A trout population study on a small creek in Gallatin County, Montana
by George D Holton
A THESIS Submitted to the Graduate Faculty in partial fulfillment of the requirements for the degree
of Master of Science in Fish and Wildlife Management
Montana State University
© Copyright by George D Holton (1952)
Abstract:
A study during two summers and the intervening winter was made of a rainbow, brook and brown trout
population in four sample sections of a small spring-fed creek in the Gallatin. Valley, Montana, A
direct current shocker was used for sampling the population. Fish taken were fin clipped and released.
Information was obtained on distribution of species in the creek, population changes' through the year',
movement and population stability, standing crops, age composition, survival, growth and
reproduction, Of 1,016 4-inch brook trout planted in August 1950, an estimated 5 per cent were left in
the 2 1/2 mile study area during the following calendar year.
Brook trout predominated in the upper part of the study area; rainbow trout, in the lower part. Rainbow
trout older than age group 0 had their maximum number in the first inventory of the year due to
recruitment of young fish and. gradually declined in number to the last inventory of the year. The loss
in total trout weight due to the reduction in number through the year was largely offset by the gain in
weight of individual fish. Brook trout (upper study section) and brown trout older than young of the
year showed a decided numerical increase during their spawning season. A population turnover greater
than expected from normal mortality and recruitment was indicated by low recoveries of marked fish
theoretically available and by the paucity of brook and rainbow trout over two years old. There was
evidence of limited movement. The standing crop per acre in the combined four study sections in
August 19.51 was estimated to be 4,586 trout or 106 pounds. At this time 80 and 85 per cent
respectively of the brook and rainbow trout numbers were in age group 0, 18 and 13 per cent were in
age group I and 2 per cent of each were in age group II.
Some individual brook and rainbow trout attained legal length (7 inches) in their second summer,
however, the majority did not reach this size until their second fall or the following spring. There were
an estimated 5,867 young of the year per mile the first fall and 5,468 per mile the second summer, A
collection of brook trout during their -spawning season showed that some young of the year males were
ripe and that at least 72 per cent of the fish over 6 Inches long were males. A TROOT POPULATION STUDY ON A SMALL GREEK
IN GALLATIN COUNTI5 MONTANA
by
GEORGE. D. HOLTON
A' THESIS
S u b m itted .to th e G rad u ate E a c u lty
in
.
p a r t i a l f u l f i l l m e n t o f t h e re q u ire m e n ts
f o r th e d e g re e o f
M aster o f S c ie n c e i n E is h and W ild lif e Management
at
Montana S t a t e C o lle g e
Approved
Head5 M ajor D epartm ent
GZhairman5 Exam ining Committee
Dean5 G raduate D iv is io n
Bbzeman5 Montana
March5 1952'
2
The Brook
I cane from h a u n ts o f coot and h e m ,
I make a sudden s a l l y ,
And s p a rk le out among th e f e r n .
To b ic k e r down a v a lle y .
I wind a b o u t, and in and o u t.
W ith h e re a blossom s a i l i n g .
And h e re and t h e r e a lu s t y t r o u t .
And h e re and th e r e a g r a y lin g ,
e
e
•
•
•
o
o
o
o
o
e
o
o
f
t
o
o
o
o
And out a g a in I curve and flo w
To jo in th e brimming r i v e r .
F or men may come and men may go.
But I go on f o r e v e r .
- Tennyson
3
TABLE OF CONTENTS
A b s tra c t -
_ _ _ _ _ _ _ _ _
I n tr o d u c tio n _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _
.— _ _ _ _ _ _ _
D e s c rip tio n o f c re ek
---- --- - - _ _
------- _ _ _ _ _ _ _ _ _ _ _ _ _ _
S tudy a re a and s e c tio n s - - - - - - - - - - - - - - - - T em peratures -
_ ----
- ---- _ _ _ _ _ _ _ _ _ _ _
Chem ical A nalyses _ _ _ _ _ _ _ _
- -
---- _ _ _ _ _ _ _
5
5
7
11
---- _ _ _ _ _
11
S p e c ie s o f f i s h p re s e n t - - - - - - - - - - - - - - - - - - -
13
M ethods _ _ _ _ _ _ _
---- _ _ _ _ _
Page
4
- ------- ---------------------------------------------------- _ -
P o p u la tio n I n v e n to r ie s
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
A geing-------------------_ _ _ _ --------- ---
_ ----- ------------ ----------------
13
13
17
_ _ _ _ _ _ _ _ _ _ _ _ _
18
- - ---- - - - - - - - - - - - - - - - - - - - - -
19
W ild t r o u t p o p u la tio n s - - - - - - - - - - - - - - - - - - - - - -
20
W eight assig n m en t (unw eighed f is h )
H a tch e ry f i s h -
D ates o f in v e n to r ie s
- - - - - - - - - - - - - - - - - - - -
20
S p e c ie s d i s t r i b u t i o n
- - - - - - - - - - - - - - - - - - - -
21
P o p u la tio n changes betw een in v e n to r ie s
- - - - - - - - - - -
22
Movement and p o p u la tio n s t a b i l i t y - - - - - - - - - - - - - -
29
D isc u ssio n o f p o p u la tio n s t a b i l i t y - - - - ---- _ _ _ _ _
31
33
S ta n d in g p o p u la tio n s Age com position — — — — — —
— — — — — — ~ — — — — — — — — — 34
37
Growth - - - - - - - - - - - - - - - - - - - - - - - - - - - -
38
N a tu ra l r e p r o d u c tion
40
- - - - - - - - - - - r - - - - -
43
L i t e r a t u r e c ite d - - - - - - - - - - - - - - - - - - - - - - -
45
Summary
- - -
- -
- -
- -
- -
'
4
' ABSTRACT
A stu d y d u rin g tw o summers and th e in te rv e n in g w i n t e r was made o f a
rainbow , brook and brown t r o u t p o p u la tio n i n f o u r sample s e c tio n s o f a
sm a ll s p r in g - f e d c reek i n th e G a lla tin . V a lle y , .M ontana, A d i r e c t c u rre n t
shocker was u sed f o r sam pling th e p o p u la tio n „ F ish ta k e n w ere f i n c lip p e d
and r e le a s e d . In fo rm a tio n was o b ta in e d on d i s t r i b u t i o n o f s p e c ie s, in th e
c re e k , p o p u la tio n changes' th ro u g h th e y ear', movement and p o p u la tio n
s t a b i l i t y , s ta n d in g c ro p s , age c o m p o sitio n , s u r v iv a l, grow th and rep ro d u c­
t i o n , Of 1,016 4 -in c h brook t r o u t planted" i n A ugust"1950, an e stim a te d
5 p e r c e n t w ere l e f t i n th e 2g m ile stu d y a r e a d u rin g th e fo llo w in g
c a le n d a r y e a r .
Brook t r o u t predom inated i n th e " u p p e r p a r t o f th e s tu d y a r e a ; rainbow
t r o u t , i n the" low er part". Rainbow t r o u t o ld e r th a n age group 0 had t h e i r
maximum number i n th e f i r s t in v e n to ry of" th e y e a r due t o re c ru itm e n t o f
young f i s h and. g r a d u a lly d e c lin e d i n number t o th e l a s t in v e n to ry o f th e
y e a r . The l o s s i n t o t a l t r o u t w eight due t o t h e re d u c tio n in number
th ro u g h t h e y e a r was la r g e ly o f f s e t b y th e g a in i n w eight o f in d iv id u a l
f i s h . Brook t r o u t (upper s tu d y s e c tio n ) and brown t r o u t o ld e r th a n young
o f t h e y e a r showed a d e c id e d n u m e ric al in c r e a s e d u rin g t h e i r spawning
s e a so n . A p o p u la tio n tu r n o v e r g r e a t e r th a n ex p ected from norm al m o r ta lity
and re c ru itm e n t was in d ic a te d by low r e c o v e r ie s o f marked f i s h th e o r e t­
i c a l l y a v a il a b le and by th e p a u c ity o f brook and rainbow t r o u t over two
y e a r s o ld . There was ev id en ce o f lim it e d movement.
The s ta n d in g cro p p e r
a c r e i n t h e combined f o u r stu d y s e c tio n s i n August 1951 was e stim a te d t o be
4 , 5#6 t r o u t o r 106 pounds. At t h i s tim e 80 and 85 p e r cen t r e s p e c tiv e ly
o f th e b ro o k and rainbow t r o u t numbers w ere in age group 0 , 18 and 13 p e r
c e n t w ere i n age group I and 2 p e r c e n t o f each were in age group II,.
Some in d iv id u a l brook and rainbow t r o u t a t t a i n e d l e g a l le n g th (7 in c h e s)
i n t h e i r second summer, how ever, th e m a jo r ity d id n o t re a c h t h i s s iz e u n t i l
t h e i r second f a l l o r th e fo llo w in g s p r in g . There were an e s tim a te d 5,86?
young o f t h e y e a r p e r m ile th e f i r s t f a l l a n d 5,468 p e r m ile th e second
summer, A c o l l e c t i o n o f brook t r o u t d u rin g t h e i r -spawning seaso n showed
t h a t some"young o f th e y e a r m ales w ere r i p e and t h a t a t l e a s t '72 p e r cen t
o f th e f i s h o v er 6 In c h e s long w ere m a le s.
5
INTRODUCTION
An i n v e s t ig a ti o n of t h e p o p u la tio n and eco lo g y o f t r o u t i n T rout C reek,
G a lla t in V a lle y , M ontana was made d u rin g t h e summers o f 1950 and 1951 and
t h e in te rv e n in g w in te r .
T h is stream i s one o f numerous sm all s p rin g -f e d
c re e k s which o c cu r i n th e a r e a .
Somewhat s i m i l a r s tu d ie s on t r o u t stre am p o p u la tio n s have been made by
S te fa n ic h (1952) on P r ic k le y P e a r C reek, M ontana; Schuck (1945) on C r y s ta l
C reek, New York; Needham, M o f f e tt, and S l a t e r (1945) on C onvict Creek,
C a l if o r n ia and S h e tte r and L eonard (1943) on Hunt C reek, M ich ig an .
•The w r i t e r w ishes t o acknowledge th e a s s is ta n c e o f D r. C .J.D . Brown
who d ir e c te d th e s tu d y and h e lp ed p re p a re t h e m a n u s c rip t.
In v a lu a b le a id
i n s e t t i n g up e l e c t r i c shocking equipment was g iv en by D r. A. R .- Jo rd an
and M r. H.G. H e l t e r l i n e $ i d e n t i f i c a t i o n s o f a q u a tic p la n ts w ere v e r i f i e d
by D r, W.E. B ooth; f r e e a c c e ss to th e p o rtio n o f th e c re ek s tu d ie d a s w e ll
a s o th e r c o o p e ra tio n was g iv e n by H e s s r s . Hugh S p a in , R adford M cGuire,
W ilb u r S p rin g and Ralph H e rd in a .
S e v e ra l s tu d e n ts a t Montana S ta te C o lleg e
a ls o a s s i s t e d , e s p e c ia ll y M arvin Boussu and W illiam C lo th ie r who h elp ed
c o l l e c t f i e l d d a ta and Ja c k B a ile y who a s s i s t e d in ag in g t h e f i s h .
The
M ontana F is h and Game D epartm ent allo w ed u se o f c e r t a i n equipm ent,
a s s i s t e d in p r e p a r a tio n o f th e s c a le m ounts, and p ro v id e d u se o f th e
s t a t e sh o c k in g ■crew on one o c c a s io n .
The M ontana S ta te C o lleg e A g ric u l­
t u r a l E xperim ent S ta tio n gave f i n a n c i a l a s s i s t a n c e ,
DESCRIPTION OF CREEK
T ro u t C reek i s 3^ m ile s n o r th e a s t o f B e lg ra d e , Montana a t an a l t i t u d e of
a p p ro x im a te ly 4 ,4 5 0 f e e t .
I t o r ig i n a te s in s p rin g s w h ic h .a re s c a tte r e d
TO
EAST
GALLATIN
RIVER
1/4 MILE
© STUDY SECTIONS
A
temperature
F ig , I .
stations
T rout C reek s tu d y a re a .
7
a lo n g i t s e n t i r e le n g th and m eanders th ro u g h a f e r t i l e a g r i c u l t u r a l a re a
f o r a d is ta n c e o f 4 m ile s to where i t e n te r s th e
E a s t G a l l a t i n E iv e r .
The d ra in a g e i s ab o u t seven sq u a re m ile s .
Study Area and S e c tio n s
O b se rv a tio n s w ere c o n fin e d t o th e upper 2g m ile s o f th e c re e k .
