Transactions of the American Fisheries Society 118:284-289, 1989
Rearing of Juvenile Chinook Salmon in
Nonnatal Tributaries of the Lower
Fraser River, British Columbia
C. B. MURRAY AND M. L. ROSENAU!
Department of Fisheries and Oceans, Biological Sciences Branch
Pacific Biological Station. Nanaimo, British Columbia V9R 5K6 Canada
Abstract. —Juvenile chinook salmon Oncorhynchus tshawytscha were collected from May to June
1980 in seven nonnatal tributaries of the lower Fraser River in British Columbia, Canada. The
juveniles were collected predominantly in pools and had migrated 0.4-6.5 km up the nonnatal
tributaries to reach the rearing areas. In 1981, two of the tributaries, Nathan Creek and the Brunette
River, were sampled every 2 weeks from late February to late June. During this period, the mean
fork lengths of juvenile chinook salmon increased from 45 to 80 mm in Nathan Creek and from
44 to 68 mm in the Brunette River. The use of nonnatal rearing areas is of importance to the
survival and productivity of juvenile chinook salmon in the Fraser River.
Freshwater residence by juvenile chinook salmon Oncorhynchus tshawytscha is highly variable.
Some fish have "ocean-type" behavior in that they
migrate seaward after a period of freshwater residence ranging from a few days to a few months.
Others exhibit "stream-type" behavior in that they
remain in fresh water for a year or longer before
migrating seaward (Reimers 1973; Major et al.
1978; Healey 1983). Chinook salmon in the Fraser
River exhibit both stream-type and ocean-type life
history patterns (Fraser et al. 1982). Stocks of chinook salmon that spawn and rear in upper Fraser
River tributaries tend to produce more streamtype juveniles than those in the lower Fraser River
(Tutty and Yole 1978). The Harrison River, a large
tributary of the lower Fraser River with about 25%
of the mean annual runs of returning chinook
salmon to the Fraser River, is probably the largest
contributor of ocean-type juveniles in the whole
system (Fraser et al. 1982).
The ocean type of juvenile Fraser River chinook
salmon varies in rearing and migratory behavior.
The juveniles either migrate directly to the ocean
with no freshwater growth, rear in the estuary for
up to 60 d before moving offshore, or reside for
60-150 d in their natal streams before migrating
to the estuary or ocean (Fraser et al. 1982; Levy
and Northcote 1982). In the Nechako and Chilcotin rivers of the upper Fraser River system, migrating juvenile chinook salmon have been marked
in the main stem and then recovered upstream
from the release site and in nonnatal tributaries
1
Present address: Department of Biological Sciences,
University of Waikato, Hamilton, New Zealand.
of these rivers (Delaney et al. 1982; Russell et al.
1983). However, there has been no documentation of upstream migrations into nonnatal tributaries of the lower Fraser River. In this study, we
describe and document the use of nonnatal tributaries of the lower Fraser River by juvenile chinook salmon for rearing, and we document their
residence time, growth, and habitat distributions.
Methods
In 1980, 21 tributaries of the lower Fraser River
in the Fraser Valley were sampled in May and
June to determine the distribution and abundance
of juvenile salmonids (Figure 1). In 1981, the Brunette River and Nathan Creek were sampled every
2 weeks from early February until late June; these
two tributaries were selected for further investigation because they contained large numbers of
juvenile chinook salmon in 1980.
In both years, collections were made with an
electroshocker (Smith-Root Type VII) and a stop
net (2 m x 10 m with 0.75-cm stretch mesh).
The collection sites were chosen according to
juvenile salmonid distribution and segregated according to habitat type (pool, run, and riffle as
defined by Helm 1985). Sampling was conducted
in a representative reach (100 m in length) of each
stream. The stop net was located downstream from
each sampling habitat, and collecting continued
until no more fish were captured. Juvenile chinook salmon from each habitat were identified,
counted, anesthetized, and preserved in 10% formalin. All juveniles from each collection were
blotted dry and then weighed to the nearest 0.01
g; fork length was measured to the nearest 0.1 mm.
