A Summary of fish populations investigations in the Poplar River drainage : July 1, 1975 through March 31, 1976

MONTANA DEPARTMENT OF FISH AND GAME
HELENA, MONTANA

A SUMMARY OF FISH POPULATION INVESTIGATIONS
IN THE POPLAR RIVER DRAINAGE 1/
JULY 1, 1975 THROUGH MARCH 31, 1976^

ABSTRACT

Fisheries studies were conducted on the Poplar River to acquire base-
line information needed to evaluate the impacts associated with development
of a coal -fired electrical generation complex on the East Fork Poplar River
Walleye was the dominant game fish present. Population estimates for wall-
eye (excluding young-of-the-year) conducted by the mark-and-recapture at
two stations revealed 178 walleye per mile in the East Fork and 297 walleye
per mile in the main river at the confluence of the East and Middle Forks.
Other sport fishes consisted primarily of northern pike, smallmouth bass,
and goldeye. Reproductive success of sport fishes and abundance of forage
species was determined at nine stations. A total of 1,071 fish were marked
to determine the extent of movement for selected sport fishes.

The Poplar River is a low-gradient, sinuous prairie stream origi-
nating in Saskatchewan. It has a drainage area of 200 square miles. The
natural flow pattern is characterized by high spring flows and low summer
flows. The physical channel consists primarily of large, deep pools and
shallow riffles. Gravel is the dominant streambed material where scouring
action occurs; sand, silt, and mud bottoms characterize the large pools.
The relatively sparse streambank vegetation consists of grasses, wild rose,
and snowberry. Flood plain vegetation consists of grasses and silver sage-
brush, except in the extreme lower reaches of the drainage where a variety
of shrubs and cottonwoods are abundant.

In 1974, the Saskatchewan Power Corporation announced plans to con-
struct a coal-fired electrical generation complex on the East Fork Poplar
River approximately 2 miles north of the U. S. boundary. The proposed
development consists of four 300 megawatt (MW) units with a total possible
generating capacity of 1,200 MW. The plant, if fully developed, would con-
sume approximately 7 million tons of lignite coal per year. The 1,200 MW
complex would require about 1,200 acres of water surface for cooling pur-
poses and approximately 11,000 acre-feet of water per year for replacement
of natural and induced evaporation.

1/ Funding assistance was provided by the Environmental Protection Agency.

INTRODUCTION

Montana State Library

3 0864 1006 4911 3

A proposed plan for trans -boundary water apportionment of the entire
Poplar River drainage has been prepared by the Poplar River Task Force. The
consumptive needs of this development will exceed the total annual discharge
of the East Fork. Development of a cooling reservoir will rely on filling
from spring run-off which will drastically reduce flows and alter flow regimes.
The recommended flow apportionment for the East Fork only assures delivery of
15 percent of the mean annual flow. It is projected that additional water in
the form of spills will be provided in 16 of 44 years. Full development will
require that supplemental water be diverted from other sources into the East
Fork. The Middle and West Forks have been included in plans for supplementing
the industrial water supply of the East Fork. The proposed flow apportionment
would provide that a minimum of 60 percent of the Middle Fork and 50 percent
of the West Fork natural flow would be delivered to the United States.

The Poplar River Drainage is one of the better warm water stream fisheries
in Montana; however, it receives only limited recognition due to the relatively
sparse human population in the area. Walleye are the dominant game fish species
Northern pike are widespread in the drainage; and although not as abundant as
walleye, they contribute significantly to the creel, possibly due to their
higher catchability . Smallmouth bass, introduced in 1967 to supplement the fish
ery, are reproducing and appear to be establishing fishable populations in some
areas. Desirable-size goldeye are present in moderate numbers throughout the
system and contribute to the fishery. Forage fishes of numerous species are
abundant .

Although Montana contains many prairie streams, few provide a sport fish-
ery. While habitat in the Poplar River is of sufficient quality to maintain a
sport fishery, only a small difference in habitat separates this river from
numerous other streams which support only non-game species.

