The biology and population characteristics of the Arctic grayling in Lake Agnes, Montana
by Larry George Peterman
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 Larry George Peterman (1972)
Abstract:
The biology and population dynamics of the grayling in Lake Agnes were studied during the summers
of 1970 and 1971. In 1971, the ice cleared from the lake on May 28, and the peak of spawning
migrations occurred from June 15 to 24. A diurnal movement of spawning grayling into and out of the
inlet stream was closely correlated to daily fluctuations in stream temperatures. The sex ratio of 9,364
fish captured in the spawning run was 2.5 females for every male. Intensive territorial behavior
between spawning males was noted along the shoreline and at the mouth of the inlet and probably
deterred many males from entering the stream. Male grayling generally averaged larger in size and
grew faster than females. Grayling from Lake Agnes showed the slowest average growth rate of any
reported in Montana. A few grayling matured at age II, however, most matured at age III. Only one
adult grayling out of 559 was aged as over 6 years old. The number of eggs per female increased with
the size of the fish and averaged 356 eggs per ounce of fish. The adult population was estimated using
the Peterson method and the Schnabel method. The total estimate based on the Peterson method was
24,214 with a standing crop of 72.8 kg/ha.
Total population estimates were in close agreement between both methods, however, male and female
estimates based on the Schnabel method were 47.5 percent higher and 18.1 percent lower, respectively,
than comparable Peterson estimates. Reasons for past fluctuations in numbers and size of fish are
discussed. S ta te m e n t o f P e r m i s s i o n t o Copy •
I n .p r e s e n tin g t h i s t h e s i s i n p a r t i a l f u l f i l l m e n t o f th e r e q u ir e ­
m e n ts f o r an a d v a n c e d d e g r e e a t M ontana S t a t e U n i v e r s i t y / I a g r e e t h a t
t£ie L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r i n s p e c t i o n .
I fu rth e r
a g r e e t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y in g o f t h i s t h e s i s f o r s c h o l a r l y ,
p u r p o s e s may b e g r a n t e d b y my m a jo r p r o f e s s o r , o r , i n h i s a b s e n c e , by
th e D ire c to r o f L ib r a r ie s .
I t i s u n d e r s t o o d t h a t any c o p y in g o r
p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a in s h a l l n o t b e a llo w e d
w i t h o u t my w r i t t e n p e r m i s s i o n .
S ig n a tu re
D a te
tl A A W
WhaSL&lt
n i x
THE BIOLOGY M D POPULATION -CHARACTERISTICS OF THE ARCTIC
GRAYLING IN LAKE AGNES , MONTMA
by
LARRY GEORGE PETERMM
A t h e s i s s u b m i t te d t o t h e G r a d u a te F a c u l t y i n p a r t i a l
f u l f u l l m e n t o f t h e r e q u i r e m e n ts f o r t h e d e g re e
of
MASTER OF SCIENCE
in
F i s h a n d W i l d l i f e M anagem ent
H e a d , M a jo r D e p a rtm e n t
MONTMA STATE UNIVERSITY
B ozem an, M ontana
J u n e , 1972
iii
ACKNOWLEDGMENT
The a u t h o r w is h e s t o e x te n d h i s a p p r e c i a t i o n t o t h o s e who
a s s i s t e d him d u r in g t h e c o u r s e o f t h e i n v e s t i g a t i o n :
D r. R ic h a r d J .
Graham d i r e c t e d t h e s t u d y , a i d e d i n t h e f i e l d w o r k a n d a s s i s t e d i n
t h e p r e p a r a t i o n p i t h e jn ^ n u s g r ip t; D r s . R o b e r t L, Eng and D on■C .
Quimby c r i t i c a l l y
r e a d t h e m a n u s c r ip t ; D r. W illia m R. G o u ld , f e l l o w
g r a d u a t e s t u d e n t s , an d J a c k P e te rm a n a id e d i n t h e f i e l d w o rk ; t h e
M ontana P i s h an d Game D e p a rtm e n t lo a n e d e q u ip m e n t an d v e h i c l e s ; and
h i s w i f e , ' B a r b a r a , g a v e h e r e n c o u ra g e m e n t an d a id e d i n t h e f i e l d w o rk .
The s tu d y was f i n a n c e d by th e M ontana C o o p e r a tiv e F i s h e r y U n i t . .
iv
TABLE OF CONTENTS
P age
VITA . . , ..................................................... .................................................... ' . . .
ACKNOWLEDGMENT , .............................
.......................................
iii
LIST OF TABLES ,..................................................... .... ...................................... . . .
v
LIST OF FIGURES
. . . . . . .
ii
....................................... . . . . . . . . . . . . . .
ABSTRACT ..................................................................................
INTRODUCTION .
. . . . . . . . .
vi
v ii
. ' ................... • „ . . . . ...........................................................
I
DESCRIPTION OF STUDY A R E A ..................................................... , ........................
2
M E T H O D S................... ' ........................................................... , ......................................
5
RESULTS
9
...............................................................
. . . . .
..................................
S p a w n i n g ..................................
P o p u l a t i o n E s t i m a t e s - .............................
Age and G row th
......................................................................................
F e c u n d it y ....................................................................................... . . . . .
9
13
21
25
D ISC U SSIO N .........................................................................................................................
27
LITERATURE CITED
28
V
L I S T OF TABLES
T a b le .
1.
2.
3.
4.
5.
6.
7.
8.
'
P age
C h e m ic a l .and p h y s i c a l p r o p e r t i e s o f Lake Agnes summer 1 9 7 1 ................... .... .................................................................................
3
Summary o f sp a w n in g s tr e a m te m p e r a t u r e s and a v e r a g e c a tc h
p e r d a y o f unm arked g r a y l i n g , 1 9 7 1 .................................................
9
C a tc h s t a t i s t i c s an d s e x r a t i o s o f g r a y l i n g i n . t h e
1971 s p a w n in g r u n ............................. ■ . . ..................................................
12
A c o m p a ris o n b e tw e e n t h e num bers o f g r a y l i n g r e c a p t u r e d
i n a n d o u t s i d e t h e a r e a o f i n i t i a l m a rk in g ( p e r c e n t i n
p a re n th e s e s )
........................ . . . . . .
............................................
17
C a tc h s t a t i s t i c s (1971) f o r a d u l t g r a y l i n g w ith P e t e r s o n
p o p u l a t i o n e s t i m a t e s , c o n f id e n c e i n t e r v a l s ( C l ) , an d
s t a n d i n g c ro p f o r e a c h s e x an d s i z e g r o u p ........................ .... .
19
A summary o f a d u l t g r a y l i n g c a tc h s t a t i s t i c s w i t h P e t e r s o n
and S c h n a b e l .p o p u l a t i o n e s t i m a t e s a n d c o n f id e n c e i n t e r v a l s
(C l) f o r t h e m a le , f e m a le , and t o t a l p o p u l a t i o n ....................
20
A v e ra g e c a l c u l a t e d t o t a l l e n g t h s i n c e n t i m e t e r s a t e a c h
a n n u lu s f o r g r a y l i n g c o l l e c t e d d u r i n g 1971 . ■........................
22
A v e ra g e num ber o f e g g s p e r fe m a le by s i z e g ro u p s f o r 27
g r a y l i n g ta k e n i n 1 9 7 1 .............................................................................
26
vi
L IS T OF FIGURES
F ig u re
1.
P age
Map o f Lake A gnes sh o w in g t r a p l o c a t i o n s and t h e p e r c e n t
o f t h e t o t a l num ber o f g r a y l i n g c a u g h t i n t r a p n e t s i n
e a c h a r e a t h a t h a d b e e n m ark ed i n t h e sp a w n in g r u n . . . .
8
2.
L e n g th - f r e q u e n c y o f 2 ,2 1 2 fe m a le and 870 m ale g r a y l i n g
c a p t u r e d in , t h e 1971 sp a w n in g r u n ..................................................... 14
3.
L e n g th - f r e q u e n c y o f 1 ,1 8 9 m a tu re m a le , 1 ,3 8 6 m a tu r e f e ­
m ale , and 489 im m a tu re g r a y l i n g c a p t u r e d i n t r a p s d u r i n g
J u l y 1971 . . ' .......................................■ ............................................ ....
16
C o m p a riso n o f g ro w th r a t e s f o r g r a y l i n g i n M ontana . . . .
23
I
4.
v ii
ABSTRACT
The b i o l o g y a n d p o p u l a t i o n d y n a m ic s o f t h e g r a y l i n g i n Lake Agnes
w e re s t u d i e d d u r i n g t h e sum m ers o f 1970 a n d 1 9 71. I n 1 9 7 1 , t h e i c e
c l e a r e d fro m t h e l a k e on May 2 8 , a n d t h e p e a k o f spaw ning- m ig r a ti o n s
o c c u r r e d fro m J u n e 15 t o 2 4 . A d i u r n a l m ovem ent o f sp a w n in g g r a y l i n g
i n t o and o u t o f t h e i n l e t s tr e a m was c l o s e l y c o r r e l a t e d t o d a i l y
f l u c t u a t i o n s i n s tr e a m t e m p e r a t u r e s .
The s e x r a t i o o f 9 ,3 5 4 f i s h
c a p t u r e d i n t h e s p a w n in g r u n was 2 .5 fe m a le s f o r e v e ry m a le . I n t e n s i v e
t e r r i t o r i a l b e h a v i o r b e tw e e n sp a w n in g m a le s was n o te d a lo n g th e s h o r e ­
l i n e and a t t h e m outh o f t h e i n l e t and p r o b a b l y d e t e r r e d Iqany m a le s
fro m e n t e r i n g t h e s tr e a m . M ale g r a y l i n g g e n e r a l l y a v e r a g e d l a r g e r i n
s i z e and grew f a s t e r t h a n f e m a le s .
G r a y lin g from Lake A gnes show ed t h e
s l o w e s t a v e r a g e g ro w th r a t e o f any r e p o r t e d i n M o n tan a. A few g r a y l i n g
m a tu re d a t pge I I , h o w e v e r , m o st m a tu r e d a t a g e I I I .