Four
r e p r e s e n t a t i v e 300- f o o t s e c tio n s were e s ta b lis h e d w ith o u t b ia s a s t o p o o ls ,
r i f f l e s and c o v e r.
S ta r t in g w ith th e u p perm ost, th e s e stu d y s e c tio n s were
d e s ig n a te d I , 2 , 3 and 4
(F ig . I ) .
P e r ti n e n t p h y s ic a l m easurem ents w ere made in each s e c tio n (T able I ) .
W idths and d e p th s w ere d eterm in ed when w a te r l e v e l s were in te rm e d ia te
betw een March low w a te r and Septem ber h ig h w a te r l e v e l s .
Average widths
were based on m easurem ents made ev ery 5 f e e t alo n g th e c re e k and in g e n e ra l
in c re a s e d p r o g r e s s iv e ly going dow nstream .
E i f f l e s w ith in - s e c tio n s had an
a v e ra g e m id -stream d ep th o f 6 .3 in c h e s , and p o o ls , a maximum d e p th o f 31
in c h e s .
The bottom i n r i f f l e a re a s was u s u a ll y composed o f sm a ll g r a v e l.
I n calm a r e a s sand and s i l t p r e v a ile d .
V e lo c ity and volume o f flow m easurem ents were made i n f a l l when h ig h
w a te r l e v e l s w ere b e in g a p p ro a ch e d .
V e l o c i t i e s were m easured w ith a
c u r r e n t m e te r h a l f way betw een th e s u rfa c e and bottom a t 12-15 e q u a l
i n t e r v a l s a c ro s s t h e c re e k .
Both v e l o c i t y and volume o f flo w in c re a s e d
from th e u p p er t o th e low er p a r t o f th e stu d y a r e a .
t i o n two f l a s h flo o d s w ere caused by. m e ltin g snow.
10, 1951 and th e o th e r on March 2 6 .
D uring t h e in v e s tig a ­
One on F e b ru a ry 9 and
The volume d u rin g th e s e flo o d s was
e s tim a te d ro u g h ly t o be seven tim e s g r e a te r th a n in t h e . f a l l .
o f t h i s n a tu r e w ere r e p o rte d t o be an a n n u al o c c u rre n c e .
Floods
They caused
8
T ab le I - Comparison o f p h y s ic a l c h a r a c t e r i s t i c s o f s tu d y s e c tio n s .
S e c tio n
L ength ( f e e t )
I
' 2
3
4
300
300
306
300
•Average w id th ( f e e t )
5.5
A rea ( a c re s )
0.038
1 0 .4
0.072
1 5 .5
0.109
1 5 .5
0.107
R iffle s p e r c en t o f s e c tio n ■
le n g th
22
50
33
40
Pools=^- ■
p e r c e n t o f s e c tio n
le n g th
13
44
49
39
12.21
14.72
Volume o f flow
(c u . f t . p e r s e c .)
2.36
9.07
1 .7 5
1.8 2
2 .0 0
(eS a /
(7.7)
(5.9)
(5.5)
A verage v e lo c i ty
( f t . p e r . sec.)-
Mkt l e a s t 12 in c h e s d eep .
■^A verage d e p th (in c h e s ) o f stream a t p la c e where v e lo c i ty was
m easured.■
9
w ashing o f th e stream banks and s c o u rin g o f t h e b o tto m .
The flow in
s e c tio n 4 was reduced a p p ro x im a te ly 20 p e r c e n t f o r 2 -3 weeks d u rin g th e
summer due t o an i r r i g a t i o n d iv e r s io n .
•In th e up p er t w o - f i f t h s o f th e .s t u d y a r e a , ( s e c tio n I in c lu d e d )
T ro u t C reek flow ed th ro u g h a sm all r a v in e i n which w illo w s ( S a lix s p .)
w ere f r e q u e n t.
S e c tio n I had l i t t l e shade from w illo w s b u t was narrow
enough so t h a t overhanging sedges (C a re x .r o s t r a t a and C. n e b ra s k e n s is )
and o th e r h e rb s covered a c o n s id e ra b le p o r tio n o f t h e c re e k s u rfa c e
( F ig . 2) .
The low er t h r e e - f i f t h s o f t h e stu d y a re a ( s e c tio n s 2 , 3 and
4 in c lu d e d ) was more open.
Much o f i t was b o rd e re d by low banks w ith
o c c a sio n a l-c lu m p s o f w illo w s and o th e r sh ru b s (F ig S i 3 and 4 ) .
2 and 3 had s e v e r a l w e ll shaded p o o ls .
S e c tio n s
S e c tio n 4 was co m p le tely open.
T here was l e s s u n d e rc u t bank i n s e c tio n 3 th a n in th e o th e r s .
■Aquatic p la n ts w ere p re s e n t in th e s tu d y a re a from e a r ly summer u n t i l
m id -w in te r.
4.
They w ere m ost dense in s e c tio n I and l e a s t d en se in s e c tio n
I n s e c tio n I (F ig . 2) w a te r c re s s (N a stu rtiu m o f f i c i n a l e ) p red o m in ated .
I t choked t h e edges along most o f th e s e c tio n and o c c u rre d a s m id -stream
p a tc h e s which i n p la c e s extended from bank t o bank.
T here w ere a ls o
o c c a s io n a l p a tc h e s o f a n a rro w -le a fe d pondweed (Fotam ogeton s p .) w ith
f o l i a g e th r e e t o s i x in c h e s lo n g , and a sm all amount o f brook g ra s s
( C a ta b ro sa a q u a t i c a ) .
I n th e low er t h r e e s e c tio n s w a te r c r e s s was common
alo n g th e edges w h ile s e p a r a te p a tc h e s o f w a te r speedw ell (V ero n ica
c o n n a ta ) . brook g r a s s and pondweed were found i n m id -stre a m .
In
s e c tio n 2 brook g r a s s and w a te r sp eed w ell predom inated and i n s e c tio n s
3 and 4 w a te r speedw ell was most abundant (F ig . 3 ) .
F ilam e n to u s
F ig , 3 .
F ig , 2 .
Upper p a r t o f studya re a ( s e c tio n I ) .
M iddle p a r t o f stu d y a re a ( s e c tio n 3 )•
11,
a lg a e were p r e v a le n t in th e c re ek i n summer and f a l l .
T em peratures
Y ear around te m p e ra tu re s were sec u re d a t th e u p p e r, m iddle and
low er p o r tio n o f th e stu d y a r e a (F ig . I ) .
These were ta k e n w ith T a y lo r
"S ix es" maximum-minimum therm om eters and were u s u a lly re c o rd e d th r e e o r
f o u r tim e s a month from August '1950 t o O ctober 1951«
The maximum and .
minimum re a d in g s f o r each s t a t i o n w ere p lo tte d on a graph o p p o s ite th e
d a te ta k e n (F ig . 5)•
The maximum w a te r te m p e ra tu re
i n th e h o t t e s t p a r t o f summer was 63
d e g re e s F . and th e minimum w in te r te m p e ra tu re was 32 d e g re e s F . .
T h is
minimum o c c u rre d o n ly f o r s h o rt p e r io d s , th e u s u a l December t o March
minimum b ein g about 38 d e g re e s F .
' The h ig h e s t and th e lo w e st tem pera­
t u r e s re c o rd e d were a t s t a t i o n 3 (F ig . I ) where s p rin g w a te r had th e
l e a s t m o d e ra tin g e f f e c t .
The maximum summer te m p e ra tu re s a t s t a t i o n I
w ere g r e a t e r th a n th o s e a t s t a t i o n 2. due to warmer w a te r from a sm all
t r i b u t a r y which e n te re d th e upperm ost p a r t o f th e stu d y a r e a .
Chem ical A nalyses
L im ited chem ical a n a ly s e s u sin g s ta n d a rd lim n o lo g ic a l m ethods were
made a t v a rio u s p o in ts a lo n g th e stu d y a re a on March I and J u ly 27, 1951°
Chem ical c o n d itio n s i n and below s e c tio n I were found t o be com parable on
b o th d a te s and c o n d itio n s a t a l l p o in ts were w e ll w ith in , th e ran g e
’
t o l e r a t e d b y t r o u t w ith th e p o s s ib le e x c e p tio n o f low d is s o lv e d oxygen
(24 p e r c e n t s a tu r a te d ) and h ig h f r e e COg (3 0 .0 p .p .m .) a t th e so u rce on
March I .
D isso lv e d oxygen and pH in c re a s e d going downstream w h ile
f r e e COg d e c re a s e d .
I n th e s tu d y s e c tio n s pH ranged from 7°5 t o 8,1.
12
1950
AUG. SEPTl OCT. |NOV. IDEC.
j a n . I F e b . Im a r J a p r j m a y Ij u n e Ij u l y Ta u g .1s e p t .Io c t .
MAX.
TEMPERATURE STATION I
H
50
MAX.
TEMPERATURE STATION 2
MAX.
TEMPERATURE STATION 3
F ig , 5»
Maximm-minimum te m p e ra tu re s i n T ro u t Creek
13
and f r e e OOg, from 3«0 t o 1 3 .0 p .p .m .
On b o th d a te s w ater i n s e c tio n
I was 77 p e r c en t s a tu r a te d w ith oxygen and in s e c tio n 4 ap p ro x im ately
100 p e r c e n t.
In g e n e r a l th e d is s o lv e d s a l t c o n te n t d e c re a se d going downstream .
On
March I t o t a l h a rd n e ss i n th e lo w er and u p p er stu d y s e c tio n s v a r ie d from
222 t o 232 p .p .m . ( a s CaCO^), and t o t a l a l k a l i n i t y (m ethyl o range) from
204' t o 223 p .p .m . Conductance ranged from 450 to 500 X ld ^ m h o p e r c e n t i ­
m e te r a t 25 d e g re es C.
S p e c ie s o f F is h P re s e n t
T ro u t w ere by f a r th e most numerous f i s h .
Rainbow t r o u t ( Salmo
g a i r d n e r i i ) and e a s te r n brook t r o u t ( S a lv e lin u s f o n t i n a l i s ) p red o m in ated .
Brown t r o u t ( Salmo t r u t t a ) w ere l e s s num erous.
H ybrid rainbow x c u tth r o a t
t r o u t w ere p ro b a b ly p r e s e n t, b u t no a tte m p t was made t o s e p a r a te them from
th e rainbow t r o u t .
F resh w ater s c u lp in s ( C o ttu s s p .) were p r e s e n t in con­
s id e r a b le num bers.
O ther f i s h c o lle c te d in c lu d e d s i x young m ountain
w h ite f is h ( Prosopium w illia m s o n i) «■th r e e la r g e su ck e rs ( Catostom us s p .)
and one longnose dace (R h in ic h th y s c a t a r a c t a e ) .
METHODS'
P o p u la tio n I n v e n to r ie s
F is h were c o lle c te d by th e d i r e c t e l e c t r i c a l c u rre n t m ethod (R ayner,
1 9 4 9 ).
Power was s u p p lie d by a sm all 2 50-w att D. C„ g e n e r a to r which was
p r o te c te d by a f u s e b u t o p e ra te d w ith o u t a r h e o s ta t
o r m e te rs .
Two
tr ia n g u la r - s h a p e d e le c tr o d e s formed by w rapping 16 gage copper w ire
h o r i z o n ta lly on a wooden fram e were employed ( S h a tt e r , 1 9 4 8 ).
A sm all
p a i r each w ith 14- in c h b a s e , 15-in c h h e ig h t and 5- in c h i n t e r v a l between
14
w ire w indings was used i n s e c tio n I s, and a la r g e p a i r each w ith 24-in c h
b a s e , 1 8 -in c h h e ig h t and 3 /8 -in c h w in d in g s was used dow nstream » The
e le c tr o d e s w ere mounted on wooden h a n d le s and were co nnected t o th e
g e n e r a to r by 100 f e e t o f ru b b e r in s u la te d c a b le „ The sh o ck e r could be
o p e ra te d w ith a minimum o f two men,
A u n it o f stre am up t o I 50 f e e t lo n g was b lo ck ed a t each end w ith
^ - in c h sq u are mesh s e in e s .
The e n e rg iz e d e le c tr o d e s were worked up- and
downstream w ith in th e a re a u n t i l no f i s h w ith a t o t a l le n g th g r e a t e r th a n
3 - 3 j in c h e s was ta k e n ,
F is h w ere r e tr ie v e d w ith a d ip n e t o f %=inch
sq u are mesh and h e ld in l i v e boxes covered w ith o rd in a ry window s c re e n ,
A 0 .5 p e r c e n t u re th a n e s o lu tio n was employed t o a n e s th e tiz e
c a p tu re d f i s h ( G erking, 1 9 4 9 ).
