44 SALMON AND TEOUT IN ALASKA. 



that have 'obeyed neither the instinct to descend as fry nor that to 

 seek the sea in self-preservation upon the approach of winter. 



Migrating fry at the river mouth were largely empty, but a few 

 contained insect remains. The small fingerlings taken in a seine haul 

 in the lagoon also showed a purely insect diet. The lot taken by the 

 trap at the river's mouth averaged about 42 mm. (37-53) ; those 

 seined in the lagoon averaged 47 mm. (40-62), showing a growth of 

 about 5 mm. since reaching brackish water perhaps not over a month 

 previously. It was noted that late in July the number of these small 

 fish seen about the margins of Karluk Lagoon had greatly decreased, 

 indicating that the stay of the main. body in brackish water is short. 



COHO SALMON. 

 EARLIEST MIGRATIONS. 



As in case of the king salmon, a considerable number of coho young 

 remain as summer residents in the streams of their birth or in the 

 connecting lakes; but the greater part seek the sea as soon as they 

 become free-swimming. In the trap at station 2, on the Naha, the 

 fingerlings and yearlings taken largely exceeded the fry in number. 

 Both were taken from the middle of May until in Jime — the migration 

 period coinciding with that of the sockeye. It is possible that this 

 migration is in large part influenced by the sockeye movement. 

 "When yearlings of the latter species travel at the surface the cohos of 

 similar size may be impelled, to some extent, to school with them; 

 but the general absence of ^^earlings in the lakes early in the summer 

 indicates that the spring migration is instinctive and general for the 

 species. 



The fry reach the swimming stage somewhat later in the season than 

 the sockeye. The eggs, though requiring a slightly shorter incubation 

 period than those of the sockeye, are deposited much later in the fall. 

 By means of a trap which was set in Steelhead Creek on Naha Bay in 

 1904 the migration was found to be heavy as early as May 19, water 

 at 48°. On this date over 1 ,100 fry were taken, the net spanning the 

 entire stream. This run reached its maximum ten days later, when 

 over 3,000 fry were taken in a single night. It continued, however, 

 until sometime in July, when the temperature had reached 54°. In 

 this creek the humpback and the dog fry left in May, the coho from 

 the middle of May through June, and the steelhead in July. These 

 dates are approximate for these species in the Loring district. 



FOOD AND HABITS. 



The fry taken in the trap during the time from May to July 9 

 showed no appreciable increase in size, the catch average varying 

 irregularly between 37 and 40 mm. Of 600 measured, 85 per cent were 