O nly one a d u l t
g r a y l i n g o u t o f 559 was a g e d a s o v e r 6 y e a r s o l d .
The num ber o f eg g s
p e r fe m a le i n c r e a s e d w i t h t h e s i z e o f t h e f i s h and a v e r a g e d 356 eggs
p e r ou n ce o f f i s h .
The a d u l t p o p u l a t i o n w as e s t i m a t e d u s i n g t h e
P e t e r s o n m eth o d an d t h e S c h n a b e l m e th o d . The t o t a l e s t i m a t e b a s e d on
t h e P e t e r s o n m ethod was 2 4 ,2 1 4 w i t h a s t a n d i n g c ro p o f 7 2 .8 k g / h a .
T o t a l p o p u l a t i o n e s t i m a t e s w e re i n c l o s e a g re e m e n t b e tw e e n b o t h m e th o d s ,
h o w e v e r, m a le an d fe m a le e s t i m a t e s b a s e d on t h e S c h n a b e l m eth o d w ere
4 7 .5 p e r c e n t h i g h e r and 1 8 .1 p e r c e n t l o w e r , r e s p e c t i v e l y , t h a n compa­
r a b l e P e t e r s o n e s t i m a t e s . R e a so n s f o r p a s t f l u c t u a t i o n s i n num bers
an d s i z e o f f i s h a r e d i s c u s s e d .
INTRODUCTION
The A r c t i c g r a y l i n g
Thymatlus avcticus ( P a l l a s ) , commonly o c c u r s
th r o u g h o u t n o r t h w e s t e r n C anada i n and n o r t h o f t h e P e a c e , A th a b a s k a ,
an d C h u r c h i l l R i v e r s , and i n A la s k a .
As a r e s u l t o f g l a c i a l a c t i v i t y
w h ic h i s b e l i e v e d t o h a v e e x te n d e d t h e i r r a n g e s o u th w a r d , r e l i c t g r a y ­
l i n g p o p u l a t i o n s h i s t o r i c a l l y h a v e b e e n p r e s e n t i n M ic h ig a n and M ontana
(V in c e n t 1 9 6 2 ) .
A lth o u g h o n c e f a i r l y a b u n d a n t i n b o th o f t h e s e l o c a ­
t i o n s , t h e g r a y l i n g h a s becom e e x t i n c t i n M ic h ig a n and h a s h a d i t s
r a n g e a n d num bers g r e a t l y r e d u c e d i n M o n ta n a .
The o r i g i n a l r a n g e o f t h e g r a y l i n g i n M ontana e n c o m p a sse d t h e h e a d ­
w a t e r s o f t h e M is s o u r i R iv e r ab o v e G r e a t F a l l s .
H ere t h e y w e re c h i e f l y
fo u n d i n t h e J e f f e r s o n , M a d is o n , G a l l a t i n and S m ith R i v e r s and t h e i r
t r i b u t a r i e s , a n d i n t h e Sun R i v e r .
T o d a y , t h e o n ly i m p o r t a n t re m n a n t o f t h e s e o r i g i n a l p o p u l a t i o n s
o c c u r s on t h e Red r o c k L a k e s N a t i o n a l W i l d l i f e R e fu g e i n s o u th w e s te r n
M o n tan a.
L a t e s t r e c o r d s i n d i c a t e t h a t t h e r e a r e 39 s e l f - s u s t a i n i n g
g r a y l i n g p o p u l a t i o n s i n l a k e s a n d 14 i n s tr e a m s t h r o u g h o u t w e s t e r n
M o n ta n a .
W ith t h e e x c e p t i o n o f t h e Red Rock L ak es a r e a an d t h e U pper
B ig H o le D r a in a g e , m o s t o f t h e s e p o p u l a t i o n s a r e t h e r e s u l t o f i n t r o ­
d u c tio n s
(H o lto n 1971) .
Lake A gnes i s c o n s i d e r e d one o f t h e b e s t g r a y l i n g l a k e s i n M o n ta n a .
I n t h e p a s t , t h e g r a y l i n g o f t h i s l a k e h a v e shown c o n s i d e r a b l e f l u c t u ­
a t i o n i n num bers o f f i s h an d s i z e o f i n d i v i d u a l s .
The p r i n c i p a l
-2 -
o b j e c t i v e s o f t h e p r e s e n t s t u d y , c o n d u c te d d u r in g t h e sum m ers o f 1970
a n d 1 9 7 1 , w e re t o d e te r m in e th e p r e s e n t s t a t u s o f t h e p o p u l a t i o n and
g a t h e r a d d i t i o n a l i n f o r m a t i o n on t h e b i o l o g y o f t h e s p e c i e s .
DESCRIPTION OF STUDY AREA
L ake A gnes i s
l o c a t e d i n t h e P i o n e e r M o u n ta in s o f s o u th w e s te r n
M o n ta n a , a p p r o x im a te ly 4 0 .2 k i l o m e t e r s n o r t h o f D i l l o n .
I t lie s in a
h i g h m o u n ta in b a s i n a t an e l e v a t i o n o f 2 .3 k i l o m e t e r s a n d i s s u rr o u n d e d
by c o n i f e r - c o v e r e d h i l l s w h ic h s l o p e s t e e p l y t o t h e s h o r e .
I n th e
e a r l y 1 9 3 0 's , g r a y l i n g w e re i n t r o d u c e d i n t o t h e la k e w h ic h was o r i g i ­
n a l l y d e v o id o f f i s h .
The i n t r o d u c t i o n w as s u c c e s s f u l a n d fro m 1940
u n t i l t h e e a r l y 1 9 6 0 's , t h e s e g r a y l i n g w e re t h e p r im a r y s o u r c e o f e g g s
f o r t h e M ontana F i s h and Game D e p a rtm e n t.
The num ber o f e g g s t a k e n
p e r y e a r v a r i e d from 3 0 0 ,0 0 0 t o a lm o s t 4 ,5 0 0 ,0 0 0 .
Lake A gnes i s one o f t h r e e n a t u r a l l a k e s i n t h e Rock C re e k D r a in ­
ag e w h ic h a r e u s e d f o r i r r i g a t i o n p u r p o s e s .
la k e was m o d if ie d t h r o u g h t h e i n s t a l l a t i o n
The n a t u r a l o u t l e t o f t h e
o f a h e a d g a te t o r e g u l a t e
t h e w ith d r a w a l o f w a t e r w h ic h u s u a l l y b e g in s i n l a t e sum m er.
I n 1970
a n d 1 9 7 1 , drawdown b e g a n on A u g u st 22 and 1 5 , r e s p e c t i v e l y .
D u rin g
b o t h y e a r s , t h e la k e l e v e l was lo w e re d a p p r o x im a te ly 1 .5 m e t e r s , b u t a
2 .1 m e te r draw down i s p o s s i b l e when t h e l a k e i s
f i l l e d to c a p a c ity .
h i g h w a t e r i n 1970 a n d 1 9 7 1 , t h e l a k e c o n t a i n e d 4 0 .9 h e c t a r e s
s u rfa c e a c re s)
o f w a t e r and a f t e r draw dow n, 3 7 -5 h e c t a r e s .
w a t e r , t h e l a k e h a s a s h o r e l i n e d e v e lo p m e n t o f 1 .5 4 .
(101
A t h ig h -
At
—3 —
The maximum d e p th o f Lake Agnes a t h i g h w a t e r was 1 7 .7 m e te r s
fe e t).
(58
A t t h i s t i m e , 22 p e r c e n t o f t h e l a k e a r e a was 6 .1 m e te r s d e e p
o r l e s s and 44 p e r c e n t was 1 2 .2 m e te r s d e e p o r m o re.
D u rin g J u l y and
A u g u s t o f 1 9 7 1 , a t h e r m o c l i n e was p r e s e n t a t t h e 6 .1 m e te r d e p t h .
By
A u g u s t, t h e r e was a p r o g r e s s i v e d e c l i n e i n t h e am ount o f d i s s o l v e d
o x y g en b e lo w 9 .1 m e te r s a n d a t a d e p th o f 1 2 .2 m e te r s o r m o re , th e
c o n c e n t r a t i o n was l e s s t h a n I ppm.
O th e r c h e m ic a l a n d p h y s i c a l c h a r ­
a c t e r i s t i c s o f Lake A gnes f o r t h e summer o f 1971 a r e l i s t e d i n T a b le I
T a b le I .
C h e m ic a l a n d p h y s i c a l p r o p e r t i e s o f Lake Agnes - su m m er.1971.
R ange
pH
A v e ra g e
7 .5 6 - 8 .0 5 ■
—
T o ta l A lk a lin ity
(ppm CaCOg)
7 1 .4 - 7 1 .8
7 1 .6
T o t a l H a rd n e ss
(ppm CaCO3 )
2 8 .0 - 3 1 .8
2 9 .7
C o n d u c t iv i ty
(m ic ro ohms)
8 0 .0 - 8 2 .0
8 0 .7
7 .0 - 8 .0
7 .5
T u rb id ity
(JTU)
W a te r T e m p e ra tu re s
0 .6 m e te r s b e lo w s u r f a c e
(Maximum)
1 0 .0 C - 1 9 .0 C
W a te r T e m p e r a tu r e s
0 .6 m e te r s b e lo w s u r f a c e
(Minimum)
6 .0 C - 1 3 .0 C
1 5 .4 C
■
10.8 C
-4 —
The p r im a r y i n l e t s tr e a m e n t e r s t h e l a k e from t h e w e s t an d i s t h e
m a jo r sp a w n in g a r e a .
I t has i t s
s o u r c e , p r i n c i p a l l y fro m r u n o f f , i n
th e s u rro u n d in g h i l l s
a n d m ea n d e rs t h r o u g h s e v e r a l a b a n d o n e d b e a v e r
im poundm ents b e f o r e r e a c h i n g t h e lak e=
The p e r i o d o f h i g h flo w f o r
t h e i n l e t s tr e a m o c c u r s i n Ju n e and c o i n c i d e s w i t h t h e s p a w n in g s e a s o n
o f th e g r a y lin g .
m3/m in
A t t h i s t i m e , t h e s tr e a m flo w s a s much a s 3 .4 t o 5 .1
(2 -3 c f s ) , h o w e v e r, by t h e e n d o f J u l y t h e flo w i s much r e d u c e d .
