Field evaluation of four strains of rainbow trout (Salmo gairdneri)
by Mary Ellen Mueller
A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Fish
and Wildlife Management
Montana State University
© Copyright by Mary Ellen Mueller (1985)
Abstract:
The performance of four strains of rainbow trout, (Salmo gairdneri) was evaluated under field
conditions. Data on field performance of specific strains is needed in order to best utilize a particular
fish in a natural environment. Growth, catchability and longevity data were collected in the field by a
summer-long creel survey. Fish from each strain were stocked at equal densities in two ponds near
Three Forks, Montana, for a replicated field evaluation. The Winthrop domestic strain grew faster and
was harvested at a higher rate than were the Erwin, DeSmet or Arlee strains. The Winthrop strain had
the highest catchabdlity followed by Aflee, Erwin and DeSmet. The DeSmet strain and the Winthrop
strain appeared to remain in the fishery longer, being found in the highest proportions in a population
estimate taken 5 months after termination of the creel survey. FIELD EVALUATION OF FOUR
STRAINS OF R A I N B O W TROUT
(S a l m o g a i r d n e r i )
by
Mary
A
Ellen
Mueller
t h e s i s s u b m i t t e d in p a r t i a l f u l f i l l m e n t
of the r e q u i r e m e n t s for the d e g r e e
of
Master
of
Science
in
Fish
and
Wildlife
Management
MONTANA STATE UNIVERSITY
Bozeman, Montana
August
1985
MAIN
LIB.
fJsys'
ii
APPROVAL
of
a
thesis
MARY
submitted
ELLEN
by
MUELLER
This thesis has been read by each m e m b e r of the thesis
c o m m i t t e e and has been found to be sati s f a c t o r y regarding
content, English usage, format, citations, bibliographic
s t y l e , a n d c o n s i s t e n c y , a n d is r e a d y f o r s u b m i s s i o n t o t h e
C o l l e g e of G r a d u a t e S t u d i ^ =
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for
Date
Hc au , via jul
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College
of
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Graduate
Graduate
Dean
Studies
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requirements
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ACKNOWLEDGEMENTS
T h e a u t h o r w i s h e s to e x t e n d he r s i n c e r e a p p r e c i a t i o n to
the following, who among others, assisted her throughout the
c o u r s e of this study.
Dr. R o b e r t W h i t e d i r e c t e d t h e s t u d y
a n d a s s i s t e d in p r e p a r a t i o n of t h e m a n u s c r i p t .
D r s . Ray
White and Robert Eng who critically reviewed the manuscript.
P a t D w y e r -f o r f i e l d a s s i s t a n c e a n d h e l p i n r e v i e w i n g t h e
manuscript.
All personnel at the Bozeman Fish Technology
Center for field a s s i s t a n c e and c o n s t r u c t i v e suggestions,
e s p e c i a l l y R o b e r t G. P i p e r .
Friends and other students
offered suggestions and aided with field work, most
especially Stacey J . Pederson without whose assistance and
friendship this study would not have been possible.
The
midnight marauders assisted with gill netting.
M y special thanks to m y family, a n d e s p e c i a l l y to m y
mother and step-father whose support both financial and
moral saw me through.
V
TABLE
OF
CONTENTS
Page
LIST
OF
T A B L E S ............................................................ v i
LIST
OF
F I G U R E S ......................................................... v i i i
A B S T R A C T .................... ..
INTRODUCTION
DESCRIPTION
. ......................................... x
...............................
OF
STUDY
I
S I T E ............................................... 5
M E T H O D S .........................................................................5
in oo oo
S t o c k i n g ..........................................
Strain Marking.
. . .........................
C r e e l C e n s u s S a m p l i n g .............. ..
T e m p e r a t u r e a n d W a t e r C h e m i s t r y A n a l y s i s ................. 1 0
P o p u l a t i o n E s t i m a t i o n ........................................... 1 0
S t a t i s t i c a l A n a l y s e s ................. ................ ..
„ . .12
R E S U L T S .........................
13
C r e e l S u r v e y ......................................................... 1 3
C o n d i t i o n F a c t o r ................................................... 1 4
G r o w t h .......................................... -..................... 2 9
T e m p e r a t u r e a n d W a t e r Q u a l i t y ................................2 9
P o p u l a t i o n E s t i m a t e ...............................
35
D I S C U S S I O N ................................................... .■ .
.
.
.37
C r e e l S u r v e y ......................................................... 3 7
T e m p e r a t u r e a n d W a t e r C h e m i s t r y ............................. 3 9
P o p u l a t i o n E s t i m a t e .............................................. 4 0
C o n c l u s i o n s a n d M a n a g e m e n t R e c o m m e n d a t i o n s ...............4 4
R E F E R E N C E S ................................................................ . 4 5
A P P E N D I X ...............................
49
LIST
OF
TABLES
Table
1.
2.
3.
4.
5.
6.
7.
8.
9.
Page
R e c o r d e d c a t c h of each s t r a i n of r a i n b o w t r o u t and
extrapolated totals from creel census conducted at
P o n d I, T h r e e F o r k s , M o n t a n a . J u n e 8 t o S e p t e m b e r
12,
1 9 8 2 ..........................................................
16
R e c o r d e d c a t c h of each s t r a i n of r a i n b o w t r o u t an d
e x t r a p o l a t e d totals from c reel census c o n d u c t e d at
P o n d 2, T h r e e F o r k s , M o n t a n a .
June 8 to September
12,
1 9 8 2 ..........................................................
17
L e n g t h f r e q u e n c y d i s t r i b u t i o n s of r a i n b o w t r o u t
strains from creel survey.
D a t a f o r P o n d I. C o n ­
d u c t e d at T h r e e Forks P o n d s , Montana, 1982.
(W=Winthrop, E=Erwin, D=DeSmet, A=Arlee; numbers
r e p r e s e n t n u m b e r s of f i s h c a u g h t of t h a t s t r ain)
.
. 22
L e n g t h f r e q u e n c y d i s t r i b u t i o n s of r a i n b o w t r o u t
strains from creel survey.
D a t a f o r P o n d 2. C o n ­
d u c t e d at T h r e e Forks Ponds, Montana, 1982.
(W=Winthrop, E=Erwin, D=DeSmet, A=Arlee; numbers
r e p r e s e n t n u m b e r s of f i s h c a u g h t of t h a t s t r a i n )
.
. 24
A n a l y s i s of l e n g t h f r e q u e n c y d i s t r i b u t i o n s of r a i n ­
b o w t r o u t p r i o r to s t o c k i n g a n d f r o m s u m m e r c r eel
survey data for Three Forks P o n d s , Montana . . . . .
26
O b s e r v e d c a t c h p e r h o u r o f e f f o r t in e a c h s t r a t a
f o r P o n d I, T h r e e F o r k s , M o n t a n a .
June 8 to
S e p t e m b e r 1 2 , 1 9 8 2 . . ........................................
27
O b s e r v e d c a t c h p e r h o u r o f e f f o r t in e a c h s t r a t a
f o r P o n d 2, T h r e e F o r k s , M o n t a n a .
June 8 to
S e p t e m b e r 1 2 , 1 9 8 2 .............................................
27
M e a n c o n d i t i o n factors for D e S m e t , W i n t h r o p , Erwin,
a n d A r l e e s t r a i n s of r a i n b o w t r o u t at t h e b e g i n n i n g
of the s t u d y a n d d u r i n g c r e e l survey, T h r e e F orks
P o n d s , M o n t a n a , 1 9 8 2 ....................
. . . . . . . .
28
Water chemistry and
a n d 2. T h r e e F o r k s ,
34
t e m p e r a t u r e data for Ponds I
M o n t a n a , 1 9 8 2 .........................
vii
LIST
OF
TABLES
(continued)
Table
10.
11.
Page
P e r c e n t by stra i n of c a tch f r o m s u mmer creel s u rvey
a n d J a n u a r y g i l l n e t t i n g i n P o n d I, T h r e e F o r k s ,
M o n t a n a , 1 9 8 2 - 1 9 8 3 .............................................
36
P e r c e n t by s t r a i n of c a t c h f r o m s u m m e r creel s u r v e y
a n d J a n u a r y g i l l n e t t i n g i n P o n d 2, T h r e e F o r k s ,
Montana, 1982-1983
36
viii
LIST
OF
FIGURES
Figure
Page
1.
Location
of
s t u d y s i t e ............................................. 6
2.
Location
of
Three Forks
3.
Location
and
4.
L o c a t i o n s of
Three Forks,
5.
symbols
ponds
used
to
................................
distinguish
7
strains.
.
. 9
s a m p l i n g s t a t i o n s i n P o n d s I a n d 2,
M o n t a n a .......................................
.
.11
P e r c e n t a g e of t o t a l c a t c h of r a i n b o w t r o u t c r e e l e d
b y s t r a i n i n P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a ,
1982.
(D = D e S m e t , E = E r w i n , W = W i n t h r o p , A = A r l e e ) .
. .
.15
6.
L e n g t h f r e q u e n c y h i s t o g r a m s of creel s u r v e y d a t a
f r o m P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a c o m p a r e d
to p r e - s t o c k i n g data for W i n t h r o p r a i n b o w trout.
