210 
Marine survival 
1998 2000 2002 2004 2006 2008 
Brood year 
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72 74 76 78 80 
Smolt length (mm) 
Fishery Bulletin 119(4) 
arine survial 
2000 2002 2004 2006 2008 
Brood year 
Log marine survival 
PC1 
Figure 3 
Time series of marine survival of Chinook salmon (Oncorhynchus tshawytscha) in the (A) Stikine River and 
(B) Chilkat River in Southeast Alaska. The horizontal dashed lines represent mean survival of Chinook 
salmon for all sample years, the brood years 1998—2009 for the Stikine River and the brood years 1999-2009 
for the Chilkat River. The (C) relationship between log-transformed marine survival and smolt mid-eye fork 
length in the Stikine River and the (D) relationship between log-transformed marine survival and the first 
principal component (PC1) in the Chilkat River during the same sample periods are shown. Regression lines 
and 95% confidence intervals (gray areas) are presented in the bottom panels. 
for BY 2004 to 3.9% (SE 0.6) for BY 2000. There was no 
significant temporal trend in marine survival of fish in the 
Stikine River (R?=0.08, P=0.36) (Fig. 3). 
Smolt Chinook salmon from the Stikine River were, on 
average, 74 mm in mid-eye fork length and ranged from 
70 mm in 2005 to 81 mm in 2009. There was no significant 
trend in smolt length over the study period (BYs 1998— 
2009); however, mean smolt size in 2009 (81 mm) was 
substantially larger than in previous years and was con- 
sidered an outlier in the data set. In summer (June—July) 
during the study period, mean SST was 12.1°C and SSTs 
ranged from 10.5°C to 13°C. Mean discharge in spring for 
the Stikine River was 1147 m°/s (range: 679-1574 m’/s), 
with no significant temporal trend (P=0.23). 
Log-transformed marine survival of Chinook salmon in 
the Stikine River was significantly positively correlated to 
smolt length (R?=0.26, P=0.05) (Table 5, Fig. 3). There were 
no significant relationships between marine survival and 
SST or between marine survival and spring discharge; there- 
fore, neither relationship was included in the final model. 
Discussion 
Marine survival 
Understanding factors influencing the survival and pro- 
ductivity of Chinook salmon during critical periods in 
