THE FOOD HABITS, GROWTH AND EMIGRATiON
or JUVENILE cemoox SALMON. (encoeemcnus
TSHAWYTSCHA) FROM A STREAM 4 POND- ENVIRONMENT ,

Thesis for the Degree of ‘M. S.
MICHIGAN STATE UNIVERSITY
JON JOSEPH LAUER
'1969

 

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ABSTRACT
THE FOOD HABITS, GROMTH AND EMIGRATION
OF JUVENILE CHINCOK SALMON (ONCOREYNCHUS
TSHAWYTSCEA) FROM A STREAM-POND EN? RONMENT

By

Jon Joseph Lauer

Chinook salmon Juveniles (Oncorhynchus tshawytscha)
were studied to determine the food habits, growth and effect
of size on emigration from a stream-pond environment. The
chinook salmon studied had failed to emigrate from a tribu-
tary of the Thunder Bay River (Michigan) after their release
on 12 May, 1968.

Comparisons of drift organism samples and stomach
contents for six sampling periods from 12 June to 26 July
showed that the Chinook preferred cladocerans, midge larvae
and midge pupae, each 54.65, 19.73 and 18.7% of the total
diet by number respectively. Midge adults and collembolans
were also preferred, but constituted a minor portion of the
diets. Copepods and tubificid worms were present in the
drift in large numbers, but were seldom present in the diets.
Piscivorous food habits were observed only in a few individ-
uals over 85 mm fork length. The possibility of major com-
petition with forage fish species for food is discussed.

Growth appeared to be rapid. A rate of 18 mm/month
was determined for the months of May, June and July.

The observed emigration of the chinook salmon

juveniles is believed to have been forced by intra-specific

. majl‘iu‘il‘n: nil.£

Jon Joseph Lauer

competition for food and space. No relationship between
size and emigration timing was observed. The study was
terminated when low dissolved oxygen caused mass chinook

salmon mortalities.

THE FOOD HABITS, GROWTH AND ENIGHATION
0F JUVENILE CHINOOK SALMON (ONCOQHYNCHUS

-
—_

TSHAWYTSCEA) FROM A STREAM—POND ENVIRONMENT

 

By

Jon Joseph Lauer

A THESIS
Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of
I'v‘IASTFJ-i OF SCIENCE
Department of Fisheries and Wildlife

1969

(01"
A)"

ACKNONLEDGEMENTS

I would like to express sincere appreciation to
Dr. Howard E. Johnson under whose guidance this study was
made. Appreciation is also expressed to Dr. Eugene w.
Roelofs for the advice and suggestions he gave, and to
Dr. T. Wayne Porter for his help with the identification
of some invertebrates.

I am deeply indebted to a fellow graduate student,
Thomas E. Nears, for all the time and assistance he gave
me, and to my wife, Carol, for reviewing and typing my
paper. I also wish to express thanks to Robert Drummond,
Dean Eyman, Richard Noreau and Wilbert C. Wagner for the
information and assistance they gave me.

I am.gratefu1 for the financial assistance from
the Agricultural EXperiment Station, Michigan State
University, and for the cooperation of Alpena Community
College, especially from its president, Jack Petoskey,

all of which allowed me to work on the project.

11

INTRODUCTION . . .

TABLE OE CONTENTS

0 O O O O O O O O O O O O O O

DES CHI PTI ON 0;? STUDY AREA 0 O O O O 0 O O O O O O O 0

Physical Features

Temperature Measurements. . . . . . . . . . . . .

Flow Measurements

Chemical Measurements . . . . . . . . . . . ... .

Biological Life

GROWTH AND MIGRATION

Growth. . . . .

Emigration. . .

Population Estimates. . . . . . . . . . . . . . .

Discussion. . .

FOOD HABITS. . . .

Analysis of Stomach

Selectivity . .

Piscivorous feeding

Competition . .

Discussion. . .

Contents and Drift Organisms.

SUMMARY AND RECOMMENDATION" FOR MANAGEMENT . . . . .

LITERATURE CITED .

iii

PAGE

\J «a -: e- e-

10
13
15
17
18
2a

37

37
40

an
#4
45
52
54

 

In! .> u. ‘— 1 I, I n V“ .F «I 1|...Il

TABLE
1.

LIST O“1 TABLES

PAGE

L

Diurnal limnological measurements for the

study pond on 2 July and 26 July, 1968.

The measurements for 2 July are listed

above the measurements for 26 July . . . . . . 9

Tish species collected from the study pond
during June, July, and August 1968 listed
in order of abundance. . . . . . . . . . . . . 12

Numbers of chinook salmon collected,
measured and preserved for stomach analysis. . 14

Population estimates for chinook salmon,
northern redbelly dace and creek chubs in
the study pond . . . . . . . . . . . . . . . . 19

Number of fish, average total length and

length ranges of eleven species of fish

collected from the study pond after poison-

ing with rotenone on 16 August . . . . . . . . 21

Dissolved oxygen concentrations in the
study pond during periods of observed
chinook salmon stress. . . . . . . . . . . . . 23

The mean numbers of eight food organisms

consumed per fish for six sampling periods,

and the percentage of each food organism

in the total diet. . . . . . . . . . . . . . . 39

Dates and times of chinook salmon stomach
sample and drift organism sample comparison. . 41

iv

FIGURE
1.
2.

LIST OF FIGURES

The location of the study pond on
Fletcher Creek (Sec. 16, T 31 N R
8 E Mich. b1) 0 O O O O O O O O I O O O 0

Daily maximum and minimum water tempera-
tures in the study pond, and maximum air
temperatures (recorded at Phelps Colins
Field, Alpena Michigan, by the U.S.
Weather Bureau.) Maximum water and air
temperatures are represented by dots;
minimum water temperatures are repre-
sented by x's. . . . . . . . . . . . . .

Flow measurements for the study pond . .

The mean growth rate of the study pond
chinook salmon compared to the sizes of
the individual emigrants (indicated by
x's). The size ranges of the study pond
salmon are indicated for each collection

Electivity indices for eight food items
consumed by 78 Juvenile chinook salmon

collected on sampling periods 1 (12 June),

2 (18 June), 3 (28 June), 4 (2 July), 5

(9 July) and 6 (16 July) . . . . . . . . .

l6

43

INTRODUCTION

In 1967 the chinook salmon (Oncorhynchus tshawytscha)
was reintroduced into the Great Lakes region (Tody, 1967).
Prior attempts to establish the species had met with only
temporary success (Hubbs and Lagler, 1958).

Successful establishment of the chinook salmon in
the Great Lakes will require sound knowledge of the factors
that affect its survival. The chinook salmon has been
studied extensively in its native environment on the Pacific
Coast. However, significant differences probably exist
between the two environments that would affect management
of the species.

The life history phase that is most important for
chinook salmon management is the freshwater1 phase, prior
to emigration. At this time, mortalities in the salmon are
highest (Butter, 190A). Thus, the more time Juveniles Spend
in freshwater, the smaller the adult return will be.

Studies by French and Wahle (1959), Mattson (1962,
1963) and Biemers and Loeffel (1967) discount a concept long

held by biologists concerning emigration. The concept is

 

1"Freshwater" in this paper means waters inland from the
oceans or Great Lakes.

that juveniles from parent stocks which typically enter
freshwater as adults in the spring (spring run chinook
salmon) or the fall (fall run chinook salmon) emigrate at
one year and three months of age, respectively. Rather,
they found that Juveniles from both spring and fall runs
spend from a few months to over a year in freshwater.

