BISSON and DAVIS: PRODUCTION OF JUVENILE CHINOOK SALMON 



represented the mean weights of the fish at the 

 beginning and end of the sampling interval, and t 

 was the sampling interval in days. Growth was 

 assumed to be linear over the relatively short 3-wk 

 period. Relative growth rates, which were essen- 

 tially the same as instantaneous growth rates, 

 were considered more appropriate for comparison 

 with relative food consumption rates. 

 Average biomass (B) was calculated as: 



B = 



B, + B-. 



where B^ and Bo represented the total weights of 

 the fish at the beginning and end of the sampling 

 interval. 



Production during each sampling interval was 

 calculated as the product of average relative 

 growth rate (ARG) and average biomass {B). 



The conversion of wet weights to calories was 

 accomplished by relating caloric content of tissue 

 to condition factors of the fish, where condition 



factor was taken as 100 times a fish's weight (g) 

 divided by the cube of its fork length (cm). Figure 

 9 of Warren et al. (1964:630), describing this 

 relationship for cutthroat trout, Salmo clarki, was 

 used for graphical estimates of calories per gram 

 of wet weight for juvenile chinook salmon. 



RESULTS 



Temporal Changes in Production 



Total production of chinook salmon in the heat- 

 ed stream was less than half that of the control in 

 1972 (Table 1). During the following year, produc- 

 tion in the control stream was approximately 30% 

 higher than in the heated stream. Mortality was 

 greatest immediately after release into the 

 streams, with populations attaining fairly stable 

 levels by late summer. Population biomasses rose 

 during winter and spring, were highest during 

 late spring, and gradually declined through sum- 

 mer and fall. The mean annual biomass in the 



Table l.-Mean production statistics of experimental chinook salmon populations. H = heated stream, 



C = control stream. 



767 



