SEAWARD MIGRATION OF CHINOOK SALMON. 



65 



VARIATIONS DUE TO SEX. 



SEX PROPORTIONS. 



The proportions of males and females 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. 



Tablb 54- — Columbia River: Proportion op Males and Females, Average Length of Males 

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



Date. 



Locality. 



Males. 



Percent- 

 age. 



FRY. 



1916: 



Apr. 13 



May 2 



May 10 



May II 



May as 



May 27 



June 13 



Do 



July 19 



AuR. 12 



Aug. 30 and 31 | Clackamas River 



1915: 



Sept. 2 



1916: 



Sept, IS 



1914: I 



Sept. 17 ' Ilwaco 



1915: I 



Oct. 16 ' Point EUice 



Oct. 17 ' Astoria 



Nov. 2 and 3 McKenzie River . 



Dec. 3 to 8 Lower Columbia 



Cottonwood and Deer Islands 



Clackamas hatchery 



Lower Columbia 



Estuary 



Columbia River near Little White Salmon River. 



Clackamas hatchery 



Small creek near Point Ellice 



Estuary 



Point Ellice 



do. 



Seulert 



Crandall's. 



YEARLINGS. 

 1916: 



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



Apr. 13 Cottonwood and Deer Islands. 



May 10 Crandall's 



June 3 Clackamas River 



64 



Length 

 in milli- 

 meters. 



43-3 



46. s 

 52- 3 

 46- 7 

 44.5 

 53- o 

 47- S 

 78. s 

 90 I 

 93.0 

 113-8 



81. s 



127.9 

 107. 1 

 95-5 



97-6 

 107.0 

 106.0 

 112.0 



Females. 



Percent- 

 aee. 



50 

 47 

 46 

 50 

 50 

 5° 

 47 

 56 

 54 

 38 

 SO 



52 



48 



49 



49 

 46 

 54 

 63 



Length- 



In milli- 

 meters. 



As per- 

 centage of 

 the male 



length. 



44-1 I 

 46.9 ' 

 52.8 

 48.8 

 44.6 ' 

 59.0 

 48.0 

 74-9 

 93.6 

 97.2 

 112. o I 



80.3 



104 

 101 

 101 

 los 

 100 

 III 

 loi 



95 

 104 

 106 



99 



99 



101 



102 



101 

 99+ 

 99 

 98 



96 



loo 

 95 



100+ 



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, 1911, and from Tisdale wier, June 24-26, 1911. 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. 



