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LIBRARIES

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3 93 00897 8581

This is to certify that the
thesis entitled
POPULATION DYNAMICS AND MOVEMENT
OF LAKE WHITEFISH IN OUTER SAGINAN BAY, LAKE HURON

presented by

Susan Harris Walker

has been accepted towards fulfillment
of the requirements for

M.S. degree in Fisheries & Wildlife

 

 

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Date March-29, 1993

 

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TO AVOID FINES return on or before date due.

    

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MSU Is An Affirmative Action/Equal Opportunity Institution
ommS-od

POPULATION DYNAMICS AND MOVEMENT
OF LAKE WHITEFISH IN OUTER SAGINAW BAY, LAKE HURON

By

Susan Harris Walker

A THESIS

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

MASTER OF SCIENCE
Department of Fisheries and Wildlife

1992

ABSTRACT
POPULATION DYNAMICS AND MOVEMENT
OF LAKE WHITEFISH IN OUTER SAGINAW BAY, LAKE HURON
By

Susan Harris Walker

Lake Whitefish are harvested commercially from large and small-mesh trap nets
throughout Saginaw Bay. This study was conducted to determine the size of the
Saginaw Bay lake Whitefish population, document movement patterns, and estimate
population parameters. A mark-recapture study was conducted to determine both the
movement patterns of the tagged fish and to obtain estimates of population size. The
commercial catch was periodically assessed to determine age and size composition,
age at sexual maturity, and growth rates. Tag returns indicated that this population is
migratory, unlike most other Whitefish studied. This finding invalidated most of the
assumptions Of the Petersen mark-recapture estimator, making estimates of population
size unreliable. However, the Observed age and size compositions, and mean age at
maturity in the catch indicate that the population is experiencing a low level Of

exploitation.

ACKNOWLEDGEMENTS

Although there is only one author listed on the title page of this thesis, there
are many others who contributed their sweat, brains and patience to make this study
possible. First, I would like to thank those men and women who work so. hard in
every kind of weather to bring food to our tables, the commercial fishermen. Special
thanks go to Tod, Randy, and Denny of the Bayport Fish Company, to Walt
Opensenko, and to those fishermen on the other side of the Bay - Sandy Whyte, Bill
Lentz and Dick Beardsley, for putting up with biologists on their boats and sharing
their coffee and stories of the lake. The Bayport Fish Company, under the watchful
eye of Forrest Williams, was instrumental in suggesting, funding and conducting this
study. My fellow graduate students were almost always supportive, and were
sometimes cajoled into assisting me in the cold, wet and slimy business of Whitefish
catch assessment and tagging. To those who now know that there is little finer than a
day on the lake in November - thanks! This includes Bob Sluka, Glenn Bamer and
Cliffena Yellowfox, Paola (what are the big green fish?) Ferreri, Michaela (I hope I
don't fall in, Sue I'm freezing) Zint, Russ (you're going to tag Mm fish today?)
Brown, Steve Marod, and Tim Watkins. There were also many undergraduates who
were "convinced" to assist me under the promise of obtaining field experience (and

never came back again), thanks also go to them. To Heather Sizek I owe a deep

ii

gratitude for she quickly, accurately and uncomplainingly aged hundreds of lake
Whitefish scales when I was unable to find any time to do so. Thanks also go to my
committee members, Tracy Dobson, Esq. for pulling me OI'It of the Natural Resources
basement and teaching me the basics of law in our society, to Dr. Scott Winterstein
who found courses for me to T.A. after my funding evaporated and even helped me in
the field (November 7, 72°F, sunshine), and to Dr. Bill Whitefish Taylor whose

interest in Great Lakes fisheries made all of this possible.

iii

TABLE OF CONTENTS

BESS
List of Tables .......................................... vi
List of Figures .............................. A ........... vii
Introduction ............................................ 1
Objectives .............................................. 6
Study Area .............................................. 6
Methods ................................................. 8
Length and Weight .................................. 8
Sex and Maturation ................................. 10
Age and Growth ..................................... 10
Movement Patterns .................................. 11
Abundance and Biomass .............................. 14
Optimal Yield ...................................... l7
Resu1ts ................................................. 17
Length and Weight .................................. 17
Sex and Maturation ................................. 21
Age and Growth ..................................... 26
Abundance and Biomass .............................. 32
Movement Patterns .................................. 36
Yield .............................................. 44
Discussion .............................................. 46
Literature Cited ........................................ 55

iv

Appendix B .............................................. 62

Appendix C .............................................. 64

LIST OF TABLES

Table

Whitefish sampling dates, locations, gear types,
and measurements taken, 1989 - 1991 ................

Location and number of lake whitefish tagged from
trap nets in Saginaw Bay, Lake Huron, during 1989
and 1990 ...........................................

Mean weights at age of all lake whitefish sampled
from large and small trap nets in Saginaw Bay, Lake
Huron during 1989, 1990 and 1991 ...................

Mean lengths at age of all lake whitefish sampled
from large and small trap nets in Saginaw Bay, Lake
Huron during 1989, 1990 and 1991...., ..............

Mean lengths at age of lake whitefish sampled
during spring, summer and fall of 1991 from deep-
water trap nets set in the whitefish permit area
in outer Saginaw Bay, Lake Huron ...................

1989 and 1990 biomass and abundance estimates for
Saginaw Bay (Lake Huron Management Zone MH4)
calculated from the Petersen mark-recapture
estimator ..........................................

Numbers of lake whitefish tagged, double- tagged,
and returned from all fall tagging locations during
1989 through 1991 ..................................

1990 yield estimates for Saginaw Bay lake whitefish
at F = 0.60 ........................................

1991 yield estimates for Saginaw Bay lake whitefish
at F = 0.60 ........................................

vi

Page

13

15

19

2O

22

35

39

47

48

LIST OF FIGURES

Figure Page
1. Saginaw Bay lake whitefish harvest, 1885 through

1991 ............................................... 2
2. Study area including management grids, Saginaw

Bay, Lake Huron .................................... 5
3. Back-calculated lengths at age for cohort and catch

curve samples of lake whitefish collected from the
commercial trap net harvest in Saginaw Bay, Lake
Huron during 1989 (n=536, 95% confidence intervals

indicated by bands) ................................ 9
4. Lake whitefish tagging sites, Saginaw Bay, Lake

Huron .............................................. 12
5. Mean weights at age of lake whitefish sampled from

trap nets throughout Saginaw Bay during 1989, 1990

and 1991. Line represents the regression of mean
weight at age on 1n age (weight = 1.95 - 1.93

(ln age)) .......................................... 19

6. Mean lengths at age of lake whitefish sampled from
trap nets throughout Saginaw Bay during 1989, 1990
and 1991. Line represents the regression of mean
lengths at age on ln age (length = 119.83 + 225.82
(1n age)) .......................................... 20

7. Mean lengths at age of lake whitefish sampled from
large-mesh trap nets in the whitefish permit area
of Saginaw Bay during spring, summer and fall of
1991. Line represents the regression of mean
lengths at age on ln age (length = 76.22 + 234.57
(ln age)) .......................................... 22

8. Sex composition of lake whitefish sampled from trap
nets throughout Saginaw Bay, Lake Huron during 1989
(n=415), 1990 (n=402) and 1991 (n=786). Horizontal
lines indicate annual overall sex composition ...... 23

9. Percent of sexually mature lake whitefish at age
from samples collected from the large and small-
mesh trap net fisheries of Saginaw Bay, Lake Huron
during 1989, 1990 and 1991 ......................... 24

vii

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

Percent of sexually mature lake whitefish at age

from samples collected from the large-mesh trap

net fishery in the whitefish permit area of outer
Saginaw Bay, Lake Huron during 1991 ................ 25

Percent at age composition of lake whitefish

sampled from large and small-mesh trap net

fisheries throughout Saginaw Bay during 1989, 1990

and 1991 ........................................... 27

Age composition of lake whitefish sampled from
large-mesh trap nets in the whitefish permit area

in outer Saginaw Bay during summer in 1989, 1990

and 1991 ........................................... 29

Age composition of lake whitefish sampled from
small-mesh trap nets at Bayport Islands in inner
Saginaw Bay during 1989, 1990 and 1991 ............. 30

Age composition of lake whitefish sampled from
large-mesh trap nets in the whitefish permit area

in outer Saginaw Bay during spring, summer and fall

of 1991 ............................................ 31

Age composition of lake whitefish sampled from large-
mesh trap nets in the whitefish permit area in outer
Saginaw Bay during summer and fall 1989 ............ 33

Tags returned in 1990 and 1991 with known recapture
locations from tagging conducted during spring 1990
near Au Gres, Sand Point, and the whitefish permit

area of sub-legal sized lake whitefish ............. 37

Tags returned in 1990 and 1991 with known recapture
locations by Canadian commercial fishermen ......... 38

Tags returned in 1990 and 1991 with known recapture .
locations from tagging conducted during the fall of
1989 in the whitefish permit area .................. 41

Tags returned in 1990 and 1991 with known recapture
locations from tagging conducted during fall 1989
and fall 1990 at Sand Point ........................ 42

Tags returned in 1990 and 1991 with known recapture
locations from tagging conducted during fall 1989
and fall 1990 at Bayport Islands ................... 43

Tags returned in 1991 with known locations from
tagging conducted during fall 1990 near Au Gres.... 45

viii

INTRODUCTION
Commercial fisheries were established in Saginaw Bay during the 18303
(Lanman 1839). The first fishing gears used on the Bay were spears, seines, and gill
nets and the fisheries were concentrated near shore and in major tributary rivers.
Late in the 19th century as steam power replaced sail power, fishermen moved
further from shore and began using pound nets, baited hooks, and trap nets (Hile and
Buettner 1959).

