38 SALMON AND TEOUT IN ALASKA. 



vigorous fish whose superior feeding and digestive powers must have 

 advanced them beyond less thrifty earher-hatched are among the first 

 to reach salt water. 



In the British Columbia work it was shown that the movement 

 took place in the Thompson between the first of April and the middle 

 of July, the run of fry being largest in April, with a temperature of 

 41°, whereas in the Eraser, with an April average of 36°, both fry 

 and yearlings ran about one month later. The May temperatures 

 of the two streams are about equal — 46° for the Thompson and 45° 

 for the Fraser. In June they reached, respectively, 53° and 51°. In 

 the Wallowa River the movement apparentl}^ takes j^lace in April; 

 temperature unknown. 



It would seem from these observations that migration begins when 

 the water has reached a temperature of about 40°. At this time 

 surface food begins to be plentiful, hence the necessity of seeking 

 new feeding grounds would appear to be less than it is earlier in the 

 season. But before any definite statement can be made regarding 

 food influences it will be necessary to become familiar with the crus- 

 tacean life of the lakes. In the fall, at least some of the principal 

 crustacean forms are multiplying, 3'ielding an increased food supply 

 which might account for the continuance of crustacean feeders in 

 the lakes. Surface food at that season decreases, hence the tarriers 

 in the streams, as coho and king, must move on as winter approaches. 

 That scarcity of food has some influence might be supposed from the 

 usual paucity of aliment in the stomachs of moving fish. Occasionally 

 there will be found a stomach partially filled, but they seldom 

 contain more than a small part of the quantity ordinarily found in 

 examples taken from the resident individuals in any waters. It is 

 probable that the fish take only what presents itself without any 

 searching on their part. 



Floods seem to have little influence on the movement of yearlings 

 beyond the possible temperature influence. Fry are apparently swept 

 out by high water, movement near the mouth of the streams inclining 

 to be heaviest on falling water. No catch of yearlings was made in 

 daylight in the Naha where the water is clear, and though the catch 

 was uninterrupted during the night it appeared to be heaviest in the 

 evening, daybreak seeming again to accentuate the movement slightly. 

 In the muddy waters of the Fraser the catch was continuous through 

 the day. The apparatus used, however, would not be effective in clear 

 water in daylight, and its results can not be taken as a sure indication 

 of the time of movement. That there is little movement in day in 

 clear water is highly probable, since none has been directly observed. 



The exact behavior of the large schools of yearlings has been fully 

 described by Mr. Babcock in the report for British Columbia, 1903. 

 Thev were observed to move down the lake in the afternoons, running 



