'- k.“ 4- ‘ ‘

 

THE WHITEFISH, COREGONUS CLUPEAFCRNIS (HITCHILL), OF
NORTHERN LAKE MICHIGAN, WITH SPECIAL REFERENCE To ACE,
GROWTH, AND CERTAIN NCRPHCHETRIC CHARACTERS

By

Prentice Alvin Saraway

A THESIS
Submitted to the School of Graduate Studies of Michigan
State College of Agriculture and Applied Science
in partial fulfillment of the requirements
for the degree of
DOCTOR OF PHILOSOPHY

Department of Zoology
1951

THESiS

 

21/2 5/" ’

ACKNOWLEDGL‘LEN TS

Field work in collecting data from the commercial
fisheries was supported in part by aid from the Michigan
Agricultural Experiment Station.

I am greatly indebted to Dr. P.I. Tack, Professor
and Head of Department of Fisheries and Wildlife,
Michigan State College, for his careful guidance and
many helpful suggestions during the course of the study.
To various other members of the staff of Michigan State
College I am indebted for additional assistance.

The cooperation of the commercial fishermen of
northern Lake Michigan, especially the Big Bay de Noc

and Manistique areas, is greatly appreciated.

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CONTENTS

PAGE
IDITRODUCTION O O O O C C O O O C O O O O C O C O 1

MATERIALS . . . . . . . . . . . . . . . . . . . 4

AGE COMPOSITION AND LENGTH FREQUENCY

DISTRIBUTION OF THE COMMERCIAL CATCHBS . . . . . 15
St. Helena Island . . . . . . . . . . . . . l7
Gull Island . . . . . . . . . . . . . . . . 17
High Island . . . . . . . . . . . . . . . . 22
Big Bay de Noc . . . . . . . . . . . . . . 25
Garden Island . . . . . . . . . . . . . . . 25
South Fox Island . . . . . . . . . . . . . 35

Pt. Aux Barques . . . . . . . . . . . . . . 55

STRENGTH OF YEAR CLASSES . . . . . . . . . . . . 57

Big Bay de Noc - Pt. Detour -
Seul Choix Pt. Areas . . . . . . . . . . . 58

Gull Island - High Island - Big Bay
de Noe Collections of 1950 . . . . . . . . 44

CALCULATED GROWTH . . . . . . . . . . . . . . . 54

LENGTH WEIGHT RELATIONSHIP . . . . . . . . . . . 70
Big Bay de Noc . . . . . . . . . . . . . . 71
Gull Island . . . . . . . . . . . . . . . 78
High Island . . . . . . . . . . . . . . . 85

PARASITIZATION BY LAMPREY . . . . . . . . . . . 89

ANALYSES OF MORPHOMETRIC MEASUREMENTS

Age-group IV (1946 year class) .

Age-group III (1947 Year class)

Age-group V (1945 year class) .

Age—group VI (1944 year class) .

Age-group VII (1945 year

Comparison of Sexes .

S UTIE‘JIARY O O O O O O O I I

LITERATURE CITED . . . . .

APPENDIX . . . . . . . . .

class)

PAGE
. 97

100
113
120
123
126
131

132

136

140

rr ||[II ll.

 

LIST OF FIGURES

Big Bay de Noc Whitefish Frontispiece

PAGE

Figure Chart of northern Lake Michigan . . . 6

Scale of Whitefish . . . . . . . . 15

1.
Figure 2. Morphometric measurements . . . . . 10
Figure 3. i
4.

Figure Percentage representation of

the 1950 colledtions . . . . . . . 48

Figure 5. Percentage representation of
Big Bay de Noc collections . . . . 50

Figure 6. Calculated growth curves . . . . . 69

Figure 7. Regression of lengthaweight,
Big Bay de Noc Whitefish '. . . . . 75

Figure 8. Length-weight relationship of
Big Bay de Noc Whitefish . . . . . 77

Figure 9. Regression of lengthaweight,
Gull Island Whitefish . . . . . . . 80

Figure 10. Lengthaweight relationship of
Gull Island Whitefish . . . . . . . 82

Figure 11. Regression of lengthaweight,
High Island whitefish . . . . . . . 86

Figure 12. Length-weight relationship of
High Island Whitefish . . . . . . . 88

Figure 15. Whitefish showing lamprey scars . . 91

Figure 14. Variance of head length of
age-group IV Whitefish . . . . . . 108

Figure 15. Variance of head length of
age-group III Whitefish . . . . . 119

Figure 16. Variance of head length of
age-group V Whitefish . . . . . . 122

Figure 17. Variance of head length of
age—group VI Whitefish . . . . . . 125

Figure 18. Variance of head length of
age-group VII Whitefish . . . . . . 150

INTRODUCTION

The Whitefish, Coregonus clupeaformis (Hitchill),
is one of the important species of commercial prominence
in the Great Lakes region. Koelz (1929, 1931) presents
a general account of the natural history and distribution
of the coregonid fishes of this region and northeastern
America.

The outstanding catches of WhithiSh in Lake Huron
during 1948 (2,971,905 pounds), followed by the sudden
near collapse of this fishery in 1949 (550,000 pounds)
and further reduction to 104,252 pounds in 1950 (Michigan
Biennial Reports, Fish Division), very strongly suggests
the need for further information of this species relative
to strength of year classes making up the commercial
catches. Especially, it is imperative to know something
of the nature of the influence of those strongly repre—
sented year classes that may dominate the catches for a
relatively short time in a certain localized area. Little
is known, from the current sampling methods used, of the
existence or nature of local populations or stocks among
Whitefish or their influence upon the fisheries of a
particular locality. When a species of fish as the white—
fish, with distribution throughout Lake Michigan, is ex-
ploited over a large portion of this area, it is important

to know whether that species consists of several populations

each keeping to a limited area or uhether there is inter—
mingling between different areas.

The trend of this fishery in Lake Michigan has not
fluctuated so drastically as that of Lake Huron, in general,
in the recent years. However, within the period 1945-1950,
the Lake Michigan catches have increased from 1,526,255
pounds in 1945 to a peak of 4,262,678 pounds in 1948, and
declined to 2,095,202 pounds in 1950 (Nichigan Biennial
Reports, Fish Division).

Studies of age and growth of this species from many
of the larger lakes of northern and northeastern North
America are available in the literature, but none have
been presented for Lake Michigan as far as the writer
can ascertain. Associated with this study of growth and
age composition of the commercial catches of Whitefish
from northern Lake Michigan, the method of analysis of
variance is applied to several body porportion measurements
of fish from several Widely separated collecting areas
(Figure 1). The analyses of measurements are based upon
the age group of the fish examined. Mottley (1941) applies
the method of covariance to head-length measurements of
trout to illustrate significant difference between two
separate populations. His measurements are taken of fish
making up a random sample and belonging to all available
size groups. Hile (1955) uses the age of the fish (age-

groups and year class) as a basis for comparing several

morphometric measurements of lake herring, Leucichthyg

 

artedi (Le Sueur). However, the values of the means

are shown without statistical treatment.

MATERIALS

The specimens of vhitefish for this study were taken
directly from the commercial fishery. Field collections
vere made during 1948, 1949 and 1950 from the raters of
northern Lake Hichigan (Figure 1). Additional information
pertaining to dates of collection, locality of catch, type
of gear, body of water, and total number of fish making
up the individual samples is given in Table 1.

All fish were weighed and measured immediately upon
collecting. This was done either by working in the cabin
of the tug during the lifting of the nets or by vorking
on the deck while returning to port. Taking of data vas
continued upon arrival at the fish house, in most instances,
until packing of the catch for shipment was completed.
Length measurements were made with a conventional "measur-
ing" board by placing the fish on the board, the axis of
the body at right angles to, and the tip of the snout
just touching a raised and piece. The total length and
standard length were read by means of a millimeter scale
set into the measuring board along the midline. All
measurements were taken by the writer.

In the 1949 and 1950 collections body proportion
measurements (Figure 2) were taken of the fish upon arrival
of the boats at the fish house in order to eliminate
possible error due to boat movement. Body proportion measure-
ments were taken only from those catches of live fish from

pound nets. Usually body proportion measurements were begun

 

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Table l.-Samples of Lake Michigan Whitefish employed
for age-growth and morphometric studies

 

 

Dgte Locality Body of water Gear Fish
1948

July 5 Seul Choix Pt. Lake Michigan trap nets 102
Aug. 7 Pt. Detour Lake Michigan trap nets 159
Aug. 14 Pt. Detour Lake Michigan trap nets 156
1949

July 29 Gull Island Lake Michigan trap nets 19
Sept. 7 Pt. Aux Barques Lake Michigan trap nets 41
Sept. 8 Round Island Big Bay de Noc pound nets 51
Sept.10 Round Island Big Bay de Noc pound nets 9
Sept.12 Round Island Big Bay de Noc pound nets 2
Sept.15 Round Island Big Bay de Noc pound nets 205
Sept.15 Fairport Big Bay de Noc gill nets 59
Sept.16 Burnt Bluff Big Bay de Noc pound nets 26
Sept.16 Round Island Big Bay de Noc pound nets 68
Oct. 6 Round Island Big Bay de Noc pound nets 156
Oct. 10 Round Island Big Bay de Noc pound nets 107
Oct. 12 Round Island Big Bay de Noc pound nets 65
Oct. 15 Round Island Big Bay de Noc pound nets 66
Oct. 14 Garden Bluff Big Bay de Noc pound nets 67
Oct. 15 Isabella Big Bay de Noc gill nets 51
Oct. 28 Garden Island Lake Michigan pound nets 25
Oct. 28 S. Fox Island Lake Michigan gill nets 86
1950

Aug. 12 St. Helena Id. Lake Michigan pound nets 45
Aug. 14 High Island Lake Michigan pound nets 57
Aug. 16 Burnt Bluff Big Bay de Noc pound nets 20
Aug. 17 Gull Island Lake Michigan pound nets 71
Aug. 22 Gull Island Lake Michigan pound nets 95
Aug. 26 High Island Lake Michigan pound nets 117
Aug. 26 Gull Island Lake Michigan pound nets 80
Aug. 51 Gull Island Lake Michigan pound nets 54
Sept.12 Burnt Bluff Big Bay de Noc pound nets 117
Sept.15 Burnt Bluff Big Bay de Noc pound nets 44
Sept.15 Burnt Bluff Big Bay de Noc pound nets 585
Sept.16 Burnt Bluff Big Bay de Noc pound nets lOl

within two or three hours after the fish.were taken from
the nets and before being covered with ice for shipment.
Body proportion measurements were taken by the use of
needle point dividers or jaw type vernier calipers which
were read to the nearest millimeter (except measurements

of H, CPL, and CPD which were read to the nearest 0.1
millimeter). Figure 2 shows graphically the coded desig-
nation of some of the measurements that were taken. All
measurements were made in a straight line on the left side.
A description of body proportion measurements of the white-
fish, the actual points from which measurements were made,
and the symbols by which the measurements are designated

in the tables and in Figure 2 are given below.

Total length (TL). Measured from the junction of the pre-
maxillaries to the tip of the caudal fin with the lobes
squeezed together so as to give the maximum possible

measurement.

Standard length {8L}. Measured from the tip of the snout
(junction of the premaxillaries) to the end of the last

vertebra or structural base of the caudal rays.

gead length (H2, Measured from the Junction of the pre-

maxillaries to the extreme bony margin of the operculum,

not including the opercular membrane.

Snout to dorsal (SD). Measured from the tip of the snout

(Junction of the premaxillaries) to the base of the first

 

 

ray of the dorsal fin.

Snout to anal (SA). Measured from the tip of snout to
the base of the first ray of the anal fin.

Body depth (D). Greatest vertical depth of the body.

Dorsal-anal distance (DA). Measured from the origin
(anterior end of the base) of the dorsal fin to the

origin of the anal fin.

Ventraleanal distance (VA). Distance between origins of

the ventral and anal fins.

Depth of caudalgpeduncle (CPD). Measured least depth of

caudal peduncle.

Length of caudal_peduncle (CPL). The oblique distance
between the posterior end of the anal base and the end
of the vertebral column (structural base of the middle

caudal rays).

Dorsa13pectoral:distance (DP). Distance between origins

of dorsal and pectoral fins.

Pectoral-ventral digtance (PV). Distance between origins

of pectoral and ventral fins.

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Scale samples were taken from the area immediately
anterior to the dorsal fin just above the lateral line.
These samples are preserved in small envelopes showing
the catalogue number assigned to the fish and information
relative to length, weight, sex, locality of catch, and
other data. The scales were cleaned and mounted on slides
in a solution of glycerin and gelatin to which a few crystals
of phenol had been added for preservation. The scale read-
ing was done by projecting the image through a scale
projection apparatus similar to that used by Van Oosten,
et a1 (1954). The positions of the essential scale features
were marked on a strip of Manila tagboard. In order to
measure the radii of the annuli, the strip was placed along
the anterior radius of the scale image (x28 approximately)
and the position of the focus of the scale was marked.