( N u m b e r s in b l o c k s r e p r e s e n t s t r a t u m in w h i c h f i s h
w e r e c a u g h t ) ........................................................ 1 8
7.
L e n g t h f r e q u e n c y h i s t o g r a m s of c r e e l s u r v e y d a t a
f r o m P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a c o m p a r e d
to p r e - s t o c k i n g data for E r w i n r a i n b o w trout.
( N u m b e r s in b l o c k s r e p r e s e n t s t r a t u m in w h i c h f i s h
were caught).
. ............. ...................... ............. 1 9
8.
L e n g t h f r e q u e n c y h i s t o g r a m s of c r e e l s u r v e y d a t a
f r o m P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a c o m p a r e d
to p r e - s t o c k i n g d a t a for A r l e e r a i n b o w t r o u t .
( N u m b e r s in b l o c k s r e p r e s e n t s t r a t u m in w h i c h f i s h
w e r e c a u g h t ) ........................................................ 2 0
9.
L e n g t h f r e q u e n c y h i s t o g r a m s of creel s u r v e y d a t a
f r o m P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a c o m p a r e d
to p r e - s t o c k i n g d a t a for D e S m e t r a i n b o w trout.
( N u m b e r s in b l o c k s r e p r e s e n t s t r a t u m in w h i c h f i s h
w e r e c a u g h t ) ................. .. ..............................
.21
ix
LIST
Figure
OF
FIGURES
(continued)
Page
10.
R e l a t i o n s h i p between time an d m ean w e i g h t of DeSmet
r a i n b o w t r o u t i n P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a ,
1982.
Strata 1-8 r e p r e s e n t two w e e k intervals s t a r t ­
i n g J u n e 6,
1982.
T h e d a t a p o i n t s at s t r a t u m 14 a r e
the average
w e i g h t s of f i s h c o l l e c t e d by g i l l n ets
on January
5 - 1 4 , 1 9 8 3 ............................................3 0
11.
R e l a t i o n s h i p betw e e n time and m e a n w e i g h t of Erwin
r a i n b o w t r o u t i n P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a ,
1982.
Strata 1-8 represent two week intervals start­
i n g J u n e 6,
1982.
T h e d a t a p o i n t s a t s t r a t u m 1 4 is
the average
w e i g h t s of f i s h c o l l e c t e d b y g i l l n e t s
o n J a n u a r y 5 - 1 4 , 1 9 8 3 .................................. ..
. .31
12.
R e l a t i o n s h i p b e t w e e n t i m e a n d m e a n w e i g h t of
W i n t h r o p r a i n b o w t r o u t i n P o n d s I a n d 2, T h r e e
Forks, Montana, 1982.
Str a t a 1-8 r e p r e s e n t two week
i n t e r v a l s s t a r t i n g J u n e 6, 1 9 8 2 .
The data p o i n t s at
s t r a t u m 14 a r e t h e a v e r a g e w e i g h t s of f i s h c o l l e c t e d
b y g i l l n e t s o n J a n u a r y 5 - 1 4 , 1 9 8 3 ......................... . 3 2
13.
R e l a t i o n s h i p between time and m e a n w e i g h t of Arlee
r a i n b o w t r o u t i n P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a ,
1982.
Strata 1-8 r e p r e s e n t two wee k intervals s tart­
i n g J u n e 6,
1982.
T h e d a t a p o i n t s at s t r a t u m 14 a r e
the average
w e i g h t s of f i s h c o l l e c t e d by g i l l ne t s
on January
5-14, 1983
33
ABSTRACT
T h e performance of four strains of rainbow trout, (Salmo gairdneri) w a s
evaluated under field conditions. Data o n field performance of specific strains is
n e e d e d in order to best utilize a particular fish in a natural environment.
Growth, catchabdlity a n d longevity d a t a w e r e collected in the fie ld b y a
summer-long creel survey. Fish from e a c h strain w e r e stocked a t equal densit-igy;
in t w o ponds near T h r e e Forks, Montana, for a replicated fie ld evaluation. T h e
Winthrop domestic strain g r e w faster a n d w a s harvested a t a higher rate than
w e r e the Erwin, D e S m e t or Arlee strains. T h e Winthrop strain h a d the highest
catchabdlity followed by Aflee, Er w i n a n d DeSmet, T h e D e S m e t strain a n d t he
Winthrop strain appeared t o remain in the fishery longer, being found in the
highest proportions in a population estimate taken 5 m o n t h s after termination of
the creel survey.
I
INTRODUCTION
Traditionally, hatchery-reared rainbow trout h a v e b e e n selected for such
desirable hatchery characteristics as rapid growth, e g g production, survival, a n d
spawning time.
efficient
Hatchery managers w e r e concerned with raising the m o s t cost
product
relative
to
hatchery
consideration given to qualities w hich
conditions,
with
relatively
little
would increase survival after stocking.
T h e n e e d to improve survivability to the creel through selection in the hatchery
did not gain recognition until the late 1960s (Kramer, 1969).
"Fish suitability"
began to b e considered as a m a n a g e m e n t objective, with the idea of interpreting
"suitability" as "related t o the problem of matching the fish to the environment
in order to deliver a high percentage survival c£ stocked fish to the creel"
(Kramer, 1969).
Most
fishery
management
agencies
utilize
stocking
as
part
of
their
m a n a g e m e n t programs, therefore, evaluations c£ fish perfo r m a n c e in the w ild
b e c o m e critical in matching the fish to the environment.
increasing
emphasis
is being
placed
on
evaluating
T o achieve this end,
p e r formance
of
specific
hatchery strains in natural environments (Hudy, 1980; Kincaid, 1981; F a y a n d
Pardue, 1982; D w y e r a n d Piper, 1984).
M a n y researchers h a v e investigated performance
of fish in hatcheries.
Growth, a n economically important quality of hatchery selection, w a s studied by
M a s o n et a L (1967) w h o found that u n d e r hatchery conditions, domestic strains
of brook trout h a d significantly faster weight gains than wild strains.
(1952)
reported
growth
rate
differences
strains cf lake trout (Seneca, Saranac,
m onths cf age.
among
fingerlings
from
Haskell
three
wild
Ragvette) reared in hatcheries to 6
G r e e n (1951) foun d that a domestic brook trout strain yielded a
heavier a n d deeper bodied fish than a wild strain.
Reinitz (1978) evaluated four
2
rainbow trout strains a n d f o u n d significant differences in strain growth.
studies
in
which
wild
conditions or in the
and
domestic
trout
wild s h o w e d that the
faster, m a t u r e at an earlier age, pro d u c e
higher resistance to disease
than the
were
compared
under
Other
hatchery
domestic strains tended to g r o w
m o r e eggs per female, a n d exhibit
wild strains
(Kincaid,
1978;
Gall a n d
Gross, 1978; ReisenbLchler a n d McIntyre, 1977).
Catchability
of
a
particular
strain
is
an
important
management
consideration. Increases in the return to the creel c a n be accomplished by strain
selection (C o r d o n e a n d Nicola, 1970).
R a w s t r o n (1973, 1977) demonstrated the
importance of strain differences in a catchable program.
differences b e t w e e n the
Coleman,
Kamloops,
H e found no g r o w t h
Whitney, a n d
Shasta strains of
rainbow trout, but the K a m l o o p s strain return to the creel w a s consistently
superior in size.
H e concluded that the Kamloops' limnetic distribution allowed
it to avoid early vulnerability a n d r each a larger size.
Wales a n d Borgeson
(1961) f o u n d the K a m l o o p s strain m o r e susceptible to fly fishing than the Shasta
strain.
DdLan .and Piper (1979) reported higher catehability of t w o domestic
strains of rainbow trout (Winthrop a n d Standard Growth) w h e n c o m p a r e d t o t w o
wild strains (Fish L a k e a n d M c C on a u g h y ) .
Moring (1982) assessed three varieties
of hatchery rainbow trout a n d f o u n d t he C a p e C o d strain yielded better results
(higher catches a n d less out migration) than the Roaring River or O a k Spring
strains.
Survival to
considered.
the
creel
is
perhaps 'the
most
important
aspect
to
be
T h e n u m b e r of catchable size trout stocked annually in the United
States exceeds
70
million (Mating,
1982).
Increased costs c£ raising fish in
hatcheries, c o m b i n e d with fiscal cutbacks in m o s t agencies ha v e reduced the
benefit to cost ratios of m a n y stocking programs.
T o minimize this reduction.
3
survival to the creel b e c o m e s critical.
Flick a n d Webster (1976) concluded that
wild strains c£ brook trout raised in a hatchery w e r e better a HIp to survive in
the first f e w
months following release than w e r e the domestic strains.
(1951) f o u n d that in
stocking fingeding
wild a n d domestic
Green
brook trout, the
domestic strain provided a higher return to the creel during the first fishing
season, but a smaller return during the second.
T h e larger sized (faster g r o w t h
rate) fish of the domestic strain w e r e m o r e susceptible to angling.
