Grosvenor Lake and Grosvenor River. — The appar- 

 ent growth of age sockeye salmon each summer in 

 1961-63 in Grosvenor Lake and Grosvenor River is 

 shown in Figure 14. Grosvenor Lake was divided into 

 four areas for tow net sampling, but only in 1961 were 

 enough samples obtained to describe the growth for 

 each area. For 1962 and 1963 data for the four areas 

 were combined to calculate a single growth curve. Col- 

 lections were made in Grosvenor River only in 1962 

 and 1963. 



The apparent growth of juvenile sockeye salmon 

 from Grosvenor Lake is unique in two regards — the 

 average length offish in particular sampling areas fre- 

 quently decreased during the summer, and the fish 

 here were generally the smallest in the system on any 

 date. The size of the outmigrating fish captured in fyke 

 nets in Grosvenor River increased during the summer 

 and these fish were generally the largest in the system 

 on any date. 



G-l 

 G-2 

 G-3 

 G-4 



All units 

 combined 

 grosvenor river 



ot 



O 30 40 50 60 70 80 90 100 

 DAYS SINCE MAT 31 



Figure 14. — Curves of apparent 

 growth of age sockeye salmon cap- 

 tured in tow nets in sampling units of 

 Grosvenor Lake and in fyke nets in 

 Grosvenor River 1961-63. 



The decrease in average length of age sockeye 

 salmon in Grosvenor Lake in August was at least 

 partly due to a late recruitment of fry that had recently 

 emerged from the spawning gravels. This late recruit- 

 ment appeared each year from 1961 to 1963 and caused 

 the marked bimodality of length frequency curves 

 — these late recruits are represented in the peak on the 

 left in the 30- to 45-mm size range in Figure 15. The 

 spawning grounds and circumstances that produce 

 these fry in Grosvenor Lake are unknown, but a simi- 

 lar late recruitment has been observed for sockeye 

 salmon in Karluk Lake where spawning occurs over a 

 period of 4 to 5 mo (Burgner et al., 1969). 



Age I and older sockeye salmon were rarely taken in 

 tow nets in Grosvenor Lake and were relatively scarce 

 in fyke nets in Grosvenor River. 



Iliuk Arm. — Because there were no consistent dif- 

 ferences in size of age or of age I fish among the 

 three sampling units of Iliuk Arm in 1961-63 (for 1962, 

 growth curves for each unit are shown for compari- 

 son), the data from all the units were combined in 

 calculating the growth curves (Fig. 16). The apparent 

 growth of age fish showed little or no evidence of 

 slowing by 1 September and the average size of the age 

 fish in Iliuk Arm (Table 21) was generally inter- 

 mediate among the lakes of the system. This good ap- 

 parent growth was not expected in Iliuk Arm because 

 glacial flour makes the water quite opaque which 

 would result in little light penetration and thus low 

 photosynthetic activity. Both of these apparent 

 anomalies in growth (no slowing by September and 

 good apparent growth) are probably caused by the re- 

 cruitment of the larger fish from the upsystem areas 

 during the summer. 



The calculated growth curves for age I sockeye 

 salmon in Iliuk Arm for 1961-63 in the three units 

 combined (Fig. 17) resemble those of age fish in that 

 they do not show a decrease during the summer. There 

 was no trend in length of age I fish from one end of the 

 basin to the other (N-15, N-14, N-13). 



The length frequency diagrams for samples of 

 juvenile sockeye salmon from Iliuk Arm for 1961-63 

 also indicate a general uniformity among the three 

 sampling units (Fig. 18). The length frequencies are 

 generally bimodal, reflecting the presence of the two 

 age classes — age and age I. 



South Bay. — The seasonal changes in apparent 

 growth and length frequencies of young sockeye salm- 

 on from South Bay are similar to those from Iliuk 

 Arm. The data were too few to permit analysis of 

 growth by sampling unit, but do permit considerations 

 of apparent growth for the entire basin (all units com- 

 bined). As in Iliuk Arm the apparent growth of age 

 fish had slowed little if at all by 1 September (Fig. 19). 



The apparent growth curves for age I sockeye 

 salmon in South Bay for all units combined for 1961-63 

 (Fig. 20) do not have the same shape as those for Iliuk 



36 