Variable timing of emigration has also been observed
in hatchery stocks of steelhead trout (Salmo gairdnerii)
(Wagner, 1968). Wagner (1968) states that individual fish
released en mass; from a hatchery will not all be in a
migratory disposition, and that some will take up residency
in the stream for varying periods of time. Chinook salmon
probably display similar behavior.

Both fish that fail to emigrate at their "normal
expected emigration time" (residuals) and fish that are
released prior to that time, are affected similarly by the
environment. Available food, predators, competitors, water
temperatures and dissolved oxygen play key roles in deter-
mining survival.

Growth rate also is important because it has an
association with emigration. Reimers and Loeffel (1967)
state that the larger chinook salmon Juveniles appear to
emigrate earliest.

To determine the effect of size on emigration, as
well as the food habits and growth rate of fall run chinook
salmon Juveniles in Michigan, I studied a population of

chinook salmon in Fletcher Creek, a tributary to the Thunder

Bay River. These salmon were hatched and reared to finger-
1ing size by the Alpena Community College from eyed eggs
obtained from a race selectively bred by Dr. L.R. Donaldson
at the University of Washington (Donaldson and Menasveta,
1961). The plant consisted of 65,000 fingerlings marked
with a right pelvic fin clip, and released 158 days after
the last eggs had hatched. The population stUdied was
largely a residual stock which had remained in the stream
after their release on 12 May, 1968. The study period,
from 12 June to 26 July, was terminated prematurely due

to the nearly complete mortality of young salmon caused by

low dissolved oxygen conditions in the stream.

DESCRIPTION 0? STUDY AREA

Physical Features

 

The study area was the lower end of Fletcher Creek
Just above the point the creek empties into the Ninth Street
Dam reservoir located on the Thunder Bay River at Alpena
Michigan (Figure 1). The creek forms a small pond (900 M2,
maximum depth 1.3 M) which has deep fast flowing water over
a gravel bottom at the upper end, graduating to shallow,
slow flowing water over a muck bottom with dense aquatic
vegetation at the lower end. The creek enters the study
pond via a culvert from a larger pond on the upstream side
of Long Rapids Road. The larger upper pond is shallow
(maximum depth 1 M), muck bottomed, and supports dense
growths of algae and submergent aquatic plants. A series
of intermittent springs in Fletcher Creek and the upper
pond provide the main flow of water to the study pond.
During periods of low rainfall the stream flow is greatly

reduced.

Temperature Measurements
Temperatures in the pond were measured with a
Taylor Maximum-Minimum thermometer that was suspended in
the main current. Daily temperatures fluctuated an average
of 7.3 C during the study period (Figure 2). The daily high

and low water temperatures were fairly stable except for a

cool period from 22-28 June and for a warm period 14-22

4

 

Fletcher Creek

‘1

Parker Street

  
   
   
     

Upper Pond

Long Rapids Road

Study Pond
Scale: 1-mm = 2.2 M

Ninth Street Dam
Reservoir
(Thunder Bay River)

FIGURE 1.--The location of the study pond on Fletcher Creek
(Sec. 16, T 31 N R 8 E Mich. M).

30'

20 '

 

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15

25-

20 -

O mwda>wnjwzsma

10 -

f <
5%

I n n A l l l l l
15 20 25 3O 5 10 15 20 25
June July

Date

EFIGURE 2.--Daily maximum and minimum water temperatures in
'the study pond, and maximum air temperatures (recorded at
Iflnelps Colins Field, Alpena Michigan, by the U.S. Weather
fhlreau.) Maximum water and air temperatures are represented
lxy dots; minimum water temperatures are represented by x's.

 

July. The changes in water temperature followed the same
trend as the changes in maximum daily air temperature

(Figure 2).

Flow Measurements

Nine measurements of Fletcher Creek discharge at
the study pond were made during the study period according
to the float method as described by Welch (1948) (Figure 3).
I observed the increase and decrease of the flow to be
dependent on rainfall, which was the main source of water
for the springs that feed Fletcher Creek. The low flows of
mid-July corresponded to the "drying up" of several springs
in Fletcher Creek. On 20 July surface discharge from the
study pond ceased and only subsurface discharge was observed

after that date.

Chemical Measurements

On 2 and 26 July, diurnal measurements of dissolved
oxygen, total alkalinity, and pH were made on Fletcher Creek
at the study pond (Table 1). Single measurements of hardness
were made on 9 and 26 July. The Standard Winkler Method
(Alsterberg modification, Hach, 1967) was used to determine
dissolved oxygen. Standard titration methods as outlined by
Hach (1967) were used to determine total alkalinity (phenol-
phthalein and brom cresol green-methyl red indicators - N/50
sulfuric acid titrant) and hardness (ManVerR indicator and
TitraVerR titrant). A Beckman pH meter (model H) was used

to measure pH.

.22

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.18

.16

"1.1

.14

.12

ElOt“

.10

sec
.06
.04

.02

.00

FIGURE 3.

 

20 25 30 5 10 15 20 25
June July
DATE
--Flow measurements for the study pond.

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10

The limnology is characteristic of a body of water
that supports abundant plant life (Table 1). The dissolved
oxygen concentrations were highest in the late afternoon
and lowest in the early morning. This oxygen pulse reflects
the daily photosynthetic cycle. The diurnal uptake of carbon
dioxide by the plants during photosynthesis caused the total
alkalinity in the pond to decrease and the pH to increase
from non-photosynthesis levels (Reid, 1960). From the total
alkalinity and pH measurements the pond water was classified

as hard and slightly alkaline (Sawyer, 1960; Reid, 1961).

Biological Life

The major species of filamentous algae collected
throughout the study pond were Spirogyra spp., Oscillatoria
spp., Cladophora spp. and Eormidium spp. In the lower end
of the pond, the aquatic plants Potamggeton_pectinatus and

.2. Richardsonii were abundant on the muck and sand muck

 

bottom. Typha sp., Scirpus sp., Sparganium sp., and Solanum
sp. comprised the dominant emergent vegetation.

The most common invertebrates in the pond were:
freshwater sponges (Porifera); aquatic snails (Gastropoda);
fingernail clams (Sphaeriidae); leeches (Hirudinea); tubi-
fix worms (Tubificidae); copepods (Canthocamptidae and
Cyclopddae); cladocera (Eurygercus lamellatus); ostracods
(Ostracoda); crayfish (Astacidae): midge larvae and pupae
(Tendipedidae and Helidae): damselfly naiads (Odonata);
mayfly naiads (Ephemeroptera); water boatmen (Corixidae);

and Collembola.

11

The fish Species collected from the pond are listed
in Table 2 in their order of abundance. The abundance was
determined from observations, and from seining and poisoning
collections described later.

The entire study area is a waterfowl sanctuary.
Ducks were often observed feeding in both of the ponds on

Fletcher Creek.

TABLE 2.--Fish Species collected from the study pond during

June, July, and August 1968 listed in order 2: abundance.