T o ta l le n g th s were ta k e n t o th e n e a r e s t
0 .1 in c h and w e ig h ts , t o t h e n e a r e s t 0 ,0 1 pound.
F is h w ere marked by
c u ttin g o f f one o r more f i n s f lu s h w ith th e body s u r f a c e .
A d iffe re n t
f i n was c lip p e d f o r each s e c tio n ( s e c tio n I , r i g h t p e c to r a l; 2 , l e f t
p e c t o r a l ; 3 , r i g h t p e lv ic and 4 , l e f t p e lv ic ) and a d i s t i n c t i v e combinaI
t i o n o f two c lip p e d f i n s was used f o r each lo c a tio n o u ts id e th e stu d y
s e c tio n s .
d e te rm in e d .
The amount o f e r r o r caused by re g e n e ra te d f i n s was n o t
I t was c o n sid e re d u n im p o rta n t, how ever, s in c e th e la p s e from
th e f i r s t t o th e f i n a l in v e n to ry was o n ly one y e a r and f i n s t h a t had
s t a r t e d t o r e g e n e ra te w ere a g ain c lip p e d from re c a p tu re d fis h , i n each
c o lle c tio n .
F is h s m a lle r th a n 3g in c h e s i n le n g th were so numerous in
some c o lle c tio n s t h a t t h e m a jo r ity were co u n ted b u t n o t m easu red .
A fte r
f i s h w ere p ro c e sse d th e y were h e ld i n a l i v e box u n t i l f u lly .r e c o v e r e d and
th e n r e le a s e d i n t o th e p o rtio n o f th e c re e k from which th e y w ere c a p tu re d .
15
Knovm c a s u a l t i e s w ere l i g h t .• Of 2 S440 f i s h h a n d led from May th ro u g h
Septem ber 1951 ( r e c a p tu r e s c o n sid e re d a s new f i s h ) o n ly 20 ( 0 .8 p e r c e n t)
were im m ediate c a s u a l t i e s .
l e s s th a n 2 in c h e s lo n g .
A ll were l e s s th a n 4 in c h e s lo n g and $ were
Of th e 2 0 , 9 were b e lie v e d t o have d ie d from '
h a n d lin g r a t h e r th a n from th e e f f e c t s o f e l e c t r i c i t y .
An a d d itio n a l 2 -3
p e r c e n t o f th e f i s h w ere caught by t h e i r g i l l s in th e w ire o f th e
p o s i t i v e e le c tr o d e .
F is h 4 -5 in c h e s in le n g th were m o stly a f f e c t e d .
U ndoubtedly some o f th e s e f i s h were i n ju r e d , though no m o r t a l i t y was ob­
s e rv e d .
A pproxim ately 2 p e r c e n t o f th e f i s h had body b u m s caused by
c o n ta c t w ith an e le c tr o d e .
The equipm ent was v e ry s a t i s f a c t o r y f o r making p o p u la tio n in v e n to r ie s
on T ro u t C reek where u n d e rc u t banks and a r e a s o f dense a q u a tic v e g e ta tio n
p r e v a ile d .
The f i s h were a t t r a c t e d t o th e p o s i t i v e e le c tr o d e where th e y
w ere e a s i l y c a p tu re d .
Few w ere stu n n e d .
About 10 f e e t 'was th e maximum d is ta n c e th e e le c tr o d e s co u ld be a p a r t
and have th e sh o ck er e f f e c t i v e .
I n one f i e l d t e s t a v o ltm e te r was used
and th e g e n e r a to r o u tp u t was found t o be 138 v o l t s w ith th e la r g e e le c ­
tr o d e s c o m p le te ly submerged a t t h i s i n t e r v a l .
In t h i s in s ta n c e th e .
t h e o r e t i c a l drop i n p o t e n t i a l betw een t h e e le c tr o d e s was 1 3 .8 v o lt p e r
fo o t.
Inasmuch a s f i s h would som etim es escape i f midway betw een e le c ­
tr o d e s h e ld 10 f e e t a p a r t b u t would be c a p tu re d i f n e a r t h e p o s itiv e
e le c tr o d e , i t i s f e l t t h a t 1 3 .8 v o l t s p e r f o o t ap p ro ach es th e minimum
v o lta g e drop t h a t would s a t i s f a c t o r i l y c o l l e c t f i s h u n d e r .th e c o n d itio n s
e x is t in g i n T ro u t C reek .
s i x t o e ig h t f e e t .
The i n t e r v a l betw een th e e lc t r o d e s was n o rm ally
Each bank had t o be worked s e p a r a te ly w ith both
■
16
e le c tr o d e s t o draw f i s h from th e u n d e rc u t, • E f f ic ie n c y was low i n p o o ls
more th a n
3 -4 f e e t d eep.
S e v e ra l e f f ic ie n c y t e s t s p a tte r n e d a f t e r th o s e o f H a s k e ll and .
Z l l l i o x (1941) were made d u rin g t h e summer o f 1951. B lo ck in g n e ts were
i n s t a l l e d and an i n i t i a l run made th ro u g h t h e en clo sed a re a w ith th e
s h o c k e r.
F is h ta k e n were marked w ith a d i s t i n c t i v e n o tc h on t h e a n a l o r
d o r s a l f i n and r e tu r n e d w ith in a m in u te o r two t o th e p la c e where c a p tu r e d .
The e s tim a te d le n g th s o f th e f i s h were re c o rd e d .
T h is p ro c e d u re was
fo llo w e d u n t i l from 10 t o 30 f i s h o f a l l s iz e s were marked and th e n
s t a r t i n g o v er a g a in th e p o p u la tio n was c o m p letely in v e n to r ie d u sin g th e
method d e s c rib e d p r e v io u s ly .
The p e rc e n ta g e o f re c a p tu re d marked f i s h
was used a s an in d i c a t i o n o f e f f i c i e n c y .
Two t e s t s w ere made u s in g th e la r g e e l e c t r o d e s .
The f i r s t upstream
from s e c tio n I i n a 49 f o o t le n g th o f stream a v e ra g in g 3 3 / 4 f e e t w ide.
T here was a t o t a l o f 16 f i s h in v o lv e d i n th e f i n a l c o l l e c t i o n .
A ll o f
t h e marked f i s h (5) from 4 .2 t o 6 .9 in c h e s lo n g were re c o v e re d and 4 o f 5
m arked f i s h l e s s th a n 3& in c h e s i n le n g th were re c o v e re d .
t e s t was i n a 120 fo o t p o r tio n o f s e c tio n 3 f i s h were in v o lv e d i n th e f i n a l c o l l e c t i o n .
The second
H eres, n e a r ly th r e e hundred
Of 14 marked f i s h from 4 .4
t o 9 .4 in c h e s Io n g 5, 13 w ere re c a p tu re d ; and o f 15 f i s h l e s s th a n 3g
in c h e s , 10 were re c o v e re d .
A- t h i r d t e s t was made u sin g th e sm a ll e le c tr o d e s i n a 150 fo o t
p o r tio n o f s e c tio n I .
In t h i s exp erim en t an hour i n t e r v a l was allow ed
betw een m arking th e f i s h and s t a r t i n g t h e f i n a l sh o ck in g .
f i s h in th e f i n a l c o l l e c t i o n .
T here were 84
A ll o f t h e marked f i s h (13) from 5 .0 t o
17
S o l in c h e s lo n g w ere re c o v e re d and o f 9 marked f i s h l e s s th a n 3 | in c h e s
i n le n g th , 8 were re c o v e re d .
Combining th e r e s u l t s o f th e s e t e s t s , i n t h e 3z in c h and l a r g e r s iz e
group 31 o f 32 marked f i s h were re c o v e re d g iv in g an e f f i c i e n c y o f 97 p e r
c e n t.
I n th e s m a lle r s iz e group 22 o f 29 marked f i s h were re c o v e re d
g iv in g an e f f ic ie n c y o f 76 p e r c e n t.
A lthough th e s e t e s t s w ere n o t as
e x te n s iv e a s would be d e s ir a b le and have o th e r shortcom ings a s p o in te d out
by Schuck (1948), th e y d id in d ic a te t h e e f f ic ie n c y o f p o p u la tio n in v e n to ry
m ethods u sed i n t h i s s tu d y .
The p e rc e n ta g e s d e riv e d w ere t h e b a s is f o r
c o r r e c tin g p o p u la tio n f ig u r e s u sed i n d e te rm in in g age co m p o sitio n , s u r­
v i v a l o f w ild t r o u t and sta n d in g p o p u la tio n s .
Ageing
A pproxim ately 1 ,6 0 0 s c a le sam ples w ere ta k e n a s a b a s is f o r d e te r ­
m ining th e age c o m p o sitio n o f t r o u t p o p u la tio n s .
s tu d ie d .
Of t h i s number 836 were
Of th e s e , 685 were from f i s h c o lle c te d i n t h e r e g u la r in v en ­
t o r i e s and 151 w ere from o th e r c o l l e c t i o n s .
A subsample o f 10 in d iv id u a ls
was u sed f o r each jg-inch s iz e group i n which th e r e w ere s u f f i c i e n t s c a le
sam p les.
A ll a v a il a b le s c a le sam ples were s tu d ie d f o r s iz e g roups in
w hich th e c la s s fre q u e n c y was below t h i s l e v e l (K etchen, 1950)„
T his was
done f o r each s p e c ie s i n each seaso n , th e tw o summers b e in g t r e a t e d
s e p a r a te ly .
Subsam pling was used m a in ly t o v e r i f y th e assum ption t h a t f i s h in a
w e ll re p re s e n te d model s iz e group in t h e le n g th -fre q u e n c y d i s t r i b u t i o n
w ere a l l o f t h e same a g e .
F is h i n p o o rly re p re s e n te d s iz e g ro u p s, where
o v e rla p was p o s s ib le , were aged by re a d in g s c a le s from t h e e x a c t f i s h
18
co n cern ed . However, s c a le sam ples were a v a il a b le f o r o n ly a b o u t 50 p e r
c e n t of. th e s e specim ens.
I n s e v e r a l in s ta n c e s re c a p tu re d f i s h t h a t co u ld
be d e f i n i t e l y i d e n t i f i e d w ere aged- by u s in g s c a le s ta k e n i n e a r l i e r
c o lle c tio n s .
About 15 whose ag es were q u e s tio n a b le w ere a ss ig n e d to age
g roups on th e b a s is o f s i z e .
A nnuli were d e term in e d w ith t h e a id o f a s c a le p r o je c tio n m achine.
S tu d ie s showed t h a t th e annulus form ed in t h e s p rin g and a l l f i s h were
c r e d ite d w ith h aving a new ann u lu s a f t e r Jan u a ry I even th o u g h i t was no t
com pleted ( H ile , 1 9 4 8 ).
There was re a so n a b ly c lo s e agreem ent betw een th e
ag es d e term in e d by th e s c a le method and th o s e shown by le n g th -fre q u e n c y
d is trib u tio n s .
A d e t a i l e d s tu d y o f an n u lu s fo rm a tio n w i l l a p p ea r in a ■
l a t e r p a p e r.
W eight A ssignm ent (Unweighed F ish )
Average w e ig h ts f o r each t r o u t s p e c ie s were d eterm in ed f o r 0 .1 in c h
le n g th i n t e r v a l s , th e av erag e f o r any one le n g th b e in g b ased on a l l f i s h
o f t h a t s iz e w eighed.
These a v erag e s were used t o a s s ig n w e ig h ts t o
in d iv id u a l rainbow and brown t r o u t n o t w eig h ted i n th e f i r s t shocking
o f s e c tio n s 2 and 4 and t o a few f i s h from o th e r in v e n to r ie s which escaped
b e fo re b e in g w eighed.
The le n g th -w e ig h t r e la tio n s h ip s f o r sm all b ro o k , rainbow and brown
t r o u t c ite d by G a rla n d er ( 1950) were u sed a s th e b a s is f o r t h e w eig h ts of
f i s h l e s s th a n 3 in c h e s i n le n g th s in c e w e ig h ts w ere n o t ta k e n on f i s h o f
th is s iz e .
W eights f o r each 0 .1 in c h l e n g t h - i n t e r v a l were o b ta in e d from
c u rv e s c o n s tr u c te d on t h e b a s is o f th e s e d a ta .
W eights o f l a r g e r f i s h
ta k e n from t h e c u rv es a g re ed re a so n a b ly w e ll w ith a c tu a l w e ig h ts o b ta in e d
19
in t h e f i e l d .
Where f i n g e r l i n g s l e s s th a n 3g in c h e s lo n g w ere counted r a th e r th a n
w eighed and m easured, w e ig h ts were a ss ig n e d i n p ro p o rtio n t o th e c a lc u ­
l a t e d w eight o f f i n g e r l i n g s a c t u a l l y m easured i n th e same c o l le c tio n o r in
c o l l e c t i o n s made a s h o rt tim e p r e v io u s ly .