Very little information exists regarding the fish population of the Poplar
River and its tributaries. Investigations were implemented in 1975 to acquire
baseline information needed to evaluate the impact of the Saskatchewan Power
Corporation Project on the fish population of the Poplar River Drainage.

FISH POPULATION

Distribution and Abundance: Nine stations as indicated on Figure 1 were
sampled with an alternating current boom-shocker in the fall of 1975, The pri-
mary objective was to obtain information on the distribution and abundance of
sport fishes. These findings are summarized in Table 1. Due to differences
in sampling effort, water conditions, and length of stream sampled, the catches
at the various stations are not directly comparable.

Goldeye, although not designated as a game fish by Montana law, were in-
cluded in the sport fish catch due to their use by some anglers. Goldeye were
taken at all sampling locations except the upper East Fork. The relative abun-
dance of goldeye was considerably higher than indicated in Table 1 as there was
low efficiency in collecting goldeye stunned during electrof ishing .

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Saskatchewan Power
Corporation Dam

MONTA NA

* East Fork Upper

Middle ForkI ~i

Upper

{vROfA CAN RDA)

Middle Fork Lower*

Confluence East
and Middle Forks *^

Main River Chabot's *

* East Fork Lower

9 SCOBEY

* Paulson Slab

West Fork *

Crowley Slab *

Main River Lower

Figure 1. Map of the Poplar River
identifying the location
of fish population sampling
stations which are indicated
by an asterisk .

iSSOURl R/^^

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labie 1. Total number and size (length in inches, weight in pounds) of sport fishes taken with an alternating current boom-shocker at nine
locations on the Poplar River, 1975.

1/

East Fork

Upper
(1 Sample)

East Fork

Lower
(4 Samples)

Middle Fork
Upper
(1 Sample)

Confluence East
and Middle Forks
(2 Samples)

Main River
Chabo t ' s
(1 Sample)

Main River
Paulson Slab
(1 Sample)

West Fork
(1 Sample)

Main River
Crowley Slab
(1 Sample)

Main River

Lower
(1 Sample)

bp .

No . L . Wt .

M.^ T Lit-
INO . L . WC .

INO . L . Wt .

M/-1 T Lit-

iNO t L , Wt .

Mi-i T LT*-
riO . L , Wl .

older

123 12.5 0.71

16 14.3 1.02

145 12.2 0.61

57 11.2 0.47

43 13.0 0.72

45 13.8 1.08

18 12.9 0.80

9 12.8 0.68

WE
Y-T

4 5.7 —

20 5.0
43 NA

5 4.2

13 4.4

10 4.5

4 4.8

8 5.4

4 5.4

4 5.0

la-
dder

H ^ J . D J . Jo

z zi . y z . 43

J 2U . J z , U2

1 TOD 1 ID
i IH . O 1 . ZJ

NP
Y-Y

7 11.3 0.33

16 10.0 0.21

7 10.1 0.24

8 10.0 0.21

SA

1 13.4 0.60

1 13.6 0.70

1 17.5 1.47

SMB
1+

older

4 7.5 C.27

7 8.2 0.33

3 7.7 0.28

6 8.0 0.32

SMB
Y-Y

5 3.2 0.02

1 3.1 0.02

GE

10 13.2 0.74

2 13.4 0.89

33 13.3 0.75

33 13.0 0.73

35 12.7 O.fil

19 13.5 0.80

14 12.1 0.57

20 11.9 0.51

^/ Abbreviations: V.T;, Walleye; N'P , Northern pike; S.A, Sauger; S>!E, Smallmouth bass; GE, Goldeye; Y-Y, young-of-the-year ; Sp . , species.

Walleye were the dominant game fish taken; however, numbers were low
at the upper East Fork station. Sampling in this area indicated walleye
adults do not commonly inhabit this stretch of river in appreciable numbers
as residents, but do utilize this portion and upstream segments for spawn-
ing. Turbid water conditions during sampling on the Middle Fork curtailed
sampling success. Walleye young-of-the-year were found throughout the en-
tire area sampled.

