PROGRESS IN BIOLOGICAL INQUIRIES, 1935 413 



PINK SALMON 



The activities of this investigation in 1935, as in past years, were 

 confined mainly to the study of the pink-sahnon populations of 

 southeastern Alaska. Although the pink salmon are found in prac- 

 tically all of the waters of Alaska they are most abundant in this sec- 

 tion. The salmon populations- that support this fishery spawn in 

 hundreds of streams, varying greatly both in size and character of 

 habitat. Hence it is believed that the fundamental facts secured 

 from the study of the fishery in this section may be applied generally 

 to the pink-salmon fisheries of Alaska. Dr. Frederick A. Davidson is 

 conducting this investigation, assisted by S. J. Hutchinson. 



Studies were continued on the factors responsible for the fluc- 

 tuations in the abundance of pink-salmon populations that spawn in 

 the stream at Little Port Walter, Alaska. A counting weir has been 

 maintained in this stream during the past two seasons. In the sum- 

 mer of 1935, 6,075 pink salmon were tallied through the weir on their 

 migration upstream to the spawning grounds. Samples of this run of 

 salmon were taken at the weir throughout the migratory period. 

 These samples were studied for the purpose of determining the sex 

 ratio, fecundity, and racial characters of the pink salmon composing 

 the 1935 population. Observations on the spawning grounds in the 

 stream indicated a successful spawning of this population. During 

 the entire year records were kept of the prevailing meteorological 

 and hydrographic conditions that tend to influence the development 

 and mortality of the brood. Since the study of the pink-salmon 

 populations at Little Port Walter has been carried on for two seasons 

 only, no returns have yet been secured from known spawning 

 populations. 



The pink salmon migrating into the stream at Little Port Walter 

 were studied also from the standpoint of the physical and chemical 

 changes that take place within the body during their spawning migra- 

 tion from the sea. This is a continuation of the cooperative study 

 of this phase of the life history of the pink salmon that the Bureau 

 has been carrying on for the past few years ^^ ith the National Can- 

 ners Association of Seattle, Wash. The results of this study provide 

 information relative to the seasonal change in the market quality 

 of the pink-salmon pack each year that is of primary importance to 

 the canning industry. A preliminary report of the progress of this 

 study up to 1935 was completed during the past year and was pub- 

 lished as Investigational Report No. 33 of the Bureau. 



Owing to the need for further information concerning the migra- 

 tions of pink salmon through Clarence Strait in southeastern Alaska, 

 a pink-salmon-tagging experiment was conducted in this area during 

 the summer of 1935. The runs of salmon that migrate into Clarence 

 Strait from Dixon Entrance are composed of different races that 

 are bound for the spawning areas adjacent to the strait through the 

 entire course of 130 miles. McLean Arm, which is approximately 8 

 miles above the junction of Clarence Strait and Dixon Entrance, 

 was selected as the point for tagging. Through the courtesy of 

 the Alaska Pacific Salmon Co., 1,900 pink salmon were tagged from 

 their McLean Arm trap in lots of 400 and 300 each, during the 

 weekly closed periods beginning July 27 and ending August 17. 