HATCHERY FISH
A t o t a l o f 1,016 (4 -in c h ) brook t r o u t from th e U .S. F is h and W ild lif e
S e rv ic e H atch ery a t Bozeman, Montana was p la n te d in th e two m id d le stu d y
s e c tio n s on August 14, 1950.
h a n d lin g .
An e f f o r t was made t o m inim ize th e e f f e c t o f
The f i s h were marked by rem oval o f t h e a d ip o se f i n , t r e a t e d
w ith a b r in e s o lu tio n and th e n h e ld a t t h e h a tc h e ry f o r 10 days p r i o r t o
b e in g p l a n t e d .
There w ere no f a t a l i t i e s d u rin g t h i s p e r io d .
Marked f i s h
w ere tr a n s p o r te d t o t h e c re ek i n a e r a te d w a te r which was n e v er more th a n
10 F a h re n h e it d e g re e s above t h a t a t th e h a tc h e ry (4 9 °F . ) .
B efo re r e ­
m oval of th e f i s h from t h e h a tc h e ry t r u c k , t h e w a te r i n t h e ta n k was
•
tem pered t o w ith in 4 F a h re n h e it d e g re e s o f th e te m p e ra tu re o f th e c re ek
■water ( 5 1 9 F .) „ ' A pproxim ately o n e -h a lf o f th e 1 ,016 f i s h were d i s t r i b u t e d
th ro u g h o u t each o f s e c tio n s 2 and 3«
On Septem ber 1 4 , one month a f t e r p la n tin g , s e c tio n s 2 and 3 were
in v e n to r ie d by sh o ck in g .
2 and 24 i n s e c tio n 3 .
T h ir ty - e ig h t h a tc h e ry f i s h w ere found in s e c tio n
In t h e November in v e n to ry , 8 were found in
‘ s e c tio n 2. and 23 i n s e c tio n 3-
In th e s p rin g shocking p e rio d (May-June
1 9 5 1 ), none was found i n s e c tio n 2 and only 2 i n s e c tio n 3 .
D uring th e
f i n a l sh ocking p e rio d (A ugust 1951) no h a tc h e ry f i s h were found in e i t h e r
s e c tio n .
20
'
I n 1951 (February=jSeptem ber) a p p ro x im a te ly o n e - f i f t h o f t h e stu d y
a re a was shocked n o t in c lu d in g p o r tio n s r e p e a te d .
D uring t h i s p e rio d 10
h a tc h e ry f i s h w ere found and none o f th e s e was o v er 6 .8 in c h e s .
I f th e r e
w ere no r e c a p tu r e s ( f i s h c a p tu re d more th a n once) i n t h e a re a co v ered ,
t h e r e would be an e s tim a te d 50 h a tc h e ry f i s h , o r 5 p e r c e n t o f th e o r i g i n a l
p l a n t , p re s e n t i n th e
p la n tin g .
e n t i r e s tu d y a re a d u rin g th e c a le n d a r y e a r fo llo w in g
T h is r e s u l t i s n e a r ly e q u iv a le n t t o an e s tim a te d s u r v iv a l o f
6 .3 p e r c e n t (from one Septem ber t o th e n e x t) re p o rte d by Schuck (1948) a s
th e h ig h e s t f o r s e v e r a l p la n tin g s o f brown t r o u t f in g e r l i n g s in C ry s ta l
C reek, New Y ork.
H is f ig u r e was based on in v e n to r ie s made by th e e l e c t r i c
shock m ethod.
A t o t a l o f 135 h a tc h e ry f i s h in c lu d in g r e c a p tu r e s was cau g h t d u rin g
th e e n t i r e i n v e s t i g a t i o n on T ro u t C reek.
o u t th e e n t i r e s tu d y a r e a .
H a tch e ry f i s h w ere found th ro u g h ­
T here was no d is e e r n a b le p a tte r n o f movement
away from th e o r ig i n a l p la n tin g s i t e s .
WILD THODT POPULATIONS
Except f o r th e marked h a tc h e ry f i s h p la n te d d u rin g th e s tu d y , the,
f i s h i n T ro u t Creek w ere c o n sid e re d t o be w ild f i s h .
T here were no
re c o rd s o f re c e n t p la n tin g s by th e l o c a l h a tc h e ry and th e m a jo r ity o f f i s h
c a p tu re d were l e s s th a n th r e e y e a r s o ld .
D ates o f I n v e n to r ie s
The f i s h p o p u la tio n s i n t h e fo u r stu d y s e c tio n s were in v e n to r ie d a t
f i v e main shocking p e rio d s a s fo llo w s;
J u ly 2 5-August 2 4 , 1950; Septem ber
14, 1950 ( s e c tio n s 2 and 3 o n ly ) ; O ctober 28-November 19, 1950; May 17June 3 , 1951 and A ugust 4 -1 2 , 1951°
O th er p o rtio n s o f th e s tu d y a re a were
shocked a t i r r e g u l a r i n t e r v a l s th ro u g h o u t th e p e rio d o f in v e s t i g a t i o n .
S p e c ie s D is tr ib u tio n
The d i f f e r e n t s p e c ie s o f t r o u t showed a d e f i n i t e p a tte r n o f d i s t r i ­
b u tio n i n th e stu d y a r e a .
Brook t r o u t predom inated a t th e u p p e r end, .I n
s e c tio n I t h e i r numbers com prised 83-96 p e r c en t o f a l l t r o u t in th e
r e g u la r in v e n to r ie s (T able I I ) ,
Rainbow t r o u t predom inated in th e low er
th r e e s e c tio n s where th e y c o n s ti tu te d 70-92 p e r c e n t (T a b le s I I I , IV, and
V ),
The f i r s t in v e n to r ie s o f s e c tio n s 2 and 4 show a lo w er p e rc e n ta g e o f
rainbow t r o u t b e ca u se i n s u f f i c i e n t e f f o r t was made t o c a p tu re young o f th e
y ear.
The p ro g r e s s iv e change from p re d o m in a te ly brook t r o u t i n th e u p p er
p a r t o f th e s tu d y a re a to ,p re d o m in a te ly rainbow t r o u t in t h e low er p a r t i s
d em o n strated by -comparing t h e y e a r lin g c la s s e s i n each s e c tio n d u rin g th e
main i n v e n t o r i e s ,
(T ab le s I I , I I I , IV and V ),
As a g e n e r a l r u l e th e
number o f brook t r o u t y e a r lin g s p r o g r e s s iv e ly d ecreased going downstream
w h ile th e number o f ra in b o w t r o u t y e a r lin g s in c r e a s e d .
F o r example i n th e
August 1951 in v e n to ry th e number o f brook t r o u t y e a r lin g s was 3 6 , 2 0 , 9
and I i n s e c tio n s I t o 4 r e s p e c tiv e ly w h ile i n th e same s e c tio n s th e
number of rainbow t r o u t y e a r lin g s was 4 , 37, 45 and 56, .
Brown t r o u t were found th ro u g h o u t th e low er th r e e —f i f t h s o f th e
s tu d y a re a b u t w ere nowhere th e predom inant s p e c ie s .
Only, two were found,
one on each o f two o c c a s io n s , in th e u p p e r tw o - f i f t h s o f th e stu d y a r e a .
They were n e v e r found i n s e c tio n I ,
There w ere n o tic e a b ly few er s e u lp in s i n s e c tio n I th a n i n th e o th e r s .
T h is a r e a was judged t o be i n f e r i o r h a b i t a t f o r th e s p e c ie s .
22
. P o p u la tio n Changes Between I n v e n to r ie s
The numbers and w e ig h ts com prisin g th e age groups o f each t r o u t
s p e c ie s a t each shocking a re p re s e n te d t o show p o p u la tio n changes between
s h o c k in g .p e rio d s (T ab le s I I j I I I s IV and V )„ These d a ta in d i c a t e a
n u m e ric a l in c r e a s e i n young o f t h e y e a r f i s h , e s p e c ia ll y rainbow t r o u t ,
from s p rin g (tim e o f h a tc h ) th ro u g h l a t e f a l l .
T h is i s p ro b a b ly n o t th e
c a s e s in c e th e r e sh o u ld be a maximum a t h a tc h in g fo llo w e d by a p ro g re s s iv e
d e c re a s e th ro u g h th e y e a r .
The a p p a re n t in c r e a s e i s most l i k e l y due to
c o l l e c t i n g m ethods and a ls o t o i n s u f f i c i e n t e f f o r t s b e in g made in th e
e a r ly c o l l e c t i o n s t o c a p tu re young o f th e y e a r f i s h .
To d e term in e t h e p a t t e r n o f n u m e ric a l changes f o r rainbow t r o u t o ld e r
th a n young o f th e y e a r , a l l in v e n to r ie s were t r e a t e d a s i f th e y were from
th e same y e a r th u s g iv in g a sequence from s p rin g th ro u g h summer and f a l l .
On t h i s b a s is rainbow t r o u t o ld e r th a n age group 0 showed maximum numbers
i n t h e f i r s t in v e n to ry o f th e y e a r and th e n a more o r l e s s p ro g re s s iv e
d e c lin e t o th e l a s t in v e n to ry o f t h e y e a r .
T h is i s b e s t shown by s e c tio n
3 where t h e r e were 133 i n June 1951s 51 i n August 1951 (53 i n August 1 9 5 0 ),
'3 1 i n Septem ber 1950 and 21 i n November 1950.
Rainbow t r o u t o f t h i s age
c a te g o ry in s e c tio n s 2 and 4 showed a s im ila r d e c re a se i n num bers.
'T his
p a t t e r n was ex p ected s in c e a t th e f i r s t o f each y e a r th e y e a r lin g c la s s i s
r e c r u i t e d from th e n u m e ric a lly s tro n g young o f th e y e a r c l a s s o f th e
p re v io u s y e a r .
S e c tio n I was an e x c e p tio n t o th e above p a tte r n presum ably
b ecau se brook t r o u t was t h e predom inant s p e c ie s .
No in fo rm a tio n was
se c u re d d u rin g th e rainbow t r o u t spawning season t o show w h eth er o r no t
th e y in c re a s e d a t t h a t tim e .
Table I I - Section I .
Trout numbers and weights (pounds) in each inventory.
D ate o f shocking
S p e c ie s
and
age group
Aug.’ 24. 1950
No
M t.
Brook (h a tc h e ry )
Brook (w ild )
0
I
II
I I I & o ld e r
T o ta l '
Rainbow
.0 '
I
II
I I I & o ld e r
T o ta l
Grand t o t a l
L b s ./a c r e
Nov. 18, 1950
No.
Wt.
2
51
45
I
097
I
10
I
0
12
109
0.63
3.57
0.19
0
4.39
May'20
1951
No.
Wt.
0 .06
5 3 (2 2 )1 /1 ,3 3
77(25) 9.67
2
0 .7 4
0
Ocx134(47) 11.80
-
I
-
5
48(14)
20(13)
0, ".
72(27)
0.02
I
0.05
0
1.7 0
101
0.77
2.83
2.50
0
4.2 2
0
13 (I)
0.18
0
0
0.45
13" (4 )
0 .5 8
0.22
0 .2 4
0 .
o;69
5.08
134
0
’ 4 (I )
0
I , .
0
0
0.29
5 (I)
0.30
4.51
.119 „
143(19)
3.95
104
0.25
0 .
0
161(53) 12.81,
337 ; ■
o„ • _ 0
0
0 138(18) 3 .6 5
0 .0 7
0
I (I)
0
1 .0 1
36(18)
0.18
0.12
9 (I)
I (I)
27 (6 )
Aug. 12 1951
• No.
Wt.
10 (2)
82(29)
g u re s in p a re n th e s e s - numbers o f re c o v e re d f i s h marked p re v io u s ly in t h i s s e c tio n .
Table I I I - S ection 2 .
Trout numbers and weights.(pounds) in each inventory. .
D ate o f shocking
S p e c ie s
and
age group
,
J u ly 25, 1 9 5 0 " S e p t. 14, 1950
No.
Wt.
No.
W t.
Mov. 19. 1950
No.
W t.
May 3 0 , 1 9 5 1 ^
"No.
Mt.
-12 ( 5)
12 (4)
Aug. 4 . 1951
No.
W t.
Brook (h a tc h e ry )
Brook (w ild )
II
I I I & over
T o ta l
32 (7 )
96(10)
Rainbow
209 (6)
II
I I I & over
T o ta l
23(10)
3 (2)
I (I)
236(19)
13 (8 )
Brown
II
I I I & over
T o ta l
G r a n d .to ta l
8 (3 )
5 .39
3 5 3 (3 7 ) -1 3 .9 9
, -1 9 4
Numbers and w e ig h ts have been c o rre c te d i n p ro p o rtio n t o th e "red u ctio n i n s e c tio n le n g th .
