United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
EPA-600/3-80-045
May 1980
Research and Development
Environmental
Effects of Western
Coal Surface Mining
Part VI.
Smallmouth Bass and
Largemouth Bass in the
Tongue River Reservoir,
Montana, 1975-76
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/3-80-045
May 1980
ENVIRONMENTAL EFFECTS OF WESTERN COAL SURFACE MINING
PART VI - SMALLMOUTH BASS AND LARGEMOUTH BASS IN
THE TONGUE RIVER RESERVOIR, MONTANA, 1975-76
by
Russell F. Penkal and Richard W. Gregory
Cooperative Fishery Research Unit
Montana State University
Bozeman, Montana 59717
Grant No. R803950
Project Officer
Donald I. Mount
Environmental Research Laboratory - Duluth
Duluth, Minnesota 55804
ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
DULUTH, MINNESOTA 55804
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DISCLAIMER
This report has been reviewed by the Environmental Research Laboratory-
Duluth, U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views
and policies of the U.S. Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation for use.
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FOREWORD
This report, sixth in a series on environmental effects of surface coal
mining in the west, is a documentation of the population of smallmouth and
largemouth bass in the Tongue River Reservoir. This water body is adjacent
to a large surface mine which will be the largest in the world if present
plans materialize, other mines exist in the drainage basin. Studies such as
this one will be vital to a long-term assessment of any major impacts of such
development.
Approaching impact assessment by field population studies has both
positive and negative features. By use of direct measures of species
populations of high value to the public, the problem of interpreting small
changes in growth, mortality, and reproduction displayed by surrogate species
in laboratory tests is avoided. Such field assessments, however, lack
precision to detect subtle changes and so must be accompanied by repeated
assessments to achieve the needed sensitivity to detect impact from the
mining activity.
J. David Yount, Ph.D.
Deputy Director
Environmental Research Laboratory-Duluth
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ABSTRACT
Population parameters of smallmouth bass (Micropterus cblom-ieu-i] and
largemouth bass (M. salmoides] were studied during 1975 and 1976, before ex-
pansion of surface coal raining adjacent to the Tongue River Reservoir in
southeastern Montana. Reproductive success, as determined by alongshore
seining, varied in different areas of the reservoir and may be correlated to
turbidity. Population estimates were obtained at night during spring and fall
1976 with boat electrofishing gear. For yearling and older smallmouth bass
the fall population of 13.0 fish/ha and the standing crop of 2.03 kg/ha repre-
sented 80 and 84 percent of the totals for basses in the reservoir. The
largemouth bass population and standing crop during fall 1976 was 3.2 fish/ha
and 0.32 kg/ha. The dominance by smallmouth bass of all year classes for
both species except age-1, was attributed to a much higher mortality of under-
yearlings among largemouth bass. This higher mortality of largemouth bass may
be correlated to a lack of shoreline vegetation in the reservoir- Summer
mortality of age-2 and older smallmouth bass, estimated from the reduction in
numbers of marked fish, was about 40 percent. Smallmouth bass growth and
condition were better in the upper than lower end of the reservoir; the differ-
ence may be due to forage fish availability. Growth and length-weight rela-
tionships were above average for both species when compared with basses in
other northern waters, indicating no noticeable effect from nearby surface
coal mine operations at the time of the study.
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables vii
Acknowledgement viii
I Introduction 1
II Conclusions 4
III Recommendations 5
IV Description of the Study Area 6
V Methods 11
VI Results 13
Age and Growth 13
Reproductive Success 13
Population and Standing Crop 13
Mortality 20
Movement and Seasonal Population Changes
of Smallmouth bass 25
VII Discussion 31
Age and Growth 31
Reproductive Success 32
Population and Standing Crop 32
Mortality 34
Movement and Seasonal Population Changes
of Smallmouth bass 34
VIII Potential Impacts of Surface Coal Mining 36
Literature Cited 42
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FIGURES
Number Page
1 Map of Montana showing location of Tongue River Reservoir 2
2 The three study areas of the Tongue River Reservoir ... 7
3 Turbidity in three areas of the Tongue River Reservoir ...... 8
4 Length-weight relationship of smallmouth bass collected
in areas B and C of the Tongue River Reservoir, fall 1976 16
5 Movement within the Tongue River Reservoir of smallmouth bass
marked in the spring or summer and recaptured during the
summer or fall, 1976 . 28
6 Movement of smallmouth bass marked and recaptured in the
Tongue River Reservoir during fall, 1976 ... . 29
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TABLES
Number Page
1 Shoreline substrate of the Tongue River Reservoir . 9
2 Back-calculated total lengths and weights of smallmouth
bass and largemouth bass in the Tongue River Reservoir 14
3 Smallmouth bass back-calculated lengths and weights, Tongue
River Reservoir, 1976 15
4 Mean condition (K) by 50-mm length intervals of smallmouth
bass and largemouth bass collected in the Tongue River
Reservoir, fall 1976 17
5 Shoreline seining by areas for 1975 and 1976 combined,
Tongue River Reservoir 18
6 Petersen catch statistics for age-1 and older smallmouth bass
in the Tongue River Reservoir, fall 1976 . . 19
7 Population and standing crop estimates for age-1 and older
smallmouth bass and largemouth bass in the Tongue River
Reservoir, fall 1976 ......... ..... 21
8 Age structure of the bass populations and standing crops
in the Tongue River Reservoir, fall 1976 ..... 22
9 Fishes caught by alongshore seining in the Tongue River
Reservoir, 1975 and 1976 23
10 Petersen catch statistics for estimating smallmouth bass
populations in the Tongue River Reservoir, spring 1976 . 24
11 Calculations for summer mortality of age-2 and older
smallmouth bass, 1976 26
12 Schumacher and Eschmeyer catch statistics for age-2 and
older smallmouth bass in two areas of the Tongue River
Reservoir, 1976 ........... 27
13 Averages and ranges of some chemical and physical parameters of
the Tongue River Reservoir, November 1975 to November 1976 .... 37
14 Average values of selected parameters measured in the Decker
Mine discharge water and in the Tongue River above and below
the mine discharge, June 1975 to November 1976 ..... 39
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ACKNOWLEDGEMENT
We thank those who assisted in this study: Victor Riggs, Janet Amestoy,
William Gardner, John Fraley, Stephen Leathe, and Stephen Whalen aided in the
field work; Allen Elser and the Montana Department of Fish and Game assisted
in the field data collection and provided a large portion of the field equip-
ment. Special thanks are extended to the management of the Decker Coal Com-
pany, which provided facilities for the field research station.
This research was funded in part by the U.S. Environmental Protection
Agency, Environmental Research Laboratory-Duluth, Research Grant No. R803950,
awarded to Natural Resource Ecology Laboratory, Colorado State University,
and Fisheries Bioassay Laboratory, Montana State University.
vm
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SECTION I
INTRODUCTION
The Tongue River watershed, including the Tongue River Reservoir, lies
in the Fort Union Coal Basin, an area that encompasses a large portion of
eastern Montana (Figure 1) as well as parts of northern Wyoming and western
North Dakota. The Fort Union Basin, and other coal deposits in the northern
Great Plains, contain nearly half of the nation's known coal reserves. To
meet the nation's growing energy demands, surface coal mining in the Fort
Union Basin is rapidly increasing.
The largest surface coal mine in the Tongue River area is the Decker
Mine, located on the southwest shore of the Tongue River Reservoir in eastern
Montana, just north of the Wyoming border. The Decker Mine began operation
in 1972, and is currently being expanded to the southeastern shore of the
Reservoir; permit application has been made for expansion northward along
the western shore. As the mine expands, and production increases, the Decker
Mine complex is projected to be the largest surface coal mine in the world.
In addition to the Decker Mine, other mines are located in the Tongue River
watershed, farther up river in Wyoming. Resource development plans also call
for construction of mine-mouth coal-fired power plants in that same region.
Historically, water from the Tongue River has been used for agriculutral
purposes and the raising of livestock. In 1939 an earthfill dam was completed
on the Tongue River, forming a reservoir for flood control and irrigation
water storage. In recent years the reservoir has also become an important
recreation area.