Then, without moving the strip, the positions of the
various annuli and the anterior margin of the scale were
also marked along the edge of the tagboard. The tagboard
was coded with the assigned catalogue number of the fish,
as designated on the glass slide, and used subsequently
in computing the growth rates. Ages are expressed by
Roman numerals and indicate the number of annuli found on
the scales. Figure 5 shows a scale that exhibits six
annuli and is thus from a fish that was in its seventh
year. The marginal increment surrounding the last annulus
indicates that the major portion of the seventh year of
growth had been completed at the time of capture in October.

O

Figure 5. Scale of a Whitefish taken from southwest of
Round Island, Big Bay de Noc, October, 1949.

Female, standard length 458 mm. (T.L. 21.9 inches)
weight 5.65 pounds

(Six annuli are evident and the fish is assigned
to age-group VI)

 

 

14

Growth computations are based on the assumption that,
after completion of the first annulus, the scales grow at
a relatively constant ratio to fish growth. A direct
proportion nomograph, calibrated in metric units, as
described by Carlander and Smith (1944) was utilized for
rapid calculations of yearly growth from the scale measure-
ments. The value of "c" (see Appendix I), length of fish
when the scales first appear, is placed at 55—40 milli-
meters for the whitefish (Van Oosten 1929). For these
calculations the value of "c" is arbitrarily set at 40
millimeters. It is not the purpose of this study to
determine the exact length of the whitefish at the
time the scales are formed. However, for purposes of
general comparison of growth rates, it seems that the
small variation in the values obtained for the initial
years by using either 40 or 55 millimeters as the value
of "c" does not produce an alarming distortion from
the general trends of the growth rates as may be seen in

the section on calculated growth.

15
AGE COMPOSITION AND LENGTH FREQUENCY DISTRIBUTION OF THE
SAMPLES

The length-frequency distribution of the whitefish
of northern Lake Michigan in the collections of 1950 are
given in Tables 2 to 12. All fish were taken in August
or September by pound nets and represent the total
commercial catch for the date indicated. The samples are
arranged according to age groups and standard length
intervals of 10 millimeters. The midpoints of the intervals
of standard length (millimeters) are converted to total
lengths (inches) in each sample by means of factors
determined for each sample area (Tables 50 and 51). The
midpoints of the class intervals for all samples were
designated as follows: e.g., the midpoint of the class
interval of 540-549 used for purposes of calculating
total length in inches was arbitrarily taken as 545.

In the 1950 collections all samples were from the
same type of gear, set at a fixed point in each locality,
and were made within a period of five weeks. The samples
for each date are preserved in their original identity
rather than combining them on the basis of sample areas.
While the large number of tables is objectionable, never-
theless, the individual sample identity is retained to
facilitate statistical comparison of body proportion
measurements of individuals of several age-groups which
make up samples taken from the same area on closely

related dates. Further results of the statistical analyses

Table 2... Length-frequency distribution
of Lake Michigan whitefish

(St. Helena Island sample of August 12, 1950. The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

:
Standard Age group
length Total III ] Iv [ V [VI 1 v11 | III-VII
interval 1en the
(millimeters) (inc es) Year class
1 ..l£i§__12&41_l§4§"1§41:124&_
540-549 16.4 1 1
550-559 16.9 5 5
560-569 17.5 6 6
570-579 17.8 8 8
580-589 18.5 6 1 7
590-599 18.8 1 1
400-409 19.2 1 1 2
410-419 19.7 4 4
420-429 20-2 5 5
450-459 20-3 1 1
440-449 21.1 2 1 3
450-459 21.7 1 2 5
460-469 22.1
470-479 22.6
480-489 25.1
500-509 23.9
510-519 24.4 - l l
vera e sta ard length 572 422 451 - 510
mill meters
Average total length 17.7 20.0 21.4 - 24.2
(inches)
Total number of fish 26 12 4 0 l 45
Percentage of total 60.5 27.9 9.5 0 2.5 100.0
2 _._r :—

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

*Equivalent to midpoints of intervals of standard length

17

of several of these measurements may permit consolidation
of some of the samples.

ISL. Helena Island. One sample of August 12, 1950 is
available for this locality (Table 2). This small sample
represents the total catch of one pound net for that date.
Age-groups III and IV dominate the sample (88.4 percent).
Age-group V is represented by 9.5 percent and age—group VII
by 2.5 percent. The 1944 year class (VI group) is not
represented. The Big Bay de Noc samples of 1950 (Tables
9 to 12) also show a complete absence of this year class.
In Table 2 the length-frequency distributions of the
individuals on the basis of age groups and class intervals
of standard length are presented. As expected, the length
distributions and the averages of the age groups in the
sample show a progressive increase in length with each
increase in age. However, there is some overlapping of
the lengths of fish in the different age groups.

Q31; Island. Four collections made in August, 1950,
are presented in Tables 5 to 6. The youngest fish taken
belong to age-group III and the oldest to age-group XI.
Percentage representation of these age groups are combined
in Table 19 and presented in the section pertaining to
strength of year classes. There is extensive overlapping of
the lengths of fish in the different age groups in the Gull
Island samples. Several of the lO-millimeter intervals of
standard length contain representatives of as many as four

age groups. In general, the standard lengths show a pro-

Table 3 .. Length-frequency distribution
of Lake Iichigan whitefish

(Gull Island sample of August 17, 1950.

The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A e roup ‘
Standard.
length Total 111 | NT v 1 v1 Ivn IVIIILIX [III-Ix
interval len th*

(m 1 mm”) (1” °"‘) 1947 1946 1945 1944 1943 1942 1941 1947-1941
330-339 15.9 1 1
340-349 16.4 1 1
350-359 16.9 1 1
360-369 17.4 1 1
370-379 17.6 1 1
360-369 16.3 1 1
390-399 16.6 1 2
400-409 19.3 1 1 2
410-419 19.7 1 3 1 5
420-429 20.2 ' 1 2 3
430-439 20.7 2 1 3
440-449 21.2 5 2 1 6
450-459 21.5 2 3 1 1 1 6
460-469 22.0 2 2 1 1 6
470-479 22.4 5 4 1 10
460-469 22.9 6 6
490-499 23.4 2 3 1 6
500-509 23.7 1 1
510-519 24.2 1 1
520-529 24.7 3 3
566-569 26.5 1 1

Average standard length 350 407 444 474 469 452 481

(millimeters) A

Average 1:61:61 length 16.6 19.5 21.1 22.4 22.3 21.5 22.6

(inches)

Total number of fish 4 2 24 25 7 6 3 71

‘Percentage of total 5.6 2.8 33.8 35.2 9.9 8.5 4.2 100.0

 

*Equivalent to midpoints of intervals of standard length

 

Table ll...Length-frequeney distribution
of Lake Michigan Whitefish

(Gull Island sample of‘Lugust 22. 1950. The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Age group
5 116. rd
{2.3: W mlIvIv Inlmmnlu Ix 1x: [In-n
interval length‘. Year class
(“lumurd (”Che") 191*? 19% 19‘5 19th 1913 19112 19111 1940 1939 191+7-1939
3 3 9 15. 1 1
£339 16. 1 1 2
350-359 16.? 2 1 1 4
370-379 17.6 2 1 a
360-369 16.3 2 2
390-399 16.6 2 2
19.3 2 1 &
1410-1119 19.7 1 z
tea-kw? 20.2 5 i i 1 g
20.7
160-169 21.2 :32 3 § 3 13
21.
M9 22.3 2 3 1 7
“70-379 22.14 5 2 1 1 9
use-1169 22.3 1 3 1 5
l#904199 23. 1 1 2
500-509 2 .7 1 1
SIG-519 2 .2 2 2
220-223 2147 3 1 1+
2’01
533-539 25.6
550-559 26.1
560-5 26.5 1 1
570-579 27.0
630-639 29.6 1 1
«Average standard length 353 383 ”he ”69 973 ‘1’53 ”35 536 530
(millimeters)
Average total length 17.3 16.3 21.0 22.1 22.2 21.5 20.7 25.0 29.5
(inches)
rem umber or fish 10 11 26 24 12 5 1 1 1 93
Percentage of total 10.7 11.6 30.1 25.6 12.9 5.4 1.1 1.1 1.1 100.0

 

 

OIQuivalent to uddpoints of intervals of standard length

 

r4514» 5... Length-frequency distribution
of Lake Michigan whitefish

(Gull Island sample of August 26, 1950.

The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A e roup _m

81:23:? Total III 11v ] V [VI ivn TVIIII "1x” 1111-11!
igigrvgl (length! Year class

0' me "3) ”c es) 1947 1946 1945 1944 1943 1942 1941 1947-1941
350-359 16.9 2 2 4
360-369 17.4
370-379 17.6 1 2
360-369 16.3 2 2
390-399 16.6 1 1 4
400-409 19.3 2 1 1 4
410-419 19.7 2 1 1 5
420-429 20.2 2 1 2 5
430-439 20.7 3 2 1 6
440-449 21.2 2 2
450-459 21.5 5 1 1 2 9
460-469 22.0 1 2 1 1 5
470-479 22.4 3 1 1 1 6
480-489 22.9 1 6 7
490-499 23.4
500-509 23.7 2 2
510-519 24.2 2 1 1 4
520-529 24.7 1 1 2_
530-539 25.1
540-549 25.6 1 1

Average standard length 369 380 433 468 432 464 512
(millimeters)

Average total length 17.5 18.0 20.6 22.2 20.5 21.9 24.2'
(inches)

Total number of fish 4 4 23 19 6 6 4 70
Percentage of total . 5.7 5.7 32.9 27.2 11.4 11.4 5.7 100.04

=: ‘

 

 

 

*Equivalent to midpoints of intervals of standard length

Table 61.. Length-frequency distribution
of Lake Michigan whitefish

(Gull Island sample of August 31, 1950. The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A e roup
Standard J—l—L
length Total IV I V aL-!:V VII 1TVIII I IX 1 IV - IX
interval length* Year class
(“unmem”) (“we”) 1946 1945 1944 1943 1942 1941 1946-1941
350-359 16.9 1 1
360-369 17.4 1 1
370-379 17.8 1 1 2
380-389 18.3 1 1
390-399 18.8 ' l 1 2
400-409 19.3 . 1 1 2
410-419 19.7 4 l 5
420-429 20.2 4 3 1 8
430-439 20.7 2 1 3
440-449 21.2 1 1‘ 2
450-459 21.5 1 1
460-469 22.0 1 1
470-479 22.4
480-489 22.9
490-499 23.4 1 1
500-509 23.7 1 1
510-519 24.2 1 1
530-539 25.1.
540-549 25.6
550-559 26.1
560-569 26.5
570-579 27.0 2 2
Average standard length« 373 412 429 460 429 542
(millimeters)
Average total length 17.7 19.6 20.4 22.0 20.5 25.5
(inches) ‘ g
Total number or fish 4 ll 10 2 5 4 34
Percentage of total 11.8 32.3 29.4 5.9 8.8 11.8 100.0

 

 

 

 

 

 

 

 

 

 

 

*Equivalent to midpoints of intervals of standard length

22
gressive increase with increase in age. However, several
poorly represented age groups show observed lengths below
those of age groups one and even two years younger. Further
consideration is given to this relationship in the section
on calculated growth. Age-groups V, VI, and VII make up
the major portion of the samples. (There is extreme paucity
of old individuals belonging to age groups above VIII.

The oldest fish in the samples belong to the 1959 year
class (XI group). However, in the High Island collections
(Tables 7 and 8) one individual exhibits 15 annuli. The
data of Tables 3 to 6 suggest that the commercial fishery
exercises considerable fishing pressure on the younger age
groups as they reach legal size and enter.the fishery. The
wider range and the extensive overlapping of the lengths of
fish in some of the age groups are discussed further at
the end of this section.

Igigh Island. Length-frequency distribution of two
collections from this sample area are presented in Tables
7 and 8. As in the Gull Island samples, there exists
extensive overlapping of the lengths in the different
age groups. Statistical analyses of the standard lengths
and body proportion measurements are discussed in the
section on analysis of variances of these measurements.
The percentage composition of the samples is presented

in Table 21.

Table 7.- Le

th-frequency distribution of

Lake M chigan shitefish

(High Island sample of August 14, 1950. The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

Age rroup
Standard
length Total 111 j 17 I v [VI VII [171117 n In I 111-3! ,
interval length* Year class
1 t ”4”’ .