& our young o f th e y e a r t r o u t n o t c l a s s i f i e d to " s p e c ie s a re " o m itte d . These were marked and re tu rn e d
t o w a te r. Jfc ig u re s in p a re n th e s e s = numbers o f re c o v ere d f i s h marked p re v io u s ly in t h i s s e c tio n .
Table I V
Section 3„
Trout numbers and weights (pounds)__in. each inventory-.
D ate o f shocking
S p e c ies
and
age group
Aug. 9, 1950
W t.
No.
Brook (h atch ery ).
Brook (w ild )
,0'
I
II
I I I & o ld e r
T o ta l.
12
17
0
0
&9
Rainbow
0
I
II
I I I & o ld e r
T o ta l
129
49
3
I
182
Brown
0
I
II
I I I & o ld e r
T o ta l , .
2
3
0
0
5.
Grand t o t a l
L b s ./a c r e
0 .1 3
2 .0 1
0
0
2 .1 4
-•
.
216
'
0.47
2 .9 2
*
S e p t. 14, 1950
No,
-Wt.
Nov, 4 , 1950
No.
Wt,
0.95
2
■0 .1 3
(8 )
0 .1 8
2 .2 2
0
0
3 .3 5
0
10
I
I
14
0- '
0 .5 7
0 .1 8
0.4 3
1 .3 1
1.0 2
258($1)
2 .0 1 ■ 17(12)
1.8 6
2 (2)
0
2
. 4.89 279(65)
2 .0 5
1 .5 1
0 .7 8
1 .2 6
5.60
24
0 .7 2
23
1 1 :( 2 ) ^
0 .2 1
1 .0 8
0
0
"9
15
0
0
47
9 (6)
o .
.0
44 (8 )
■
158(17)
26(17)
Aug, I l . 1951
No.
- W t,
0
0.
’0
2.01
(2)
(6 )
.' .
0.90
5,(3)
0 .5 1
4 .8 0
0 .
189(37)
- 0.01
2
2 (2)
0
0
4 (2)
0 .4 2
0
0
0 .4 5
0.05'
1 .2 4
I - . 0 .5 6
4
8.43
12 (4) 10.28
7^47 • 237(47)
69
7 .3 5
67 .
338(77) 19.23
- 176
0 .5 2
0
0
0 .5 3
June 3 , 1 9 5 1 ^
. No.
W t.
0.03
3 (2)
4 (2)
0
114(13)
18.(5)
I
133(18)
0
I
0
0
I
148(18)
0
3 .3 6
2 .7 2
0 .6 0
6.68
o •
0 .0 6
0.
o
0 .0 6
" 8 ,0 5
74
53 (4)
9 (2)
2 (I)
.0
64 (7)
332 ( I )
45(33)
6X3)
0
383(37)
12
I
0
0
13
(I)
(I)
.
(2)
1460(46)
-tw e lv e young o f th e y e a r t r o u t n o t c l a s s i f i e d t o s p e c ie s a re o m itte d . These w ere marked and
e tu m e d t o w a te r.
£ F ig u re s i n p a re n th e s e s = numbers o f re c o v e re d f i s h marked p re v io u s ly i n t h i s s e c tio n ,
0
0.57
.0.83
0 .6 9
o ■
2 .0 9
1 .0 4
2 .9 1
1.59
0
5.54
0 .1 1
0 .14
0
0
0 .25
7.88
72
Table -V--- Section 4
Trout numbers, and weights (pounds) In each inventory.
D ate o f shocking
S p e c ie s
age g ro u p Brook
(h a tc h e ry )
Brook (w ild )
II
I I I & o ld e r
T o ta l
0
...
.
Eainbow
376 (3)
22 (1 5 )
Il
I I I & o ld e r
T o ta l
400(48)
'0 .
95(13)
3 .( 1 ) '
■0
98(14)
2 .( 1 )
0
0 .5 5
0 -
212(22)
5.94
238(22)
6.81
Brown
II
I I I & o ld e r
T o ta l
23 (5)
Grand t o t a l .
106(17)
. 58.
.73.. .
% h i s s e c tio n was 504 f e e t long on t h i s d a te . B e f o r e t h e n e x t shocking i t was reduced to
300 f e e t . Numbers and w e ig h ts have been c o rre c te d in p ro p o rtio n t o th e re d u c tio n in
s e c tio n le n g t h ,
2 /^ g u re s i n p a re n th e s e s
numbers o f re c o v ere d f i s h marked p re v io u s ly i n t h i s s e c tio n .
On
27
A lthough i n t h e r e g u la r p a tte r n th e number o f f i s h i n each c la s s
d e c re a se d th ro u g h th e y e a r , th e lo s s ' i n t o t a l w eight due t o re d u c tio n in
numbers was o f f s e t t o a la r g e e x te n t by th e g a in in w eight o f in d iv id u a l
f i s h « T h is was w e ll d em onstrated by th e August 1951 shocking o f s e c tio n
2 (T able I I I ) ,
Here h a l f th e age g roups o ld e r th a n young o f th e y e a r
showed a d e c re a se in number b u t an in c r e a s e i n w eight when compared to
th o s e i n t h e May 1951 sh o ck in g .
W hile th e same p a t t e r n o f n u m e ric al d e c re a se th ro u g h th e y e a r prob­
a b ly e x i s t e d .f o r th e o v e ra ll, p o p u la tio n o f brook and brown t r o u t , i t was
n o t confirm ed by d a ta on T ro u t C reek.
The October-November in v e n to ry was
ta k e n d u rin g t h e spawning season o f th e s e s p e c ie s and showed a decided
n u m e ric a l in c r e a s e o f y e a r lin g s and o ld e r f i s h .
Only s e c tio n I showed a
pronounced in c r e a s e in th e number o f brook t r o u t .
in c re a s e d from 45 i n August 1950 to 77 i n November.
Here th e y e a r lin g group
The numbers o f spawn­
in g brook t r o u t d id n o t m arkedly in c r e a s e i n th e o th e r s e c tio n s which had
p re d o m in a te ly rainbow t r o u t .
The in c r e a s e i n brown t r o u t o ld e r th a n t h e 0 age group i n th e
October^November in v e n t o r y .i s b e s t d e m o n strated by s e c tio n s 3 and 4°
S e c tio n
3 showed an in c r e a s e from 2 i n th e Septem ber 1950 shocking t o
9 i n November and s e c tio n 4 showed an in c r e a s e from 3 i n August 1950 t o
10 in l a t e O cto b er.
Both s e c tio n s showed a re d u c tio n o f brown t r o u t o ld e r
th a n young o f t h e y e a r i n l a t e r in v e n to r ie s .
■In th e October=November in v e n to ry s e c tio n s I , 3 and 4 each had a
t o t a l t r o u t w eig h t double t h a t f o r th e same s e c tio n in any o th e r in v e n to ry .
F o r exam ple, i n s e c tio n I th e t o t a l w eig h t i n t h i s in v e n to ry was 1 2 .8 1
28.
p o unds„
The n e x t h ig h e s t was th e August 1950 in v e n to ry w ith a t o t a l
w e ig h t o f 5»08 pounds (T able I I ) „ These in c r e a s e s were due la r g e ly t o th e .
i n f l u x o f brook o r brown t r o u t and t o a l e s s e r e x te n t th e in c re a s e d w eight
o f young o f th e y e a r ,
.Needham, M o ffe tt and S l a t e r (1945) s tu d ie d f l u c t u a t i o n s o f a brown
t r o u t p o p u la tio n o v er s e v e r a l y e a rs and found th e r e was u s u a lly a g a in in
t o t a l pounds p e r m ile over t h e summer p e rio d b ecau se o f th e growth o f in™
d iv id u a l young o f th e y e a r f i s h .
S e c tio n 2 d id n o t show an in c r e a s e in t o t a l t r o u t w eig h t from th e
Septem ber t o t h e October-November in v e n to r y .
The p re se n c e o f two la r g e
brown t r o u t a cc o u n te d f o r th e in c r e a s e i n w eig h t o f t h i s s p e c ie s .
There
was a .re d u c tio n in b o th brook and. rainbow t r o u t w e ig h ts,
■The two summer in v e n to r ie s (Ju ly -A u g u st 1950 and August 1951) were
compared.
S e c tio n I showed a 22 p e r cen t re d u c tio n i n t o t a l t r o u t w eight
from 1950 t o 1951 due m ainly t o a d e c re a s e o f 28 p e r c e n t i n th e number o f
y e a r lin g s and o ld e r f i s h .
i n w e ig h t,
T h is was th e o n ly s e c tio n t h a t showed a d e c re a se
S e c tio n 2 showed a n u m erical in c r e a s e in most age groupisj th e
t o t a l w eight more th a n d o u b led , - P a r t o f t h i s in c r e a s e may be a t t r i b u t e d
t o an improvement i n c o l l e c t i n g methods a f t e r th e J u ly 1950 shocking o f
t h i s s e c tio n .
In s e c tio n s 3 and 4 th e t o t a l t r o u t w eight d id n o t change
m arkedly from summer to summer.
Comparison o f numbers o f each t r o u t
s p e c ie s from summer t o summer (young o f t h e y e a r ex clu d ed ) showed a 28
p e r c en t d e c re a se i n brook t r o u t and an 11 p e r c en t in c r e a s e i n rainbow
t r o u t f o r th e combined f o u r s e c tio n s .
•
29
Movement and P o p u la tio n S t a b i l i t y
About_3S200. w ild t r o u t w ere marked d u rin g th e in v e s t ig a ti o n and most
o f th e s e ( n e a r ly 2 ,4 0 0 ) b e fo re t h e M ay-June 1951. in v e n to ry .
A lto g e th e r
ab o u t o n e -q u a rte r o f th e stu d y a re a was covered by shocking o p e r a tio n s .
•A t o t a l o f . 57 f i s h (28 b ro o k , 27 rainbow and 2 brown t r o u t ) , in c lu d in g
r e p e a t s , were re c a p tu r e d more th a n 500 f e e t from t h e stream s e c tio n in
which th e y w ere o r i g i n a l l y ta k e n .
I and I m ile , and 5 over a m ile .
Of th e s e , 26 had tr a v e le d betw een
The g r e a t e s t d is ta n c e co v ered was t h a t
o f .a rainbow which tr a v e l e d about I 3 /4 m ile s i n a downstream d i r e c t i o n .
The o b s e rv a tio n s in d ic a te d ab o u t e q u al u p - and downstream movement, how­
e v e r , t h e sam pling te c h n iq u e was n o t d e sig n e d t o q u a n t i t i v e l y m easure th e
d i r e c t i o n o f movement.
L im ited movement was in d ic a te d by o b s e rv a tio n s o f f i s h c a p tu re d
im m ed iately above o r below t h e s e c tio n i n which th e y had been .m ark ed .
In
one c o l l e c t i o n 12 f i s h marked, i n s e c tio n I w ere found o u ts id e th e s e c tio n
b u t w ith in 220 f e e t o f i t s u p p er boundary.
On p r a c t i c a l l y e v ery o ccasio n
when c o l l e c t i o n s were made a d ja c e n t t o a stu d y s e c tio n , marked f i s h from ■
th e n e arb y s tu d y s e c tio n were fo u n d .
-The e x te n t t o which t r o u t rem ained i n one a re a was in d ic a te d by a
com parison o f t h e number marked i n any one s e c tio n t o th e number re ­
c a p tu re d i n th e same s e c tio n .
each in v e n to ry (T able V I ) .
T his was ta b u la te d , f o r each s e c tio n in
A lthough th e number a v a ila b le t h e o r e t i c a l l y
in c r e a s e d a s a d d itio n a l f i s h were marked in each in v e n to ry , th e number o f
r e c a p tu r e s d id n o t in c r e a s e p r o p o r tio n a l ly .
F o r exam ple, i n th e Septem ber
14, .1950 in v e n to ry o f s e c tio n 3 th e r e w ere 47 r e c a p tu r e s o f 183 tr o u t
f)
30
- T ab le VI - W ild t r o u t marked and re c o v e re d i n each s e c tio n .