The potential impacts from coal mining and proposed coal combustion fa-
cilities on the Tongue River system are largely unknown. To provide a basis
for measuring that impact, a variety of studies have been undertaken by the
Montana Cooperative Fishery Research Unit, U.S. Fish and Wildlife Service, on
the present status of the aquatic biota of the river and reservoir. The
research reported here is the result of a study conducted during 1975 and
1976 on the populations of smallmouth bass (Micropterus dolomieui] and large-
mouth bass (M. salmoides] in the Tongue River Reservoir. Minimal research
has previously been reported on these two species in Montana; the only two
published papers concern the growth of largemouth bass in Montana ponds
(Brown 1952; Brown and Logan I960). The immediate objective of the present
research was to study the age and growth, reproductive success, and population
size of these two species in the Reservoir, and to see what discernable im-
pact, if any, present coal mining operations might be having on these fishes.
The longer range objective was to provide information against which compari-
sons can be made in the future as mining operations in the Tongue River
watershed increase.
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V
\
I
\_
\
M 0
Helena
Bozemon i
^ -Tongue River Reservoir
/J Fort Union Coal Region
Figure 1. Map of Montana showing location of Tongue River Reservoir.
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Additional studies on the aquatic biota of the Tongue River and Reser-
voir will be reported separately. These include reports on the microbiologi-
cal community within the Decker Mine settling pond (Turbak et al., in press),
the limnology of the Tongue River Reservoir (Whalen 1979), and the distribu-
tion and behavior of walleyes (stizostedion vitreum] and saugers (S. cana-
dense] in the reservoir (Riggs and Gregory, in press). Information from
these and the present study will be of value in formulating recommendations
for institution of appropriate safeguards to protect aquatic life as mining
and combustion operations expand in this region of the country which has re-
latively little water and a fragile environment.
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SECTION II
CONCLUSIONS
1. Reproductive success of largemouth bass and smallmouth bass in the
Tongue River Reservoir was limited by the amount of suitable spawning
substrate and the turbidity.
2. Growth and length-weight relationships of both species were excellent
for a northern latitude impoundment. These relationships for largemouth
bass were superior to those for smallmouth bass.
3. The smallmouth bass fall populations and standing crops were average
when compared to reports on other impoundments; by comparison the same
measurements for largemouth bass were extremely low. The low measure-
ments for largemouth bass are probably attributable to a lack of suitable
habitat and/or significantly higher mortality rates between the finger-
ling and yearling stages.
4. Based on the present and related concurrent studies on fishes and the
limnology (including water chemistry) of the Tongue River Reservoir,
there is no evidence that the present level of surface coal mining
activity adjacent to the reservoir is having a measurable effect on the
growth rate and reproductive success of either largemouth bass or small-
mouth bass in the reservoir.
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SECTION III
RECOMMENDATIONS
Additional studies should be initiated on the fishes of the Tongue River
and Reservoir as surface coal mining continues and expands in the areas
immediately adjacent to the reservoir and the river above the reservoir.
These studies should include measurements of growth rates, reproductive
success, and standing crop of the important fishes, including largemouth
bass and smallmouth bass, in the reservoir, and should be correlated
with further limnological measurements, including water chemistry para-
meters.
Although the State of Montana Department of Fish and Game has conducted
periodic creel surveys on the reservoir, additional surveys should be
initiated as the level of surface coal mining activity increases.
Results of such surveys will permit distinguishing possible effects on
the fish populations resulting from surface mining activity and those
from increased fishing pressure; this latter may well prove to have the
greater impact.
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SECTION IV
DESCRIPTION OF THE STUDY AREA
The Tongue River Reservoir in Big Horn County, southeastern Montana, is
32 km north of Sheridan, Wyoming, the closest population center. At storage
capacity the reservoir has an average depth of 6.1 m, a maximum length of
12.5 km, and a maximum breadth of 1.4 km (Garrison et al. 1975). Height of
the earthfill dam, which was completed in 1939, is 27.7 m; spillway elevation
is 1043.7 m above mean sea level (U.S. Geological Survey 1976). Surface area
and length of shoreline at spillway elevation are 1277 ha and 60 km, respec-
tively. Total storage capacity in 1947 was 85.6 hm3 (U.S. Geological Survey
1976), but sedimentation has undoubtedly reduced this capacity. In 1976 the
maximum depth at spillway elevation was 18 m and the bottom of the outlet was
15.2 m from the surface of the spillway. Because of an annual water level
fluctuation of 3 to 6 m, submerged and emergent vegetation have not become
established. Thermal stratification occurs for a short period in late spring
and early summer but disappears quickly due to wind mixing and discharge of
water from the outlet. Dissolved oxygen concentrations decrease to values
less than 3 mg/liter at depths greater than 8 m in late summer (Whalen and
Leathe 1976).
The reservoir was first stocked with warm water fishes in 1963. Large-
mouth bass were stocked as fingerlings in 1964, 1972, and 1973. Smallmouth
bass were first captured in the reservoir in 1972; however, records of the
Montana Fish and Game Dept. include no plantings of smallmouth bass. This
species probably entered the Tongue River system and then the reservoir from
adjacent strip-mine ponds near Sheridan, Wyoming. During the time of study
the reservoir had only light use by fishermen (Elser et al. 1977).
The reservoir was divided into three sections on the basis of habitat
type (Fig, 2). The shallow inflow section (area A) had an approximate maxi-
mum depth of 6 m and was most affected by summer water level reduction.
During summer 1975, this area was completely dewatered due to large with-
drawals, and had the highest turbidities recorded throughout the study (Fig.
3). Favorable bass spawning substrate (pebbles and cobbles) made up only 14
percent of the shoreline substrate in area A while unsuitable substrate (silt
and clay) made up 51 percent (Table 1).
The central portion of the reservoir was designated area B, and the lower
portion area C, Physical characteristics of area B were intermediate to those
of areas A and C. Water level fluctuations had less effect on habitat because
the water was deeper (14 m maximum). Turbidities were much lower than in area
A (Fig. 2), Pebbles and cobbles made up 43 percent of the dominant shoreline
substrate and silt and clay accounted for 19 percent (Table 1).
-------
Figure 2. The three study areas of the Tongue River Reservoii
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co
30-
23-
1975
1976
JULY ' MWWST ' SCPT OCT
-SPIT
JULY
AIM.
MONTH
Figure 3. Turbidity (Jackson turbidity units) in three areas of the Tongue River Reservoir,
(S. C. Whalen, Montana Cooperative Fishery Research Unit, unpublished data.)
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TABLE 1. SHORELINE SUBSTRATE OF THE TONGUE RIVER RESERVOIR.
Area A
Area B
Area C
Total
Number of 0.25 km study sections
Percent of Sections:
Silt to clay (less than 0.062 mm)
Very fine to medium sand (0.062 - 0.5 mm)
Coarse to very coarse sand (0.5 - 2 mm)
Pebbles (2 - 64 mm)
Cobbles (64 - 256 mm)
Boulders (greater than 256 mm)
69
63
65
197
50.7
30.4
0.0
1.4
13.0
4.3
19.0
14.3
19.0
25.4
17.5
4.8
13.8
6.2
4.6
33.8
26.2
15.4
28.4
17.3
7.6
19.8
18.8
8.1
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Area C had a maximum depth of 18 m, and as a result fish habitat was
least affected by water level declines. Turbidities were generally lower in
this area especially during the spring and early summer (Fig. 3). Pebbles
and cobbles comprised 60 percent of the shoreline substrate while silt and
clay accounted for only 14 percent (Table 1).
There was less than one degree (Celsius) difference in mean temperature
of the upper 6 m of water among areas A, B, and C (Whalen 1979).
10
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SECTION V
METHODS
The dominant particle size of shoreline substrate was analyzed during
mid-July 1976 when the reservoir surface elevation was 1042 m. Vertical
distribution of the substrate above the silted portion of the basin was
fairly uniform. This analysis should represent substrate available to bass
at preferred spawning depths (l-7m). A topographic map of the reservoir was
used to divide the shoreline into 0.25-km study sections. Each section was
visually classified according to the size of its dominant substrate based on
the Wentworth Classification System (Welch 1948). The number of sections
classified alike were totaled and percentages were computed for each area.