(5111 "e "8) “mm” 1947 1946 1945 1944 1943 1942 1941 1935 1947-1933
340-349 16.5 1 1
350-359 16.9 1 1
360-369 17.3 1 1
370-379‘ 17.8 1 1
$90-$99 18.8 2 1 1 4
400-409 19.2 2 2 1 5
410-419 19.7 2 _2 1 1 6
420-429 20.2 3 3
430-439 20.7 1 3 2 8
440-449 21.1 1 2 4 9
450-459 21.5 2 2
460.469 22.0 1 2 1‘ 4
470-479 22.4 1 2 1 4
480-489 22.9 2 1 3
490-499 23.4 1 1 2
500-509 23.8 3 1 4
510-519 24.2 1 1
630-639 29.9 1 1

Average standard length 353 412 428 464 446 429 . 460 634

(millimeters)

Average total length 16.8 19.6 20.2 21.9 21.1 20.4 21.8 29.6

(inches)

Total number of fish 2 7 15 21 6 4 1 1 57

Percentage of total 3.5 12.3 26.3 36.8 10.5 .7.0 1.8 1.8 100.0

 

 

 

 

 

 

 

 

 

 

 

*Equivalent to midpoints of intervals of standard length

Table 8... Length-frequency distribution
of lake flehigan whitefish

(Big: Island earple of August 1950.26. The sexes are ”combined)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

V ” “'_" _'.‘::=
Standard
length Total 1 111 111111? Iwnnnnl 1x I x I x -44
interval length‘ Year class
(millimeters) (inches) 198 19148 1914] 19116 19115 191.1,, 191,3 1912 19”! 19% 1959-190
190-199 9.3 ‘ 1 1
210-219 10.3 3 3
25...; a; \ 1 1
e 1 1
$269 12.3 1 1
270—279 13-1
260-269 1 . 3 3
299-299 1 .1 1 1
300- 14.6 3 u 7
310-319 15.1 1 1 _
32°32? 1'3 2 i g
353: 9 16:5 3 u 7 7
350-359 16.9 1 2 i 3
‘370-379 17.8 1 1 2 1
380-389 18.3 1 3 1 l 5
90- 99 18.6 1 2 3 \ 5
9 19.2 1 2 a : 6
1110-1119 19.7 2 2 , 1 s
h 9 2.0-7 1 2 2 1 J 6
9 21.1 2 h 2 1 I 2
21. 3 1 2
l160-95115").ng 22.3 1 2 3
11“IO-WIS 22.1: 1 3 2 1 7
W69 1- '3 2 1 1 1.
1490-1199 23. 2 1 1. 1*
soc-509 2 .6 2 1 3
510-519 2 .2 4
$20-$29 29.7 1 1
" 5 9 25.2
at 9 , 2507 1 1
Average standard length 210 2113 31m 380 1421 1152 1172 1‘51 1‘39 1193
(millimeters)
Average total meta 10.0 13.1 16.11 16.1 20.0 21.5 22.9 -21.}: 23.1 23.9
(inches)
Total water of £1.11 6 12 20 16 19 an 11 7 1 1 111
Per-co ”engage; of total 5.1 10." 17.1 13.7 16 2 29 5 9.1; 6,0 01—11...th 100.0

 

‘Iluivalent to man“. ate 0! intervals of standard length

 

 

25

Big Bay Qg Egg. Four collections were made in 1950
from this area. Data pertaining to the samples are presented
in Tables 9 to 12. Age groups II to XII are represented.
Percentage representation of the year classes and age groups
are shown in Table 18. There is less overlapping of the
lengths of fish in different age groups (Tables 10 and 12)
than in the Gull Island and High Island samples. The Big
Bay de Noc samples of September and October, 1949, (Tables
15 and 14) exhibit relationships very similar to the
collections of 1950. Collections were made in September
and October, 1949, while the samples of 1950 were taken
in September (except the small sample on August 16, 1950,
containing 20 fish). The observed lengths for each well
represented age group show very little difference in the
samples for the two collecting years. Further analysis
of the Big Bay de Noc samples is presented in the section
relative to calculated growth.

Garden Island. One sample of October 28, 1949 is
available for this locality (Table 15). The total catch
is represented by 25 fish. Age groups III to VI are
represented. The III group is represented by 20 percent,
IV group by 40 percent, V group by 52 percent, and VI
group by 8 percent. The observed lengths for the age
groups very closely approximate those of the Big Bay de

Noe samples.

Table 61.. Length-frequency distribution
of Big Bay de Noe Whitefish

(Burnt Bluff sample of August 16, 1950.

The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

St d d T t 1 Age rroup

an ar 0 a .

length 1ength* III I IV I v VI ‘lVII [VIII I III-VIII
interval Year class

(millimeters) (1n0hes) 1947 1946 1945 1944 1943 1942 1947-1942
360-369 17.4 1 1
370-379 17.9 4 4
380-389 18.4
390-399 18.8 1 1
400-409 19.3 1 1
410-419 19.8
420-429 20.3 2 2
430-439 20.7 3 3
440-449 21.2 3 1 1 4
450-459 21.5 i
460-469 22.0 1 I 1
480-489 22.9 2 2
490-499 23.4 1 1

Average standard length 374 434 445 - 486 492

(millimeters)

_ _l_.ll____.___ .1

Average total length 17.8 20.5 21.0 - 22.9 23.2

(inches)

Total number of fish 6 10 1 0 2 1 20

Percentage of total 30.0 50.0 5.0 0 10.0 5.0 100.0

 

 

 

 

 

 

 

 

 

*Equivalent to midpoints of intervals of standard length

 

£93 2350...? 32532 .2 33282 3 1.63.33.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

H" J
o.8H m. o o m. in Ha: o ~.m «.5 n.n~ H33 .3 63:8qu
mHH H . o o H 1H . R o m on 3 an no “cause Haves
. m.m~ . .. o.m~ ~.n~ :.n~ - :.H~ 08 SH H.333
nude." H30» swayed:
3m - .. ohm mm: mm: .. om: as man 2.83328.
. H333.” danced: ouduebd
H H 7mm. m
m .H . H . . «.mu mmmnnmmM
m m . him mum-own
w H a. Qua 9.9.on
- mH H :H win 8.968
m w ..n... 3.18:
mH H mH H mam $4.3:
3 H a. H H :12 2.1135
N N as... a:
H H m.Hm main:
~.H~ .
s N 1. we mg
m H z “now @118:
m. m H WMH ”quon
. . H ,
m H m u.uH mmmdmm
3H H nH méH mung
u. a. .HH deR
-5 mmnnomn
H H NSH mmndmn
uanuSmH uan man 93H Han «:3 nzmH .22 mHmH mamH FmH “.383 5.8»8HHHEV
I . guano .30» .598” figaoana
wmequmH—HQ; - u f u as HHS H: H» p H H309. 5mg:
_ _ _ Edam—$44 _ _ a. _ HHH H5336

 

 

 

33338 0.3 .38. one .Omma .NH heaven... .3 39.3. 93.8 «93an

H3333: 08 0c 9n wan no
33535.3 gouguunaudenl.0_ 0.23.9

 

 

»
”‘0'".

 

Table II”. Length-frequency distribution
of Big Bay de Noc Whitefish

(Burnt Bluff sample of September 13, 1950. The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

*Equivalent to midpoints of intervals of s

 

E ‘
. Age group
\Siandgid 'r t 1 III I Iv I v I VI [VII [III-v11
eng 0 a
interval length* Year class
(millimeters) (inches) 1947 1946 _1945 1943 1942 1947-1942
350-359 16.9 3 3
360-369 17.4 11 11
370-379 17.9 6 6
380-389 18.4 6 6
390-399 18.8 1 1
400-409 J 19.3 1 3 4
410-419 19.8
420-429 20.3 5-
430-439 20.7
440-449 21.2
7450-459 21.5
460-469 22.0 1 1
470-479 .22.4
480-489 22.9 2 2
490-499 23.4 1 1
500-509 23.8 2 ‘ 2
510-519 24.3
520-529 24.7 1 1
540-549 25.7 1 1
Average standard length
(millimeters) 372 417 - - 501
Average total length
(inches) 17.8 19.9 - - 23.7
Total number of fish 28 8 0 0 8 44
Percentage of total 63.6 18.2 0 0 18.2 100.0

tandard length

 

Table '2. -Length-frequency distribution
of Big Bay de Noe whitefish

(Burnt Bluff sample of September 16, 1950.

 

 

The sexes are combined)

 

 

 

 

 

 

 

 

 

Standard A 9 J’°“P
length Total 11 Jill! I IV v I v1 | v11 | v111|11-v111
interval length
(millimeters) (inches) Year class.
1948 1947 1946 1945 1944g 1943 1942 1948-1842
300-309 14.8 1 1
310-319 15.3 1 1
320-329 15.8
330-339 16.2 1
340-349 16.7
360-369 17.4 6 6
370-379 17.9 24 24
380-389 18.4 19 4 23
390-399 18.8 8 1 9
400-409 19.3 7 8
410-419 19.8 3 3
420-429 20.3 1 1
430-439 20.7 3 3
440-449 21.2 2 1 3
450-459 21.5 1 1 2
460-469 22.0 1 1
470-479 22.4
480-489 22.9 1 1
490-499 23.4 1 3
500-509 23.8 1 1
510-519 24.3 2 3
520-529 24.7 1 1
530-539 25.2 1 1
Averaggestandard length
(mill ters) 309 376 411 447 - 501 508
Average total length
(inches) 14.9 18.0 19.5 21.0 - 23.7 24.1
Total number of fish 2 83 22 2 O 7 4 100
Percentage of total 2.0 63.0 22.0 2.0 (J 7.0 4.0 100.0

 

 

 

 

 

 

 

*Equivalent to midpoints of intervals of standard length

 

 

 

 

5135. IPPV. .i a?" n. . . .vW

m1. 13 rimgth-trequemq distribution of Big say do you mun-h

(he maples taken during October, 19349. are combined)

 

 

 

 

 

 

 

 

 

 

8length 11 Age group
Total m n v n m m: n
interval lung“). . yam- 012188 Total
millimeters) (inches) 19111 19116 1914; 1% 123 1213 1931 1
:4 3‘ 1-_C__L£_L_8_L_H_L
280-289 13.8 1 LLLL 1
290-293 111.3
300-309 111.7 2 2
310-319 15.2 2 2
£2223 12" a 1 s
.2 1 1
333.6% 16.7 1 f
350-359 16. s 3
360'369 170 7 7
$70-$79 17. 8 3
380-389 18. 2 2
90- 9 13.8 6 1 2 9
1 .3 1 2
1410-319 19.8 5 3 1 3
320-329 20.3 1 3 1 2 7
W9 20.8 3 3 I: 1 11
9 21-2 3 5 3 11
‘60-‘69 21.5 2 1 m 9 22
W69 22.0 1 20 11 32
“70-1179 22.5 9 15 an
had-M9 22.2 13 15 21;
”90-399 23. 8 6 1 15
soc-.509 .8 3 u 7
$10-$19 .3 1 1 2
gee-gag 35‘; 1 1
£253 32';
560-569 26.6 1 1
570-579 27.1
580-589 27.6 -
590-599 28.0 2 2
verege standard length
millimeters) u 312 330 1123 - 1170 .. - -
1' - 1 ”31 ‘456 1‘73 ”90 550 595
verage total length
inches) x 15.1 7.7 20.2 - 22.130 - - -
r - 19.1 20.!» 21.5 22. 23.0 25.9 28.2
htel mle
ma length 312 372 1125 1156 1171 1190 550 595
1.11m (inches) 15.1 17.8 20.2 21.5 22.3 23.0 25.9 28.2
tel under of fish 8 37 28 l 1‘31 1 2 2 23
ereentage or total 3.611 16.82 12.73 .95 9.09 J15 .91 .91 100.0

 

 

 

 

 

 

 

 

 

 

‘huivelent to midpoints of intervals of standard length ,

 

Table I4.-Lengtb-trequenqr distribution of Big 31v de the whitcfinh

(5510 00.1351“ taken during Septerber. 1939, are combined)

 

 

 

 

 

 

 

 