Catches for northern pike were relatively low. Northerns appeared to
be distributed throughout the system, but due to the small numbers taken
only limited information was obtained. The greatest numbers taken con-
sisted of young-of-the-year. Spring flows were above normal in 1975 which
may have provided better than average spawning conditions for northern pike.

Smallmouth bass were taken only in the West Fork and mainstem portions
of the drainage downstream from Scobey. In 1967, approximately 4,000 finger-
Ungs (2-inch) smallmouth were stocked to establish a population In addi-
tion, 150 yearlings (6-inch) were stocked in 1968. Most of the stocking was
conducted m the West Fork; however, releases were also made at the Paulson
Slab on the mam river. Most of the smallmouth collected were young-of-
the-year and yearlings. Indications are that the relatively few adults
present are spawning successfully and therefore the population should in-
crease significantly in the future when additional fish reach maturity.

During electrofishing operations an effort was made to collect only
fishes of significant sport value. However, in an effort to acquire broad
information on population composition, records were also maintained on all
species observed within the electrical sampling field. Information re-
corded m this manner did not include small individuals less than 6 inches
in length. As indicated in Table 2, the number of species taken increased
at downstream locations. Only white sucker, shorthead redhorse, and carp
were common throughout the drainage.

In an effort to obtain quantitative information on portions of the
drainage to be immediately impacted by development, population estimates
were conaucted by the mark -and -recapture method at two stations Walleye
(excluding young-of-the-year) populations were estimated at one site on
the East Fork (lower) and one site on the mainstem immediately below the
confluence of the East and Middle Forks. Estimates were made utilizing
Chapman's modification of the Petersen formula (Ricker, 1975 Pg. 78):

N = (M+1) (C+i) where

R+1

N = Population estimate.

M = Number of fish marked.

C = Number of fish in recapture sample.

R = Number of marked fish in recapture sample (C) .

>

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Table 2. Numbers and species of fish observed (but not collected) while sampling with an alternating
current boom-shocker at nine stations on the Poplar River, 1975.

Species

East
Fork
Upper

East
Fork
Lower

1/

Middle
Fork

Conflu.
East &
Middle
Forks

Main
River
Chabot 's

Main
River
Paulson
Slab

West
Fork

Main
River
Crowley
Slab

Main
River
Lower

Carp

15

3

2

9

29

33

35

16

31

River

carpsucker

20

20

101

Bigmouth
buffalo

1

Shorthead
redhorse

20

1

5

24

29

191

74

59

89

Longnose
sucker

1

White
sucker

2,984

168

40

455

242

378

349

83

12

Black
bullhead

1

1

Channel
catfish

—

—

—

—

—

—

—

—

1

Stone cat

6

3

Yellow
perch

2

Freshwater

1

drum

\j Represents fish collected.

This work revealed a population of 178 walleye per mile in the East Fork and
297 walleye per mile at the confluence of the East and Middle Forks. Popula-
tion estimates were not made for goldeye, northern pike, and smallmouth bass
because low populations or failure to recapture sufficient numbers of marked
fish did not satisfy statistical criteria.

Reproduction: Reproductive success of sport fishes and abundance of
forage species was determined at nine stations by sampling in the fall with a
4- X 25-foot seine of %-inch square mesh. A summary of abundance and distri-
bution of small and/or young fish is presented in Table 3. Each sample des-
ignated on this table represents one seine haul through 25-50 feet of stream.

The best catch for young-of-the-year walleye occurred at the upper Middle
Fork station. It was also apparent that the East Fork provides important wall-
eye spawning habitat. Young-of-the-year northern pike were only taken in the
mainstem river below the confluence of the East and Middle Forks. However,
reports from anglers indicate that northern pike are more common in the Middle
Fork than was indicated at the sampling station.

