SALMON AND TROUT IN ALASKA. 43 



August 2 about 600 fry and fingerlings were placed in a live-box 3 

 by 3 by 7 feet and towed from the river through the lagoon to the sea, 

 a trip of 5 hours. About 50 died en route, 150 died during the fol- 

 lowing night, and all but 70 in the next 24 hours. These were proba- 

 bly all Idng salmon. The totals show that all under 2 inches died; 

 6 percent of the fuigerlings up to 2h inches lived; 9-1 per cent of the 

 larger fingerlings lived. This result is singular enough when it is 

 noted that the king salmon young migrating out of the river are but 

 If inches in average length. It is inconceivable that they remain 

 in the fresh-water end of the lagoon until they have added 50 per 

 cent to their size. Two-inch fish were taken by Eigenmann in 1890 

 at Mare Island; 2 i -inch examples were taken by the writer in 189S 

 in San Pablo Bay in brackish water. There is every reason to believe 

 that fingerlings of the latter length under natural conditions are 

 perfectlv able to endure a standard salinity. The fact that this 

 species breeds only in rivers of considerable volume insures to the 

 young the opportunity of making the transition Avith the necessary 

 gradualness. In this they differ from the frequenters of short 

 streams, the fry of which species are doubtless able to endure a 

 sudden entry into salt water.'* 



The tendency of the resident king fingerlings to advance upstream 

 has been pointed out by Evermann in the report of the Columbia 

 River inquiry. The same habit was noted by Rutter, and the pres- 

 ence of king salmon in the catches at Karluk Lake verifies the earlier 

 observations, showing that the location of the breeding ground is not 

 closely indicated by the presence of the young. 



FOOD. 



The food of this species is alniost wholly insects, in large part from 

 the surface. The yearlings mentioned above, taken in Karluk Lake, 

 contained only insects, as did also the young taken at the mouth of 

 the river; but the 8 taken in the lagoon contained amphipods in addi- 

 tion. These large fish must be yearlings. Their presence in the lake 

 can be accounted for only, on the assumption that the fry or finger- 

 lings migrated into the lake the previous season, or that the yearlings 

 ascend the stream in the spring and summer. Since their natural food 

 would become scarce early in the fall it would seem to be improbable 

 that they would remain in the fresh water, whereas the length of the 

 river and the unnaturalness of an instinct that would impel female 

 yearlings to ascend it from salt water lay that supposition open to 

 serious question. They remain to be accounted aberrant individuals 



o Questions regarding the change from fresh to salt water, and vice versa, made by 

 all the salmon, have been discussed in detail by Sumner (Bulletin U. S. Bureau of 

 Fisheries, vol. xxv, 1905, p. 53-108) and by Greene (Bulletin U. S. Bureau of 

 Fisheries, vol. xxiv, 1904, p. 429-456). 