Standard Age group
hug“, Total in [ :17 TV“ Tn” I 711”:leng lxm
interval 19357;}, Year claw Total
(nillinetere) (inches) 19116 19115 1910 19113 1992 190 19110 1939 1936
$833 12" 2 u
3 1 . 1 16
360-369 17. 32 32
ӣ333 J13.8 11 u 15
. 7 5 12
Izen-£09 19.3 2 8 10
Inc-M9 19.8 1 19 2 22
11204129 20.3 17 3 20
W 20.8 E 13 20
21.2 23 29
use-use 21.5 3 3s 2 11"
“0.1169 22.0 1 1 32 3’:
33383 8:5 . a: a 33
“90-999 23. 1a 1 :3
500-509 3.8 2 1 7
$10-51, e3 2 2
520-529 20.7 1 1
23:23 25.2 1 1
5 559 2561’ i 1 2
522-669 26: 1 1
570-579 27.1
580-589 27.
250-299 28.0
28.5
610-619 29.0 1 1
Average tambrd length '
(mud...) 373 an: m 157 use 509 5:45 559 615
Average total length
(inches) 17.6 19.9 21.1 21.9 23.0 23.8 25.5 25.9 28.7
10:81 number or fieh 100 71 u 178 9 3 5 1 1 372
Percentage 0‘ total 509 19.1 1.1 u7e8 2.1} .8 1e} 03 e3 1m.0

 

 

 

 

 

 

 

 

 

 

 

‘MuiEent t0 nidpointe of intervele or etandard length

 

 

 

 

 

 

 

 

 

 

 

Table 15 .Le th-freguency distribution
of La e Mich gan‘whitefish

(Garden Island sample of October 28, 1949. The sexes are combined)

Standard A89 grouy
length Total
interval length! III I IV V VI
Igar class . Total

(millimeters) (inches) 1943 1945 T1 44 _ T3
380-389 18.3 1 1
390-399 18.8
400-409 19.3 2 2 4
410-419 19.7 2 2
420-429 20.2 2 2 l 5
430-439 20.7 2 2
440-449 21.2 2 2 4
450-459 21.4 1 l 2
460-489 21.8 1 1
470-479 22.3 2 2
480-489 22.8
490-499 23.2 1 1
510-519 24.1 1 1

vera e standard length a

mill meters) 408 429 448 500

verage total length

(inches) 19.4 20.3 21.2 23.7

otal number of fish 5 10 8 2 25

ercentage of total 20.0 40.0 32.0 8.0 100.0

 

 

 

 

 

 

 

*Equivalent to midpoints of intervals of standard length

33

South Fox Island. Data of one collection made on
October 28, 1949 are presented in Table 16. This sample
comprised the total catch from commercial gill nets (4 1/2-
5 inch mesh, stretched). Comparison of such a sample with
collections from pound nets must be undertaken with caution.
However, there exists wide ranges of lengths within the
same age group and extensive overlapping of the lengths
of fish belonging to several different age groups. A
similar relationship is exhibited in the Gull Island and
High Island samples.

23, Aux Barques. One trap net sample of September 7,
1949 is available for this area. The total catch consisted
of only 39 fish (Table 17). Age groups III to VIII are
represented. Age group V (1944 year class) dominates the
sample (41.0 percent). It is this same year class that
is so very poorly represented in the Big Bay de Noc collect-
ions of 1949 and 1950. Age group IV is represented by 20.5
percent, VI group by 18.0 percent, and III group, the fourth

most abundant group, by 12.8 percent.

M1. 16 .iangthpfrequenw distribution of m. mama-m manna

(South lo: Island senple of October 28, 191:9. The sexes are oonbined.)

 

 

 

 

 

 

 

 

Age map
33:33:“ Total 17 l V In J! 0:161:11] IL I J: 19.4 km
interval length.

(“111”“3') (1391") 191‘s 19% 19”} 19112 19141 19140 7 1939. 1938
390-399 18.8 1 1
NS 19.3 1 2 2 5
1110-1119 19.8 10 3 3 1. 17
1420-1129 20.2 8 13 1+ 25
1’60-‘89 20.? 1 11 3 15
Mao-M9 21.2 ’ 1 5 5 1 12
”50459 21.6 2 2 1;
W9 22.1 3 1 8
“70-379 22.6 1 1
#804189 23.0
W99 23.5 1 1 2

‘ffiiificfiifim length n32 9.51 1:19 )432 1132 1111+ L010 1191

323??“ lens“ 20.7 21.14 20.0 20.5 20.6 19.7 20.9 23.2

Total number of. fish 1 5 22 39 16 .1 1 .1 86

Percentage of total 1.2 5.8 25.5 115.3 8.6 1.2 ' 1.2 1.2 100.0

 

 

 

 

 

 

 

 

 

 

*Bnuivalent to mid-mints of intervals of standard length

 

Table 17.-Length-frequency distribution of Lake Michigan whitefish

(Pt. Au: Barqucs sample of September 7, 19119.

The sexes are combined)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Age group
simmugthd Tom :11 I xv I v I VI I 711 I vm
interval length. Year class Total
(millimeters) (inches) 19% 1 _19m; 1918 191.12 191a.
350-359 17.3
370-379 17.7 2 2
380-389 18.2 ’ 2 2
90- 99 18.7
19.2
1110-1119 19.6 1 1
320-1129 20% 3 1 n
20. l 1
03333 21.0 1 1 2
1150-959 21.9 ‘4 9
1560-1469 . 21.9 2 M 6
1170-1179 22.3 1 1 2
use-R89 22.8 2 2 h
‘190-999 23.3 1 1 2
500.509 3.6 1 1 1 3
5110-519 .1 1 1
San-529 211.6 2 2
33:5 9 25.0 1 1
9 25.5
550-559 26.0 1 1
Average standard length
(millimeters) 375 ‘35 ”59 500 505 5%
Average total length
(tr-311.8) 17.8 20.5 220° 23.3 2309 25.6
Total number of fish 5 8 l6 7 l 2 39
Percentage of total 12.82 20.51 ”1.03 17.95 2.56 5.13 100.0

 

'Iquivalent to midpoints of intervals of standard length

 

56

In the South Fox Island, Gull Island, and High Island
samples of Whitefish there exists wide ranges in lengths
within a majority of age groups represented. This is
accompanied by extensive overlapping of the lengths of
fish in several different age groups. In contrast, the
collections of Big Bay de Noe show less fluctuations and
reduced overlapping of the lengths in different age groups.
Preliminary statistical analyses of the standard lengths
and other body proportion measurements (see section on
analysis of variance of morphometric measurements) indi-
cate significant (1 percent level) differences between
the same age groups from some of the different sample
areas. A feasible explanation of the factors responsible
for these conditions is beyond the range of the present

paper.

57
AGE COMPOSITION AND STRENGTH OF YEAR CLASSES

A study of the relative abundance of the various age
groups and, at the same time, the consideration of the
relative abundance of the different year classes should be
undertaken with special consideration. Such problems as
type of gear used, selective action of the gear, depth of
set, and season are immediately encountered. However,
for purposes of these comparisons, only samples collected
in pound nets set in very nearly the same locality each
year are utilized. Comparisons are made of those samples
taken during August, September, and October.

In View of existing limitations, however, the members
of a certain year class may appear so conspicuous or so
scarce at all of the ages at which that year class appears
over several years of collecting that it may be feasible
to designate the year class as "good" or "poor."

An analysis of the age composition of the collection of
the years 1948, 1949, and 1950 in this study suggests the
presence of certain year classes that can be termed
relatively poor and relatively good. In the Big Bay de
Noc area the year class of 1945 as the age-group V of

1948 made up over 80 percent of that year's collection,
and 2 years later as the VII group it was still relatively
abundant, compriSing approximately 28 percent of the
combined collections in 1950 (Figure 5, Table 20). In
contrast, the year class of 1944 as the IV group of 1948

was represented by 6.5 percent, as the V group of 1949

58
made up only 0.4 percent, and as the VI group in 1950 was
not represented in the total catch samples (Figure 5).
Bingay de Noc - Pt. Detourg- Seplgghoix Pt. areas. In the
Seul Choix Pt. collection (Table 20) age-groups III and IV
(year classes of 1945 and 1944 respectively) account for
approximately 85 percent of the sample while the V group
(1943) forms 12 percent. This sample represents the total
catch of three trap nets for a period of 3 days and 2 nights.

Two samples were taken off Pt. Detour August 7 and
August 14, 1948. Since they represent total catches for
four trap nets for the dates indicated and the percentage
composition of the original samples were very similar
(Table 20), the data are combined. The V group (1945)
dominates markedly, forming over 80 percent of the catch
in each sample. Age-group IV (1944) is represented by
6.5 percent, and III group and VI group by 2.5 percent
each. The other age groups represented are II, VII, and
VIII, with none contributing greatly to the sample.

Samples taken in Big Bay de Noc during October, 1949,
are combined; however, only those collections considered
representative (those samples comprising the total catch)
are treated in such a manner. Preliminary inspection of
the data revealed that the age composition of represent-
ative samples taken during September and October, 1949,
show a very similar composition. Larger samples are

available for October and for this reason those data are

59
utilized. In the Big Bay de Noc collections of October,
1949, (Table 20) it is evident that the 1945 year class
(VI group) dominates the samples (64.2 percent of the total).
Age-group III is represented by 16.8 percent, and age-group
IV, the third most abundant group, by 12.7 percent of the
total. The study of the age composition of the Big Bay de
Noc - Pt. Detour collections indicates the presence of one
year class (1945) which may be considered very successful
and one year class (1944) which may be considered poor.

Of approximately 1,100 fish examined from Big Bay de Noc
during September and October, 1949, only 5 fish belonged

to the V group (1944). Further, in the Big Bay de Noc
collection of the following year (September, 1950) the

VI group (1944 year class) is not represented in the total
catches sampled. However, the 1943 year class (VII group)
continued to make up 27.8 percent of the total. A further
analysis of the Big Bay de Noc collections of September,
1950, (Table 18, Figure 4) indicates a definite trend in
the fishery toward a reduced representation by the 1945
year class within the period of one week. Table 18 exhibits
age composition of consecutive samples taken from the same
pound nets set off Burnt Bluff. In the collection of
September 12, 1950, the VII group (1945) is represented by
49.1 percent of the total. In the sample of September 15,
1950, the VII group is represented by 18.2 percent; however,
the catch of September 16, 1950, indicates that the VII

group made up only 7.0 percent of the total catch. A11

40

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samples for this period comprise the total catch for the
date indicated. Although the sample of September 15,1950,
may be considered small, the trend is definitely exhibited.
Further, an analysis of age composition of a sample of 783
fish (not included in this study) taken September 15, 1950,
from the same nets off Burnt Bluff presents representation
of the year classes in percentage composition very nearly
that of the September 16, 1950, collection. Accompanying
this rapid decline in the representation by the 1943 year
class, there was a marked increase of the IV group and,
especially, the III group (1947 year class) (Table 18).
This situation was evident during the actual process of
lifting the nets, since considerable difficulty was en-
countered in separating those individuals estimated to be
of legal size (2 pounds) from those individuals of
slightly less weight. In addition, conversation with
several commercial fishermen in the Big Bay de Noc area
further substantiated the fact that the catches in early
September, 1950, consisted of more than half of "jumbo"
Whitefish, weighing 4 pounds or over, while that size of
fish were poorly represented in the catches of late September,
1950. At the same time there appeared in the nets a marked
increase in the number of individuals slightly less than 2
pounds in weight. This is in agreement with data presented

in Table 18.

43

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. 44

From Figure 5, which exhibits graphically the
percentage representation of the different year classes,
the dominating influence of the very strong 1943 year
class may be seen. Also, the combined collections of
1950 show a bimodal relationship in that the III group
(1947) and the VII group (1943) are abundantly represented,
while the V group (1945) and the VI group (1944) are
very poorly represented. The collections of October,
1949, also indicate a bimodal relationship; however,
the VI group (1945) dominates the catch, while the
III group and the IV group are represented in next order
of abundance. Again, the 1944 year class is very poorly

represented.

Gull Island-High Island-Bingay de Noc collections of 1950.
Percentage representation of the different year classes
in the 1950 collections are shown in Figure 4. The Gull
Island collections (Table 19) represent total catches
for the dates indicated. Since these samples show close
similarity and are from the same pound nets, they are
combined for comparison with the High Island and Big Bay
de Noc collections.

In the Gull Island samples age—groups III (1947) to
XI (1959) are represented. Age-group V (1945) is slightly
more numerous (32.1 percent of the total) than age-group
VI, which is represented by 29.1 percent, and age-group
VII, the third most abundant group, is represented by

 

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46

10.8 percent. Absence of the I and II groups may be con-
sidered largely due to the selectivity of the gear. However,
Hart (1950) suggests that, at certain times, the larger
forms of Whitefish frequent water of less depth than the
smaller forms. Groups I and II are represented in the High
Island collection of August 14, 1950, but are not represent-
ed from the same nets in the collection of August 26, 1950.
In the former collection, a special effort was made to
collect all small Whitefish that were schooling in the "pot"
of the pound net with the larger fish. Usually these small
fish, if brought out of the water during the process of
lifting the nets, are immediately separated from the com-
mercial catch because of their sublegal size and returned
to the water. For this reason, representation of I group
and II group in the High Island collection is considered
atypical of a catch selected for commercial markets. In
collections of this study, in most instances, the III
group represents the youngest fish in the catch. Usually
these individuals were retained in the catch because their
weights were estimated to be approximately 2 pounds.

