66 BULLETIN OI? THB BUREAU OF FISHERIES. 



Table 55. — Percentages of Males and Females in McCloud River Collections. 



Date. 



Females. 



Males. 



Total. 



Imma- 

 ture. 



Mature, 



1909: VRY. 



July 



September 



191 1 : 



September 



October 



November 



December 



1912: YEARJUNGS. 



January 



February , 



March , 



Average 



5t-6 



48.4 



42.6 



5.8 



RELATIVE SIZES OF MALES AND FEMALES. 



Table 54 gives, for each Columbia River collection in which the specimens were 

 sexed and which was large enough so that conclusions seem warranted, the average 

 length of the females as a percentage of the average length of the males. Dividing ibis 

 series roughly into quartiles, it is found that the average for the first six collections is 

 103.6; for the next five, loi; for the next five, 100.4; and for the last six, 98. The 

 cumulative evidence seems conclusive that among the younger fish the females average 

 slightly larger. In the case of the fish taken during and subsequent to September, 

 however, this condition is reversed, and the males are slightly larger than the females. 

 No explanation for this is offered, but the facts seem undoubted and worthy of record. 



The males and females from the two collections from the lower Sacramento are 

 approximately the same size. The length of the females in the collection from Woods 

 Break averages 98.3 per cent of that of the males. In the collection from Tisdale 

 wier the percentage is 102.4. 



Table 56 gives for each collection made on the McCloud River the length of the 

 females and of the mature males as percentages of the length of the immature males. 



Table 56. — McCloud River: Length of Females and of Mature Males as Percentages op the 



Length op Immature M.\les. 



Males. 



Imma- 

 ture. 



Mature. 



Females. 



1909: 



July 



September. 



September. 



October 



November. 

 December. . 



1912: 



January . . 

 February. 

 March .... 



VSARUNGS. 



100 

 100 



JOO 



100 

 100 

 300 



100 

 too 

 100 



109 

 106 



136 



IIS 



107 

 98.3 



97-5 

 98.9 

 100 

 99-7 



98. J 

 101.3 

 98.* 



