ABUNDANCE AND AGE OF KVICHAK RIVER RED SALMON SMOLTS 



305 



Figure 5. — Ice floes in the Kvichak River. (Photo by C. D. Becker.) 



Daii> Fishing Period 



The smolt index was based on the total catch 

 of the fyke net from 2200 to 0100 hours. This 

 3-hour period was selected on the basis of ex- 

 perience in the Nushagak system, where most 

 of the smolts leave the lake during the darkest 

 hours. The same nightly concentration of mi- 

 gration was found in the Kvichak River during 

 24-hour periods of fishing, as shown later. 



River Conditions and Fyke-Net EfiSciency 



Water velocity. — Desirable surface-water ve- 

 locity for fyke netting in the Kvichak River is 

 3 feet per second or more. This velocity is pre- 

 sumed necessary to prevent size selectivity, or 

 larger fish evading the net. Net selectivity in- 

 fluenced by water velocity in the Kvichak River 

 during 1955 was illu.strated by two nets fished 

 side by side at site A. The net in faster water, 

 3.1 feet per second, caught a greater poundage 

 and larger-sized fish than the net in water of 2.4 

 feet per second velocity (fig. 6). A second test 

 for size vselectivity caused by similar water 

 velocity was also made at the index site in 1955. 



The length frequencies of smolts taken during 

 this test, in which two nets were fished side by 

 side, are shown in figure 7. Both nets, fished in 

 a current velocity of approximately 3.5 feet per 



Site A, - 2.4 ft/sec. 



velocity, 107 fish 



Site Ao- 3. 1 ft/sec. 



velocity, 98 fish 



80 



90 100 



FORK LENGTH 



no 120 



N MILLIMETERS 



130 



Figure 6. — Length frequencies of smolts captured in 

 high and low velocity waters near site A from 2150 to 

 2210 hours, June 2, 1955. (Frequencies are smoothed 

 by moving averages of threes.) 



