escapement counted from the towers 

 erected in the stream at Igiugig. Finally, 

 the total percentages of the two age 

 groups for the entire season were calcu- 

 lated (table 5). 



In spawning ground sanriples, percent- 

 ages of the two age groups were calculated 

 for each locality. These were weighted 

 according to estimated population size 

 for each locality, and the totals for all 

 spawning ground samples were obtained. 

 These are compared in table 5 with those 

 from Kvichak River samples. 



were properly weighted, there should be 

 no difference in the freshwater age 

 composition between the two samples. 

 The discrepancy revealed in 1956 and 

 1957 samples is obviously due to sampling 

 difficulties, which may have occurred at 

 either or both places. Let us examine 

 each sampling closely. 



Kvichak River Sampling 



Theoretically, several factors here may 

 cause nonrepresentative sampling of the 

 population. 



In 1956 and 1957, there was a marked 

 difference in age composition between 

 samples from the Kvichak River and from 

 the spawning grounds, but in 1958, the 

 age composition was practically identical. 

 The differences in the first 2 years are 

 consistent in that there is a higher propor- 

 tion of I. fish in Kvichak River samples 

 than in spawning ground samples. In other 

 words, proportionately more 2. fish were 

 found on the spawning grounds than were 

 first sampled in the Kvichak River. This 

 is especially pronounced in 1956. 



DISCUSSION OF RESULTS 



Scale samples from both the Kvichak 

 River and the spawning grounds naturally 

 canne from the same population. If they 

 were representative of each place and 



1. The sampling period: The run lasts 

 about a month. Our sampling covered only 

 about 3 weeks. The early and tail ends of 

 the run were not sampled. However, most 

 of the migration took place during the 3- 

 week sampling period; in both 1956 and 

 1957, more than 95 percent of the run 

 occurred within this period (table 1). 

 This coverage can certainly be considered 

 adequate. 



2. The weighting: The percentages of 

 the two age groups as determined from 

 each day's samples were weighted ac- 

 cording to the number of fish counted 

 from towers in the Kvichak River. Tower 

 enumeration of the adult run has been 

 proved an accurate method of assessing 

 the number of fish by this Institute's 

 work on the Wood River and by the Fish 

 and Wildlife Service's work on the Egegik 



Table 5. — Freshwater age composition between Kvichak River and spawning ground samples 



of adult red salmon, 1956-58 



Year 



Locality 



Age groups, in percent 



1. 



1956 



Kvichak River 

 Spawning grounds 



83.6 

 53.6 



16.^ 



46. A 



1957 



Kvichak River 

 Spawning grounds 



57.4 

 44.1 



42.6 

 55.9 



1958 



Kvichak River 

 Spawning grounds 



11.6 

 11.2 



