Yasumiishi et al.: Effect of population abundance and climate on 2 populations of Oncorhynchus keta 
213 
Table 5 
Validation statistics based on the application of the 
growth models for age-0.3 male chum salmon ( On- 
corhynchus keta ) from Quilcene River, Washington to 
the reserved observations. GLS was the generalized 
least squares regression model. Growth indices includ- 
ed 1 st immature year (SW2), 2 nd immature year (SW3), 
and maturing (SW4) life stages. GLS/VAR was the GLS 
and vector autoregression-integrated model. Statistics 
include sample size (n), coefficient of variation (CV), 
coefficient of determination (r 2 ), T^-statistic, P - value of 
the .F- statistic, F-statistic of model deterioration (Fdet.), 
P- value of Fdet. (P-det.), and the Schwarz’s information 
criterion (SIC). Negative r 2 values and associated F and 
P values were not shown for the SW2, SW3 and SW4 
models. 
SW2 
SW3 
SW3 
SW4 
GLS 
GLS 
GLS/VAR 
GLS 
n 
7 
7 
7 
6 
CV 
0.09 
0.07 
0.11 
0.09 
r 2 
0.06 
F 
0.18 
P 
0.98 
F-det. 
2.52 
1.14 
4.13 
1.79 
P-det. 
0.04 
0.37 
0.001 
0.14 
SIC 
57 
47 
56 
44 
increasing body of growth studies on chum salmon pop- 
ulations from southcentral Alaska (Helle, 1979), west- 
ern Alaska (Agler et al., 2013), Russia (Zavolokin et al., 
2009), Japan (Kaeriyama et al., 2007), and Korea (Seo 
et al., 2006). Contrary to growth in the Asian popula- 
tions, juvenile and maturing growth did not increase 
in the mid-1990s, indicating that productivity on the 
North American continental shelf remained relatively 
lower than that in the western Pacific Ocean. In ad- 
dition, we back-calculated indices of chum and pink 
salmon abundance using harvest data, age composition, 
and mortality schedules; therefore, this index was more 
likely to accurately represent the actual abundance of 
chum salmon than estimates based on harvest alone. 
We found that size of the adult chum salmon was pri- 
marily related to growth in oceanic waters during the 
immature life stage on the basis of data from the early 
1970s to the mid-2000s and that immature growth was 
related to population abundance and to climate in prior 
years. Further research needs to focus on identifying 
and better understanding factors influencing immature 
growth in order to allow for more accurate predictions 
of size-at-maturity for returning chum salmon in a 
given year. 
Trends in size and growth 
Size at maturity was essential for determining fecundi- 
ty, breeding success, and survival of progeny in salmon 
Table 6 
Lehmann’s correlation coefficients to test the difference 
among the mean square errors of the growth models 
for age-0.3 male chum salmon ( Oncorhynchus keta ) from 
Fish Creek and the Quilcene River. Growth indices in- 
cluded 1 st immature year growth (SW2) and 2 nd im- 
mature year growth (SW3). GLS=the generalized least 
squares regression model. GLSAAR=the GLS and vec- 
tor autoregression-integrated model. Models were not 
statistically significant at a 5% level of significance. 
Stock and life stage 
Fish Creek Quilcene River 
SW2 SW3 
Sample method GLS GLS 
Insample GLS/VAR 0.44 0.41 
Outsample GLS/VAR -0.08 -0.50 
(Helle, 1979, 1989; Schroder, 1982). Therefore, it was 
important to understand factors influencing growth. 
Largebodied female salmon can dig deeper redds (van 
de Berghe and Gross, 1984), produce more eggs (Helle, 
1989), produce larger eggs and fry (Koski, 1975), and 
have progeny with higher survival probability (Helle, 
1979; 1989). Larger males are more aggressive and are 
more successful in competing for a mate than smaller 
males (Schroder, 1982). In the ocean, larger salmon 
consume more prey, more energy-rich prey, and more 
diverse prey than smaller salmon (Davis et al., 2009) 
and therefore have a competitive advantage for larger 
fish. Because a growth advantage once gained has a 
high likelihood of being maintained throughout the 
life of a fish, these factors highlight the significance of 
understanding the impacts of climate and population 
abundance on the marine growth and ultimately on the 
size at maturity of salmon. 
In this study, the temporal trends in the body size at 
maturity of chum salmon from the two stocks from the 
early 1970s to early 1990s were similar to decreases in 
early juvenile, middle juvenile, immature, and matur- 
ing growth for Fish Creek chum salmon and to decreas- 
es in the immature and maturing growth for Quilcene 
River chum salmon. Our results are comparable to ob- 
served declines in body size of Hokkaido chum salmon 
in the mid-1980s that were linked to reduced growth 
during the 2 nd immature and maturing stages for years 
1970-1994 (Kaeriyama, 1998). Similarly, the reduction 
in the adult (mature) body size of chum salmon from 
the Anadyr River in Russia during the mid-1980s was 
linked to reduced growth in the immature and matur- 
ing stages (Zavolokin et al., 2009). Although the gen- 
eral trends in size at maturity from the 1970s to the 
1990s were similar for different populations around the 
Pacific Ocean, the changes in adult size were linked 
to different developmental stages, namely the imma- 