M a s o n et a L
(1967) f o u n d that domestic strains of brook trout w e r e harvested early in the
fishing season, w h ereas domestic x wild hybrids a n d wild strains contributed to
the fishery throughout the season.
T h e specific objectives of this study w e r e to evaluate Winthrop, AfLee,
D e S met,
and
Erwin
strains
of
rainbow
trout
survival in a simulated natural environment.
commonly
used
strains
in
Montana
(R.G.
for
growth,
catchahdlity,
and
T h e s e strains represented the m o s t
Piper,
Fish
Technology
Center,
B o z e m a n , MT., personal communication).
The
Winthrop strain, a January s p a w n e r w h e n held at a constant water
temperature of 10°C, is a domestic strain originating f r o m private stock f r o m
C a p e Cod, Massachusetts, in 1936. This strain has b e e n evaluated in the wild by
the U.S. Fish & W ildlife Service in B o z e m a n , Montana. It is currently maintained
there as a brood stock for use in research a n d d e v elopment studies as well as
for minor plantings.
It is considered highly successful in put-and-take fisheries
a n d grows well in the hatchery (W.P. Dwyer, Fish Technology Center, Boz e m a n ,
MT., personal communication).
T h e Arise, a domestic A u g u s t - D e c e m b e r spawner, originated f r o m a cross
b e t w e e n a Donaldson a n d a n unidentified Missouri strain in 1955.
It w a s widely
used in M o n t a n a b y the M o n t a n a D e p a r t m e n t of Fish, w ildlife, a n d Parks, but is
4
currently being phased out. M a n a g e m e n t biologists feel it has very l o w s p awning
potential a n d very l o w survival in the wild (R. Vincent, M D F W P , B o z e m a n , MT.,
personal communication).
The
DeSmet
strain,
a
January-Fehruary
spawner
considered a mixed domestic and. natural stock.
in
the
hatchery,
is
This designation is given b y
Kincaid (1981), w h o defined a domestic stock as "a brood stock maintained b y
m a n in a hatchery environment continually for m o r e than t w o generations" a n d a
natural stock as "a brood
stock maintained in a
natural environment (lake,
reservoir, pond, or stream) b y a combination of natural sp a w n i n g a n d periodic
stocking with fish reared in a hatchery environment".
T h e m i x e d domestic a n d
natural classification for the D e S m e t is used because the
wild fish of L a k e
DeSmet, Wyoming, m o v e into Shell C r e e k to s p a w n during April a n d t he eggs are
then collected a n d hatchery reared.
W y o m i n g De p a r t m e n t c£ G a m e
catchabLe
strain,
the
Eagle
T h e D e S m e t strain is widely used b y the
& Fish,, but is currently being replaced by a m o r e
Lake
(R.
G a r butt,
Wyoming
Game
and
Fish
Department, Casper, Wyoming, personal communication).
The
Erwin
originating from
strain, a n
the
O c t o b e r - D e c e m b e r spawner, is a domestic strain
Wytheville
strain
of Virginia.
Tennessee, in 1973 a n d cultured as the E r w i n strain.
It
was
sent to
Erwin,
It has b e e n widely used in
M o n t a n a a n d is currently maintained a t the Ennis National Fish Hatchery.
previous
evaluations
cf
performance
in the
wild h a v e
been
conducted,
No
but
m a n a g e m e n t biologists consider it a satisfactory strain, w h i c h g r o w s well in the
hatchery but is s o m e w h a t lacking in vigor (D. Jennings, U S F WS, Regional Office,
Denver, C O., personal communication).
5
D E S C R I P T I O N O F S T U D Y SITE
This study w a s conducted in t w o ponds located 0.5 miles east of T h r e e
Forks,
Montana
(Township 2N,
R a n g e IE, Section 25; Figures I a n d 2).
ponds are former gravel pits purchased b y the
W ildlife, a n d Parks.
Montana
The
D e p a r t m e n t of Fish,
P o n d I has 21.4 surface acres (8.66 ha), a m a x i m u m depth
of 5.46 m, a m e a n depth of 3.64 m, a n d a regular b o ttom c o m p o s e d of gravel
a n d mud, with shoreline vegetation consisting of cattails (Typhaceae).
Pond 2
has 12.4 surface acres (5.02 ha), a m a x i m u m depth of 5.46 m, a m e a n depth of
3.94
m,
a
somewhat
irregular
bottom
of
gravel
and
mud,
and
shoreline
macrop h y t e vegetation, primarily cattails (Dolan a n d Piper, 1979).
The
ponds are fed b y ground
water
and
w a t e r levels remained fairly
constant throughout the s u m mer.
METHODS
Stocking
In
September
r e m o v e fish.
rainbow trout.
c£
1981
the
two
p onds
O n J u n e 6, 1982, e a c h p o n d
were
treated
m e a s u r e d for a r a n d o m sample of 200 fish of e a c h strain.
also calculated for
to
w a s stocked with four strains of
Prior to stocking, length, weight, a n d
calculating condition factor was:
with rotenone
condition factor
were
T h e formula used for
3
5
(weight/length ) x 10 . Condition factors w e r e
all fish censused as
well as for fish gill netted during
population estimation.
T w e l v e hundred a n d seventy a n d 780 trout of ea c h strain w e r e stocked in
ponds I a n d 2, respectively.
This represented 237 fish per surface acre in p o n d
I a n d 251 fish per surface acre in p o n d 2. T h e s e stocking n u m b e r s w e r e used to
remain
consistent with previous strain evaluations conducted in these ponds
(Dolan a n d Piper, 1979; D w y e r a n d Piper, 1984).
Butte
Kilometers
Figure
I.
Location
of
study
site
7
Figure
2.
Location
of
Three
Forks
Ponds.
8
Strain Marking
Each
fish
MigheQl (1969).
fish
was
was
marked
using a
cold
branding
technique
described
by
Liquid air w a s used to super-cool a brass branding iron. E a c h
anesthetized
approximately 2 seconds.
other strains (Figure 3).
using
MS222
and
then
held
against
the
iron
for
E a c h strain h a d a distinct brand distinguishing it from
Fish w e r e branded 3 w e e k s prior to stocking.
Creel Census Sampling
A
creel census w a s conducted f r o m J u n e 8 to S e p t e m b e r 12, 1982.
census period w a s broken d o w n into strata of 14 days.
randomly selected using a r a n d o m n u m b e r table.
days w e r e sampled in each stratum.
AU
The
Sampling days w e r e
Seven weekdays and 3 w e e k e n d
holidays w e r e sampled. T w o out of 3
w e e k e n d days w e r e sampled f r o m 3 p m to 10 p m with the remaining d a y sampled
from 8 a m to 3 pm. F o u r c£ the w e e k d a y s w e r e sampled f r o m 3 p m to 10 p m a n d
3 w e e k d a y s w e r e sampled f r o m 8 a m to 3 p m.
Creel census data w e r e extrapolated t o represent all hours fished.
The 3
w e e k e n d samples in each stratum w e r e a veraged to give a m e a n value, which
w a s multiplied by 4 to give an extrapolated total value for the 4 w e e k e n d days
in the 2 - w e e k stratum. Similarly, th e 7 w e e k d a y s in each stratum w e r e averaged
to provide a m e a n value, which w a s multiplied by 10 to give the extrapolated
total value for w e e k d a y s in the stratum.
Fishermen
Information
were
recorded
interviewed
during
the
every
interview
hour
on
included
both
bodies
number
of
water.
of fish caught,
strain, weight, length of e a c h fish, h o w long fished, a n d location of fisherman.
E a c h fish censused w a s w e ighed to the nearest I g r a m using a platform scale.
Length w a s m e a s u r e d to the nearest I m m using a metric measuring board.
9
DESMET
ARLEE
WINTHROP
Figure
3.
Location
and
symbols
used
to
distinguish
strains.
10
Lengtli frequency data of all strains stocked w a s m e a s u r e d prior to stocking a n d
c o m p a r e d to length
survey
data.
frequency distributions
F r e q uency
analysis,
Kruskal-W allis nonparametric
differences
between
one-way
one-way
prestocking,
obtained f r o m
analysis
pond
I
and
analysis
the s u m m e r
of
creel
variance
and
were
calculated to determine
pond
2
means
and
variances.
Distributions w e r e also analyzed for kurtosis a n d skewness.
Temper a t u r e a n d W a t e r Chemistry Analysis
W a t e r chemistry w a s sampled monthly.
W a t e r samples w e r e taken from
three depths at t w o stations per pond, a n d a n average value recorded.
were
selected to represent m a x i m u m
(Figure 4).
Stations
depths in both ponds at each location
W a t e r samples w e r e taken at 0.9, 3.0, a n d 4.5 m, respectively, with
a K e m m e r e r bottle.
Samples w e r e then transferred to an E rienmeyer flask for
determinations cf alkalinity, hardness, a n d p H using a H a c h chemical Mt.
temperature
and
dissolved
oxygen-temperature meter.
oxygen
were
measured
using
a
A
model
54
T h e probe cf the meter w a s attached to a 4.5 m
cord that w a s l o w e r e d to three different depths (0.91 m, 1.82 m
obtain readings.
