308 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Fish in groups of 10 to 15 were anesthetized 

 in urethane ' or chlorotone, measured from the 

 tip of the snout to the fork of the tail, and 

 returned to a container of fresh water to revive. 

 Each length was tallied together with informa- 

 tion identifying the sample. At a later date all 

 length-frequency tabulations for 1 day were 

 weighted according to the magnitude of the 

 fyke-net catches during the daily 3-hour index 

 period and combined in a composite season 

 sample. 



Scale Samples 



Ages determined from length frequencies 

 were verified from scale samples. Scale samples 

 were taken from fish used in the length-fre- 

 quency measurements, and the fish selected for 

 scale samples were immediately preserved in 5- 

 percent formalin. Several weeks after preser- 

 vation, the fish were remeasured and the scale 

 samples removed. Shrinkage of preserved speci- 

 mens was adjusted by a shrinkage factor deter- 

 mined by measuring individual fish before and 

 after their preservation. Shrinkage from live 

 length varied from 3 to 7 percent, depending on 

 the length of the fish, or about 4 millimeters. 

 Four to eight scales were taken from each fish 

 from immediately above or below the lateral 

 line and between the dorsal and adipose fins. 

 These scales were mounted in a spread pattern 

 on a 1- by 3-inch glass slide. Scales from eight 

 fish were mounted on a slide, with the length 

 of each fish recorded on the slide label. The 

 scales were covered with a second glass slide 

 and the two slides taped together. 



All scales were studied to determine number 

 of annuli and amount of spring growth since 

 formation of the last winter annulus. Spring 

 growth does not appear on the scales of smolts 

 that migrate soon after lake ice breakup, but it 

 becomes apparent about midway through the 

 migration season and the growth increases dur- 

 ing the summer. 



ABUNDANCE OF SMOLTS 



The annual Kvichak River smolt index was 

 based on the number of fish captured in a single 

 fyke net fished each year of the study under 



similar fishing conditions and for the duration 

 of the migration. This method was designed to 

 detect fluctuations in the number of smolts from 

 year to year. The number of smolts and cal- 

 culated index values for the 5 years of the study 

 are presented in table 4. The daily smolt catches 

 each year are shown in appendi.x tables 1 

 through 5. 



Table 4. — hidices of smolt abundance in the Kvichak 

 River 



1 The total number of smolts caught in 1958 has been arbitrarily 

 assigned the base value of 100.0. 



Some adjustments of each year's total catch 

 have been necessary. For the first 3 years of 

 the study, some smolt catches from secondary 

 net sites A and C were included to obtain the 

 index value. The use of these sites was neces- 

 sary because ice in the river prevented fishing 

 at the index site early in the season and because 

 the biologists who did the counting were in- 

 volved with other duties late in the season. Dur- 

 ing 1955 and 1957, the catches from net-sites 

 A and C were included when the two nets were 

 contributing less than 7 percent of the season's 

 catch. During the period of the ice flow in 

 1956 a substantial migration was detected at 

 site A ; and, consequently, an evaluation of these 

 catches in terms of principal index-site catches 

 was necessary. This evaluation was made on 

 the basis of simultaneous fishing at the index 

 site and site A for 4 days, from June 7 through 

 June 10 (table 5). The ratio of catches of site A 

 to those of the index site for the 4 days was 



Table 5. — Si'tnultancoits smolt catches at site A and at 

 the index site, 1956 



1 Urethane has not been used e.xtensively since reports of its 

 carcinogenic elTects were published. 



