THE AGE Am: GROWTH 05 ms:
YELLOW PiKEPERCH
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'LMITCHILL) IN THE GREEN BAY.
WATERS OF LAKE MGMGAN

Thesis for the Degreu of M. S.
MICHIGAN STATE COLLEGE
Rank art F; Batch
1952

 

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"The Ace and Growth of the Yellow Pike-
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(Mitchi 115 in the Green Bay Waters

of Lake Michigan"

presented by
Robert F. Belch

has been accepted towards fulfillment
of the requirements for

M. S. degree in Zoologx

Major professor

Date OCtOber [+1 1'9le

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THE AGE AND GROWTH OF THE YELLOW PIKEPERCH
STIZOSTEDION VITREUM VITREUM (MITCHILL)

IN THE GREEN BAY WATERS OF LAKE MICHIGAN

BY
ROBERT F. QALCH

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

MASTER OF SCIENCE

Department of Zoology
1952

TABLE OF CONTENTS

Introduction.................
Acknowledgements....... .... ... .
Materials andMethods . . . . . . . . . . . .
Production of Yellow Pikeperch in Green Bay .

Seasonal fluctuations . . . . . . . . . .

CatchbyGear..............

Return per unit of Effort . . . . . . . .

Age class composition of the catch . . .
ThelQQYearClass............ .
Growth of the Yellow Pikeperch in Green Gay .
SexualDetermination. . . .. .. . . . . . .
éemalliaturity...............
Growth in Other Waters . . . . . . . . . . . .
Summary.....‘..............

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16
16
19
28
32
35
56
6O
62
70
73

FIGURES AND TABIES
PAGE

Figure 1 c c e e o o e o o e o e o o e e o o o o 6

Production of Yellow Pikeperch Stizostedion

Vitreum Vitreum Mitchill) in the State of
mIc'fiIgan Waters 0 reen ay (Dist. M—l)

1929-1949, Table I-A o c e e». o o 0 ea. c o o 9

Fluctuation in the Production of Yellow Pike-

.perch Stizostedion Vitreum Vitreum (Mitchilll

in the State of Wisconsin Waters ofaGreen Bay
1929-1949, Table 1.3 c e a e o c o o c o c c o 10

Fluctuations in the Production and Abundance

-of Yellow Pikeperch Stizostedion Vitreum

Vitremn (Mitchilll and in the Flsmtensity
for the Species in the State of Michigan Waters

of Green Bay 1929-1948(Production in Thousands

of Pounds-Abundance and Fishing Intensity as
Percentages of the 1929-1948 Mean). . . . . . . ll

 

FngIO 2 o o e c e e o e o e o o c c o e c o c e 12

Monthly Trends in the Yellow Pike Fishery in
the State of Michigan Waters of: Green Bay
Diate MP1, 1929-1949. a e c e o c o oo o o 017. 18

Monthly Trends, by Gear and unit of Effort Cal-
culations, of the Yellow Pikeperch Fishery in
the Wisconsin Waters of Green Bay 1944-1949,
AreaIM‘l. c e a o o o o o o o c c o o o 0 22.23.24

catch by Gear in the Yellow Pikeperch Fishery
in the State of Michigan Waters of Green Bay
Dist. Mkl, 1929-1949 Table V. e c o o e e c c c 25

Average Catch (Pounds) of Yellow Pikeperch
Stizostedion VitreumAVitreum Mitchill Per

LITE of Una Net 33 the State 0 0 gen

Waters 0: Green Bay 1929-1948 Table VI. 0 o c o 26

Fluctuations in the Production and Abundance

of Yellow Pikeperch Stizostedion Vitreum

Vitreum Mitchilll in the State of Wisconsin
Waters 0 Green Bay (Dist. M-l) 1943-1949 . . . 27

ii

FIGURES AND TABLES (CONT'D)

A. Summary of Yellow Pikeperch Samples in
Northern Green Bay Michigan Waters Showing
Year Class Composition of the Catchby Gear

Calculated Total Lengths (Inches) of the
Northern Green Bay YellowPikeperch Taken
by all Major Types of Gear 1949-1951. . . .

Average Length and Weight at Capture of
Yellow Pikeperch From Southern Green Bay
and the Average Calculated Length Attained
by the Age Groups at the End. of Each Year
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Growth of the Yellow Pikeperch in Northern
Green Ba Samples were Taken by 4%" Gill
(Hatm1n194geoceoocsaocec

Growth or‘the Yellow Pikeperch in Northern
GreenBaJTableIII...o........

Calculated Total Lengths (Inches) of the
Northern Green Bay YellowPikeperch Taken
by Trap Nets (N613 Run») 1949 e c o c c c o 0

Calculated To tel Lengths (Inches) of the
Northern Green Bay YellowPikeperch Taken
by Trap Nets (Net Run) During 1950. . . . .

Length-Frequency of 835 Yellow Pikeperch
.From Northern Green Bay During the Years
1949-195000000000000000000

Values of Length, Actual Weight, Theoretical
Weight, and Condition Factor Expressed in
English and Metric Systems by One-Half Inch
Length Intervals for Male Yellow Pikeperch
in Northern Green Bay 1949-1950 e . . . . .

Values of Length, Actual Weight, Theoretical
Weight, and Condition Factor Expressed in
English and Metric Systems by One-Half Inch

Length Intervals for Female Yellow. Pikeperch
in Northern Green Bay1949-l950 e o e e o o c

111

PAGE
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. 36
. 57
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. 44
. 45
. 46
. 48
.51,52
.53,54

FIGURES AND TABLES (CONT'D)

PAGE

The Calculated Growth in Weight of the
Yellow Pikeperch in Northern Green Bay. . . . . . 57

Figure4ooceeeeeeooeeeeseooo.58

Factors fer Conversion Between Total (T.L.)
and Standard (S.L.) Lengths of GreenBay .
YQIIOWPikePerCh-oeeeeeeooe000000059

Sexual maturity of Yellow Pikeperch in
.NorthernGreenBay. cc 0 c e o o so a o o e o 065

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F1g111‘95coecceoeooooeeoooc.0065
Comparison of Lengths (Inches) at Different

Ages at Yellow Pikeperch Caught in Saginaw

Bay in 1926-1930 and 1943 . . . . . . . . . . . . 67

Comparison of Weights (Pounds) at Different
ages of Yellow Pikeperch Caught in Saginaw
Bay1n1926-1950and194300 can a one. 0068

iv

-1-
THE AGE AND GROWTH OF THE YELLOW PIKEPERCH, STIZOSTEDION

 

VITREUM VITREUM (MITCHILL), IN THE GREEN BAY’WATERS or
' ’ LAKE MICHIGAN

BY
ROBERT F. BADGE

INTRODUCTION

This study was initiated during the summer of 1949
while the author was a student at Michigan State College.
It was continued during 1950 and 1951 by the author as
a research project at the Sturgeon Bay, Wisconsin, head-
quarters of the Wisconsin Conservation Department. The
State of Wisconsin and the U.S. Fish and Wildlife Service,
through a 'co-Operative agreement, maintain a research
station at Sturgeon Bay, Wisconsin, for investigations
of the waters of northern Lake Michigan and Green Bay.

Green Bay is only 118 miles long and 23 miles wide
at the maximum. In spite of its small size, this body
of water is extremely productive. In 1936-1946, the
Wisconsin waters yielded a recorded'annual harvest of
6,139,000 pounds. The statistics are not complete for
the first seven years of that period. For the same

period, Michigan waters of Green Bay yielded 3,553,000

pounds.

- a -

The high productivity of the bay is influenced by
the shallow character of this body of water and by the
higher temperature at the water. Its fisheries are for
all practical purposes distinct from those of Lake
Michigan.