Relative abundance of black bass fingerlings was based on collections
with 30.5-m beach seines and 15.3-m bag seines during August and September in
both 1975 and 1976. Each haul with the larger and smaller seines sampled
approximately 19 and 9.5 m of shoreline, respectively. Seine results were
equally weighted by (1) hauling the bag seine twice at each sample area or
(2) multiplying the bag seine results by a factor of two. Both seines had a
mesh size of 6.4 mm (bar measure).
Older bass were collected at night with a Type VI Smith Root electro-
fishing boat, a Coffelt variable voltage pulsator, Model VVP-10, and a 230-V,
4000-w, AC generator. The electrode array was designed according to Novotny
and Priegel (1974) for direct current output. The entire shoreline of areas
B and C were fished three times during the spring and early summer of 1976.
The entire shoreline of the Tongue River Reservoir was electrofished twice
during late August to mid-September 1976. All electrofishing occurred at
night.
Fish total length and weight were measured to the nearest 1 mm and 10
gms. Fishes collected in the spring and fall were given different kinds of
fin clips. Ages of bass were determined by examining celluolose acetate
scale impressions on a projector at 66x. Fish age assignments were made by
adding one year to the ages indicated by the number of annuli laid down be-
fore the calendar year in which the fishes were collected. Scales were
collected below the lateral line from the area covered by the right pectoral
fin when appressed to the body. Total lengths were partitioned into 1 cm
intervals and scales were collected from at least 20 fish (where possible)
in each length interval.
Population estimates, 95 percent confidence intervals, age structures,
and standing crops were computed using methods similar to those summarized
11
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by Vincent (1971). The Schumacher-Eschmeyer equation (.Formula 3.12 in Ricker
1975) was used to compute population estimates in the spring, and the Chapman
modification of the Petersen formula (Formula 3.7 in Ricker 1975) was used in
the fall.
Vincent (1971) calculated the total population and its variance by sum-
ming sub-estimates for several total-length intervals within the population.
He divided the population into different size groups to reduce effects of
unequal sampling efficiency for different sizes of fish. In this study, the
populations were partitioned into 2 or 3 size groups depending on sample
size. Age structure was determined by proportioning the population into
total-length groups according to the relationship between age and total length
(as determined by scales). Standing crop was estimated by multiplying the
average weight of fish of each age group (total length group) times their
estimated number (see Vincent 1971).
A spring and early summer population estimate of smallmouth bass was
calculated by treating the three spring and early summer electrofishing runs
as the mark run, and the fall electrofishing circuits as the recapture run.
Too few largemouth bass were collected to obtain an estimate of their spring
population. Smallmouth bass fall population estimates were calculated for
areas A and B combined and area C. An estimate of the smallmouth bass popu-
lation and its variance for the entire reservoir was computed by summing the
estimates of both areas. Summer mortality of age-2 and older smallmouth bass
was estimated from the reduction of spring-marked smallmouth bass in the fall
population. Because of the small sample size of largemouth bass, a fall pop-
ulation estimate could be computed only for the entire reservoir.
Scale samples collected during the fall were used to back-calculate
length at annul us formation. The relationship between total length and an-
terior scale radius appeared linear for both largemouth bass and smallmouth
bass (r = 0.960 to 0.978), so Method 2 described by Tesch (1971) was used for
back-calculation.
Condition factors were computed for basses over 150 mm in total length
with the following formula (Carlander 1969):
K = 105 W/L3
where W = weight in grams;
L = total length in millimeters.
The method of least squares was used to derive linear regressions.
12
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SECTION VI
RESULTS
Age and growth
Smallmouth bass were 92, 157, 232, 309, and 340 mm in length at the
first through fifth annul us (Table 2). The corresponding mean calculated
weights were 9, 52, 181, 454, and 618 gms, respectively. The length-weight
relationship for smallmouth bass in the Tongue River Reservoir was loq W =
-5.350 + 3.216 log L.
Largemouth bass were 86, 191, 267, 342, and 388 mm in length at the
first through fifth annulus (Table 2). Corresponding mean calculated weights
were 8, 107, 314, 697, and 1046 gms, respectively. The length-weight
relationship was log W = -5.319 + 3.221 log L.
Smallmouth bass had greater total lengths, at similar annuli in areas
A and B thru C (Table 3). Fish were heavier, over a similar range of lengths,
in area B (log W = -5.322 + 3.208 log L, n = 1212) than C (log W = -5.201 +
3.147 log L, n = 831) (Fig. 4). Too few fish were collected in area A to
obtain a representative length-weight relationship. For six total-length
intervals, the unweighted grand mean condition (K) was significantly greater
for smallmouth bass in area B than in area C (Table 4).
Too few largemouth bass were collected in each area to determine differ-
ences in growth. Condition factors were generally larger, although not
significantly, for fish collected in areas A and B than in area C (Table 4.)
Reproductive success
Smallmouth bass finger!ings were most abundant in area C, less abundant
in area B, and absent in area A; 7.5, 2.3, and 0 fingerlings were collected
per standard seine haul in each area, respectively (Table 5). Largemouth
bass fingerlings were found in all threee areas of the reservoir but showed
a similar distribution of abundance; 16.9, 3.7, and 1.2 largemouth bass
fingerlings were collected per standard seine haul in areas C, B, and A,
respectively.
Population and standing crop
Electrofishing gear was used to sample along the entire shoreline of the
Tongue River Reservoir during the fall 1976. During the first circuit, 1,156
smallmouth bass and 198 largemouth bass were marked. Durinq the second
circuit 1,371 smallmouth bass and 259 largemouth bass were captured; 12.3 per-
cent of the smallmouth bass and 9.3 percent of the largemouth bass had been
marked during the previous circuit (Table 6).
13
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TABLE 2. BACK-CALCULATED TOTAL LENGTHS (nun) AND WEIGHTS (g) OF
SMALLMOUTH BASS AND LARGEMOUTH BASS IN THE TONGUE RIVER RESERVOIR,
Year Class
a/
1970
1971
1972
1973
1974
1975
Grand Mean
Calculated
Weight
a/
1969
a/
1970
1971
1972
1973
1974
1975
Grand Mean
Calculated
Weight
Number
of Scales
Examined
4
22
13
113
271
97
2
2
11
5
31
65
318
Annulus
1
102
96
100
89
90
83
92
9
100
87
92
87
87
86
79
86
8
2
192
165
162
158
142
157
52
244
249
204
203
166
192
191
107
3
Smallmouth
274
236
253
206
232
181
Largemouth
319
342
286
270
246
267
314
456
Bass
331 373 401
318 340
300
309 340 401
454 618 1051
Bass
382 416 445
385 412 442
355 388
329
342 388 444
697 1046 1615
7
459
459
1798
a/ Not included in Grand Mean except for oldest age groups.
14
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TABLE 3. SMALLMOUTH BASS BACK-CALCULATED LENGTHS (mm) AND WEIGHTS (g),
TONGUE RIVER RESERVOIR, 1976.
AREA A
Year Class
1970
1971
1972
1973
1974
1975
Grand Mean
Calculated
Weight
n 1
3 99
1 96
6 85
39 90
3 92
92
10
2345
157 235 321 356
230 256 327
165 217
149
175 236 324 356
76 192 513 687
n
3
12
9
76
130
40
1
103
97
101
90
91
85
95
11
AREA B
2
202
168
163
161
148
168
66
3456
289 346 386 410
241 325 343
255 301
210
249 324 365 410
232 566 790 1148
n 1
1 92
7 93
3 92
31 86
102 87
54 81
89
8
AREA C
2
126
151
158
147
130
142
37
3 4 5
178 233 291
215 287 325
245 297
192
208 272 308
127 302 450
6
346
346
654
n = Number of scales examined.