S e c tio n and
d a te , shocked
Number
marked
Number
p re v io u s ly marked
Number
re c a p tu re d
S e c tio n I
Aug. 2 4, 1950
Nov. 18, 1950
May 2 0 , ■ 1951
Aug. 12, 1951 '
107
101
47
11
107
208
255
. 53
29
19
( 3 2 .4 )
(3 6 .7 )
(4 6 .3 )
S e c tio n 2
J u ly 2 5 , 1950
S e p t. 14, 1950
Nov. 19, 1950
May 3 0 , 1951
Aug0 4 , 1951
1062/
256
.249
64
155
106
362
611
675
36
33
37
(4 2 .4 )
(4 6 .7 )
(3 4 .0 )
(4 7 .3 )
S e c tio n 3
Aug. 9, 1950
S e p t. 14, 1950
Nov. 4 , 1950
Ju ne 3 , 1951
Aug. 11, 1951'
183
144.
225
134
160
183
327
. 552
686
47
77
18
46
(6 6 .7 )
(4 8 .9 )
(1 2 .3 )
(6 3 .5 )
191
471
557
27
17
22
(5 2 .5 )
(16. 0 )
(3 6 .7 )
S e c tio n 4
Aug. 1 ,1 9 5 0
O ct. 2 8, 1950
May I ? , 1951
Aug. 5, 1951
-4lumbers
I9M
86
131
98
i n p a re n th e s e s a re th e p e rc e n ta g e s o f th e p o p u la tio n made up
by re c a p tu re d f i s h , e x c lu d in g young o f th e y e a r ,
-=Low due t o i n f l u x of spawning brook t r o u t ,
^ S e c t i o n s ‘2 " and 4 "were 482 and 504 f e e t "lo n g r e s p e c tiv e ly i n th e
f i r s t " i n v e n t o r y when th e s e f i s h w ere m arked„ Each was reduced to
300 f e e t- b e fo re .th e n e x t sh o ck in g ,
M.n e s tim a te . About 125 young o f t h e y e a r n o t marked; t h i s p o s s ib ly
reduced th e p e rc e n ta g e o f th e p o p u la tio n made up by r e c a p tu r e s in
l a t e r sh o c k in g s.
31
marked on A ugust 9»
The number o f r e c a p tu r e s i n t h i s s e c tio n f lu c tu a te d
in th e November and June in v e n to r ie s , b u t in th e August 1951 in v e n to ry
t h e r e were s t i l l o n ly 46 r e c a p tu r e s o f 686 f i s h m arked.
S e c tio n s 2 and 4
showed s im ila r p a t t e r n s .
An i n d ic a tio n o f p o p u la tio n s t a b i l i t y was a ls o o b ta in e d by comparing
th e p e rc e n ta g e o f th e p o p u la tio n ( e x c lu d in g young o f th e y e a r) which was
re c a p tu re d f i s h from in v e n to ry t o in v e n to ry .
s e c tio n (T ab le V I ) .
T h is was done f o r each
The p e rc e n ta g e was e s p e c ia ll y c o n s ta n t from in v e n to ry
t o in v e n to ry f o r s e c tio n 2 .
As a whole th e s e f ig u r e s ' seem t o in d ic a te
t h a t th e p e rc e n ta g e s o f t h e p o p u la tio n made up by r e c a p tu r e s would be
f a i r l y c o n s is te n t were th e in v e n to r ie s a t e q u a l i n t e r v a l s .
The sp rin g
in v e n to ry (M ay-June), f o r a l l s e c tio n s e x ce p t s e c tio n I , showed a re d u c tio n
i n th e a c tu a l number o f re c a p tu r e s a s w e ll a s a r e d u c tio n i n th e p e rc e n t­
age o f th e p o p u la tio n ( y e a r lin g s and o ld e r) made up by r e c a p tu r e s .
T h is
was ex p ected becau se o f th e 6-7 month i n t e r v a l which had e la p s e d sin c e th e
Gctober-November in v e n to ry .
The e f f e c t o f t h e two f la s h f lo o d s th a t
o c c u rre d d u rin g t h i s p e rio d i s n o t known.
S e c tio n I showed a p ro g re s s iv e
d e c re a s e i n th e number o f r e c a p tu r e s from t h e November 1950 t o th e August
1951 in v e n to r y .
There was a l s o a p ro g r e s s iv e re d u c tio n o f t r o u t numbers in
t h i s s e c tio n .
The g r e a t e s t p e rc e n ta g e re c o v e ry o f m arked f i s h o c c u rre d in s e c tio n I
w here 107 t r o u t w ere marked on August 2 k s 1950, 53 (50 p e r c e n t) were
re c o v e re d 86 days l a t e r on November 18.
D is c u s s io n o f ,P o p u la tio n S t a b i l i t y
There a p p a r e n tly was a p o p u la tio n tu rn o v e r g r e a te r th a n t h a t which
32
co u ld be expected from norm al m o r t a lit y and r e c r u itm e n t,
As p o in te d o u t,
a d d itio n a l f i s h were marked a t each in v e n to ry y e t marked f i s h d id no t
accum ulate from in v e n to ry t o in v e n to ry ,
A lso s a t l e a s t 45 p e r c en t o f th e
y e a r lin g s and o ld e r f i s h w ere "new" f i s h i n a l l in v e n to r ie s where marked
f i s h were a v a i l a b l e ,
S h e tte r and H azzard (1939) found p o p u la tio n s o f '
rainbow , brook and brown t r o u t t o be r e l a t i v e l y u n s ta b le in s h o r t s e c tio n s
(a b o u t 100 f e e t ) o f c e r t a i n M ichigan s tre a m s.
They computed th e n e t p e r­
c e n ta g e l o s s . o f marked t r o u t t o be 44 -9 4 p e r cent from month t o month.
T h is was b ased on th e number o f marked f i s h r e tu r n e d t o th e w a te r a f t e r
any o n e . in v e n to ry compared t o th e number re c a p tu re d i n th e n e x t.
F o r th e
T ro u t Greek s tu d y s e c tio n s th e n e t p e rc e n ta g e lo s s o f marked t r o u t
(com puted by th e same method) was 81-94 p e r c e n t d u rin g th e 6 -7 month
i n t e r v a l from October-November 1950 t o M ay-June 1951 and 61-79 p e r c en t
d u rin g th e 2 -3 month i n t e r v a l from M ay-June t o August 1951.
■The changes i n p o p u la tio n from in v e n to ry t o in v e n to ry co u ld only have
been caused by movement or.som e m o r t a lit y f a c to r y such a s p r e d a tio n ,
a n g lin g , e t c .
W hile th e r e was evid en ce o f movement over s h o r t d is ta n c e s ,
th e stu d y d id n o t d e m o n strate e m ig ra tio n from t h i s sm all c re e k t o th e
r i v e r below .
Shocking and h a n d lin g may have in flu e n c e d movement.
M o r ta lity from sh o ck in g i s n o t c o n sid e re d to be an im p o rta n t f a c t o r ,
■Smith and E lso n (1950) t e s t e d th e l e t h a l e f f e c t s o f c o lle c tin g t r o u t and
salmon w ith a-D. C. shocking a p p a r a tu s .
They concluded t h a t delayed
m o r t a l i t y was n o t s i g n i f i c a n t and t h a t f i s h re c o v e rin g im m ed iately co u ld
be assumed t o be u n in ju r e d .
d e le te rio u s .
The w r i t e r does n o t b e lie v e u re th a n e was
G erking (1949) d e s c rib e d i t a s n o n to x ic when u sed in p ro p e r
33
c o n c e n tr a tio n s . . F in c lip p in g , how ever, may be th e cause o f m o r t a lit y ,
e s p e c ia ll y when th e p e c to r a l f i n s a re removed (W a le s ,.1947 I
1951)•
S h a tte r ,
P e c to r a l f i n s were c lip p e d from f i s h i n th e u p p er two .study sec­
t i o n s o f T ro u t C reek.
The e f f e c t on t h e p o p u la tio n was n o t d eterm in ed .
The p a u c ity o f rainbow and brook t r o u t o ld e r th a n ag e-g ro u p I I
in d ic a te d a r a p id p o p u la tio n tu r n o v e r .
Inasmuch as o ld e r f i s h were s c a rc e
a t th e tim e o f th e f i r s t a s w e ll a s l a t e r in v e n to r ie s t h i s c o n d itio n co u ld
n o t be a t t r i b u t e d t o shocking o r m ark in g .
The o b s e rv a tio n s made do n o t
d is c l o s e th e cause o f t h i s u nexpected l o s s o f o ld e r f i s h .
F is h in g p re s s u re
was c o n sid e re d t o be o f m inor im p o rtan ce s in c e th e r e were few fish erm en on
t h e s tu d y a re a a f t e r th e f i r s t 3=4 weeks o f th e f is h in g s e a so n .
King­
f i s h e r s , g r e a t b lu e h e ro n s and mink w ere p r e s e n t and fo u r f i s h w ith wounds
presumed t o be beak marks were found.
P r e d a tio n by th e s e an im als was no t
b e lie v e d t o have had a s e r io u s e f f e c t on th e p o p u la tio n .
S ta n d in g P o p u la tio n s
The sta n d in g p o p u la tio n o f t r o u t i n th e s tu d y a r e a was computed on
th e b a s is o f th e August 1951 in v e n to ry (T ab le V Il)..
The numbers and
•
w e ig h ts were c o r r e c te d f o r t h e .e f f ic ie n c y of th e shocking method as ex­
p la in e d u n d er age c o m p o sitio n .
C o rre c te d f ig u r e s showed 1,495 t r o u t t o be
'
i n th e f o u r s tu d y s e c tio n s .
,
These had a t o t a l w eight o f 34=7 p ounds.
i s e q u iv a le n t t o 4 ,5 8 6 t r o u t or 106 pounds p e r a c r e .
T h is
Rainbow t r o u t
com prised 72 p e r c e n t by number and 52 p e r c e n t by w e ig h t; brook t r o u t , 25
p e r c e n t by number and 29 p e r c e n t by w eight 5 and brown t r o u t 3 p e r c e n t
by number, and 19 p e r c en t by w e ig h t.
As a lr e a d y p o in te d o u t, i n t h e ' October-November in v e n to ry th e t o t a l .
34 ’
w e ig h ts i n s e c tio n s I j, 3 arid 4 were a t l e a s t double th o s e i n o th e r in v en ­
to rie s ,
At t h i s tim e s e c tio n I was computed t o have a sta n d in g crop o f
o v er 300 pounds p e r a c r e - by f a r th e l a r g e s t s ta n d in g crop f o r any
s e c tio n .
The u p p er two s tu d y s e c tio n s each c a r r ie d more pounds p e r a c re
d u rin g 1951 th a n e i t h e r o f th e low er tw o s e c tio n s (T a b le s X I, I I I , IV and
V ),
In th e c o r r e c te d A ugust 1951 in v e n to ry f i s h o f l e g a l s iz e (7 in c h e s
and over) made up a p p ro x im a te ly 2 , 3 and 14 p e r c en t by number and 35, 2?
and 93 p e r c e n t by w eight o f t h e rainbow , bro o k and Tarowri t r q u t re s p e c ­
tiv e ly ,
L egal rainbow t r o u t in t h i s in v e n to ry av erag ed 8,3 in c h e s and
0 ,2 5 poundsi brook t r o u t , 8 ,3 in c h e s and 0 ,2 2 pounds; and brown t r o u t ,
1 1 ,2 in c h e s and
0 ,8 5 pounds.
There w ere 197 le g a l t r o u t p e r m ile o f th e
s tu d y a re a b a se d on c o rre c te d f i g u r e s .
The e ig h t l a r g e s t f i s h c a p tu re d d u rin g th e stu d y p e rio d w ere brown
t r o u t ra n g in g from 1 8 ,4 t o 2 5 .5 in c h e s .
The l a r g e s t rainbow t r o u t was
1 7 .9 in c h e s and t h e l a r g e s t brook t r o u t 12 .3 in c h e s ,
■The s ta n d in g cro p o f 106 pounds p e r a c re f o r th e stu d y a re a as a
w hole i n August 1951 i s com parable t o t h e sta n d in g crop o f 94.40 pounds of
b ro o k t r o u t p e r a c re (p lu s 9 .6 8 pounds o f m u ddlers) found by S h e tte r and
Leonard (1943) in a s e c tio n o f Hunt C reek , M ich ig an .
In t h e i r stu d y le g a l
s iz e f i s h (7 in c h e s and over) com prised 2 ,3 p e r cent by number and 19 .4
p e r c e n t by w eight o f th e brook t r o u t p o p u la tio n a s compared t o 3 p e r cen t
by number and 27 p e r c e n t by w eight i n t h e p re s e n t stu d y on T ro u t C reek.