I n t h e p a s t when b e a v e r w e re a c t i v e d u r i n g a low w a te r y e a r , l i t t l e
or
n o w a t e r flo w e d b e lo w t h e dams an d a v a i l a b l e s tr e a m sp a w n in g a r e a was
p r a c t i c a l l y e lim in a te d
(R o b e rt A. M i t c h e l l - p e r s o n a l c o m m u n ic a tio n ) .
The s tr e a m i s s t i l l i n t h e p r o c e s s o f e r o d i n g i t s way t h r o u g h o l d b e a v e r
im p o u n d m e n ts.
As a r e s u l t , t h e s tr e a m b e d an d b a n k s a r e v e r y u n s t a b l e
a n d b a n k c a v e - i n s d u r in g t h e p e r i o d o f h i g h flo w a r e n o t uncommon.
Due
t o t h e c h a n g in g n a t u r e o f t h e s tr e a m , n a t u r a l o b s t r u c t i o n s . f o r m ig r a t i n g
g r a y l i n g p e r i o d i c a l l y o c c u r a n d t h e p o r t i o n o f t h e s tr e a m a v a i l a b l e f o r
s p a w n in g may v a r y g r e a t l y fro m y e a r t o y e a r .
i n 1 9 3 6 , a b o u t 9 1 .4 m e te r s
Brown (1938) fo u n d t h a t
(100 y a r d s ) o f s tr e a m a d j a c e n t t o t h e la k e
w e re a v a i l a b l e f o r s p a w n in g .
I n 1 9 7 0 , 1 8 1 .0 m e te r s w e re a v a i l a b l e f o r
s p a w n in g , b u t o n ly 4 3 .9 m e te r s i n 1 9 71.
The s tr e a m b o tto m c o n s i s t e d
o f a c o a r s e , g r a n u l a r s a n d ; 57 p e r c e n t o f t h e p a r t i c l e s b e in g from 10.-0
t o 1 .9 8 1 mm i n d i a m e t e r , 28 p e r c e n t fro m 1 .9 8 0 t o 0 .8 3 3 mm, a n d th e
r e m a in d e r made up o f s m a l l e r m a t e r i a l .
Two s m a l l t r i b u t a r i e s e n t e r t h e
l a k e a lo n g t h e s o u th s h o r e , b u t o n ly a b o u t 3 .1 t o 6 .1 m e te r s o f e a ch
-5 -
w e re a v a i l a b l e
f o r s p a w n in g .
T h e se c e a s e d f lo w in g by t h e b e g in n i n g o f
A u g u s t.
The m a jo r a q u a t i c p l a n t s o f Lake A gnes w e re
Potcmogeton praelonguss
Potamogeton nodosa3 Potamogeton Tobbins-H3 and MyTiophyltum s p .
T h ese
o c c u r r e d i n t h i c k b e d s a lo n g t h e s h o r e , many o f them a t d e p th s o f o v e r
1 .5 m e t e r s .
A ls o p r e s e n t i n l e s s e r q u a n t i t i e s w e re
peotinatus a n d Potamogeton s p .
much o f t h e l a k e an d
Potamogeton
ChaTa s p . w as q u i t e common th r o u g h o u t
M t e l l a s p . was a l s o p r e s e n t .
METHODS
The g r a y l i n g p o p u l a t i o n o f L ake A gnes was e s t i m a t e d d u r in g t h e
summer o f 1971 by tw o m ark and r e c a p t u r e m e th o d s .
P o p u la tio n e s tim a te s
u s in g t h e P e t e r s o n m eth o d w e re b a s e d on d a t a o b t a i n e d by m a rk in g f i s h
i n t h e i n l e t and r e c a p t u r i n g f i s h i n t h e l a k e by t r a p p i n g .
P o p u l a ti o n
e s t i m a t e s u s i n g t h e S c h n a b e l m ethod w e re b a s e d e n t i r e l y on d a t a ob­
t a i n e d by t r a p p i n g f i s h i n t h e l a k e .
I n s t i t u t e f o r F i s h e r i e s R e s e a rc h
F o rm u la 5 o f t h e M ic h ig a n
(1960) was u s e d f o r p o p u l a t i o n e s t i ­
m a te s b a s e d on t h e P e t e r s o n m ethod ( B a ile y m o d i f i c a t i o n ) w i t h c o n f id e n c e
i n t e r v a l s co m puted u s i n g f o rm u la 6 .
P o p u l a t i o n e s t i m a t e s b a s e d on th e
S c h n a b e l m eth o d w e re made u s i n g f o rm u la 3 .1 2 o f R ic k e r (1958) w ith
c o n f id e n c e i n t e r v a l s co m puted u s in g f o rm u la s 3 .1 3 and 3 .1 4 .
S paw ning g r a y l i n g w e re c a p tu r e d a t random i n t h e i n l e t th r o u g h o u t
t h e sp a w n in g r u n s o f 1970 an d 1971 by h e r d i n g them d o w n stre a m i n t o l i v e
boxes.
C a p tu r e r u n s w e re s t a r t e d i n l a t e m o rn in g when s u f f i c i e n t
“ 6—
num bers o f f i s h h a d c o n c e n t r a t e d b e lo w t h e b a r r i e r a n d w e re r e p e a t e d
th r o u g h o u t t h e .day u n t i l t h e num ber o f m ark ed f i s h e x c e e d e d t h e num ber
o f unm arked f i s h i n t h e s a m p le .
L e n g th , w e i g h t , and s e x w e re r e c o r d e d
a n d s c a l e s a m p le s w e re t a k e n fro m e a c h f i s h c a p t u r e d i n 1 9 7 0 .
Due t o
th e l a r g e num ber o f f i s h h a n d le d i n t h e 1971 sp a w n in g s e a s o n , l e n g t h s ,
w e ig h ts , a n d s c a l e s a m p le s w e re t a k e n fro m a p p r o x im a te ly 50 f i s h o f
each se x f o r each c e n tim e te r s iz e i n t e r v a l .
I n a d d i t i o n , l e n g t h s w ere
t a k e n on a b o u t 30 p e r c e n t and s e x was d e te r m in e d on a l l f i s h c a p tu r e d .
I n 1 9 7 0 , a v a r i e t y o f a r t i f i c i a l t a g s w e re u s e d , b u t i n 1971 a l l f i s h
w e re m arked b y c l i p p i n g t h e a d ip o s e f i n .
D e te r m in a tio n o f s e x o f m a tu re f i s h was b a s e d on t h e s i z e and s h a p e
o f th e d o r s a l f i n
(Ward 1951) .
Im m atu re g r a y l i n g w e re s e p a r a t e d fro m
m a tu re f i s h by v i s u a l i n s p e c t i o n .
Im m a tu re s h a d s i l v e r y b o d i e s and
s m a ll, l i g h t c o lo re d d o r s a l f i n s .
A d u lts h a d l a r g e r , m ore b r i l l i a n t l y
c o l o r e d d o r s a l f i n s an d d a r k e r b o d i e s .
I n a d d i t i o n , many m a tu r e m a le s
s t i l l e x u d e d a s m a l l am ount o f m i l t when h a n d le d and f e m a le s h a d v e r y
f l a c c i d ab d o m en s.
G r a y li n g w e re t r a p p e d i n th e l a k e w i t h m o d if ie d fy k e n e t s .
Each
n e t c o n s i s t e d o f a 3 .7 - m e t e r lo n g hoop n e t w i t h a 0 .9 - m e t e r d ia m e te r
o p e n in g , p r e c e d e d by a O i9 x 1 .8 x 0 .6 m e te r b o x o f m esh c o v e r e d s t e e l
fra m e s.
L e a d s , 1 .2 m e te r s h i g h , w e re a t t a c h e d t o t h e b o x a n d v a r i e d
i n l e n g t h from 7 .6 t o 1 5 .2 m e t e r s .
I n 1 9 7 0 , tw o m o d if ie d fy k e n e t s
w e re u s e d and o n ly a s m a ll p o r t i o n o f t h e la k e w as s a m p le d .
I n 1971,
—7 —
f o u r m o d if ie d fy k e n e t s w e re u s e d and t h e t r a p s w ere moved t o a new
l o c a t i o n e a c h d a y u n t i l a l l o f th e s u i t a b l e p o r t i o n o f t h e s h o r e l i n e ,
a b o u t 75 p e r c e n t , w as s a m p le d .
P o r t i o n s n o t t r a p p e d w e re p r i m a r i l y
t h r e e a r e a s w h e re t h e b o tto m s lo p e d t o o s t e e p l y
( F ig . I ) .
A l l t r a p p e d f i s h w e re m e a s u re d , s e x e d , m a rk e d , and r e l e a s e d n e a r ,
t h e i r p o in t o f c a p tu re .
I n 1 9 7 1 , t h e l a k e was d i v i d e d i n t o f i v e a r e a s
an d t h e f i s h c a p t u r e d i n e a c h a r e a w e re m arked w i t h a d i s t i n c t i v e
p a r tia l fin c lip .
H o le s p u n c h e d i n t h e a n a l f i n w e re u s e d t o i n d i c a t e
t h e num ber o f tim e s a f i s h h a d b e e n r e c a p t u r e d i n a p a r t i c u l a r a r e a .
W h ile t r a p s w e re i n o p e r a t i o n , a p a r t i a l c r e e l c e n s u s was c o n d u c te d t o
d e te r m in e t h e p r o p o r t i o n o f m arked t o unm arked f i s h h a r v e s t e d .
P r i o r t o an d d u r i n g t h e e a r l y p a r t o f t h e sp a w n in g r u n i n 1 9 7 1 ,
f e m a le s w e re c o l l e c t e d t o o b t a i n . e g g s a m p le s .
F em ales w e re p r e s e r v e d
i n 10 p e r c e n t f o r m a li n and t h e e g g s l a t e r rem oved a n d s t o r e d i n 40 p e r ­
c e n t i s o p r o p a l a l c o h o l u n t i l c o u n te d .
