SEAWARD MIGRATION OF CHINOOK SAI<MON. 



65 



VARIATIONS DUE TO SEX. 



SEX PROPORTIONS. 



The proportions of males and fernales in the collections from the Columbia River, 

 while subject to considerable variation in different collections, are on the whole remark- 

 ably even. The data for each collection are presented in Table 54. There seems to be 

 no regularity to the variations noted, and the conclusion that males and females 

 migrate seaward in equal numbers throughout the year seems justified. 



Table 54. — Columbia River: Proportion op Males and Females, Average Length of Males 

 AND Females, and Length op Females as Percentage op the Length op Males. 



Date. 



Locality. 



Males. 



Percent- 

 age. 



Length 

 in milli- 

 meters. 



Females. 



Percent- 

 age. 



Length- 



In milli- 

 meters. 



As per- 

 centage ol 

 the male 



length. 



Apr. 13 



May 2 , 



May 10 \. 



May II 



May 25 '.. .. 



May 27 



June 13 1... 



Do 



July 19 



Aug. 12 



Aug. 30 and 31. 



Sept. 2 . . 

 Sept. is^ 

 iSept. 17. 



Cottonwood and Deer Islands 



Clackamas hatchery 



Lower Colimibia 



Estuary 



Columbia Rivernear Little White Salmon River. 



Clackamas hatchery 



Small creek near Point EUice 



Estuary 



Point EUice 



do 



Clackamas River 



Seufert. , 



Crandall's. 



Ilwaco. 



Oct. 16 1 Point EUice 



Oct. 17 1 Astoria 



Nov. 2 and 3 McKenzie River. . 



Dec. 3 to 8 Lower Columbia. 



1916; 



YEARUNGS. 



Mar. 31 to Apr. 2 .... ' Lower Columbia 



Apr. 13 Cottonwood and Deer Islands. 



May 10 Crandall's 



Jime 3 Clackamas River 



42-3 

 46.5 

 52- 3 

 46-7 

 44-5 

 S30 

 47- S 

 78-5 

 90. I 

 92. o 

 II3-8 



81. s 



121.3 



112. 2 

 127.9 

 107.1 

 95- S 



97.6 

 roy.o 

 106.0 

 112.0 



44.1 

 46.9 j 

 52.8 

 48.8 I 

 44.6 I 

 59- o 1 

 48.0 

 74-9 

 93-6 

 97.2 

 112.0 



80.3 



34.8 



124.7 



JI3-3 

 127.0 

 io6.o 

 93-4 



93-2 

 107.0 

 101. o 

 112.6 



104 

 loi 

 lol 



105 



100 

 111 

 101 



95 

 104 

 106 



99 



99 



lox 



102 



101 

 99+ 

 99 

 98 



96 

 100 



9S 

 100 -f- 



The only collections from the lower Sacramento River which were large enough to 

 give significant data and in which the specimens were sexed are those from Woods 

 Break, June 5 and 6, 191 1, and from Tisdale wier, June 24-26, 191 1. The sexes 

 were quite evenly balanced in both of these collections, 52 per cent males in the first 

 and 48 per cent males in the second. 



The situation in the McCloud River is somewhat complicated by the presence of 

 precociously matured males. Table 55 gives the percentages of males, both mature 

 and immature, and of females for each collection made in the McCloud River. The 

 sexes are present in approximately equal numbers, although there is a slight pre- 

 ponderance of females. Five and eight-tenths per cent of the total number of speci- 

 mens are mature males. This signifies that between 10 and 12 per cent of the males 

 which do not migrate during their first spring mature precociously during the following 

 summer and fall. 