•Age C om position
The August 1951 in v e n to ry o f a l l f o u r s e c tio n s was used a s th e b a s is
35
f o r d e te rm in in g th e age com position o f t h e w ild- t r o u t p o p u la tio n in th e
s tu d y a r e a „
The t o t a l number i n each age group from a l l fo u r s e c tio n s was
com piled f o r each s p e c ie s o f t r o u t „
These numbers were c o r r e c te d on th e
b a s i s o f e f f ic ie n c y t e s t s d e s c rib e d above in which 76 p e r c e n t o f th e f i s h
l e s s t h a n -Sg in c h e s i n le n g th and 97 p e r c e n t o f th o se. 3& in c h e s and o v e r
w ere re c o v e re d (T ab le V I I ) 0 W eights were c o rre c te d by d e te rm in in g th e
a v erag e w eight i n each age group and m u ltip ly in g i t by th e c o rre c te d
number o f f i s h .
The age c o m p o sitio n s o f th e rainbow and brook t r o u t p o p u la tio n s were
co m parable.
I n each th e young o f th e y e a r group predom inated n u m e ric a lly .
I t com prised 85 p e r c e n t o f th e rainbow and 80 p e r c e n t o f t h e brook
tro u t.
T h is age group was a c o n s id e ra b ly l e s s im p o rta n t component o f
p o p u la tio n w e ig h ts making up o n ly 15 and 26 p e r c e n t.
Y e a rlin g s (one
an n u lu s) com prised 57 and 58 p e r cen t r e s p e c tiv e ly o f th e rainbow and
brook t r o u t w eig h ts b u t o n ly 13 and 18 p e r c en t o f th e num bers.
Tw o-year-
o ld s (two a n n u li) made up 28 and 16 p e r c e n t o f rainbow and brook t r o u t
w e ig h ts and 2 p e r c e n t o f t h e numbers o f each s p e c ie s .
T here were no
o ld e r rainbow o r brook t r o u t ta k e n i n t h i s in v e n to ry .
The age s t r u c t u r e of th e brown t r o u t p o p u la tio n d i f f e r e d m arkedly
from t h a t o f t h e rainbow and brook t r o u t i n August 1951 s in c e t h e y e a r­
l i n g group was o f m inor im p o rtan ce (one f i s h ) w h ile f i s h two y e a r s old
o r o ld e r com prised 90 p e r c e n t o f th e w e ig h t.
The age s t r u c t u r e o f t h i s
s p e c ie s had changed c o n s id e ra b ly s in c e th e p re v io u s summer.
I n th e J u ly -
August 1950 in v e n to ry t h e r e were nijhe y e a r lin g brown t r o u t and none
o ld e r .
36
T able V II - C o rre c te d numbers and w e ig h ts o f t r o u t i n August 1951
in v e n to r y . D ata from a l l s e c tio n s combined.
?F
CO
W t.
( lb s .)
2 .6 0
908
2 .7 8
44.
0 .4 7
6 9 ^ 5.90
146
10.37
I
0 .1 4
18
5.06
5
1 .9 1
0
I
3 .9 0
51
6.4 2
No.
0
297
II
I I I & o ld e r
T o ta ls
W t. .
( lb s .)
No.
Age group
I
Brown
tro u t
Rainbow
tro u t
Brook
tro u t
6
1 .6 1
o
0
0
10.12
372
1,072
No.
18.21
.
-A6ne hatchery trout (0.05 pounds) included.
T ab le V III - C o rre c te d numbers o f w ild brook and rainbow t r o u t in
in v e n to r ie s used f o r r a t e o f s u r v iv a l c o m p u ta tio n s.1 /
Brook t r o u t
Rainbow t r o u t
Age group ■
0
I
II
101
i
0
1133/ 2
0
In v e n to ry
Ju ly -A u g . 1950
O c t.-N ov. 1950
M ay-June
1951
-2 /
81
72
32
III &
o ld e r
I
Age group
0
I
III &
o ld e r
7
■2
66 , 5
2
- 2 / 139
1,243
II
- 2 / 285
36
2
■ fig u res-sh o w n a r e t o t a l s f o r a l l stu d y s e c tio n s .
^Sample in a d e q u a te '
..............................
% ig h due t o i n f l u x o f spaw ning f i s h .
■
37
S u rv iv a l
E stim a te d r a t e s o f s u r v iv a l f o r w ild e a s te r n b ro o k and rainbow t r o u t
were computed from c o r r e c te d in v e n to ry f i g u r e s f o r t h e v a r io u s age-groups
(T a b le s V II and V I I I ) „
S u rv iv a l was computed by two m ethods: ( l ) by com­
p a rin g numbers i n age groups o f one in v e n to ry w ith th o s e i n an e a r l i e r
in v e n to r y ;(2) by com paring age groups i n a s in g le in v e n to ry w ith each
o th e r .
The young o f t h e y e a r sample in th e Ju ly -A u g u st 1950 in v e n to ry was
n o t c o n sid e re d r e p r e s e n ta tiv e f o r e i t h e r s p e c ie s and was n o t u sed to
/
e s tim a te s u r v iv a l -o f t h i s age group,
-
I
The e s tim a te d s u r v iv a l o f young o f th e y e a r rainbow t r o u t over th e 12
month p e rio d (August, t o A ugust) was 16 p e r c e n t when b ased on th e r a t i o o f
age group I to age group 0 i n t h e August 1951 in v e n to r y .
T h is.w as compar­
a b le to th e e s tim a te o f 12 p e r cent, s u r v iv a l f o r n in e months. (November t o
A ugust) b ased on th e r a t i o o f age group I i n t h e August 1951 in v e n to ry t o
age group 0 i n th e October-November 1950 in v e n to r y .
E stim a te d s u rv iv a l
from age group I to a g e 'g ro u p I I from August t o August was about 12 .5
p e r c e n t by e i t h e r m ethod.
-The s u r v iv a l o f young o f th e y e a r brook t r o u t f o r n in e months
(November t o A ugust) was e stim a te d to be 84 p e r cen t based on th e r a t i o o f
age group I i n t h e August 1951 in v e n to ry t o age group 0 i n t h e .G ctoberNovember in v e n to r y .
The s u r v iv a l f o r 12 months i f based on th e age compo­
s i t i o n o f th e August 1951 in v e n to ry would be o n ly 23 p e r c e n t.
T h is
method o f com putation i s n o t c o n sid e re d v a l i d i n t h i s i n s ta n c e .
It
depends on un iform re c ru itm e n t from y e a r t o y e a r and t h i s a p p a re n tly was
n o t th e c a s e .
There were 81 young o f th e y e a r in th e October-November .
38
1950 in v e n to ry and 297 i n th e ,A u g u st 1951 in v e n to r y .
The w r i t e r does no t
b e lie v e t h e .th r e e months d if f e r e n c e in seaso n o f c a p tu re a c c o u n ts f o r t h i s
v a r i a t i o n i n numbers „ S u rv iv a l o f y e a r lin g bro o k t r o u t over, a 12 month
p e rio d was e s tim a te d t o be 6 p e r c en t b ased on th e r a t i o o f age group I I
in t h e August 1951 in v e n to ry t o age group I i n th e Ju ly -A u g u st 1950 i n ­
v e n to ry .
T here w ere no brook o r rainbow t r o u t i n age group I I I in th e
August 1951 in v e n to ry ; t h e r e f o r e , th e r e was no a p p aren t s u r v iv a l f o r age
group I I and o ld e r from August 1950 to A u g u st'1951°
S h e l t e r and Leonard (1943) e s tim a te d th e y e a r t o y e a r s u r v iv a l o f a
brook t r o u t p o p u la tio n i n a s e c tio n o f Hunt G reek, M ichigan t o be 65 .9 p e r
Cent from age group 0 t o I .
T h is i s somewhat com parable t o th e e stim a te
o f Bk p e r c e n t f o r n in e months in t h e T ro u t Creek s tu d y .
T h e ir e s tim a te s
o f 64.3 p e r c en t s u r v iv a l from age group I t o I I and 1 3 .7 p e r c en t from
age group I I t o I I I a re much h ig h e r th a n e s tim a te s f o r bro o k t r o u t s tu d ie d .
from T ro u t G reek.
Schuck (1948) a n aly z e d S h e lte r and H azzard 6s (1939) d a ta
o f a summer’ s s e in in g s o f t h r e e M ichigan stre am s and e s tim a te d th e s u r v iv a l
from f i n g e r l i n g s t o y e a r lin g s t o be 14 p e r c e n t f o r rainbow t r o u t (v e ry
s im ila r t o e s tim a te f o r T ro u t Greek) and $2 p e r c e n t f o r brook t r o u t
(lo w e r th a n e s tim a te f o r T ro u t C re e k ).
Growth
A ll grow th e s tim a te s were b ased on th e August 1951 in v e n to r y .
was chosen b e ca u se:
T h is
( l ) th e tim e la p s e from b e g in n in g t o end was compar­
a t i v e l y s h o r t (8 d a y s ); and (2 ) most c o l l e c t i o n s by o th e r w orkers have
been made d u rin g summer, so t h a t a c o l l e c t i o n i n t h i s sea so n made th e
d a ta more com parable.
Growth o f rainbow and brook t r o u t w a s-e stim a te d
39
T ab le IX - T o ta l le n g th s o f brook and rainbow t r o u t in each age
group- (A ugust 1951 in v e n to r y ) „
S p e c ie s and
age group
Number
of fis h
T o ta l le n g th s a t c a p tu re (in c h e s )
Average
Range
Brook
0
.230
2 .9 0
2 .0 = 4 -1
I
66
6 .0 8
4 . 7 - 9.-li /
II
' 6
8 .8 0
8 .0 - 9 .7
2.12
1 .0 - 3 .3
Rainbow
0
326
I
142
5-50
3 .7 - 8 . 3 ^
II
17
8 .#
6 .5 ~ 1 2 .6
S t a n d a r d d e v ia tio n s
S t a n d a r d d e v ia tio n s
'
0 ,8
0 o9
40
from th e av erag e t o t a l le n g th s o f each age group a t tim e o f c a p tu r e ,
A ll
m easured f i s h from a l l s e c tio n s were in c lu d e d (T able IX )„
Young o f th e y e a r rainbow t r o u t .had an av erag e le n g th o f 2 ,1 in c h e s
compared w ith 2 .9 in c h e s f o r brook t r o u t .
The d if f e r e n c e was p ro b a b ly due
to th e e a r l i e r h a tc h in g d a te o f brook t r o u t .
Some in d iv id u a ls o f each
s p e c ie s a t t a i n e d l e g a l le n g th (7 in c h e s ) i n t h e i r second summer, however,
th e m a jo r ity d id n o t re a c h t h i s size, u n t i l t h e i r second f a l l o r th e
I
fo llo w in g s p r in g .
T h is grow th r a t e i s somewhat b e t t e r th a n t h a t re p o rte d
b y P u rk e tt (1951) f o r th e rainbow and brook t r o u t i n th e B rid g e r Creek
system which i s a ls o t r i b u t a r y t o th e E a s t G a lla t in E i v e r .
Here both
rainbow and brook t r o u t averaged 6 .6 in c h e s a t tim e o f second annulus
fo rm a tio n .
P h e n ic ie (1950) found t h a t i n 12 o f th e 17 M ontana stream s
sam pled rainbow t r o u t d id n o t re a ch l e g a l le n g th , on th e average^ u n t i l
th e t h i r d y e a r o f l i f e .
C om parisons o f sam ples from th e v a rio u s s e c tio n s o f T ro u t Creek
in d ic a te d a sm all b u t p ro g r e s s iv e in c r e a s e i n r a t e o f grow th from th e
u p p er t o th e low er end o f th e stu d y a r e a .
However, th e sam ples were n o t
l a r g e .enough t o s e rv e a s c o n c lu s iv e e v id e n c e .
N a tu ra l R ep ro d u ctio n
Ju d g in g from th e la r g e number o f f i n g e r l i n g t r o u t , c o n d itio n s must
have been v e ry fa v o ra b le f o r n a t u r a l re p ro d u c tio n ift T ro u t C reek, C o rre c te d
in v e n to ry f ig u r e s in d i c a t e t h e r e were 1 ,3 4 0 young o f t h e y e a r t r o u t in th e
f o u r stu d y s e c tio n s (1 ,2 0 6 f e e t ) i n Oetober-November 1950 and 1,249 i n
August 1951.
The s p e c ie s com positio n d i f f e r e d in th e two y e a r s .
October-November in v e n to ry
In th e
about 93 p e r c e n t were rainbow t r o u t , 6 p e r
41
c e n t brook t r o u t and I p e r c e n t brown t r o u t ,
I n th e August 1951 in v e n to ry
a b o u t 73 p e r c en t w ere rainbow t r o u t , 24 p e r c e n t brook t r o u t and 3 p e r
c e n t brown t r o u t .