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1600-1
WOO-
1200-
1000-
AREA B
AREA C
s
12
u
800-
600-
400-
200-
150 200 250 300 350
TOTAL LENGTH (MM)
4OO 43O
Figure 4. Length-weight relationship of smallmouth bass collected
in areas B and C of the Tongue River Reservoir, fall 1976
16
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TABLE 4. MEAN CONDITION (K) BY 50-MM LENGTH INTERVALS OF SMALLMOUTH BASS AND LARGEMOUTH
BASS COLLECTED IN THE TONGUE RIVER RESERVOIR, FALL 1976. (Grand
means with corresponding superscript^/ are significantly different.
Standard deviations are in parenthesis).
Section A
Interval
151-200
201-250
251-300
301-350
351-400
401-450
Unweighted
Grand Mean
151-200
201-250
251-300
301-350
351-400
401-450
451-500^
Unweighted
Grand Mean
N
7
25
9
0
5
0
4
0
10
2
7
3
0
Mean
1.444 (
1.442 (
1.607 (
...
1.459 (
1.488 (
1.455 (
---
1.689 (
1.766 (
1.879 (
1.827 (
...
1.723 (
K
.192)
.134)
.138)
.068)
.080)
.047)
.168)
.172)
.140)
.190)
.166)
Mean TL
185 (16)
229 (14)
268 (15)
...
383 (21)
---
266 (85)
157 (19)
...
280 (13)
306 (6)
387 (9)
425 (15)
---
311 (104)
N
225
757
180
33
14
3
9
5
26
10
2
4
0
Section B
Mean K
Smallmouth Bass
1.365 (.159)
1.491 (.177)
1.536 (.159)
1.542 (.130)
1.458 (.209)
1.694 (.171)
1.514^.109)
Largemouth Bass
1.517 (.223)
1.558 (.119)
1.686 (.150)
1.843 (.177)
1.814 (.379)
1.851 (.107)
---
1.712 (.148)
Section C
Mean TL
177 (16)
225 (15)
268 (15)
319 (15)
376 (14)
430 (21)
299 (95)
154 (3)
229 (15)
285 (11)
319 (12)
397 (2)
434 (16)
...
303 (104)
N
378
381
56
9
5
2
2
11
39
13
3
2
2
Mean
1.342 (
1.418 (
1.434 (
1.366 (
1.446 (
1.298 (
1.384-{
1.334 (
1.599 (
1.656 (
1.604 (
1.644 (
1.761 (
1.846 (
1.600 (
K
.189)
.148)
.106)
.173)
.069)
.004)
.058)
.117)
.186)
.143)
.079)
.147)
.036)
.065)
.143)
Mean TL
180 (15)
220 (14)
266 (14)
314 (7)
388 (5)
418 (4)
298 (94)
195 (4)
213 (13)
279 (9)
316 (17)
380 (19)
431 (6)
484 (26)
302 (93)
Interval not Included 1n unweighted mean.
-------
TABLE 5. SHORELINE SEINING BY AREAS FOR 1975 AND 1976 COMBINED,
TONGUE RIVER RESERVOIR. (Number of seine hauls
are shown in parentheses.)
Species
and total ,
length (mm)
Smallmouth Bass
<100
100 - 200
Largemouth Bass
Finger! ings
100 - 200
Others-/
Total
Area A
(23)
No. per %
haul
0.0 0.0
0.1 0.2
1.2 1.9
0.7 1.1
62.6 96.9
64.6
Area B
(58)
No. per %
haul
2.3 4.7
2.5 5.1
3.7 7.5
0.7 1.4
40.2 81.4
49.4
Area
(41)
No. per
haul
7.5
2.0
16.9
0.4
19.9
46.7
C
%
16.3
4.3
36.2
0.9
42.6
' Ra<;<; < 100 mm Innn u/ovia nrimayilv unnnn n-f tho v/oav- thnco 100-900 mm
long were primarily yearlings.
Includes in decreasing order of abundance: yellow perch (Perca
flavesGens), black and white crappie (Pomoxis nigromaeutatus and P.
annularis), carp and goldfish (Cypri.nus carp-io and Carrassius auratus) ,
golden shiner (Notemigonus orysoleuoas), shorthead redhorse (Moxostoma
macrolepidotim) , black and yellow bullhead (Ictalurus melas and
J. natalis) , pumpkinseed (Lepomis gibbosus), northern pike (Esox
luaius) - Fish sampled only occasionally with seines include walleye
(Stizostedion vitrewn), sauger (S. eanadense), white sucker (Catostorms
commersoni), longnose sucker (C. aatostomus), rock bass (Ambloplites
rupestris), channel catfish (Ictaluras punatatus), and green sunfish
(Lepomis oyanellus) .
18
-------
TABLE 6. PETERSEN CATCH STATISTICS FOR AGE-1 AND OLDER SMALLMOUTH BASS IN THE TONGUE RIVER
RESERVOIR, FALL 1976. (The 95% confidence intervals are in parentheses.)
Population ,
Estimate -'
Population
Estimate
Population estimate
Area A + B Combined
101-190 mm total length interval 191-450 mm total length interval
M C R M C R
118 110 12 594 597 72
1006 (496-1516) 4874 (3812-5936)
Area C
101-170 mm total 171-220 total 221-411 total
length interval length interval length interval
MCR NCR MCR
156 163 21 226 299 41 62 202 23
1170 (756-1624) 1621 (1163-2079) 532 (332-732)
for entire reservoir 9303 (7200-11,206)
Corrected for 0.9% age 0 fish in catch.
-------
The estimated 9,023 smallmouth bass was 80 percent of the total bass
fall population, while largemouth bass, estimated at 2,296, comprised the
other 20 percent. The smallmouth bass standing crop, 1443 kg, was 84 percent
of the total bass standing crop, while the largemouth bass standing crop, 272
kg, made up the other 16 percent. Expressed as a function of surface area
during fall, the smallmouth bass population and standing crop was 13.0
fish/ha and 2.03 kg/ha, respectively, while the largemouth bass population
and standing crop was 3.2 fish/ha and 0.38 kg/ha (Table 7).
The 1974 year class made up 73 percent of the 1976 smallmouth bass fall
population, whereas the same year class of largemouth bass made up only 9
percent of the population of this species (Table 8). Fluctuations in
strengths of year classes have been attributed to environmental conditions
such as wind, food, water temperature, and water level fluctuation during egg,
fry, and finger! ing stages (Forney 1972; Latta 1963; Summerfelt 1975; Kramer
and Smith 1962; von Geldron and Mitchell 1975). In view of the abundance in
1976 of smallmouth bass of the 1974 year class, it can be assumed that small-
mouth bass produced a large fingerling crop during 1974. However, largemouth
bass made up 81 percent of the 628 finger! ings seined in 1974 (A. A. Elser,
Montana Department of Fish and Game, unpublished data). This large apparent
change in abundance suggests either that larnemouth bass had a much higher
mortality rate than smallmouth bass between the fingerling and yearling
stages (largemouth bass made up only 11 percent of .the yearling bass seined
during 1975) or that fingerling largemouth bass were more vulneraole to the
collecting gear than fingerling smallmouth bass (Table 9). The 1976 fall
population estimate for the 1974 year class consisted of 3 percent largemouth
bass and 97 percent smallmouth bass. The mortality pattern for the 1973 year
class was similar to that of the 1974 year class. The 461 fingerlings seined
during 1973 were 88 percent largemouth bass and 12 percent smallmouth bass
(A. A. Elser, Montana Department of Fish and Game, unpublished data) whereas
the 1976 fall population estimate of the 1973 year class consisted of 10 per-
cent largemouth bass and 90 percent smallmouth bass (Table 8). A greater
mortality of age-2 and older largemouth bass compared with that of smallmouth
bass may also contribute to the dominance of smallmouth bass in the older
bass populations. Survival of both largemouth bass and smallmouth bass finger-
lings from fall 1975 to fall 1976 was similar; 36 percent of the fingerlings
seined in 1975 were smallmouth bass while 31 percent of the yearlings seined
(Table 9) and 44 percent of the fall population estimate of yearlings in
1976 were smallmouth bass (Table 8).
Mortality
During spring 1976, 1,551 age-2 and older smallmouth bass were marked,
and 2,068 were captured during the. fall; 11.4 percent of which had marks.
