FISHERY BULLETIN: VOL. 74, NO. 4 



Table 18.-Densities of juvenile coho salmon by brood year (1963-66)' on dates of population estimates in Sashin Creek and Funny 



Creek. Separate estimates are included for three areas of Sashin Creek. 



'The estimated populations of fish of a brood year at age I (second summer of life) include an average of 11% age II fish from the pre- 

 ceding brood year. 



^Estimate of density calculated from population obtained from expansion of estimated populations in upper area and Funny Creek. 



2 Just before emergence to first estimate of 

 fry population (end of period 1 to late 

 June or mid-July). 



3 First to second estimate of fry population 

 during first summer (end of period 2 to 

 late July or mid-August). 



4 Second estimate of fry population to first 

 estimate of population as yearlings (end 

 of period 3 to late June or mid-July of the 

 following year). 



5 First to second estimate of yearling 

 population (end of period 4 to late July or 

 mid-August). 



Although the lengths of the corresponding periods 

 for the three brood years are similar, they varied 

 according to vv^hen the population estimates were 

 made. 



We compared the estimates of the population at 

 the end of each of the five periods with the original 

 population (potential egg deposition) to obtain 

 percentage survival during nearly 2 yr of their 

 freshwater life for the brood years 1963-65 (Table 

 19). Survival from potential egg deposition to just 

 before fry emergence (period 1) was estimated to 



Table 19.— Survival through five periods' in the freshwater life 

 of three brood years of coho salmon in Sashin Creek, expressed as 

 a percentage of potential egg deposition. 



See text for explanation of time covered in each period. 



be 15%, 22%, and 26% (mean of 21%) for the 1963, 

 1964, and 1965 broods, respectively. Other inves- 

 tigators have found similar survival to emergence 

 for coho salmon. A range in survival to emergence 

 in terms of counted fry of 11.8% to 40.0% (mean of 

 21.0% and 26.5%) is reported for two tributaries of 

 the Cowichan River, British Columbia (Pritchard 

 1947). Koski (1966) obtained survival values to fry 

 emergence of 0% to 78% (mean of 27.1%) for 

 individual redds of coho salmon in three streams 

 tributary to Drift Creek. For Karymaisky Spring 

 on Kamchatka, Semko (1954) reports survival to 

 emergence of 0.8% to 21.4% (mean 10.6%). 



Because the lengths of the five periods were not 

 equal and a specific period was not the same length 



918 