F r y an d f i n g e r l i n g s w e re
c o l l e c t e d b y d i p n e t t i n g a lo n g t h e s h o r e a n d e l e c t r o f i s h i n g th e s h o a l
a re a s.
A c o n s t a n t r e c o r d i n g T a y lo r th e rm o g ra p h was p l a c e d i n t h e i n l e t
i n 1971 t o m o n it o r s tr e a m t e m p e r a t u r e s d u r i n g t h e sp a w n in g r u n .
T a y lo r
maximum-minimum th e rm o m e te rs w e re p l a c e d i n two p o s i t i o n s 0 .6 m e te rs
b e lo w t h e s u r f a c e o f t h e l a k e d u r in g t h e summer m o n th s.
T e m p e ra tu re
p r o f i l e s w e re o b t a i n e d w i t h an ARA m o d el FT3 A ll-W e a th e r H y d ro g ra p h ic
T h e rm o m e te r.
W a te r c h e m is tr y a n a l y s i s f o llo w e d p r o c e d u r e s o u t l i n e d i n
S t a n d a r d M ethods f o r t h e E x a m in a tio n o f W a te r and W aste W a te r (1 9 7 1 ).
OUTLET
PRIMARY
INLET
F ig u re I .
Map o f Lake Agnes sh o w in g t r a p l o c a t i o n s and t h e p e r c e n t o f th e t o t a l num ber
o f g r a y l i n g c a u g h t i n t r a p n e t s i n e a c h a r e a t h a t h a d b e e n m arked i n th e
sp a w n in g r u n .
-9 -
RESULTS
S paw ning
The i c e c l e a r e d from Lake Agnes on May 2 8 , 1971.
a p p e a r e d i n t h e i n l e t f o r sp a w n in g on J u n e 7„
G r a y li n g f i r s t
The p e a k o f th e sp a w n in g
r u n o c c u r r e d from J u n e 15 t o 2 4 , a n d g r a d u a l l y t a p e r e d o f f u n t i l J u l y
6 , when few f i s h w e re s e e n .
F i s h a p p a r e n t l y b e g a n m oving i n t o th e i n ­
l e t when t h e a v e r a g e d a i l y s tr e a m t e m p e r a t u r e s a p p ro a c h e d 2 .8 C (37 F)
(T a b le 2 ) .
The s u r f a c e l a k e w a t e r warmed m ore r a p i d l y t h a n t h e s tr e a m
T a b le 2 . Summary o f sp a w n in g s tr e a m te m p e r a t u r e s a n d a v e r a g e c a tc h p e r
____________ day o f unm ark ed g r a y l i n g , 1 9 7 1 ._______________ ____________________
Time
P e rio d
Maximum
Temp.
Minimum
T e m p .■
A v e ra g e -'
D a ily
Temp.
A v e ra g e
h o u rs /d a y
O ver 4 .4 C
0 .6 C
( 3 3 . 0 F)
1 .9 C
(3 5 .5 F)
1 .3
6 /1 -6 /4
5 .3 c ■
(4 1 .5 F)
0 .6 C
(3 3 .0 F)
1.8 c •
( 3 5 .4 F)
0 .7
6 /5 -6 /8
6 .7 C
(4 4 .0 F)
0 .6 C
(3 3 .0 F)
2 .4 C '
(3 6 .7 F)
4 .4
6 /9 -6 /1 2
6.7 C
(4 4 .0 F)
1 .1 C
F)
2 .4 C
( 3 6 . 7 F)
1 .6
6 /1 3 -6 /1 6
7 .2 c •
(4 5 .0 F)
1 .1 C
(3 4 .0 F)
2.9 C ■
(3 7 . 6 ■F)
6.4
7 .5
*
O
6 .8 C
(4 4 . 5 F)
CO
5 /2 8 -5 /3 1
6 /1 7 - 6 / 2 0
8 .3 C
. (4 7 . 0 F)
1 .3 C
(3 4 .5 F)
3 .4 C .
( 3 8 .4 F)
6 /2 1 -6 /2 4
1 0 .6 C
(5 1 .0 F )
2 .2 C
(3 6 .0 F)
5 .1 C
(4 1 .3 F)
1 1 .6
6 /2 5 - 6 / 2 8
8 .3 C (4 7 .0 F)
2 .2 C
(3 6 .0 F)
3 .9 C
(3 9 .0 F)
6 .0
A verage
C a tc h
P e r Day
1,-240
935 '
906
133 ■
—1 0 —
a n d may h a v e i n f l u e n c e d m ovem ents o f t h e g r a y l i n g p r i o r t o an d d u r in g
th e ru n .
From Ju n e 11 t o 2 4 , t h e maximum a n d minimum te m p e r a t u r e s o f
t h e l a k e w a t e r w e re 2 .8 C ° (5 F ° ) t o 4 .4 C ° (8 F ° ) h i g h e r t h a n s tr e a m
te m p e ra tu re s .
I c e c l e a r e d from t h e l a k e on J u n e 2 , 1 9 7 0 , a n d t h e p e a k
o f t h e r u n o c c u r r e d fro m J u n e 11 t o 2 0 .
G ra y lin g , e x h i b i t e d a m ark ed d i u r n a l f l u c t u a t i o n I n nu m b ers p r e s e n t
i n t h e i n l e t d u r i n g t h e sp a w n in g r u n b o t h y e a r s .
A round m id - d a y , l a r g e
s c h o o ls w e re o b s e r v e d e n t e r i n g t h e s tr e a m an d p e a k num bers w e re r e a c h e d
by l a t e a fte rn o o n .
F i s h b e g a n m oving d o w n stre a m i n e a r l y e v e n in g and
o n ly a s m a l l num ber o f f i s h r e m a in e d i n t h e s tr e a m o v e r n i g h t .
B ish o p
(1971) fo u n d a s i m i l a r d i u r n a l m ovem ent o f sp a w n in g g r a y l i n g i n P r o v i ­
d e n c e C r e e k , C a n a d a , w i t h no f i s h o b s e r v e d i n t h e c r e e k d u r i n g t h e n i g h t
a n d l a r g e num bers m oving u p s tr e a m a ro u n d n o o n .
On l a r g e r o r l o n g e r •
t r i b u t a r i e s , s i m i l a r d i u r n a l m ovem ents h a v e n o t b e e n r e p o r t e d
(N elso n
1 9 5 4 , K ru s e 1 9 5 9 ) .
The d i u r n a l m ovem ent i n and o u t o f t h e sp a w n in g s tr e a m was c l o s e l y
r e l a t e d t o t e m p e r a t u r e ..
L a rg e num bers o f f i s h e n t e r e d t h e i n l e t when
s tr e a m t e m p e r a t u r e s w e re 4 .4 C (40 F) o r h i g h e r , an d t h i s se ld o m o c ­
c u rre d b e fo re noon.
Maximum t e m p e r a t u r e s w e re r e a c h e d b e tw e e n 3 :0 0 and
6 :0 0 p .m . an d f e l l b e lo w 4 .4 C by l a t e e v e n in g .
C o ld , c lo u d y d a y s w i t h
r a i n o r snow lo w e re d maximum s tr e a m t e m p e r a t u r e s and t h i s i n t u r n , h a d
a d e p r e s s i n g e f f e c t on t h e num bers o f f i s h m oving u p s tr e a m .
a n d G u s ta f s o n
F a b ric iu s ■
(1955) c o n c lu d e d t h a t t h e d a i l y rh y th m o f w a t e r t e m p e r a t u r e s
—1 1 —
was v e r y m ark ed i n s h a ll o w s tr e a m s and w as t h e m o st i m p o r t a n t s ti m u lu s
a f f e c t i n g t h e g r a y l i n g 's rh y th m o f sp a w n in g a n d d e f e n s e o f t e r r i t o r y .
S paw n in g f i s h w e re a l s o o b s e r v e d i n t h e tw o s m a l l t r i b u t a r i e s .
S e v e r a l o f t h e s e f i s h h a d b e e n p r e v i o u s l y c a u g h t i n t h e p r im a r y i n l e t
s tr e a m a n d m a rk e d .
I n a d d i t i o n , sp a w n in g a c t i v i t y was n o t e d a lo n g th e
s h o r e lin e o f th e la k e .
T h is a p p e a r e d q u i t e i n t e n s i v e a t tim e s w ith a s
many a s s i x o b s e r v a t i o n s i n 30 m i n u t e s .
A l l o f t h e o b s e r v a t i o n s w ere
made i n s h a ll o w w a t e r o v e r s m a ll g r a v e l o r c o a r s e s a n d b o t t o m s , ho w ev er
v i s i b i l i t y w as l i m i t e d i n d e e p e r w a t e r s a n d o v e r d a r k e r m u d -b o tto m
ty p e s .
D u rin g t h e sp a w n in g s e a s o n , c e r t a i n m ale g r a y l i n g a p p e a r e d t o
e s ta b lis h t e r r it o r i e s
an d a c t i v e l y d e f e n d th em a g a i n s t i n t r u d i n g m a le s .
T h is a n t a g o n i s t i c b e h a v i o r was m o st f r e q u e n t l y o b s e r v e d a lo n g t h e s h o r e
l i n e and a t t h e .m outh o f t h e i n l e t .
L ittle
o r no a n ta g o n is m was n o te d
i n t h e s tr e a m a t t h e p e a k o f t h e r u n when sp a w n in g d e n s i t i e s w e re e x ­
tr e m e ly h i g h , h o w e v e r, c o n s i d e r a b l e c o n f l i c t was o b s e rv e d a t t h e m outh
o f th e i n l e t a t t h i s tim e .
e n t e r i n g t h e s tr e a m .
T h is may h a v e d e t e r r e d many m a le s from
No a g g r e s s i v e b e h a v i o r o f m a le s to w a rd s fe m a le s
o r b e tw e e n f e m a le s was n o t e d .
A t o t a l o f 9 ,3 6 4 g r a y l i n g from t h e 1971 sp a w n in g r u n w as m arked
from J u n e 11 t o 2 8 .
f e m a le s .