The Bay’s fish community remained stable until the 19303, except for the
deliberate eradication of lake sturgeon Acipenser fulvescens, and introduction of the
carp Cvprinus carpio (Hile and Buettner 1959). Lake herring Coregonus artedii was
the predominant species sought by the commercial fishery, yielding annual harvests
ranging from one to eight million pounds (Baldwin et al. 1979). Walleye
Stizostedion vitreum, yellow perch Perca fulvescens, and suckers (Catostomus
commersoni and Moxostoma spp.) were also abundant, each providing annual
catches of almost one million pounds.

Records of the lake whitefish Coregonus clupeaformis harvest in Saginaw
Bay began in 1885 (Figure 1), although information on fishing effort was not

collected. During the period of 1891 - 1904 the catch had no clear trend, harvests

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ranged from 92,000 to 436,000 pounds, averaging about 200,000 pounds annually.

No reliable records exist for the period from 1909 - 1915. An exceptionally high
catch of 1,203,000 pounds was landed in 1916. After 1916 the catch began to
fluctuate drastically, and during the period of 1926 - 1929 the average annual
harvest rose to 457,000 pounds. From 1930 to 1932, the average harvest increased
to 1,818,000 pounds, and a record harvest of 2,463,000 pounds was landed in 1932.
Harvest declined to an average of 291,000 pounds from 1933 - 1937, and fell off
further to an average of 26,000 pounds from 1938 - 1945. This was followed by
another sharp rise in harvest averaging 807,000 pounds during 1946 - 1948. This
increase in harvest was attributed to the large year class of 1943 (Hile et a1. 1953).
During the 19503, lake whitefish harvests declined to all-time lows, with harvests
ranging from less than 1,000 pounds to 21,000 pounds.

The 19503 coincided with the expansion of several non-indigenous species
including sea lamprey Petromvzon marinus, which preyed upon the lake whitefish,
and alewife Alosa pseudoharengus and rainbow smelt Osmerus mordax, which may
have competed with lake whitefish for forage and preyed upon juveniles (Christie
1974). Over-exploitation was also implicated in the declining abundance of lake
whitefish and other species. Heavy exploitation during the 19303 apparently resulted
from the use of deep-water trap nets with pots constructed entirely of small meshes
(2.5 - 3 inches, stretched measure) resulting in heavy mortalities of juvenile fish

(Van Oosten et a1. 1946).

Fishing effort was reduced by a ban on gill nets and a reduction of the

4

number of commercial licenses in the 19703. Sea lamprey control efforts also began
in the 19703, and whitefish stocks started to rebound. Catches increased slowly
throughout the 19703, and have continued to increase throughout the 19803 and early
19903 (Figure 1; MDNR unpublished data).

The Michigan Department of Natural Resources established a new fishery
policy in 1966 making the development of recreational fisheries the primary
management goal for the Great Lakes. Commercial fishing was downgraded to a
become a secondary, and decreasing, resource use (Keller et al. 1987). This effected
the commercial fisheries in Saginaw Bay by reducing the number of licensees from
45 in 1970 to 27 in 1986, and by removing Walleye and lake trout from the list of
commercially harvestable species. The commercial fishery was further regulated by
establishing designated fishing areas, specifying allowable gear dimensions, closing
seasons for some species, and setting catch quotas for others. Gill nets, which were
traditionally used to harvest both lake whitefish and lake trout, were outlawed in
1972 and gradually were replaced by less lethal trap nets, which had been modified
to allow non-target and game species to be returned alive to the water.

The history of unstable lake whitefish harvests from Saginaw Bay in
particular and the Great Lakes in general provided the basis of concern which led to
this study. The Bayport Fish Company owners and fishermen have been harvesting
lake whitefish with large-mesh deepwater trap nets in a designated area of outer
Saginaw Bay (Whitefish Permit Area, Figure 2), under the auspices of a fisheries

research permit issued by the Michigan Department of Natural Resources, since

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Figure 2. Study area including management grids, Saginaw Bay, Lake Huron.

6

1978. Their concern about the future stability of the whitefish populations they were
harvesting led them to arrange for this study of lake whitefish population dynamics

and stock movement.

OBJECTIVES
The primary objectives of this study are to determine for Saginaw Bay lake
whitefish, the population’s age, sex and size structure, to estimate the population’s
abundance and biomass, to calculate Optimal yield, and to document movement

patterns from the results of a mark-recapture study.

STUDY AREA

Saginaw Bay is an 82 km long inlet of southwestern Lake Huron on the
Michigan shoreline. It is nearly equally divided into inner and outer bays by a
broad shoal between Charity Island and Sand Point (Figure 2). The Bay’s 2,960
km2 of surface area compose 5% of the total surface area of Lake Huron. The
periphery of the shallow inner Bay is mainly marshlands, and the mean inner Bay
depth is 4.7 m. The maximum depth of the inner Bay is 14 m. The inner Bay is
highly productive and enriched, but polluted by industrial, domestic, and agricultural
waste and runoff. The Saginaw River is the major tributary to Saginaw Bay, it
drains a large industrial-urban complex (16,833 kmz) and is the primary source of
the Bay pollutants (Beeton et al. 1967). Due to frequent mixing of the shallow

water column by wind and a flushing rate of 186 days (Beeton et al. 1967),

7

dissolved oxygen levels are usually adequate for many warm-water fish species
(Keller et al. 1987). Waters of the inner Bay rarely stratify. Ice cover on the inner
Bay usually forms by late November and breaks up by mid-March.

The outer Bay has a mean depth of 15.6 m and a maximum depth of 40.5 m.
Seventy percent of the Bay’s total volume is contained in the deeper outer Bay
(Beeton et a1. 1967). The outer Bay’s periphery contains few marshes, rocky shores
are predominantly found on the east side and sand beaches line much of the western
shore. Outer Bay water mixes with Lake Huron proper, resulting in dissolved
oxygen conditions of nearly 100% saturation during summer stratification (Keller et
al. 1987) and abundant cold water fish populations.

The Bay has several small islands including the Charity Islands in the central
outer Bay, three islands south of Sand Point (North, Heistennan, and Maisou
Islands) which enclose shallow Wildfowl Bay. A distinctive feature of the Bay’s
bathymetry is the Coryeon Reef, a shallow sand and gravel bar stretching nearly the
entire length of the Bay in a north-eastern direction.

The harvest of lake whitefish in Saginaw Bay is divided into two fisheries,
the large mesh trap net. fishery of the Whitefish Permit Area in the outer bay, which
targets lake whitefish, and catch incidental to the harvest of yellow perch and catfish
from small mesh trap nets set in the inner bay. The inner bay incidental lake
whitefish harvest is seasonal, with peak harvests during early spring and late fall
coinciding with congregations of lake whitefish on shoals during spring when water

temperatures are unitherrnally cool, and similar shoal crowding during the fall

8

spawning season (Scott and Crossman 1975).

Commercial fishing for lake whitefish within the Whitefish Permit Area is
permittted during the period from January 1 to October 31 and December 1 to
December 31 with the following restrictions on seasonal use of gear. Up to ten
large mesh trapnets (pot mesh not less than 11.43 cm)or nine large mesh trap nets
and one small mesh menominee trap net may be fished from January 1 through June
30, from September 26 through Occtober 31, and from December 1 throngh
December 31. From July 1 through September 25, no more than five large mesh
trap nets or four large mesh trap nets and one small mesh menominee trap net may
be fished. These permit terms are subject to annual renewal and revision of specific

provisions.

METHODS

Length and Weight

Net run samples of the commercial catch (all legal and sub-legal lengths
included) were assessed seasonally for length, weight, sex, maturation, and age
information during the summer of 1989 through the fall of 1991 (Table 1). Total
length was measured to the nearest millimeter, and weight was measured to the
nearest 25 grams during 1989 and spring of 1990 using a spring balance, and to the
nearest gram beginning in the summer of 1990 using a more precise electronic
balance. When rough lake conditions prevented accurate weighing, net run samples

were brought to shore and measured.

LENGTH (mm)

 

800 _.

COHOFIT

700 '-

 

600 '-
500 '-
.400 —
300 -
200 - .

.100 -

 

600 —

700 —

500-

400 —

300-

200 ‘-

100 '-

 

 

 

AGE

Figure 3. Back-calculated lengths at age for cohort and catch curve samples of
lake whitefish collected from the commercial trap net harvest In Saglnaw Bay,
Lake Huron during 1989 (n=536, 95% confidence Intervals lndlcted by bands).

10

Sex and Maturation

Samples were classified as either immature or mature based upon gonadal
development, including size of ovaries, eggs and testes. Sex and maturation were
determined by visual examination of the gonads. Samples collected during the
spawning season were further classified as either "Ml", ripe, or spawning. Mature
females were described as "M1" if small ovaries with few mature eggs were
observed, indicating that this was the first spawning season for that particular fish.
Female fish were described as "ripe" if their eggs were mature but not yet loose in
the ovary. "Spawning" was used to describe mature female fish whose eggs were
easily expressed. Male fish were not as easily classified due to the variation in
testes size. Mature male fish can be generally described as having relatively large
testes compared to the thin, string-like gonads of immature fish, although it was
impossible to determine the first year of maturity for male fish. During the

spawning season, mature male fish were considered ripe if milt was easily expressed.