 

 

Chinook Salmon
Northern Redbelly Dace
Creek Chub

Brook Stickleback
Central Mudminnow
Bowfin

White Sucker
Darters

Banded Killifish
Tadpole Madtom
Northern Pike

Oncorhynchus tschawytscha1

Chrosomus eos1

Semotilus atromaculatus2
Eucalia inconstans2
Umbra llgi3

Amia calva3

 

Catostomus commersoni3
Etheostoma spp.“

Fundulus digphanusu
4

Moturus gyrinus

Esox lucius

 

 

Carp Cyprinus carpiol+
Yellow Bullhead Ictalurus natalis
Burbot Lgta'lotau

1

Over 500 collected.
Less than 500 collected.
3Less than 100 collected.

Less than 20 collected.

GROWTH AND MIGRATION

To study the growth of Juvenile chinook salmon in
the study pond and the relationship of size to emigration,
both emigrating and residual chinook salmon were collected.

For growth determinations, the residual salmon were
collected by seine hauls from several locations in the study
pond for each sampling period (Table 3). The fish were
anesthetized with MS 222 (Tricane Methanesulfonate), and
were measured (fork and total length) to the nearest milli-
meter. A random sample of the chinook salmon from each
collection was preserved in 10% Formalin for stomach analy-
sis, and the remainder of the fish were returned to the
pond. The first two collections were exceptions to this
procedure in that a random sample was collected, killed in
10% Formalin, and then measured shortly after death.

The collection of emigrating chinook salmon was
limited due to restrictions on equipment and material. An
improvised fyke net was fished intermittently at the pond
outlet from 22 June to 10 July. The net was set to block
the width of the outlet channel. However, effectiveness of
the net in collecting and retaining fish was impaired by
insufficient water flow and by constant clogging with fila-
mentous algae.

To improve collection of emigrants, and to determine
possible immigration of salmon from upstream, basket-like

wire traps of i-inch mesh were placed at the inlet and outlet

13

14

TABLE 3.--Numbers g; chinook salmon collected, measured
and preserved for stomach analysis.

 

Number
Sampling Seined and Number
Dates Measured Preserved
12 June 44 44
18 June 12 12
28 June 149 14
3 July 13 13
9 July 104 10
16 July 24 6
20 July 32 22

Totals 378 121

 

15

of the pond. All of the water entering or leaving the

pond flowed through the traps. Both traps were used con-
tinuously from 12 to 20 July. Water ceased to flow through
the outlet trap on 20 July. Other fish species were collected
in the traps incidental to the collection of the salmon.

All of the emigrating salmon collected in the traps
and the net were released downstream with the exception of
13 individuals collected after 3 July which were marked by
clipping the tip of the caudal fin and released in the upper
end of the study pond. None of the 13 marked fish were
recaptured.

To make growth and size comparisons with other
studies, conversion factors for standard, fork, and total
length were determined. These relationships are as follows:
fork length = 0.82 total length; fork length = 1.13 standard
length. The conversion factor for fork to standard length
was calculated from measurements made on 49 preserved speci-
mens selected from all sampling periods to represent the
complete range of sizes for those periods. All chinook
salmon length measurements given in this paper will be in

millimeters fork length unless otherwise specified.

Growth

The ranges and mean lengths of chinook salmon col-
lected on each of seven sampling dates in June and July are
shown in Figure 4. The size of the fingerlings at the time

of release on 12 May was determined by measuring a sample of

l6

 

 

 

 

 

 

 

 

 

120
r .,
110 -
X
F 100 L 'J
O 'L x
R «I-
K 90 . "
L n
E 80 . " 5
N
G x i s
T 70 -
H 8
fl
T J. X A
50 - x
A
40 -
30 I 1 1 L l n
15 1 15 1 15 31
May June July
DATE

FIGURE 4.--The mean growth rate of the study pond chinook
salmon compared to the sizes of the individual emigrants
(indicated by x!s). The size ranges of the study pond
salmon are indicated for each collection.

17

50 fish that were collected and frozen Just prior to the
release. The fluctuations in ranges on 18 June and 3 July
were probably caused by small sample sizes (Figure 4). The
average rate of growth of the salmon during the study period

was 18 mm per month.

Emigration

A total of 35 emigrants were collected in the outlet
trap and 4 immigrants in the inlet trap. Apparently the
4 immigrants had previously moved upstream and were in the
process of emigration at the time of their capture. A com-
parison of the sizes of the individual emigrants and the
average size of the chinook salmon remaining in the pond
showed that there was not a relationship between size and
emigration (Figure 4).

The possibility of smoltification and aggressive
behavior being associated with emigration was also considered.
I determined smoltification as the loss of parr marks and
increased silveriness. There appeared to be no relationship
between smoltification and either emigration or size. Chinook
salmon remaining in the pond were as silvery as the emigrants.
However, it seemed that the degree of smoltification in the
salmon increased from the time the study began until the end
of June when it began to decrease.

No characteristic aggressive behavior such as nipping
was observed, but the larger chinook salmon occupied dominant

positions behind rocks in the water current. The northern

18

redbelly dace and creek chubs occupied the positions farthest
downstream.

A minnow trap was placed beside the improvised fyke
net, blocking the outlet, in an effort to collect any salmon
attempting to re-enter the pond after passing through the
outlet, but none were collected.

Junge and Phinney (1963) state that emigration may
be blocked by temperature gradients. To determine if a
temperature barrier existed below the pond outlet, a ther-
mistor thermometer was used on 24 June to check water temp-
eratures for 300 M south from the outlet until a water depth
of 2-3 M was reached. The pond outlet temperature of 16.6 C
was traced the entire distance. I concluded that a tempera-
ture barrier was not holding the chinook salmon in the pond,
and that they could have emigrated as was expected after

release.

Population Estimates

To estimate migration and the number of chinook
salmon in the study pond, Petersen mark and recapture popu-
lation estimates (Lagler, 1956) were made on 29 June and 9
July (Table 4). The right pelvic fin was re-clipped for the
first population estimate. It had previously been clipped
to identify the pOpulation, but some regeneration had occurred
in nearly all individuals. The fresh clip was easily iden-
tified in all the fish marked. However, for the second

estimate on 9 July, the "freshness" of the clip was not as

19

TABLE 4.--Population estimates for chinook salmon, northern

 

redbelly dace and creek chubs in the study pond.

 

 

Number
Number Becaptured/ Population
Date Species Clipped Total Catch Estimate
29 June Chinook
Salmon 135 21/185 1189
9 July Chinook
Salmon 133* 22/104 630
Northern
Redbelly
Dace 215 9/85 1141
Creek
Chub 5 1/39 195

 

v——

*The 135 chinook salmon marked on 28 June were used, less
two known emigrants.

20

easy to determine and fish that had not been re-clipped on
29 June could have been counted as re-clipped fish. This
would have caused an underestimate.

Based on observations and seining success, I
would estimate that twice as many chinook salmon were present
in the pond at the onset of the study, as there were on the
first population estimate on 29 June. Likewise, probably
one-tenth of the population of 29 June was present when
mortalities were first observed on 20 July.

Mark and recapture estimates of the northern
redbelly dace and creek chub populations were made on 9
(July with fish marked on 5 July (Table 4). The identifying
mark was an anal fin clip.

The relative abundance of different species in
the pond was determined by poisoning the pond with rotenone
on 16 August. All fish that came to the surface were col-
lected for eight hours after the poison was administered.
Few fish were found after that time. The species composition,
numbers, and average lengths (total length) are listed in
Table 5. Many of the smaller fish became trapped in the sub-
mergent vegetation and were not collected as effectively as
the larger fish. Because the creek chubs were generally
larger than the northern redbelly dace, the population esti-
mate of the former (Table 4) was similar to what was found

at poisoning, whereas the latter was not.