The fishery of Green Bay is much.more intensive
than that of the lake. The character of the bay is
conducive to greater effort on the part of the Operator,
since nets can be set at any place in the bay, resulting
in less time spent in travel and more time can be spent
lifting and setting on the grounds.

The waters of Green Bay are administered by two
states. Regulations concerning minimum legal length
and fishing gear vary. IMichigan, for example requires
a 15% inch minimum size limit, while Wisconsin limits
the size of the yellow pikeperch to 15 inches. Wiscon-
sin has made the trap net illegal to Operate, while
IMichigan has.not outlawed this type of gear. ZMany other
regulations differ for Wisconsin and Michigan waters of
Green Bay. '

The yellow pikeperch pepulations of.northern and
southern Green Bay act like different pepulations en-
tirely. Growth rates differ. Factors causing the rise
and fall of the populations do not seem to affect both
regions in the same way. Fish.populations of.northern

and southern Green Bay are composed of different species.

- 3 -
Southern Green Bay produces large amounts of carp, yel-
low perch, smelt, catfish, herring and sheepshead.
Northern Green Bay produces largely Whitefish, yellow-
pikeperch, herring, smelt and yellow perch.

While a large number of investigators have des-
cribed the growth.of the yellow pikeperch, Stizostedion
1. W (Mitchill) the recent increase in production
in Northern Green Bay waters and the lack of specific
information on this particular population has made this
study valuable from a fish management standpoint.

ACKNOWLEDGEMENTS

I wish to acknowledge the assistance and advice of
Dr. Peter I. Tao]: of the Department of ZOOIOgy, Michigan
State College, under whose guidance this study was
initiated.

Dr. Ralph Hile, Supervisory Fishery Research Biol-
Ogistlof the U.S. Fish and Wildlife Service, Great Lakes
Fishery Investigations contributed three samples of data
taken during the spring of 1949, and the spring of 1950.
The statistical data for the yellow pikeperch fishery
of northern Green Bay was prepared by Dr. Hile. Much

valuable advice as to analysis and presentation of data,

from Dr. Hile is gratefully acknowledged.

- 4 -

Mr. Leonard Joeris, Fisheries Research BiOIOgist,
and Mr. Donald Mraz, Fisheries Technician, of the'U.S.
Fish and Wildlife Service; and.Mr. William Gerl, of the
Wisconsin Conservation Department, all aided in the col-
lection of data.

Commercial fishing statistics for the Wisconsin
waters of Green Bay were obtained from the Commercial
Fisheries section of the Wisconsin Conservation.Depart-

nent at Sturgeon Bay, Wisconsin.

IMATERIALS AND METHODS

This investigation of age and growth has been
based upon the determinations of ages for 835 yellow
pikeperch from northern Green Bay and 33 specimens from
southern Green Bay. Samples for growth calculations
were restricted to random samples of known sex.

Specimens were obtained largely from.wholesale fish
dealers in the area. When possible, samples were ob-
tained directly from the fishermen. Unless otherwise
noted, all are not run samples. In the case of extremes
in size, selection was.made for purposes of completeness.

Samples in northern Green Bay were taken in the
vicinity of the following localities: Fairport, Round
Island, Garden, Ogontz Bay, Wilsey Bay, Escanaba, Ford
River, and Cedar River, Michigan; Marinette, Peshtigo

- 5 -
and Suamico, Wisconsin. Figure I shows saMpling loca-
tions. -

With the exception of the seine, samples were taken
from all types of commercial gear used to harvest yellow
pikeperch in this area. These include the fyke net, the
pound net, the trap net and the gill net. Samples from
both large mesh (4% inch stretched measure) and small
mesh (2% inch stretched measure) gill nets were taken.

Scale samples were taken in the field from all Spec-
imens. The scale samples were obtained from the left
side of the fish above the lateral line in all cases ex-
cept one sample taken during the fall of 1949.

These particular scale samples were taken below the
lateral line. .All scales were taken from the area immed-
iately ventral to the dorsal fin.

With each scale sample a record of the date, loca-
tion or capture, type of gear, length (total length was
taken as the distance from the tip of the snout to the
line connecting the tips of the extended caudal fin),
weight, sex, and state of maturity was made. In addition
standard length was taken for 332 individuals from all
length intervals. Standard length was measured from
the tip of the snout to, and including, the last caudal

vertebrae.

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- 7 -
.At least three scales from each fish were mounted
on a microscope slide in a gelatin-glycerin medium.
The scales were studied by means of a Bausch and Lomb
Microprojector. .At least two of the three scales in
each individual sample were read. The entire collection
of scales were read twice, and.checked once.
Growth calculations were made by measuring the
distance from the annulus to the focus of the scales
in the anterior field. Individual calculations were
then made with the use of a nomograph as outlined by
Hile (1948).
' The intercept length used in computations was 50
millimeters. This figure was calculated by Deason
(unpublished) in his work with the yellow piheperch
or Lake Erie.
‘ Age was recorded for each individual as the number
of years of life actually completed. Thus a fish of A
eight growing seasons would be designated as age class
VII until after the next springs spawning takes place.
I. The time of annulus formation was not determined
for this study. In a sample of 18 specimens made at
Cedar River, Michigan, May 18, 1949, none of the scales
showed a positive annulus recently formed. The same was
true for a sample of nine fish taken May 17, 1950, from

the same locality. The next samples were taken on

- 3 -
August 21, 1950, and all specimens showed complete an-
nulus formation. Presumably, the annulus is formed

during the month of June.

PRODUCTION OF YELLOW PIKEPERCH IN GREEN BAY

Production figures for both the Michigan and Wis-
consin waters of Green Bay are available prior to the
year 1929, but are not known to be accurate. Because
of this fact, only those statistics compiled since
1929 are used.

Dr. Ralph Hile, in an article printed in the
March, 1950, issue of "The Fisherman“, described the
commercial fishery for yellow pikeperch in Green Bay.

In his study of the trends of this fishery in northern
Green Bay, he used a base period of 15 years from 1929
to 1943. During this period, the production fluctuated,
but within-rather narrow limits as compared to the
recent increase.

In Table I-A, it may be seen that the greatest pro-
duction during this period occurred in 1934, when
108,247 pounds of yellow pikeperch.were taken commerb
cially in the Michigan waters of Green Bay. During
this same period, (Table I-B) Wisconsin's greatest pro-
duction occurred in 1930, when Commercial fishermen

reported an annual catch of 21,710 pounds.

Table I-A

PRODUCTION OF YELLOW PIKE-PERCH
STIZOSTEDION VITREUM VITREUM (EITCHILL)
IN THE STATE OF MICHIGAN WATERS 0F GREEN BAY
(DISTRICT M-l) l929-l9h9

 

Year Production
1929 267963
1930 27,4h6
1931 h1,né9
1932 85,059
1933 108,110
l93h 108,247
1935 57,371
1930 73,7h8
1937 59.345
1938 38,023
1939 30,177
19h0 27,029
1941 25,987
1942 16,121
19h3 30,215
l94h £2,908
19h5 20,712
l9h6 71,798
1947 261,627
1948 571,099
1949 1,003,016 *

* Tentative figure
--Dr. Ralph Hile, U. 3. Fish & Wildlife Service,
Ann Arbor, Michigan

- 10 -

Table I-B

FLUCTUATIONS IN THE PRODUCTION OF YELLOW PIKE-PEHCH
STIZOSTEDION VITREUM VITREUM EMITCHILLE IN THE STATE OF
WISC G nI‘

 

 

ONSIN'WKTERS OF A 929-l9h9
Year Production
1929 13,307
1930 21,710
1931 h,o87
1932 3,365
1933 4,200
1934 u,ooo
1935 2,600
1936 1,36h
1937 25
1938 15
1939 7,390
1940 3,759
19h1 -------
19h2 -------
1943 to
l9hh 200
19h5 117,209
1946 119,900
1947 72,6hh
19h8 35,097
1940 20,891

Note: 1929-1945 figures represent production for
Green Bay and Lake Michigan.

