46 



BULLETIN OF THE BUREAU OE FISHERIES. 



One of the most striking features of the growth as shown by this tabulation is the 

 constant difiference in average size maintained in different parts of the stream. 



The smallest fish taken are those comprising group i, from the main river above 

 the estuary. The rate of increase in the size of these fish is quite regular, although 

 there is a period from November until March when the growth is practically negligible. 

 In April and May a second period of rapid growth is apparently started, although more 

 data collected during subsequent months would be necessary to prove this. Since no 

 yearlings are found in the river after June, it is impossible to get this information. 



140 

 130 

 120 



90 

 80 

 •70 

 60 

 50 

 40 

 30 

 20 

 10 



Mch. Apr. Maif June Jul^ /ug. Sept. Oct. Nov. Dec. 



Jan. Feb- Mch. Apr. May Juvt 

 Yegi-ltnga. 



Graph i. — Rate of growth of young diinook salmon from different regions of the Columbia 

 River Basin. Figures at left of graph indicate length of fish in mm. ; solid line, group i ; broken 

 line, group 2; dots and dashes, group 3; dotted line, group 4; a, Columbia River near mouth 

 of Little White Salmon River; h, small creek near Point ElUce; c, lake at Seufert, Oieg.; 

 d. Little WTiite Salmon River; and e, McKenzte River. 



Until after May there is no particular difference in the size of the fry from different 

 portions of the stream. However, in later collections it is seen that those composing 

 group I are smallest, followed, in the order of increasing size, by those of group 2 (from 

 the estuary), group 4 (from the Clackamas River), and group 3 (from under the can- 

 neries at Ilwaco and Astoria). 



The greater size of the fish of group 2 as compared with those of group i is un- 

 doubtedly due to the more rapid rate of growth maintained in the estuary. In the same 

 manner the greater size of the fish taken from under the canneries is due to the more 

 rapid rate of growth of those fish which acquire the habit of feeding on the abundant 

 offal. The fact that fish taken under canneries are so uniformly different from those 

 taken but a short distance away indicates that the young salmon congregate at these 



