SALMON AND TKOUT IN ALASKA. 33 



They could be taken in small numbers by sinking the net several 

 fathoms. In Klawak Lake, however, on October 1 copepods seem 

 to have been abundant near the surface at any time of day, but 

 this was noted in comparatively shallow water, whereas the trials 

 on the other lakes had been made in water of greater depth. As 

 these forms have little horizontal movement it may be that their 

 presence in Klawak Lake during the day was to be accounted for 

 by the shallowness of the water. 



On the approach of darkness many of these crustaceans congregate 

 near the surface, and with that come the young sockeyes. Taken 

 soon after dark, these young fish commonly had the stomach filled with 

 Crustacea, with a number of insects, mostly flies and ^vinged ants, in 

 the esophagus. Over the entire surface of Yes Lake on a cpiiet even- 

 ing of August or September the presence of young fish could be 

 marked by the ripples. Sometimes they would jump clear of the 

 water, but more usually merely rise to the surface, apparently to snap 

 up the floating insects which they then sought. The depth at which 

 the fish remain during daylight is unknown, but is probably not great. 

 As noted above, they were obtained in Alturas Lake in 15 to 60 feet. 

 Whether an}^ lived at the greater depth is unknown, since the seine 

 had to be landed through lesser depths. It is unlikely they much 

 exceed such depth, since in summer the lower parts of small lakes are 

 unsuitable for the support of animal life.*^ 



Small fingerlings taken in Karluk River May 22 were feeding on 

 Crustacea, insects, and insect larvae. June 21 their food was almost 

 wholly insects and larvse; in the lagoon July 24 it was mainly insects, 

 but with some Crustacea. Specimens of slightly advanced size 

 (average 42 mm.) from Wood River, Western Alaska, submitted by 

 the collector without notes, contain both Crustacea and insects. Some 

 small fingerlings taken July 14 in the small creek tributary to Karluk 

 Lake contained insects and in one instance Crustacea. 



In Yes Lake October 12 tows immediately off the mouth of the 

 inflowing river in water of 47° F. took very few Crustacea. These 

 were probably not fTom the river water, for it, being somewhat colder, 

 would sink to the greater depths on entering the lake. October 17 a 

 net set over night in the river just above the lake took very few Crus- 

 tacea; river temperature 4.3° and lake 46° F. September 12 a net 

 was set at the foot of the lake in the outflow for fifty minutes and no 

 Crustacea taken; at the same time tows were made just above this 

 set net and a few Crustacea taken, but much fewer than were usually 

 taken in the main body of the lake. It would seem from these few 

 trials that there is a scarcity of Crustacea in both sections of the river, 



a See E. A. Birge, Gases dissolved in the waters of Wisconsin lakes. Transactions 

 American Fisheries -Society, 1906, p. 143-163. 



