data on the collections from 

 the McCloud River: 



Table 52. — Percentage op Fish from McCloud River Whose Scales Show Marginal Rings of 

 (i) Summer Type Belonging to the First Summer's Growth, (2) Winter Type, (3) Summer 

 Rings of New or Intermediate Growth, Associated with the Second Period of Rapid 

 Growth. 



1909; FRY. 



July 



September 



1911: 



September 



October 



November 



December 



Z912: YEARUNGS, 



January 



February '. 



March 



(3) 



0.0 

 S30 



 7 

 sS. o 

 56.0 



58.0 

 48.0 

 71.0 



If the author's supposition is correct that there is a migration of older fish sharply 

 separated from the spring migration of fry, it would be expected that there would be 

 two distinct types of nuclei found on the scales of the adults — one characteristic of 

 fish which had migrated as fry in the spring and which shows no particular narrowing 

 preceding the intermediate or ocean growth, and the other type showing a narrowing 

 preceding the intermediate or ocean growth representative of fish which had migrated 

 either in the fall as fry or as yearlings in the spring. A more detailed study of the 

 young migrants in the Sacramento, involving collections made throughout the year, 

 would be -necessary to firmly establish this hypothesis. The spring and fall runs of 

 adult fish in the Sacramento River are sharply separated, and a study of the scales of 

 adults belonging to these two runs would seem to offer interesting possibilities. 