YSI
Water
a n d 2.73 m) to
secchi disc w a s u s e d to record turbidity (depth of light
penetration).
Population Estimation
T o evaluate strain survival, a population estimate w a s m a d e on January
5-7 a n d 12-14, 1983 based o n a mark-recapture m e t h o d in which the m a r k e d
c o m p o n e n t cf the population consisted of m o r e recently stocked trout that h a d
b e e n fin clipped. T h r e e hundred fifty a n d 250 m a r k e d fish w e r e planted in ponds
I a n d 2 respectively 10 w e e k s prior to gill netting.
Chapman
modification
(Ricker,
1975)
of
the
Calculation w a s b y the
Petersen
formula
(N
=
(M+l)(C+l)/(R+i)) w h e r e N is the estimated size of the population a t the time of
11
Station I
Station 2
Station I
Station 2
Pond I
F i g u r e 4. L o c a t i o n s o f s a m p l i n g
2, T h r e e F o r k s , M o n t a n a .
Pond 2
stations
in
Ponds
I
and
12
marking, C is the catch or sample taken, M is the n u m b e r of fish marked, a n d R
is the n u m b e r of recaptured marks in the sample. F o r purposes of the population
estimate, rainbow trout of D e S m e t strain w e r e obtained f r o m t he surplus stock
of the Fish Technology Center.
p u n c h e d for marking.
On
T hese fish w e r e anesthetized a n d caudal fins
October 20, 1982, 350
stocked in ponds I a n d 2, respectively.
a n d 250
m a r k e d fish w e r e
Experimental g i U nets (mesh size 1.9,
3.2, 3.8, 5.1, a n d 6.4 cm) w e r e set J a n u a r y 5, 6, 7, 1983, in p o n d 2, a n d o n
J a n u a r y 12, 13, 14, 1983, in p o n d I.
Experimental g i U nets w e r e set u n d e r the
ice using a p o w e r auger to o p e n holes a n d a lever action ice jig to string the
nets.
Five nets w e r e set in each p o n d overnight for three consecutive nights.
Fish captured w e r e weighed, measured, a n d strain or caudal p u n c h recorded.
Statistical Analyses
Statistical m e thods presented in S n edecor a n d C o c h r a n (1980) w e r e used
in all data analyses.
frequencies
T h e S P S S statistical c o m p u t e r p a c k a g e w a s also used for
analysis, analysis
confidence limits w e r e at 95%.
of variance
tests
a n d linear regressions.
All
13
RESULTS
Creel Survey
During the creel census, 330 fish w e r e e x a m i n e d in p o n d I.
total harvest w a s 945 or 18.6% of the 5080 fish planted.
48.8%
w e r e Winthrop, followed b y 24.2%
(Figure 5, Table I).
T h e estimated
O f the fish exa m i n e d
Aflee, 19.4% Erwin, a n d 5.2% D e S m e t
Eight fish creeled w e r e unidentifiable to strain. In p o n d 2,
357 fish w e r e e x a m i n e d during the creel census.
w a s 846 or 27.1% of the 3120 fish planted.
Winthrop, followed b y 24.9%
Aflee, 24.7%
T h e estimated total harvest
O f the fish examined, 41.2% w e r e
Erwin, a n d 6.4%
DeSmet.
T e n fish
w e r e creeled with undistinguishable m a r k s (Table 2).
Analysis c£ length-frequency distributions of Winthrop a n d Erwin strains
prior to stocking a n d f r o m s u m m e r creel survey data revealed no skewness or
kurtosis (Figures 6, 7; Tables 3-5).
O n e - w a y analysis c£ variance test revealed
significant differences in distribution of m e a n s b e t w e e n the prestocking data
a n d the creel survey data from both strains.
T h e E rwin distributions, however,
s h o w e d heterogeneity cf variances thus invalidating the A N O V A test. Significant
differences in m e a n location b e t w e e n E r w i n prestocking data a n d creel survey
data w e r e confirmed using nonparametric rank order analysis of variance test
(Kruskal-W allis
one-way).
Standard
deviations
of
the
length-frequency
distributions for the Erwin strain w e r e significantly different from prestocking
data
and
creel survey data.
The
Winthrop
strain s h o w e d
no
difference in
standard deviations for prestocking or s u m m e r creel survey data.
Although
Aflee
strains h a d significant differences in length-frequency
distribution means, the prestocking distribution w a s lepitokurtotic precluding a n y
conclusions about differences in variability (Figure 8; Tables 3-5). D e S m e t strain
14
length-frequency distributions w e r e not analyzed due to insufficient sample size
(Figure 9; Tables 3, 4).
Mean
catch per unit effort for p o n d I w a s
0.49 fish per hour.
Total
n u m b e r cf hours fished w a s 673.16, with the heaviest fishing effort observed in
stratum 2, although there w a s n o significant difference b e t w e e n strata 2, 3 a n d
4.
T h e p e a k catch rate, however, w a s in stratum 4 (TafcQe 6). In p o n d 2 m e a n
catch per unit effort w a s 0.597 fish per hour (Table I ) .
T h e total n u m b e r of
hours fished in p o n d 2 w a s 597.45, with p e a k effort in stratum 3.
catch rate w a s found in stratum 5.
s o m e of the lowest catch rates.
T h e highest
T h e periods of heaviest fishing pressure h a d
In p o n d I, stratum 2 h a d the heaviest fishing
pressure, but a C P U E of only 0.262, while in p o n d 2, stratum 3 h a d the heaviest
pressure with a C P U E of 0.678.
Condition Factor
A v e r a g e condition factors of rainbow trout creeled generally decreased
overall during the s u m m e r study period (Table 8) with the
Winthrop strain.
exception of the
In p o n d I, condition of D e S m e t rainbow trout decreased f r o m
1.23 to 1.03, Erwin from 1.28 to 1.07, a n d Aflee from 1.20 to 1.08.
in condition w a s observed for the
N o change
Winthrop strain b e t w e e n the beginning a n d
e n d of the creel survey. Similar results w e r e found in p o n d 2, with the Winthrop
strain increasing f r o m 1.11 to 1.27 in stratum 5 a n d declining to 1.08 b y the e n d
of the study.
There
was
no consistency among
condition factor was at a maximum.
strains in either pond as to when
In pond I DeSmet showed a summer high in
stratum seven, while Winthrop condition was highest in strata one and two
(Table 8).
POND I
POND 2
STRAIN
F i g u r e 5. P e r c e n t a g e o f t o t a l c a t c h o f r a i n b o w t r o u t c r e e l e d
b y s t r a i n in P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a , 1 9 8 2 .
(D = D e S m e t , E = E r w i n , W = W i n t h r o p , A = A r l e e ) .
T a b l e I. R e c o r d e d c a t c h o f e a c h s t r a i n o f r a i n b o w t r o u t
e x t r a p o l a t e d totals from creel census conducted at Pond
Three Forks, Montana.
J u n e 8 t o S e p t e m b e r 12 , 1 9 8 2 .
Date
Stratum
DeSmet
Erwin
Winthrop
Arlee
Unidentified
Recorded
Total
and
I,
Total Extrap­
olated Catch
Percent
Total
I
6-8 to 6— 12
0
0
31
3
0
34
103
10.3
2
6-13 to 6-26
I
6
31
4
0
42
102
12.7
3
6-27 to 7-10
I
18
33
12
6
70
173
21.2
4
7-11 to 7-24
7
14
51
41
0
113
387
34.2
5
7-25 to 8-7
2
13
6
12
0
33
70
10.0
6
8-8 to 8-21
0
0
0
0
I
I
4
0.30
7
8-22 to 9-4
3
5
5
I
I
15
41
4.6
8
9-5 to 9-12
3
8
4
7
0
22
62
6.7
17
64
161
80
8
330
945
24.2
2.4
TOTAL
PERCENT TOTAL
5.2
19.4
48.8
T a b l e 2. R e c o r d e d c a t c h o f e a c h s t r a i n o f r a i n b o w t r o u t
extrapolated totals from creel census conducted at Pond
Three F o r k s , Montana.
J u n e 8 t o S e p t e m b e r 12, 1 9 8 2 .
Erwin
Date
Stratum
Winthrop
Arlee
Unidentified
Recorded
Total
and
2,
Total Extrap­
olated Catch
Percen
Total
I
6-8 to 6-12
i
I
6
I
0
9
26
2.5
2
6-13 to 6-26
2
21
38
15
4
80
221
22.4
3
6-27 to 7-10
10
34
55
31
0
130
242
36.4
4
7-11 to 7-24
2
3
14
9
3
31
87
8.7
5
7-25 to 8-7
2
12
16
10
0
40
6
8-8 to 8-21
3
8
8
11
0
30
75
8.4
7
8-22 to 9-4
I
8
7
9
2
27
65
7.6
8
9-5 to 9-12
2
I
3
3
I
10
20
2.8
23
88
147
89
10
357
846
TOTAL
PERCENT TOTAL
6.4
24.7
41.2
24.9
2.8
HO
11.2
H
18
PRIOR TO
STOCKING
POND I
POND 2
— i~~
ISO
T"'
170 ISO ISO 200 210 220 230 240 250 260 270 280 290 300
310 320
LENGTH (mm)
F i g u r e 6. L e n g t h f r e q u e n c y h i s t o g r a m s o f c r e e l
s u r v e y d a t a f r o m P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a
c o m p a r e d to p r e - s t o c k i n g d a t a for W i n t h r o p r a i n b o w
trout.