21

TABLE 5. --Number of fish, average total length and length
ranges of eleven species pg fish collected from the study

pon nd after poisoning with rotenone __ __

 

 

Number Average Total Total Length

Species of Fish Length (mm) Range (mm)
Northern

Redbelly

Dace 226 47.7 34-65
Creek

Chub 122 60.9 43-120
Brook

Stickleback 70 32.2 22-63
Central

Mudminnow 4 78.8 75-85
Bowfin 52 153.8 127-184
White

Sucker 43 118.2 43-163
Banded

Killifish 5 60.4 55-67
Tadpole

Madtom 12 66.6 55-82
Northern

Pike 7 231.2 222-249
Carp 12 52.3 32-85
Yellow

Bullhead 1 81.0 81.0

 

22

On 20 July mortalities associated with low dissolved
oxygen were observed. Signs of stress had been observed
earlier on 16 July. The signs of stress were: darker than
normal pigmentation; rapid opercular ventilation; gasping;
disorientated swimming at the water surface. No other fish
species in the pond demonstrated these signs of stress.

The results of dissolved oxygen measurements made
on 16 July and on seven successive days (Table 6) show that
low dissolved oxygen levels in the morning increased to
saturation or near saturation levels later in the day. The
signs of stress were apparent near or below 3 ppm dissolved
oxygen. Many mortalities were observed on 20 and 23 July
when dissolved oxygen levels were less than 2 ppm. The
chinook salmon showed the stress behavior described above,
lost equilibrium and sank to the bottom of the pond. Mor-
talities on both days occurred over the entire pond, so
probably many were not observed.

On 23 July when the water was 8% saturated with
oxygen, I netted 14 stressed salmon from the pond surface
and placed them in a tub of pond water that was aerated to
a level of 6.5 ppm (64% saturated at 17.5 C). All but two
salmon recovered from their stress symptoms in ten minutes.
This indicated that oxygen and not temperature was the
lethal factor.

The study was terminated on 26 July when seine
hauls indicated the mortality of the salmon was nearly

complete.

23

TABLE 6.--Dissolved oxygen concentrations in the study
pond during periods 2; observed chinook salmon stress.

 

Dissolved Oxygen
Date Time Temperature Oxygen Saturation
(July) (E.D.S.T.) (C) (ppm) (%)

 

16* 0800 18.0 3.6 38
16 1700 26.0 15.6 150+
17 1815 19.0 5.4 57
18* 0800 20.0 3.0 33
18* 1030 19.6 2.7 28
18 1330 20.0 6.0 65
18 2000 22.7 8.2 94
19* 0730 17.2 2.7 27
19 0930 17.0 3-7 39
19 1900 25.5 12.2 150
20** 0830 18.0 1.8 18
20** 1000 18.2 2.2 24
20** 1100 19.2 2.9 31
20 1200 20.4 3.5 38
21* 1000 18.7 2.9 31
21 1930 22.1 8.6 99
22 0830 19.0 3.2 34
23** 0800 18.0 0.8 8
23** 0930 17.8 2.5 26
23** 1100 18.3 2.3 24
23** 1200 19.0 2. 26
23 1700 19.7 7.3 78

 

«l-
Stress observed.

*5!-
Stress and mortalities observed.

24

Discussion

The length of time Juvenile salmon remain in tri-
butary streams prior to downstream migration has a signifi-
cant influence on their survival and return as adults.
Extended periods of residence in the tributary streams may
result in higher mortalities of the Juvenile salmon due
to predation, limitations of food and space and adverse
environmental conditions, such as wide fluctuations in
temperature and dissolved oxygen.

The downstream migration of salmonid Juveniles is
generally associated with the parr-smolt transformation '
which results in an active or voluntary emigration (Bagger-
man, l960a; Hoar, 1966; Wagner, 1968). Smoltification has
been defined by Hoar (1953) as the morphological, biochemical
and ethological changes associated with increased endocrine
activity and seaward migration. Baggerman (1960a) developed
a model of the smoltification process which incorporates
both the endocrine system activity and more conventional
factors associated with salmonid emigration such as stream
flows and water temperatures.

The priming factors of increasing day length and
water temperature promote changes in the endocrine balance.
Smoltification results when these changes are coordinated
with endogenous rhythms. The transformed smolt shows

increased activity and increased sensitivity to environmental

25

factors such as water temperature, light intensity, river
discharge, and meteorological conditions. These factors in
turn serve as releasers for the migratory behavior and
orientation of the smolt to its environment (Baggerman, 1960a).

With most anadromous salmonids a threshold size has
been associated with smoltification and emigration (Elson,
1957; Beimers and Loeffel, 1967; BJornn, Craddock and Corely,
1968; Vanstone and Markert, 1968; Wagner, 1968). Thus, the
larger individuals tend to emigrate earliest.

Salmonid Juveniles of hatchery origin, which are
released prior to smoltification, remain as residents in the
stream until the transformation takes place (Wagner, 1968).
Thus, a premature release of hatchery-reared salmon may
contribute to higher mortalities of the Juveniles.

Chapman (1962; 1965) and Mason and Chapman (1965)
report that aggressive behavior by dominant coho salmon
(Oncorhynchus kisutch) Juveniles is an important cause of
emigration prior to smoltification. They state that dominant
coho salmon were the larger and faster growing individuals
which occupied territories in riffles or appeared in hier-
archies in pools. The density of Juvenile coho salmon in
the streams was regulated by the aggressive territorial
behavior of these dominant individuals. Chapman (1966) feels
that competition for a limited amount of food is the basis for
the dominant behavior which serves to regulate the distribu-

tion of food available to a population. He also states that

26

there appears to be some spatial requirement independent of
food supply because some individuals will defend territories
even in the presence of an abundance of food.

It is difficult to determine if the chinook salmon
emigration from the study pond was voluntary or forced.
Certainly the feeding hierarchy in the chinook salmon observed
in the study pond could be the basis for forced emigration.
As the salmon increased in size, food and space may have
become limited. The fact that large as well as small salmon
were captured emigrating from the pond (Figure 4) does not
contradict the supposition that the emigrations were forced.
Chapman (1966) states that the dominant fast growing salmonid
may outgrow its territory even though food is more than
adequate, and may be forced to move to a more suitable location.

Density-caused dispersion may also be the reason
for the migration of chinook salmon into the upstream pond.
Chinook salmon planted in the Ocqueoc River near Millersburg,
Michigan were observed to move about 2 km upstream to a
barrier, in addition to movement downstream after their
release (Drummond, pers. comm., 1968).

On the basis of adult scale studies, larger chinook
salmon Juveniles have been reported to emigrate earlier than
the smaller individuals (Gilbert, 1914; Rich, 1922, Mattson,
1962; and Reimers and Loeffel, 1967). This is not confirmed

by comparing the size of the study pond chinook salmon

27

emigrants with the size of the individuals remaining in the
pond, nor by the idea of forced migration described by
Chapman (1962) in which large numbers of smaller salmon

would be expected to emigrate first. One possible explana-
tion is that chinook salmon Juveniles do not exhibit dominant
behavior to the degree coho salmon Juveniles do; however, this
is not verified by the work of Edmundson, Everest and Chapman
(1968) and Reimers (1968).