Differences in fork length and weight offish among
285
JUVENILE CHINOOK SALMON IN BRITISH COLUMBIA
10
20km
FIGURE I.—Streams in the Fraser River (British Columbia, Canada) drainage sampled in 1980 and 1981 for the
presence of juvenile salmonids. Circled numbers indicate streams that contained juvenile Chinook salmon. (1)
Tincan Creek (near Vancouver), (2) Brunette River, (3) Coquitlam River, (4) Scott Creek, (5) Alouette River, (6)
Kanaka Creek, (7) Whonnock Creek, (8) Silverdale Creek, (9) Lagace (Bouchier) Creek, (10) Chilqua (Thompson)
Creek, (11) Norrish (Suicide) Creek, (12) Nicomen Slough, (13) Squakum Creek, (14) Hicks Creek, (15) Salmon
River, (16) West Creek, (17) Nathan (Beaver) Creek, (18) Clayburn (Kelly) Creek, (19) Wade Creek, (20) Hope
Slough, and (21) Silverhope Creek.
rivers in 1980 and between rivers and among time
periods in 1981 were tested by either one-way
(river) or two-way (river, time) analysis of variance.
stream surveys revealed additional juveniles,
whereas upstream surveys did not. These observations indicated that juvenile chinook salmon
used these seven nonnatal tributaries for rearing
and that the collection sites were close to the most
upstream distribution of the fish.
Results
In 1980, more juvenile chinook salmon were
Juvenile chinook salmon were found in 7 of the collected from pools than from runs or riffles (Ta21 tributaries of the lower Fraser River sampled ble 1). Differences in fork length (F = 11.01, df =
in 1980 (Figure 1). No young chinook salmon with 6, 203, P < 0.01) and weight (F = 5.67, P < 0.01)
yolk sacs were collected, and there was no infor- were observed among tributaries. Juveniles colmation available from yearly (1947-1981) spawn- lected from the Nathan, West, and Brunette tribing ground surveys during probable spawning pe- utaries in early May were larger than those colriods to suggest that chinook salmon have ever lected from the other tributaries in late May and
spawned in these seven tributaries. Collection sites early June. Higher indices of total dissolved solids
with juvenile chinook salmon were located 0.4- were obtained from the Brunette, Nathan, and
6.5 km upstream from the confluence of the trib- West tributaries (Table 1), and indices of total
utaries with the Fraser River (Table 1). These sev- dissolved solids were significantly correlated with
en tributaries probably were accessible to juve- juvenile length (r = 0.87, df = 5, P < 0.05) and
niles because of their low gradients and the absence weight (r = 0.83, P < 0.05). In addition to variof barriers, such as flood control gates, bridge foot- ation in size, there was considerable variation in
ings, culverts, and waterfalls. At each site, down- fish density among tributaries (Table 1); higher
286
MURRAY AND ROSENAU
TABLE 1.—Numbers of juvenile chinook salmon collected from different habitats, stream reach characteristics,
and mean sizes of juveniles measured. Fish were collected during 1980 from sites on seven tributaries of the Fraser
River, British Columbia. Location is number of kilometers upstream from the confluence with the Fraser River;
TDS is the index of total dissolved solids; SEs are in parentheses.
Reach characteristics
Number offish
collected from
Tributary
Date
Pool
Run
Riffle
Nathan
West
Brunette
Scott
Whonnock
Squakum
Wade
Total
% of total
May8
May 9
May 12
May 21
May 29
JunS
Jun 6
245
32
226
161
26
58
25
773
66
86
18
39
10
15
55
10
233
20
73
12
30
5
6
30
2
158
14
Water
MaxitemperWetted mum
area
density TDS
aturc Loca(m2) (fish/m2) 0«s/cm) (°Q tion
594
490
1,354
540
767
990
620
5,355
0.680
0.126
0.217
0.326
0.061
0.144
0.060
199.3
149.0
161.7
15.2
13.6
19.2
18.4
10.5
10.1
14.9
12.4
11.1
12.2
9.2
6.5
2.1
4.1
6.3
0.5
4.5
0.4
Fish measurements
N
Fork
length
(mm)
40
25
40
40
25
25
15
52.8(0.49)
54.4(1.72)
54.2(0.97)
47.7(1.00)
47.1(1.67)
49.9(0.92)
45.2(0.90)
Wet
weight
(g)
1.88(0.06)
2.16(0.20)
2.14(0.14)
1.51(0.14)
1.24(0.16)
1.71(0.12)
1.30(0.09)
densities occurred in Nathan and Scott creeks and migrations (upstream, downstream, or both) that
