Figure 1. — Map of lower Columbia River watershed, showing locations of the three National Fish Hatcheries from 

 which study materials were obtained. 



Theoretically speaking, these two groups of 

 fish should have differences in the growth pat- 

 tern of scales, because at the time of release 

 the fry have not started to grow scales, where- 

 as the fingerlings have already grown scales 

 with circuli. The nuclear area (the central 

 portion of the scale) , or at least the initial part 

 of it, of adult scales originating from these two 

 groups of fish must have then grown under 

 different conditions: that from the fry group 

 in river water under lower but variable tem- 

 perature '■ and feeding conditions, and that from 

 the fingerling group in hatchery water with 

 higher and nearly constant temperature ' and 

 ample food. It may be expected then that scales 



Water temperatures of Columbia River at Bonneville Dam in 

 February were 2.8-4.4 T. (1957); 6. 1-8. ST. (19.">8); 3.9-.i.0<>C. 

 (1959). U.S. Army Corp.s of Kngineers. Annual Fish Passape 

 Reports. 



7 Water temperature in Spring Creek Hatchery is about 7.8='C. 

 year-round. 



from fish released as fry should have more 

 closely spaced circuli in the nuclear zone than 

 those released as fingerlings. Further, because 

 the fry were released 3 months before the 

 fingerlings, they should reach the ocean earlier 

 and consequently may have a different pattern 

 of ocean growth than have the fingerlings. 



Practically speaking, if the origin of release 

 — whether fry or fingerling — of returning 

 adults can be identified through .scale charac- 

 ters, then the two methods of release can be 

 evaluated without having to mark young fish. 

 Junge and Phinney (1963) indicate that fish 

 released as fingerlings have a much greater 

 survival rate than have fish released as fry. 

 Therefore, the elimination of mai-king would 

 not only save the costs of marking but also 

 eliminate any possible harm that marking may 

 cause the fi.sh. 



168 



U.S. FISH AND WILDLIFE SERVICE 