( N u m b e r s in b l o c k s r e p r e s e n t s t r a t u m in w h i c h
fish were caught.)
19
PRIOR TO
STOCKING
X
POND I
160
ITO ISO
ISO 200
ZIO 220 230 240 250 260 270 280 290 300
L E N G T H (mm)
F i g u r e 7. L e n g t h f r e q u e n c y h i s t o g r a m s of c r e e l
s u r v e y d a t a f r o m P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a
c o m p a r e d to p r e - s t o c k i n g d a t a for E r w i n r a i n b o w
trout.
(N u m b e r s in b l o c k s r e p r e s e n t s t r a t u m in w h i c h
fish were c a u g h t . )
20
PRIOR TO
STOCKING
40
POND I
POND 2
160
170
180
ISO 200 2)0 220 230 240 250 260 270 280 290 3 0 0
LENGTH (mm)
F i g u r e 8. L e n g t h f r e q u e n c y h i s t o g r a m s of c r e e l
s u r v e y d a t a f r o m P o n d s I a n d 2, T h r e e F o r k s , M o n t a n a
c o m p a r e d to p r e - s t o c k i n g d a t a for A r l e e r a i n b o w
trout.
( N u m b e r s in b l o c k s r e p r e s e n t s t r a t u m in w h i c h
fish were c a u g h t . )
21
PRIOR TO
STOCKING
X
CO
Lu
U-
O
or
IOt
POND I
5"
I
3
7__ j__3_
Z
4
2
4
7
~i
3
4---'
---1
POND 2
-j160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330
LENGTH (mm)
F i g u r e 9. L e n g t h f r e q u e n c y h i s t o g r a m s of c r e e l
survey data from Ponds I and 2 , Three F o r k s , Montana
c o m p a r e d to p r e - s t o c k i n g d a t a for D e S m e t r a i n b o w
trout.
(N u m b e r s in b l o c k s r e p r e s e n t s t r a t u m in w h i c h
fish were c a u g h t . )
T a b l e 3. L e n g t h f r e q u e n c y d i s t r i b u t i o n s o f r a i n b o w t r o u t
s t r a i n s f r o m c r e e l s u r v e y d a t a f o r P o n d I.
C o n d u c t e d at
T h ree Forks Ponds, Montana, 1982.
(W=Winthrop, E=Erwin,
D = D e S m e t , A = A r l e e ; n u m b e r s r e p r e s e n t n u m b e r s of fish c a u g h t
o f t h a t s t r a i n .)
Length Interval (mm)
Strata I
Strata 2
Strata 3
Strata 4
Strata 5
Strata 6
Strata 7
Strata 8
320-329
310-319
290-299
W = I
W = 2
280-289
W = I
W = I
W = 3
W = 6
270-279
W = 4
W = 3
E = I
W = 4
E = I
W = 4
E = 2
A = 3
W = I
E = 2
W=I
W = I
E = I
A = I
260-269
W = 4
W = 2
W = 5
E = 2
W = 9
E = I
A = 2
W = 3
E = 4
A = 2
0 = 2
W = I
E = I
A = I
W = 2
E = 2
A = 4
E = 5
A = I
W= 2
E = 3
W=I
E = 4
A = 2
0 = I
250-259
W = 4
W=S
E = 2
W = 5
E = 3
D = I
D = I
M
D = I
0= 2
240-249
W = 3
W = 5
E = 2
W = 6
E = 8
A = I
W = 15
E = 2
A = 12
D = I
E = 2
A = 3
W =
E =
D = I
0= 2
230-239
W = 5
W = 5
W = 6
E = 3
A = 5
W = 7
E = 6
A = IO
0= 2
E = I
A = 4
W = I
E = I
A = 1
D = I
I
I
W=I
E = 2
A = I
A = I
M
Table
3.
(continued).
Length Interval (mm)
Strata I
Strata 2
Strata 3
Strata 4
Strata 5
220-229
W = S
A = I
U = S
A = 2
E = I
W = 4
A = 4
W = S
E=I
A = 6
W = 2
A ='2
210-219
W = 4
W = 3
A = I
A = 2
W = 3
A = I
200-209
A = 2
W = I
W = I
A = I
5:1
D -'
190-199
I
Strata 6
Strata 7
Strata 8
B
Length Interval (mm)
Strata I
Strata 2
Strata 3
Strata 4
Strata 5
320-329
0 = I
310-319
W = I
300-309
W = I
290-299
280-289
W = I
270-279
W = I
W = I
D = I
W = 2
W = 3
E = 2
D = I
W = 3
E = I
W = 2
E = 4
A = I
W = I
W = 4
E = 2
W
E
A
0
=
=
=
=
5
3
I
2
250-259
W = 2
W
E
A
0
W
E
A
0
=
=
=
=
16
10
3
3
240-249
LU
W = 5
E = 6
A = I
Il
260-269
=
=
=
=
8
8
I
I
W = 7
E = 7
A = 9
W = I
Strata 6 Strata 7
W = I
E = I
W = I
E = I
W = 2
E = 2
A = I
E = I
W = I
A = I
0 = I
W
E
A
D
W = 2
E = 4
A = I
W = 3
E = I
W = 3
E = I
A = 6
D = I
Strata
=
=
=
=
2
2
3
I
E = I
A = I
W
E
A
D
=
=
=
=
E = I
A = I
I
I
3
I
W = I
D = I
W = 2
E = 3
W = 2
A = I
W = 3
E = 4
W = I
A = 4
D = I
W = 2
E = 4
A = I
W = I
D = I
W = 2
A = 4
W = I
E = 2
W = I
A = 2
W = I
A = I
to
Table
4.
(c o n t i n u e d ).
Length Interval (mm)
Strata I
Strata 2
Strata 3
Strata 4
Strata 5
Strata 6 Strata 7
230-239
W = 2
W = 6
E = 3
A = 4
W=IO
E = S
A = 12
D = I
W = I
A = 3
D = I
W = 2
A=I
W = 4
E = I
W
E
A
D
=
=
=
=
S
2
3
I
W = 4
E = I
A = 3
W = 2
W = I
A = I O = I
W = I
A = 2
W
E
A
D
=
=
=
=
6
I
I
I
W = I
E = I
A = 2
W = 3
A = 2
A = I
W = I
220-229
D = I
A = 5
210-219
D = I
200-209
190-199
A = I
W = I
Strata 8
E = I
A = I
A=I
iv
Ul
T a b l e 5. A n a l y s i s o f l e n g t h
rainbow trout strains prior
creel surv e y data for T h r e e
Pre-stock
Winthrop
Pond I
Pond 2
f r e q u e n c y d i s t r i b u t i o n s of
to s t o c k i n g a n d f r o m s u m m e r
Forks Ponds, Montana.
Pre-stock
Erwin
Pond I
Pond 2
Pre-stock
Arlee
Pond I
Pond 2
n =
200
161
147
200
64
88
200
80
89
Mean
228.157
249.150
249.095
228.095
248.047
253.977
205.465
233.900
241.416
S t d . Dev.
21.902
21.993
21.674
14.084
12.038
17.110
14.060
14.556
19.017
Skewness
-0.179
0.167
0.102
-0.323
0.244
-0.037
-0.951
-0.012
-0.022
Kurtosis
-0.399
-0.661
0.243
-0.110
-0.130
0.295
6.107
-0.091
0.498
27
Strata
No. fish cauqht
Total hours fished
Catch/hour
I .
34
57.29
0.593
2
42
160.48
0.262
3
70
154.64
0.453
4
113
144.50
0.782
5
33
72.50
0.455
6
I
19.75
0.051
7
15
23.00
0.652
8
22
41.00
0.537 ■
330
673.16
TOTAL"
0.490
T a b l e 7. O b s e r v e d c a t c h p e r h o u r o f e f f o r t i n e a c h
s t r a t a f o r P o n d 2, T h r e e F o r k s , M o n t a n a .
June 8 to
S e p t e m b e r 12, 1 9 8 2 .
Strata
No. fish cauoht
Total hours fished
Catch/hour
I
9
33.50
0.269
2
80
152.70
0.524
3
130
191.75
0.678
4
31
56.75
0.546
5
40
41.00
0.976
6
30
61.75
0.485
7
27
33.00-
0.818
8
■JO
27.00
0.370 '
357
597.45
TOTAL
0.597
T a b l e 8. M e a n c o n d i t i o n f a c t o r f o r D e S m e t , W i n t h r o p , E r w i n
a n d A r l e e s t r a i n s of r a i n b o w t r o u t at the b e g i n n i n g of the
s t u d y a n d d u r i n g c r e e l survey. T h r e e Forks, M o n t a n a , 1982.
