FISHERY BULLETIN: VOL. 70. NO. 1 



because (1) they had poor ocean survival be- 

 cause of their small size; (2) the young over- 

 wintered in the river and migrated as age 2 

 smolts the following year; or (3) the young 

 never migrated at all. 



SIZE 



Only lengths were measured in 1956, and 

 lengths and weights were taken in 1965 and 1968. 

 A summary of average size data by age class 

 is presented in Table 7. Average lengths for 

 comparable age classes were greater in 1968 

 than in 1956 and 1965. Average weights, with 

 the exception of age 3 fish, were less in 1968 

 than 1965. Differences in lengths and weights 

 bet\N'een smolts for the two comparable years 

 (1965 and 1968) are reflected in the condition 

 factor (K), or coefficient of condition, which 

 indicates the relative well-being of the fish. In 

 1965 all age groups had K values greater than 

 1.0000; the range was 1.0544 to 1.3695. In 1968 

 all K values were under 1.0000; the range was 

 0.9187 to 0.9600. 



Information on the size of coho salmon smolts 

 from other spawning systems is presented in 

 Table 8. This table gives information for natural 

 or "wild" populations and not for artificially 

 hatched or reared stocks. Karluk Lake coho 

 salmon smolts were generally as large as smolts 

 of the same age from other areas or larger. 



POSSIBLE EFFECTS OF INCREASED 

 FRESHWATER RESIDENCE ON 

 SURVIVAL OF COHO SALMON 



The extended period of freshwater residence 

 resulting in coho salmon smolts of age 3 occurs 



in many systems but seems to be significant only 

 at Karluk. 



It is interesting to hypothesize what effect a 

 prolonged freshwater residence has on the an- 

 nual return of adult coho salmon at Karluk Lake. 

 Is an increased freshwater residence advanta- 

 geous or disadvantageous to survival of each 

 year class? What effect is there on marine sur- 

 vival of coho salmon if they take up ocean resi- 

 dence at an older age and consequently a larger 

 size? 



One means of answering these questions is to 

 examine freshwater and marine survival rates 

 for coho salmon from other areas. Survival 

 from egg to smolt (fresh water) and smolt to 

 returning adult (marine) are shown in Table 9 

 for some areas in California, Oregon, Washing- 

 ton, and British Columbia. Both freshwater and 

 marine survival for age 1 smolts from these 

 areas are quite variable: 0.13 to 12.00% and 

 3.77 to 11.79% respectively. The survival data 

 in Table 9 pertain to stocks in which the smolts 

 were primarily age 1 when they migrated to 

 sea, and the application of these data to more 

 northern stocks in which the smolts are mostly 

 older and larger when they migrate must be 

 done with caution. 



The small population of age 2 smolts from 

 Sweltzer Creek in British Columbia (Table 9) 

 is of interest because these fish are more compar- 

 able to Karluk smolts, in that they may possibly 

 have had a period of lake residence. Marine 

 survival of these older, larger fish was high. Of 

 72 fin-clipped migrating age 2 smolts, 19 (26%) 

 returned 5 or 6 months later as 83 fish (Foerster 

 and Ricker, 1953). Although marine survival 

 for these age 2 smolts might have been lower 

 if they had spent another year in the ocean, it 



Table 7. — Average length, weight, and condition factor of coho salmon smolts by age from Karluk Lake, 1956, 1965, 



and 1968. 



Age 



Length 



1956 



1965 



Weight 



Condition 

 factor 



Length 



Weight 



Condition 

 factor 



Length 



1968 



Weight 



Condition 

 factor 



112.5 

 136.3 

 141.7 

 177.0 



g 

 19.5 

 28.2 

 30.7 

 63.9 



1.3695 

 1 .0544 

 1 .0790 

 1.1523 



114.8 

 140.1 

 160.4 

 181.8 



e 



13.9 

 26.4 

 38.5 

 56.2 



0.9187 

 0.9600 

 0.9329 

 0.9353 



90 