High_I§land samples. As mentioned above, the occur-
rence of the I and II groups in gear designed to select
legal commercial catch is considered irregular. In final
analysis of the samples these two groups are not considered.
It may be seen from Table 21 and Figure 4 that age-groups

IV, V, VI, and VII are well represented in the catch. In

47

Figure 4. Percentage representation of the different
year classes in the 1950 Whitefish collections
from the three principal sample areas.

 

 

PERCENTAGE

 

__BIG BAY DE NOC
..-..-H|GH ISLAND
_.._ GULL ISLAND

 

VI VII VIII IX
AGE GROUP

 

49

Figure 5. Percentage representation of the different
age groups taken in the Big Bay de Noc - Pt. Detour
collections for the years indicated.
Pt. Detour, (1948); Big Bay de Noc, ----- (1949);

Big Bay de Noe, __ .. _ (1950).

II

 

51

contrast to the Big Bay de Noc collections, year classes
1945 and 1944 (V group, VI group) make up slightly over

50 percent of the catch. Similar strengths of these same
year classes in the collections of Gull Island are evident.
In contrast, the Big Bay de Noc samples show almost a

complete absence of these year classes.

Pt. Aux Barques. -Unfortunately, 1949 collections

 

are not available for the Pt. Detour area. However,

one sample taken off Pt. Aux Barques, which is very

near that area (Figure l), on September 7, 1949, presents
age group composition quite unlike that indicated in

Big Bay de Noc samples for the 1949 collections (Table
20). In the Pt. Aux Barques sample age-group V (1944
year class) is represented by 41.0 percent and age-group
IV (1945 year class) by 20.5 percent. In contrast, the
V group (1944) is very poorly represented (0.4 percent)
in the Big Bay de Noe collections of the same year.

Fluctuations in abundance of year classes of fish
have long attracted the attention of fisheries biologists.
Especially, studies of the populations of marine fishes
have occupied prominent positions in research programs.
Dymond (1948) reviews some European studies of populations.
Studies of the age composition of herring stocks have
produced evidence that different year classes vary markedly

in their contributions to the stock of fish supporting the

52
fishery. At a meeting of the International Council for
the Exploration of the Sea (Rapp. Cons. Explor. Mer 65, 68)
the problems of fluctuations were given special emphasis.
In addition, Hjort (1914, 1926, 1930), Hodgson (1950, 1936),
Lea (1950), H. Thompson (1950), Sund (1956) and othe.s have
conducted studies on fluctuations of such species as herring,
cod, plaice, pilchard, hake and others. InveStigations for
an explanation of the causes of the wide differences in
the size of different year classes have shown that there
is no necessary connection between the number of eggs
produced in a particular spawning season and the number of
fry which survive. Poor spawning years have often been
good brood-years. Several suspected causes of fluctuation
in abundance are discussed by Dymond (1948).

The recent investigations of Burkenroad (1948),
Huntsman (1958), W.F. Thompson (1957), Thompson and Bell
(1954), Ricker (1940) and Walford (194s) pertain, largely,
to studies of abundance of various marine fishery animals
of economic value to industries in the United States and
Canada.

In review, Figure 4 shows diverse representation of
the different year classes in samples from three principal
collecting localities. The 1944 year class is not represented
in the Big Bay de Noc samples, yet this year class is well.
represented in the High Island and Gull Island samples.

Also, the 1945 year class is very poorly represented in the

55

Big Bay de Noc collections. In contrast, this year class
is well represented in the High Island samples and dominates
the Gull Island samples. Further, Figure 5 shows the
dominating influence of the very strong 1943 year class in
the Big Bay de Noc area through three fishing seasons. It
lies beyond the scope of this paper to indicate causes of
such fluctuations in abundance of different year classes of
Whitefish in northern Lake Michigan. It is evident that
the strength of a certain year class may vary markedly
between locations that are not too widely separated. Van
Oosten and Hile (1947) fail to indicate a correlation
between meterological-limnological conditions and fluc—
tuations in the strength of the year classes of Lake Erie
whitefish. In order to detect and evaluate any one of a
number of complex relationships, more extensive and
uniform methods of sampling and recording of data probably
will be devised.

54
CALCULATED GROWTH

The several SamPles of Lake Michigan Whitefish used

in these comparisons of calculated growth rates were taken
primarily from the sane'type of gear (pound nets) during
approximately the same months of the collecting years.
The data on length at capture and the calculated length
at the and of each year of life are presented in Tables
22 to 29. The grand averages of lengths and increments
in length are given at the bottom of each table.

Collections ggfliggg, The principal.sample areas of
the 1950 collections were located in Big Bay de N00 and
at Gull Island and High Island. All data are from Specimens
which made up the commercial catches from pound nets. A
comparison of the Gull Island (Table 23) and High Is1and
(Table 24) samples indicates very similar calculated growth
rates, especially among the age groups that are well
represented. Age-groups I and II are represented in the
High Island collection due to special effort to collect
these small individuals by means of a hand net. They
were not restrained by the gear and the 18 individuals
represent only a partial success of capture of individuals
of this size that were actually schooling with the larger
fish. Calculated lengths of these age groups (I,II) ex-
hibit values higher than those of the first two years of
life calculated from.the older fish in the samples. If

the I and II (Table 24) are removed from.the sample,

55

the annual increment in lengths for the first and second
year become very nearly the same as those calculated for
the Gull Island collections (Table 23). A comparison of
the values obtained for the calculated total lengths, based
on age-groups III through VIII, show close agreement of
High Island and Gull Island collections. Growth of the
whitefish is rapid during the first year and the length
increment added during the second year is more than half
that of the first year. The increment of length during
the third, fourth, and fifth years continues to decrease
but at a much slower rate. The higher age groups are
represented by fewer individuals and the calculated
lengths and observed lengths show considerable fluctuation.
The grand average calculated lengths at the end of each
year of life are plotted in Figure 6 for*the High Island,
Gull Island, and Big Bay de Noc samples of whitefish.

Data pertaining to the calculated lengths of the Big
Bay de Noc samples are presented in Table 25. The calculat-
ed lengths for each year of life through 8 years are slightly
higher than those of whitefish from.Gull Island and clearly
higher than those from High Island. The age groups above
VIII can not be accurately compared.because of the small
number of individuals representing the sample. The advantage
of the Big Bay de Noc whitefish over the Gull Island specimens
increases from 0.7 inches at the end of the first year of

life to 1.3 inches at the end of the eighth. The advantage

 

 

 

 

 

 

 

 

 

 

 

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59
of the Big Bay de Noc whitefish over the High Island speci-
mens increased from 0.7 inches at the end of the first year
to 2.3 inches at the end of the eighth year. The inter-
mediate position of the Gull Island whitefish is also
reflected in the length-weight relationship (Figure 10).

Data pertaining to calculated lengths of St. Helena
Island whitefish are presented in Table 22. Age-group III
forms over 50 percent of the sample. In general, the
calculated total lengths exceed those of the Big Bay de Noc
fish. ‘With the exception of the first year, calculated
values of total length for each year of life of the III
group very closely approach the values determined for
the Big Bay de Noc whitefish. The close agreement of
these two age groups from such widely separated localities
(Figure l) is discussed further in the section pertaining
to statistical analyses of measurements.

Collections.g§';ggg. Big Bay de Noc samples of
October 6-14 are combined in Table 26. The calculated
total lengths for the combined age groups very closely
approximates those of the 1950 collections of the same
locality (Figure 6). However, only general conclusions
can be made because of the pronounced differences in age
group composition of the samples of the two consecutive
years. The 1949 samples are heavily influenced by the
dominant year class of 1943. In the 1950 collections
the year classes of 1946 and 1947 dominate; a reduced

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8. .33 $.38 22.6 8.. cc 58 3n 5 .3338 53.39. .5 no case: a. 533 332:. mm .23.

 

62
group. Conditions favoring such a comparison of these two
collections are the similarity of gear and seasons of collect-
ing. Fish were taken in both years from.the same type of
gear (pound nets), operated by the same commercial fishermen,
and set very nearly in the same locality. The collections
of the first year were made October 6-14 and those of the
second year were made September 12-16.

The Big Bay de Noc collections of 1949 (Table 26) permit
analysis of several age groups on the basis of calculated
lengths, observed lengths, and observed weights of the sexes.
Age-group III is made up largely of males, IV group shows
increased representation by females, and in the VI group
very favorable comparison of males and females (141 fish)
may be made. The best represented age groups (IV and VI)
indicate that the females are slightly longer than the
males of the same age group (0.1 to 0.2 inches). The ob-
served weights of the females are distinctly higher than
those of the males. All VI group fish were sexually mature
and females of this age group averaged 0.45 pounds above
weights of the males. Since samples were taken in early
October, these fish showed increased development of the
gonads. Unfortunately, the scarcity of individuals belong-
ing to age—group V does not permit study of their sexual
maturity. Most of the males and females (percentage un-

determined) of IV group exhibited advanced development of

gonads but no collections are available immediately

65
following the spawning to verify actual conditions of these
organs. However, individuals of this age group (IV), for
all practical purposes, had completed their fifth year of
growth. Van Oosten (1959) states that in the Lake Huron
whitefish the males were sexually mature or reached sexual
maturity in the fifth year of life at a total length of 19.3
inches and a weight of 2.4 pounds. The length-weight values
of Big Bay de Noc fish agree very favorably with these values.
Age-group IV males (Table 26), nearing completion of their
fifth year of growth at this time, exhibit a total length
of 20.2 inches and a weight of 2.76 pounds. All VI group
fish (Table 26) were sexually mature. The females show
an advantage in total length of only 0.1 inch over males,
but are 0.45 pounds heavier. The calculated total lengths
at the end of each year of life are in close agreemert;
however, the females exhibit values at each year slightly

above those determined for the males.

The Pt. Aux Barques collection of September 7, 1949,
(Table 27) and the Garden Island sample of October 28, 1949,
(Table 28) are relatively small samples and permit only a
generalized comparison.with the Big Bay de Noc samples
(Table 26). In general, both samples exhibit calculated
lengths and increments of growth very closely related to
the Big Bay de Noc fish; however, age group composition
varies widely between the samples and such conclusions

should be regarded with caution.

64

The South Fox Island collection (Table 29) is the Only
gill net sample used in this study. Since it has been shown
by many fishery bioligists that gill nets are extremely
selective (see Hile, 1936, for review of literature), calcu-
lated values of total length and growth increments are
entered here only for purposes of general information
(Figure 6). The table of length—frequency distribution
arranged according to age (Table 16) exhibits extensive
overlapping of the lengths of fishes belonging to different

age groups.

 

 

 

 

 

 

 

 

 

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68

Figure 6. Calculated growth in length of the whitefish
in northern Lake Michigan based on total samples for
the areas and years indicated. The sexes are

combined.
Big Bay de Noc, (1950); Big Bay de Noe, ..... (1949);
High Island, ————— (1950); Gull Island, __ .. _ (1950);

South Fox Island, .... (1949).

 

IN MILLIMETERS

CALCULATED TOTAL LENGTH

 

 

 

 

 

7O
LENGTH-WEIGHT RELATIONSHIP

The data for this relationship are analyzed on
the basis of combined collections from three principal
sample areas: Big Bay de Noc, Gull Island, and High
Island. All fish were taken from pound nets in August
and September, 1950, with the exception of the Big Bay
de Noc collections of September, 1949. Length-weight
relationships were obtained from 254 fish taken off
Gull Island, 174 fish taken off High Island, and 848_
fish from Big Bay de Noc. The sexes are combined.

The individuals were placed in 10 millimeter length
groups and average lengths and weights obtained for
each group.

The lengthaweight data of the northern Lake Michigan
whitefish are fitted to the following formulae:

c (L)n

log W = log c + n log L

W

The values of log c and n are determined empirically.
Regression lines are calculated for the three sample
areas by methods presented by Snedecor (Sec. 6.10,

1946).

71

Big Bay d3 Egg. The formula expressing the length-
weight relationship was calculated from the means of 18
size groups (each containing 10 or more fish) between
540 and 519 millimeters in standard length. These means
are based on measurements from 848 fish. The values for
these and the regression line calculated from them are
plotted in Figure 7. Open circles indicate those groups
represented by less than 10 individuals. The correspond—
ence of the better represented groups to a straight line
is very close. The length-weight relationship for the
Big Bay de Noc whitefish of the 1949 collections may be

expressed by the formula:

log W = - 8.4271 + 5.2544 (log L)
where W = weight in kilograms
and L = standard length in millimeters.

