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2000 2002 2004 
Brood year 
2006 2008 
Freshwater overwinter survival 
Parr abundance (000s) 
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Fishery Bulletin 119(4) 
Smolt abundance (000s) 
2002 2004 2006 2008 
Brood year 
Log smolt production 
Figure 2 
Time series of (A) overwinter survival and (B) smolt abundance by brood year (1999-2009), (C) the relation- 
ship between parr abundance and parr mid-eye fork length, and the relationships between log-transformed 
smolt production (estimated spring abundance) and the (D) first rotated component (RC1) and (E) second 
rotated component (RC2) for Chinook salmon (Oncorhynchus tshawytscha) during their freshwater period in 
the Chilkat River in Southeast Alaska. The horizontal dashed lines in panels A and B indicate mean freshwa- 
ter overwinter survival and smolt abundance. The regression line and 95% confidence interval (gray areas) in 
panel C are based on a regression of parr length on parr abundance. The regression lines and 95% confidence 
intervals (gray areas) in panels D and E are based on the principal component regression of RC1 and RC2 on 
smolt production. 
(coefficient of multiple determination [R?]=0.12, P=0.29) 
or smolt abundance (R7=0.05, P=0.49). 
Overall mean parr mid-eye fork length was 69 mm, rang- 
ing from an annual mean of 64 mm in 2006 to 74 mm in 
2005. Results from the simple linear regression indicate a 
significant negative relationship between parr length and 
parr abundance (R7=0.54, P=0.01) (Fig. 2). Over the study 
period, river discharge was consistent in fall and was 
higher and more variable in spring. The mean tempera- 
ture in fall was 3.2°C (range: 2.2—4.8°C), and the mean 
temperature in spring was —0.8°C (range: -3.8—2.5°C). 
There were no significant temporal trends in discharge 
(fall: P=0.45; spring: P=0.86) or temperature (fall: P=0.93; 
spring: P=0.74). 
Two RCs were retained for analyses on the basis of a 
scree plot and accounted for 39% and 38% of the overall 