Age and Growth

Scales from sub-samples of the weighed and measured fish were removed
from the left side of the fish in the area between the lateral line and the anterior
portion of the dorsal fin. Ages of whitefish were determined from the collected
scales by counting the annuli of projected scales (van Oosten 1923). Age
determinations were made by the author and an assistant and were checked for

accuracy by comparing the results each obtained. Age determinations were also

11

compared to the results obtained by another experienced scale-reading technician.
Measurements of the distances between the focus and each annuli on scale
samples collected during spring of 1989 were used to back-calculate lengths at age
(Carlander 1981; Smale and Taylor 1986). The Fraser—Lee back-calculation method 4
was used to estimate back-calculated lengths at age for catch curve and cohort

samples (Figure 3).

Movement Patterns

Whitefish were captured from trap nets set at or near spawning locations
during the fall of 1989 and 1990 (Figure 4) and tagged with serially-numbered Floy
anchor tags (FD-68B). Tagging occurred during the November spawning closure
and was, completed by 14 November. The fish were brought to the surface in trap
nets, removed with dip nets and placed in aerated tanks on deck. Individual fish
were removed by hand from the tanks, quickly measured, examined for sea lamprey
wounds, tagged and then released back into the lake. Only fish in good condition
were tagged, using a fabric-gun applicator to place the T-bar anchor between the
intemeural bones of the dorsal fin. Fish which were judged to be in poor condition
were returned to the lake untagged. Tags were inserted at the anterior edge of the
dorsal fin on the fishes’ left side after removal of a few scales from the insertion
site. A randomly chosen sub-sample of fish were similarly marked and a second tag
was placed at the posterior edge of the dorsal fin on the right side of the fish.

During November of 1989, 2,500 fish were tagged, and 2,351 fish were tagged in

12

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13

Table l. Whitefish sampling dates, locations, gear
types, and measurements taken, 1989 - 1991.

 

 

 

NUMBER

DATE SAMPLED LOCATION GEAR? MEASUREMENTSb
1989

07-18 151 Permit Zone TN-L 1, 2, 3, 4, 5
08-01 144 Permit Zone TN-L 1, 2, 3, 4, 5
08-09 104 Permit Zone TN-L l, 2, 3, 4, 5
10-20 101 Heisterman Is. TN-S 1, 2, 3, 4, 5
10-20 106 Permit Zone TN-L 1, 2, 3, 4, 5
10-30 86 Permit Zone TN-L 1, 2, 3, 4
10-30 100 Heisterman Is. TN-S 1, 2, 3, 4
1990
05-03 126 Permit Zone TN-L 1, 2, 3, 4
05-31 90 Permit Zone TN-L 1, 3

05-31 199 Permit Zone TN-L 1, 2, 3, 4,
05-31 110 Permit Zone TN-L l, 2, 3, 4
05-31 48 Permit Zone TN-L 1, 2, 3

06-11 64 Permit Zone TN-L 1, 2, 3, 4
07-10 78 Permit Zone TN—L 1, 2, 3

07-24 134 Permit Zone TN-L 1, 2, 3, 4
08-16 29 Permit Zone TN-L 1, 2, 3, 4
10—16 58 Masiou Is. TN-S 1, 2, 3, 4
10-30 66 Sand Point TN-S 1, 2, 3, 4
10-30 69 Heisterman Is. TN-S 1, 2, 3, 4
11-08 148 Au Gres TN—S l, 2, 3, 4
1991

04-25 104 Permit Zone TN-L 1, 2, 3, 4, 5
05-16 100 Permit Zone TN-L 1, 2, 3, 4, 5
05-20 99 Bay City TN-S 1, 2, 3, 4
06-20 113 Permit Zone TN-L 1, 2, 3, 4
07-02 103 Permit Zone TN-L 1, 2, 3, 4
07-03 100 Permit Zone TN-L 1, 2, 3, 4
09-28 41 Pt. Austin TRAWL 1, 2, 3, 4, 5
10-11 48 Permit Zone TN-L 1, 2, 3, 4
10-11 21 Sand Point TN-S 1, 2, 3, 4
10-11 86 Masiou Is. 'TN-S 1, 2, 3, 4

 

aTN—L = deepwater large—mesh trap net, TN-S = shallow small-
mesh trap net, TRAWL = 39’ bottom trawl
b1 = length, 2 = weight, 3 = scales, 4 = sex and maturity,

5 = annular measurements

‘I

 

14
November 1990 (Table 2).

During March and April of 1990, sub-legal size (<19") whitefish were tagged
using smaller "fine-fabric" Floy anchor tags (FD-683 with "fine fabric"
monofilarnent). Due to difficulties encountered in locating sufficient numbers of
small fish, suspected high mortalities of these fish, and incomplete recruitment of the
small whitefish to the fishing gear, spring tagging was not continued in 1990.

All commercial fishermen operating in the surrounding waters of Saginaw
Bay, northern Lake Huron, and southern Ontario were notified annually of the study
by mail. All major whitefish fishermen were visited several times to keep them
informed of the study and to request that tag recaptures be recorded and reported.
The Bayport Fish Company is the primary wholesale fish-buyer and was the primary
collector of fish tags from the area.

Tags which were returned from within the study area with information on the
date and location of recapture were used to document the movement patterns of fish

in the study area.

Abundance and Biomass
Population abundance (N) and biomass estimates were made using the
Petersen mark-recapture method, where
N = M * C / R
and, M = the number of legal-sized fish tagged in year 1

C = the number of fish caught by the fishery in year 2

15

Table 2. Location and number of lake whitefish tagged from
trap nets in Saginaw Bay, Lake Huron, during 1989 and 1990.

 

 

 

 

Location Date Trap net Number
size Tagged
Permit Zone Large
11-07-89 204
11-13-89 172
04-16-90 41
05-04-90 32
11-02-90 74
Total 523
Sand Point Small
11-09-89 374
11-12-89 263
11-13—89 68
04-16—90 25
11-03—90 216
11-10-90 419
Total 1365
Heisterman Island Small
11—04-89 168
11-13-89 518
11-14-89 733
11-03—90 262
11-09—90 . 804
11-14-90 203
Total 2688
Au Gres Small
04-12-90 209
11—08-90 373
Total 582

 

Grand Total 5158

 

16

R = the number of tags recaptured in year 2

Mean individual weights were estimated using a weighted mean weight of
legal-sized fish from the small and large-mesh trap net catches (432 and 483 mm
minimum legal lengths respectively) sampled throughout the fishing season. This
mean was used to convert the catch (C) from weight to numbers. M was corrected
for tag loss during the study period to meet one of the assumptions of the Petersen
method. Annual rates of tag 1033 were estimated from a Mayfield instantaneous tag
loss rate calculated from the number of tags lost to days exposed for the double-
tagged sub-sample (Bart and Robson 1982; White 1983). Annual catch was
corrected for recruitment during the season by subtracting an estimate of the
fractions of the catch which grew to legal size for the large-mesh and small-mesh
trap net fisheries. Confidence intervals were estimated using the Poisson estimator.
Total instantaneous mortality rates were estimated from the slopes of the descending
limbs of catch curves constructed by plotting the natural logarithms of frequency
against age, and from cohort analysis (Ricker 1975).
Annual survival (S) estimates were calculated from the following equation:

S = (R12 * M2) / (R22 * M,)

where: R12 = Recaptures in 1991 from tagging in fall 1989

R22 = Recaptures in 1991 from tagging in fall 1990

MI = Number of fish tagged in fall 1989

M2 = Number of fish tagged in fall 1990

17

and recaptures were corrected for tag 1033.

Annual mortality (A) was calculated from survival as:

A = l - S
Exploitation rates (u) were calculated as:
u = # of recaptures/ # of tagged fish, corrected for tag loss.
Instantaneous estimates of total mortality (Z), fishing mortality (F), and natural
mortality (M) (Ricker 1975) were be calculated as:

Z = -In (S)

F = (u)*(Z) /A

M=Z-F

Optimal Yield y
Optimal yield for the 1990 fishing season was estimated by multiplying
abundance and average biomass estimates of each age class by the optimal rate of

instantaneous fishing mortality for exploited whitefish populations (Clark and Smith

1984)

RESULTS
Length and Weight
Mean weights at age of lake whitefish in 1990 and 1991 from combined

samples of large and small trap net catches were similar. However, the 1989

18

samples were heavier at ages three through nine years (Figure 5). The greater
average weights observed in 1989 are probably attributable to the lack of spring
samples during that year. Regression of mean weight at age on In age yielded an
equation which can be used to predict weight at age. Figure 5 includes only those
ages for which samples were collected in each of the three years. During 1991, one
one-year old fish and seven two year-old fish were sampled from the spring trap net
fishery and two twelve year-old fish were also sampled (Table 3). The mean
weights at age of these age groups were not included in the regression due to the
lack of representation in each year, the variability of weight at age in juvenile fish,
and the difficulties of aging whitefish accurately at ages greater than ten years.
Mean lengths at age of lake whitefish in 1989, 1990, and 1991 from
combined samples from large and small trap net catches were more similar than
were weights. However, the trend observed in 1989 weight data was also Observed
in mean lengths at age, with fish sampled in 1989 being longer than mean lengths at
age observed in other years. Again, this is probably attributable to a lack of spring
sample data in 1989 (Table 4; Figure 6). Twelve year old fish were observed in
each year, however the small sample size and great variability in size at older ages
indicates these data are of little value. The one twelve year-old fish sampled in
1989 was the largest whitefish observed (765m) in the three years of commercial
catch assessment and compares to a Von Bertalannfy length at infinity parameter of
722mmcalculated from a body-to-scale-radius regression of ages one through

eleven.