A more plausable explanation can be made if the
authors who state that larger chinook salmon emigrate earlier
are referring to active, voluntary emigration, which is asso-
ciated with smoltification and movement to the ocean. Forced
emigration is movement due to unfavorable conditions resulting
from the limitations of food and space. If favorable habitat
could not be found by the forced emigrants, the evidence
given by Chapman (1966) indicates that they would be elimi-
nated by predation. Only those Juveniles left in the stream
to smoltify and emigrate would survive to maturity. Since
smoltification is related to size, the larger individuals
remaining in the stream would probably be the first to emi-
grate, survive and return.

In comparisons of hatchery plantings in California,
Cope and Slater (1957) and Warner, Fry and Culver (1961)
found that chinook salmon released at a younger age returned
at a greater average size, but in fewer numbers than those

released as yearlings or near-yearlings. Warner pp 21-

28

(1961) found no differences in the returns of adult fall

or spring run chinook salmon when the Juveniles were released
as either fingerlings or yearlings. Somewhat similar results
were reported by Cope and Slater (1957).

The growth rate (18 mm/month) of the study pond
chinook salmon was greater than what Rutter (1904) reported
for Sacramento River chinook salmon (10 mm/month) of the
same age. The better growth rate of the chinook in the
study pond may reflect genetic differences in the two stocks
or more favorable environmental conditions. However,
Rutter's data were collected from the main stem of the
Sacramento River and may have included emigrants from dif-
ferent racial stocks for each sampling period. Variations
in the size of different emigrating stocks would introduce
considerable variation inthe determination of growth rate.
The approximate growth rate of 15 mm/month for chinook
salmon in the Klaskanine River, a tributary of the Columbia
River (Reimers and Loeffel, 1967), was only slightly less
than that of the study pond population. To explain differ-
ences in growth rates, environmental conditions associated
with the growth rates, such as food abundance, water temp-
eratures and dissolved oxygen levels, must be known. In
most instances, these conditions are not given in the
literature.

Controlling the growth rate of hatchery salmon may

be a means of controlling their emigration upon release.

29

The growth could be regulated so that the fish would reach
their threshold size for smoltification at the desired
release time. If necessary, artificial photoperiod regu-
lation, as described by Baggerman (1960b), could be used
to induce smoltification.

One very important factor in obtaining good adult
returns is the imprinting of Juveniles to return to their
parent stream. Imprinting in salmonids is believed to be
most rapid at the time of smoltification (Lichtenheld, 1966).
Wagner (1969) indicates that although much stronger imprints
occur during the period of smoltification, imprinting is not
limited to that time. A possible explanation is provided by
Lichtenheld (1966) who found that Juvenile steelhead trout
desmoltified if not allowed to migrate, but then resmolti-
fied after a period of time. This apparently endogenous
cycle took place without the priming factors of increasing
photoperiod and temperature. The process of imprinting is
believed to be continuous during downstream migration
(Lichtenheld, 1966; Wagner, 1969). Stream odors and physi-
cal obJects are suggested as important parameters used as
cues in the imprint process. Wagner (1969) states that
adults probably return by following the imprint stimuli in
reverse sequence.

Whether salmon are released prior to smoltification
and reside, or are a residual population that failed to emi-

grate as expected, predators, 1ow dissolved oxygen levels

30

and high water temperatures increase their mortalities.
All of these factors could be important in the selection
of a stream for stocking in Michigan.

A chinook salmon predator study was not made in
the study pond. However, it is possible that some of the
reduction in population size in the pond can be attributed
to predation. The bowfin and northern pike in the study
pond (Table 5) suggest this possibility.

Predation on Juvenile sockeye slamon (Oncorhynchus
nppnn) is reported by Foerster (1968) to be of great sig-
nificance in effecting the return of adult sockeye. He
cites several studies that give evidence of high rates of
predation on both fry and fingerling sockeye. Similarly,
Rutter (1904) states that predation on chinook salmon
Juveniles is high in their early life. The major species
reported to be predatory on chinook salmon are the squaw-
fish (Ptychocheilus oreggnense), Dolly Varden trout
(Salvelinus malma), yearling steelhead trout, yearling
coho salmon, yearling chinook salmon, and sculpin (Cottus
spp.) (Rutter, 1904; Clemens, 1934; Korn, 23 gl., 1967).

The importance of predation on chinook salmon
Juveniles in the Great Lakes tributaries can only be specu-
lated. The seasonal distribution and activities of both
predators and prey, which is of great importance in deter-
mining predation (Foerster, 1968) can be estimated. Chinook

salmon planted in streams and rivers would be subJect to

31

predation by brown trout (Salmo trutta), yearling steelhead
trout, yearling coho salmon, yearling chinook salmon, nor-
thern pike, smallmouth bass (Micropterus dolomieui), and
walleye (Stizostedion vitreum). Salmon fingerling stocked
in lakes, bays, or reservoirs would be subJect to predation
by bowfin, crappie (Pomoxis spp.), largemouth bass (Microp-
terus salmoides), smallmouth bass, northern pike, yellow
perch (Perca flavescens), and walleye.

Several factors are mentioned in the literature as
important in the reduction of predation. These factors are:
predator removal (Foerster and Ricker, 1941); increasing the
size of the planting or migration (Neave, 1953; Hunter, 1959);
increasing the size of the individual migrant salmon (Foerster,
1954; Burrows, 1963); removal of temperature barriers (Junge
and Phinney, 1963; Mihursky and Kennedy, 1967): reduction of
the water temperature (Moffett, 1949; Thompson, 1959), which
would place the migrant in an activity range that is optimum
with respect to reduced activity of the predator (Burrows,
1963).

The fate of the chinook salmon that emigrated prior
to the study is not known. Several facts do give evidence
for a potentially large loss due to predation: the chinook
salmon had a small average size at release; they were released
into a shallow impoundment containing many predators; and

they were planted about three weeks after the release of

32

100,000 coho salmon yearlings below the impoundment outlet.

The residual chinook salmon in the study pond suf-
fered mortalities due to low dissolved oxygen. Comparisons
of Figures 2 and 3 and Table 6 show that temperatures in
the pond increased as flows and early morning oxygen concen-
trations decreased in mid-July leading to the mortalities of
the salmon.

Slower, quieter waters are reported by Hutchinson
(1957) to be prone to oxygen deficit in the summer months
if they are productive of algae or aquatic plants. Noctur-
nal respiration of the plants causes the greatest deficit
in the early morning. A slight deficit was noticeable in
the diurnal dissolved oxygen cycles (Table 1). Because the
pond above the study area on Fletcher Creek (Figure 1) had
dense aquatic vegetation, and because the pond discharge
was low, nocturnal respiration of the aquatic vegetation
was the most probable cause of the low dissolved oxygen
concentrations. The situation was compounded by high water
temperatures which are inversely related to dissolved oxygen
concentrations at saturation (Hutchinson, 1957). and by a
biological oxygen demand caused by increased flow of parti-
culate matter in the water resulting from ducks feeding in
the creek.

