Table 3.— 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. 



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



^Mean for 16 August to 1 September 1961-63, for species other than sockeye salmon and after 11 August for 

 sockeye salmon. 



'Mean for 20 August 1962 and 1963. 



Table 4. — Abundance of spawning grounds and 

 average catch per unit effort of age sockeye 

 salmon in early July 1961-63 in lakes of the 

 Naknek River system. 



Area of potential Age 

 spawning grounds sockeye 

 per unit lake salmon 



Lake or basin area (ha/km') per tow 



Coville Lake 

 West End 

 Grosvenor Lake 

 Diuk Arm 

 Brooks Lake 

 South Bay 

 North Arm 

 Northwest Basin 



3.32 

 0.68 

 0.40 

 0.37 

 0.24 

 0.07 

 0.04 

 0.02 



96 

 3 

 3 



13 

 1 

 5 



1 

 2 



within each basin were not correlated (at P = 0.05, 

 Spearman rank correlation, Siegel 1956). However, 

 Coville Lake had by far the highest ratio of spawning 

 grounds to lake area and the greatest abundance of age 

 sockeye salmon in early July, and basins with the lowest 

 proportions of spawning grounds had smallest catches of 

 age fish in the tow nets. The lack of significant correla- 

 tion in all basins is likely due to many factors in- 

 cluding: sampling error, annual variations in success of 

 the various stocks, and incomplete knowledge of poten- 

 tial spawning grounds and their capacities to produce 

 fry. 



For the Naknek system, the abundance of age sock- 

 eye salmon in late August between 1961 and 1964 was 

 relatively constant. The mean number of fish per tow 

 (weighted by surface area of each basin) varied by a fac- 

 tor of <3— from 8.8 to 23.0 (Table 5). In addition, the 

 numbers of smolts produced by these age fish (esti- 

 mated in the Naknek River) were relatively constant. 

 The parent escapements for the age fish sampled from 

 1961 to 1964 ranged from 351,000 to 828,000 and for age I 

 fish from 351,000 to 2,231,000 (Table 5). 



From the foregoing discussion we see that the Naknek 

 system has a relatively constant number of age fish in 

 the fall of each year and, similarly, a relatively constant 

 number of smolts produced in the spring from 351,000 to 

 2.2 million parents (Table 5). It appears, however, that 



Table ^. — The systemwide mean catch per tow (weighted by area of 

 each lake) for age and age I sockeye salmon in the Naknek River 

 system in August 1961-64 and resulting numbers of smolts produced. 

 Age (I fish in .August can become age I or age II smolts. but age I fish 

 in .August can become only age II smolts (rarely age III). 



'Stewart, Donald M. (editorl. 1969. 1967 Bristol Bay red salmon 

 smolt studies. Alaska Dep. Fish Game, Inf. Leafl. 134. p. 69. 



the three external basins are not supporting the density 

 of age sockeye salmon that could be possible. Two of 

 the external basins. North Arm and Northwest Basin, 

 have by far the lowest spawning-area to lake-area ratios 

 of the system which apparently results in too few fry to 

 fully use the rearing areas. The third external basin. 

 Brooks Lake (fifth ranking in the system in ratio of 

 spawning area to lake area), may have enough spawning 

 grounds in Headwater Creek where the lake's major stock 

 is produced, but the true capacity of this stream is un- 

 known. 



PREDATION AS A LIMITING FACTOR 



Predation has been considered both significant in 

 limiting the number of sockeye salmon smolts produced 

 (Foerster and Ricker 1942; Rounsefell 1958) and insigni- 

 ficant (DeLacy and Morton 1943; Roos 1959). Many 

 species of fish and bird predators occur in the Naknek 

 system but they appear to have little effect on the 

 number of smolts. The best example of this little effect is 

 the large number of smolts per spawner produced by the 