Figures 8, lO, and 12 are presented for the principal
sample areas to permit rapid conversion between the
metric and English systems of measurement. Factors

used for converting standard length in millimeters to
total lengths in inches are presented in Tables 50 and
51. The values obtained for the Big Bay de Noc whitefish
are slightly higher than those given for the Lake Huron
whitefish (Van Oosten, 1959) and the Lake Erie whitefish
(Van Oosten and Hile, 1947). Factors yor the conversion
of total lengths in inches to standard lengths in

millimeters and for conversions between total and standard

72

 

 

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'74

Figure 7. Length-weight relationship of Big Bay de Noc
whitefish taken in September, 1949.

The regression line was calculated from the size grou 5

containing 10 or more fish (represented by black dots .

Size groups containing less than 10 fish are shown by
circles.

 

 

 

 

 

 

 

 

 

 

 

BIG BAY DE NOC

 

 

 

 

800

IN MILLIMETERS

 

-——_.—-— .

 

 

 

 

 

.

_

7 6 5 4 3 2
moZDOa 2. .5052,

 

STAN DAR D LE NGTH

 

'76

 

Figure 8. Length—weight relationship of Big Bay de Noc
whitefish.

 

I N POUNDS

WEIGHT

TOTAL LENGTH IN INCHES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  

 

 

 

 

4 8 I2 I6 20 24 28
I00 I ‘ l 4.5
9.0 f I
J I 4.0
I
3.0 4 , I i
3.5
I
7.0 I 1‘ Ti 0
I I o
I I 30
6.0
2.5
5.0 I
I
I 2.0
4.0
L5
3.0
LG
20
I0 05
' BIG BAY DE NOC
0 A . . . . I A
I00 2 3 4 5 6 700

STANDARD LENGTH IN MILLIMETERS

IN Kl LOGRAMS

WEIGHT

78

length without change in the unit of measurement are
computed for several samples but are not included in this
paper. However, preliminary results indicate that the
values agree very closely with those of the above authors.

Gull Island. The formula expressing the length-
weight relationship was calculated from the means of 17
size groups (each containing 5 or more fish) between 350
and 529 millimeters in standard length. The means are
based on measurements from 254 fish. The values of these
are plotted in Figure 9 along with the regression line
calculated from them.

The length weight relationship for the Gull Island
whitefish of the 1950 collections may be expressed by

the formula:

log W = - 7.7259 + 2.9886 (log L)
where W = length in kilograms

and L = standard length in millimeters.

'79

Figure 9. Length-weight relationship of Gull Island
whitefish. '

 

 

IN POUNDS

WEIGHT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I . r .— - .
OI r0, I
9 - I’t ‘
L I
8 I I
I. I
I
7 ’ ‘
a I , *
5 _ -
4 _.
3 _ __
2 a
GULL ISLAND
I . L . J . I L
200 5 6 7 800
STANDARD LENGTH IN MILLIMETERS

 

81

 

Figure 10. Length—weight relationship of Gull Island
whitefish.

IN POUNDS

WEIGHT

TOTAL LENGTH IN INCHES

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4 3 I2 I6 20 24
I0.0 2° __ 45
9.0 --
"44.0
8.0 —~-
H 3.5
7.0 .4-
-—H~—-—- ____ 30
0.0 ——— — -
—- 2.5
50 I
I
I 2.0
4.0
I
I I.5
3.0
I.0
2.0
|.0 0.5
" GULL ISLAND
0 I00 2 3 4 5 0 700

STANDARD LENGTH IN MILLIMETEPS

IN KI LOGRAMS

WEIGHT

85

High Island. The formula expressing the length-
weight relationship was calculated from the means of 14
size groups (each containing 5 or more fish) between
570 and 509 millimeters in standard length. These means
are based on measurements from 174 fish. The values for
these and the regression line calculated from them are
plotted in Figure 11.

The length-weight relationship for the High Island
Whitefish of the 1950 collections may be expressed by

the formula:

log W = .. 7. 2567 + 2.8166 (log L)
where W = weight in kilograms
and L = standard length in millimeters.

84

An inSpection of the formulae expressing the
regression line for length—weight relationship of fish
from the three principal sample areas indicates a distinct
advantage of the Big Bay de Noc whitefish over fish from
Gull and High Islands, especially at the higher lengths.
The length—weight relationship of fish from Gull Island
Show a very slight advantage over those taken off High
Island.

The weights of the northern Lake Michigan white-
fish increased to the following power of the lengths:
Big Bay de Noc, 5.2544; Gull Island, 2.9886; High
Island, 2.8166.

Comparative growth curves of fish from these three
sample areas, based on average calculated lengths at the

end of each year of life (Figure 6), exhibit a very

similar relationship.

85

 

Figure 11. Length—weight relationship of High Island
whitefish.

IN POUNDS

WEIGHT

 

 

 

 

 

 

 

 

HIGH
I

 

 

ISLAND
l . I

 

 

3

4

5

6 7800

STANDARD LENGTH IN 'MILLIMETERS

8‘7

Figure 12. Length—weight relationship of High Island
whitefish.

 

TOTAL LENGTH IN INCHES
4 8 I2 I5 20 24 28

 

9.0

 

 

 

 

8.0

 

7.0

 

 

9‘
O

 

 

 

 

IN POUNDS

go
0
IN Kl LOG RAMS

 

 

8

9
O
WEIGHT

 

WEIGHT

 

 

'u

 

3.0

 

 

2.0

 

 

 

L0 0.5

 

 

HIGH ISLAND

 

 

 

 

 

 

 

0 loo. 2 3 4 5 a 700

STANDARD LENGTH IN MILLIMETERS

s—

89
PARASITIZATI ON BY Lamar

The total collections of 1950 were examined for
evidence of scars suspected to be caused by lampreys .
(especially the sea lamprey, Petromyzon marinus). For
purposes of this study deeply injured areas (Figure 15,
A,B) were regarded to be the result of very recent
parasitization by the sea lamprey. In some instances
the lampreys were observed attached to the fish during
the lifting of the nets and, on rare occasions, remained
attached after the fish were removed from the nets.
These observations were made of fish making up the
actual commercial catch. It is beyond the scope of
this paper to estimate the p0pulation density of either
parasite or host, or to indicate degree of error in
recording incidence due to death and nonrecovery of
severely affected fish. Results of observations are
presented due to current interest in possible effect
of this form on the Great Lakes fishery.

Data relative to observations of scars shown by
individual fish making up catches of three principal
sample areas are presented in Tables 52 to 54. "New"
(fresh) scars were designated as deep bloody injuries,
piercing the skin and causing injury to the muscle
tissue (Figure 15, A). A further aid in identification
and classification of these damaged areas was the

common occurrence of "teeth" markings at the periphery

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31.

 

 
 

             

92
of the scar (Figure l5,B) caused by the horny circum-
oral teeth of the lamprey as compared to an injury
caused by mechanical means. "Old" (healed) scars
were designated as injured areas, devoid of scales,
that indicated recovery from previous injury by growth
of scar tissue. Deformities or tears in the skin that
obviously were the results of mechanical injuries were
not recorded.

The total fish observed and the number of fish
exhibiting old scars and new scars, by number and
percentage of total, are presented in Tables 52 to 54
for each collecting area. As a further interest the
injured fish were arranged on the basis of age groups.
The available data are considered insufficient to permit
a concise comparison of incidence of infection to relative
abundance of the age groups. Such inferences must be
approached with caution. However, age composition of
these samples on a percentage basis are presented in
Tables 18, 19, and 21. A comparison of the number of
individuals in each age group exhibiting new scars
follows very closely the rank order of the age groups
dominating the catch, with the exception of the younger
age groups (I, II, III). In addition, samples from
Big Bay de N00 for two successive years indicate that
scars recorded as healed scars in 1950 collections

(Table 54) exhibit their highest frequency in age-group

93

 

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94

 

 

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96
VII (1943 year class) which had been the dominant year
class in that area for the two previous years.

The younger age groups (I,II, and III), forming
their reSpective part of the samples presented in Tables
32 to 34 and examined at the same time, consisted of a
total of 178 fish which did not exhibit scars of any
type. Of a total of 94 fish belonging to age-group IV
(1946), only 4 fish exhibited fresh scars and 2 fish showed
healed scars. These data suggest that comparative enumer-
ations of incidence of lamprey (?) damage upon fish from
different collecting localities may be biased by age
composition of the respective samples. Especially, this
may be true among those samples in which the age groups
III and IV dominate the commercial catches. Royce (1949)
shows that the larger lake trout in Seneca Lake, N. Y.,
suffered more attacks and were more vulnerable to attack
by lamprey. However, his data are not correlated with
age, but are correlated with length and weight of the
fish parasitized.

The points of occurrence of the damaged areas were
recorded in each case. Seventy—five percent of the
scars occurred very near the origin or insertion of the
ventral fins as shown in Figure 13,A. Infrequently scars
appeared on the side of the body or on the ventral surface.
Only on rare occurrences were scars recorded from the

dorsal region.

97
ANALYSES OF MORPHOMETRIC MEASUREMENTS

Body proportion measurements, as designated in Figure
2, were taken of the 1950 collections. Summaries of six
of these measurements, based on age groups of the fish
examined, are presented. Studies of the remaining measure-
ments by means of analysis of variance and regression are
to be presented in a separate paper.

Various methods have been suggested and devised as
a tool for distinguishing separate pOpulations or stocks
of fish, especially marine forms. Dymond (1948) presents
an excellent review of the literature pertaining to
European investigations of populations. Body proportion
measurements, counts of fin-rays, scale counts and other
characters such as the number of vertebrae have been used
to distinguish p0pu1ations of fish. Godsil (1948) defines
the term "pOpulation" as a group of intermingling fish
inhabiting a restricted area and constituting a separate
and distinct unit, the fish of which may collectively be
distinguished and identified by minor morphological
characteristics. In his study of the Pacific tunes, an
assumption is made that distinct p0pulations do not
normally intermingle, with the corollary that differences
existing between populations are constant.

Body proportion measurements have been used by many

early workers to study the differences between local

98
populations. Results were expressed largely as ratios
and general limits were set up without statistical
evaluation of these measurements. However, many of
the recent investigations exhibit refined use of various
statistical methods as a tool for designating local
populations or stocks. Carp rearing techniques and the
means of defining local populations have been thoroughly
investigated by such workers as Eichler (1938), Kfihne
(1938), and Lechler (1938). Primarily, these authors
have used body proportion measurements and based their
conclusions upon means and standard deviations of these
measurements or ratios for the different populations.
Martin (1949) reviews the relative-growth method in the
interpretation of the environmental control of body form
in fishes. Relative-growth curves are given for some
twenty species.

Among the coregonid fish, ratios of various body
parts have been used to separate many of the species
and subspecies. Koelz (1929, 1931) reviews extensively
the coregonid fishes of northeastern America. Several
body proportion measurements and ratios of these measure—

ments are set up for the whitefish, Coregonus clupeaformis,

 

by Koelz (1929), but none are treated statistically.
Hile (1935, 1937) casts doubt as to the validity of this
method for determining subspecies of the lake herring,

Leucichthys artedi. His reports do not pertain to the

 

whitefish; however, he reviews some of the recent European

99

works relative to the genus Coreggnus.

 

Recent European investigations concerning coregonid
variations have demonstrated conclusively that, under the
influence of changed environment, these fish may undergo
extensive morphological modifications. Svardson (1948,
1949) presents results of ecological and Speciation studies

of the whitefish, Coregonus, in Sweeden. Twenty-two body

 

proportion measurements are utilized. Transplantations
from.one lake to another indicate that the morphological
characteristics of a single population are dependent largely
upon the nature of the local environment.

It is one of the purposes of this paper to apply the
method of analysis of variance to several body measurements.
The fish are compared on the basis of age groups as deter-
mined from the scales. Only fish belonging to the same

year class (year of hatching) are compared.

AGE GROUP IV (1946 YEAR CLASS)

Summaries of six body proportion measurements of
Whitefish from several localities are given in Table 35.
The values of the locality means and their standard errors
and the extremes of individual measurements are listed.
Standard errors are computed on the basis of the psoled
standard deviation as determined in the analysis of variance.

Body prOportion measurements of age-group IV fish
are used to illustrate methods used in this study. Methods
of testing the significance of two or more means by the
analysis of variance as described by Baten (1938) and
Snedecor (Chapter 10, 1946) are utilized. Summaries of data
pertaining to head lengths (H) of Whitefish from six samples
are presented in Table 36. Symbols are those used by
Snedecor (1946). Similar computations were made for all
measurements tested. Although a few age groups in some
samples are represented by a relatively small number of
fish, these samples were analyzed separately rather than
combining all collections for a particular locality.