Chapman (1939) subjected Juvenile chinook salmon to
low dissolved oxygen concentrations in closed containers and

found that levels of 2.66 ppm (25% saturated - 13.5 C)

33

distressed most individuals and produced considerable mor-
tality. This is very close to the approximate 30% saturation
and 3 ppm level I observed to initiate stress symptoms in
chinook salmon Juveniles. Chapman also found the fish to
exhibit considerable individual variation in their suscep-
tibility to low dissolved oxygen levels. The individual
salmon I found alive in the pond after the two days of
observed mortalities exhibited individual variation that
allowed them to survive normally lethal levels. Similar
individual variation is described by Fry (1957).

The sublethal effects of low dissolved oxygen are
also quite important. In work with coho salmon, Davidson
23.31. (1959) found that 903 of the salmon fed restricted
diets survived 2.0 ppm dissolved oxygen (20% saturated at
18 C) for 30 days, but suffered a 6.7% loss in weight. At
2.9 ppm (30% saturated at 18 C) and at 9.0 ppm (95% satu-
rated at 18 C) dissolved oxygen, the salmon suffered no
mortalities and gained 28.1% and 42.0% in weight respec-
tively. In another study, reduction of dissolved oxygen
levels below saturation was accompanied by a similar reduc-
tion in growth when coho salmon were fed unrestricted rations
(Herrmann, Warren, and Doudoroff, 1962). The apparent reason
is that the more food a fish consumes, the more oxygen it
requires because of the energy required by assimilation

(Doudorcff and Shumway, 1967).

34

Salmon will avoid low dissolved oxygen concentra-
tions. Whitmore, Warren, and Doudoroff (1960) found chinook
salmon Juveniles to show marked avoidance of low dissolved
oxygen, especially at higher temperatures. When the tempera-
ture was 22.8 C, they would avoid oxygen levels of 4.5 ppm
(52% saturated), but not 6.0 ppm (68% saturated). At 12.3 C,
oxygen levels of 4.5 ppm (42% saturated) were not avoided.
These data indicate the absolute oxygen concentration is
more important for respiration than the percentage satura-
tion. This position is held by Fry (1957).

Beamish (1964) found that the rate oxygen was con-
sumed in brook trout (Salvelinus fontinalis) and brown trout
increased with the temperature of water, indicating that a
temperature increase not only reduces the amount of oxygen
that can be saturated in water, but it also increases the
demand the fish has for oxygen by increased metabolism and
maintenance requirements.

It is difficult to evaluate the effects that high
water temperatures (or fluctuating temperatures as well)
had on the mortality of the chinook salmon in the study
pond. Temperatures at times that stress or mortalities were
observed were below 20 C (Table 6), well below the ultimate
lethal limit Brett (1952) set for Pacific salmon Juveniles
at 25.1 C. Temperatures near or above this lethal limit
were recorded on six days in mid-July (Figure 2) with no

observed mortalities. A plausable explanation can be made

35

from Breder's (1927) experiment with brook trout. He found
that high temperatures caused little stress when large
amounts of oxygen were present. High water temperatures in
the study pond were accompanied by high levels of dissolved
oxygen (Table 6). The time of day when most photosynthesis
in aquatic vegetation occurred would probably be during the
period of highest water temperature. This situation would
create high levels of dissolved oxygen in the pond, especially
since the water flow was low (Figure 3).

The temperature range for maximum productivity of
salmon fingerlings is given by Burrows (1963) as 10.00 C
to 15.55 C. Not only is it the preferred range, but tempera-
tures above or below it are conducive to the development of
disease in both young and adult salmon. In chinook salmon
Juveniles, food consumption, which is a determinant of
growth, increases 60% for every 5.5 C raise in temperature
from 4.5 C to 15.5 C (Burrows, 1963). Because the oxygen
demand of a fish increases with increasing food consumption
(Herrmann.at.al., 1963), a temperature increase causes a
wo-part oxygen demand. One part is caused by increased
body maintenance requirements (Beamish, 1964), and the other
part by increased assimilation requirements.

The effect that both temperature and dissolved
oxygen have on growth and survival of a fish depends on

factors such as species differences, physiological state,

36

acclimation, synergisms with pollutants and water chemistry
(Mihursky and Kennedy, 1967; Doudoroff and Shumway, 1967).
Consequently, control of environmental conditions whenever
possible can greatly increase production of salmonids

(Burrows and Combs, 1968).

FOOD HABITS

Wagner (1968) states that fish released prior to
parr-smolt transformation may not smoltify if the environ-
ment has a reduced food supply. A study was made to deter-
mine the food habits and possible feeding selectivity of
residual chinook salmon in the study pond. The residual
chinook salmon Specimens collected and preserved for the
growth studies (Table 3) were also used for the stomach
analysis.- In addition, 29 northern redbelly dace, (33-55
mm total length), 9 creek chubs, (45-82 mm total length),
and 7 brook stickleback, (38-56 mm total length), collected
and preserved with the salmon on the sampling dates listed
in Table 3, were used to determine possible competition with

the salmon for food items in the study pond.

Analysis 2; Stomach Contents and_23;§p_0rganisms

The stomachs from the esophagus to the gut were
dissected from each fish, and the contents were enumerated
according to taxonomic groups. Only those organisms in a
somewhat whole condition were ineluded in the enumeration.
I arbitrarily determined "somewhat whole condition" as:
cladocerans, copepods, and ostracods which contained body
contents in addition to a recognizable exoskeleton; midge
larvae, pupae and adults with body contents and two body
regions still intact; and all identifiable collembolans and

tubificid worms. I believe that some of the bias caused by

37

38

slow digesting food organisms (Lagler, 1956) was eliminated
using this procedure. The percentage composition of the
total combined stomach contents for each sampling period was
calculated for the salmon.

Only 8 of the 121 stomachs examined were empty or
near empty, indicating that the food supply was abundant.
Cladocerans, midge larvae and midge pupae were the maJor
food items consumed by the salmon for most sampling periods
(Table 7). All other food items were consumed in much
smaller numbers.

Feeding selectivity was determined by comparing the
abundance of specific food organisms in the salmon's diet
with the abundance of these organisms in the environment.
Drift organism samples collected with a Wisconsin plankton
net at the inlet of the pond were used for the comparisons.
The mouth of the net was held for two minutes in the fast
current with three-fourths of the net opening under the
water, and one-fourth above the surface. A two minute
sample was considered sufficient to get a representative
sample. The samples were preserved in 70% ethyl alcohol.

The drift organisms collected were analyzed in the
same manner as the stomach contents. The relative selec-
tivity of chinook salmon for each food item was calculated
according to the method described by Inlev (1961). The
electivity index equation is
ri'pi
r1+Pi

 

TABLE 7.--The mean numbers 2: eight food organisms consumed
per fish for six sampling eriods, and the percentage 23
each food organism.in the total diet.

 

 

Mean Number of Each
Organism Consumed per Fish

Sampling Date

 

 

Percent-

Food age of 12 18 28 2 9 16
Organism Diet June June June July July July
Cladocerans 54.6 4.6 4.9 9.8 24.3 43.5 13.2
Copepods 2.2 0.2 0.1 3.6 0.1 0.0 0.7
Midge Larvae 19.4 7.5 4.0 10.4 6.9 4.9 9.0
Midge Pupae 18.7 6.8 0.9 7.1 1.3 8.0 21.9
Midge Adults 1.3 '0.3 0.4 0.8 0.1 0.1 2.3
Tubificids 0.3 0.3 0.0 0.1 0.0 0.0 0.0
Collembolans 1.9 0.1 1.0 0.7 0.0 0.1 0.2
Ostracods 0.9 0.7 0.5 0.2 0.0 0.1 0.0

I

40

where ri is the percentage of a food item in the fish ration,
and pi is the percentage of the same item in the environment.
An index of +1 indicates positive selection and -1 negative

selection for the food item. The corresponding stomach con-
tent and drift organism sample used for the electivity calcu-

lations are listed in Table 8.
Saleetivity

A comparison of the percentage composition of stomach
contents and drift samples for six different sampling

periods indicates selectivity for and against food items as
well as a change in preference with time (Figure 5).

