42 SALMON AND TROUT IN ALASKA. 



As in the Sacramento, it was found that a small number of young 

 king salmon remain in the river until they reach the size of finger- 

 lings. Five yearlings averaging 111 mm. total length were taken in 

 Karluk Lake June 5; 2 females slightly smaller, June 23 and 30; 2 

 males, 115 mm., were taken in an upstream trap at the mouth of the 

 river July 3, and 2 slightly smaller examples on the 5th. This would 

 indicate that they were feeding in the river at this date. In a seine 

 haul on the lagoon 4 males averaging 130 mm. and 4 females aver- 

 aging 135 mm. were taken July 24, in company with large numbers 

 of sockeye and king fry and a few coho and sockeye fingerlings (or 

 yearlings) and small trout. It has not been noted that these feeding 

 fingerlings migrate in schools, but Rutter has shown that in the Sac- 

 ramento, with the growing scarcity of food in the fall and the oppor- 

 tunity offered by fall freshets, they gradually forsake their summer 

 quarters. 



The "summer residents" were also found in abundance in the 

 Columbia River work of 1895. The altitude of these breeding waters 

 and the proximity of snow tends to reduce the temperatures below 

 those of the Sacramento, altitude doubtless effecting for them what 

 latitude does for the Karluk. The bottom temperatures given for 

 Alturas Lake '^ can not be relied on, owing to the character of the 

 instrument ^vith which they were taken. It is probable that the 

 bottom temperature at 150 feet is little over 40° F., as shown by 

 later observations in Wallowa and other lakes. The falling air 

 temperatures of the autumn must be closely followed by the water. 

 The circulation in these lakes must be comparatively small and the 

 cooling of the waters rapid. 



Dr. Evermann's researches show that the lake temperatures, and 

 consec[uently those of the spawning waters, fall rapidly after August. 

 Since the king salmon deposits its eggs late in August and early in 

 September, it is likely that the early freezing of the water arrests the 

 development of the fry, so that they can not arrive at the migrating 

 stage until some time in the spring. But, in so far as the tempera- 

 tures taken in Idaho are somewhat above the corresponding obser- 

 vations in Karluk Lake, it is probable that the downstream migration 

 of the main schools would have been completed before the arrival of 

 the investigating party in July. The size and growth of the finger- 

 lings found exhibit a condition exactly analogous to that described by 

 Rutter for the Sacramento and observed in a less degree for the Karluk. 



EFFECT OF CHANGE FROM FRESH TO SALT WATER. 



Rutter demonstrated that the king salmon fry is unable to sustain 

 immediate transfer from fresh water to sea water. In addition to 

 his experiments on the California salmon, he made a test at Karluk, 



aEvermann, Bulletin U. S. Fish Commission, vol. xvi, 1896, p. 157. 