Pond I -
Strain
Pre-Btocklnq
Stratum
5
6
7
8
0.99
7
1.05
2
0
1.11
3
1.03
3
1.03
17
1.11
18
1.07
14
1.05
13
0
1.13
5
1.07
8
1.11
120
0
1.02
5
1.04
4
1.07
105
0
1.02
I
1.03
7
1.08
80
I
2
3
4
0
1.13
I
0.92
I
1.15
31
Creel Survey Mean
DeSmet
n =
1.23
200
Winthrop
n =
1.11
200
Erwin
n =
1.28
200
0
1.12
6
1.13
33
1.04
51
1.07
6
Arlee
n =
1.20
200
1.18
3
1.12
4
1.01
12
1.09
12
1.09
12
DeSmet
n =
1.23
200
0.97
I
1.07
2
1.11
10
1.08
2
1.02
2
1.20
3
1.13
I
1.10
2
1.09
23
Winthrop
n =
1.11
200
1.09
6
0.98
38
1.11
55
1.26
14
1.27
16
1.25
8
1.08
3
1.08
3
1.14
147
Erwin
n =
1.28
200
1.15
I
1.17
21
1.11
34
1.17
3
1.12
12
1.16
8
1.01
I
1.01
I
1.11
88
Arlee
n =
1.20
200
1.00
I
1.07
15
1.04
31
1.08
9
1.13
10
1.07
11
1.06
3
1.06
6
1.06
89
1.18
31
—
Pond 2
29
A
two-way
analysis
of
variance s h o w e d
a
significant overall difference in
condition factors b e t w e e n ponds I a n d 2 at the e n d of the study period. Overall
in
both
between
ponds
the
there
was
Winthrop
a 'significant difference in
strain
and
difference from the Erwin strain.
the
Erwin.
These s a m e
the
DeSmet
and
the
average
Arlee
condition
strains,
but
no
T h e D e S m e t w a s significantly different from
differences
w e r e also true for p o n d
2. S u m m e r gill
netting data for p o n d I s h o w e d m e a n condition factors of 0.93 for D e S m e t f 1.03
for Erwin, 1.04 for Winthrop, a n d 1.00 for Aflee (Table 8).
P o n d 2 gill netting
data s h o w s m e a n condition factors cf 1.28 for DeSmet, 1.15 for Erwin, 1.06 for
Winthrop, a n d 1.00 for Aflee (Table 8).
Growth
G r o w t h data w e r e evaluated by plotting average weights for each strain
in
each
strata a n d the relationship w a s
(Figures 10-13).
evaluated using regression analysis
This is not a true regression line as e a c h
represents a different n u m b e r cf cases examined.
a weight trend for each strain over time.
average
weights
J a n u a r y 1983.
obtained f r o m
average plotted
This line does, however, s h o w
T h e final value plotted is based o n
gill netting
during
population
estimation
in
All strains g r e w at a higher rate in p o n d 2. T h e Winthrop strain
h a d the fastest a n d largest weight gain in both ponds over all strains. Following
the Winthrop in weight gain w a s Erwin, A d e e , a n d DeSmet, respectively.
T emperatu r e a n d W a t e r Quality
M e a n water temperature increased through the sampling period a n d w a s
similar b e t w e e n ponds.
W a t e r temperature r a n g e d f r o m 20.3 to 23.7 ° C with the
highest water temperature in August.
On
sampling dates, m e a n temperature
varied n o m o r e than 0.9 degrees b e t w e e n ponds (Table 9). T h e r e w a s no thermal
stratification detected in either p o n d during a n y of the sampling times.
30
PONO I
r = .12
12 3 4 5 6 7 8
STRATA
290S
POND 2
230
170
2 3 4 3 6 7 8
STRATA
F i g u r e 10. R e l a t i o n s h i p b e t w e e n t i m e s t r a t u m a n d
m e a n w e i g h t o f D e S m e t r a i n b o w t r o u t in P o n d s I a n d
2, f r o m c r e e l s u r v e y d a t a . T h r e e F o r k s , M o n t a n a ,
1982.
S t r a t a 1-8 r e p r e s e n t two w e e k i n t e r v a l s s t a r t ­
i n g J u n e 6, 1 9 8 2 .
T h e d a t a p o i n t s at s t r a t u m 14 a r e
t h e a v e r a g e w e i g h t s of f i s h c o l l e c t e d by g i l l net s
on J a n u a r y 5-14, 1983.
31
SOOr
255
POND I
210
165-
2 3 4 5 6 7 8
STRATA
300t
POND 2
255 '
r * .97
210
165-
STRATA
F i g u r e 11. R e l a t i o n s h i p b e t w e e n t i m e s t r a t u m a n d
m e a n w e i g h t of E r w i n r a i n b o w t r o u t in P o n d s I a n d
2, f r o m c r e e l s u r v e y d a t a , T h r e e F o r k s , M o n t a n a ,
1982.
S t r a t a 1-8 r e p r e s e n t two w e e k intervals s t a r t ­
i n g J u n e 6, 1 9 8 2 .
T h e d a t a p o i n t s a t s t r a t u m 14 a r e
t h e a v e r a g e w e i g h t s of f i s h c o l l e c t e d by g i l l n e t s
on J a n u a r y 5-14, 1983.
32
300T
260
PONO I
2 20
r = .79
STRATA
260
POND 2
r = .91
220
180
STRATA
F i g u r e 12. R e l a t i o n s h i p b e t w e e n t i m e s t r a t u m a n d
m e a n w e i g h t of W i n t h r o p r a i n b o w t r o u t in P o n d s I
a n d 2, f r o m c r e e l s u r v e y d a t a . T h r e e F o r k s , M o n t a n a ,
1982.
Strata 1— 8 represent two week intervals
s t a r t i n g J u n e 6, 1 9 8 2 .
The data points at stratum
14 a r e t h e a v e r a g e w e i g h t s of f i s h c o l l e c t e d by
g i l l nets on J a n u a r y 5-14, 1983.
33
246
POND I
r K .86
135
12 3 4 5 6 7 8
STRATA
POND 2
r = 92
190
12
3 4 5 6 7 8
STRATA
F i g u r e 13. R e l a t i o n s h i p b e t w e e n t i m e s t r a t u m a n d
m e a n w e i g h t of A r l e e r a i n b o w t r o u t in P o n d s I a n d
2, f r o m c r e e l s u r v e y d a t a , T h r e e F o r k s , M o n t a n a ,
1982.
Strata 1-8 represent two week intervals start­
i n g J u n e 6, 1 9 8 2 .
T h e d a t a p o i n t s a t s t r a t u m 14 a r e
t he a v e r a g e w e i g h t s of f i s h c o l l e c t e d by g i l l nets
on J a n u a r y 5-14, 1983.
34
Table
Ponds
9. W a t e r
I a n d 2.
chemistry and temperature data
Three F o r k s , M o n t a n a , 1982. *
June 24
Pond I Pond 2
July 25
Pond I Pond 2
August 24
Pond I Pond 2
Alkalinity
(ppm C a C O 3 )
190
178
180
169
228
207
Hardness
(ppm C a C O 3 )
176
240
150
223
168
230
DO
8.2
8.8
7.6
7.5
6.2
7.5
8.5
8.6
8.5
8.6
8.5
8.6
20.4
20.3
23.5
22.6
23.7
23.6
(ppm)
PH
Temp.
Secchi
(0 C)
2.1
(meters)
for
3.64
♦Values listed represent averages of three values taken at three depths
( . C l 1.82m# 2,73m)
at two sampling stations.
35
Alkalinity w a s similar b e t w e e n ponds a n d w a s highest in A u g u s t (Table 9).
I s h o w e d l o w e r hardness values for all m o nths than p o n d 2.
differed b y 60 to 70 p p m less in e a c h m o n t h sampled.
Pond
P o n d I values
T h e p H levels in both
ponds rem ained constant a n d w e r e nearly identical.
Dissolved o x y g e n declined
slightly in both ponds throughout the study period.
Secchi disc readings w e r e
also taken in each p o n d in August.
Pond I showed a
2.1 m
depth of light
penetration, while p o n d 2 w a s 3.64 m.
Population Estimate
A
population estimate w a s m a d e for p o n d I o n J a n u a r y 5-7, 1983 a n d
p o n d 2 o n January 12-14, 1983 after planting a n additional 350 a n d 250 m a r k e d
fish, respectively, 10 w e e k s before gill netting.
O f 78 fish netted in p o n d I, 28
w e r e recaptures (fish with caudal punch), 16 w e r e DeSmet, 6 w e r e Erwin, 13
were
Winthrop,
and
956+277 (95% CJ.).
DeSmet,
2
were
8
were
Arise.
The
strain
Erwin, 4
was
population
estimate
was
O f 62 trout sampled in p o n d 2, 45 w e r e recaptures, 3 w e r e
were
Winthrop, a n d
estimate for p o n d 2 w a s 344+52 (95%
DeSmet
Petersen
caught
the
CJ.).
least
(5.2%
I was
Aflee.
T h e population
B a s e d o n creel survey data, the
and
6.4%
in
ponds
I
and
2,
respectively) a n d should therefore b e m o s t a b undant in the population (Tables
10, 11).