Although the feedingactivity of the chinook salmon
was observed to be primarily restricted to floating or
drifting obJects near the upper reaches of the pond, their
food habits probably changed throughout the day, depending
on any cycles of food abundance in the study pond. On quiet
evenings the chinook salmon were distributed throughout the
pond and apparently fed at the surface on adult midge and
other flying insects. Changes in feeding behavior, and in
drift organism abundance throughout the day, would bias the
interpretation of the electivity index. Therefore, the
results of this study apply only to the time of day the

samples were collected.

TABLE 8.--Dates and times 2: chinook salmon stomach sample

41

and ggift organism sample comparisons.

 

 

 

 

Comparison Stomach Sample Drift Sample

Date Time Date Time
1 12 June 1500 14 June 1300
2 18 June 1430 14 June 1300
a 28 June 0900 26 June 0800

3 July 1445 2 July 0800
5 9 July 1300 9 July 0800
6 16 July 1300 16 July 0800

 

42

FIGURE 5.--E1ectivity indices for eight food items con-
sumed by 78 Juvenile chinook salmon collected on sampling
periods 1 (12 June), 2 (18 June), 3 (28 June), 4 (2 July),
5 (9 July) and 6 (16 July).

[“3]

[11

Kl-JHdHu—ac)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

9! C'mpoctanyr , I c OPIPOD:
o /\/\\ o A
“I -1
fl Mm 6! Int/at +1 ”/05: Pa ”4'
a a
a, "
fl Afloat Aral/z 7': fl Tue/:1: 10.:
o c
-/ -I 3‘ ‘f 4' =
H fig Cgsltqe 0444/: ” 012-0460;:
0 a h7g4
./ -I
I I I I I L I I _I l I
l 2 3 4 5 6 l 2 3 4 5 6
SAMPLING PERI ODS

44

Piscivorous Epeding

The termination of the study in July limited col-
lection of larger individuals to nine chinook salmon (mean =
94 mm). Some of them were collected, prior to the cessation
of flow over the weir, on 15 and 16 July, and others showing
stress symptoms were collected on 20 July. Several stomachs
were nearly empty. Examination showed: 11.1% cladocerans,
11.8% midge larvae, 55.3% midge pupae, 5.2% midge adults,
4.8% brook stickleback (under 22 mm total length), and 9.4%
miscellaneous insects. One individual contained seven
partially digested stickleback Juveniles. Even though small
forage fish were often observed in the pond, no other inci-

dents of piscivorous feeding were found.

Competition

The major forage fish species in the study pond,
including northern redbelly dace, creek chubs, and brook
stickleback, were abundant (Table 4; Table 5) and undoubtedly
did compete with the chinook salmon for food. The stomachs
of the chubs and dace contained small quantities of clado-
cerans, copepod, and midge pupae. The stickleback stomachs
contained the same food items in larger amounts than the
dace or chubs, but in much smaller quantity than the chinook

salmon.

45

Djscussion
The availability of sufficient food to sustain

Juvenile salmon for an extended period is a necessary con-
sideration for the introduction of salmonids to a new area
(Chapman and Quistorff, 1938). Growth rate, which is a
reflection of food supply (Burrows, 1963; Chapman, 1965),
has previously been Shown to be an important factor in
determining survival of salmonid Juveniles.

Shapovalov and Taft (1954) state that the food of
young salmonids of a given species depends on the locality,
time of year, size of fish, and relative abundance of food
items. However, consideration must also be given to food
preference by the species. A

The feeding behavior I observed in the chinook
salmon was similar to that described by Rutter (1904).
Their behavior indicated they were sight feeders that
showed preference for certain food items. The same feeding
behavior was described by Ricker (1937) for Juvenile
sockeye salmon and by Shapovalov and Taft (1954) for Juve-
nile steelhead trout and coho salmon. The fact that chinook
salmon Juveniles show preference for certain food items is
demonstrated by the application of Inlev's (1961) index for
electivity to my study pond data.

Cladocerans, 54.6% of the total food items, tended
to decline in preference with increasing age and size of the

chinook salmon Juveniles. A high negative preference was

46

found for copepods (2.2% of the total diet), possibly because
they were generally much smaller than the cladocerans. Simi-
lar to the findings of Galbraith (1967) for rainbow trout
and yellow perch, the chinook salmon appeared to feed selec-6
tively on the larger cladocerans and copepods.
Midge larvae (19.7% of the total diet) increased
in preference through the sampling periods, but midge pupae
(18.7% of the total diet) remained in steady preference.
The high degree of selection for midge adults and collem-
bolans is insignificant because they were only 1.3% and 1.93,
respectively, of the chinook salmon diet. Ostracods were
only 0.9% of the total diet, and appeared to be eaten only
incidentally. The highly negative preference for tubificids
(0.36 of the total diet) is difficult to explain since they
were of the same general size as the midge larvae. Although
unlikely, it is possible that the tubificids were digested
much faster than other food items. Other soft bodied food
items in the diet were often found in excellent condition.
Food preference by chinook salmon in a bonafide
stream situation in Michigan could possibly differ from
what was found in the study pond. I examined the stomach
contents of 22 chinook Juveniles (mean = 79.3 mm) obtained
from Robert Drummond (District Fish Biologist, Michigan
Department of Natural Resources) which were collected on
30 and 31 May, 1968 from the Ocqueoc River north of Rogers

City, Michigan. The contents by enumeration were: 68.8%

47

cladocerans, 21.9% midge adults, 7.9m copepods, 1.2% midge
pupae, and 12.0% Ephemeroptera naiads. Seven of the fish
contained all of the cladocerans, indicating they either had
a high individual preference for cladocerans, or they had
been located in the environment where these food items were
in abundance. I observed similar "individual preference"
in the salmon from the study pond.

Several studies of Juvenile chinook salmon food
habits have been made by biologists on the Pacific Coast,
but they list only the organisms found in the stomach samples,
and not what was available in the environment. Rutter (1904)
summarized the stomach contents of the 198 specimens (mean =
75 mm) he collected in all months of the year as: 32.0%
larval insects, 43.2% naiad or pupal insects, 15.26 flying
insects, 1.6% terrestrial insects and 8.0% crustaceans by
number. Three fish had eated 98% of all crustaceans found.
The main food items were from the orders Coleoptera, Diptera,
Ephemeroptera, HymenOptera and Plecoptera. In a sample of
20 Juvenile chinook salmon (mean = 67 mm) from brackish
water he found that amphipcds, copepods and adult insects
were 2.55, 74.05 and 23.4% by number, respectively. Only
one fish had been eaten.