The s e x r a t i o o f t h e s e f i s h was I m a le t o 2 .5
The s e x r a t i o s by d a y s o f c a p t u r e show a m ark ed i n c r e a s e i n
t h e p r o p o r t i o n o f f e m a le s d u r in g t h e l a t t e r p a r t o f t h e r u n
(T a b le 3 ) .
-1 2 -
T a b le 3 .
D a te ■
' C a tc h s t a t i s t i c s a n d s e x r a t i o s o f g r a y l i n g i n t h e 1971 .
s p a w n in g r u n .
T o t a l Number
of .
F i s h M arked
S ex R a t i o
cf/9
T o t a l Number
of
R e c a p tu r e s
S ex R a tio
( R e c a p tu re s )
cr/9
6 / 1 1 /7 1 •
370
1 / 2 .7
—
6 / 1 2 /7 1
727
1 / 2 .3
207
6 /1 5 /7 1
976
1 / 2 .3
277
— --
1 /2 .1
627
1/ 2 . 7
6/ 1 6 / 7 1
1 ,5 0 3 .
6 / 1 7 /7 1
733
1 / 3 .0
612
1 / 3 .1
6 /1 9 /7 1
1 ,0 5 5
1 / 2 .5
498
1/ 3 . 0
6 / 2 0 /7 1
1 ,0 1 7
1/ 2 . 8
354
1/ 4 . 2
6/ 2 2 / 7 1
871
1 /2 .1
498 '
1 / 1 .9
6/ 2 3 / 7 1
1 ,0 3 5
1/ 2 . 3
622
1/ 3 . 0
6/ 2 4 / 7 1
811
1 / 3 .1
717
1/ 3 . 0
6 / 2 7 /7 1
208
1 / 4 .5
178
1/ 3 . 1
58
1/ 6 . 2
48
1/ 2 . 7
6 / 2 8 /7 1 .
.T o ta l
9 ,3 6 4
1 /2 .51
4 ,6 3 8
1/ 2 . 9 ^
1A v e ra g e
,
I n 1 9 7 0 , a sa m p le o f 512 f i s h r e v e a l e d a s e x r a t i o o f I m a le t o 1 .8
fe m a le s .
B o th o f t h e s e s e x r a t i o s a r e s i g n i f i c a n t l y d i f f e r e n t from an
e x p e c te d 1 : 1 r a t i o
(x2 v a l u e s 1695 and 45 r e s p e c t i v e l y ) .
Brown (1938)
r e p o r t e d a m a l e - t o - f e m a l e r a t i o o f 1 . 5 : 1 i n h i s s tu d y s e c t i o n on t h e
i n l e t t o L ake A g n e s.
K ru s e
(1959) fo u n d a s e x r a t i o o f 1 :1 i n th e
sp a w n in g r u n o f g r a y l i n g i n G reb e L a k e , W yoming.
B is h o p
(1971) fo u n d
-1 3 -
a m a l e - t o - f e m a l e r a t i o o f 1 . 3 : 1 i n a sa m p le o f 168 g r a y l i n g fro m th e
sp a w n in g r u n i n P r o v id e n c e C r e e k , C a n a d a , b u t d i d n o t c o n s i d e r t h i s
s t a t i s t i c a l l y d i f f e r e n t fro m a 1 :1 r a t i o .
The h i g h e r p r o p o r t i o n o f
fe m a le s i n t h e s a m p le s o f r e c a p t u r e d f i s h w ould i n d i c a t e t h a t fe m a le s
e n t e r e d t h e s tr e a m m ore f r e q u e n t l y o r s t a y e d l o n g e r t h a n m a le s
(T a b le
3) .
The l e n g t h - f r e q u e n c y o f a d u l t f i s h c a p t u r e d i n t h e 1971 sp a w n in g
r u n i s shown i n F i g u r e 2 .
F e m ale s a v e r a g e d 2 6 .3 cm i n t o t a l l e n g t h and
r a n g e d fro m 2 2 .4 t o 3 3 .5 .
M ales a v e r a g e d .2 7 .9 cm an d r a n g e d from 2 4 .0
t o 3 5 .8 .
P o p u l a t i o n E s t im a t e s
T r a p p in g f i s h i n t h e l a k e i n 1971 b e g a n on J u l y 2 a n d was d i s ­
c o n ti n u e d a f t e r J u l y 1 6 .
D u rin g Ju n e an d t h e f i r s t w eek o f J u l y , l a r g e
s c h o o ls o f g r a y l i n g w e re o b s e r v e d swimm ing a lo n g t h e s h o r e .
The a v e r ­
a g e c a t c h p e r o v e r n i g h t t r a p s e t i n s h a ll o w w a t e r fro m J u l y 2 th r o u g h
9 was 142 f i s h .
A f t e r t h i s p e r i o d , few f i s h w e re o b s e r v e d f r e q u e n t i n g
t h e s h o a l a r e a s an d t h e a v e r a g e c a t c h p e r o v e r n i g h t s e t f e l l t o 69.
Warm s u r f a c e w a t e r t e m p e r a t u r e s w e re b e l i e v e d t o h a v e f o r c e d t h e g r a y ­
lin g in to d eep er w a te rs .
G i l l n e t s s e t on t h e b o tto m a t 1 2 .2 t o 1 5 .2
m e te r s on J u l y 20 a n d 21 y i e l d e d no g r a y l i n g , h o w e v e r, one s e t a t a b o u t
t h e 9 .1 m e te r d e p th c a u g h t 83 f i s h .
A b u n d a n t d i s s o l v e d o x y g en was
p r e s e n t a t 9 .1 m e te r s b u t l e s s t h a n 0 .5 ppm a t t h e d e e p e s t s e t s .
-1 4 -
- - FEMALES
MALES
TOTAL LENGTH-CENTIMETERS
F ig u re 2.
L e n g th - f r e q u e n c y o f 2 ,2 1 2 fe m a le and 870 m ale g r a y l i n g
c a p tu r e d i n t h e 1971 sp a w n in g r u n .
4
-1 5 -
A t o t a l o f 31 t r a p d a y s o f e f f o r t
( I t r a p d ay = I o v e r n i g h t s e t )
r e s u l t e d i n a c a tc h o f 1 ,1 8 9 a d u l t m a l e s , 1 ,3 8 6 a d u l t .f e m a le s , and 489
im m a tu re s .
Of t h e a d u l t f i s h t r a p p e d , 331 m a le s
(27,8% ) an d 600 fe m a le s
(43.3% ) h a d p r e v i o u s l y b e e n m ark ed i n t h e sp a w n in g r u n .
T h e .s e x r a t i o o f t h e - t r a p c a u g h t a d u l t s w as I m ale t o 1 .2 f e m a le s .
T h is was s t a t i s t i c a l l y
d i f f e r e n t fro m an e x p e c te d 1 :1 r a t i o
15) a n d fro m t h e s e x r a t i o o f t h e sp a w n in g r u n
(y 2 v a lu e
(x 2 v a lu e 2 8 6 ) .
The m ore
n e a r l y 1 :1 s e x r a t i o i n t h e l a k e an d t h e lo w e r p e r c e n t r e c a p t u r e o f m a le s
w o u ld i n d i c a t e t h a t a s m a l l e r p r o p o r t i o n o f t h e m ale p o p u l a t i o n th a n t h e
fe m a le w as p r e s e n t i n t h e sp a w n in g s tr e a m .
The a n t a g o n i s t i c b e h a v io r
n o t e d b e tw e e n m a le s a t t h e m outh o f t h e i n l e t p r o b a b l y c a u s e d t h i s .
The l e n g t h - f r e q u e n c y f o r a l l f i s h t r a p p e d i n 1971 i s shown i n
F ig u re 3.
The s m a l l e s t g r a y l i n g c a p t u r e d i n t h e t r a p s w as 9 .8 cm and
t h e l a r g e s t w as 3 2 .4 cm.
The a v e r a g e l e n g t h o f a d u l t m a le s was 2 7 .2
cm and r a n g e d fro m 2 3 .8 t o 3 2 .4 .
r a n g e d fro m 2 3 .0 t o 2 9 . 2 .
2 1 .8 and 2 5 .0 cm.
A d u lt f e m a le s a v e r a g e d 2 5 .9 cm and
A mode o f im m a tu re g r a y l i n g a p p e a r e d b e tw e e n
T h e se f i s h a v e r a g e d 2 3 .5 cm an d s c a l e a n a l y s i s r e ­
v e a le d t h e i r age as I I + .
F i s h i n a n o t h e r m ode, b e tw e e n 9 .8 and 1 8 .3 cm,
a v e r a g e d 1 3 .9 an d a l l w e re y e a r l i n g s .
A b a s i c a s s u m p tio n i n m aking p o p u l a t i o n e s t i m a t e s i s
t h a t th e
m ark e d f i s h d i s t r i b u t e th e m s e lv e s ra n d o m ly th r o u g h o u t t h e p o p u l a t i o n
b e in g e s tim a te d
( R ic k e r 1 9 5 8 ) .
An i n d i c a t i o n o f t h e d i s t r i b u t i o n o f
f i s h m ark ed i n t h e s p a w n in g r u n w as o b t a i n e d b y c o m p a rin g t h e p e r c e n t
—1 6 —
- - IMMATURES
FEMALES
----- MALES
15
20
25
TOTAL LENGTH - CENTIMETERS
F ig u re 3.
L e n g th - f r e q u e n c y o f 1 ,1 8 9 m a tu r e m a l e , 1 ,3 8 6 m a tu re f e m a le ,
and 489 im m atu re g r a y l i n g c a p t u r e d i n t r a p s d u r in g J u l y 1971.
—1 7 —
o f t h e t o t a l num ber o f g r a y l i n g c a u g h t i n e a c h a r e a t h a t w e re r e ­
c a p tu re s
( F ig . I ) .
T hese, r a n g e d fro m 32 t o 40 p e r c e n t w i t h th e a r e a
f a r t h e s t fro m t h e p o i n t o f m a rk in g h a v in g 37 p e r c e n t r e c a p t u r e s .
c a p t u r e s f o r t h e e n t i r e l a k e a v e r a g e d 35 p e r c e n t .