The resultant estimate for the spring age-2 and older smallmouth bass popula-
tion in the entire Tongue River Reservoir was 13,549 (11,896-15,202) fish
(Table 10). The fall population estimate of age-2 and older smallmouth bass
(7,695) was 43 percent smaller than the sprina estimate. Total summer mor-
tality of age-2 and older smallmouth bass, estimated from a decrease in
marked fish from spring to fall was 40 percent (Table 11).
-------
TABLE 7. POPULATION AND STANDING CROP ESTIMATES FOR AGE-1 AND OLDER
SMALLMOUTH BASS AND LARGEMOUTH BASS IN THE TONGUE RIVER RESERVOIR,
FALL 1976. (Numbers are expressed as a function of
shoreline length and surface area at spring (1043.7 m)
and fall (1039.4 m) elevations. The 95i confidence
intervals are in parentheses.)
Smallmouth
Bass
Largemouth
Bass
Population Estimate
Number/km of Shoreline
Spring Elevation
Fall Elevation
Number/hectare
Spring Elevation
Fall Elevation
Standing Crop Estimate
kg/km of Shoreline
Spring Elevation
Fall Elevation
kg/hectare
Spring Elevation
Fall Elevation
9203
(7200 - 11206}
154
(121 - 188)
229
(179 - 279)
7.2
(5.6 - 8.8)
13.0
(10.1 - 15.8)
1443
(1129 - 1756)
24.2
(18.9 - 29.5)
37.0
(28.1 - 43.7)
1.13
(0.88 - 1.38)
2.03
(1.59 - 2.47)
2296
(1282 - 3310)
39
(22 - 56)
57
(32 - 82)
1.8
(1.0 - 2.6)
3.2
(1.8 - 4.7)
272
(152 - 392)
4.6
(2.5 - 6.6)
6.8
(3.8 - 9.8)
0.21
(0.12 - 0.31)
0.38
(0.21 - 0.55)
21
-------
ro
TABLE 8. AGE STRUCTURE OF THE BASS POPULATIONS AND STANDING CROPS
IN THE TONGUE RIVER RESERVOIR, FALL 1976.
Smallmouth Bass
Age
1
2
3
4
5
6
7
Total
Year
Class
1975
1974
1973
1972
1971
1970
1969
Fish
No.
1508
6700
818
62
98
17
9203
%
16.4
72.8
8.9
0.7
1.1
0.2
Weight
kg
65
1009
235
37
76
19
1441
%
4.5
70.0
16.3
2.6
5.3
1.3
Largemouth Bass
Fish
No.
1954
199
89
18
33
6
6
2305
%
84.8
8.6
3.9
0.8
1.4
0.3
0.3
Weight
kg
74
73
46
17
41
9
11
271
%
27.3
26.9
17.0
6.3
15.1
3.3
4.1
-------
TABLE 9. FISHES CAUGHT BY ALONGSHORE SEINING IN THE TONGUE RIVER
RESERVOIR, 1975 AND 1976. (Number of seine hauls
is shown in parenthesis.)
Species and
Total length (mm)-/
Smallmouth bass
< 100
100-200
Largemouth bass
< 100
100-200
Others
Total
1975
August 14 -
September 5
(62)
No. per
haul %
4.0 9.6
2.5 6.0
7.0 16.7
0.3 0.8
28.2 67.1
42.0
1976
July 30 -
September
(60)
No. per
haul
2.1 3
0.4 0
6.4 10
0.9 1
52.1 84
61.9
5
%
.3
.7
.4
.4
.2
Bass < 100 mm long were primarily young of the year; those 100-200 mm
long were primarily yearlings.
23
-------
TABLE 10. PETERSEN CATCH STATISTICS FOR ESTIMATING SMALLMOUTH BASS
POPULATIONS IN THE TONGUE RIVER RESERVOIR, SPRING 1976.
(Data are for age-2 and older right pelvic fin
clipped fish marked in the spring and recaptured
in the fall. The 95% confidence intervals
are in parenthesis.)
Total fish Total fish Total marked
marked captured fish captured
Area A 23 46 1
Area B 431 1212 120
Area C 1097 810 115
Total 1551 2068 236
Population
Estimate 13,549 (11,896-15,202)
24
-------
Movement and seasonal population changes of smallmouth bass, 1976
During the spring and early summer 1,709 smallmouth bass two years and
older were handled during three electrofishing runs along the shoreline in
areas B and C. The population estimates for area C and B were 4,063 and
2,048 bass (Table 12).
During the spring and early summer 454 and 1,097 age-2 and older small-
mouth bass were marked in areas A and B combined and C, respectively. During
the fall, the estimated number (538) of right pelvic fin clipped fish in
areas A and B combined increased, while the number in area C (398) signifi-
cantly decreased (Table 11). An estimated movement of 980 fish out of area
C and into areas A and B combined (40.0 percent of the spring smallmouth bass
population in area C after mortality) would account for the increased number
of marked fish in areas A and B combined. This was calculated by allowing for
mortality and assuming similar behavior between marked and unmarked fish.
This resulted in a population of 1,469 age-2 and older fish in area C which
is 1,005 less than the fall estimate. When the spring estimate for area B,
minus mortality, is summed with the 980 fisn from area C the result is 2,216
fish, 2,679 less than the fall estimate of areas A and B combined. This
suggests 3,684 smallmouth bass were added to the fall population from area A.
When accounting for mortality, 6,105 fish is the estimate for the number of
age-2 and older smallmouth bass in area A during the spring. This compares
to the estimated 7,438 fish in area A during the spring which was computed by
subtracting the spring estimates for areas B and C from the spring estimate
for the entire reservoir. This figure may be slightly high because the spring
smallmouth population in area B may have been underestimated due to the small
number of recaptures in the larger length interval (Table 12). Nevertheless,
apparently sufficient numbers of smallmouth bass were present in area A
during the spring to account for the increase in the fall population.
In summary, the distribution of recaptured marked fish indicated a net
movement (spring to fall) of 1,005 and 2,679 smallmouth bass out of area A
and into areas C and B, respectively; a small percent of the 2,679 fish re-
mained in area A (Table 10). During the same period, a net 980 fish moved
out of area C and into area B. This, along with a 39.7 percent mortality,
accounts for the 139 percent increased population in area B and the 39 per-
cent reduced population in area C.
Tagged smallmouth bass also demonstrated a pattern of downstream move-
ment with declining water levels. Of nine smallmouth bass tagged in areas
A and B during the spring and summer of 1976 and recaptured durina the fall
of the same year, five moved downstream toward the dam, one moved upstream,
and three showed no significant movement (Fig. 5). Of 50 fish tagged in
these two areas during the fall and recaptured the same season, 16 moved
downstream, one upstream, and 33 showed no significant movement. Four fish
moved out of area A into area B, and two moved from area B into area C
(Figures 5 and 6). Overall, average detectable movement downstream and up-
stream was 2.0 and 2.5 km, respectively.
25
-------
TABLE 11. CALCULATIONS FOR SUMMER MORTALITY OF AGE-2 AND OLDER SMALLMOUTH
BASS, 1976. (Fish were marked in the spring and
recaptured in the fall.)
Area
A + B
C
Total
§/ cb/
454 1175
1097 773
1551
R-/ R/C
121 0.1030
115 0.1608
Number
Remaining
(R/C) X N
538
398
936
Mortality
l-(936/1551)
0.397
M = Number age-2 and older fish marked in spring.
C = Total number of age-2 and older fish captured in fall.
c/
R = Number of marked fish captured.
26
-------
TABLE 12, SCHUMACHER AND ESCHMEYER CATCH STATISTICS FOR AGE-2 AND OLDER SMALLMOUTH BASS
IN TWO AREAS OF THE TONGUE RIVER RESERVOIR, 1976.
(95% confidence intervals are in parenthesis.)