Based on th e s e c o r r e c te d in v e n to ry f ig u r e s th e r e were
59867 young o f t h e y e a r p e r m ile i n l a t e f a l l (October-W ovember) 1950 and
5*468 p e r m ile i n August 1951°
Needham, M o ffe tt and S l a t e r (1945) i n a
s tu d y o f th e w ild brown t r o u t p o p u la tio n i n
C onvict C reek, C a lif o r n ia
found t h a t n a t u r a l re p ro d u c tio n c o n trib u te d an av erag e o f o v er 2 ,7 5 0 f i s h
p e r m ile each y e a r .
T h is was i n a p o r tio n o f stream- w ith an average
w id th n o t much d i f f e r e n t from t h a t o f t h e T ro u t Creek s tu d y s e c tio n s .
T h e ir maximum f ig u r e was 4 ,9 0 5 p e r m ile which i s n e a r ly e q u iv a le n t t o th e
number found i n T ro u t C reek.
Brook t r o u t c o lle c te d on November 1 8 , 1950.i n s e c tio n I w ere used f o r
d e te rm in in g age and se x r a t i o .
T his c o l le c tio n was s e le c te d s in c e brook
t r o u t predom inated and w ere spawning a t t h a t tim e .
f i r s t y e a r o f l i f e w ere r i p e .
Some m ales i n t h e i r
E ig h t o f 55 young o f th e y e a r (in c lu d in g
two h a tc h e ry f is h ) ta k e n i n t h i s c o lle c tio n exuded m ilt when l i g h t
p re s s u re was a p p lie d t o t h e b e l l y .
le n g th .
These ranged from 4 °1 t o 4»8 in c h e s in
The y o u n g est fem ales found t o be r i p e w e r e - y e a r lin g s .
The
s m a lle s t o f th e s e was 6 .3 in c h e s .
Sex was d eterm in ed o n ly f o r brook t r o u t which were r i p e .
c lu d ed th e m a jo r ity o f th o s e over s ix in c h e s i n le n g th .
p re d o m in a te ly m a le s .
T h is in ­
These -wefe
A t o t a l o f 67 in c lu d e d 48 (72 p e r c e n t) m ales, 14
(21 p e r c e n t) fem ales and 5 (7 p e r c e n t) whose, sex was n o t d e term in e d .
The u n b alan ced sex r a t i o
co u ld be caused by m ales m atu rin g and moving
i n t o spawning a r e a s a t a younger age t h a n fem ales;,
However, t h i s
42
a p p a r e n tly i s n o t th e e ase s in c e re c a p tu re d f i s h , i . e . , th o s e marked p re ­
v io u s ly i n t h i s s e c tio n , showed t h e same predom inance o f m a le s.
Of I?
re c a p tu r e d f i s h lo n g e r th a n 6 in c h e s , 12 (70 p e r c e n t) were m a le s, 2
(12 p e r ceni^ w ere fe m a les and 3 (18 p e r c e n t) co u ld n o t be d e s ig n a te d as
t o se x .
R ipe brown t r o u t i n th e O ctober-N ovember in v e n to ry in d ic a te d t h a t
t h e i r spawning sea so n c o in c id e d a t ' l e a s t in p a r t w ith t h a t o f th e brook
tro u t.
The y o ungest brown t r o u t found t o be r i p e were y e a r l i n g s .
The
sam ple o f t h i s s p e c ie s was to o sm all t o g iv e r e l i a b l e in fo rm a tio n on sex
ra tio
43
SUMMARY
I4
A stu d y o f a ra in b o w , brook and brown t r o u t p o p u la tio n i n T ro u t G reek,
a sm all s p r in g - f e d ■c re ek i n th e G a lla tin Va l l e y , M ontana, was made
d u rin g two summers and th e in te r v e n in g w in te r .
The p o p u la tio n s i n two
stu d y s e c tio n s w ere in v e n to r ie d f o u r tim e s and in two o th e r stu d y
s e c tio n s f i v e tim e s d u rin g th e i n v e s t i g a t i o n .
c lip p e d and r e le a s e d ,
th e p o p u la tio n .
F is h ta k e n w ere f i n -
,
A. d i r e c t c u r r e n t sh o ck er was u sed f o r sam pling
The minimum dfrbp i n p o t e n t i a l t h a t would s a t i s f a c t o r ­
i l y c o l l e c t fis h .w a s e s tim a te d t o be 1 3 ,8 v o l t s p e r f o o t ,
2,
A t o t a l o f 1,016 marked 4 -in c h bro o k t r o u t were p la n te d i n August 1950
An e s tim a te d $ p e r c en t rem ained i n t h e 2g m ile stu d y a re a d u rin g th e
fo llo w in g c a le n d a r y e a r ,
3,
The d i f f e r e n t s p e c ie s o f t r o u t showed a d e f i n i t e p a tte r n o f d i s t r i ­
b u tio n i n t h e s tu d y a r e a .
Brook t r o u t com prised 83-96 p e r c en t o f th e
- t r o u t numbers i n th e upperm ost stu d y s e c tio n where th e stre a m was
n arro w .
Rainbow t r o u t com prised 70-92 p e r cen t i n th e lo w er th r e e
stu d y s e c tio n s ,
4,
Rainbow t r o u t o ld e r th a n age group 0 were a t t h e i r maximum number i n
th e f i r s t in v e n to ry o f th e c a le n d a r y e a r (May-June) due t o re c ru itm e n t
o f young f i s h and th e n g ra d u a lly d e c lin e d i n number t o th e l a s t i n ­
v e n to ry o f th e y e a r (O ctober-N ovem ber),
The l o s s i n t o t a l t r o u t
w eight due to th e re d u c tio n i n number th ro u g h th e y e a r was la r g e ly
o f f s e t by th e g a in i n w eig h t o f in d iv id u a l f i s h .
Brook t r o u t (u pper
stu d y s e c tio n ) and brown t r o u t o ld e r th a n young o f t h e y e a r in c re a s e d
■ m arkedly d u rin g t h e i r spawning s e a s o n s.
44
5 o A p o p u la tio n tu r n o v e r g r e a t e r th a n ex p ected fro m norm al m o r t a lit y and
re c ru itm e n t was in d ic a te d by low r e c o v e r ie s o f marked f i s h t h e o r e t i ­
c a l l y a v a il a b le and by th e p a u c ity o f b ro o k and rainbow t r o u t over two
y e a r s o ld .
6.
There was evidence o f lim ite d movement. '
The e s tim a te d s ta n d in g cro p p e r a c re i n August 1951 i n t h e f o u r stu d y
s e c tio n s combined was 4* 586 t r o u t o r 106 pounds (197 l e g a l s iz e d t r o u t
per m ile )o
Of th e brook and rainbow t r o u t num bers, 80 and 85 p e r c en t
r e s p e c tiv e ly were i n age group Oj 18 and 13 p e r c e n t w ere i n age gro u p
I and 2 p e r c e n t o f each were i n age group I I ,
There were no o ld e r
specim ens o f e i t h e r s p e c ie s .
7.
The e s tim a te d s u r v iv a l (A ugust t o A ugust) o f rainbow t r o u t between age
group 0 and I was 16 p e r c e n t o r l e s s ; betw een age group I and I I ,
about 1 2 .5 p e r c e n t.
The e stim a te d ’ s u r v iv a l o f brook t r o u t between '
age group 0 and I from f a l l t o summer (n in e months) was 84 p e r c e n t;
betw een age group I and I I from August t o A ugust, 6 p e r c e n t.
8.
The av erag e t o t a l le n g th s (in c h e s ) i n August 1951 f o r th e v a rio u s age
groups o f rainbow and brook t r o u t r e s p e c tiv e ly were:
age group 0 , 2 .1
and 2 .9 ; age group I , 5«5 and 6 .1 ; and age group II., 8 .6 and 8 ,8 .
9.
On th e b a s i s o f th e f o u r stu d y s e c tio n s t h e r e were an e stim a te d 5,867
young o f th e y e a r p e r m ile o f th e s tu d y . s p c tio n in l a t e f a l l (O cto b erNovember) 1950 and 5*468 p e r m ile in August 1951.
A c o lle c tio n of
brook t r o u t made d u rin g t h e i r spawning seaso n showed:
( l ) some young
o f th e y e a r m ales were r i p e , (2) th e youngest r ip e fem ales were y e a r lin g s , (3) a t l e a s t 72 p e r c e n t o f th e f i s h o v er 6 in c h e s lo n g
w ere m a le s.
45
LITERATURE CITED
C a rla n d e rj, Kenneth D0
1950« Handbook o f fre s h w a te r f i s h e r y b io lo g y 0
Wm0 C0 Brown Co0j Dubuquej Iow a0 281 pp„
G erk in g j S helby D0 1949» U rethane ( e th y l carbam ate) i n some f is h e r y
p ro c e d u re s . P ro g . F is h - C u ltOJ l l ( l ) : 73-74»
H a s k e llj David C0 and R obert G0 Z i l i i o x 0 1941« F u r th e r developm ents of
th e e l e c t r i c a l method o f c o l le c tin g f i s h , T ra n s 0 Am. F is h , S ocoj 70
(1940): 404-409.
H ile j R alph,
1948. S ta n d a rd iz a tio n o f methods o f e x p re ss in g le n g th s and
w e ig h ts o f f i s h , T ra n s , Am, F is h , S o coj 7 5 (1945): 157-164«
K etch en j K0 S ,
1950, S t r a t i f i e d subsam pling f o r d e te rm in in g age
d i s t r i b u t i o n s . T ra n s , Am. F is h , S o c oj 7 9 (1949): 205-212.
Needhamj P a u l Roj James W. M o f f e ttj and D a n ie l W, S l a t e r ,
1945«
F lu c tu a tio n s i n w ild brown t r o u t p o p u la tio n s i n C onvict C reek,
C a l if o r n ia , J o u r 0 W ild l, M gtoj 9 (1 ): 9 -2 5 .
P h e n ic ie j C h a rle s K0 1950, Rainbow t r o u t g ro w th . B ear F a c ts and F ish
T a le s (M ont, F is h and Game
P u r k e t t , C h a rle s Aoj J r .
D ep t0) , M ar, 1950: 5 -6 .
1951. Growth r a t e o f t r o u t i n r e l a t i o n to
e le v a tio n and te m p e ra tu re , T ra n s, Am, F is h , Socoj 80(1950): 251-259«
R aynerj H.' J .
1949. D ir e c t c u rre n t a s a id t o th e f is h e r y w o rk er.
P ro g , F is h - C u lt, 11(3)': 169-170,
Schuckj Howard A.
1945. S u r v iv a l, p o p u la tio n d e n s ity , grow th and
mdvement o f th e w ild brown t r o u t i n C r y s ta l C reek, T r a n s , Am, F is h ,
S o c ,, 73(1943): 209-230,
46
—=
„
1948. S u rv iv a l o f h a tc h e ry t r o u t in stre am s and p o s s ib le methods
o f im proving th e q u a l i t y o f h a tc h e ry t r o u t « P ro g . F is h - C u lt„s
1 0 (1 ): 3 -1 4 .
S h e l t e r , David S .
1948. The e l e c t r i c ” shocker" and i t s u se in M ichigan
s tre a m s . P ro g . F is h . C u l t , 1 0 ( l ) : 4 3 -4 7 .
-------- .
1951. The e f f e c t o f f i n rem oval on f in g e r li n g la k e t r o u t
( C ris tiv o m e r namaycush) - T ra n s . Am. F is h . S o e ., 80(1950): 260-277«
'
--------
and A lb e rt 5 . H azzard .
1939. S p e c ie s com p o sitio n by age group's
and s t a b i l i t y o f f i s h p o p u la tio n s in- s e c tio n s o f th r e e M ichigan t r o u t
stre am s d u rin g th e summer o f 1937. T ra n s . Am. F is h . S o c ., 68(1938):
281 - 302 .
-------- and J u s t i n ¥ . L eonard.
1943. A p o p u la tio n s tu d y o f a lim ite d a re a
i n a M ichigan t r o u t stre am , Septem ber 1940. T ra n s . Am, F ish S o c .,
72(1942): 3 5 -5 1 .
S m ith, G. F . M. and P . F i E ls o n .
1950. A - d ir e c t- c u r r e n t e l e c t r i c a l
f i s h i n g a p p a r a tu s . C anadian F is h C u lt. ( 9 ) ° 3 4 -4 6 .
S te f a n ic h , Frank A.
1952. The p o p u la tio n and movement o f f i s h in
P r ic k le y P e a r G reek, M ontana. T ra n s . Am. F is h . -Sod. 81(1951):
W ales, J . H.
1947. Growth r a t e and f i n re g e n r a tio n i n t r o u t . P ro g .
■ Fish-C ult. 9 (2 ): 86-89.