Re­
A l s o , 32 p e r c e n t
o f f i s h c a u g h t .by f i s h e r m e n ■h a d b e e n m ark ed i n t h e s p a w n in g r u n and
m o st o f t h e c a t c h o c c u r r e d i n a r e a s C., 'D , a n d E .
T hus, f o r th e .
P e t e r s o n e s t i m a t e , t h e a s s u m p tio n o f ra n d o m .d i s t r i b u t i o n w as m e t.
To d e te r m in e random d i s t r i b u t i o n o f t r a p - c a u g h t f i s h .in t h e la k e
f o r t h e S c h n a b e l m e th o d , a c o m p a ris o n w as made b e tw e e n t h e num ber o f
f i s h r e c a p t u r e d i n t h e a r e a o f i n i t i a l m a rk in g t o t h e num ber r e c a p t u r e d •
in o th e r a re a s
T a b le 4 .
(T a b le 4) .
A c o m p a ris o n b e tw e e n t h e num bers o f g r a y l i n g r e c a p t u r e d i n and o u t s i d e t h e a r e a o f i n i t i a l m a rk in g ( p e r c e n t i n p a r e n ­
t h e s e s ) . __________________________ ■
____________ .__________________:__
A re a o f
M a rk in g
A
B
■C
D
E
The p e r c e n t o f r e c a p t u r e s o c c u r r i n g i n ;t h e
A
4
8
2
3
2
(20)
(23)
(6)
(17)
(14)
B
9
7
7
6
2
(45)
(20)
(20)
(33)
(14)
A re a o f R e c a p tu r e
C
2
16
13
3
I
(10)
(45)
(37)
(17)
(7)
E
D
I
2
8
5
4
a r e a o f i n i t i a l m a rk in g v a r i e d fro m 20 t o 37 p e r c e n t .
(5)
(6 )
(23)
(28)
(29)
4
2
5
I
5
(2 0 )
(6 )
(14)
(5)
(36)
I n tw o o u t o f
f i v e c a s e s , t h e a r e a w i t h . f e w e s t r e c a p t u r e s was a l s o f a r t h e s t from t h e
a r e a o f i n i t i a l m a r k in g , h o w e v e r , sa m p le s i z e s o f r e c a p t u r e s w e re s m a l l.
T q overcom e p o t e n t i a l b i a s fro m n o n -ra n d o m m ix in g o f tr a p - m a r k e d f i s h .
—1 8 -
a l l o f t h e s u i t a b l e s h o r e l i n e r e c e i v e d a p p r o x im a te ly e q u a l p r e s s u r e
a n d t h e t r a p s w e re moved t o a new l o c a t i o n e a c h d a y .
F o r e s t i m a t e s o f t h e p o p u l a t i o n b a s e d on t h e P e t e r s o n m e th o d ,
g r a y l i n g w e re g ro u p e d i n t o f o u r s i z e i n t e r v a l s
f o r e a c h s e x t o a v o id
p o s s i b l e b i a s d u e .to a s m a l l e r p r o p o r t i o n o f t h e m ale p o p u l a t i o n b e in g
m ark ed a n d t r a p s e l e c t i v i t y b a s e d on s i z e .
The i n t e r v a l e s t i m a t e s .
w e re t h e n co m b in ed t o g iv e a d u l t m ale a n d fe m a le e s t i m a t e s an d a t o t a l
a d u lt p o p u la tio n e s tim a te
(T a b le 5 ) .
T h is r e s u l t e d i n an e s t i m a t e o f
1 4 ,9 9 7 a d u l t f e m a le s a n d 9 ,2 1 7 a d u l t m a l e s , f o r a t o t a l o f 2 4 ,2 1 4 .
F e m a le s fro m 2 4 .0 t o 2 7 .9 cm an d m a le s fro m 2 6 .0 t o 2 9 .9 cm
c o m p ris e d t h e b u l k o f t h e a d u l t p o p u l a t i o n .
u s i n g t h i s e s t i m a t e w as 7 2 .8 k g / h a
S ta n d in g c ro p o f a d u l t s
( 6 4 .8 l b s / a c r e ) .
K ru se
(1959)
fo u n d a s t a n d i n g c ro p o f 7 0 .2 I b s / a c r e f o r g r a y l i n g o v e r 4 .3 i n c h e s i n
G rebe L ake i n '1953 a n d 7 0 .9 I b s / a c r e f o r g r a y l i n g o v e r 8 .4 i n c h e s i n ,
1954.
E s t im a t e s o f t h e p o p u l a t i o n by t h e S c h n a b e l m ethod w e re b a s e d on •
119 r e c a p t u r e s fro m 2 ,4 1 8 m ark ed f is h .-
Due t o t h e s m a l l num ber o f
r e c a p t u r e s , g r a y l i n g w e re g ro u p e d b y s e x o n ly f o r t h e s e e s t i m a t e s .
t o t a l p o p u l a t i o n e s t i m a t e b y t h e S c h n a b e l m ethod was 2 5 ,8 8 9 .
The
T h is was
o n ly 5 .2 p e r c e n t h i g h e r t h a n t h e t o t a l P e t e r s o n e s t i m a t e , b u t t h e con­
f id e n c e i n t e r v a l s w e re f o u r tim e s a s g r e a t (T a b le 6 ) .
A ls o , S chnabel
e s t i m a t e s f o r t h e a d u l t m ale and fe m a le p o p u l a t i o n W ere 4 7 .5 p e r c e n t
h i g h e r an d 1 8 .1 p e r c e n t l o w e r , r e s p e c t i v e l y , th a n c o m p a ra b le P e t e r s o n
T a b le 5.- C a tc h s t a t i s t i c s (1971) f o r a d u l t g r a y l i n g w i t h P e t e r s o n p o p u l a t i o n e s t i m a t e s ,.
__________ . c o n f id e n c e i n t e r v a l s ( C l ) , and s t a n d i n g c ro p f o r e a c h s e x a n d s i z e g r o u p ,._____
T o ta l
C a p tu re
T o ta l
R e c a p tu r e
E s tim a te d
Num bers
(C l)
T o ta l
W e ig h t
kg
S ta n d in g
. C ro p .
k g /h a
264
6 ,4 2 2
( 5 ,8 1 0 - 7 ,0 3 4 )
6 5 5 .0
1 6 .0
609
299
7 ,1 6 1
( 6 ,5 7 3 - 7 ,7 4 9 )
895.1
2 1 .9
559
49
22
1 ,2 1 5
(8 5 1 -1 ,5 7 9 )
2 0 9 .0
5 .1
9
6 ,6 7 4
1 ,3 8 6
600
1 ,7 7 7 .8
43.5
2 4 .0 - 2 5 .9
Cf
219
151
28
1 ,1 4 8
(7 7 1 -1 ,5 2 5 )
1 1 1 .1
2 .7
2 6 . 0- 2 7 . 9
Cf
1 ,2 4 2
726
179
5 ,0 1 6
(4 ,3 6 9 -5 ,6 6 3 ).
5 9 7 .7
14.6
2 8 .0 - 2 9 .9
Cf
1,0.34
282
106
2 ,7 3 5
( 2 ,3 2 0 - 3 ,1 5 0 )
419.0
1 0 .3
3 0 .0 - 3 5 .9
Cf
195
30
18
318
(2 3 0 -4 0 6 )
6 9 .7
1 .7
T o ta l
Cf
2 ,6 9 0
1 ,1 8 9
331
9 ,2 1 7
( 8 ,3 5 6 - 1 0 ,0 7 8 )
1 ,1 9 7 .5
2 9 .3
9 ,3 6 4
2 ,5 7 5
931.
2 4 ,2 1 4
( 2 2 ,9 4 6 -2 5 ,4 7 8 )
2 ,9 7 5 .3
7 2 .8
59
15
2,540
669
5
3 ,5 2 2
2 8 .0 - 3 3 .9
9
T o ta l
2 2 . 0- 2 3 . 9
$
2 4 .0 - 2 5 .9
$
2 6 .0 - 2 7 .9
P o o le d T o t a l
53 '
1 4 ,9 9 7
( 1 4 ,0 6 9 -1 5 ,9 2 5 )
Ln
199
(1 1 6 -2 8 2 )
O
S ex
M arked
at
L a rg e
H
CO
S iz e
Group
cm
T a b le 6 . A summary o f a d u l t •g r a y l i n g c a t c h s t a t i s t i c s w i t h P e t e r s o n an d S c h n a b e l p o p u l a t i o n ■
______ e s t i m a t e s a n d c o n f id e n c e i n t e r v a l s (C l) f o r t h e m ale', f e m a le , a n d t o t a l p o p u l a t i o n .
P o p u la tio n
E s t im a t e d
Type
E s t im a t e
T o ta l
C a p tu re
M arked
at •
L a rg e
P e te rs o n
1 ,1 8 9
2 ,6 9 0 *
331
9 ,2 1 7
(8 ,3 5 6 -1 0 ,0 7 8 )
Schnabel
1 ,2 3 3
1 ,2 2 9 * *
47
1 3 ,6 0 0
(1 0 ,1 7 7 -2 0 ,4 9 3 )
P e te rs o n ■
1 ,3 8 6
6 ,6 7 4 *
600
1 4 ,9 9 7
(1 4 ,0 6 9 -1 5 ,9 2 5 )
Schnabel
1 ,4 5 0
1 ,2 8 9 * *
72
1 2 ,2 8 9
( 9 ,5 6 9 -1 6 ,8 8 6 )
P e te rs o n
2 ,5 7 5
9 ,3 6 4 *
931
2 4 ,2 1 4
(22 ,9 4 6 -2 5 ,4 7 8 )
Schnabel
2 ,683
2>418**
119
2 5 ,8 8 9
(2 1 ,3 3 6 -3 1 ,5 9 6 )
T o ta l
R e c a p tu r e ■
A d u lt m ale
A d u l t ■fe m a le
T o ta l a d u lt ■
* F is h ;m arked in .s p a w n in g r u n .
* * F is h c a p t u r e d a n d m arked i n la k e ,.
