THE SALMON OF THE YUKON RIVER. 



By Charles H. Gilbert, 

 Professor of Zoology, Stanford University. 

 J* 



CONTENTS. 



Pago. 



Introduction 317 



The king salmon (Oncorhynchus ischawylscha). . . . 318 



Rate of travel 318 



Growth and age at maturity 320 



The chum or dog salmon (Oncorhynchus keta). . 325 



Rate of travel 326 



Year classes 326 



Proportions of sexes 327 



Size at maturity 328 



Growth and scale readings 329 



The sockeye salmon (Oncorhynchus nerka) 330 



The coho salmon (Oncorhynchus kisutch) 331 



The humpback salmon (Oncorhynchus gorbusrha) 332 



INTRODUCTION. 



The summer of 1920 was spent by the writer, in company with Henry O'Malley, at 

 that time field assistant of the United States Bureau of Fisheries, in investigating the runs 

 of salmon to the Yukon River. The primary object of the expedition was to ascertain the 

 advisability of permitting the operation of one or more salmon canneries on the Yukon, 

 in view of the possibility that they might so curtail the salmon supply that it would fail 

 to provide natives, and white inhabitants as well, with the stores of fish that they find 

 essential under the rigorous conditions of the far northern climate. It was to be deter- 

 mined whether there existed an excess above the needs of the inhabitants that could 

 safely be used for commercial purposes for export beyond the boundaries of Alaska. 



This phase of the situation has been dealt with in a report to the Commissioner of 

 Fisheries and was published in 1921. 1 .Some of the details that are given in that report 

 concerning the movements of the salmon during their run and the rate of travel that they 

 maintain in their ascent of the river are herein repeated, but the body of the present 

 paper is concerned with the growth-history of the Yukon salmon and the ages at which 

 they have reached maturity. The Yukon River is near the northern limit of range for 

 the Pacific salmon. The effect of the arctic cold on growth and age of maturing is an 

 interesting problem. 



1 Investigation of the Salmon Fisheries of the Yukou River, by Charles H. Gilbert and Henry O'Malley. Bureau of 

 Fisheries Document No. 909a, pp. 128-154. Washington, 1921. 



317 