Mean Weight (kg)

 

 

O

 

 

 

 

L
8

 

,—

L

11

 

Age

Figure 5. Mean weights at age of lake whitefish sampled from trap nets
throughout Saglnaw Bay during 1989, 1990, and 1991. Line represents the
regression of mean weight at age on In age (weight = 1.95 - 1.93(ln age)).

Table 3. Mean weights at age of all lake whitefish sampled from large and small
trap nets in Saginaw Bay, Lake Huron during 1989, 1990 and 1991.

 

Mean Weight (kg)

 

 

Year 1991 (n) 1990 (n) 1989 (n)
Age
1 0.062 ( 1)
2 0.171 ( 7) 0.275 ( 2)
3 0.399 (79) 0,333 ( 7) 0.653 ( 22)
4 0.642 (132) 0.390 (157) 0.892 ( 97)
5 0.924 (307) 0.928 (148) 1.275 (129)
6 1 .209 ( 72) 1.352 ( go) 1.87:! (241)
7 1.578 ( 70) 1,339 (101) 1.857 (162)
8 1.950 (44) 2,013 ' (53) 2.226 (77)
9 2.260 ( 88) 2,333 ( 23) 2.718 ( 25)
10 2.549 (21) 2,327 I 12) 2.803 ( 19)
11 2.785 ( 9) 2,324 ( 1) 2.957 ( 11)
12 2.897 ( 2) 4.950 ( 1)

 

20

 

 

 

 

 

 

 

 

 

800
o
+
700 —
600 '-
E
E
5 500 "
m
c
3
c 400 —
15
o
5
30° " o 1989
200 '_ I
100 J l l l l 1 L l 1 4 l
1 2 3 4 5 6 7 8 9 10 11 12

Age

Figure 6. Mean lengths at age of lake whitefish sampled from trap nets
throughout Saglnaw Bay during 1989, 1990 and 1991. Line represents the
regression of mean lengths at age on In age (length = 119.83 + 225.82(in age)).

Table 4. Mean lengths at age of all lake whiteflsh sam led from large and small
trap nets in Saglnaw Bay, Lake Huron during 1989, 19 0 and 1991.

 

Mean Length (mm)

 

 

Year 1991 (n) 1990 (n) 1989 (11)
Age
1 150.00 ( 1)
2 255.45 ( 7) 277.00 ( 4) 250.00 ( 2)
3 555.25 ( 75) 544.25 ( 25) 557.51 ( 22)
4 414.55 (152) 555.00 (275) 455.55 ( 55)
5 452.51 (507) 457.51 (255) 455.24 (125)
5 501.15 ( 72) 525.57 (1 45) 555.1 5 (242)
7 547.05 ( 70) 555.52 (151) 555.50 (152)
5 I 575.55 (44) 552.15 ' (104) 554.22 (77)
5 505.55 ( 55) 515.54 ( 55) 555.20 ( 25)
10 525.45 (21 ) 555.15 ( 17) 555.55 ( 15)
11 554.55 ( 5) 575.50 ( 5) 552.15 (11)

.4
M

038.50 ( 2) 734.00 ( 1) 705.00 ( 1)

 

21

To examine mean lengths at age of lake whitefish free from the possible
biases associated with year-to-year variation, differences in gears, and differences in
areas, I looked at mean lengths at age of fish sampled during spring, summer and
fall of 1991 from large-mesh deepwater trap nets set in the whitefish permit area
(Table 5; Figure 7). Although the mean lengths at age of fish at ages three and
four years appear to be longer in summer than in spring, these differences are not
significant (2-sample t-tests: age 3 =O.1581, d.f.=30, P>0.05; age 4 = 0.1720,
d.f.=93, P>0.05). Lengths at age are nearly identical at ages six through eight, and
small sample sizes and greater variability of lengths at older ages obscure any

apparent differences in length by season at ages greater than eight.

Sex and Maturation

The sex ratios of whitefish sampled from the commercial catch varied
strongly by season. Although the sex ratio of each year’s combined samples were
dominated by male fish (Chi2=55.13, d.f.=2, P<0.001) (Figure 8), this was likely due
to the high proportion of pre-spawning males sampled during the fall. Combined
spring and summer samples from all years did not differ from a 50:50 sex ratio
(Chi2=0.7853 and 1.090 respectively, d.f.=1, P>0.05), although combined fall
samples were composed predominantly of male fish (Chi2=95.601, d.f.=1,
P<0.001)(Appendix A).

Lake whitefish matured between the ages of three through seven years, with

approximately 50% becoming sexually mature by age five (Figures 9 and 10).

22

 

 

 

 

 

 

 

 

 

 

 

700
g 550— .
g 500~
8,, 550~
: 500—
5 450' Spring
2’ 400— 0 Summer
3 350— ° Fa"
g 300-
2 250— +
2002 45 7551011112
Age

Figure 7. Mean lengths at age of lake whlteflsh sampled from large-mesh trap
nets In the whitefish permit area of Saglnaw Bay during spring, summer and fall
of 1991. Une represents the regression of mean lengths at age on In age
(length = 76.22 + 234.57(ln age)).

Table 5. Mean lengths at age of lake whitefish sampled during spring, summer
and fall of 1991 from deepwater trap nets set in the whitefish permit area in
outer Saglnaw Bay, Lake Huron.

Mean Length (mm)

 

 

 

Season Springn) Summer(n) Fall (0)
Age
1
2 247.00 ( 2)
3 544.40 (15) 555.00 (17)
4 405.27 (55) 420.52 (55)
5 451.75 (71) 453.93 (155) 455.00 ( 1)
6 502.00 (17) ' 505.75 (25) 502.25 ( 7)
7 552.45 (21) 545.55 (15) 547.27 (11)
8 578.53 (15) 531,40 ( 5) 569.09 (11)
9 515.14 (14) 510.50 '( 5) 555.57 (12)
10 544.40 (10) 524.00 ( 2) 555.55 ( 5)
11 554.75 ( 4) 555.00 ( 5)
12 555.50 ( 2)
Mean (Total) 455.55 (202) 457.55 (515) 555.52 (45)

 

23
n=4 45 6014538 46 29 2712 8

1.0—
.9—
.8-
.7—
.6—
.4—
I
.2—
.1_1991
0

n=1 74101 69 82 42 22 10 1

_5
O
l

 

 

2:1990

 

 

 

- Percent Female

n=2 22 98129242161 77 25 18 11

—l

0;.ixainbinba'xlbo'co'o
l

 

AGE

1

 

o
—1
—2
~3
—.4
—.5
—5
~7
~5
—9
1.0 D
0 l"Cl
—.1 g
y: 0
' (D
—.4
_.5 B
.5
_.7 Z
-.8 91—31
—.9 (D
~1.o
o
-.1
—.2
—.3
—.4
—.5
—.5
—.7
-.8
—.9
—1.0

 

Figure 8. Sex composition of lake whitefish sampled from trap nets throughout

Saginaw Bay, Lake Huron during 1989 (n=415), 1990 (n=402) and 1991 (n=786).

Horizontal lines indicate annual overall sex composition.

Percent Mature

 

24

 

 

 

 

 

 

100‘ // - - = ~
80-
60' +1991
/
+1990
40— +1989
20- n=1661
0-1 1 1 1 I l l I I I I I
1 2 3 4 5 6 7 8 9 1011 12

AGE

Figure 9. Percent of sexually mature lake whitefish at age from samples
collected from the large and small-mesh trap net fisheries of Saginaw Bay,
Lake Huron during 1989, 1990 and 1991.

Percent Mature

25

 

    

 

 

 

 

 

100-
.80-
—-—spring
60‘ +summer
+fall
4o—
n=295
20-
Oi£-_llllll'll
12 3 4 5 6 7 8 9101112

AGE

Figure 10. Percent of sexually mature lake whitefish at age from samples
collected from the large-mesh trap net fishery in the whitefish permit area of
outer Saginaw Bay, Lake Huron during 1991.

26

Small percentages of three year-old fish were sexually mature in 1991. In 1989 and
1990 the youngest mature fish were four years of age. By age six, approximately
eighty percent of the year class had become mature, and nearly all (>90%) whitefish
were mature at age seven.

Whitefish samples from the large-mesh trap net fishery in the permit area
during spring, summer and fall of 1991 were assessed for sexual maturity. In
spring, 26% of the four year-old whitefish sampled were sexually mature, in summer
ten percent were mature, and in fall only one immature four year-old was

encountered (Figure 10; Appendix B).

Age and Growth

Ninety-two percent of the age determinations of the primary and assistant
scale-reader were in agreement. Of the 101 scale samples read independently. by
another experienced scale reader, 70.3% of the age determinations agreed with ours,
90% of the differences were of one year, and no determinations were different by
more than two years.