Table 37 gives the analysis of variance for the
head length (H) of age—group IV (1947 year class) white—
fish of northern Lake Michigan. To determine whether
the results are significantly different we obtain the

value of F:

F : EEEgE£-YE£i§ESS_-- = -EL§§§§-__ = 15.89*%

Smaller variance 0.1789

lOl

 

 

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103

Table 37.-Ana1yeie of variance of head length (H) of age-group
Iv (19% year class) northern Lake Michigan whitefish

 

 

Source 01‘ Degrees of Sun or Standard
variation freedom squares Variance deviation
Total 98‘ 29-065
Between
samples 5 12.1L26 2.1;652"
Within
samples 93 16.639 0.1789 034230

 

”Highly significant

104
Referring to tables for distribution of F, we find the
F value for nl = 5 and n2 = 95 (n2 = 80 used) degrees of
freedom is approximately 8.35 at the 5 percent point and
3.25 at the 1 percent point. Since an F value of 13.89
is obtained, it may be concluded that the difference be-
tween at least two of the means of the samples is highly
significant, that is, that the chance of obtaining differ-
ences as large or larger due to sampling variation alone
is less than one in a hundred.

The standard deviation of differences of means and
value of "t" are determined by methods described by Baten
(p. 275, 1958). Results of "t" tests of these data are
presented in Table 58. The conventional terms "significant"
and "highly significant" are used to designate differences
significant at the 5 percent level (denoted by single
asterisk) and the 1 percent level (denoted by double asterisk),
respectively, in this paper when stating the statistical
significance of differences between means. Any difference
beyond the 5 percent level is termed "not significant.“

For purposes of illustration of methods used, the following
example is given.

It may be seen from Table 36 that the mean head-lengths
of the St. Helena Island and High Island fish are 8.349
and 7.811, respectively. The pooled standard deviation of
all age-group IV is 0.4250 (Table 57) for this measurement.
This quantity (5) is obtained by pooling the sums of the

squares of items from their respective means. The following

105

method is that used by Baten (1958). The standard errors

of the means of the two samples are

s __ s
8.13. if = «mm = 0.122 cm., S.E. X2 = --——— = 0.088 cm.

The standard error of the difference of the means is

 

S.E. Difference of means

_ 2 __ 2
1/(8.E.X1) + (S.E.X2)

 

 

= 0.150
The value of t is
4 "2'1 - 352 - o 8.849-7.811
t = _—— _ _— —— ——— = —— —— —— = 5.59**
S.E. Difference of means 0.150

If we consult a table for t-values (Snedecor p.65, 1946)

at 85 degrees of freedom (50 used), we find that the t-value
at the 5 percent point is 2.042, and at the 1 percent point
2.750. The value of t obtained is larger than the values
obtained from the table. This indicates that the differ-
ence between the means ( §d_ - '35 = 0.558 ) differs
significantly from zero and that the probability that

the two samples were taken at random from the same popula-

tion is very small; from the t-table this probability

.106

Table 38.-H: values of "1:" relating to paired comparisons between
samples of age-group IV (l9h6 year class) whitefish from Lake

Source of
sample

Date (1950)
number

St. Helena

Island

Gull
Island

High
Island

Big Bay
de Ibo

BigIBay
de Nbc

BigIBay
de Nbc

St. Helena
Island

August 12

12

5.18"

3. 59“

0.014

0.06

0.09

"’ Highly significant

lflchigan

Gull , High Big Bay de Noe (Burnt Bluff)

Island Island

august August August 16 Sept.12 Sept. 16

12 23 10

207». "
5. 66.. 30W. '-
6.71m ms» 0.12

5.35“ 5.03" 1-32

20 22

1077 "

ll Ill. lll‘llll‘ III I .i' 1'

fl

 

107
is less than 0.01.

In addition, the graphical method of Dice and Leraas
(1956) has been used to show relationship of the samples
in the head-length measurements (Figure 14). Means are
represented by crossbars. Bectangles show trice the
standard error each side of the means. Vertical lines
represent observed ranges of measurements. A similar
arrangement is followed in Figures 15-18. Samples are
arranged in the same order, from left to right, as listed
in tables of summary of measurements. In general, where
rectangles do not overlap, the means differ significantly.
This relationship is discussed by HUbbs and Perlmutter
(1942). Figure 14 suggests that two samples (Gull Island
and High Island) should be tested further. Values of "t"
tests for this age group are presented in Table 58. These
values indicate that, on basis of head length, the difference
between Gull Island and High Island fish are highly
significant. Further, that each of these samples differs
from the Big Bay de Noe and St. Helena Island fish at the
level of high significance. Among the Big Bey de Noe
samples there are no significant differences in head length.
In addition, the differences betreen the sample from St.
Helena Island and each of the Big Bay de Noe samples are
not significant.

Means and standard errors pertaining to additional
body measurements are given in Table 55. Preliminary

graphic inSpection of CPL, CPD, and SL measurements

. l' 'III- VIvIV.
ll l|l 'Il

M ILLI METERS

90

a)
U'
I

a:
C)
I

N]
U'
l

70"

 

65—

 

 

 

 

 

 

 

 

 

 

 

 

 

 

o
z
<
.1
o ‘2
<2:
4 5
‘2 - u
I U 0
O _J _ O 2
Z .l I z w
< 3 o
a” 0 L w
_ 0 >-
- -* s
g 2
m ‘9 S2
.1 en
La 9
I a:
F
U)

 

 

 

 

 

 

 

 

 

 

 

 

 

Fig. |4_Variance of head length of whitefish (Corsican:

clupeaformis) from Lake Michigan. Age group IV,
year class.

 

—

 

 

 

BIG BAY DE NOC'

 

 

109
indicated a very similar pattern as presented by head
measurements. From the method of analysis of variance,
the following F values vere obtained:

CPL, 10.87**; CPD, 9.38**; 8L, l2.1l**
Values of "t" for these measurements are presented in
Tables 59—41. It may be seen that, with the exception
of Gull and High Islrnd samples, the localities show
the same relationship in levels of significance for
these measurements as displayed by the head lengths.

0n the basis of the measurements analyzed, the
age—group IV (1948 year class) Whitefish from Gull Island
and High Island do not differ significantly (except in
head measurement) from each other, but exhibit differences
between St. Helena Island and Big Bay de Noc that are
highly significant. Differences between Big Bay de Noc
and St. Helena Island are not significant and differences
Within Big Bay de Noe are not significant.

Analysis of the ratios SL/H and CPL/CPD exhibit
values that indicate differences between the samples

are not significant.

Table 39.4311: values of "t' relating to pained comparisons between
samples or ago-group IV (191% year class) whitefish from Lake

Michigan
source of St. Helena Gun High B13 Bay do Nos (Burnt Bluff)
sample Island Island Island

Date (1950) August 12 August August August 16 sopt.12 Sept.16

Number 12 12 23 10 20 22

St. Helena

Island -

Gull

Island 3.88“ -

High

Island 3075” 0075 "'

Big my

do Noe 1.58 5.59” 5.61” -

Big Bay .

do Noe 0.61 3.73“ 3.56“ 1.65 «-

Big Day 4

do Noe 0.29 ”.11" ”~17” 269* 0.39 '-
*Significm

“manly significant

111

ram. 40.41%: values of «I relating to paired comparisons between
samples of age-group IV (1946 year class) whitefish from Lake
Michigan

source of Staelena Gull High Big Bay de Noc (Bumt Bluff)
sample Island Island Island

Date (1950) August 12 August August August 16 Sept. 12 Sept. 16

mum:- 12 12 23 10 20 22
Ste H010”
Island -
Gull
Island ”.25" ..
a. High
Island 3.66" 1.27 «-
Bis Bay
6.. N00 0036 ”on?" 3060" -
Big Day
de Noe 0.21} 11.99” 11.50" 0.17 -
Big Bay
de Noe 0.98 3.86” 3.11;" 1.32 1.112 -

"Highly significant

112

Table 1#1..» 81.: values of "t" relating to paired comparisons between
samples of age-group IV (1946 year class) whitefish from Lake

Source of St. Helena

sample

Date (1950) August 12

Number

815 . Helena

Island

Gull
I sland

High
Island

Bis Bay
de Noe

Big Bay
do Noe

Big Hay
do Noe

Island

12

ll .67"

n.06**

1.27

0.35

1.38

I""Highly significant

Michigan
Gull High Big Bay de Noe (Burnt Bluff)
Island Island
August August August 16 Sept.12 Sept.16
12 23 10 20 22
1e57 -
5.91" 5.20" -
5.09** 11.25” 1.73 -
M.16** 3.13** 1.9h 1.13 -

113
AGE GROUP III (1947 YEAR CLASS)

Morphometric measurements were taken of 115 fish
belonging to age-group III. A summary of these measure-
ments is presented in Table 42.

Applying the method of analysis of variance to the
several body proportion measurements, in order to test
the statistical homogeneity of the 5 samples, the follow-
ing F values were obtained:

SL H SL/H CPL CPD CPL/CPD
19.75** 17.83** 1.69 ll.69** 18.12** 1.97
The above F values are to be interpreted with degrees of
freedom.4 and 108 (or 110, see Table 42). The correspond-
ing 5 percent and 1 percent F values are about 2.46 and
3.51 respectively. 'Nith the exception of the two ratios,
SL/H and CPL/CPD, the differences are highly significant.

The differences between means were tested by use of
"t" tests. The values obtained for CPL and CPD measure-
ments are shown in Tables 43 and 44. Since a very similar
relationship between samples is shown for SL and H meas-
urement, t values are not presented.

Variations in mean length of head among the localities
follow much the same pattern as do the age-group IV fish
(Figure 14 and 15). However, in contrast to the IV group,
the High Island sample exhibits larger head measurement
than Gull Island fish, their difference being only

significant as compared to highly significant in age IV.

114

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115

The mean head length in each of the two Big Bay de Noc
samples exceeds those of the remaining samples. The differ-
ence between samples from Big Bay de Noc and the island
samples, Gull and High Island, is highly significant. In
general, the St. Helena Island sample agrees closely with
the Big Bay de Noc samples and differs significantly from
the island samples.

values of "t" for CPL and CPD measurements are given
' in Table 43 and 44. Since SL values follow the same pattern,
they are omitted. Generally, the following pattern or
relationships are shown between the samples when each meas-
urement is considered separately. The Big Bay de Noc samples
are clearly larger than the Gull Island and High Island
samples and their differences from.these two samples are
highly significant. The St. Helena Island sample closely
approaches those of Big Bay de Noc; however, in a few
instances (SL, H) the difference between this sample and
the Big Bay de Noe sample of September 12, 1950, are
significant. Among Big Bay de Noc samples there are no
significant differences.

A comparison between Gull Island and High Island samples
show significant differences for SL, H, and CPD measurements.
In.CPL measurement the samples do not differ significantly.

The means of all measurements considered are lowest in the
Gull Island and High Island fish. Differences between these

two samples and the other localities are, in general, above

116

the level of high significance; however, in a few instances
the St. Helena Island and Gull Island fish show differences

only at the significant level.

117

Table h3.-CPL: values of ”t" relating to paired comparisons
between samples of age III (1947 year class) whitefish
from Lake‘Michigan

Source of St. Helena Gull High Big Bay Big Bay

sample Island Island Island de Noc de Noe
Date (1950) Aug. 12 Aug. 22 Aug. 26 Sept.12 Sept.16
Number 26 15 19 27 26
Ste Helena

Island -

Gull

Igland 2.76” "

High

Island h.67** 1.50 -

Big Bay

de Noe 1.50 1+.o9’” 6.09" -

Big Bay

de Noc 0.13 2.859" 11.156M 1.1m .-

** Highly significant

,9

118

Table un.-CPD: values of "t" relating to paired comparisons
between samples of age-group III (1947 year class) white-

fish from.Lake'Michigan

Source of St. Helena Gull High
sample Island Island Island
Date (1950) Aug. 12 Aug.22 Aug.26
Number 26 15 19
St. Helena

Island -

Gull

Island 2.92" -

High

Island 5 .811“ 2.57* -
Big 8837

de Noc 1.65 1:53” 7.59“
Big Bay

(36 Noc 0.53 5A0“ 6.142“

* Significant

"‘" Highly siglifi cant

Big Bay Big Bay
de Noc de Noc
Sept .12 Sept.16
27 28
1.35 -

MILLIMETERS

90

85

75

7O

65

60

 

 

 

 

o
22
‘1
.J
g
o 9
z I
.‘3
m o
- 2
g 3
m 2
.1
m .1
I: .J
I)
f‘ (D
m

Fig. I 5_Variance of head length of
clugea‘formis) from Lake Michigan.
year class.

