222 BULLETIN OF THE BUREAU OF FISHERIES 



Table 1. — Chinook-salmon yearlings marked at Bonneville hatchery March 2 and 11, 1916 — Contd. 



I In this and subsequent tables the averages given at the toot of the columns of frequencies represent the average length in 

 millimeters. 



Note.— Groups in parentheses each contain 1 individual whose scales show no second year's growth. 



A slight narrowing of the rings about midway in the first year's growth is ap- 

 parent in some of the scales. (See fig. 6.) This narrowing or check is comparable 

 to that which the senior author (Rich, 1920) observed in the scales of many seaward 

 migrants and has termed "primary check. " In this connection the term "primary " 

 was intended to be descriptive from the standpoint of time, but to some readers it 

 has given the impression of first in the order of importance. In view of this con- 

 fusion of meaning it seems advisable to discontinue its use and to introduce the more 

 general term "incidental check, " to be applied to all checks other than annuli, which 

 represent a winter in the life of the fish. The significance of this check, formed 

 during the fii-st year's residence in fresh water, is not always clear, but it has been 

 shown in some cases to have resulted from some abrupt change in the environmental 

 conditions. (Rich, 1920.) 



Only one adult fish has been recovered that unquestionablj- shows the mark used 

 in this experiment. This fish was a male weighing 48 pounds (21.8 kilograms) and 

 was taken in one of the wheels near The Dalles, Oreg., on May 4, 1920. The adipose 

 fin was entirely lacking and the right opercle showed unmistakably the scar resulting 

 from the clipping. Figure 4 shows the approximate extent of the scar. One other 

 specimen was obtained that probably is of this series. This doubtful specimen was 

 taken on May 28, 1920, near Warrendale, Oreg., and was sent by the finder to the 

 Oregon fish commission. The data, including scars, were forwarded to the writers, 

 together with data from several other marked fish. En route the package was 

 damaged badly, and from this specimen only the scar of the adipose fin remained. 

 It is not Ivnown whether the gill cover was included in the original shipment or not. 



The scales of these fish are similar and show that they were in their sixth year. 

 The central portions of the scales, the "nuclei" (representing the growth of the first 

 year), are typical of the stream type described by Gilbert (1913) and correspond 



