ABUNDANCE AND AGE OF KVICHAK KIVRK KED SALMON SMOLTS 



313 



results are shown as length-frequency curves in 

 figure 14. The similarity between the two nets 

 in sizes of fish caught indicate that nets fished 

 in the area bordered by the index and B4 sites 

 should sample reliably. The length-frequency 

 curves presented in figure 7 also show similarity 

 in the sizes of fish taken by two nets fished side 

 by side. 



Smolt Sizes at Distant Net Sites 



Smolt samples taken in 1957 and 1958 during 

 the simultaneous fishing of two nets, one 2 

 miles upstream from the other (fig. 15; appen- 

 dix tables 10, 11, 15, and 16), show similarity 

 of length frequencies and age composition and 

 indicate that the nets were intercepting the 

 same smolt population. 



N'erification of Fresh-Water Age 



It is reasonable to assume that if the age 

 composition of the smolts is reliable, then the 

 fresh-water age composition of the adults that 

 return after two or three winters in the ocean 

 should be similar to that of the smolts. This 

 comparison is made on the assumption that the 

 marine survival rate is relatively constant for 

 one-winter and two-winter fish. Only the adult 

 samples taken at the Igiugig tower sites were 

 used in this comparison, because samples from 

 the commercial catch include fish bound for 

 adjacent rivers in the Naknek and Egegik dis- 

 tricts as well as the Kvichak River. The per- 



Index Site 

 Site B4 



80 90 100 110 120 



FORK LENGTH IN MILLIMETERS 



130 



Figure 14. — Leng:th frequencies of smolts captured at 

 the index site and site B, between 2200 and 0100 hours, 

 June 7 and 8, 1955. (Frequencies are smoothed by 

 moving averages of threes.) 



80 90 100 110 120 130 



Index site 

 Site C 



80 90 100 no 120 130 

 FORK LENGTH IN MILLIMETERS 



Figure 15. — Comparative smolt length frequencies, in- 

 de.x site and site C, 1957 and 1958. (Each daily sample 

 was weighted by the magnitude of the smolt catch for 

 that day. Frequency for each year is smoothed by 

 moving averages of threes.) 



centages of the two age groups of smolts in the 

 1955, 1956, and 1957 migrations, and the per- 

 centages of the various age groups of adults 

 that returned from these smolt migrations ai'e 

 shown in table 12. This good relationship of 

 smolt age to adult fresh-water age indicates the 

 method for smolt age determination is valid. 



Table 12. — Agr groups (in percent) of smolts i)i migra- 

 tions of 1955, 195ti, and 1957 and of adults 

 yetnriiing 2 and 3 years later 



1 Age groups of smolts refer to number of winters the smolts spent 

 in fresh water. 



- Adult age determinations from escapement scale samples ana- 

 lyzed by Dr. Koo. Arabic figure refers to year in which fish returned 

 as adults, and subscript figure refers to year in which fish migrated 

 tu sea. 