in the Brunette River than in the other tributaries. are genetically and environmentally controlled
In 1981, sampling was limited to the Brunette (Kelso et al. 1981). Most newly emerged chinook
River and Nathan Creek. Juvenile chinook salm- salmon are carried downstream for several days
on were collected from early April to late June in and then either develop residence behavior, mithe Brunette River and from late March to early grate back upstream, or actively continue the
June in Nathan Creek (Table 2). The first juveniles downstream migration to the estuary (Lister and
collected in each stream measured 43.6-44.7 mm Genoe 1970; Reimers 1973; Fraser et al. 1982;
fork length and had a streamlined body shape with Anonymous 1987). Healey (1980) found that many
no visible or residual yolk. This suggests that they young chinook salmon collected in the Nanaimo
were not newly emerged. Sampling continued in River estuary between March and April were new
Nathan Creek from early June to late September emergents with visible yolk. The first juveniles
and produced no juvenile or adult chinook salm- collected in Nathan Creek and Brunette River were
on. In each sampling period, water temperature past the yolk-sac stage. A survey of the lower Frawas higher in the Brunette River than in Nathan ser River (Schubert 1982) and extensive yearly
Creek. In both tributaries, juvenile chinook showed surveys of spawning grounds conducted on foot
significant increases in fork length (F = 1,011.6, by fisheries officers during probable chinook salmdf = 6, 231, P < 0.01) and weight (F = 240.8, P on spawning times (Hancock and Marshall 1985a,
< 0.01) over the sampling period, but the juve- 1985b, 1985c) revealed no chinook salmon
niles from Nathan Creek were consistently longer spawning in the seven tributaries where we found
(F = 986.3, P < 0.01) and heavier (F = 130.2, P juveniles. This suggests that habitat requirements
< 0.01) than those collected from the Brunette do not restrict juveniles to their natal streams and
River. In both tributaries, the juveniles were found that the absence of spawners does not necessarily
predominantly in pools. In 1981, densities of ju- indicate an absence of appropriate habitat.
venile chinook salmon were usually higher in the
Our findings and those of others suggest that the
Brunette River than in Nathan Creek. However, dispersal and migratory patterns of young chinook
densities within each stream were dissimilar be- salmon increase the use of available rearing areas
tween years. In early May 1980, the numbers of (Chapman 1966; Reimers 1973; Fraser etal. 1982;
juveniles collected from Nathan Creek and the Levy and Northcote 1982). The method of coloBrunette River were 404 and 295, respectively, nization is not known, but in a large system like
and in early May 1981, they were 16 and 210, the Fraser River and its tributaries, a passive
respectively.
downstream migration over several days during a
spring freshet could result in considerable downDiscussion
stream displacement. Juvenile chinook salmon are
Movements of young salmonids from spawning territorial (Chapman and Bjornn 1969), and terareas to rearing areas may consist of complex local ritorial interactions among and within salmonid
287
JUVENILE CHINOOK SALMON IN BRITISH COLUMBIA
TABLE 2.—Habitat characteristics, number, and mean (SE) measurements of juvenile Chinook salmon collected
during 1981 in the Brunette River and Nathan Creek, British Columbia, Canada. Sampling locations are the same
as in Table 1. W is the number of juvenile Chinook salmon measured from each stream.
Number offish
collected from
Tributary
Date
Pool
Run
Riffle
Wetted
area
(m 2 )
Maximum
density
(fish/m2)
Water
temperature
(°C)
Fish measurements
N
Fork
length
(mm)
Wet
weight
(g)
Nathan
Brunette
Feb22
Fcb23
0
0
0
0
0
0
502
1,315
6.5
7.0
Nathan
Brunette
Mar 10
Mar 11
0
0
0
0
0
0
545
1,340
6.5
7.5
Nathan
Brunette
Mar 23
Mar 24
9
0
2
0
1
0
554
1.345
0.022
7.5
8.5
12
44.7(0.99)
1.10(0.08)
Nathan
Brunette
Apr 6
Apr?