Figure 11 illustrates the annual age composition of lake whitefish compiled
from all trap net assessment data. Net run assessment of the 1989 catch revealed the
broad age structure of the Saginaw Bay lake whitefish population. Six year-old fish
dominated the catch, although eleven year-classes, from ages two through twelve,
were represented. The age structure shifted in 1990 as'four and five year-old fish

dominated the catch. The 1990 age structure was also broad and composed of

PERCENT

27

 

30_ 1990

    

 

   

123456789101112
AGE

Figure 11. Percent at age composition of lake whitefish sampled from
large and small-mesh trap net fisheries throughout Saginaw Bay during
1989, 1990 and 1991.

28

individuals from ages two through twelve years. In 1991, five year old fish
dominated the catch, apparently due to continued recruitment of the strong 1986 year
class. In 1991 the age structure was even broader than in the previous two years
due to one year-old fish appearing in the catch.

To remove the possible effects of different seasonal and gear-induced effects
on annual age composition, net run lake whitefish captured in large trap nets set in
the permit area during the summers of 1989 through 1991 were examined (Figure
12). The resulting age compositions are similar to those of Figure 11, except fewer
age classes, are represented. In the summer of 1989, the permit area catch was
dominated by five year-old fish, and fish from ages two through twelve were present
in the catch. In 1990, four year-old fish are predominant, and only six age classes
were present. In 1991, five year-old fish composed over 50% of the catch, and ages
three through ten were present.

Annual differences in age distributions are also apparent in samples collected
from small-mesh trap nets set near the Bayport Islands during fall (Figure 13). The
1983 year class dominated the small-mesh catch in 1989 as six year-olds. Six and
seven year-old fish were the predominant ages in samples collected during 1990, and
1991 samples were of a very broad age distribution dominated by five year-old fish.

To examine the data for seasonal differences in age composition, I compared
the spring, summer and fall age compositions of lake whitefish captured in large trap
nets set in the permit area during 1991 (Figure 14). The spring and summer age

compositions are similar, with both dominated by five year-old fish. The increase in

PERCENT

29

50 2
4o «-
30- 1955
20 5
1o 4-

 

 

50 5
40 ~-
30 -, 1990
20 '-
10 "

n=237

 

 

 

50 '-
40 ‘- .
30, 1551
20 5

n = 318
10..

 

 

 

 

123455785101'11'2
AGE

Figure 12. Age composition of lake whitefish sampled from large-mesh
trap nets in the whitefish permit area in outer Saginaw Bay during summer
in 1989, 1990 and 1991.

PERCENT

30

50»
4o~
30~
1989

20 -'

10”

 

 

50—
4o—
30—
1990

20"

10-

 

 

 

50-
4o-
30-
1991

20"

1o-

 

 

1 2 5 (i 5 5 17 5 5 1o 11
.AGE

Figure 13. Age composition of lake whitefish sampled from small-mesh
trap nets at Bayport Islands in inner Saginaw Bay during 1989, 1990
and 1991.

 

~—

PERCENT

50-
40-

30“

SPRING

20-

10— n =204

 

 

50‘

4o-
SUMMER

30-
20-

1o— n=318

 

 

 

50 -
4° ' FALL
30 -
20 -

10-

 

 

 

Figure 14. Age composition of lake whitefish sampled from large-mesh trap nets
in the whitefish permit area in outer Saginaw Bay during spring. summer and fall
of 1991.

32

the proportion of five year-old fish from spring to summer is most likely attributable
to the continuing recruitment of five year-olds into the fishery. During spring, small
percentages of eleven and twelve year-old fish were present. in the catch. No fish
older than ten were present in the catches assessed during the summer. In fall, few
five year-olds were present and the predominate age class was nine years old. This
seasonal change in age composition between summer and fall was also present in
1989, when the predominate age in the catch changed from age five in summer to
age seven inifall (Figure 15). Both the 1989 and 1991 summer and fall age
distributions were significantly different from one another Kolmogorov—Smirnoff

two-sample test, P<0.01).

Abundance and Biomass

Abundance and biomass estimates were based upon tag return data, which
were adjusted for both recruitment of younger fish into the fishery and for tag loss.
To estimate the rate of tag loss, a total of 358 fish were double-tagged. Ten double-
tagged fish were recovered, seven with both tags still attached and three with only
one tag for a tag-loss rate of 30% over the course of the study. A daily Mayfield
estimate of tag retention for the double-tagged sub-sample was extrapolated to yield
an annual probability of retaining one tag over one year of 0.6906 (Bart and Robson
1982; White 1983). Based upon the binomial distribution of double-tagged returns,
a 95% confidence interval of the tag loss rate ranges from 7 to 65% (Steele and

Torrie 1980). Due to the wide confidence interval on the return of double-tagged

PERCENT

33

3O SUMMER

20—

10-

 

 

20 -
FALL

10-

 

 

 

125455789101'112

Figure 15. Age composition of lake whitefish sampled from large-mesh trap nets
in the whitefish permit area in outer Saginaw Bay during summer and fall 1989.

34

fish, the 30.94% annual tag loss rate was used to adjust the total number of tagged
fish (M) used to estimate abundance.

Because measures of abundance and biomass were based upon tag returns, it
was essential to estimate the amount of cooperation by the fishermen involved in tag
recapture and return. The major large-mesh trap net operators were fully
cooperative, as it was due to their initiative and funding that the study was
conducted. The other large-mesh trap net fisherman fished only seasonally in a
northern area of the bay, and did not report any tag recoveries during several visits,
phone and mail contacts. Therefore, it is assumed that all tags recovered by large-
mesh trap net fishermen were reported. It was known that several small-mesh trap
net fishermen were not returning the tags they recovered, but their tags were being
returned by several wholesale fisheries. To determine whether most of the recovered
tags were being received, the percentage of tags-to-catch of a small-mesh trap net
fisherman who was known to be cooperative was compared with the percentage of
other small-mesh trap net tags-to-catch (including tags returned by wholesale
fisheries). This analysis demonstrated that the, tags to catch ratios were independent
of the method of tag return (Chi2=1.035, d.f.=1, P>.05), thus it could be assumed
that all recaptured tags were returned.

Abundance and biomass estimates were calculated for 1989 and 1990 (Table
6). A population estimated at 3,750,000 (95% Confidence Interval 2,946,076 -
4,759,047) whitefish existed in Saginaw Bay during 1989, decreasing to 2,690,000

(2,088,734 - 3,450,952) in 1990. Biomass, based on weighted mean individual

35

Table 6. 1989 and 1990 biomass and abundance estimates for
Saginaw Bay (Lake Huron Management Zone MH4) calculated from
the Petersen mark-recapture estimator.

 

 

 

Estimated Mean ,Estimated
Year Ma Cb Rc Population Weight/ Total
Size (N) fish Biomass
(kg)d (kg)
1989 2,111 117,229 66 3,749,552 1.79 6,711,698
1990 1,328 119,536 59 2,690,573 1.63 4,385,634
1989, 95% C.I. 84 2,946,076 5,273,477
52 4,759,047 8,518,693
1990, 95% C.I. 76 2,088,734 3,404,637
46 3,450,952 5,625,052

 

aNumber of fish tagged, adjusted for recruitment

bNumber of fish harvested annually

cNumber of tagged fish which.were recaptured, adjusted for tag loss

dWeighted mean weights of legal-sized individual fish in the large
and small-mesh trap net fisheries

36

weights from samples of the large and small-mesh trap net fisheries, was estimated

at 6,711,698 kg in 1989 and 4,385,634 in 1990.

Movement Patterns

Of 307 juvenile or sub-legal (< 483 mm) whitefish tagged during the spring
of 1990, ten tags were returned with known recapture locations (Figure 16). All of
these recaptures were made within the original tagging area, indicating little
movement of juvenile whitefish during the study, period. These recaptures were
made throughout the year and do not indicate any seasonal trends (Appendix C).

The most distant recovery location of any of the tagged fish was from near
South Bay, Manitoulin Island, Ontario, approximately .150 linear land miles from its
tagging site (Figure 17). Nine additional tags were returned by Canadian
commercial fishermen from gill netting operations in south eastern Lake Huron.
These fisheries operate year-around and tags were recovered without any apparent
seasonal pattern. Of interest is one fish which was tagged at the Bayport Islands
during November of 1989 while in spawning condition and recaptured the following
November in the Ontario waters of southern Lake Huron, near Kettle Point.

Due to the relatively exposed location of the large-mesh trap nets in the
whitefish permit area, weather conditions limited our ability to tag fish from these
nets. In November of 1989, 376 whitefish were tagged from these nets (Table 7).
Three of these fish were returned during 1990 with known recapture locations, one

from across the bay near Au Gres, one from the Bayport Islands to the south, and

37

 

 

Location and number tagged:

I Au Gres, n = 209
0 Permit zone, n = 73

 

 

A Sand Point, n = 25 Permit area
Point Lookout .
.... . 4661}
Point Au Gres I D A"
‘ Barges
I I I Caseviiie
Sand Point

6’ Ba art
0,, VP

 

O
.{1
45’ ~
Sebewaing - O 5

I————i

miles
Bay
City

 

Figure 16. Tags returned in 1990 and 1991 with known recapture locations from
tagging conducted during spring 1990 near Au Gres, Sand Point, and the whitefish
permit area of sub-legal sized lake whitefish.

