102 SALMOX AND TROUT IN ALASKA. 



be seen either season, yet early in July the fry were migrating at the 

 rate of 200 to 300 per night and the creek was full of them till the fall 

 rains swept them out. 



Regarding the migration of sockeye young from Seton Lake in 1903, 

 Babcock states: ''The sight was amazing, and impressed one with the 

 fact that the percentage of natural fertilization of ova and the survival 

 of the resulting fr\" was greater than has been generally believed by 

 the authorities." 



It will be noted that eyed eggs were found in the Karluk creeks 

 on September 2. On this date the lake surface was 44°, ha\ang 

 fallen about 10° in as many days. With the shortening of the days 

 and prevalent cloudy weather the temperatures must fall rapidly 

 from this date, and it is c[uestionable whether anj^ but the earliest 

 deposited and hence most advanced eggs hatch before the onset of 

 freezing weather. 



Fry were found as late as August 1 in the stream just below 

 the lake; species unidentified. It is improbable that any consider- 

 able number of sockeye eggs hatch in time for the young to seek the 

 shelter of the lake for the winter. With the congealing of the 

 waters in the mountains the streams will become reduced in volume 

 and the entire bed must at times become frozen over, part by its 

 exposure and the remainder })y the formation of anchor ice. The 

 habit of the fish of spawning on the shallow riffles must unfailingly 

 subject the spawai to this influence. That it is not an extermi- 

 nating influence is due to the covering of gravel which the eggs have 

 received. The depth to which the bared beds freeze in winter has 

 not been ascertained. At points where a constant current perco- 

 lates through, such as must occur on the spawiyng riffles, it is im- 

 probable that tills depth is so great as might be suspected in view of 

 the low air temperatures. 



The efl'ects of freshets are largely nullified by the season at which 

 the}' occur. Late fall rains produce comparatively small floods for 

 the reason that the precipitation in the hills falls as snow. The 

 spring floods which come with the melting snows will find the eggs 

 in great part hatched, and fry are largely able to rise above the 

 deposit. 



RELATION OF SPAWNING HABITS TO NUMBER OF FISH. 



The spawning habits of a species bear a suggestive relation to its 

 abundance. The humpback in Southeast Alaska far outnumbers all 

 others. This is a region of small streams, and practically all that 

 have a suitable bed and are accessible from the sea are utilized by 

 this salmon. The small size of the adult humpback makes spawn- 

 ing possible in even shallower water than the sockeye or coho re- 

 quires. The number of eggs, about 2,000, is perhaps less than in 

 other species. The incubation period is less than that of the sock- 



