Reese et al.: Distribution and estuarine interactions between wild and hatchery Oncorhynchus keta 
447 
salmon or according to foraging behavior and abilities, 
with little negative effect (Levings et al., 1986; Murphy 
et al., 1988; Sturdevant et al., 1996; Landingham et 
al., 1998). However, the timing of food resource avail- 
ability in relation to estuarine entry of wild salmon 
or hatchery releases could affect residency time, diet, 
growth rate, predation, and survival (Hargreaves and 
LeBrasseur, 1986; Mortensen et al., 2000; Willette et 
al., 2001; Duffy and Beauchamp, 2008), and thus the 
extent and duration of potential interactions. The dif- 
ference in environmental conditions that we observed 
in Taku Inlet in 2004 compared to 2005 indicates that 
this was a likely scenario. A companion study of diet 
and energy density of wild and hatchery chum salmon 
fry in Taku Inlet and Icy Strait is currently under- 
way and should shed light on prey utilization, foraging 
behavior, and the extent to which hatchery and wild 
stocks partition food. 
Interactions between hatchery and wild salmonids are 
complex and competition may occur only at critical pe- 
riods during the life history of a cohort when resources 
are limited (Orsi et al., 2004; Ruggerone and Nielsen, 
2004). Mixed schools of wild and hatchery fry formed 
in outer Taku Inlet, which may indicate that there is a 
potential for interactions as long as the schools persist. 
Both hatchery and wild juvenile chum salmon must 
learn to integrate many factors related to habitat, prey, 
and potential competitors and predators as they enter 
marine ecosystems (Willette et al., 2001; Warburton 
2003; Armstrong et al., 2008; Duffy and Beauchamp, 
2008). Hatchery salmon may rapidly learn to feed on 
natural prey after their release, yet these naive fish also 
lack predator-recognition and -avoidance skills and may 
lag behind wild individuals in such abilities (Olla et al., 
1998). Laboratory studies conducted with chum salmon 
indicate a potential for growth of wild fry to be affected 
by the presence of hatchery fry if there is a significant 
difference in body size, as we observed in Taku Inlet. 
This research indicates that larger individuals aggres- 
sively defend food when food is patchy but school with 
smaller fish when food is distributed evenly (Olla et al., 
1998). On the other hand, we observed chum salmon fry 
in Taku Inlet before hatchery releases, and other stud- 
ies concluded that despite smaller size, prior residence 
gives wild salmon a competitive advantage because the 
hatchery fish have to develop foraging behavior and 
search images for wild prey instead of hatchery pellets 
(Huntingford and Garcia de Leaniz, 1997; O’Connor et 
al., 2000). Later wild outmigrants in Taku Inlet also 
have the opportunity to develop foraging and predator- 
avoidance behavior in the inner inlet while few hatchery 
fish are present. 
Although the focus of this article has been the po- 
tential for intraspecific interactions, the probability 
for interspecific interactions in Taku Inlet should not 
be overlooked, because these interspecific interactions 
may also occur in Taku Inlet. We captured considerable 
numbers of pink salmon fry that often co-occurred in 
similar habitats with chum salmon fry. Several studies 
have noted diet and habitat overlap between pink and 
chum salmon in their early marine life (Bailey et al., 
1975; Sturdevant et al., 1996; Moulton, 1997; Duffy et 
al., 2005) or later (Landingham et al., 1998; Ruggerone 
and Nielsen, 2004). Commercial catches of pink salmon 
in Taku Inlet have been substantial, but variable, over 
the past 30 years and abundant populations of pink 
and chum salmon have co-existed in the Taku River. 
No data on historical abundance of pink salmon fry 
exist and there is no evidence that pink salmon returns 
have declined in the Taku River during the years since 
hatchery production of chum salmon began. The inves- 
tigation of interspecific interactions, especially between 
pink and chum salmon, would be an important focus for 
future research. 
Marine survival of most other chum salmon popula- 
tions in Southeast Alaska has been stable (Orsi et al., 
2004), and therefore poor ocean conditions are not the 
likely cause of the decline of wild chum salmon in the 
Taku River. Local evidence from the early ocean phase 
in epipelagic habitat has indicated that juvenile chum 
salmon consumed only a small portion of the available 
zooplankton (Orsi et al., 2004), and feeding indices have 
remained high throughout the diel cycle and summer 
season, indicating that growth of the fish was not food 
limited at this time. During the late ocean phase, run 
timing and harvest of adult wild and hatchery stocks 
are segregated in Taku Inlet; wild stocks return in the 
fall, whereas hatchery stocks (derived from broodstocks 
of summer-run chum salmon from coastal streams near 
Juneau) return in the summer. Although it is not known 
how many hatchery fish stray into the Taku River, 
this difference in run timing of adults presumably pre- 
vents large numbers of summer-run hatchery strays 
from interbreeding with the wild fall-run (Bachen and 
Linley, 1995; Heard et al., 1995). No directed fishery 
on wild Taku River chum salmon has operated since 
the early 1990s when the decline began. Wild fall-run 
chum salmon are intercepted in an annual coho salmon 
fishery in Taku Inlet and the catch of fall-run chum 
salmon in this fishery has averaged 4100 fish per year 
since 1992. 
In summary, our results indicate that interactions 
in Taku Inlet between hatchery and wild chum salmon 
from the Taku River are possible because of the co- 
occurrence of these fish, particularly in the littoral 
habitat of the outer inlet, and the large proportion of 
early-released hatchery fry with larger body size. How- 
ever, direct indications of competitive effects on wild 
fry, such as poor condition or reduced apparent growth 
rates in the presence of abundant hatchery fry, were not 
observed in this study. Because our understanding of 
the migration patterns of wild Taku chum salmon fry 
after leaving the inlet is inferred from data collected 
from hatchery fish, research to better define the degree 
of interaction should include a program to mark wild 
fry as they leave the river. Marking wild fry in the river 
would also allow a comparison of results of interactions 
such as growth, condition, feeding, and residence dura- 
tion between wild and hatchery fry not only in the inlet 
but along their migratory corridor. 