--1929-1935 figures from U. 8. Bureau of Fisheries
--l936-19h9 figures from Wisconsin Commercial Fishing Reports,
Sturgeon Bay, Wisconsin.

Table II

FLUCTUATIONS IN THE PRODUCTION AND ABUNDANCE OF YELLOW PIKE-PERCH
STIZOSTEDION VITREUM VITREUM EMITCHILL) AND IN THE FISHING INTENSITY
FOR THE SPECIES IN THE STATE 0 I C IGAN WATERS 0F GREEN BAY 1929- 1948
(Production in Thousands of Pounds-Abundance and Fishing Intensity as
Percentages of the 1929- 1948 Mean)

 

Per cent
Fishing of

Year Production Abundance Intensity Prodqgtigg
1929 27 54 104

1930 27 57 98 53
1931 41 83 102 81
1932 85 121 144 167
1933 108 198 111 213
1934 108 171 129 213
1935 57 106 108 112
1936 74 115 127 146
1937 59 105 112 116
1933 38 57 132 75
1939 30 54 112 59
1940 28 86 64 55
1941 26 108 48 51
1942 16 66 48 31
1943 36 119 61 71
Average 51 100 100

1944 43 152 56 85
1945 21 89 47 41
1946 72 136 105 112
1947 262 220 236 510
1948 572 282 403 1126

--Dr. Ralph Hile, U. 8. Fish & Wildlife Service
Ann Arbor, Michigan

 

 

 

IN
GREEN BAY WATERS
OF
LAKE MICHIGAN
I929 '- I9 49

FIGURE 2
PRODUCTION OF YELLOW PIKEPERCH

 

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- 15 -

The smallest annual production for the 1929-1943
period occurred in.Michigan waters in 1942, when
16,121 pounds were produced. In Wisconsin, however,
the yellow pikeperch was removed from the commercial
list and for the period of 1941 and 1942, there was no
commercial fishing for this species reported.

Because there has not been the great fluctuation
in production of yellow pikeperch in Wisconsin and
because of the incomplete statistics, no detailed an-
alysis of the production has been made. It may be
seen, however, from the graph on production for both
Michigan and Wisconsin (Fig.2), that Wisconsin's yel-
low pikeperch fishery is not nearly as great as that
in Michigan. Furthermore, the factors that caused the
tremendous increase in the yellow pikeperch population
in northern Green Bay are evidently lacking or insig-
nificant in southern Green Bay;

The present abundance of yellow pikeperch in north-
ern Green Bay is not a normal situation. It is obvious
from past catch statistics that Green Bay does not
produce yellow pikeperch normally in the quantities
that have occurred since 1946. After consulting Table
II, it can be seen that the catch in 1948 was 1126 per-
cent of the production average over the 1929-1943 base

period.

- 14 -

There is, however, more to the picture than pro-
duction alone. One must consider effort as well as
production when considering the relative abundance of
a fish papulation. If the level of abundance of a
certain fish population remains constant, the production
may be increased or decreased by the fishing intensity.
In other words, a man can fish more gear and lift more
often to produce a higher yield.inspite of the fact
that the number of fish available remains constant.

To evaluate this change of fishing intensity or
effort, scientists have devised an index called the
unit of effort. This value actually'is the average
catch per. net per lift. Thus the variable of changing
fishing intensity is eliminated.

It may be seen from Table II that the fishing
intensity in 1948 was 403 percent of the 1929-1943
average. It is obvious, therefore, that the production
Of Green Bay is due in some part to greatly increased
fishing pressure.

In Table II, there will be fdund a column en-
titled WAbundance". These statistics supplied by Dr.
Ralph Hile represent percentages of the catch per unit
of effort related to the average catch per unit of effort
for the 1929-1943 period. Thus, the index of abundance
eliminates the variable, fishing intensity, and gives

. as accurate an index as possible of the actual abundance

- 15 -
of the population.

In Table II, there may be found a column headed
"Percent of Production". These figures are percent-
ages computed using the 1929-1943 average as a basis
and assigning that value 100. Thus it may be seen
that some years,prior to 1943, were better than average
(an index of abundance of over 100) and for some the
production did not equal the average figure.

In 1948, in spite of the fact that the fishing in-
tensity was 403 percent of the 1929-1943 mean, the
index of abundance was 282 percent of the average for
the base period.

Fishermen in northern Green Bay in 1948 were fishing
four times as intensively as they did during the base
period and were taking about eleven times as many fish
as they did during this period.

From these facts, therefor, it is evident that the
increased yield of the Green Bay waters of Lake Michi-
gan is due primarily to two causes. The first is the
greatly increased number of available yellow pike-
perch, and the second is the increased fishing pressure

or effort directed toward the capture of these fish.

- 15 -
SEASONAL FLUCTUATION

Table III presents data on the monthly trends of
yellow pikeperch production in Michigan waters. There
is a fluctuation evident in the production during the
different seasons of the year. The period of greatest
productivity occurs in the spring. During the months
of May and June, roughly 50 percent of the annual catch
is made. Yield decreases during the warm summer
months, presumably because of rising water temperatures.
During the months of September and October, another
heavy catch is taken. The winter months are periods
of low yield because of curtailed operations due
to cold weather. While the ice cover permits a rather
intensive gill net fishery, trap, fyke, and pound nets
are fished with some difficulty. It will be noted be-
low that these types of gear produce the bulk of the

catChe

CATCH BY GEAR
It may be seen in Table V that the catch by gear
varies widely. Fyke and hoop nets during the 1929-
1943 base period caught 50.2 percent of the average

annual yield.

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15,121 30,210 761,910

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. 19 -

Pound nets produced the next greatest amount or
24.9 percent of the average annual catch. Shallow
trap nets produced 20.2 percent and large mesh gill
nets produced 3.6 percent. In Wisconsin waters, the
trap net is considered as an illegal type of fishing
gear. From Table IV, the gear producing the greatest
percentage of the catch in Wisconsin waters was the
fyke and drop net with 74.1 percent of the total catch
for the period of 1944 through 1949. Seines followed
with 11.9 percent. Pound nets produced 6.6 percent,
and large mesh gill nets (4%" up) produced 6.4 percent
of the catch. Small meshhgill hét (2 3/8' and up to
2 3/4“) produced approximately 1 percent of the total

gal

catch.

RETURN PER UNIT OF EFFORT

This calculated value, perhaps more than any other,
assists the fishery biologist in examining catch step
tistics for it is in itself, an index.of abundance.
Levels of abundance are reflected in its fluctuation
for it eliminates the variable fishing intensity. Pro-
duction may remain constant in a declining fishery, but
the return per unit of effort accurately records the

condition of the fish papulation.

- 20 -

The yield in pounds divided by the amount of gear
used, yields an average weight value per net per lift.
The length of time the net is in use is disregarded.
Unit of effort values are calculated on the basis of
one net and one lifting of that net, in the case of
fyke, trap and pound nets, and on the basis of 1,000
lineal feet in the case of gill nets and seines.

Table VI and VII show unit of effort calculations
for Michigan and Wisconsin waters of Green Bay. It is
interesting to note in Michigan's production (Table VI)
that the fyke net not only produces the largest amount
of yellow pikeperch, but also the greatest return per
unit of effort. For the period of 1929-1943, fyke nets
produced 1.? times the amount of fish that the pound
nets produced per lift and 4.2 times the amount that
trap nets produced. However, the same does not hold
true for the yellow pikeperch fishery of southern Green
Bay. Here the seine, a gear not important in northern
Green Bay waters, produces the greatest return per unit
of effort. Gill nets are second in importance, pound
nets third and fyke nets are last, inspite of the fact
that they produce the largest percentage of the total
yield. This may be explained by the nature of the

fishery in southern Green Bay.