E s tim a te d
Numbers
(Cl)
-2 1 -
e s tim a te s .
Due t o this h i g h e r p e r c e n t o f r e c a p t u r e s a n d t h e s m a l l e r
c o n f id e n c e i n t e r v a l s , t h e P e t e r s o n e s t i m a t e s a r e c o n s i d e r e d t h e m ost
a c c u ra te .
Age a n d G ro w th .
Age and g ro w th d a t a w e re o b t a i n e d fro m a n a l y s i s o f s c a l e s ta k e n
fro m 559 g r a y l i n g c o l l e c t e d d u r in g t h e s p a w n in g ru n o f 1971 an d 80 c o l ­
le c te d in tr a p n e ts
(T a b le 7 ) .
The a v e r a g e t o t a l l e n g t h o f a d u l t
f e m a le s a t t h e tim e o f c a p t u r e r a n g e d fro m 1 .4 cm s m a l l e r t h a n a d u l t
m a le s f o r a g e g r o u p .I I t o 3 .2 cm s m a l l e r f o r age g ro u p V I.
A verage
c a l c u l a t e d t o t a l l e n g t h o f f e m a le s a t a n n u lu s one w as 0 .9 cm s m a l l e r
t h a n m a le s a n d 3 .2 cm s m a l l e r a t a n n u lu s s i x .
A lth o u g h t h e r e w ere
e x c e p t i o n s , m a le s g e n e r a l l y grew f a s t e r t h a n fe m a le s i n e a c h y e a r o f
life .
O th e r a u t h o r s r e p o r t e d s i m i l a r d i f f e r e n c e s i n s i z e an d g ro w th
r a t e s b e tw e e n s e x e s
(Ward 1 9 5 1 , K ru se 1959) .
s e x u a l l y im m atu re g r a y l i n g show ed l i t t l e
Reed (1964) fo u n d t h a t
g ro w th d i f f e r e n c e s b e tw e e n
s e x e s i n A l a s k a , h o w e v e r , m a tu re m a le s grew f a s t e r t h a n f e m a l e s ..
The a v e r a g e g r o w t h .o f g r a y l i n g i n L ake Agnes was l e s s th a n t h e .
a v e r a g e r e p o r t e d f o r s i x l a k e s and tw o s tr e a m s i n M ontana ( P e t e r s 1964)
( F ig . 4 ) .
C om bined ag e a n d g ro w th d a t a o b t a i n e d fro m 353 f i s h i n
U pper Red Rock Lake a n d Red Rock C re e k
(N e lso n 1954) show ed t h e b e s t
r e p o r t e d g ro w th f o r g r a y l i n g in ,M o n ta n a ;
Brown (1943)
fo u n d t h e c a l ­
c u l a t e d s t a n d a r d l e n g t h i n c e n t i m e t e r s a t e a c h a n n u lu s f o r t e n g r a y l i n g
fro m L ake Agnes t o b e 1 1 .4 - 1 s t y e a r , 1 9 .3 - 2nd y e a r , 2 5 .0 - 3 rd y e a r .
T a b le 7 .
A v e ra g e
t o t a l le n g th
a t c a p tu re
C a l c u l a t e d l e n g t h a t e a c h .a n n u lu s
4
2
3
5
I
6
Number
I
I*
56
1 4 .2 '
1 0 .7
II
I*
24
23.7
1 1 .0
2 2 .6
Cf
16
2 6 .9
1 4 .4
2 5 .0
$
25
2 5 .5
9 .9
2 4 .2
Cf
84
2 8 .1
1 1 .5
2 2 .4
2 7 .0
9
99
26 =6
1 2 .1
2 2 .0
2 6 .3
Cf
113
2 7 .9
1 1 .6
2 0 .9
116
2 6 .4
8 .8
1 8 .9
25,0
2 3 .4
2 6 .2
Cf
57
2 9 .2
7 .3
1 7 .8
22.9
2 6 .1
28.6
9
41
2 7 .2
7 .8
1 7 .6
2 2 .1
2 5 .0
2 7 .2
Cf
5
3 1 .2
8 .9
1 8 .7
2 2 .9
2 6 .4
2 8 .8
3 1 .2
3
2 8 .0 :
8 .1
1 6 .0
2 1 .0
2 3 .8
2 6 .3
2 8 .0
1 0 .8
22 .6
2 5 .1
2 7 .1
2 8 ,6
3 1 .2
III
IV
9
V■
VI
9
i*
,
80
2 7 .6
Cf
275
CO
T o ta ls
’
d
Sex
I— i
Age
Group
A v e ra g e . c a l c u l a t e d t o t a l l e n g t h s i n c e n t i m e t e r s a t e a c h a n n u lu s f o r
g r a y l i n g c o l l e c t e d d u r in g 1971.
2 0 .9
9
284
9 .9
20.2
2 4 .3
2 5 .8
2 7 .1
2 8 .0
A ll
639
1 0 .3
2 0 .6
2 4 .7
2 6 .5
2 8 .0
3 0 .0
*Im m ature
■23-
RED ROCK LA K ES (N EL SO N 1954)
---- TWO MONT. STREAM S (PE T E R S 1964)
------- SIX MONT. LA K E S (PET ER S 1964)
-------- LA K E AGNES - 1971
AGE GROUP
F ig u re 4.
C o m p ariso n o f g ro w th r a t e s f o r g r a y l i n g i n M o n tan a.
-2 4 -
2 7 .6 - 4 th y e a r , an d 2 7 .9 - 5 th y e a r .
I n t h e s o u t h e r n p o r t i o n o f t h e i r r a n g e , g r a y l i n g u s u a l l y m a tu re
a t a g e I I I w i t h a few m a tu r in g a t ag e I I
1 9 5 4 ).
(K ru se 1 9 5 9 , Ward 1 9 5 1 , N e lso n
I n t h e 1971 s p a w n in g r u n , - t h e p e r c e n t o f fe m a le s i n e a c h age
g ro u p w e r e : 9 .5 - I I ,
3 8 .8 - I I I ,
3 8 .2 - IV , 1 2 .7 - V, an d 0 .8 - V I.
F o r m a le s t h e p e r c e n t s w e r e : 6 .3 - I I ,
a n d 1 .4 - V I .
3 1 .1 - I I I , 4 1 .8 - IV , 1 9 .4 - V ,
The lo w e r p e r c e n t o f m a le s t h a n fe m a le s i n ag e g ro u p s I I
a n d I I I may h a v e b e e n t h e r e s u l t o f t h e a n t a g o n i s t i c b e h a v i o r b e tw e e n
m a le s d e t e r r i n g s m a l l e r a n d p o s s i b l y y o u n g e r .o n e s from e n t e r i n g t h e
in le t.
W o jc ik
(1955) r e p o r t e d t h a t g r a y l i n g d i d n o t r e a c h s e x u a l
m a t u r i t y i n .A la s k a u n t i l 5 o r 6 y e a r s o l d .
G r a y li n g se ld o m l i v e l o n g e r t h a n 6 y e a r s i n l a k e s i n t h e s o u th e r n
p a r t o f t h e i r ran g e .
6 y e a rs o ld .
N e ls o n
The o l d e s t g r a y l i n g fo u n d by Brown (1943) was
(1954) fo u n d tw o g r a y l i n g i n t h e Red R o c k . la k e s
r e g i o n w h ic h w e re 6 y e a r s o l d , h o w e v e r, one g r a y l i n g fro m Low er Twin
Lake ( e l e v a t i o n 9 ,1 0 0 f t )
was a g e d a t 10 y e a r s o l d a n d f o u r a t 9 y e a r s .
O nly one m a le , 3 2 .2 cm l o n g , was ju d g e d t o b e 7 y e a r s o l d .f r o m Lake
A g n es.
B is h o p
(1971) fo u n d g r a y l i n g up t o 11 y e a r s o l d i n P r o v id e n c e
C r e e k , C a n a d a , and R eed (1964) fo u n d g r a y l i n g up t o 8 y e a r s o l d i n "
A la s k a .
A sa m p le o f 40 f i n g e r l i n g s c o l l e c t e d on S e p te m b e r 2 5 , 1 9 7 0 ,
a v e r a g e d 7 .7 cm i n l e n g t h a n d r a n g e d fro m 6 .4 t o 8 . 7 .
A sa m p le o f
18 c o l l e c t e d on A u g u st 3 0 , 1 9 7 1 , a v e ra g e d 3 .8 cm i n l e n g t h an d ra n g e d
fro m 2 .7 t o 4 .7 .
-2 5 -
F e c u n d ity
Eggs w e re t a k e n fro m 27 g r a y l i n g p r i o r t o and d u r i n g t h e 1 9 7 1 '
sp a w n in g r u n .
The num ber o f e g g s p e r fe m a le i n c r e a s e d w i t h l e n g t h ,
r a n g i n g fro m 799 e g g s ■f o r a . 2 2 .0 cm f i s h t o 4 ,3 4 6 e g g s f o r a 3 0 .5 cm
fis h
(T a b le 8 ) .
The a v e r a g e num ber o f e g g s p e r f i s h f o r t h e e n t i r e
sa m p le was 1 ,7 5 0 o r 1 2 .6 p e r .g r a m o f f i s h
(356 p e r o u n c e ) . . Brown
(1938) fo u n d t h r e e l a r g e f e m a le s i n G eo rg eto w n L a k e , M o n ta n a , w h ich
a v e r a g e d 2 p o u n d s i n w e ig h t and c o n t a i n e d 1 2 ,9 4 6 , 1 2 ,4 6 2 , and 8 ,1 3 5
e g g s ,.re s p e c tiv e ly .
T h is i s a p p r o x im a te ly 351 e g g s p e r o u n c e ..
Ward
(2951) . found.. 376 e g g s p e r o u n ce f o r g r a y l i n g in ,C a n a d a an d B ish o p
(1971). r e p o r t e d 3 1 0 .9 p e r o u n c e .
D u rin g b o t h y e a r s o f t h e s t u d y , a num ber o f fe m a le s w e re ta k e n
d u r i n g J u l y and A u g u s t w h ic h w e re a p p a r e n t l y eg g -b o u n d ,.
