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BULLETIN OF THE BUREAU OF FISHERIES. 
residents” remained in the headwaters of the Sacramento until the first winter rains, 
when they all went out. 
2. The salmon feed in the ocean for a period of years. For the chinook salmon 
this period is believed to be from three to five years, though the evidence is not entirely 
conclusive. The feeding period continues until maturity is reached. 
3. At the end of the feeding and maturing period the salmon migrate up the Pacific 
coast rivers to spawning grounds, which are sometimes only a few miles from the sea 
and scarcely beyond brackish water, but often for hundreds of miles, apparently always 
into cold fresh waters of the streams fed by springs, lakes, and mountain snow fields. 
4. It has long been known in a general way that the migration of O. tschawytscha to 
the spawning grounds is made wholly without food. 
5. The most striking and least expected climax to this interesting life cycle was 
discovered in 1894 by Evermann 01 for the species O. tschawytscha and O. nerka, namely, 
the fact that death invariably follows the spawning act. Evermann states, on page 260 
of his preliminary report upon the 1904 expedition, that on September 13th he counted 
72 dead salmon in a three-mile stretch of Salmon River and a mile or more of the lower 
portion of Alturas Creek in Idaho. Only one live salmon was noted on this date. He 
quotes numerous observations and conclusions of local men of the region tending to 
confirm the deduction expressed on page 1 53 of his final report as follows: ‘‘The chinook 
salmon which come to these waters die after spawning.” 
This brief salmon history is repeated here for the reason that it is the most effective 
way of presenting the setting for the problems that appeal to the physiologist. Of 
these problems I have in a previous paper 6 attacked the question of the acclimatization 
of the chinook salmon to fresh water after its life in the sea. That study was based on 
an examination of the blood and other body fluids. The special interest attaches to 
the osmotic changes during the passage of the fish through the various degrees of brackish 
water in the journey from the salt water of the sea to the fresh water of the rivers. The 
further osmotic change during the run up the river was also studied. 
The changes in the blood and body fluids are relatively slight and are carried on 
very slowly and gradually. The osmotic changes in the body fluids give little or no 
intimation of the length of time consumed by the fish in the transition from salt to fresh 
water. Neither do the osmotic changes give any measure of the duration of the sojourn 
in fresh water. In order to arrive at any adequate explanation of the profound changes 
in the tissues and organs during the migration it becomes almost a necessity that the 
rapidity of change in the environment and the total duration of the period be determined. 
The time element in this change is indeed the most important factor, yet an almost 
wholly unknown one. 
The present paper gives the results of a preliminary experiment designed to secure 
more tangible evidence as to the time element in the migration, especially on the Columbia 
o Evermann, B. W., op. cit., vol. xvi, p. 151. 
b Greene, C. W.: Physiological studies of the chinook salmon. Bulletin U. S. Bureau of Fisheries, vol. xxiv, 1904, 
p. 429- 
