Table 27. — Number of sockeye salmon in escapements and 

 abundance, age composition, and mean length of smolts pro- 

 duced, by year of spairninn, Kvichak system, 1952-60 ' 



[Size of escapements for 1952-54 based on stream surveys] 



Sraolts 

 pro- 

 duced 



Year of Fish Smolts per ^K^ composi- Mean length - 



spawning in escape- produced 1 million tion of smolts of smolts 



""'"t spawncrs Age I Age II A ge I Age II 



Index Index 



Thousands points' points' Percent Percent Mm. Mm. 



1962 5.970 109 



1953 321 1 95 6 1 28 72 89 116 



1954 241 1.15 4.8 78 22 92 120 



1955 251 2.65 10 6 23 77 96 114 



1956 9.443 181,32 19 2 54 46 84 99 



1957 2.843 19,14 67 13 87 80 108 



1958 535 2.15 4 86 14 91 118 



1959 680 2.96 4,4 27 73 93 110 



1960 14,630 '157,38 10.8 22 78 82 98 



• Abundance and length data for age II smolts from the 1958 

 escapement and age I smolts from the 1959 escapement supplied by 

 Alaska Department of Fish and Game. 



- Fork length of live anesthetized fish. 



■' Based on 24-hour catches. 



' Marriott (1965). 



Kvichak System 



Data on smolts produced (index points) and 

 the numbers of adults in the parent escapement 

 in the Kvichak system are presented in table 27 

 for 1953-60. 



The production of smolts per spawner in the 

 Kvichak system does not follow the classic repro- 

 duction curves described by Schaefer (1954), 

 Beverton and Holt (1957), and Ricker (1958). 

 Reproduction curves are based on the assump- 

 tion that the return per spawner is invei'sely re- 

 lated to the numbers of spawners, but in the 

 Kvichak system the maximum production of 

 smolts per spawner was produced by the rela- 

 tively large escapement of 9.4 million in 1956 

 (table 27, fig. 12). The escapement of 14.6 mil- 

 lion adults in 1960 apparently produced smolts 

 at a lower rate per spawner"- than that of 1956 

 but still greater than in most years of low 

 escapement. 



We assume that two reproduction curves are 

 applicable in the Kvichak system — one for large 

 escapements or "peak" years (over 5 million 



"^ The extraordinarily large return of sockeye salmon to the Kvichak 

 system in 1965 from the 1963 smolt run was unexpected. The smolt 

 production from the 1960 escapement must have been greater than 

 that indicated by the fyke net catches (shown as index points in table 

 27 and figure 12) because the return was disproportionately large. 

 and ocean survival was not unusually high for sockeye salmon from 

 other systems during this period. Intermittently occurring ice floes in 

 the Kvichak River between May 15 and June 1, 1963. made it difficult 

 to fish the fyke nets properly (footnote 4. table 27). 



16 



- 14 



to 



z 

 o 

 3 12 



H '0 



z 



UJ 



5 8 



UJ 

 Q- 

 < 



<J 6 



I 



CO 



 PARENT ESCAPEMENT 



D SMOLTS PRODUCED PER SPAWNER 



IkJ 



1953 1954 1955 1956 1957 1958 1959 I960 

 YEAR OF ESCAPEMENT 



Figure 12. — Number of sockeye salmon in parent es- 

 capement and relative numbers of smolts produced per 

 spawner, by year of escapement, in the Kvichak sys- 

 tem, 1953-60. 



fish) and one for small escapements or "low" 

 years (5 million fish or fewer). Two derived 

 points are available for calculating the relation 

 between smolt production and large escape- 

 ments, namely the most recent peak years of the 

 cycle, 1956 and 1960. Axiomatically, the repro- 

 duction curve includes the origin. A compound 

 exponential curve of a type suggested by Ricker 

 (1958) fitted to these three points necessarily 

 produces a flat dome. These data indicate that 

 the optimum escapement is less than the 1956 

 escapement, i.e., less than 9.4 million spawners 

 (footnote 16). 



We conclude that our estimate of the number 

 of smolts produced by the 1960 e.scapement was 

 too low, and, consequently, our estimate of the 

 optimum escapement for peak years is also too 

 low and will be raised as more data become 

 available. 



Naknek System 



Estimates were made of the number of smolts 

 produced in the Naknek system from each es- 

 capement in 1954-61 (table 28). Within these 

 years the escapements ranged from 0.28 to 2.23 

 million. 



The number of smolts produced increased as 

 the escapement increased, up to an escapement 

 of about 1 million (fig. 13). Beyond this point 

 the number of smolts tended to level off (at about 

 14 million smolts) or decline. 



SOCKEYE SALMON IN MAJOR RIVER SYSTEMS IN SOUTHWESTERN ALASKA 



441 