Lake chub and white sucker were key forage species throughout the drain-
age. Fathead minnows and longnose dace were common at most collection sites.
The large numbers of northern redbelly dace and brook stickleback taken at
the upper East Fork station appear to be associated with channel eutrophica-
tion conditions. In general the abundance and distribution of the flathead
chub was similar to that of the emerald shiner which appeared to be confined
to the mainstem river and lower West Fork.

Movement : Walleye and northern pike are not native to the Poplar River
system and events responsible for development of their populations are not
known. Personal communication with "oldtimers" who have resided along the
river for up to 70 years indicate these species were not present histori-
cally. Limited walleye stocking conducted by the Montana Department of
Fish and Game from the mid 1950 's to the early 1960 's may have been a con-
tributing factor; however, population increases of walleye and northern
pike during this period in the Missouri River undoubtedly had a major role
in establishing populations in the Poplar River,

In an effort to determine the extent of movement and migration for
selected sport fishes, within the Poplar River system, marking was conducted
m the spring and fall of 1975 by tagging and fin excision. The objectives
of this work were to: 1) determine residence within the system, 2) identify
spawning migrations, and 3) determine the contribution, if any, from migra-
tion of Missouri River fishes.

A total of 1,071 fish were marked for study, of which 733 were walleye
as summarized in Table 4. All tags utilized were numbered Floy anchor tags.
Walleye tagging was confined to adults and some yearlings in the 7- to 10-
inch size class. Goldeye were marked by fin-clipping to minimize stress by
handling.

Since most fish marking was in the fall of 1975 and comparatively few
were marked the previous spring, only limited numbers of marked fish were
available for study during the period covered by this report. Fall sampling

Tatle 3. A sunmary of fish collected by sampling with a 4- x 25-foot seine in the Poplar River, 1975.

Species

East Fork East Fork Middle Fork Middle Fork Main River Main River Main River Main River

Size Upper Lower Upper Lower Chabot'e Paulson Slab West Fork Crowley Slab Lower

(Inches) (4 Samples) (6 Samples) (10 Samples) (5 Samples) (3 Samples) (5 Sagfiles) (A Samples) (3 Samples) (3 Samples)

Northern pike
Carp

Creek chub

Northern redbelly
dace

Flathead chub

Lake chub

Emerald shiner

Brassy minnow

Silvery /plains
minnow

Fathead minnow
Longnose dace
River carpsucker
Blgmouth buffalo
Shorthead redhorse

White sucker

Brook stickleback
Smallnouth bass
Walleye

Iowa darter

8-11
1-2

1-3

1-3

3-6
6-9

1-6
6-10

3- 8

4- 6
8-14

4

2

1,311

297

*

96

96
9

163
2

2U

319
7

18
72

11

342

406

110
16

84

348
308

40

4

195

13

34

10

12

11
110
8

14

1

4

30
14

42
99
357

16

16

17
18

1
18

96
310

114

19
60

60
18

189
206
239

12
1

1
X2
2

42
5

213
14
209

20

3
8

8
5

26
5

13

Identification error may have included brassy minnows with silvery/plains minnows.

Table 4. A Summary of fish marked by tagging and fin-clipping at various
locations in the Poplar River, 1975.

Walleye Northern Pike Sanger Goldeye
Station Tag Clip Tag Clip Tag Clip Tag Clip

East Fork 109 113 4 __ - - 12

Middle Fork 28 75

Confluence 135 54 1 — 1 - - 73

East and
Middle Forks

Main River 41 35 - 10 - - - 88

Chabot ' s

West Fork 45 11 - - - - 32

Main River 39 11 - 17 * - - - 35

Paulson Slab

Main River 16 6 3 10 1 - - 14

Crowley Slab

Main River 9 6 - 10 1 - - 20

Lower

Totals 422 311 9 47 3 - - 279

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in 1975 provided movement observations on five walleye and one northern pike
marked in the spring. Three of the walleye were recaptured at the same loca-
tion where marking occurred, and two had moved upstream 4 to 6 miles. The
northern pike had moved downstream approximately 2 miles.

