SALMON OF THE YUKON RIVER. 32 1 



all other streams thus far examined a considerable proportion of the adult salmon are 

 developed from fry that passed to sea during their first year and completed only a 

 small portion of their first year's growth in fresh water. This "sea type"' develops 

 at an earlier age than do those that tarry a year in fresh water, and it frequently 

 constitutes half or more than half the entire run. The absence of the "sea type" in 

 the Yukon may well be related to the severity of the fall and winter, the lateness of the 

 spring, and the shortness of the summer season. It would seem that the hatching of 

 the eggs, the absorption of the yolk, and the emergence of the fry from the gravels 

 must be correspondingly retarded. 



A third peculiarity of the Yukon king salmon consists in the retardation of the 

 age at which they attain maturity. In the Columbia River, where, owing to the use of 

 beach seines, wheels, and traps, the smaller salmon are captured in due proportion 

 with those of larger size, the youngest chinooks of stream type that are captured in the 

 spawning run are in their second year. These are all male fish, as are those of the next 

 larger size, which are in their third year. Female chinooks of stream type do not mature 

 in the Columbia until their fourth year, when they are not far inferior in numbers to 

 males of equal age. The commercially valuable portion of the Columbia River run con- 

 sists of 4 and 5 year fish. Comparatively few individuals reach their sixth year, and 

 none has to my knowledge been reported in its seventh year. The condition in the 

 Yukon is far different. No 2-year fish were secured, and but one 3-year fish, which 

 was a male, 16 inches long, the scale of which is represented in Figure 276. 



In spite of the fact that fishing was prosecuted exclusively by gill nets, which 

 during the king salmon run were of large mesh (8h or 8f inches), fish of diminutive 

 size were frequently entangled in the web and captured. Special attention was paid 

 to these, with the object of ascertaining the earliest age at which maturity would be 

 attained in the Yukon race. In addition to the 16-inch individual in its third year, 

 above noted, we examined 44 specimens ranging from 17 to 27 inches, all of them males, 

 in their fourth year. From this it is apparent that no female king salmon mature on 

 the Yukon until after their fourth year. They are therefore retarded at least one 

 year in reaching maturity, as compared with king salmon in the more southern part 

 of the range of the species. (See Figs. 277 and 278.) 



Continuing the examination of larger sizes we encountered the first 5-year male 

 at 25 inches, the males of this age ranging from 25 to 40 inches. In the fifth year, for 

 the first time, we encountered female salmon, but these were very few in number. 

 Among the 131 individuals in their fifth year that we have examined, selected wholly 

 by size without reference to sex, there are 119 males and only 12 females. This indi- 

 cates a still further retardation in age of maturing of females. Not only are there no 

 4-year mature females (so abundant in more temperate latitudes), but comparatively 

 few females develop maturity even at the age of 5. The 12 of which we have record 

 lie in size within the range of the 5-year males, the smallest being 30 and the largest 37 

 inches long. (See Figs. 279 and 280.) 



The male 6-year fish are numerous, the 79 individuals represented in our series 

 ranging widely from 29 to 48 inches. There is thus a wide overlap in size between the 

 5 and the 6 year fish, as is always the case, although, as will be noted, the 4 and the 5 

 year males show but little overlap. Among the 6- year fish, for the first time, females 