- 21 -
The major fish produced in southern Green Bay are

the yellow perch Perca flavescens, the lake herring

 

.Leucichthys artedi and the carp Qyprinus carpio. The
major type of gear fished during the open water season

is the fyke or drOp net. These nets are essentially
fished for perch and, incidental to their Operation,
catch the bulk of the yellow pikeperch produced annu-
ally. The seine is used principally for the capture of
carp and, while not used extensively, it does result in a
high return of yellow pikeperch per unit of effort.

The pound net in southern Green Bay produces lake
herring to a large extent, but some yellow perch, yellow
pikeperch, white fish Coregonus clupeaformis, smelt Osmerus
mordax, are also taken incidental to the catch of herring.

It is significant that the total poundage of yellow
pikeperch produced by the use of seines is not large,
while the total produced by fyke nets is very large.

The fishery for yellow pikeperch in southern Green Bay
is directed toward other species and yellow pikeperch
are taken incidental to the catch.

The yellow pikeperch fishery in northern Green Bay
is directed toward the capture of this species and yellow
perch, carp, and other species are incidental. The gear
set in northern Green Bay is designed to fish for yellow

pikeperch alone.

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-25..

Table VI

AVERAGE CATCH (POUNDS) OF YLLLow PIKE-PERCH
§IIZOST§QLQE VITREUM VITREUM (MITCHILL) PER LIFT
OF one NET IN T33 STATE OF RICHIGAN WATJRS 0F GREEN BAY

 

 

 

1929-1948

Year Gear __

Pound ghaIIOW ‘F§ke

Ne; ran Egg Net

1929 10. 3.7 15.6
1930 7.6 4.6 20.2
1931 11.0 10.2 27.3
1932 19.6 9.8 37.0
1933 33.3 19.2 56.6
l93h 31.8 8.6 59.3
1935 35.3 5.h 31.0
1936 61.6 7.1 20.1
1937 19.8 9.0 30.2
1938 7.8 4.0 23.1
1939 7.7 2.h 22.7
1940 9.8 7.5 28.1
1911 9.0 10.9 32.1
19h2 9.3 h.4 23.4
1943 10.9 7.3 56.0
Average 19.0 7.6 32.0
19hh 12.5 13.3 58.3
1945 5.7 16.6 19.8
1946 7.5 20.6 23.6
1947 16.8 30.2 h7.5
1918 27.6 40.1 66..

--Dr. Ralph Hile, U. S. Fish & Wildlife Service,
Ann Arbor, Michigan

- g7 -

Table VII

FLUCTUATIONS IN THE PRODUCTION AND ABUNDANCE 0F YELLOW PIKE-PERCH
STIZOSTEDION VITREUM VITREUM MITCHILL IN THE STATE OF WISCONSIN
WATEF§“UP“GPEEN"§KYLTUT§TRTU% M-l) 1943-1919

(Pounds Per Unit of Effort)

 

 

 

 

Year Gear Total
Gill Pound Fyke-Drop Production
Net Net Net___ Seine in Pounds
1943 3.3 2.4 46
1944 9.3 1.5 1.3 200
1945 20.1 5.9 3.4 18.1 117,209
1946 20.0 7.8 4.1 31.2 119,906
1947 12.1 7.1 3.3 52.2 72,644
1948 15.0 6.5 3.0 32.0 35,697
1949 7.0 10.3 2.3 31.7 40,891

Unit of_effort defined as harvest/amount of gear.
--Wisconsin Commercial Fishing Reports,
Sturgeon Bay, Wisconsin

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- 28 -
AGE AND YEAR CLASS COMPOSITION OF THE CATCH

The following discussion of the age and year class
composition of the commercial catch is based on observa-
tions made on random samples from commercial gear. It
will be noted, however, that two samples from small-mesh
gill nets, a gear not fished for walleyes, are included in
Table VIII. Because of the small size of the southern
Green Bay collections, no tabulation was made of the age
class composition of that particular population.

The data indicate that until 1950, very few fish
younger than those spawned in 1943 appeared in the
lifts. Of 120 fish sampled in the fall of 1949 at Garden,
Michigan, 80.8 percent were of the 1943 year class. Of
80 fish taken from trap nets in the spring of 1949, in
Ogontz Bay, Delta county, Michigan, by Mr. Stanley
Lievense of the Michigan Department of Conservation,
92.5 percent were of the 1943 year class, and 6.2 per-
cent were of the 1944 year class. During the spring of
1950, younger fish began to show up in the catches. Of
58 fish sampled from the trap net catches in Ogontz Bay
by Dr. Ralph Hile on May 17, 1950, 79.3 percent were of
the 1943 year class and 17.3 percent were from the 1944
year class. As the season progressed, reports came in
that smaller fish were becoming more numerous. Reports

of smaller fish from Roy Jensen, a fish dealer in

- 39 -

Escanaba and Buck Lavallie of Garden, were verified by
a trap net sample taken from the vicinity of Ford River
in Little Bay De Noe on August 21, 1950. This sample
had 50 percent 1943 year class fish, 12.5 percent 1944
year class fish, 6.2 percent of 1945 year class fish,
15.8 percent fish.spawned in 1946, 12.5 percent from
1947, and 3.0 percent from 1948.

From another sample taken on the same day with the
same type of gear from the vicinity of Eseanaba, 50.0
percent were 1943 year class fish, 3.8 percent were from
the 1946 Spawning, and 46.2 percent were hatched in 1948.

lMany expressed concern during the fall of 1949, and
the spring of 1950, that the yellow pikeperch.fishery
would return to its former production level when the
1943 year class passed through the fishery. It is evi-
dent that succeeding year classes were not as successful
as that of 1943. However, fishermen contacted at Fair-
port, Michigan, report large numbers of small yellow
pikeperch appearing in small mesh gill nets set for perch
in that vicinity. On October 4 and 5, 1950, small yellow
pikeperch were taken from these gill nets. These fish
on both occasions were 100 percent of the 1949 year class.
‘Upon questioning Norbert Casey and.Nestor Seaman, both
of Fairport, reported that in 1944, similar catches of
yellow pikeperch were made in small mesh nets. They
added, however that the 1950 catches were lighter than
those of 1944.

- 30 -

On February 1, 1951, Roy Jensen of Escanaba sent
a selected sample of small yellow pikeperch to the
Sturgeon Bay headquarters. The sample had been taken
from the Escanaba area where they were mixed with pound
net smelt. Only 12 fish were received, but these were
100 percent young of the year.

From the summary of Table VIII, it can be noted
that in 1949, the 1943 year class dominated the catch
with 85.1 percent of the total catch. The 1944 year
class contributed 10.5 percent of the total production.

In 1950, however, 73.6 percent of the catch was
made up of the 1945 year class, 7.9 percent of the
1944 year class and 6.2 percent of the 1947 year class.

Table VIII is also summarized by gear. In both
1949, and 1950, pound nets took fish only of the 1943
year class or older fish. This probably is due to two
factors. These nets have 4 1/2' to 6' mesh.netting in
the backs and will allow many of the smaller fish to
escape. As a rule, they are set in more than 60 feet
of water.‘ It may also be noted that in 1950, the trap
nets caught more of the younger fish than they did in
1949. This may be due to the fact that there were
more fish of the year classes following 1943, in 1950
than there were in 1949. The large mesh gill nets took
roughly the same age class composition in both years.

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- 32 -

A 4-1/2“ mesh gill net rarely catches a yellow pikeperch
smaller‘thah 15 inches, a fish probably four years old.