Period
5/27-6/14
6/15-7/3
7/4-7/20
Population
Estimate
111-180 mm Total Length Interval
Ct Rt Mm Mt
39 -- 39 0
160 3 157 39
159 20 139 196
1573 (1381-1826)
101-140 mm Total Length Interval
Area B
181-420 mm Total Length Interval
Ct Rt Nm Mt
27 0 27 0
26 0 26 27
47 6 41 53
475 (266-2181)
Area C
141-411 mm Total Length Interval
Period
5/27-6/14
6/15-7/3
7/4-7/20
Population
Estimate*
Ct
67
167
77
1483
Rt
--
9
19
Nm
67
151
66
Mt
0
67
218
(1170-2452)
Ct
163
319
458
2580
Rt Nm
0 163
19 291
81 377
(2460-2713)
Mt
0
163
454
* Corrected for 6.38% age-1 fish in catch.
Ct = Total fish captured.
Rt = Recaptured fish.
Nm = Number marked less removals.
Mt = Marked fish at large.
-------
Fish No.
1
2
Unnumbered
Date Date
Tagged Recaptured
5/30 9/15
6/14
summer
8/16
fall
SCALE
Figure 5. Movement within the Tongue River Reservoir of smallmouth
bass marked in the spring or summer and recaptured during
the summer or fall, 1976.
28
-------
SC»LE
0. CIV
Figure 6. Movement of smallmouth bass marked and recaptured in the
Tongue River Reservoir during fall (8/30 - 9/16), 1976.
(Number indicates more than one fish moved in a similar
direction.)
29
-------
Only four fish were recaptured in the fall which had been tagged in area
C in the spring or summer of 1976. None of these four fish moved signifi-
cantly from their tagging location (Figure 5). Only three of 11 fish, which
were tagged in area C during the fall and recaptured the same season, showed
measurable movement. One moved across the reservoir and the other two moved
an average of 0.6 km downsteam (Figure 6).
30
-------
SECTION VII
DISCUSSION
Age and growth
Growth of smallmouth bass in the Tongue River Reservoir was above aver-
age for fish of this species in a northern water body. Though smallmouth bass
growth was slower than in Minnesota it was faster than for fish of this
species in Wisconsin (Bennett 1938), Maine (Watson 1955), or Michigan (Latta
1963). The length-weight relationship for smallmouth bass in the Tongue
River Reservoir was similar to those for fish from Clear Lake, Wisconsin
(Marinac 1976) and Tadenac Lake, Ontario (Turner and MacCriramon 1970).
Growth of largemouth bass in the Tongue River Reservoir was faster than
that reported for this specie in Wisconsin (Bennett 1937), Minnesota (Kuehn
1949), or Montana (Brown 1952; Brown and Logan 1960). Lengths of older large-
mouth bass were similar to those reported by Tharratt (1966) in California.
Largemouth bass in the reservoir were heavier at similar lengths than those
in Beaver and Bull Shoals Reservoirs, Missouri (Bryant and Houser 1971) and
similar to those in Gladstone Lake, Minnesota (Maloney et al. 1962).
Excellent growth of basses in the Tongue River Reservoir may be correlated
to nutrient levels, low population densities, fluctuating water levels, and
for smallmouth bass, recent exploitation of a new habitat. Whalen and Leathe
(1976), who studied primary and secondary production in the reservoir, con-
cluded that the reservoir is a moderately productive system. Cooper et al.
(1963) observed that growth of largemouth bass increased when densities de-
creased in a Pennsylvania pond. The largemouth bass population in the Tongue
River Reservoir research represents only 3 percent of the mean (by surface
area) for 170 U.S. reservoirs, whereas the smallmouth bass population equaled
the average for 45 reservoirs (Jenkins 1975). Heman et al. (1969) reported
that increased growth of largemouth bass coincided with drawdown of a central
Missouri reservoir. Summer drawdown, after spring runoff, reduced the sur-
face area of the Tongue River Reservoir by 44 percent from spring to fall
1976.
Growth (total length at annulus) of smallmouth bass was faster in areas
A and B than in area C, possibly because forage fish were more abundant in
A and B. Results of alongshore seining (which collected fish generally
smaller than 150 mm in length) indicated that area A had the highest density
of fish (64.6 fish per haul), whereas area C had the lowest (46.7 per haul;
Table 5). As summer progressed, surface area decreased faster in areas A and
B than in C, concentrating fish more in A and B. Areas A and B had a larger
percentage of low-gradient littoral zones which usually supported a higher
concentration of forage fish than did the steep-gradient areas common in area
31
-------
C. Length-weight relationships and condition factors (Table 4) also indi-
cated the superior condition of fish in areas A and B.
Reproductive success
Smallmouth bass finger!ings appeared to be three times more abundant in
area C than in area B, while smallmouth bass fingerlings were never collected
in area A (Table 2). This can possibly be related to turbidity levels in the
three areas; area A had the highest turbidities, C the lowest and B inter-
mediate. Cleary (1956) noted that streams which remained turbid for long
periods seldom produced smallmouth bass fingerlings or good smallmouth bass
fishing. Area A remained turbid throughout the year, but turbidities in areas
B and C decreased from spring to fall. Walters (1974) suggested that unsuc-
cessful smallmouth bass reproduction in Missouri impoundments was related to a
lack of suitable substrate. Since area A was not completely devoid of pebbles
and cobbles (14 percent of the dominant shoreline substrate), lack of suit-
able substrate can probably be ruled out as the major factor limiting small-
mouth bass reproduction in this area of the reservoir.
Largemouth bass fingerlings were found in all three areas of the reser-
voir but were 3.1 and 14.1 times more abundant in areas B and C, respectively,
than in area A (Table 2). Buck (1956) demonstrated a similar inverse rela-
tionship between levels of turbidity in farm ponds, and reproductive success
of largemouth bass. Apparently, largemouth bass can reproduce, although not
prolifically, in higher turbidities than can smallmouth bass.
Population and standing crop
Although largemouth bass were initially stocked in 1964 and smallmouth
bass were not documented in the Tongue River Reservoir until 1972, smallmouth
bass dominated the bass population (80 percent smallmouth bass) and standing
crop (84 percent smallmouth bass) during the fall of 1976. This relative
abundance is just the opposite of the average in 26 U.S. reservoirs which con-
tained largemouth (66 percent), spotted (22 percent), and smallmouth bass (12
percent) (Jenkins 1975). Bennett and Childers (1957) and Walters (1974)
noted a preponderance of largemouth bass over smallmouth bass when they oc-
curred together in a pond environment. These differences in abundance may
be attributed to inter-specific competition and/or to greater habitat suit-
ability for one species during any one or more of the life stages.
Bass habitat in the Tongue River Reservoir more closely resembles that
in smallmouth bass lakes described by Belding (1926) and Hubbs and Bailey
(1938), than that of largemouth bass lakes described by Carlander (1975).
Smallmouth bass lakes were characterized by a surface area of over 40 ha,
clear water, scanty vegetation, large areas of rock and gravel, a depth not
less than 6 to 9 m, and moderate summer temperature. The Tongue River Reser-
voir meets these specifications in areas B and C. Area A, the inflow section,
does not meet the criteria for water clarity, large areas of rock and gravel,
and (except during spring and early summer) depth. Area A was inhabited by
smallmouth bass in spring and summer but moved into area B when water levels
declined in late summer. Largemouth bass habitat in northern lakes is
32
-------
typified by shallow weedy areas. Due to extreme water level fluctuations,
aquatic vegetation is lacking in the Tongue River Reservoir, and terrestrial
vegetation is flooded only for a short period in early summer. Rideout and
Oatis (1975) noted a change in species composition in Quabbin Reservoir, a
fluctuating impoundment in Massachusetts, similar to that observed in the
Tongue River Reservoir. Largemouth bass dominated the catch in Quabbin Reser-
voir during the 15th to 24th year of impoundment but smallmouth bass in-
creased markedly in abundance and became heavily dominant from the 25th
through 34th year. The largemouth bass population remained almost unchanged
during this period. They attributed this change in relative abundance to the
preference of smallmouth bass for the cool, clean water and rubble shoreline
habitat and to their greater tolerance of water level fluctuations. They
also noted that smallmouth bass were never stocked in the reservoir and pro-
bably entered from an adjacent pond. This most probably also occurred in the
Tongue River Reservoir.