Gill netting data support this, with the D e S m e t strain netted in the
highest percentage in p o n d I.
determination.
Pond
2 samp l e size
w a s insufficient for this
T a b l e 10. P e r c e n t b y s t r a i n of c a t c h f r o m s u m m e r
s u r v e y a n d J a n u a r y g i l l n e t t i n g in P o n d I f T h r e e
M o n t a n a , 1982-1983.
n =
Creel Survey
5.2
17
Erwin
■
DeSmet
Gill Nettino
'37.2
16
19.4
6.4
14.0
6
n =
48.8
161
30.2
13
Arlee
n =
24.2
80
18.6
8
n =
Wlnthrop
T a b l e 11. P e r c e n t b y s t r a i n of c a t c h f r o m s u m m e r
s u r v e y a n d J a n u a r y g i l l n e t t i n g i n P o n d 2, T h r e e
M o n t a n a , 1982-1983.
Creel Survey
DeSmet
creel
Forks,
Gill Nettinq
n =
6.4
23
30
3
Erwin
n =
24.7 ■
88
20
2
Winthrop
n =
41.2
147
40
4
Arlee
n =
24.9
89
10
I
creel
Forks,
37
DISCUSSION
Creel S u rvey
Domestic strains of rainbow trout h a v e generally b e e n s h o w n to b e m o r e
susceptible to angling than wild or semi-wild strains (Dolan a n d Piper, 1979;
Fay, 1982; D w y e r a n d Piper, 1984).
M y results support this generalization a n d
also suggest that relative susceptibility m a y b e related to the length of time a
strain has b e e n domesticated.
has been
O f the four strains tested, t he Winthrop strain
domesticated the longest (since 1936) a n d w a s
the
m o s t catchahle
(48.8% a n d 41.2% of the catch in ponds I a n d 2 respectively).
The
Winthrop
strain w a s follow e d in catchabdlity b y Arlee (24.2%, 24.9%) a n d E rwin (19.4%,
24.7%),
domestic
respectively.
strains
which
have
been
cultured
since
1955
and
1973,
T h e semi-wild D e S m e t strain w a s the least catchahle of those
tested, m aking u p only 5.2%
a n d 6.4%
of the creeled fish in ponds I a n d 2
relationship b e t w e e n length
of domestication a n d catchabdlity w a s
respectively.
The
also seen in the Dolan a n d Piper (1979) study.
Winthrop strain
was
creeled the
O f the four strains tested, the
m o s t followed b y
M c C o n a u g h y , a n d Fish L a k e strains.
Spring
Standard
Growth,
T h e Fish L a k e strain w a s o ne generation
r e m o v e d f r o m the wild, t h e M c C o n a u g h y strain t w o generations r e m o v e d f r o m
the wild a n d the Spring Standard G r o w t h a n d Winthrop strains w e r e domestics.
In addition. F a y (1982) f ound that the domestic strains of Fish Genetics L a b
Standard Winter a n d Ennis domestic strains exhibited a
higher return to the
creel over the wild Fish L a k e a n d M c C o n a u g h y strains.
Length-frequency
distribution
analysis, for
the
Winthrop
strain
shows
differences in m e a n s but n o difference in variability b e t w e e n prestocked fish
a n d creeled fish.
This implies that there is n o length susceptibility to angling.
38
The
differences in m e a n s is probably
difference in variability for the
a reflection of s u m m e r
Erwin
strain, however,
growth.
combined
with
The
the
differences in means, supports the notion of possible length susceptibility to
angling.
T h e size groups stocked in the highest proportions did not appear to b e
the s a m e as those caught.
N o conclusions or inferences c an b e m a d e regarding
size susceptibility to angling for Arlee a n d DeSmet.
Total angler harvest of 18.6 % a n d 27.1 % in p o n d I a n d 2 (Tables I, 2),
respectively is l o w
c o m p a r e d to other rainbow trout strain evaluation studies
conducted in these ponds.
In 1978 the harvest w a s estimated a t 5 2 % a n d 45%,
respectively, in
and
ponds
I
34.7% K D w y e r a n d Piper, 1984).
2
with
similar
estimates in
1979
(44.8%
and
Th e s e previous studies did not utilize the s a m e
rainbow trout strain combination used in this study, a n d that m a y account for
the differences in angler harvest.
Comparisons can b e m a d e h o w e v e r b e t w e e n
the harvest of the Winthrop domestic strain.
D w y e r a n d Piper (1984), evaluating
the Spring Standard G r o w t h a n d Winthrop strains, f o u n d 60-83 % of the strains
caught in both years of their study.
In m y
study, only 1 8 %
Winthrop strain w e r e harvested in ponds I a n d 2, respectively.
and 20%
of the
The Dwyer and
Piper (1984) study did not report fishing pressure so it is not k n o w n if angling
pressure w a s significantly different from m y study.
T h e catch rate w a s less than o n e fish per hour in both ponds during all
fishing periods.
Only in p o n d 2 did C P U E a p proach o n e (strata 5 a n d 7), with
m o s t ether values ranging -f r o m 0.782 d o w n to 0.051 (Table 7).
Although g o o d
temperature data are not available, fishing pressure a n d catch rate decreased
throughout the s u m m e r , while temperature increased.
A U rainbow trout strains evaluated maintained ade q u a t e coefficient of
condition throughout the study. Piper et a L (1982) considered a condition factor
39
of 1.12 as optimal for rainbow, brook a n d b r o w n trout.
D w y e r a n d Piper (1984)
reported similar findings with n o significant differences a m o n g
strains.
The
Winthrop strain used b y Dolan a n d Piper (1984) s h o w e d a condition factor of
0.907 at the termination of their s u m m e r creel survey.
This c o m p a r e s well with
the m e a n s u m m e r average of 1.11 a n d 1.14 calculated for the Winthrop strain in
my
study
in
ponds
I
and
2
respectively
(Table
8).
The
Winthrop
strain
maintained the highest m e a n condition factor of all strains in both ponds.
Winthrop strain also exhibited the fastest g r o w t h
The
a n d attained the heaviest
weight in both ponds, followed b y the Erwin, Arlee, a n d D e S m e t (Figures 10-13).
This is consistent with the previous evaluations by Dolan a n d Piper (1979) a n d
D w y e r a n d Piper (1984) in which the Winthrop domestic strain g r e w faster a n d
maintained a higher condition than t w o
wild strains u n d e r hatchery a n d field
conditions.
Dolan a n d
Piper
(1979)
and
Dwyer
and
Piper
(1984) reported gradual
decline in condition of all strains tested. Although small sample size often m a d e
similar comparisons difficult, I observed th e s a m e trend.
factors w e r e consistently less than in p o n d 2 (Table 8).
In p o n d I, condition
Insufficient data w e r e
collected to speculate o n the differences b e t w e e n ponds.
T emperatu r e a n d W a t e r Quality
W a t e r chemistry values for all parameters m e a s u r e d fell within acceptable
levels for salmonids (US E P A , 1976).
p o n d I.
Hardness values w e r e larger in p o n d 2 than
Alkalinity, however, w a s similar b e t w e e n ponds, implying the carbonate
content did not vary.
B a s e d o n charge balances calculated f r o m hardness a n d
alkalinity values, the higher hardness in p o n d 2 (with similar alkalinity readings
to p o n d I) w a s d u e to the presence of other non-carbonate anions which balance
the calcium a n d m a g n e s i u m cations.
40
Secchi readings s h o w e d clearer w a t e r in p o n d 2 than p o n d I which m a y
h a v e b e e n d u e to a n a b u n d a n c e c£ phytoplankton present in the w ater in p o n d I
limiting
light
penetration.
Piankton
sampling
and
total
dissolved
solids
m e a s u r e m e n t s w e r e not done, so the significance c£ the secchi m e a s u r e m e n t is
not known.
W a t e r temperature increased slightly (20.3-23.7°C) as s u m m e r progressed
a n d w a s considerably higher than "optimal" for rainbow trout.
D w y e r (1981)
reported the optimal range for physiological performance as b e t w e e n 15-18°C.'
Outside cf this range, fish b e c a m e less active a n d f ed less, resulting in a drop
in condition.
Dickson a n d K r a m e r (1971) reported the highest scope for activity
for hatchery a n d wild rainbow trout is in the temperature range of 1 5 -20°C .
T h e y also reported that the scope for activity for hatchery a n d wild rainbow
trout w a s similar except at 2 5 ° C w h e n it w a s significantly higher for wild trout
( D e S m e t strain).
There
w a s n o attempt to correlate the
obvious discrepancies in w a t e r
quality (hardness a n d secchi readings) to differences in fish g r o w t h b e t w e e n
ponds.
W a t e r quality m e asuremen t s w e r e taken only to specify the conditions
under which the fish w e r e evaluated.
Population Estimate
The
post-study
population
estimate
in
January
1983
supports
the
conclusion that the D e S m e t strain w a s harvested the least, since it w a s present
in the highest n u m b e r s in gill n e t samples t a k e n in January. T h e Winthrop strain
which h a d the largest harvest, however, also m a d e u p a large proportion of fish
s a mpled b y gill nets.