38

 

 

I
e
I
I
I
I
I
n
s
s
.5
e e
g e e
e- .
....

 

“.North Channel
4506 South Bay
Georgian Bay
, , Lake ‘Huron
Michigan =.
at
6’9
a .
9’6 '-. .
Bayport ' Ontario
Bay City e
. ..
C . .
6 etfie Point
Pt. Huron -' I
Sarnia

 

Figure 17. Tags returned In 1990 and 1991 with known recapture locations by
Canadian commercial fishermen. '

 

39

Table 7. Numbers of lake whitefish tagged, double-
tagged, and returned from all fall tagging locations
during 1989 through 1991.

 

 

 

 

Number 1990 1991 Total
tagged
Location Date N N N
Fall 1989
North Island 11-04 168 7 13 20
Heisterman Island 11-13 518 16 17 33
11-14 733 ' 15 12 27
Sand Point 11-09 374 S 3 9
11-12 263 4 5 10
11-13 68 l 1 2
Permit Zone 11-07 204 2 7 9
11-13 172 1 l 2
Total 2500 51 60 110
Fall 1990
Heisterman Island 11-03 262 . 6
11-09 804 15
11-14 203 4
Sand Point 11-03 216 6
11-10 419 4
Permit Zone 11-02 74 l
AuGres 11-08 373 , - 10
Total 2351 46

 

40

one from the permit area (Figure 18). In 1991 eight tags were returned, seven of
these from the permit area and one from the Canadian gill net fishery in southern
Lake Huron. In November of 1990, 74 fish were tagged in the permit area (Table
7). Only one of these tags was recaptured from a known location, near Au Gres.

From nets set off the north shore of Sand Point, 1,340 whitefish were tagged
and released during November of 1989 and 1990 (Table 7). Twenty-nine of these
fish were recaptured at locations throughout the bay, one in southern Lake Huron,
and one was returned from a commercial fish wholesale business in Racine,
Wisconsin (Figure 19). Only two fish were recaptured near the original tagging site,
most (17) were recaptured in the permit area, eight were recaptured in nets set near
the Bayport Islands, and one was recaptured near Point Au Gres. Fall recaptures do
not indicate homing to the tagging site (Appendix C).

The Bayport Islands are located close to the commercial fish docks at
Bayport and are protected from hazardous storms arising from the northeast. These
factors allowed us to tag a large number (2,678) of whitefish from nets set off the
northwestern shores of the islands during November in 1989 and 1990.
Consequently, the largest number (105) of tag recoveries are of fish tagged in these
nets (Figure 20). These tags were recovered from all areas of the bay (99), and
seven were recaptured in the Canadian waters of southern Lake Huron. There do
not appear to be seasonal or annual patterns of movement which are discernable
from these tag return data.

Fall tagging was conducted near Au Gres only during 1990 when 373

41

 

marked, n = 376
A returned in 1990, n = 3

e returned in 1991, n = 8

 

Permit area

 

Point Lookout ' * A
- Charity Is 9 9 . 9
Point Au Gres D ' . . 0
A
Sand Point
‘5 a
Q <5
if 0 5
Q9 |-—-i
miles
Bay
City 0 southern Lake Huron

 

 

Figure 18. Tags returned In 1990 and 1991 with known recapture locations from
tagging conducted durlng the fall of 1989 in the whitefish permit area.

 

42

 

marked In 1989, n I: 705
marked In 1990. n = 626
Q 1990 returns of 1989 tagging, n .. 10

A 1991 returns of 1989 tagging, n a 10

 

I 1991 returns 011990 tagging, n = 9

Permit area
IA.-
A A A
P ' tL k ut A
cm 00 o I: .. A
Point Au Gres D A .
O
O I
- Sand Pomt
I ' : Q
A a}
. 4% o 5
$2 l—.—-l
Q7 miles
I southern Lake Huron
F) 0 Racine, Wisconsin

 

 

Figure 19. Tags returned in 1990 and 1991 with known recapture locations from

tagging conducted during fall 1989 and fall 1990 at Sand Point.

43

 

Tagged in 1989, n a 1.419
Tagged In 1990, n I 1.259

. 1990 returns ct1989 tagging, n I 38

A 1991 returns M1989 tagging, n - 41

 

 

I 1991 returns ct1990tagglng,n .. 20 Permit area
‘ A I I. I
. A 1 A e :.A A A
Pount Lookout A A.. . A A I
. A e O... A I
Ponnt A Gres .:..: D A A _
A O O O ‘
I I A'eA *
Ag. . b ,9 Sand Point
A I A. O b
A A Q Q .
A IAAA:9 W
A. AA. Qo
I 45'5“
I
Ba A AA A
cu), l . . southern Lake Huron

 

Figure 20. Tags returned in 1990

and 1991 with known recapture locations from

tagging conducted during fall 1989 and fall 1990 at Bayport Islands.

 

44

whitefish were tagged and released. Ten of these fish were recaptured, eight from near

the original tagging site and two from the permit area (Figure 21).

Yield

Using population estimates, age distributions, and growth characteristics
determined in this study, allowable yield was estimated from a target optimal total
annual mortality rate of 60%. This mortality rate was reported to be the median
mortality limit which lake whitefish populations can endure over time without
collapsing (Clark 1985).

Yields for 1990 and 1991 were calculated using population estimates from the
fall of 1989 and 1990. For each year the average biomass of each age class was

calculated using the following equation (Ricker 1975):

1
73': f3, (We:
i=0

where B0 equals the fall biomass estimate; instantaneous growth rate (G) was
determined from summer age data of whitefish permit area, Bayport Islands and Sand
Point fish; instantaneous total mortality rate (Z) was estimated from cohort analysis to
be 0.85, exploitation (u) = 0.0363, instantaneous fishing mortality was set at (F) = 0.6,
and instantaneous natural mortality (M) = 0.313. All parameters except the
instantaneous growth rates were constant for all ages.

Yield estimates for 1990 and 1991 differred by 1/3, yet their 95% confidence

intervals overlapped indicating that’the difference was not significant. In

45

 

 

Tagged, n = 373
Returned, n = 10

 

Permit area

Point Au Gre e u :
. e
. 0
g e
. ts
' Q
[2% o 5
t——l
miles

R

 

Figure 21 . Tags returned in 1991 with known locations from tagging conducted
during fall 1990 near Au Gres.

 

46

1990, yield at instantaneous fishing mortality (F) = 0.6 was estimated to be
3,002,685 kg (95% Confidence Interval = 2,359,221 - 3,811,049) (Table 8),
decreasing to 1,962,022 kg (95% Confidence Interval = 1,523,149 - 2,516,506)
(Table 9). Actual harvests in these two years were 208,967 kg in 1990 and 193,332
kg in 1991. F was estimated from analysis of the 1983 year-class at 0.0371. Using
this value of F in the yield equation, yield in 1991 closely approximates actual

harvest at 185,659 kg.

DISCUSSION

This study provided new, baseline information about the lake whitefish
population of Saginaw Bay which will be useful for future management of the stock.
The broad age and size structure of the population indicates that the stock is not
experiencing heavy mortality due to fishing or natural causes. The observed
differences in size and age structure of whitefish sampled from different areas and at
different seasons are probably attributable to seasonal distributions due to behavior.
For example, juvenile lake whitefish are known to inhabit shoal waters (Reckahn
1970; Scott and Crossman 1975) and thus are found more frequently in the shoal
areas of inner Saginaw Bay. During fall, an abundance of larger, older fish
congregate to spawn on the shoals, and younger, immature fish do not mix with the
spawners. Thus the fall age compositions are very different from those during other
seasons.

In heavily exploited lake whitefish populations, such as Lake Michigan’s

47

Table 8. 1990 yield estimates for Saginaw Bay lake whitefish at F = 0.60.

 

 

 

Age in % of Biomass 95% Confidence Intervals a b c
1989 catch in 1989 (Lower limit) (Upper limit) G 2 F
at age (kg) (kg) (kg)
4 7.0 469819 369143 596309 0.330 0.85 0.6
5 16.5 1107430 870124 1405584 0.240 0.85 0.6
6 34.5 2315536 1819350 2938949 0.263 0.85 0.6
7 23.1 1550402 1218173 1967818 0.167 0.85 0.6
8 1 1 .0 738287 580082 937056 0.127 0.85 0.6
9 3.6 241621 189845 306673 0.108 0.85 0.6
10 2.7 181216 142384 230005 0.135 0.85 0.6
>10 1.6 107387 84376 136299 0.074 0.85 0.6
Total 671 1698 5273477 8518693

 

Age in Biomass 95% Confidence Intervals Harvest at 95% Confidence Intervals
1990 in 1990 (Lower limit) (Upper limit) F = .60 (Lower limit) (Upper limit)
g)___1_g)___t|$9)___059)____figl___i_9

(k k

4 366350 287846 464982 219810 172708
5 829028 651379 1052227 497417 390827
6 1751472 1376157 2223022 1050883 825694
7 1123418 882686 1425877 674051 529611
8 525588 412962 667093 315353 247777
9 170580 134027 216506 102348 80416
10 129464 101721 164319 77678 61033
>10 74694 58689 94805 44817 35213

R)

278989
631336
1333813
855526
400256
129903
98591
56883

 

Total 4970594 39054668 63088305 29823564 2343280.1

 

a

instantaneous growth rate

b

instantaneous total annual mortality rate
c

instantaneous fishing mortality rate

48

Table 9. 1991 yield estimates for Saginaw Bay lake whitefish at F = 0.60.