Rawstron and Hashagen (1972) proposed that competition between smallmouth
and largemouth basses may have increased relative abundance of smallmouth bass
in Merle Collins Reservoir, an irrigation impoundment in California. They
implied that competition had its greatest influence during the first year of
life. Competition during the first summer of life was not the cause of a
comparatively much higher mortality of largemouth bass than smallmouth bass
which occurred after the first fall of life and probably before the second
fall.
Perhaps the major factor contributing to the observed relative abundance
in the Tongue River Reservoir is that preferred smallmouth bass habitat
(rubble and gravel shoreline) was abundant, while preferred largemouth bass
habitat (shallow areas with aquatic vegetation) was almost nonexistent. This
may explain the much greater mortality of largemouth bass than smallmouth
bass from the fingerling to yearling stage. Even though fry and fingerling
production was probably high in 1974, the limited habitat available for year-
ling largemouth bass (shallow weedy areas) may have prevented their survival
in representative numbers. Perhaps this need for aquatic vegetation by large-
mouth bass can be correlated to the observation by Rideout and Oatis (1975)
that smallmouth bass are more tolerant to water fluctuations than largemouth
bass.
Habitat suitability rather than interspecific competition is probably
the controlling factor for the observed bass abundance in the Tongue River
Reservoir. Competition may be a significant factor only because largemouth
bass must compete in habitat less than optimum for its needs. Munther (1970)
documented that smallmouth bass seek rocky areas during winter which provide
hiding areas beneath the substrate. In the Tongue River Reservoir there were
concentrations of smallmouth bass over such areas during fall. Perhaps
largemouth bass have similar needs that are tied to vegetation rather than
substrate. This may be especially critical during the first winter of life.
The fact that largemouth bass was the dominant bass specie in other environ-
ments (Jenkins 1975; Bennett and Childers 1957; Walters 1974) also suggests
that habitat suitability is of prime concern.
33
-------
Food did not appear to be a limiting factor for either species. Age and
growth of all ages of both species of bass was excellent.
Survival of largemouth bass and smallmouth bass of the 1975 year class
from the fingerling to yearling stages was similar. Possibly largemouth
fingerling production in 1975 did not greatly exceed the concurrent carrying
capacity for yearlings. If so, mortality factors may have operated equally
for both species. Large withdrawals of water during the fall of 1975 (to
facilitate dam repairs) resulted in low water levels which may have affected
relative survival of the 1975 year class.
Mortality
The total estimated summer mortality (40 percent) of age-2 and older
smallmouth bass in the Tongue River Reservoir was close to the range of
annual total mortalities (43 to 66 percent) for six studies cited by Coble
(1975). Clady (1977) believed that most of the annual natural mortality of
age-3 to age-4 bass occurred during the period of rapid growth (June through
August). He observed a natural mortality of only 23.8 percent for smallmouth
bass from September to May, whereas annual natural mortality was 60 percent.
If total annual mortality of smallmouth bass in the Tongue River Reservoir
falls within the range cited by Coble (1975), the pattern of higher summer
than winter mortality was similar to that found by Clady (1977). Perhaps the
habit of smallmouth bass of becoming inactive beneath the substrate at tem-
peratures lower than 7.8 C (Munther 1970) keeps winter mortality low. This
period of winter smallmouth bass inactivity was evident in the Tongue River
Reservoir as only one smallmouth bass was known to have been caught by fisher-
men during two winters of creel census (A. A. Elser, Montana Fish and Game
Department, unpublished data).
Movement and seasonal population changes of smallmouth bass
Tag returns indicated a downstream movement of smallmouth bass during the
late summer and fall. This movement coincided with a reduction in surface
area particularly impacting habitat in upstream areas. Surface area declined
by 45, 30, and 20 percent from spring to fall in areas A, B, and C, respec-
tively. Also, much of the remaining surface area in area A was shallow mud
flats not suitable for smallmouth bass. Much of the observed movement of
bass may have been in response to deteriorating habitat. Fajen (1962) noted
that smallmouth bass were less faithful to a particular home range, usually
one pool, in two Ozark streams when shifting gravel threatened the security
of the pool.
Population estimates and distribution of fin-clipped fish indicates that
not only does water level reduction result in movement due to elimination of
habitat (area A) but also causes movement in a section with habitat less
affected by water levels (area C).
Possible reasons for a net movement of fish out of area C and into area
B are greater competition for food due to a lower forage fish density (and
the smaller percent of shoreline areas where forage fish, congregate), and
habitat selection for areas of greater forage availability. Habitat selection
34
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for a suitable substrate for the winter dormancy period may also be involved.
Munther (1970) observed that smallmouth bass preferred a broken rock substrate
in the Middle Snake River, Idaho and Oregon. Smallmouth bass rested on or
below the rock substrate at night but did not use a rounded cobblestone or
sand substrate. High concentrations, of smallmouth bass over a rock and
boulder substrate with a large amount of interstitial space were observed in
the Tongue River Reservoir, especially during the fall. In the laboratory,
Munther saw that most smallmouth bass stayed below the rock substrate when
water temperatures were 6.7 to 7.8 C. Munther also noted that smallmouth
bass formed fall and winter concentrations in pools at least 3.6 meters deep.
Area B in the Tongue River Reservoir has large amounts of broken rock sub-
strate in the deeper water which perhaps is being preferentially selected in
the fall.
35
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SECTION VIII
POTENTIAL IMPACTS OF SURFACE COAL MINING
Surface run-off water in the immediate vicinity of the Decker Mine, and
subsurface water resulting from disturbing the aquifer, are collected within
the Mine in a sedimentation pond system. The sedimentation pond water is re-
used for dust control and for irrigation onto reclaimed mine spoils; excess
water is pumped onto the flood plain of the Tongue River at the upper end of
the Reservoir.
Turbak et al. (in press) have studied the quality of the settling pond
water, including the heavy metals arsenic, cadmium, lead, mercury, and se-
lenium, and data are reported for the mine effluent water for five dates from
July 1976 to April 1977. Concentrations ranged from 1.1 to 1.9 yg/liter for
arsenic and <1 to <5 for cadmium, both of these below the criteria published
by EPA (1977). Reported concentrations for lead were <0.01 to <0.1 mg/liter
and for selenium were <0.03 to 0.5 yg/liter. No specific numerical criteria
for these two metals have been provided by EPA (1977); although it is rec-
ommended that acceptable concentrations be based on 96-hr LC5Q values for
sensitive resident aquatic species. The reported concentrations for mercury,
0.11 to 0.87 yg/liter, are in excess of the EPA (1977) criterion of 0.05 yg/
liter, however these criteria are for receiving waters, not the discharge
itself.
Additional data on mercury concentrations in the mine effluent between
October 1975 and August 1976 have been reported by Phillips (1978); based on
reported analyses performed by the Montana Department of Health and Environ-
mental Sciences, mercury concentrations ranged between 1.2 and 335 yg/liter.
Phillips also reported concentrations of mercury in the Tongue River below
the mine effluent at this same time as ranging from <0.2 to 2.3 yg/liter.
