328 



BULLETIN OF THE BUREAU OP FISHERIES. 



during the entire season we should have a considerable preponderance of males over 

 females on the spawning beds and we should also have indicated a relatively earlier 

 maturing of females than of males. Both of these results would be unexpected. While 

 no determination has been made of the ratio of the sexes in dog-salmon fry, analog)' with 

 other species of salmon would make it appear probable that males and females are in 

 approximately equal numbers at the time of hatching. If this be true, a final excess of 

 males in the spawning run could only be brought about by selective mortality directed 

 against the females. It does not seem probable that this exists. As regards an earlier 

 maturing of the females than of the males, producing a heavier percentage of females in 

 the younger groups, we can only note that this would be the reverse of what occurs in 

 king salmon, sockeyes, and cohos. 



In the Bellingham material, previously referred to, we found 67 per cent males and 33 

 per cent females, the proportion of males and females being approximately the same in 

 the third and the fourth year groups. In Doctor Fraser's material, the totals showed 

 59 per cent males and 41 per cent females. 



The Yukon specimens, 448 in number, contained 57.6 per cent males and 42.4 per cent 

 females. The 3-ye;ir fish had 53.3 per cent males; the 4-year fish, 53.8 per cent; and the 

 5-year fish 67 per cent. 



SIZE AT MATURITY. 



The length and weight frequencies are given in Tables 8 and 9, which follow. These 

 indicate unmistakably that the northern race is retarded in its growth and reaches a 

 smaller size in each year class than is attained in Puget Sound and the Gulf of Georgia 

 by fish of equal age. To compare with the average lengths of Yukon chums, we repeat 

 below those given by Doctor Fraser based on Qualicum and Nanaimo material. As 

 measurements of the latter were taken only to the base of the middle caudal rays and 

 our measurements include the length of the middle rays themselves, we have added 

 7>2 per cent to Doctor Fraser's measurements to make them comparable. 



Table 8. — Yukon Chum Salmon, 1920, Grouped by Age, Sex, and Length. 