In examining stomach contents of immature chinook
salmon from Alaskan rivers, Chamberlain (1907) found that
the food was almost wholly insects from the water surface,

with amphipods being eaten occasionally by larger chinook

48

salmon in estuaries. Clemens (1934) examined the stomach
contents of 64 chinook salmon Juveniles (under 83 mm stan-
dard length) from Shuswap Lake, British Columbia and reported
that in addition to terrestrial insects and Tendipedidae
larvae, pupae and adults, large numbers of cladocerans and
copepods were eaten. Chapman and Quistorff (1938) found
that chinook salmon collected in the north central Columbia
River drainage lived almost entirely on insects. The most
abundant insects were: Diptera larvae, beetle larvae,
stonefly nymphs and leaf hoppers in the 301 chinook salmon
(44-152 mm standard length) examined. Reg (1952) lists the
contents of 60 chinook salmon fingerlings collected in the
Duwamish River estuary from May through July (no age or
size given) as: 43% Diptera larvae, pupae and adults;
32% marine crustaceans; 20% terrestrial insects; 3% mayfly
and stonefly larvae; and 1% freshwater crustaceans by number.
he food habits of chinook salmon Juveniles from
Pacific Coast rivers differ somewhat from what Clemens (1934)
reported for chinook salmon from a lake environment, or from
what I found from the study pond salmon, in that the former
contained few crustaceans. The difference is probably
explained by the fact that cladocerans and copepods normally
do not inhabit streams (Pennak, 1953). I did find large
numbers of cladocerans and copepods in the stomachs of some
chinook salmon collected from the Ocqueoc River, but there

is a lake on the river that may have been the source of the

crustaceans.

49

The food habits of Juvenile coho salmon, sockeye
salmon and steelhead trout in a stream environment are very
similar to those of the chinook salmon in a stream environ-
ment (Chapman and Quistorff, 1938; Shapovalov and Taft, 1954).
Similarly, Juvenile sockeye salmon and young rainbow trout
in lake environments feed heavily on cladocerans and c0pepods
(Ricker, 1937; Galbraith, 1967). The food items preferred
by Juvenile chinook salmon in the Great Lakes environments
would probably not differ from the food items preferred in
Pacific Coast environments.

New authors have reported separately the food habits
of the larger Juvenile chinook salmon over 90 mm. Rutter
(1904) found yearling (residual) chinook salmon to prey on
alevin or sac fry chinook salmon, and Korn'gp.nll, (1967)
found them to prey on other salmonid fry.

Although small immature forage fish were present
in the study pond in June and July, and even on occasion
were collected in drift samples, only the larger salmon
Juveniles were found to prey on them. I did not find any
reference in the literature to piscivorous food habits in
small chinook salmon (under yearlings) other than the one
instance reported by Rutter (1904). This implies that,
until Juvenile chinook salmon reach a large Size (over 85
mm) they are in direct competition with forage fish species
for food.

The food habits of the northern redbelly dace,

creek chubs and brook stickleback were similar to those of

50

the chinook salmon. The threespine stiCkleback (Gasterosteus

 

aculeatus) is reported to be a major competitor of young
sockeye salmon in some lake systems (Foerster, 1968). Con-
ceivably the brook stickleback could be a maJor competitor
with residual chinook salmon in a reservoir or pond. How-
ever, the chinook salmon generally occupied the upper end
of the pond over the gravel bottom, and the stickleback
occupied weeded areas in the lower end of the pond which
probably eliminated direct competition.

The northern redbelly dace and creek chubs occupied
some of the same areas of the pond as the chinook salmon,
but I observed Size dominance to play a major role in
selecting feeding sites. The salmon appeared to be dominant
in selecting feeding sites which probably eliminated some
competition for food.

The presence of adult alewife (nlpnnpseudoharengnp)
in large numbers on spawning runs to the river mouths and
bays in the spring months (Odell, 1934; Brooks and Dodson,
1965; Wagner pers. comm., 1969) presents the threat of
serious competition for food with migrating Juvenile chinook
salmon in the Great Lakes. Wagner (pers. comm., 1969) reports
that the alewife in Little Bay de Noc fed during the entire
period they were in the bay. He listed the main food items
as cladocerans and copepods. Brooks and Dodson (1965) and
Smith (1968) have cited evidence that alewife are dominant

in competition with other fish for the larger plankton.

51

The present practice of planting fall run chinook
salmon in the spring places the Juvenile chinook salmon,
at a size where they feed on plankton, in a location where
competition for food is great. Korn.p£.§1. (1967) in a
study of salmonid migratory behavior in small impoundments,
found the salmon tended to cease migration once they reached
the quieter water of the reservoir. Based on this informa-
tion, I think that Juvenile chinook salmon will reside tem-
porarily in river mouths and bays after downstream migration
' to these areas. Young salmon in the ocean do feed in bays
and along shores during their first summer (Hoar, 1953). If
the chinook salmon Juveniles were of a large enough size to
have piscivorous feeding habits, some competition might be
avoided.

Wagner (ners. ppnn., 1969) reported that the alewife
in Little Bay de Noc spawn in late June and larval alewife
should be present by the first of July. Perhaps by planting
larger chinook salmon at this time, greater returns of
larger individuals could be obtained. The interaction of

alewife and chinook salmon should be investigated.

SUMMARY AND

RECOMMENDATIONS FOR MANAGEMENT

I could find little conclusive evidence of any
pattern in chinook salmon migration from the study pond.

The 39 migrants collected at the pond exit were similar in
size to the chinook salmon remaining in the pond. Evidence
of smoltification (loss of parr marks and increased silveri-
ness) was present in the migrants, but to no greater extent
than in most individuals in the study pond. There were indi-
vidual differences in the degree of smoltification, but I

did not observe a size relationship.

I do believe that much of the migration was forced
migration due to lack of suitable habitat for a large num-
ber of salmon. This would explain the lack of any Size or
smoltification relationship in the migrants. Emigration
probably occurred continuously during the study period.

The growth rate of the chinook salmon appeared as
good or better than that reported for Pacific Coast chinook
salmon. EXplanations are difficult because of the many
factors that affect growth. Dissolved oxygen, water tempera-
ture and available food are reported to be the most important
factors influencing growth. The importance of growth or more
precisely, size, on survival and return of the chinook salmon
can not be over-emphasized. Larger salmonid Juveniles smol-

tify and emigrate faster, compete better and are preyed upon

52

53

less than smaller Juveniles. Control of smoltification may
be possible through controlled growth and photoperiod regu-
lation.

The results of the food studies indicate that the
study pond chinook salmon positively selected cladocerans
and midge larvae, pupae and adults as their main food items.
Competition for food between the salmon and forage fish
species in the pond did occur, but I believe it was limited
by the dominant behavior the chinook salmon displayed in the
selection of feeding sites. Food was apparently abundant and
should not have interfered with smoltification.

Although it was not studied, competition between
alewife and Juvenile chinook salmon in the Great Lakes could
limit the success of the introduction because of their simi-
lar food habits and presence in the same areas in the Spring.

The larger chinook salmon I examined exhibited pisci-
vorous feeding habits to some degree. Because of this, the
possibility of coordinating the planting of larger chinook
salmon with the hatching of young alewife should be investigated.

Another possibility for sport fishing management in
the Alpena area is to plant spring run chinook salmon. Because
there is probably a temperature and physical barrier to up-
stream migration, the adults returning in the spring may delay
in the deeper parts of Thunder Bay and be exposed to the sport

fishery throughout the summer.

LITERATURE CITED

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