The most extensive data available on the water chemistry of the Tongue
River in the region of the Decker Mine have been reported by Whalen (1979),
who studied the chemical limnology of the reservoir. Whalen has considered
the potential impact on the river and reservoir of the mine discharge, and
has extrapolated from his data to consider also the impact from the proposed
expanded mine areas. Water chemistry from Whalen are presented in Tables 13
and 14. Whalen has calculated the average annual discharge of the mine to be
less than 0.1 percent of the Tongue River flow at point of receipt. On the
basis of the values obtained from the chemical parameters measured both in
the receiving water and present mine discharge, Whalen has concluded that the
impact of the mine water discharge on the Tongue River is and will be negli-
gible for those parameters measured, with the caveat that an unusually dry
36
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TABLE 13. AVERAGES AND RANGES (IN PARENTHESES) OF SOME CHEMICAL AND
PHYSICAL PARAMETERS OF THE TONGUE RIVER RESERVOIR, NOVEMBER 1975
TO NOVEMBER 1976.-/
Parameter
Ca (meq/Ji)
Mg (meq/£)
Na (meq/£)
K (meq/5,)
Total alkalinity (meq/£ CaC03)
SOt,' (meq/£)
Cl" (meq/£)
Si02 (mg/£)
NH3-N (yg/£)
N03-N (yg/A)
N02-N (yg/£)
PO^-P (yg/A)
Total -P (ug/£)
Spec. cond. (ymhos/cm @25 C)
Station I-/
Reservoir
Above Dam
2.86
(1.26-3.80)
2.99
(0.96-4.29)
1.25
(0.34-1.92)
0.10
(0.04-0.16)
3.70
(1.92-4.70)
3.44
(0.81-5.18)
0.08
(0.03-0.12)
5.6
(1.4-11.8)
24
(0-236)
27
(0-204)
3
(0-20)
10
(0-100)
40
(16-144)
660
(246-929)
Station 2
Mid-Reservoir
2.79
(1.30-4.31)
2.91
(0.84-4.59)
1.23
(0.29-22.7)
0.10
(0.04-0.16)
3.59
(1.68-5.62)
3.35
(0.66-6.24)
0.08
(0.03-0.13)
5.7
(1.1-10.0)
18
(0-142)
26
(0-187)
3
(0-10)
8
(0-77)
41
(10-109)
645
(221-1032)
Station 3
Reservoir
Upper region
2.81
(1.09-3.63)
2.99
(0.79-3.81)
1.26
(0.28-2.02)
0.10
(0.03-0.13)
3.69
(1.56-4.71)
3.37
(0.54-5.27)
0.08
(0.03-0.12)
6.8
(2.5-13.0)
21
(0-220)
27
(0-47)
3
(0-10)
12
(0-27)
71
(37-260)
654
(197-948)
37
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TABLE 13. Continued.
Parameter
pH
Turbidity (JTU)
Temperature (C)
Dissolved Oxygen (mg/Ji)
Station I-/
Reservoir
Above Dam
8.4
(7.5-8.9)
7.3
(1.9-24)
10.6
(1.2-23.5)
8.5
(0.2-13.4)
Station 2
Mid-Reservoir
8.5
(7.5-9.0)
8.6
(1.3-32)
10.9
(1.2-23.8)
9.3
(0.8-19.6)
Station 3
Reservoir
Upper region
8.4
(7.9-9.0)
20.3
(5.5-62)
11.4
(1.2-23.9)
10.1
(2.5-17.6)
-/From Whalen (1979).
-Station locations shown in Figure 2.
38
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TABLE 14. AVERAGE VALUES OF SELECTED PARAMETERS MEASURED IN THE DECKER MINE
DISCHARGE WATER AND IN THE TONGUE RIVER ABOVE AND BELOW THE MINE
DISCHARGE, JUNE 1975 TO NOVEMBER 1976, (All parameters
expressed as mg/liter unless otherwise noted.)
Parameter
PH
Dissolved oxygen
Spec. Cond. (ymhos/cm @ 25 C)
Turbidity (JTU)
Temperature (C)
Organic carbon
C03
HC03
Total alkalinity (as CaC03)
Si02
Fe
Cl
F
SO,
Ca
Mg
Na
K
N02-N (v-g/a)
N03-N (yg/&)
Tongue River
above mine
8.6
10.1
693
15
14.7
4.9
4
238
202
7.4
0.028
2.8
0.33
166.4
61.2
37.8
30.5
3.9
3
31
Mine discharge
8.5
9.8
1498
18
14.9
5.2
12
597
509
13.0
0.021
6.8
1.22
295.1
33.1
42.4
253.3
7.7
37
287
Tongue River
below mine
8.4
9.8
696
14
14.7
5.0
4
240
203
7.4
0.024
2.7
0.33
166.4
61.0
37.8
30.4
3.9
3
30
39
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TABLE 14. Continued.
Tongue River Tongue River
Parameter above mine Mine discharge below mine
NH3-N (vg/fc) 16 282 16
Total Kjehldahl nitrogen (yg/A) 326 674 333
P04-P (ygA) 20 6 18
Total-P (yg/£) 62 38 60
Sodium absorption ratio (SAR) 0.78 6.88 0.78
-/From Whalen (1979).
40
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water year could alter this prediction. It should be noted that Whalen did
not report concentrations of heavy metals.
The present study has concerned itself with the movement, age and growth,
and life histories of largemouth bass and smallmouth bass in the Tongue River
Reservoir. Any effect on these fishes as a result of altered water chemistry
within the reservoir is not apparent from the results of the study. With the
intensification of coal mining planned for this area, we believe that addi-
tional information is needed to plan for adequate safeguards to protect the
aquatic biota of the Tongue River drainage system. Information is now avail-
able which will provide baseline data against which data from future studies
may be compared.
An incremental increase in recreational use of the river and reservoir
will undoubtedly result from expanded mining or coal conversion operations.
These waters are currently subject to light fishing pressure but a human
population influx could alter use patterns and fishing intensity.
In summary, we believe the following aspects should be studied in some
detail in the near future:
1. Changes in water quality of the reservoir (salinity, turbidity, temper-
ature, nutrient loading, heavy metal loading).
2. Changes in water quantity (dewatering for offstream storage and use, and
resultant reductions in reservoir storage levels), particularly in area
A.
3. Changes in fishing pressure and recreational use (including conflicts
among various user types).
41
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Coble, D. W. 1975. Smallrnouth bass. Pp. 21-33 in R. H. Stroud and H.
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45
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-80-045
3. RECIPIENT'S ACCESSION NO.
4, TITLE AND SUBTITLE ...
Environmental Effects of Western Coal Surface Mining
3art VI - Smallmouth Bass and Largemouth Bass in the
Tongue River Reservoir, Montana, 1975-76
5. REPORT DATE
May 1980 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Russell F.
Penkal and Richard W. Gregory
I. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
ooperative Fishery Research Unit
Montana State University
Bozeman, Montana 59717
10. PROGRAM ELEMENT NO.
1NE625. EHE625
11. CONTRACT/GRANT NO.
R803950
12. SPONSORING AGENCY NAME AND ADDRESS
environmental Research Laboratory--Duluth, Minnesota
Office of Research and Development
J.S. Environmental Protection Agency
Duluth, Minnesota 55804
13. TYPE OF REPORT AND PERIOD COVERED
Final
14. SPONSORING AGENCY CODE
EPA/600/03
15. SUPPLEMENTARY NOTES
16. ABSTRACT
opulation parameters of small mouth bass (Micropterus dolom-ieui] and largemouth bass (M.
salmoides] were studied during 1975 and 1976, before expansion of surface coal mining
adjacent to the Tongue River Reservoir in southeastern Montana. Reproductive success, a
determined by alongshore seining, varied in different areas of the reservoir and may be
correlated to turbidity. Population estimates were obtained at night during spring and
fall 1976 with boat electrofishing gear. For yearling and older smallmouth bass the fal
copulation of 13.0 fish/ha and the standing crop of 2.03 kg/ha represented 80 and 84
percent of the totals for basses in the reservoir. The largemouth bass population and
standing crop during fall 1976 was 3.2 fish/ha and 0.32 kg/ha. The dominance by small-
nouth bass of all year classes for both species except age-1, was attributed to a much
n'gher mortality of under-yearlings among largemouth bass. This higher mortality of
argemouth bass may be correlated to a lack of shoreline vegetation in the reservoir.
ummer mortality of age-2 and older smallmouth bass, estimated from the reduction in
numbers of marked fish, was about 40 percent. Smallmouth bass growth and condition were
better in the upper than lower end of the reservoir; the difference may be due to forage
Fish availability. Growth and length-weight relationships were above average for both
pecies when compared with basses in other northern waters, indicating no noticeable
effect from nearby surface coal mine operations at the time of the study.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
dilution
Effects from mining
Smallmouth bass
Largemouth bass
Foxicity
Energy development
Fishery effects
Population estimates
Aquatic biology
Reservoirs
68 D
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
ASSTFTED
20. SECURITY CLASS (This page}
UNCLASSIFIED
21. NO. OF PAGES
54
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
46
YIJS GOVERNMENT PBINTING OFFICE 1980-657-146/5659
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