This m a y b e a reflection of a higher susceptibility to gill
netting, population densities corresponding to net set locations, or high survival
a n d high catchability.
41
Population estimates for both ponds suggest l o w survival.
of
5,080 fish planted,
945
or 1 9 %
were
estimated to
have
In p o n d I, out
been
caught b y
anglers a n d only an estimated 956+277 or 1 9 % of the fish rem a i n e d at the e n d
of the
survey leaving
estimated 846 or 2 7 %
3,179
or
62%
u n a c c o u n t e d for,
w e r e caught a n d 344+52 cr 1 1 %
while in p o n d
2
an
r e m a i n e d of the 3,120
fish planted leaving 1,930 or 6 2 % u n a c c o u n t e d for.
T h e creel survey e n d e d in September, 1982 a n d the population estimate
w a s conducted in January, 1983.
fishermen after the
Although s o m e fish w e r e probably harvested b y
creel survey ended, this n u m b e r is expected to b e l o w
because surface ice o n the ponds a n d cold winter temperatures probably detered
m a n y of the local fishermen.
However, previous studies b y D w y e r a n d Piper
(1984) conducted the population estimate immediately following the termination
of the
creel survey.
It is possible that m a n y
more
fish
fishermen during this period (September to January) than
w o u l d give a misleadingly l o w population estimate.
were
removed
w a s a s s u m e d which
T h e m e t h o d of population
estimation used in this study w a s the adjusted Petersen model.
Implicit in this
m o d e l are s o m e conditions that m u s t b e m e t for the analyses to b e valid.
are: the m a r k e d fish suffer the s a m e
marked
fish are
as vulnerable
to
by
T hese
natural mortality as the unmarked, t he
the
fishing
being
carried o n
as are
the
u n m a r k e d ones, the m a r k e d fish b e c o m e ran d o m l y mixed with the unmarked, the
m a r k e d fish d o not lose their mark, all m a r k s are recognizable a n d reported o n
recovery a n d there is a
negligable a m o u n t
of recruitment to the catchable
population during the time the recoveries are being made.
It is possible in this study that s o m e of these assumptions m a y ha v e b e e n
c o m p r o m i s e d or violated.
T h e D e S m e t strain w a s the only strain available for
restocking for the purpose cf population estimation.
The
D e S m e t strain m a y
42
exhibit different mortality than the other strains found in the population which
would, violate the first assumption of equal mortality a m o n g strains.
Further, it
w a s a s s u m e d that if there w a s a difference in vulnerability to fishing b e t w e e n
m a r k e d a n d u n m a r k e d fish, this n u m b e r would b e negligible because of very lo w
fishing pressure.
It w a s also a s s u m e d that the m a r k e d fish did b e c o m e randomly
m i x e d with the u n m a r k e d fish.
Considering the conditions of m a r k e d fish not
losing their m a r k a n d .all m arks
being recognized a n d reported o n
recovery
reveals s o m e problems. In this study the m a r k e d fish w e r e tagged using a caudal
punch. During the gill-netting process, m a n y of the caudal fins w e r e torn, a n d it
is possible that s o m e tears w e r e misidentified as caudal punches.
inflate the
recapture ratio
There
no
was
and
recruitment to
give
the
misleadingly l o w
catchable
This would
population
population.
Aside
estimates.
from
these
considerations, it appears that natural mortality w a s large in both ponds.
Using gill netting data as the primary measure of survival rather than
creel
survey
catchability.
data
eliminates
the
possible
bias
of
Gill net samples taken in J a n u a r y 1983
survival of fish stocked in ponds I a n d 2, respectively.
strain
show
differences
a
19%
and
in
11%
It is well d o c u m e n t e d
that s o m e hatchery strains h a v e l o w survival in natural waters.
H u d y (1980)
reports survival of rainbow trout stocked in Porcupine Reservoir, Utah at 6.7%
in a 24 m o n t h study a n d 7.1% in a 14 m o n t h study.
H e concluded his loss of
stocked fish w a s due to stress factors within the reservoir.
Flick a n d Webster
(1976) report a consistently high mortality rate for domestic brook trout stocked
in natural ponds.
T h e y found f e w
of t h e m lived b e y o n d a g e
2+ years. T h e y
conclude that their domestic strains lacked inherent capacity to survive. Jenkins
(1971)
suggested
that
behavioral
patterns
of
domesticated
hatchery
trout,
successful in a c r o w d e d hatchery raceway, are ill-adapted t o the conditions in a
43
natural stream environment.
Hatchery r a c e w a y s represent very controlled environments with regulated
temperatures a n d a n a b u n d a n c e cf pelleted food.
a
pond, fish m u s t tolerate temperature
found in hatchery raceways.
In the natural environment of
fluctuations often
Feeding strategies b e c o m e
well a b o v e those
critical, in that fish
m u s t recognize a n d feed o n natural f o o d items. B a c h m a n (1984) suggested that a .
major cause
energy.
cf
mortality a m o n g
hatchery trout is excessive
expenditure
of
H e felt that hatchery trout in stream studies fed less often than wild
trout, p o ssibly because it takes considerable time for the hatchery trout to
I e a m to feed o n natural food items, a n d h e suggested that s o m e never do.
Condition of fish at time cf stocking is another important consideration
w h e n speculating o n possible causes of mortality.
strains
may
be
attributable
to
rearing
S o m e natural mortality a m o n g
d ifferences
at
different hatcheries.
H a s m e r et a L (1979) reported that different hatchery procedures h a v e an effect
o n returns cf Atlantic salmon to rivers in Maine.
F o w l e r (1972) found that
g r o w t h a n d mortality cf fingeding Chinook salmon w e r e effected b y e g g size.
T h e Winthrop a n d D e S m e t strains w e r e reared in the s a m e hatchery (Fish
Technology Center, B o z e m a n ) while the A d e e a n d Erwin strains w e r e obtained
f r o m t w o different hatcheries ( A d e e fr o m Bluewater State Hatchery, M T ; Erwin
f r o m Ennis National Fish Hatchery, MT).
found a t the B o z e m a n
hatchery w e r e
ft is possible that rearing conditions
m o r e favorable to survival of the fish
w h e n stocked a t Three Forks, although n o actual rearing data w e r e ccQlected
f r o m a n y cf the hatcheries.
44
Conclusions a n d M a n a g e m e n t R e c o m m e n d a t i o n s
This study supports well reported facts that there are differences in fish
p e f o r m a n c e a m o n g strains.
T h e domestic strains of Winthrop, E rwin a n d ArLee
out-performed the wild D e S m e t strain in g r o w t h a n d catchability.
This is a n
important assessment w h e n trying to max i m i z e returns to the creel a n d angler
satisfaction.
primary
In a p o n d situation such as this, those qualities are considered
objectives
for
maintaining
a
put-grow-take
fishery.
Although
the
D e S m e t a n d Winthrop strains did a p p e a r to ha v e the "highest" survival of the
strains evaluated, n o n e w e r e considered high in terms of the total n u m b e r of
fish stocked.
This is a continuing problem f a c e d b y m a n a g e m e n t biologists w h o
w o u l d like to have strains that are able to survive.
Field
evaluations
of
this
type
supply
important
information
to
the
hatchery m a n a g e r so that he m a y obtain m a x i m u m benefit in stocking programs.
T h e results of this study suggest that the
Winthrop rainbow
superior for a put-grow-take type of fishery.
g r o w t h a n d survival.
trout strain is
It exhibited high catchability,
T h e D e S m e t strain h o w e v e r w ould b e the strain of choice
if establishing a population c£ desirable fish w e r e the objective.
strain h a d the highest survival a n d the lowest catchability.
strain
was
steady throughout the
study.
The
Erwin
and
The DeSmet
G r o w t h of this
Arlee
strains are
probably best suited for stocking programs w h e r e longevity is not the main
objective.
45
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46
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47
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S n e d e c o r , G . a n d W. C o c h r a n . 1 9 6 7 .
S t a t e U n i v . P r e s s , Iowa.
Statistical
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1976.
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Quality
Wales, J.H. a n d D.P. B o r g e s o n . 1961. C a s t l e L a k e
investigation - third phase: R a i nbow trout.
and Game. 47:399-414.
Iowa
criteria
Calif.
Fish
49
APPENDIX
50
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FORM
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AMG-LCR
:
—
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I n t e r v i e w form u sed for creel s u r v e y at
M o n t a n a , J u n e 8 t o S e p t e m b e r 12, 1 9 8 2 .
I
-
-
Three
I
L
I
Forks
Ponds,
51
M G t-E re T D
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LCAKrTVI
LI*. KrVtr
ArJO L E R
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Data sheet used
Montana, June 8
in
to
creel su r v e y at Three
S e p t e m b e r 12, 1 9 8 2 .
I
Forks
I
Ponds
MONTANA STATE UNIVERSITY LIBRARIES
Main
Sir
M886
cop.2
OATE
t e l l e r , M a r y Ellen
F i e l d eva l u a t i o n of
four strains of...
ISSUED
to
----- —
M a in
N378
M886
cop. 2