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Fishery Bulletin 1 14(2) 
ture and maturing life stages in the western Pacific 
and the juvenile, immature, and maturing life stages 
in the eastern Pacific. From the mid-1990s to the mid- 
2000s, increases in body size of adult chum salmon in 
our study were related to increases in growth during 
the immature life stage in offshore waters. 
Juvenile and maturing growth of chum salmon 
from the two populations in our study did not re- 
cover from the size reductions of chum salmon from 
the early 1970s to the early 1990s. Conversely, juve- 
nile chum salmon released from Japan into the Sea of 
Okhotsk had lower growth from the late 1960s to the 
mid-1980s and higher growth from the mid-1980s to 
the mid-1990s, possibly because of reduced ice cover 
and warmer sea temperatures during summer and fall 
(Kaeriyama et al., 2007). Farther north in Russia, ju- 
venile growth of chum salmon departing the Anadyr 
River was relatively stable from the early 1960s to 
the late 2000s, but slightly higher in the late 1990s 
(Zavolokin et al., 2009). The difference in the patterns 
in juvenile growth of chum salmon between the east- 
ern and western Pacific Ocean populations indicates 
that conditions in the 1990s were more favorable for 
juvenile chum salmon in the western North Pacific 
than in the eastern North Pacific Ocean. Declines in 
zooplankton biomasses were documented in both re- 
gions of the North Pacific Ocean from the mid-1970s 
to the early 1990s but remained 50% to 300% higher 
in the western North Pacific (Sugimoto and Tadokoro, 
1997). Lower ocean productivity in the eastern Pacific 
may have accounted for the lower juvenile growth of 
the two chum salmon populations in our study during 
the 1980s and 1990s. We could not include indices of 
zooplankton biomass in our models because sufficient 
data were not available. 
In our study, increases in size at maturity in the 
1990s were linked to increases in immature growth. 
However, in the validations with reserved data, our 
models did not capture the entire increase in the 1 st 
and 2 nd immature years of growth for Fish Creek and 
Quilcene River chum salmon. Alternative conditions 
may exist that can explain the increase in immature 
growth in the mid-1990s. For example, the annual 
growth during age-0.1, 0.2, and 0.3 immature stages 
measured on the scales of adult chum salmon from Ko- 
rea was positively correlated with zooplankton biomass 
in the Bering Sea (Seo et al., 2006), thus establishing 
a potential pathway for climate-induced changes in 
growth. Helle and Fukuwaka (2009) found a strong 
positive correlation between body size of maturing 
chum salmon from the eastern North Pacific and Japan 
and the spring and summer sea temperatures in the 
southeastern Bering Sea for the period 1977-1994, but 
weak and often negative correlations during the 1960- 
1976 and 1995-2006 periods. Decadal-scale changes in 
growth of N. American chum salmon may be related to 
shifts in their ocean distribution, e.g., northwestward 
shifts into the Bering Sea during summer in warm 
periods vs. remaining in the GOA during cool periods. 
Additional factors, such as zooplankton biomass and 
prey diversity, need to be investigated to determine the 
cause of increases in body size in the mid-1990s. 
Growth and abundance 
Evidence of density-dependent growth was detected in 
the juvenile chum salmon from Fish Creek, but not in 
those from Quilcene River. One explanation for this 
discrepancy in growth patterns may be the much high- 
er abundance of pink and chum salmon in SE in com- 
parison with WA and OR during our study period. In 
fact since 1995, the harvest of pink and chum salmon 
has been 5 to 12 times higher in the GOA region than 
in WA, OR, and BC combined (Eggers et al. 1 ). Annu- 
ally, Alaska hatcheries release approximately 1.5 bil- 
lion juvenile salmon into the Pacific Ocean (Alaska De- 
partment of Fish and Game, available at website, data 
obtained in September 2012) and the primary species 
released are pink and chum salmon. Pink salmon are 
primarily released from Prince William Sound hatch- 
eries, whereas chum salmon are the primary species 
released from hatcheries in SE. In the waters along the 
Japan Sea coast of Honshu, Japan, where hatcheries 
release 100-300 million juvenile chum salmon annu- 
ally, the relative weight of juvenile chum salmon stom- 
ach contents decreased as their density increased — a 
finding that was postulated to be the result of juvenile 
chum salmon depleting prey abundances (Fukuwaka 
and Suzuki, 2000). Similarly, early marine growth of 
Atlantic salmon (Salmo salar) from the Miramichi 
River in eastern Canada was inversely related to sub- 
sequent recruitment (Friedland et al., 2009). We found 
an inverse relationship between the mean body length 
of juvenile chum salmon and the surface trawl catch of 
juvenile pink and chum salmon from continental shelf 
waters off Icy Point in the GOA from 1997 to 2011 
indicating density-dependent effects on growth. How- 
ever, these surface-trawl-caught juvenile salmon were 
the length of the chum salmon in our study during the 
early juvenile stage and may not represent processes 
affecting growth later in life while chum salmon in the 
GOA. 
Pink salmon abundance consistently influenced the 
immature growth of both populations of chum salmon, 
except in the 1 st immature year of Quilcene River chum 
salmon. This finding was consistent with that of pre- 
vious studies of the influence of pink salmon on the 
growth of chum salmon (Ivankov and Andreyev, 1971; 
Salo, 1991; Bugaev et al., 2001; Kaeriyama et al., 2007; 
Agler et al., 2013). This observation was not surpris- 
ing because pink salmon are the most abundant North 
American species of Pacific salmon (Eggers et al. 1 ). 
However, chum salmon mature at multiple ages within 
a brood and are likely more abundant as immature in- 
dividuals than the maturing pink salmon. Other stud- 
ies have documented the effects of pink salmon abun- 
dance on the feeding of chum salmon. In oddyears of 
higher pink salmon abundances in the ocean, chum 
salmon were observed to consume less prey (Ivankov 
and Andreyev, 1971; Salo, 1991), shift their diet to less 