I n 1 9 7 1 , 49
e g g -b o u n d f e m a le s w e re c a p t u r e d i n t r a p s and c o m p ris e d 3 .5 p e r c e n t o f
t h e t o t a l fe m a le c a t c h .
The abdom ens o f t h e s e f i s h w e r e e x tr e m e ly
d is te n d e d , g iv in g th e f i s h a b lo a te d a p p e a ra n c e .
I n t e r n a l e x a m in a tio n
r e v e a l e d a w a te r y m ass o f e g g s , m o s t .o f w h ic h w ere c r u s h e d .
T h ese
f i s h w e re m ore f r a g i l e t h a n o t h e r g r a y l i n g a n d s u f f e r e d a h ig h
m o r t a l i t y t h r o u g h t r a p p i n g and h a n d l i n g .
-2 6 -
T a b le 8 . A v e ra g e num ber o f e g g s p e r fe m a le by s i z e g ro u p s f o r 27
____________ g r a y l i n g t a k e n i n 1 9 71.
_____________ ._________________ ’
S iz e
In te rv a l
(cm)
Number
of
F is h
A v e ra g e
S iz e
(cm)
A v e ra g e ■ Mean #
W e ig h t
o f Eggs
p e r F is h •
(gram s)
Range
2 2 .0 - 2 2 .9
■3 •
2 2 .4
89
916
2 3 .0 - 2 3 .9
4
. 2 3 .7
105
1 ,5 5 2
935 - 2 ,8 1 2 ■
2 4 .0 - 2 4 .9
6
2 4 .4
122 •
1 ,3 4 7
869 - 1 ,9 8 2
2 5 .0 - 2 5 .9
4
2 5 .3
126
1 ,7 4 3
1 ,0 9 6 - 2 ,1 1 0
2 6 .0 - 2 6 .9
4
2 6 .4
148
1 ,8 0 5
1 ,4 2 7 - 2 ,1 5 2
2 7 ,0 - 2 7 .9
3 ■
2 7 .3
187
2,403■
1 ,7 7 0 - 3 ,3 4 5
2 9 .0 - 3 1 .5
3
3 0 .3
230
2 ,9 9 4
1 ,8 6 4 - 4 ,3 4 6
2 5 .5
139
I , .750
A v e ra g e
799 - 1 ,1 3 4
-2 7 -
DISCUSSION
I n d i c a t i o n s o f p o p u l a t i o n • f l u c t u a t i o n s i n Lake A gnes b a s e d on
nu m b ers a n d s i z e o f f i s h i n t h e sp a w n in g r u n h a v e been, n o t e d d u r in g
s p a w n - ta k in g o p e r a t i o n s c o n d u c te d i n t h e p a s t , b u t few r e c o r d s w ere
k e p t (V ern C a m p b e ll, R o b e r t M i t c h e l l - p e r s o n a l c o m m u n ic a tio n ).
D u rin g
t h e s p a w n - ta k in g o p e r a t i o n s i n 1 9 6 0 , t h e t o t a l num ber o f g r a y l i n g
p a s s i n g t h r o u g h a f i x e d t r a p i n t h e p r im a r y i n l e t w a s •6 0 4 .
T h ese
r a n g e d i n l e n g t h fro m 1 0 .5 t o 1 6 .5 i n c h e s a n d a v e ra g e d a ro u n d 15 i n c h e s .
W e ig h ts r a n g e d 0 .8 t o 1 .8 p o u n d s .
I n 1 9 7 1 , 9 ,3 6 4 g r a y l i n g w e re c a p ­
t u r e d fro m t h e sp a w n in g r u n an d t h e s e r e p r e s e n t e d o n ly a p o r t i o n o f t h e .
to ta l.
T h e i r a v e r a g e s i z e was 2 6 .8 cm (10=5 in c h e s ) a n d w e ig h ts r a n g e d
fro m 64 g ( 0 .1 4 l b s )
t o 322 g ( 0 .7 1 l b s ) .
G r a y lin g fro m L ake Agnes
c u r r e n t l y show s lo w e r g ro w th th a n t h e a v e r a g e r e p o r t e d f o r m o s t ■
M ontana l a k e s a n d s t r e a m s .
w ith i t s
The m a r g i n a l n a t u r e o f t h e s p a w n in g s tr e a m
s h i f t i n g s a n d b o tto m and f r e q u e n t b a n k c a v e - i n s , and th e
v a r i a b l e am ount o f s tr e a m a v a i l a b l e t o sp a w n in g f i s h b e tw e e n y e a r s a r e
b e l i e v e d t o b e t h e m o st i m p o r t a n t f a c t o r s c o n t r i b u t i n g t o ■t h e p o p u l a t i o n
flu c tu a tio n s .
A t th e p r e s e n t tim e , th e g r a y lin g i n . t h i s
a b u n d a n t t o t h e p o i n t o f o v e rc r o w d in g a n d s t u n t i n g .
la k e a re
I f fe w e r f i s h o f
a l a r g e r s i z e a r e d e s i r e d , th e. i n l e t s tr e a m may b e p e r i o d i c a l l y b lo c k e d
o f f i n an a t t e m p t t o c u r t a i l t h e m a jo r p o r t i o n o f t h e s p a w n in g a c t i v ­
itie s .
LITERATURE CITED
A m e ric an P u b l i c H e a l th A s s o c i a t i o n ,
1965,'
e x a m in a tio n o f w a t e r an d w a s te w a t e r .
S ta n d a r d m eth o d s f o r th e
E'd. 1 2 , New Y o rk .
769 p . •
B i s h o p , F . G.
1971. O b s e r v a t i o n s on s p a w n in g h a b i t s an d f e c u n d i t y o f
th e A r c tic g r a y lin g . P ro g . F is h - C u lt.
3 3 (1 ):
1 2 -1 9 .
B row n, C. J . D.
1943. Age a n d g ro w th o f M ontana g r a y l i n g .
Mgmt. 7 ( 4 ) :
3 5 3 -3 6 4 .
J . W ild ! .■
_________________.
1 9 3 8 . O b s e r v a tio n s on t h e l i f e - h i s t o r y an d b r e e d i n g
■h a b i t s o f t h e M o n tan a g r a y l i n g .
C o p e i a , 1 9 3 8 (3 ) : 1 3 2 -1 3 6 .
F a b r i c i u s , E . , a n d K a r l- J a k o b G u s ta f s o n .
1 9 5 5 . O b s e r v a t i o n s on t h e
sp a w n in g b e h a v i o r o f t h e g r a y l i n g T h ym allu s th y m a ltu s ( L ) . I n s t .
Freshw .- R e s. D r o ttn in g h o lm . Rept . 3 6 : 7 5 -1 0 3 .
H o lto n , G. D.
1971. M o n tan a g r a y l i n g : t h e la d y o f t h e s t r e a m s .
F i s h a n d Game D e p ., M ontana O u td o o r s , 2 ( 5 ) :
1 8 -2 3 .
M ont.
K r u s e , T . E . 1 9 5 9 . G r a y li n g o f G rebe L a k e ; Y e llo w s to n e N a t i o n a l P a r k ,
Wyoming. U. S . F i s h W il d l. S e r v . , F is h .. B u l l . 1 4 9 :
3 0 7 -3 5 1 .
M ic h ig a n I n s t i t u t e f o r F i s h e r i e s R e s e a r c h .
1960. P o p u la tio n e s tim a te s by m ark an d r e c a p t u r e ( P e te r s o n M ethod) w i t h c o n f i d e n c e ; l i m i t s .
M ethods Memo N o. 1 8 : 1 - 6 .
N e ls o n , P . H. 1 9 5 4 . L i f e h i s t o r y a n d m anagem ent o f t h e A m erican
• g r a y l i n g (T h ym allu s s l g n i f e v t T l o o l o v ) i n M o n tan a. J . W ild l.
Mgmt. 1 8 ( 3 ) :
3 2 4 -3 4 2 .
P e t e r s , J . C.
1 9 6 4 . Age and g ro w th s t u d i e s and a n a l y s i s o f b o tto m
s a m p le s i n . c o n n e c t i o n w ith p o l l u t i o n s t u d i e s . D. J . C o m p le tio n
R e p o r t. P r o j e c t F - 2 3 - R - 6 . M ont. F i s h and Game D e p . 76 p .
R e e d , R.' J . 1 9 64. L i f e h i s t o r y an d m i g r a t i o n p a t t e r n s o f A r c t i c
g r a y l i n g T h ym allu s a r o t i c u s 3 ( P a l l u s ) , i n T anana R i v e r D ra in a g e
o f A la s k a . A la s k a D e p . o f F i s h an d G am e,' R e s . Rept . 2 , 30 p . ■
R i c k e r , W. E .
1958.. H andbook o f c o m p u ta tio n s f o r b i o l o g i c a l s t a t i s ­
t i c s o f f i s h p o p u l a t i o n s . F i s h . R e s . Bd. C a n a d a . B u l l e t i n 1 1 9 ,
300 p .
-2 9 -
V i n c e n t , R . E . 1 9 6 2 . B io g e o g r a p h i c a l and e c o l o g i c a l f a c t o r s co n ­
t r i b u t i n g to. t h e d e c l i n e o f A r c t i c g r a y l i n g , Thymatlus a p c tte u s
p a l l a s , i n M ic h ig a n and M o n ta n a . P h .D . T h e s is , U n iv . o f M ich.-,
169 p .
( U n p u b l is h e d ) .
W ard, J . C.. 1951.
The b i o l o g y . o f t h e A r c t i c g r a y l i n g i n t h e s o u t h e r n
A th a b a s k a d r a i n a g e . M. S. T h e s is , U n iv . o f A l b e r t a > 71 p .
( U n p u b lis h e d ) .
W o jc ik , F . J .
1 9 5 5 . L i f e h i s t o r y a n d m anagem ent o f t h e g r a y l i n g i n
i n t e r i o r A la s k a .' M. S. T h e s i s , U n iv . o f A la s k a , 54 p .
( U n p u b lis h e d ) .
MONTANA STATE UNIVERSITY LIBRARIES
762 100
75 O
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