Fishermen reported eight walleye tag returns. Five of these tagged in
the fall of 1975 were caught within one month near the release site. Three
reports of tagged fish were made in the spring of 1976. One of these was
caught at the lower East Fork station and had been tagged at that location
in the spring of 1975. The second was caught 6 miles north of Poplar and
had been tagged at the Crowley Slab in the fall of 1975. This represents a
downstream movement of approximately 25 river miles. The third was caught
just west of Scobey and had been tagged in the fall of 1975 at the conflu-
ence of the East and Middle Forks which represents a downstream movement of
several miles.

Electrof ishing during the spring of 1976 at the lower East Fork station
captured one marked goldeye which had been released at this site in the fall
of 1975.

Age and Growth: Scale samples were collected from various species for
aging to facilitate data arrangement by year-class and provide an additional
dimension to fish population knowledge. Back-calculations were made using an
intercept at zero. A summary of age and growth findings is presented in
Table 5.

Growth rates for walleye, northern pike, and smallmouth bass were good
overall. As adult smallmouth bass become more abundant, future age deter-
minations will be desirable. Some difficulty was encountered when identi-
fying annuli on goldeye scales and this effort should be repeated with addi-
tional samples. Growth for goldeye was similar to, but slightly poorer than
that reported for the Missouri Rifver by Bill Hill (1965) .

CONCLUSIONS AND RECOMMENDATIONS

The low, stable flows proposed for the East Fork will dramatically alter
the natural flow regimen of this river. It is anticipated that this condition
will greatly impair walleye reproduction and contribute to channel eutrophica-
tion.

The Middle Fork contains one of the most important segments of the sport
fishery. Potential flows within the proposed allotments should be adequate to
maintain walleye. However, the water apportionment does not indicate the ex-
tent or timing of releases, and therefore, meaningful evaluations of impacts
cannot be ascertained. Flow regimens that generally resemble existing con-
ditions, particularly with reference to spring flow are essential.

An immediate need exists to obtain improved quantitative information on
the fish population in the East Fork where near future impacts are anticipated.
Additional population estimates should be secured for adult sport fishes and

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Table 5. A summary of growth rate information for several species in the
Poplar River, 1975. The number of fish sampled is given in
parenthesis .

Species &

Age Class

Station

I

II

III

IV

V

VI

VII

VIII

Walleye:

East Fork

4.2
(3)

8.8
(2)

11.4
(1)

13.9

(1)

17.5

(1)

19.7

(1)

Middle Fork

5.0

(11)

8.9
(7)

11.1

(7)

13,5
(7)

15.7

(6)

16.9

(2)

West Fork

4.9

(13)

9.0

(13)

11.5

(7)

14.0
(5)

16.0
(5)

17.8

(2)

Confluence
East & Middle
Forks

4.7

(29)

8.8

(25)

11.6

(13)

13.5

(12)

15.8
(7)

16.5

(4)

18.3

(3)

Combined
Average

4.7

(56)

8.9
(47)

11.5
(28)

13.6

(25)

15.9

(19)

17.3

(9)

18.3

(3)

Smallmouth
bass

3.6

(17)

8.2

(1)

Northern
pike

11.1
(3)

Go Id eye

3.2

(22)

6.5

(22)

8.7
(22)

10.2

(22)

11.5
(21)

12.2
(10)

13.4
(4)

14.4
(2)

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efforts should concurrently be undertaken to identify spawning and nursery
areas for walleye and quantify reproduction. Early spring sampling should
be conducted to evaluate and identify key spawning sites.

LITERATURE CITED

Hill, Willaim J. 1965. Observations on the Life History and Movement of
the Goldeye Hiodon alosoides in Montana. Proc. Mont. Acad. Sci. 26
p. 45-53.

Ricker, W. E. 1975. Computation and Interpretation of Biological
Statistics of Fish Populations. Fish Res. Bd. Can., Bull. 191
382 p.

Prepared by Robert G. Needham

Date June 11, 1976

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