436 
Fishery Bulletin 107(4) 
2006). Beach gradient was 9-14% and substrate was 
predominantly gravel <5 cm. Three beaches were seined 
in the inner inlet and two in the outer inlet (Fig. 2). 
All five beach seine sites were sampled during daylight 
for a minimum of three times per week. At each beach 
seine site, sea surface temperature was measured with 
a thermometer and a water sample was collected to 
determine salinity. 
We sampled neritic habitat with a two-boat Kodiak 
trawl at night (Moulton, 1997; Mortensen et al., 2000). 
The 6-m widexl5-m longx3-m deep surface trawl (3- 
mm codend mesh) was towed at the surface at 2 knots, 
40-100 m offshore, parallel to the shoreline and at a 
bottom depth of 10-20 m. We trawled two nights per 
week at two sites in the outer inlet and two in the in- 
ner inlet (Fig. 2; 8 samples per week). Each tow lasted 
10 minutes. At each trawl site, a temperature and sa- 
linity profile was taken with a Seabird SBE-19 Seacat 
conductivity-salinity-depth (CTD) profiler (Sea-Bird 
Electronics, Bellevue, WA). 
Fish from both beach seine and trawl sets were pro- 
cessed in the same manner and fish treatment followed 
a protocol approved by the University of Alaska Fair- 
banks Animal Care and Use Committee (IACUC no. OS- 
19). All captured fish were anesthetized with tricaine 
methanesulfonate (MS-222), identified to species, and 
counted; nontarget species were released after identi- 
fication. A maximum of 60 chum salmon per set was 
euthanized with excess MS-222 and either preserved 
in 10% formaldehyde-seawater solution or frozen for 
subsequent laboratory analysis. Preserved fry were 
transferred to 50% isopropyl to maintain the integrity 
of the otolith. 
Laboratory processing 
Each preserved or frozen fish was weighed to the near- 
est 1.0 mg wet weight (wt), and measured to the nearest 
1.0 mm fork length (FL). Otoliths were removed and fry 
were identified by origin from the presence and type of 
thermal marks. Each year DIPAC placed a unique ther- 
mal mark on fry released near Taku Inlet: one mark for 
Gastineau Channel early fry, one for Gastineau Channel 
late fry, and one for Limestone Inlet fry(Fig. 2). Early 
and late hatchery fry were released from Limestone 
Inlet in both years but the two groups were given the 
same thermal mark. All fry caught from Limestone Inlet 
releases before release of the late hatchery fry were 
assumed to be early hatchery. All fry without thermal 
marks were assumed to be wild. Inferences about the 
distribution of late hatchery fry from Limestone Inlet 
after they were released were based on Gastineau Chan- 
nel late -hatchery-fry data. 
Data analysis 
We analyzed data from 2004 and 2005 separately. Sam- 
pling sites were pooled by littoral or neritic habitat for 
inner or outer inlet locations. The inner inlet sites were 
closest to the mouth of the river (the source of wild fish) 
and the outer inlet sites were closer to the hatchery 
release sites (Fig. 2), and therefore there was an a priori 
expectation that hatchery fry would be more abundant 
in the outer inlet. The inner and outer inlets were strati- 
fied because sea surface temperature and salinity were 
noticeably higher in the outer inlet location and the 
probability of encountering hatchery fry was greater in 
the outer inlet. Data on early fry from both hatchery 
release sites were pooled for analysis for two reasons: 
first, early hatchery fry from Gastineau Channel and 
Limestone Inlet were released at almost the same time 
and were similar in size; and second, the fry from both 
release sites were commonly found on both the east and 
west sides of the inlet (Fig. 2). We conducted three types 
of analyses: 1) spatial and temporal analyses to compare 
the abundances of wild and hatchery chum salmon fry; 
2) spatial and temporal analyses to contrast the body 
sizes of hatchery and wild chum salmon fry; and 3) 
analyses to correlate the distribution and size of wild 
chum fry with hatchery fry distribution, sea surface 
temperature, and salinity. 
Spatial and temporal distribution of relative abundance 
Total catch of chum salmon for each set (seine or trawl) 
was apportioned by hatchery origin or wild origin 
according to the proportion of thermally marked fry in 
the sample. We calculated CPUE of wild and hatchery 
salmon separately as the mean number of chum salmon 
captured per set by week in the inner or outer inlet loca- 
tions (Fig. 2). We plotted CPUE as an indicator of fry 
abundance. The proportions of wild and hatchery fry in 
the catch were calculated by week through the season 
and plotted separately by habitat and location. We could 
not determine when individual wild fry entered the estu- 
ary, but hatchery fry were assumed to have resided in 
the area since time of release. 
Spatial and temporal change 
in body size of hatchery and wild salmon 
Mean fork length and weight of wild, early hatchery, and 
late hatchery chum salmon fry were plotted by week over 
the course of the emigration period by location and habi- 
tat. The change in the mean size of each fish stock over 
time was calculated as an indirect measure of apparent 
growth. Although we acknowledge that immigration, 
emigration, and size-selective mortality are confound- 
ing effects on growth, we could not account for these 
changing processes. We determined apparent growth 
rate using the slope of the regression of fork length on 
date caught (day of the year). Fork length of fry of all 
origins was plotted into four histograms per year by 
location and habitat. Differences in length among loca- 
tion (inner, outer) and habitat type (littoral, neritic) for 
each year were analyzed with a one-way analysis of 
variance (ANOVA) for wild fry. The ANOVA compared 
length of wild fry by location and habitat. Fork length 
of early hatchery fry was analyzed by using the same 
ANOVA procedure. We used t-tests to examine length 
