54 



BULLETIN OF THE BUREAU OF FISHERIES. 



which have begun such growth, this would seem to indicate that the later migrants 

 reach actually a greater size before migrating than do the earlier migrants. It is possi- 

 ble, however, that the scales are larger proportionately in the later migrants, the fish 

 themselves being the same size, or even smaller. In such a large river as the Columbia, 

 where the young migrants are coming from numerous tributaries, such generalizations 

 require careful confirmation. 



The author has been unable to see any systematic arrangement in the occurrence 

 of the primary check. The cause of the formation of such a check has been traced in 

 the collection from Seufert; but it is not to be inferred that the change from the hatchery 

 environment to one approximating normal, wild conditions is the only cause behind the 

 formation of such a check. Other somewhat similar envirormiental changes early in 

 the life of the fish would undoubtedly result in a similar check. 



In Table 49 are presented in percentages the data regarding the tj^e of marginal 

 rings found on the scales during successive months on the Columbia River. During the 

 early months the marginal rings of the fry are always of the summer type [type (i) in 

 the table]; that is, are not conspicuously narrowed. In August is encountered the first 

 development of narrow, winter rings [type (2)], and from this time on imtil April vary- 

 mg proportions of the specimens have marginal rings of this type. After the time when 

 the marginal winter rings begin to be a feature of the scale growth it may be expected 

 that the intermediate band, when formed, will be preceded, in some instances, at least, 

 by a distinct band of narrower rings. After the winter bands begin to appear there is 

 a constantly decreasing percentage of specimens whose scales show marginal rings be- 

 longing to the growth of the first summer in fresh water. 



Table 49. — Percentage of Fish Whose Scales Show Marginal Rings of (i) Summer Type not 

 Associated with Intermediate or New Growth, (2) Winter Type, (3) Summer Rings of Nbw 

 OR Intermediate Growth. 



a Seufert. 



6 Little \yTute Salmon River. 



c "Warrendale. _ 

 d McKenzie River. 



e Clackamas hatchery. 



With the exception of the collection from Clackamas hatchery none of the fish taken 

 after November shows marginal rings belonging to the first summer's growth. Such 

 changes as these, combined with the development of an intermediate band, will result 