 

 

 

 

 

 

 

 

Age in % of Biomass 95% Confidence intervals a b c
1990 Catch in 1990 (Lower limit) (Upper limit) G 2 F
at age (kg) (kg) 1kg}
4 .16.4 719244 558360 924149 0330 0.85 0.6
5 28.4 1245520 966917 1600355 0.240 0.85 0.6
6 17.1 749943 582193 963594 0.263 0.85 0.6
7 19.0 833270 646881 1070660 0.167 0.85 0.6
8 12.3 539433 418770 693111 0.127 0.85 0.6
9 4.1 179811 139590 231037 0.108 0.85 0.6
10 2.0 87713 68093 112701 0.135 0.85 0.6
>1 0 0.7 30699 23832 39445 0.074 0.85 0.6
Total 4385634 3404637 . 5635052
Age in Biomass 95% Confidence interval Harvest at 95% Confidence intervals
1991 in 1991 (Lower limit (Upper limit) F = .60 (Lower lim (Upper limit)
(kg) 4kg) (kg) (kQL___ll_<9)___1£9)___
4 239384 185838 307582 143631 1 1 1503 184549
5 558128 433284 717133 334877 259970 430280
6 1161053 901344 1491824 696632 540806 895095
7 730899 567408 939124 438539 340445 563474
8 343436 266615 441277 206062 159969 264766
9 123847 96145 159130 74308 57687 95478
10 93995 72970 120773 56397 43782 72464
>10 61010 47363 78391 36606 28418 47034
Total 331 1 752 2570966 4255234 1987051 1542579 2553140
a

instantaneous growth rate

0

instantaneous total annual mortality rate

C

instantaneous fishing mortality rate

49

North Shore population no fish older than age five are present (Scheerer 1982). Age
at maturity is another indication of fishing pressure, as age at maturity decreases
with sustained heavy fishing pressure. Saginaw Bay lake whitefish did not begin to
mature until reaching the age of four years and were not 100% mature until reaching
seven years of age, similar to the lightly exploited Alpena whitefish population
(Freeberg et a1. 1990).

These basic observations on the relative amount of exploitation were
supported by estimates of mortality and exploitation calculated from catch curve and
cohort analysis. Catch curve analysis is the least reliable 0f the two estimates
however, due to variations in year class strength which obscure true trends in year-
to-year numbers at age. The third method of estimating mortality and exploitation,
from tag return data, is probably the most flawed. For the mark-recapture based
population parameters to be reliable, the following conditions must apply: the
marked fish (M) become randomly distributed in the population before the second
sample (C) is taken and (C) must be selected at random from the population
(Robson and Regier 1964). It is also assumed that the population is closed. By
tagging fish during the fall spawning closure and waiting over-winter to recapture
tags, the first condition is probably met. However, the second condition has clearly
not been met by virtue of the fact that the fishery occurs within Saginaw Bay, and
many tagged fish ventured beyond the bay into Lake Huron proper. Although the
Canadian fishery did return a substantial number of tags, the Canadian catch far

exceeds the Saginaw Bay harvest, and the ratios of tags-to-catch are grossly different

50

between the two areas. This indicates that either the Saginaw Bay whitefish
partially mix with the population(s) inhabiting the eastern shore of southern Lake
Huron, or one homogenous stock exists and tag reporting was (very) incomplete
from the Canadian fishery. Canadian fishermen were notified of the study by mail,
and tag returns were received from both the fishermen themselves and from
governmental on-board fishery observers, indicating that tag recovery reporting was
good.

Because M is functionally over-estimated, the resulting annual survival rate is
over-estimated. Hence, total annual mortality is over-estimated, and exploitation,
instantaneous total annual mortality, instantaneous total mortality, instantaneous total
fishing mortality, and instantaneous total natural mortality rates are all under-
estimated.

One hypothesis which has been put forth to explain the apparent mixing of
whitefish in southern Lake Huron with those inhabiting Saginaw Bay is a that a lack
of suitable spawning habitat exists in the southern Lake with the exception of the _
Bay which contains vast areas of suitable spawning substrate, causing fish to migrate
into the Bay to spawn. Perusal of the Atlas of the Spawning and Nursery Areas of
Great Lakes Fishes (Goodyear et al. 1982) indicates that this may be the case. The
atlas states that most of the shoreline, island and reef areas of Saginaw Bay were
used for whitefish spawning, and other than two small reef areas in the southern
basin at Harbor Beach and Port Huron, no other whitefish spawning areas were

known to exist in southern Lake Huron. The literature does not address whitefish

51

spawning grounds in the Ontario waters of southern Lake Huron, but communication
with Ontario fisheries managers and fishermen indicates that a possible spawning
location exists near Kettle Point and no other grounds are known (N. Robert Payne,
Ontario Ministry of Natural Resources, personal communication; John Little,
commercial fisherman, personal communication).

Other support for this hypothesis includes the favorable ice cover which
forms early (mid-November) annually on the Bay, followed by rapid spring break-up
and fast warming of the highly productive enriched waters of the Bay. Freeberg et
al. (1990) discovered that whitefish year-class strength is determined during the first
few weeks post-hatching and that early ice-cover followed by an early, warm spring
lead to greater survival and eventual recruitment of whitefish. Saginaw Bay
consistently provides these conditions.

The problems which plagued the mark-recapture based exploitation and
mortality estimates also effected estimates of stock abundance and biomass, which
were based upon tagging data. Because M was effectually over-estimated, estimates
of abundance and biomass were also over-estimated. This is obvious when
comparing the 1989 and 1990 biomass estimates with historical harvest, biomass is
estimated at approximately two to three times the all-time record harvest. Because
tagging occurred during the fall when the fishery was presumably composed of
mixed stocks, I was unable to estimate that portion of the marked fish which resided
primarily within the Bay in order to estimate the fishable population of Saginaw

Bay.

52

Yield estimates are based upon the above described flawed biomass estimates
and were likewise unreliable, however, using the estimated total annual fishing
mortality value the actual harvest was closely approximated.

Saginaw Bay lake whitefish are forced by seasonal thermal conditions to be
migratory. With the exception of spring and fall, during tum-over, lake whitefish
are usually found just off the lake bottom, under the therrnocline in water between 6
and 8°C. The relatively shallow waters of Saginaw warm rapidly during the summer
months, and by early August temperatures at 30m are near 10°C (Beeton et a1.
1967). Water temperatures remain above 10°C until mid-September and lake
whitefish apparently leave the Bay’s waters for the Open lake where more favorable
temperatures can be found.

When this study was being planned, it was expected that the Saginaw Bay
whitefish would prove to be an isolated, closed population composed of multiple
reproductively isolated stocks, similar to most other Great Lakes whitefish
populations studied (eg. Budd 1957; Cucin and Regier 1966; Ebner and Copes 1985;
Casselman et al. 1981; Scheerer and Taylor 1985; Smale 1988; Prout 1989; Walker
et al. in press; etc.). Perhaps the most significant finding of this study is that
Saginaw Bay lake whitefish are not discrete from the population inhabiting southern
Lake Huron waters. Fall tag returns did not indicate homing to specific spawning
grounds, or even to Saginaw Bay. Over five percent of the tags recovered were
returned from the Ontario waters of southern Lake Huron, presumably these fish also

range south along the Michigan shore where no fishery Operates to intercept and

53

report them. The recovery of one tag to the far north at the mouth of South Bay,
Manitoulin Island, Ontario indicates that this population is very migratory, and
perhaps mixes with other Lake Huron whitefish populations. These findings support
those of Hill (1982) who found no evidence for discrete stocks of whitefish in outer
Saginaw Bay from four locations, based on the results of electrophoretic studies.
The implications of this finding leads to a new view of the Saginaw Bay whitefish
population as being part of a larger southern Lake Huron stock, based on the
movements of tagged fish.

The findings of this study are important for the continued management of the
Saginaw Bay lake whitefish fishery. Rather than assuming that the stock is discrete
and exists within the geographical boundaries of Lake Huron’s Whitefish
Management Zone 4, tag returns have indicated the far-ranging migratory nature of
these fish. Saginaw Bay’s importance as a spawning and nursery ground for lake
whitefish will place more importance on continued clean-up of it’s industrial
pollutants and the identification and preservation of critical spawning areas. One
research need emphasized. by this study is to identify lake whitefish spawning and
nursery grounds within the southern portion of Lake Huron, in both U. S. and
Canadian waters.

Realization that the fall fishery is targeting an international, mixed-stock
concentration of spawners may lead to increased United States - Canadian
management of this important fishery. Another research need identified by this

study is to determine the number of lake whitefish stocks and the degree of stock

54

mixing which occurs in the southem~ Lake Huron basin.

Even though estimates of exploitation from this study are not reliable, the
small catch-to-tag return ratios and the size and age structure observed indicate that
the population is experiencing low levels of exploitation. Thus, it is probable that
fishing effort could increase without harmful effect to the population. Finally, it is
apparent that both the large and small-mesh trap net fisheries are harvesting fish
from the same population, thus the current different minimum size limits for each
fishery lack a logical purpose and pose both enforcement and management

complications.