9
1
0
0
2
0
607
L375
0.018
8.0
9.5
11
1
51.6(0.65)
43.6
1.75(0.07)
0.75
Nathan
Brunette
Apr 21
Apr 22
15
382
16
160
34
54
557
1,340
0.117
0.445
9.0
10.0
40
40
52.2(0.45)
41.6(0.29)
1.82(0.05)
0.80(0.02)
Nathan
Brunette
May 3
May 4
1
154
8
48
7
8
564
1,352
0.028
0.155
9.0
13.0
16
40
58.8(1.24)
43.4(0.68)
2.63(0.18)
1.03(0.07)
Nathan
Brunette
May 22
May 23
11
22
3
2
3
1
600
1,365
0.028
0.018
11.0
14.0
17
25
70.0(1.18)
44.9(0.96)
4.79(0.24)
1.26(0.10)
Nathan
Brunette
Jun 8
Jun9
8
26
1
0
0
0
582
1.345
0.015
0.019
12.0
13.5
9
26
80.5(1.55)
68.1(1.13)
6.65(0.72)
4.39(0.19)
Nathan
Brunette
Total number
offish
% of total
Jun 29
Jun 30
0
0
0
1
0
0
589
1.360
12.0
13.5
1
66.3
4.28
638
64
241
24
110
11
species cause downstream displacement of subordinate fish (Stein et al. 1972). However, dispersal to other rearing areas implies that the juveniles must imprint on their natal stream as
alevins or emergents, not as smolts (Cooper and
Hirsch 1982; Rehnberg et al. 1985).
High tides coupled with high water flows in the
main-stem Fraser River during spring freshets
cause flows to stop or reverse in those lower tributaries that lack flood control systems. Juvenile
chinook salmon displaced downstream and carried into the lower reaches of these tributaries could
then migrate upstream and develop residency behavior. This is similar to colonization of tidal
channels by young chinook salmon in the Fraser
River estuary (Levy and Northcote 1982). Upstream migrations of these fish after initial downstream displacement have been observed in the
Nechako River (Russell et al. 1983). Tributaries
of the lower Fraser River tend to be less turbid
than the main stem (Cooper 1965; Servizi and
Martens 1987). Feeding success (reaction distance, capture rate, and percentage of prey ingested) of juvenile coho salmon O. kisutch decreases with increased turbidity (Berg and
Northcote 1985), and young coho salmon reared
in turbid water have reduced growth rates (Grouse
et al. 1981). Therefore, those young chinook salmon that enter nonnatal tributaries of the lower Fraser River may be able to maximize their growth
and survival. Small tributaries are generally more
productive than large rivers (Mundie 1969), and
the upstream migrations of up to 6.5 km suggest
that these areas have productive rearing habitats.
Levels of productivity also vary among streams,
and differences in productivity could account for
some of the differences in juvenile size we observed among streams. The larger size in spite of
lower rearing temperatures and the stable abundance of juvenile chinook salmon in Nathan Creek
suggest that juveniles rear there for a long period;
conversely, the smaller size at higher rearing temperatures and the rapid increases and decreases in
abundance over time suggest a short rearing period for juveniles in the Brunette River. Colonization of tributaries by chinook salmon stocks with
differences in initial egg size (Beacham and Murray 1989) could also produce differences in juvenile size among streams.
Growth of young chinook salmon rearing in
288
MURRAY AND ROSENAU
various habitats and from many different stocks
in the Pacific Northwest is remarkably consistent.
Chinook salmon rearing in estuaries in southern
British Columbia from early April to late June
increase in fork length from 33 to 80 mm (Kask
and Parker 1972; Healey 1980; Levy and Northcote 1982). Fish that remain in their natal streams
increase from 37 to 83 mm fork length before
migrating to the ocean in late July (Lister and
Genoe 1970; Reimers 1973; Delaney et al. 1982;
Russell et al. 1983; Anonymous 1987). Our finding that young chinook salmon increased in fork
length from 42 to 80 mm suggests that growth in
nonnatal tributaries is similiar to growth in natal
streams and estuaries.
Levy and Northcote (1982) reported an average
density of 0.18 juveniles/m 2 in the Fraser River
estuary. Rearing densities in our study were within
this range and were considerably higher for the
Brunette River. This suggests that the nonnatal
tributaries of the Fraser River are important rearing areas for juvenile chinook salmon and that
further research is needed to assess methods of
colonization, survival, carrying capacity, and the
origin of juveniles that use these tributaries.
Acknowledgments
The extensive field sampling necessary for this
project was accomplished with the help of Sam
Bowman, Jim Kristmanson, Wally Osterman, and
Lynn Yamanaka. Wally Barner assisted in the data
analysis. T. D. Beacham, J. H. Mundie, and W.
R. Meehan provided helpful suggestions for improvements to the manuscript. We thank J. D.
McPhail for supporting the study through his grant
from the Natural Sciences and Engineering Research Council of Canada (grant A3451).
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Accepted March 3, 1989