Figure 24. — Curves of apparent growth of age sockeye salmon captured in tow nets in Brooks Lake 



1961-63. 



water temperatures during August. The lakes with the 

 smallest combined catches of sockeye salmon and as- 

 sociated species. North Arm and Brooks Lake, were 

 intermediate in size of age sockeye salmon and in 

 water temperatures. I conclude that the abundance of 

 associated species such as pond smelt and stickle- 

 backs is not restricting the growth of juvenile sockeye 

 salmon. The growth of juvenile sockeye salmon seems 

 to be more directly related to temperature, but the 

 mechanism is not known. 



Differences in time of recruitment of fry. — A greatly 

 prolonged period of recruitment of fry from the spawn- 

 ing grounds has been reported for Karluk Lake on 

 Kodiak Island (Burgner et al., 1969) and in 1 yr at 

 Kitoi Lake on Afognak Island (Smoker, 1957). In the 

 Naknek system a late recruitment of recently emerged 

 sockeye salmon fry was apparent only in Grosvenor 

 Lake and the length frequency graphs for this lake 

 (Fig. 15) show two groups of age fish in August 1962 



and 1963. The location of the peak of the larger groups 

 indicates a smaller average length than in the rest of 

 the system, which is probably due in part to late 

 emergence and lake entry. Grosvenor Lake is inter- 

 mediate in the system in regard to summer water 

 temperatures (Table 22) and in productivity (Burgner 

 et al.. 1969). 



Differences in rates of dispersion of large and small or 

 fast- and slow-growing fish. — Differences in the aver- 

 age size of age sockeye salmon at various distances 

 from the major spawning grounds have been reported 

 in Lake Aleknagik of the Wood River system (Pella, 

 1968) and Iliamna Lake of the Kvichak system (see 

 footnote 12). In these two lakes differences in lengths 

 of juvenile sockeye salmon could be explained by the 

 more rapid migration of larger and faster growing fish. 

 Within the Naknek system the earlier migration of the 

 larger fish is apparent in the differences between the 

 size of the summer migrants in Coville River and the 

 fish collected at the same time with tow nets in Coville 



Table 22. --Mean surface water temperatures in August, mean number of age and age I sockeye 

 salmon and of pond smelt and threespine and ninespine sticklebacks, and mean fork lengths of 

 age sockeye salmon in seven lakes of the Naknek River system, 1961-63. 



J Mean of all observations made in each lake during tow netting in August 1961-63. 

 2 Mean for 1961-63, August 16 to September 1, for species other than sockeye salmon, and 

 post-August 11 for sockeye salmon. 



3 Mean for 1962 and 1963 on August 20. 



43 



