496 
Fishery Bulletin 107(4) 
age 2.2 sockeye salmon from Kvichak River in western 
Alaska from 1920 to 1997, a positive warm-regime 
effect occurred for Ml, but not for M2 (Isakov et al., 
2000). For ocean age-3 sockeye salmon from Bristol 
Bay from 1955 through 2000, scale growth increased 
after 1977 (following entry into saltwater and later 
in the year for Ml, after the peak summer growing 
season for M2, and during the peak growing season for 
M3 (Ruggerone et al., 2005). Such long-term patterns 
may continue to persist over a period of years during 
which C-0 regime conditions remain relatively stable 
or warm. 
Several mechanisms could explain the lower than 
expected Ml and M2 growth during the 1922-46 warm 
regime. First, growth rates derived from the scales of 
returning adult salmon, a small subset of the original 
smolts entering the ocean, may not accurately reflect 
the actual growth rate of the population of juvenile 
and immature salmon as a whole. However, the de- 
cline in freshwater scale growth in the mid 1940s 
corresponds with the reduced freshwater productivity 
in Karluk Lake over the period 1940s through 1993, 
as indicated by salmon-derived nitrogen levels in lake 
sediment cores from 1752 to 1993 (Gregory-Eaves et 
al., 2004), and the decline in scale growth supports 
the use of adult scales to estimate the past growth 
life history of the fish. Second, higher marine survival 
of smaller size classes indicate a larger proportion of 
slower growing fish in the surviving population that 
was sampled. Alternatively, an increase in inter- and 
intra-specific competition for food led to slower Ml and 
M2 growth during the 1922-46 warm regime. Finally, 
a change in the scale sampling method in the 1950s 
indicated a lower precision and accuracy of growth 
measurement in the years before the 1950s. Before the 
1950s, a scraping method was used to remove scales 
Table 3 
Correlation coefficients (r), P-values, and sample sizes ( n ) relating the growth of early run age-2.2 sockeye ( Oncorhynchus nerka ) 
from the Karluk system to climatic and oceanic (C-O) indices in the North Pacific Ocean. C-0 indices include the average spring 
(Mar-May) coastal sea-surface temperature (SST), cumulative winter and spring (Dec-May) coastal precipitation amounts 
(PREC), cumulative winter (Dec-Mar) coastal upwelling (UI), average winter (Dec-Mar) Atmospheric Forcing Index (AFI), 
and the average winter (Dec-Feb) Northern Oscillation Index (NOI). Smolt length (freshwater, FW), and juvenile (first-year 
marine, Ml), immature (second-year marine M2), and maturing (third-year marine, M3) growth were estimated from measure- 
ment on the scales of age-2.2 sockeye salmon. Relationships between variables in the correlation table are significant at 5% 
(P<0. 01=0. 05/5) indicated by *. 
C-0 indices for the North Pacific Ocean 
Growth 
Year 
variable 
SST 
PREC 
UI 
AFI 
NOI 
1922-2000 
FW 
r 
0.245 
0.070 
-0.101 
0.224 
0.025 
p 
0.109 
0.590 
0.493 
0.061 
0.870 
n 
44 
61 
48 
71 
47 
Ml 
r 
0.303 
0.158 
0.115 
-0.074 
-0.089 
p 
0.047 
0.223 
0.438 
0.538 
0.552 
n 
44 
61 
48 
71 
47 
M2 
r 
0.194 
0.283 
0.269 
0.151 
-0.269 
p 
0.201 
0.026 
0.061 
0.209 
0.064 
n 
45 
62 
49 
71 
48 
M3 
r 
-0.193 
-0.151 
-0.176 
-0.222 
0.017 
p 
0.200 
0.237 
0.225 
0.056 
0.908 
n 
46 
63 
49 
71 
49 
1951-2000 
FW 
r 
0.245 
0.120 
-0.118 
0.206 
-0.001 
p 
0.109 
0.439 
0.444 
0.181 
0.994 
n 
44 
44 
44 
44 
44 
Ml 
r 
0.303 
0.269 
0.210 
0.380* 
-0.060 
p 
0.047 
0.079 
0.171 
0.011 
0.700 
n 
44 
44 
44 
44 
44 
M2 
r 
0.194 
0.392* 
0.250 
0.308 
-0.251 
p 
0.201 
0.008 
0.097 
0.039 
0.096 
n 
45 
45 
45 
45 
45 
M3 
r 
-0.193 
-0.248 
-0.214 
-0.104 
0.077 
p 
0.200 
0.097 
0.153 
0.490 
0.612 
n 
46 
46 
46 
46 
46 
