KARLUK EIVEE RED-SALMON INVESTIGATION 



57 



Among the adult salmon that return to the Karluk River to spawn there is always 

 found a larger number of females than males. The proportions differ somewhat 

 in different years, partly due to the number of grilse that enter the run. For the 

 grilse, alone, of all the age groups, show a marked preponderance of male fish. In 

 Table 23 the proportions of the sexes are given for different sections of the run of 

 1926. It will be noted that during the second half of June and from the middle 

 of July to the end of August the relative numbers of males and females are virtually 

 identical, varying less than 1 per cent during this most important part of the run. 

 During the earlier part of the run, prior to the middle of June, the males show 

 greater abundance, about equaling the females in number. During the latter part 

 of the run, especially in September, the males show a marked increase, slightly 

 exceeding the females for the average of this period. This reversal near the end 

 of the season is not wholly due to the increase in numbers of grilse running at this 

 time, for if we take into consideration only the 5 3 and the 6 3 groups, we find in them 

 also a slight excess of males. 



Table 23. — Karluk red-salmon run of 1926. Percentages of males and females in samples during 



different portions of run , 



Date 



Males 



Females 



Date 



Males 



Females 



May 24 to June 18 _ 



49.1 

 39.0 

 42.1 

 39.4 

 39.9 



50.9 

 61.0 

 57.9 

 60.6 

 60.1 



Aug. 14 to Aug. 27 



39.8 

 53.1 



60.2 

 46.9 



June 19 to July 3 



Aug. 28 to Sept. 11 



July 6 to July 17 . 



Total 



July 19 to July 29. 



43.0 



57.0 



July 30 to Aug. 12 





In Table 24 we give, for purposes of comparison, the proportions of males and 

 females in the three principal age groups during four recent years. We give also the 

 relative proportions of the males and females in the total samples of all age groups 

 taken during those years. It will be noted that the excess of females is greatest in 

 age group 6 3 for each of the four years presented, a condition that may well stand 

 related to the fact that the 6 3 group has spent one more year at sea than have the 

 other two groups and is thus potentially older. Inasmuch as the males show a 

 constant tendency to mature at an earlier age than do the females, it results that 

 early-maturing age groups very generally show a heavier percentage of males than 

 do the older groups. 



Table 24. — Percentages of males and females in principal age groups in a series of years 



Year 



Sex 



Age groups 



Total 

 samples 



St 



63 



6< 



1922 





48.4 

 51.6 

 46.6 

 53.4 

 43.7 

 56.3 

 43.2 

 56.8 



42.0 

 58.0 

 44.3 

 55.7 

 41.4 

 58.6 

 34.0 

 66.0 



57.3 

 42.7 

 46.8 

 53.2 

 43.2 

 56.8 

 46.4 

 53.6 



47.6 

 52.4 

 49.0 

 61.0 

 46.2 

 53.8 

 43.2 

 56.8 



1924.. 



\Females 



1 Males 



1926 



\Females 



(Males 



1926 , 



\ Females 



(Males _.. 





\Females 