Indications are that following 1943, conditions
prevented another large year class from entering the
fishery. 1944 was a more successful year than the suc-
ceeding two years. Undoubtedly, the presence of a large
number of predacious fish in a body of water results
in a minimum survival rate. It would.appear from the
limited data, that the 1947 year class was stronger
than the two years preceding it. However, escapement
of fish spawned 1a 1947, and sampled in 1950, would be
high due to the size of the commercial gear. Large mesh
gill net and pound nets with 4 1/2' backs would allow a
large number of three-year-old (12:58) fish to escape.

q;

THE 1943 YEAR CLASS

The great increase in the yellow pikeperch in.northp
ern Green Bay was caused by a very successful spawning
season during the spring of 1943. The exact reason for
the spawning success in 1943 is not definitely known.
In his article, Hile (1950) writes as follows:

I'The reason for the phenomenal hatch.of walleyes
in Green Bay in 1943, must be given as 'unknowni. Many
hold that the recent great abundance was made possible

by the mortality that all but wiped out the population

- 35 ..
of smelt in the late winter of 1942-1943. Certainly,
the timing is suggestive and the explanation is made
even more attractive by the fact that the lake herring
and the Whitefish enjoyed similar increases. **********.
We cannot ignore the possibility that the increase in
all three species was not associated at all with the
decline of the smelt but rather arose from peculiarly
favorable weather conditionsmuwus In support of
the latter interpretation I may cite the fact that
Minnesota scientists report an exceptional 1943 hatch
of walleyes in Mills Lacs where smelt could not have
been a factor." .

It is interesting to note, when examining catch
statistics, that Michigan fishermen in 1942, produced
only 16,121 pounds of yellow pikeperch. This figure
will give some idea of the size of the papulation in
northern Green Bay at the time of the spawning of the
1943 year class. The production of yellow pikeperch
in 1942, was the lowest on reliable record. These
fish, in 1943, spawned so successfully, and the fry
survived so well, that the largest production on record
resulted.

The population levels of the yellow pikeperch were
so high in 1948 and 1949, that Sportsmen took out

.. 34, ..
commercial fishing licenses and fished with hook and line.
In 1948, 20,224 pounds were produced in this manner with
a return per unit of effort of 60 pounds per man per day.
Ln 1949, the total production from commercial sport troll-
ing was 11,868 pounds and a return per man-day of 35
pounds. In 1950, few fish were caught in this manner
and immediately speculation arose to the effect that the
yellow pikeperch had disappeared. It is interesting to
note, however, that commercial production kept increas-
ing. The fact that there are fewer, but larger fish
present now than there were in 1948, may be the answer
to this paradox.

That the 1943 year class has added tremendously to
the fishery of northern Green Bay, is obvious. 1949 and
1950 samples indicate that by far the greatest percent-
age of the catch was made up of 1943 year class fish.
Data indicates that 85.1 percent of the 1949 catch was
made up of this year class. This amounts to 883,366
pounds. During 1950, 73.6 percent of the total catch
was made up of the 1943 year class. The final figure
for the 1950 production is not available, but the state
of Michigan has issued an estimate of the yellow pike-
perch production of all of Lake Michigan waters as
1,298,412 pounds. in assumption of 1,250,000 pounds

- 35 -
for the 1950 Green Bay production results in at least
920,000 pounds of the total catch made up of the fish
spawned in 1943.

It can be seen from the above data that, inspite
of the reduction in percentage of occurrence of the
1943 year class individuals in the total catch, a great-
er production in pounds has resulted. This trend will
continue as long as the annual growth in weight of fish
spawned in 1943 exceeds the weight of this year class
removed from Green Bay waters. When exploitation and
natural mortality of this year class reduce thepopulap
tion composition below the point where growth in weight
makes up the difference in production, the value of the
1943 year class to the fishery will decline. Unless
the decline is balanced by the entrance into the fish,
cry of another year class, total production will then

decline.
GROWTH OF THE YELLOW PIKEPERCH IN GREEN BAY
Tables I! and.I present growth data for the yellow
pikeperch in northern and southern Green Bay. .Although
the southern Green Bay sample is inadequate forks de-
tailed study of the growth characteristics of the yellow
pikeperch pepulation, it does indicate that the growth

rate in southern Green Bay is more rapid than that found

for the same species in northern Green Bay.

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- 39 -

calculations show that, on the average, the yel-
low pikeperch in southern Green Bay grows 25 percent
faster than in northern Green Bay. Age Class I is 32
percent larger, and Age Glass VIII is 10 percent larg-
er with the difference in length hetween northern and
southern Green Bay becoming smaller as the fish become
older.

The following table will serve to illustrate the

pointé

A COMPARISON OF TOTAL LENGTHS (BY INCHES) OF THE
"' "" Immwrlmmcs ' ’ " A I
IN NORTHERT AND SOUTHERN GREEN BAY
AGE CLASS
I II III IV -.V VI VII VIII
S. Green Bay 8.7 13.2 16.1 19.1 20.7 24.3 27.2 28.0
No Green Bay 606 1002 1208 1504 1706 1902 2004 2508
% Difference
_.1 over B 32 30 26 24 18 27 33 10
Figure 3 compares the growth characteristics from
northern and muthern Green Bay, by sex.
In southern Green Bay after the second.year or life,
the female yellow pikeperch begins to exhibit a more
rapid rate or growth than does the male. This growth
characteristic is not apparant in northern Green Bay

until the fish have reached their third growing season.
While detailed observations on the age of sexual maturity

- 4o .
in southern Green Bay are lacking, data from.northern
Green Bay indicate that 93.1 percent of three-year-
old males are immature and in the case of females,
100 percent are immature (Table XXI). Sexual maturity
is attained by 22.3 percent of the‘fish' between their
third and fourth year of life.

Tables IX through XIV, inclusive, present growth
data for yellow pikeperch from both northern and south-
ern Green Bay. Table II presents data for northern
Green Bay from all types of gear. Age Class 0 is in-
cluded in this tabulation for the sake of completeness,
but because these fish were selected for their small
size they have not been included in the grand average.

Figure 5 and Tables IX and I present detailed
growth data for Green Bay.’ As has been mentioned,
growth rates differ rather widely. The growth rate
as illustrated graphically by Figure 2 does not differ
greatly in character from those computed for the yel-
low pikeperch in other waters. Growth of the females
exceeds that of the males. This is, of course, the
usual finding for this species. Growth rates are more
rapid during the first years of life. .As the fish be-
comes older, the rate of growth declines gradually un-
till during the last years of life growth rates are very

slow. Figure 3 also shows growth increments.

- 41 -

It is interesting to examine data from individuals
older'than those Spawned. in 1945. With the exception
of three specimens, all individuals examined were se-
lected for their large size and so cannot be considered
with the growth data.

It does appear, however, that the general growth
rate in northern Green Bay before the entrance of the
1943 year class was somewhat more rapid than it is at
present. It seems 10gical that the increase in numbers
of fish since the 1943 year class could reduce the
available food supply from a previously high level and
so also reduce the rate of growth of the present popue
lation.

The almost complete reduction of the smelt from
Green Bay in 1942, may also have affected the rate of
growth of the Green Bay yellow pikeperch. Certainly,
this fish is important in the diet of this species.
Further work is necessary to confirm the supposition
that there actually has been a reduction in growth rates
of the yellow pikeperch following the entrance of the
1943 year class.

Figure 3 shows growth data for fish spawned before
1943. I These data are plotted only as points since the
author does not feel Justified in establiShing growth

rates for these age classes based on such a limited

sampling.

.. 4a -

Table I presents combined data from various types
of fishing gear for southern Green Bay.

