N-l 1 (high abundance), N-9 and N-6 (low abundance), 

 and N-4 (high abundance). 



The source of the relatively larger number of age 

 fish in N-4 in 1963 (Fig. 7) may have been the beach 

 spawning areas a'ong the south shore of N-6 (the base 

 of the north slope of Dumpling Mountain). But again 

 the situation may be comparable to the situation in 

 Coville Lake where juveniles were relatively scarce 

 over the deep water of the central basin but were 

 abundant over the shallower water at both ends. The 

 age fish may have passed through or around the deep 

 water of N-9 and N-6 without being sampled. The data 

 for 1962 and 1963 in Figure 7 indicate this may have 

 happened. If it did, this movement involved more of 

 the larger fish, for the average lengths of the age fish 

 were generally greater in the West End. 



North Arm. — The North Arm basin is the largest in 

 the system in surface area (over water deeper than 5 

 m) and volume, but has next to the lowest ratio of 

 potential spawning area to lake area (Table 2). In addi- 

 tion to having little intrabasin spawning grounds, re- 

 cruitment of juvenile sockeye salmon to North Arm 

 from other basins is limited by the drainage pattern 

 — the flow of water into North Arm is surface runoff 

 via several small streams and the flow out is through 

 narrow channels and over shoals. The two factors 

 — little intrabasin spawning and little recruitment from 

 other lakes — resulted in the lowest abundance of 

 juvenile sockeye salmon observed in the Naknek sys- 

 tem (Fig. 7). 



Northwest Basin. — The Northwest Basin appears to 

 be as much an entity as North Arm. The Northwest 

 Basin is small and comparatively deep and has only a 

 shallow connection to the rest of the Naknek system 

 via the West End. This basin has several small lateral 

 spawning streams along its north shore, but the ratio of 

 spawning area to lake area is the lowest in the system 

 (Table 2). The general abundance of age sockeye 

 salmon is also quite low — only North Arm and Brooks 

 Lake produced lower rates of catch. 



The type of spawning ground in Northwest Basin 

 — small lateral streams — is generally more intensively 

 utilized by sockeye salmon than the larger 

 intermediate-sized streams such as Bay of Islands 

 Creek in North Arm and Headwater Creek in Brooks 

 Lake (Burgner et al., 1969). The greater intensity of 

 use of the spawning grounds in the Northwest Basin 

 could account for the greater abundance of age sock- 

 eye salmon there (Fig. 7) than in North Arm or Brooks 

 Lake, in spite of their larger ratios of spawning area to 

 lake area. 



Brooks Lake. — Brooks Lake is similar to North Arm 

 and Northwest Basin in terms of abundance of 

 juvenile sockeye salmon (relatively low — Fig. 7), in 

 lacking recruitment from other basins, and in not hav- 

 ing a recruitment of fry in midsummer (based on shape 



of the 1962 catch curve [Fig. 5] and length frequency 

 data). In late summer and early fall it is usual for few 

 to several thousand age sockeye salmon to migrate 

 from Brooks Lake to South Bay. 4 



ABUNDANCE OF ASSOCIATED SPECIES 



In general, the catches of fish other than sockeye 

 salmon in tow nets were not consistent within or be- 

 tween years either for species or basin. The effects of 

 such factors as spawning migrations and recruitment 

 of age fish cannot be analyzed because there are not 

 enough data on age composition or length frequency. 

 Hence, only general comments can be made on the 

 abundance of associated species. 



The three species most commonly associated with 

 sockeye salmon in tow nets were pond smelt, three- 

 spine sticklebacks, and ninespine sticklebacks. In the 

 sections that follow, the catch-per-tow data for these 

 three species were summarized by semimonthly 

 periods for 1961-63 for areas and lakes. The lake aver- 

 ages were derived by the procedure used with the 

 salmon data. Although most sampling was in the sur- 

 face to 3-m zone in 1961, the data for that year are 

 treated here as equivalent to those of 1962-64 because, 

 as with juvenile sockeye salmon, the split-plot analysis 

 of variance tests did not indicate consistent differences 

 between average catches at the two depths (Table 11). 



Pygmy whitefish and least cisco were captured with 

 some type of gear in most basins of the system (Table 

 3), but because neither species consistently occurred 

 in significant numbers in the tow net samples, they will 

 not be discussed in this section. 



Pond Smelt 



Pond smelt occur in all basins of the Naknek 

 system 5 and have been taken by all suitable gear, but 

 they occurred in large numbers only in samples col- 

 lected with tow nets in Coville Lake. In Coville Lake, 

 tow net catches of pond smelt fluctuated greatly and 

 erratically during the season (Fig. 9) — much more than 

 the catches of juvenile salmon, which were charac- 

 terized by a relatively steady seasonal decline (Fig. 5). 

 Age pond smelt, which first occurred in late August, 

 were never the most numerous age group in the 

 catches. 



The comparatively large catches of pond smelt in 

 Coville Lake in 1963 may reflect good survival of the 



1962 year class. Generally favorable growing condi- 

 tions for fish in 1962 were indicated by the greater 

 growth of juvenile sockeye salmon that year. Signifi- 

 cant differences in abundance were indicated in the 

 split-plot analysis of variance for depth in 1962 and 



1963 and for interaction of depth-time in 1963 (Table 



4 From Brooks Lake Field Station Reports. 1961-65, on file Na- 

 tional Marine Fisheries Service, Auke Bay Fisheries Laboratory, 

 Auke Bay, AK 99821. 



5 Pond smelt have not been reported from Brooks Lake, but 

 have been seen in a tributary to Brooks Lake and in Brooks River 

 near the outlet of Brooks Lake (Heard, Wallace, and Hartman. 

 1969). 



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