Table 9. --Mean fork length (X) and standard deviation (SD) of age sockeye salmon taken in tow 

 nets in sampling units of Coville Lake and in fyke nets in Coville River by time periods, July 11 

 to September 1, 1963. 



Sampling 



July 7-11 



July 19-21 



July 51 -Aug. 1 



Aug. 15-17 Aug. 31-Sept. 1 



the outlet. In 1963 and 1964 the second sampling units 

 downlake (C-2U and C-2 respectively) yielded fewer 

 fish per tow than did the adjacent units uplake (C-1) or 

 downlake (C-2M and C-3) in July and the first part of 

 August. In mid- and late-August the rate of catch of 

 juveniles was greatly reduced in C-1 and it appears 

 that in 1963 many of the fish that had been in C-1 had 

 moved downlake into C-2U. Analysis of variance 

 showed significant differences in abundance among 

 areas of Coville Lake only in 1964 (the year when five 

 areas were sampled). In early July of both years the 

 average length of fish was smaller close to the" upper 

 end of the lake, but later, fish with the smallest aver- 

 age lengths were from the area closest to the outlet. 

 No dines or gradients among the areas appear in the 

 length data (Tables 9 and 10). 



The migration of age sockeye salmon from Coville 

 Lake to Grosvenor Lake began in mid-July, but did 

 not involve many fish until about the first of August. 

 In 1963 and 1964 juvenile salmon captured in fyke nets 

 in Coville River as they were leaving the lake were 

 generally larger than the average size of those remain- 

 ing in the lake (Tables 9 and 10). In 1964, when the 

 lake was sampled in most detail, the smallest average 

 size was found in the area adjacent to the outlet (Table 

 10). It appears that fish leaving the lake were the larger 

 members of the "normal" length frequency which re- 



sulted in a smaller average size for those remaining in 

 the area adjacent to the outlet. 



Grosvenor Lake. — The seasonal change in abun- 

 dance of age sockeye salmon in tow net catches 

 from Grosvenor Lake was generally similar to that of 

 the system as a whole (Fig. 3) in 1961 , 1962, and 1963; 

 i.e., the abundance increased during July and de- 

 creased in the latter part of August (Figs. 5 and 7). The 

 only exception was the unusually large (for Grosvenor 

 Lake) average catch for one series of tows made in 

 areas G-l and G-2 in the sampling in the late period in 

 1963 (Fig. 7). There was no marked concentration of 

 young salmon early in the summer in the pelagic areas 

 near the major spawning grounds (sampling units G-3 

 and G-4 — Fig. 1). 



The decline in abundance of juveniles in Grosvenor 

 Lake in August occurred during the time of an immi- 

 gration offish from Coville Lake via Coville River and 

 an emigration from Grosvenor Lake via Grosvenor 

 River. Several large catches of juveniles were made 

 with tow nets very close to the outlet of Grosvenor 

 Lake indicating that migrants accumulated here; these 

 data are not included in Figure 7 because this area was 

 not part of a regular sampling area. 



Sockeye salmon in the 27- to 39-mm size groups 

 were recruited to Grosvenor Lake in middle and late 



Table 10. --Mean fork length (T) and standard deviation (SD) of age sockeye salmon taken in tow 

 nets in sampling units of Coville Lake and in fyke nets in Coville River by time periods, July 4 

 to September 5, 1964. 



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