L_L_J

 

BIG BAY DE NOC m

whiter/d sh '

1_l_l

 

BIG BAY DE NOCI I I

(Coresonus
Age group II ,

 

120
AGE GROUP v (1945 YEAR CLASS)

Table 45 presents a summary of morphometric measure-
ments of 85 fish belonging to age-group V (1945 year class).
Due to paucity of V group individuals in the Big Bay de N00
and St. Helena Island samples, only collections from Gull
Island and High Island are compared. From Table 45 it is
evident that the means of the measurements agree very closely.
The analysis of variance was applied to the several body

proportion measurements and the following F values were

obtained:
SL H SL/H CPL CPD CPL/CPD
2.21 1.45 1.29 1.66 1.10 1.29

The above F values are to be interpreted with degrees of
freedom 3 and 78 (or 80, see Table 45). The corresponding

5 percent and 1 percent F values are about 2.72 and 4.04
respectively. In all measurements considered, the differ-
ences between Gull Island and High Island samples of fish
belonging to age-group V (1945) are not significant.

In order to illustrate the close agreement between

separate collections from.the same areas, head measurements

of the four samples are graphically presented in Figure 16.

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95 -
90 - __
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Fi l6 Variance of head length of Xhéteifg‘sll; (for-ego
clgpeaformis) from Lake Michigan. g g
year class.

123
AGE GROUP VI (1944 YEAR CLASS)

Summaries of morphometric measurements of 89 fish
belonging to age-group VI (1944) are presented in Table
46. As in age-group V, the Big Bay de Noc collections
were poorly represented by this age fish and, consequently,
only Gull Island and High Island fish are compared. The
High Island fish show means slightly lower than those of
Gull Island. This same general pattern is shown among
age-group V fish from the same localities.

From.the method of analysis of variance, the following

F values were obtained:

SL H SL/H CPL CPD CPL/CPD
2.50 1.55 1.45 1.51 1.50 1.49

The above values are to be interpreted with degrees of
freedom.3 and 87 (or 85, see Table 46). The correSponding
5 percent and 1 percent F values are about 2.72 and 4.04
respectively. In all measurements considered, the differ-
ences between Gull Island and High Island samples of fish
belonging to age-group VI (1944 year class) are not
significant.

In order to illustrate the close agreement between the
separate collections from the same areas, head-lengths of

the four samples are graphically presented in Figure 17.

124

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Fig. I7- Variance of head length of whitefish (Core 0 us
clu eaformis) from Lake Michigan. Age group VI,
year cIass.

AGE GROUP VII (1943 YEAR CLASS)

Table 47 presents a summary of morphometric measure-
Iments of 51 fish belonging to age-group VII (1945). Due
to poor representation of this age group, the samples of
August are combined in the High Island and Gull Island
collections. The Big Bay de Noc sample was taken
September 12, 1950. The six measurements listed in

Table 47 were tested by the analysis of variance method
and, with the exception of the two ratios, SL/H and CPL/CPD,
all show F values above the level of high significance.
The t-values for the measurements are presented in Tables
48—51.. Without exception, these four measurements follow
the same pattern. The Gull Island and High Island fish
are not significantly different from each other; yet,

the difference between each island collection and the

Big Bay de Noc fish is highly significant.

Figure 18 shows graphically the variance of head-
length of agengroup VII (1943) fish. An additional
sample of 35 Big Bay de Noc fish taken September 16,
1950, is shown. Since there is very close agreement
of this sample with the Big Bay de Noc sample of
September 12, 1950, data are not included in Table 47.
Analyses of the six measurements of these two samples
exhibit no significant difference among the Big Bay
de Noc fish.

127

 

 

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Table lLS.-CPL: values of “1:" relating to paired
comparisons between samples of age-group VII
(19%} year class) whitefish from Lake Michigan

Source of Gull
sample Island

Date (1950) August

Number 19
Gull

Island -
High

Island 0 009
Big Bay -

de Noc hall“

High
Island

August
17

u.13**

Big Bay de

Noc

September 12

15

Table ’49.-CH): values or "1:" relating to paired
comparisons between samples or age-group VII
(1914} year class) whitefish from lake Michigan

Source of Gull
sample Island

Date (1950) August

Nunber 19
Gull

Island -
High

1518111 0.01
Big Bay

d6 NOC 5053“

”Highly signi fi 0 ant

High
I sland

August
17

5 .30**

Big Bay (16

Noc

September 12

15

Table 50.-SL: values of "t" relating to paired
comparisons between samples of age-group VII
(19,43 year class) whitefish from Lake Michigan

Source of Gull High Big Bay de
sample Island Island Noc

Date (1950) August August September 12
Number 19 17 15

Gull

Island -

High

Island 0.22 -

Big Bay

de Noc 2.77** 2.91** -

Table 51.-H: values of "t" relating to paired
comparisons between samples of age-group VII
(1914} year class) whitefish from Lake Michigan

Source of Gull High Big Bay de
sample Island Island Noc

Date (1950) August August September 12
NUmber l9 ‘ 17 15

Gull

Island -

High

Island 0.3} -

Big Bay

de Noe 2.78 ** 3.02M -

“Highly significant

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.1 “J
.J :2 C3
— U
2 -- o z;
90 I- L— 2 m cl
S? G)
a)
{BESP ‘
80L. ..

Fig. I8 Variance of head length of whitefish (Core onus
clupeaformis) from Lake Michigan. Age group VII, 1533
year class. -

COKPhRISON OF ssxs

Since most of the body proportion measurements were
made of collections in which sex data were unknown, or
the numbers of known individuals were so few that it
was necessary to combine the data, it becomes a matter
of special importance to test the relationship of the
sexes. .

Data relative to sex are available for the folloaing
age groups: .

Age~group VI (19 5 year classl. These fish were taken
from near Round Island, Big Bay de Noc, on October 6, 1949.
Since this collection was made at a time during which
enlargement of gonads is known to take place, differences
between sexes relative to body form should be pronounced
at this particular season. Tests of significance of the
six measurements (SL, H, SL/H, CPL, CPD, CPL/CPD) were made
between 75 males and 66 females. Differences between
males and females, for the measurements considered, were
far below the level of significance.

Ageggroup VII 11945year class). Data relative to
sex are available for 52 fish from the collection of
September 12, 1950, taken in Big Bay de Noc off Burnt
Bluff. Comparison of 55 males and 19 females, with
respect to the measurements of SL, H, SL/H, CPL, CPD,
CPL/CPD, show that the difference between males and

females is not significant.

152
SUMMARY

1. Age composition, strength of year classes, growth
in length and weight and measurements of several body
proportions of whitefish from northern Lake Michigan are
presented.

2. Collections were taken from three principal sample
areas: Big Bay de Noc, Gull Island, and High Island. Data
were taken directly from the commercial catches during
portions of the years 1948, 1949, and 1950.

3. Length-frequency distributions arranged according
to age of fish are presented for the samples. Gull Island
and High Island samples show more overlapping of the
lengths of fish belonging to different age groups than do
the Big Bay de Noc samples.

4. In the 1950 collections year classes 1945 and
1944 (age-groups V and VI respectively) dominated the
catches from Gull Island and High Island, and made up
slightly over 50 percent of the total samples. Big Bay
de Noc collections of the same year exhibited an especially
poor representation by these year classes; the 1945 year
class was represented by only 5.1 percent and the 1944
year class was not recorded in any of the catches sampled.

5. In the Big Bay de Noc - Pt. Detour samples, the
especially high dominance of the 1945 year class is
evident. This year class as the V group of 1948 accounted
for over 80 percent of the total catch, as the VI group

.\.\-

133
of 1949 made up 64 percent, and as the VII group of 1950
made up 27 percent of the collections.

6. Calculated lengths for each year of life through
8 years indicate values for the Big Bay de Noc fish exceed
those of Gull Island and High Island samples. The advantage
of the Big Bay de Noc whitefish over Gull Island specimens
increased from 0.7 inches at the end of the first year of
life to 1.3 inches at the end of the eighth year. The
advantage of the Big Bay de Noc whitefish over the High
Island specimens increased from 0.7 inches at the end of
the first year to 2.3 inches at the end of the eighth year.
Calculated lengths for the St. Helena Island fish approach
closely the values determined for the Big Bay de Noc white-
fish.

7. The length-weight relationship of the 1949 collec-
tions of Big Bay de Noc whitefish with standard lengths of
340 to 519 millimeters is expressed by the equation

log W = - 8.4271 + 3.2544 (log L)

8. The length-weight relationship of the 1950 collec-
tions of Gull Island whitefish with standard lengths of
350 to 529 millimeters is expressed by the equation

log W’ = 4— 7.7239 + 2.9886 (log L)

9. The length-weight relationship of the 1950 collec-
tions of High Island whitefish with standard lengths of
370 to 509 millimeters is expressed by the equation

log W = —— 7.2567 + 2.8166 (log L)

\\

134

10. The 1950 collections were examined for scars
suspected to be caused by sea (lake) lamprey, Petromyzon
marinus, Tabulation of marked fish on basis of age
groups revealed no fish belonging to age-groups I, II,
and III showing either fresh or healed scars. Of a
total of 94 fish examined belonging to age-group IV
(1946), only 4 fish showed fresh scars and 2 exhibited
healed scars. The 1950 collections from Gull Island
and High Island show slightly higher percentage of
fish bearing scars than the Big Bay de Noc samples.

11. The method of analysis of variance, based
upon the year classes, is applied to several body
proportion measurements of fish from different localities.

12. Four measurements (SL, H, CPL, CPD) taken of _
fish from four localities and belonging to five differ-
ent year classes (age-group III to VII) are compared.

In general, differences between Gull Island and High
Island fish are not significant, except among the young
fish (III, IV). Fish from each of these localities
differs from the Big Bay de Noc fish at the level of
high significance. St. Helena Island fish closely
approach those of Big Bay de Noc; however, in a few
instances the differences for a few of the measure-
ments are significant. Among the Big Bay de Noc samples

there are no significant differences.

155

13. The ratios SL/H and CPL/CPD were determined
for the several localities. Values of SL/H range from
4.927 to 5.187 and those of CPL/CPD from 1.558 to 1.686.
The method of analysis of variance applied to values
determined for the several samples reveal no significant
differences between fish from any of the localities.

14. Tests of significance of the six measurements
(SL, H, SL/H, CPL, CPD, CPL/CPD) show that the differ—
ences between males and females of Big Bay de Noc fish
taken in October, 1949, and September, 1950, are not

significant.

136
LITERATURE CITED

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1938 Elementary mathematical statistics. John
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Biennial Reports
1947 Michigan Department of Conservation, Fish
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1949 Michigan Department of Conservation, Fish
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1948. PP. 61-120.

1951 Michigan Department of Conservation, Fish
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Burkenroad,iM.D.
1948 Fluctuations in abundance of Pacific halibut.
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1944 Some uses of nomographs in fish growth studies.
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1936 A contribution to the "race question." Rapp.
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Dymond, John R.
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Eichler, H.
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Godsil, H.C.
1948 A preliminary population study of the yellow-
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7‘

137

Hart, J.L.

1930 The spawning and early life-history of the
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Hile, Ralph
1935 Summary of investigations on the morphometry
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Hjort, Johan
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Hubbs, Carl L., and Alfred Perlmutter
1942 Biometric comparison of several samples, with
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Huntsman, A.G.
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138

Koelz, Walter
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1931 The coregonid fishes of northeastern America.
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Kuhne, W.

1938 Untersuchungen uber die festigkeit und
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Lea, Einar ,
1930 Fluctuations in the stock of fish. Herring.
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Lechler, H.
1938 Uber den zusammenhang von gewichtund langen-
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Eartin, W.R.
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1941 The covariance method of comparing the head-
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RiCker , on o
1940 Relations of "catch per unit of effort" to
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139

Svgidson, Gunner
1949 The coregonid problem. 11. Morphology of two
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Van Oosten, John
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1939 The age, growth, sexual maturity, and sex ratio
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1934 A microprojection machine designed for the
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Van Oosten, John, and Ralph Hile
1947 Age and growth of the lake whitefish,
Coregonus clupeaformis (Mitchill), in Lake
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Walford, L.A.
1946 Correlation between fluctuations in abundance
of the Pacific sardine (Sardingps caerulea)
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6 (1), Pp. 48-53.

140

APPENDIX

Calculated growth:

S
_ n
Ln - c + --§--- (L - c)
where
Ln = length of fish at any annulus
formation
L = length of fish at time of capture
c = length of fish when scales appeared
S = scale diameter (or radius) at time of
capture (outside scale measurement)
and Sn = scale diameter (or radius) at any

annulus.

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H‘ “ (
, (_ .a ‘ ' ‘3-1.-'H‘-~ ,w-v
. 1 (~11 m: mews» a...
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