Table XI through XIV inclusive presents growth
data by types of fishing gear for 1949 and 1950.

It may be seen in comparing these tables that be-
tween'leee and 1950, there was no significant variation
in growth rate. Neither does there appear to be a sig-
nificance in growth rate calculations (hie to net selec-
tivity. Variations in calculations are rather small,
considering the size of the sample, between fish taken
in gill nets and in trap nets.

In northern Green Bay, regulations limit the min-
imum size of the commercial catch to 15 1/2 inches in
total length. Generally, fish of this size are in their
fourth year of life. Because of variation, however,
three-year-old individuals may attain the legal minimum.
Especially slow growing individuals may not reach 15 1/ 2
inches until they are five years old.

In southern Green Bay, Wisconsin's regulations limit
the minimum size of yellow pikeperch taken commercially
to 15 inches. Because of the more rapid rate of growth
in southern Green Bay, the fish enter the fishery in
their second and third years of life.

Table IV presents a tabulation of length frequency
distribution of all fish examined. Specimens from 4 to

 

 

 

 

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.. 47 ..
6 inches in total length in Age Class 0 have been in-
cluded for completeness. They were selected for their
size. Fish taken by all types of gear are represented
in this‘tabulation.

Those fish that appear in the 9-11 inch classes
were taken largely by small meshed gill not set for
perch or herring.

It should be noted that the large number of spec-
inane-appearing in the 18-22 inch length intervals is
due largely to two causes. First, the gear used to
obtain these specimens was selective for fish above
the legal minimum; and second, the presence of the
dominant 1943 year class creates a disprOportionate
number of fish of this size.

There is a large variation in size between indi-
viduals of the same age. It may be seen in Table IV
that fish from Age Class VII range from 16.5 inches to
337.9 inches in total length. Fish 16.5 to 16.9 inches
in total length ranged from Age Class III to Age Class
VII. ‘ . . .

H The theoretical distribution of the length fre-
quencies is, in this case, unbalanced. Instead of a
large number of small individuals gradually decreasing,
as the length increases, to a point where age, fishing
pressure and natural mortalities reduce the population

hMMIY

IJIKMHFJIIQDINGI 03'055 IIILOI'PIIIEIBOEEIIDIIIOBIEIII'IIIIIIEI!
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150° " 1509
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15.5 - 15.9
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17.5 - 17.9
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19.5 - 19.9
20.0 - 20.4
m.5 - 8009
2100 " 21.4
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22.0 U 220‘
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8405 - “0’
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26.5 - 2509
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26.5 " “09
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- 49 -
to zero, there are fewer small fish, a large number of
them between 18 and 22 inches, and practically none be-
yond this point.

The selective action of fishing gear, both for
very small and very large individuals, must be recog-
nized. Large individuals are not usually taken in gill
nets, but pound nets and trap nets will take them read-
ily. It is felt that this factor is negligible in the
case of extremely large individuals. In the case of
small fish, however, the error is quite large. Only
from about 15 inches and up does Table XII represent
a true picture of the present length frequency distri-
bution.

Length-weight relationships of the yellow pikeperch
have been calculated for northern Green Bay only. There
are no data to indicate whether or not fish of comparable
lengths are different in weight in northern and southern
Green Bay. Tables XVI and XVII present lengths, weights,
theoretical weights and condition factors expressed in
both English and metric systems. The sexes are kept
separate. At no time was sampling made during the time

when the fish were in a spawning or near spawning

condition.

- 50 -f

The condition factor or coefficient of condition
has been widely used by fishery biologists to serve as
a measure of the "degree of well being” of fishes
(Hile 1936). For~purposes of comparison, both the
metric coefficient (K) and the English coefficient (0)
were computed. Alignment charts similar to those pub;
lished by Garlander (1950) were used to compute both
C and K. These values, however, were spot checked to
compare the graphical method of computation with the
arithmetic.

The condition factor generally increases with an
increase in size. The increase appears gradual and
does not show any abrupt changes at the time of sexual
maturity for either sex.

In general, female specimens averaged somewhat
heavier than males of similar size. ‘Accordingly, the
condition factor reflects this trend.

The formulae describing the lengthpweight relation.
ships for northern Green Bay were computed according to
the proceedure set forth by Beckman (1948). The compup
tations were made separately by sex since length weight
relationships show sexual differentiation. The equation
W I on“ is a general formula describing growth in weight
for any fish.

- 51 -

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- 55 -

The formula describing the growth in weight of the
male yellow pikeperch in northern Green Bay is as fol-
lows:

w - 1.9210 x 10'5L2-7118

The formula describing the growth in weight for
female fish is as follows:
= 6.6450 x 10'5L2'9247

Where weight in grams

has
n

3 standard length in millimeters

8 constant

0

n = constant

Figure 4 presents curves for these equations. The
more rapid rate of growth in length of the female fish,
as previously noted, holds true for growth in weight
also. In comparing Figures 3 and 4, it may be seen
that the length growth differential of female fish be-
comes apparent at approximately 13 inches (Figure 3).
At that same length, female fish also begin to increase
their weight at a more rapid rate (Figure 4). Generally,
then it may be said that beginning at the time of sex-
ual maturity growth differentials in length and in
weight becomes apparent between the sexes with females
showing greater growth in length and weight.

Table XVIII presents data on the calculated growth

in weight of the specimens from northern Green Bay.

- 55 ..
The annual weight increment calculations are of interest
in that they show an increase each year until a maximum
increment occurs during the fifth year of life. From
that time the increments decrease annually.

Table XII presents factors for conversion between
total length and standard length in both English and
metric systems. These factors agree within reason with
published data for yellow pikeperch.in other bodies of

water.

SEXUAL DETERMINATION

The following criteria were used for sex determin-
ation. Certain of these details were reported by Dr.
Paul Eschmeyer and are based on his observations of the
yellow pikeperch of lake Gegebie, Michigan. (Eschmeyer
1950) ' ‘

’In the case of mature fish.of either sex, the gon-
ads show either eggs or the characteristic greyishpwhite
color of the testis from September until the time of
spawning. Mature female fish show residual eggs immed-
iately after spawning until the ovaries deve10p for the
following season. Sex determination of mature males
depends on comparison of the size and color of the
testis. The testis has an opaque color and is smaller

in size than the ovary. The ovary may have a

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3: T——{§~ 2000
A 9 2
U l ..
Lu vmti 1750
: I'-
E . z
5' :2
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8 ' T—& '250
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1 4
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II

M-

l6

'8

20

22 24

TOTAL. LENGTH INo INCHES

26 28 '50 .32.

.. 59 .

Table III

FACTORS r012 CONVERSION BETWEEN TOTAL (T.L.) AND
STANDARD (S.L.) moms or GREEN BAY mow PIKEPERCH

(The Date Are Based On Fish Taken In 1950 Collections From
Different Ports And From All Major Types Of Fishing Gear)

Conversion Factor

Total Number TI. to 3.1:. 8.4... to T32.

 

 

 

Length of No Change No Change T.L. (In.) 8.1.. (Inn!)

(Inches! _Ii_s_lL of Units of M“ to 8.1.. Lani to T.L. (In.)
Below 9.9 27 1.2019 0.8320 21.1328 30.3283
10.0 - 11.4 99 1.1902 0.8402 21.3411 30.2311
11.3 - 22.0 186 1.1799 0.8473 21.3263 29.9693

A3070 22.3 20 1.1330 0 .8383 21.8008 29 .391

.. so -
pinkish color.

In immature fish, the size and shape of the gonads
is of, some use in determining sex. In fish of the same
size, the ovary is wider. The testis also tapers toward
the anterior portion and over much of its length while
the ovary tapers more abruptly.

Internally, the ovary exhibits folds when out in
cross section, while the testis appears homogeneous.

