August 1961 and 1963, but relatively few fish in these 

 size groups were collected during this time in 1962 (see 

 section on length frequencies). These small and pre- 

 sumably late-emerging fish must originate within the 

 Grosvenor Lake basin because they have never ap- 

 peared in samples from Coville Lake or Coville River. 

 They may be progeny of adults that spawn in the shal- 

 low beach areas — the development of these fish could 

 be slower than normal because of low temperature and 

 oxygen levels accompanying severe winter conditions, 

 as has been reported for progeny of beach spawners at 

 Lake Kitoi (Smoker, 1957). 



Iliuk Arm. — Iliuk Arm has only one known intraba- 

 sin spawning ground of significant size, Margot Creek, 

 but it has enough extrabasin spawning ground (includ- 

 ing one tributary to the Savonoski River above Gros- 

 venor River) to yield a spawning-area-to-lake-area 

 ratio intermediate for the Naknek system — 0.37 ha per 

 square kilometer (Table 2). In addition to the known 

 grounds, it is suspected that spawning occurs in beach 

 areas within Iliuk Arm and in streams tributary to the 

 Savonoski River. A variable recruitment to Iliuk Arm 

 from Hardscrabble Creek in Grosvenor Lake is 

 known to occur, but the potential spawning ground of 

 Hardscrabble Creek is not assigned to Iliuk Arm. The 

 greatest number of recently emerged fry and interlake 

 migrants probably enter Iliuk Arm through Savonoski 

 River in sampling unit N-15 (Fig. 1). 



The abundance of age sockeye salmon increased 

 in Iliuk Arm in the summers of 1961, 1962, and 1963 

 (Fig. 5), but the relative abundance in the three sam- 

 pling areas varied from year to year (Fig. 7). This 

 variation may be due to year-to-year changes in the 

 relative number of recruits from different sources. The 

 trends in abundance in each of the sampling areas dur- 

 ing the summer in 1961 and 1963 are similar — mortality 

 or migration from the basin exceeded recruitment in 

 August in N-15 and N-14 and resulted in a shift in the 

 center of abundance to the downlake end of the basin 

 by the end of August (Fig. 7). This did not happen in 

 1962 when a relatively intensive summer migration of 

 age sockeye salmon down Grosvenor River was ob- 

 served. A similar migration occurred in Grosvenor 

 River during the summers of 1961 and 1963, but was 

 not well sampled. The analysis of variance showed 

 significant differences in abundance of juvenile salmon 

 (age and I combined) among sampling areas, times, 

 and in time-area interaction for 1962 and 1963 (Table 

 6). The differences between areas and the time-area 

 interaction were also significant in 1963, but time alone 

 was not when only age are considered. 



In 1964 Iliuk Arm was sampled only at the end of 

 August, and at this time (as in 1963), age sockeye 

 salmon were least abundant in the uplake unit, N-15. 

 and most abundant in the midlake unit. N-14. The 

 weighted average catch per tow for the entire basin at 

 this time was the greatest observed in Iliuk Arm from 

 1961 to 1964. 



South Bay. — South Bay receives sockeye salmon fry 

 from both outside and inside its basin. The only sig- 

 nificant source within the basin is Brooks River in 

 unit N-ll, although some fry may result from beach 

 spawning along the south shore of N-6. Because 

 downsystem migrants are recruited from Iliuk Arm, 

 the major recruitment from outside the basin is also 

 into N-ll. 



There was generally a gradient in abundance of age 

 fish in South Bay — the largest catches were made in 

 N-ll and the smallest in N-6 (Fig. 7). The greatest 

 abundance of age sockeye salmon recorded for 

 South Bay between 1961 and 1964 was at the end of 

 August 1964; at that time (as in 1963) the catches were 

 largest in N-ll and smallest in N-6. Analysis of vari- 

 ance for age indicated significant differences in 

 abundance among sampling areas, times, and time- 

 area interactions in 1961 and only in time-area interac- 

 tions in 1962 (Table 6). During the 4 yr of this study, 

 South Bay always had its greatest number of age fish 

 at the end of summer. 



West End. — The West End basin is the shallow out- 

 let end of Naknek Lake and is mostly less than 10 m 

 deep. It contains a few small spawning streams and the 

 extensive but essentially unknown spawning areas of 

 the upper end of Naknek River, i.e., between the 

 rapids and the lake. It is assumed that sockeye salmon 

 that hatch in the Naknek River move upstream into 

 West End shortly after they emerge. The evidence for 

 this is all negative — very few zero freshwater-age-type 

 adults return to the system, 3 and the Naknek River 

 and adjacent lagoons are probably not extensive 

 enough to rear enough smolts to produce the large 

 number of adults that spawn in the river in some years. 

 However, sampling with tow nets in the early period in 

 unit N-l never yielded many age sockeye salmon 

 (Fig. 7). 



The abundance of age sockeye salmon in the West 

 End in 1962 and 1963 (Fig. 5) was low in the early 

 period, high in the middle period, and low in the late 

 period. In 1964 this basin was sampled only on 3 Sep- 

 tember. Comparison of length frequencies of age Ofish 

 (discussed later) and their seasonal abundance in Iliuk 

 Arm and South Bay with similar data from West End 

 (Fig. 7) indicates that the movement of interlake 

 migrants during the summer does not continue on into 

 West End. This is also shown by the marked reduction 

 in abundance of age fish through South Bay from 

 sampling units N-ll to N-9 to the unit adjacent to the 

 West End, N-6. Although it seems that the movement 

 of age fish downlake does not extend through South 

 Bay by early September, the situation in Coville Lake 

 thoughout July 1963 should be recalled, i.e., areas of 

 greater abundance occurred both uplake and downlake 

 from an area of low abundance (Fig. 8) comparable to 



3 Unpublished data on file at National Marine Fisheries Service. 

 Auke Bay Fisheries Laboratory, Auke Bay. AK 99821. 



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