The dorsal blood vessel of the testis lies in a
groove, while the blood vessel of the ovary lies on
the surface. Cross veination may also be seen on the
ovary while generally, it is lacking or inconspicuous
on the testis.

In extremely small individuals (young of the year)
the ovary may exhibit two dark lineshslong its length .
while the testes appear as thread-like organs devoid
of pigmentation.

SEXUAL MATURITY

Only those females showing eggs forming in the
ovary were considered mature. Males were considered
mature if the testis showed the characteristic whiteish
color, during the fall, winter and early spring. Dur-
ing late spring and summer, maturity determinations are
difficult. The testis, however, increases noticeably

in size when maturity occurs.

- 51 ..

Table II contains data taken from samples made in
northern Green Bay. About one half of the male yellow
pikeperch are mature by the time they reach 15 1/2
inches. None of the females examined were mature at the
15 1/2 inch legal minimum length. Males mature at a
smaller size than do females. 100 percent of the males
were mature by the time they were 19 inches in total
length. The females were not all mature until they had
reached a total length of 21 inches. Table XVI gives
the length interval and the percentage of maturity by

sexes for northern Green Bay.

- 52 -
GROWTH IN OTHER WATERS

Many authors have described the growth rates of
the yellow pikeperch Stizostedion vitreum vitgeum
(Mitchill) in various bodies of water. Generally, it
may be said that the population for every body of water
described differs in growth rate from every other. It
can be seen.from Figure 5 that growth.rates vary great-
1y from that of Lake ibitibi, Ontario, Hart (1928) to
that of Norris Reservoir, Tennessee, Stroud (1948}.

The Green Bay yellow pikeperch is one of the fast-
est growing fish studied to date. Stroud (1949) reports
the growth rates from Norris Reservoir, Tennessee, as
being more rapid. The only other reported data avail-
able indicate that the yellow pikeperch of Bass Lake,
Wisconsin, Schloemer and Lorch (1942), grows more rapid-
ly than does the same species in Green Bay.

Table XXI compares published data with that com-
puted for northern and southern Green Bay. Figure 5
presents this data graphically.

Tables.XXII and XXIII present unpublished data
from Dr. Ralph fiile on the Saginaw Bay yellow pikeperch.
This material was not included in Table m because it
presents growth data in more detail than is possible in

Table XXI, and because for purposes of comparison,

-63..

Table I!

SEXUALIMATURITY 0F YELLOWIPIKEPERCHI
IN NORTHERN GREEN BKY

 

 

 

Isles
Wer
Total Number Number or 01‘ Percentage
Length Of Inmature Mature 01"
Inches Specimens Fish Fish Meturit
4.0 - 12.9 74 74 0 0.5
13.0 - 13.9 29 27 2 6.9
14.0 - 14.9 24 17 7 29.2
15.0 - 15.9 22 12 10 43.5
17.0 - 17.9 30 3 22 88.0
18.0 - 18.9 39 0 59 100.0*
Females
4.0 - 16.9 122 122 0 0.0
17.0 - 17.9 V 4 2 2 50.0
18.0 - 18.9 12 1 11 83.3
19.0 - 19.9 33 2 33 94.3
20.0 .. 20.9 139 0 139 100.0

l“One mle yellow pikeperch 21.9” total length appeared to be inmature

 

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1‘ -~~ ' ' i~< , 1 SUMMARY OFAVEQAGE

.’ GROWTH 'RATES.

7L- YELLOW P1KEPERCH

x . a m

' 1 ‘1 VARIOUS WATERS
LlEéEMD‘

 

NORTH GREEN BAY- BALCH
SOUTH GREEN BAY - BALCH
.~ ______ NORRIS' RESERva-TENN: STROUD
4 LAKE ABITIB\-CANADA~HART-1928
5 LAKE NIPIGON-CANADA- HART-1928
. z. - LAKE WINNipEG-CAHADA- BAJKOV-
“ 1 ' 7 -o——o— LAKE OF THE WOODS-M1MN.CARLAUDER

‘ s

9

 

 

 

1
"’ '77 3 1' ‘ a
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4 7 1 . : _,__ —--—- aAss LAKE— wss: scHLOEMEB¢Lor2CH
3 1 “-0. no _—— TROUT LAKE- Wis-ScuLOEMEn¢’ Loam-x
1 1 1 n —_-.-- LAKE ERIE ~ ADAM sTouE- 1922
2 >7 . 1 * r |z -.___- LAKE ERIE - DEASOH - I955
. __ _ . .1 _ \25 0—0- LAKE eOGEBlC-Mlcfi. ESCHMEYER-lgso

 

I n m w v vr vu mm W x X1. xu ym yuv xv
AGE - m YEARS-

- 55 -
Saginaw Bay; more than any other body of water, closely
resembles Green Bay in physical and biolOgical charac—
ters.

'Until the fifth year of life in the case of male
yellow pikeperch, Saginaw Bay and northern Green Bay
growth characteristics are similar. In the case of
females, growth rates are very close antil the sixth
year. After this time, the growth rates in Saginaw Bay
for both sexes SlOW'up more rapidly than in the case
of northern Green Bay. .A8 a result, the older fish in
northern Green Bay are longer than in Saginaw Bay.
Comparisons are made upon the growth rates computed
since 1950.

Tables XVIII and XXIII contain data on the weights
of yellow pikeperch.from Saginaw Bay and Green Bay.

‘A marked difference is apparent between the weights
of northern Green Bay and Saginaw Bay yellow pikeperch
of comparable age. Saginaw Bay specimens average heave
ier than the northern Green Bay fish of the same age
all through life. It should be stated that the size of
the sample in northern Green Bay of fish older than.Age
Class VII is small and is influenced by a large percent-
age of larger than average rim.

- 67 -D

lkflilo JDEII

COIRKRISON O? EINGEEB (INCEE§) A! DIFTERENT
.Aflflfl 0? YIELOUWPIKIEERGHIGKUGHP IN SAGINIH BK!
IN 1926-1930 AND 1943

130 Miles limeles
in - - -
You. 1930 m 1930 1943
1 6 C 7 6 0‘ 6 O 9 6 0‘
2 10.7 12.0 10.9 12.0
3 13.4 15.8 13.8 16.3
4 15.3 18.1 16.0 18.9
6 16.6 19.6 17.8 21.3
6 17.6 20.6 19.3 22.9
7 18.3 21.6 20.3 24.3
8 18.9 21.9 21.0 25.4
9 19.6 22.7 21.7 26.3
10 20.0 23.3 22.3 27.3
11 22.9 27.9
18 23.5 28.8
13 24.0 29.5

-68..

Table XXIII

CMARISON OF WEIGHTS (POUNDS) AT DIFFERENT
A. 01' YELLOW PIKEPERCH CAUGHT IN SAGINAW BAY
IN 1926-1930 AND 1943

Age Males Females
in 1926- 26-

Yeare 1930 1943 1930 19:55.

0.09 0.08 0.10 0.08
0.57 0.52 0.59 0.52
0.71 1.18 0.81 1.29
1.06 1.76 1.26 2.04
1.36 2.25 1.74 2.96
1.61 2.69 2.21 5.75
1.85 5.05 2.60 4.55
2.05 5.55 2.94 5.18
2.25 5.69 5.29 5.77
2.45 4.00 5.62 6.41

HP |-
ampoomqaapamp

3.91 6.86
4.23 7.53
4.50 8.14

- 69 -

Growth rates in waters located in a comparable
geographical location do not show the rapid growth of
the Green Bay population. Yellow pikeperch from
Canadian Lakes described by Hart (1928) and Bajkov
(1930), the Minnesota Lakes and streams as described
by Eddy and Carlander (1939), Lake Erie, Adamstone (1922)
and Deason (1935), Lake Gogebic, Michigan, Eschmeyer
(1950), and work done on northern‘Wisconsin lakes
(Schloemer and Lorch, l942) all have growth rates

somewhat slower than that of Green Bay.

-70-

SUMMARY

Although the yellow pikeperch Stizostedion vitreum

 

vitreum (Mitchill) of Green Bay is not the most im-
portant commercial Species, either in pounds produced
or in value, it does rank among the most important
species in northern Green Bay. Northern Green Bay pro-
duces the bulk of the yellow pikeperch taken from Lake
Michigan waters.

The yellow pikeperch p0pulations of northern and
southern Green Bay are apparently discrete p0pulations.
Factors causing fluctuations in numbers do not seem to
affect both regions in the same way. Growth rates dif-
fer rather widely. Physical and biological character-
istics are quite different in northern and southern Green Bay.

The recent production of yellow pikeperch in northern
Green Bay has been greatly affected by the presence of a
dominant year class spawned in 1943. Samples taken in 1949
indicate that 85.1 percent of the commercial harvest was
made up of the 1943 year class. In 1950,.73.6 percent
of the estimated annual production was made up of this
year class. A combination of increased fishing pressure
(403 percent of the 1929-1943 average) and increased
abundance (282 percent of the 1929-1943 average)

have resulted in an increased harvest (1126 percent

- 71 -
of the 1929-1945 average).

The period of greates:production occurs during the
months of May and June when approximately 50 percent
of the annual catch is made. September and October are
also periods of increased yield when about 25 percent
of the annual production is taken.

The fyke net produces the largest amount of yellow
pikeperch as well as the highest return per unit of
effort in northern Green Bay; In southern Green Bay,
the seine produces the largest return per unit of effort,
but the least production of the commercial gear operb
ated. The fyke net in southern Green Bay produces the
greatest percentage of the annual harvest but has the
lowest return per unit of effort.

Growth rates were computed for northern and south-
ern Green Bay. Growth rates in length and weight of
female yellow pikeperch are more rapid than those of
the males. Growth rates (sexes combined) in southern
Green Bay'exceed those found in northern Green Bay by
approximately 25 percent.

Fbr female yellow pikeperch in northern Green Bay,
the formula describing the growth in weight is as fol-
lows:

w: 6.6450 x 10-51209247

For males it is:
‘ w = 1.9210 x 10-5L2-7118

- 73 -
Weight increments increase annually until the sixth
year of life and then decrease gradually.

Sex determination, though easily determined in
the case of adults, requires close examination in the
case of immature fish. The size of the gonades, the
ovary being larger, as well as the cross veination of
the ovary, aid in determining sex. A transverse sec-
tion of the gonad reveals the ovary to be hollow with
folds, while the testis is solid.

Sexual maturity for male yellow pikeperch occurs
in 45.5 percent of the Specimens studied at 15 inches
(total length). In the case of females, none were
found mature at 15 inches. Fifty percent were mature
by the time they had reached 18.9 inches. Females
were 100 percent mature at 20.9 inches. -

The Green.Bay yellow Pikeperch population is one of
the most rapidly growing populations on record. Growth
rates in Norris Reservoir, Tennessee, and possibly Bass
Lake, Wisconsin, are the only known populations that

exceed the rate of growth in Green Bay.

- 73 -
LITERATURE CITED

Adamstone, F.B.

1922 Rates of growth of the blue and yellow
pikeperch (ggizostedion vitreum) in Lake
Erie. Univ. of Toronto Studies No. 20.
Pub. Ont. Fish. Res. Lab. No. 5. pp. 77-86.

Bajkov, Alexander
1930 Fishing industry and fisheries investi-

gations in the prairie provinces. Trans.
Am. Fish. Soc. Vol. 60. pp. 215-237.

Beckman, Wm. C.

1948 The length-weight relationship, factors
for conversion between standard and total
lengths, and coefficients of conditions
for seven Michigan fishes. Trans. Am.
Fish SOC. 75. pp. 237-2560

Carlander, Kenneth D.
1945 Age, growth, sexual maturity, and popula-
tion fluctuations of the yellow pike-perch
Stizostedion vitreum vitreum (Mitchill)
with reference to the commercial fisher-
ies, Lake of the Woods, Minnesota. Trans.
Am. Fish. Soc. 73. (1943). pp. 90-107.

1950 Handbook of freshwater fishery biology. Wm.
C. Brown Company, Dubuque, Iowa. 281 pp.

Deason, Hilary J.
1933 Preliminary report on the growth rate, dom-
inance, and maturity of the pike-perches
(Stizostedion) of Lake Erie, Trans. Am.
F1811. SOC. V010 630 Pp. 348-3600

Eddy, Samuel, and Carlander, Kenneth
1939 The growth rate of wall-eyed pike (Stizo-
stedion vitreum vitreum (Mitchill) in var-
ious lakes of Minnesota. Proc. Minn. Acad.
Sci. Vol. 7. pp. 44-48.

Eschmeyer, Paul H.
1950 The life history of the walleye, Stizostedion
vitreum vitreum (Mitchill), in Michigan.
Bull. of the Inst. for Fish. Res. No.
3 Mich. Dept. of Cons. 99 pp.

 

- 74 -

Hart, John L.
1928 Data on the rate of growth of the pike
erch (Stizostedion vitreum) and Sauger
S. canadense) in Ontario Univ. of
Toronto Studies No. 31 Pub. Ont. Fish.
Res. Lab. No. 34.

Hile, Ralph
1936 Age and growth of the Cisco, Leucichthys
Artedi (Le Sueur) in the lakes of the
northeastern highlands, Wisconsin. Bull.
U.S. Bur. Fish., Vol. 48. 317 pp.

 

1937 The increase in the abundance of the yel-
low pike-perch, Stizostedion vitreum (Mit-
chill) in Lakes Huron and Michigan, in
relation to the artificial propagation of
the species. Trans. Am. Fish. 800., Vol.
66.

1950 A nomograph for the computation of the
growth of fish from scale measurements.
Trans. Am. Fish. Soc., Vol. 78.

Hile, Ralph
1950 Facts on walleye fishing. The Fisherman,
March 1950.

Hile, Ralph and Jobes, Frank W.

1942 Age and growth of the yellow perch, Perca
flavesuns (Mitchill) in the Wisconsin
waters of Green Bay and northern Lake
Michigan. P0p. Mich. Acad. Sci. Arts. and
Letters 27. pp. 241-266.

Hubbs, Carl L. and Lagler, Karl F.
1947 Fishes of the Great Lakes Region. Cranbrook
Inst. of Sci., Bull. No. 26. xi / 186 pp.

Lagler, Karl F.
1949 Studies in fresh water biology. Ann Arbor
Press. 231 pp.

Lindeborg, R. G.

1941 Records of fishes from the Quetico Provin-
cial Park of Ontario with comments on the
growth of the yellow pikeperch. COpeia
N00 30 pp. 159-1610

MacKenthun, Kenneth M.

1946

A preliminary report on the age, growth
and condition factor of southern Wisconsin
fishes. Wis. Cons. Dept. Div. Fish.

Mgt. Invest. Rept. No. 574. 17 pp.

Schloemer, Clarence L., and Ralph Lorch

1942

The rate of growth of the wall-eyed pike
(Stizostedion'l. vitreum (Mitchill) in
Wisconsin's inland waters with Special ref-
erence to the growth characteristics of

the Trout Lake p0pulation. Copeia No. 4.
pp. 201-2110

Stroud, Richard H.

1949

Growth of Norris Reservoir walleye during
the first twelve years of impoundement.
Jour. Wildlife Management. Vol. 13, No.
2. PP. 167-177.

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