LITERATURE CITED

55

Baldwin, Norman S., Robert W. Saalfield, Margaret A. Ross, and Howard J.
Buettner. 1979. Commercial fish production in the Great Lakes, 1867-1977.
Technical report number 3, Great Lakes Fishery Commission, Ann Arbor,
Michigan. _

Bart, J. and D.S. Robson. 1982. Estimating survivorship when subjects are visited
periodically. Ecology, 63: 1078 - 1090.

Beeton, A.M., S.H. Smith, and RF. Hooper. 1967. Physical limnology of Saginaw
Bay, Lake Huron. Technical Report No 12. Great Lakes Fisheries
Commission, Ann Arbor, Michigan.

Budd, J. 1957. Movements of Tagged whitefish in northern Lake Huron and
Georgian Bay. Transactions of the American Fisheries Society 86: 128 — 134.

Carlander, K. D. 1981. Caution on the use of the regression method of back-'
calculating lengths from scale measurements. Fisheries 6 (1): 2-4.

Casselman, J.M., J.J. Collins, E.J. Crossman, P.E. Ihssen, and GR. Spangler. 1981.
Lake whitefish (Coregonu_s_ cluneaformis) stocks of the Ontario waters of

Lake Huron. Canadian Journal of Fisheries and Aquatic Sciences. 38: 1772-
1789.

Christie, W.J. 1974. Changes in the fish species composition of the Great Lakes.
Journal of the Fisheries Research Board of Canada. 31: 827 - 854.

Clark, RD. 1985. A tale of two whitefish fisheries: the boom and buster and the
green-branch. Michigan Department of Natural Resources Technical Report
No. 84-4. Lansing, Michigan.

Clark, R.D. Jr., and K.D. Smith. 1984. Quota calculations with SAP.1 (Stock
Assessment Package). Michigan Department of Natural Resources Institute of
Fisheries Research, Ann Arbor, Michigan.

Cucin, D. and H.A. Regier. 1966. Dynamics and exploitation of lake whitefish in
southern Georgian Bay. Journal of the Fisheries Research Board of Canada.
23: 321 - 274.

Ebner, MA. and RA. Copes. 1985. Population statistics, yield estimates, and
management for two lake whitefish stocks in Lake Michigan. North American
Journal of Fisheries Management. 5: 435 - 448.

APPENDICES

56

Freeberg, M.H., W.W. Taylor, and R.W. Brown. 1990. Effect of egg and larval
survival on the year-class strength of lake whitefish in Grand Traverse Bay,
Lake Michigan. Transactions of the American Fisheries Society 119: 92 -
100.

Goodyear, C.D., T.A. Edsall, D.M. Ormsby Dempsey, G.D. Moss, and RE.
Polanski. 1982. Atlas of the spawning and nursery areas of Great Lakes
Fishes. Volume V. Lake Huron. US. Fish and Wildlife Service, FWS/OBS -
82/52.

Hile, R. and H.J. Buettner. 1959. Fluctuations in the commercial fisheries of
Saginaw Bay, 1885 - 1956. U. S. Fish and Wildlife Service, Research Report
No. 51.

Hile, R., G.F. Lunger and H.J. Buettner. 1,953. Fluctuations in the fisheries of the
State of Michigan waters of Green Bay. Fisheries Bulletin 75 of the US. Fish
and Wildlife Service, Volume 54. 34 pp.

Hill, T.L. Identification of lake whitefish stocks in western Lake Huron. MS Thesis.
University of Michigan, Ann Arbor, Michigan.

Keller, Myrl, J.C. Schnieder, L.E. Mrozinski, R.C. Haas, and J.C. Weber. 1987.
History, status and management of fishes in Saginaw Bay, Lake Huron, 189 -
1986. Michigan Department of Natural Resources, Fisheries Division,
Fisheries Technical Report No. 87 - 2.

Lanman, J. 1839. History of Michigan: Civil and topographical in compendious form
with a view of the surrounding lakes. E. French, New York.

Prout, M.W. 1989. Population dynamics and stock differientiation of lake whitefish,
Coregonus clupeaformis, in Grand Traverse Bay, Lake Michigan. MS Thesis,
Michigan State University, East Lansing, Michigan.

Reckahn, J.A. 1970. Ecology of young lake whitefish (Coregonus clu eaforrnis in
South Bay, Manitoulin Island, Lake Huron. Pages 437 — 460 In: C.C. Lindsey
and CS. Woods, editors. Biology of coregonid fishes. University of Manitoba
Press, Winnepeg.

Ricker, W.E. 1975. Computations and interpretation of biological statistics of fish
populations. Bulletin 191. Fisheries Research Board of Canada. Ottawa,
Canada.

Robson, D.S. and H.A. Regier. 1964. Sample size in Petersen mark-recapture
experiments. Transactions of the American Fisheries Society. 93: 215 - 226.

57

Scott, W.B. and E.J. Crossman. 1975. Freshwater fishes of Canada. Fisheries
Research Board of Canada. Bulletin 184.

Scheerer, PD. 1982. Population dynamics and stock differientiation of lake whitefish
in northeastern Lake Michigan with implications for their management. MS
Thesis, Michigan State University, East Lansing, Michigan.

Scheerer, PD. and W.W. Taylor. 1985. Population dynamics and stock
differentiation of lake whitefish in northeastern Lake Michigan with

implications for their management. North American J. of Fish. Res. 5: 526 -
536.

Smale, MA. 1988. A comparative analysis of lake whitefish population dynamics in
northeastern Lake Michigan. MS Thesis, Michigan State University, East
Lansing, Michigan.

Smale, M.A., and W.W. Taylor. 1986. An analysis of sources of error in back-
calculation methods applied to lake whitefish Coregonus clupeaformis. In:
Proceedings of the International Symposium on Age and Growth in Fishes,
Iowa State University Press, Iowa.

Steele, G.D. and J.H.Torrie. 1980. Principals and procedures of statistics. McGraw -
Hill, New York.

Van Oosten, J. 1923. A study of the scales of whitefish of known ages.
Zoologica. 2: 380 - 412.

Van Oosten, J., R. Hile, and F.W. Jobes. 1946. The whitefish fishery of Lakes
Huron and Michigan with special reference to the deep-trap-net fishery.
Fisheries Bulletin Vol. 50, No. 40: 297 - 394.

Walker, S.H., M.W. Prout, W.W. Taylor, and SR. Winterstein. 1992. Population
dynamics and management of lake whitefish stocks in Grand Traverse Bay,
Lake Michigan. North American Journal of Fisheries Management. (In press.)

White, GO 1983. Numerical estimation of survival rates from band recovery and
biotelemetry data. Journal of Wildlife Management: 47: 716 - 728.

58

Appendix A. Sex composition by season, location, gear, and age of
lake whitefish assessed from commercial trap net catches of Saginaw
Bay, Lake Huron during 1989 through 1991.

 

 

Season Location Gear Age % F % M N
1991 Saginaw Bay All 2 1.00 0.00 4
3 0.53 0.47 45

4 0.40 0.60 60

5 0.39 0.61 145

6 0.53 0.47 38

7 0.26 0.74 46

8 0.41 0.59 29

9 0.67 0.33 27

10 0.58 0.42 12

11 0.63 0.38 8

12 1.00 0.00 I

MEAN (TOTAL) 0.44 0.56 (415)

Spring Permit Zone TN—L 2 1.00 0.00 l
3 0.88 0.13 8

4 0.36 0.64 11

5 0.58 0.42 26

6 0.60 0.40 5

7 0.13 0.87 15

8 0.44 0.56 9

9 0.70 0.30 10

10 0.57 0.43 7

11 0.25 0.75 4

12 0.00 1.00 I

MEAN (TOTAL) 0.49 0.51 (97)

Spring Bay City TN-S 2 0.00 1.00 3
3 0.40 0.60 20

4 0.17 0.83 12

5 0.29 0.71 7

6 0.20 0.80 5

7 0.00 1.00 3

MEAN (TOTAL) 0.26 0.74 (50)

59

 

 

Appendix A. Cont.
Season Location Gear Age % F % M N
Summer Permit Zone TN-L 3 0.44 0.56 9
4 0.52 0.48 29
5 0.44 0.56 84
6 0.63 0.38 16
7 0.63 0.38 8
8 0.00 1.00 l
9 1.00 0.00 2
10 1.00 0.00 I
MEAN (TOTAL) 0.49 0.51 ~(150)
Fall Permit Zone TN-L 5 0.00 1.00 1
6 0.71 0.29 7
7 0.27 0.73 11
8 0.55 0.45 11
9 0.67 0.33 12
10 0.33 0.67 3
11 1.00 0.00 3
MEAN (TOTAL) 0.54 0.46 (48)
Fall Bayport TN-S 3 0.63 0.38 8
Islands 4 0.38 0.63 8
- 5 0.12 0.88 26
6 0.17 0.83 6
7 0.22 0.78 9
8 0.25 0.75 8
9 0.33 0.67 3
10 1.00 0.00 1
11 1.00 0.00 1
MEAN (TOTAL) 0.27 0.73 (70)
1990 Saginaw Bay All 3 1.00 0.00 1
4 0.42 0.58 74
S 0.40 0.60 101
6 0.33 0.67 69
7 0.46 0.54 82
8 0.40 0.60 42
9 0.50 0.50 22
10 0.50 0.50 10
11 0.00 1.00 1
MEAN (TOTAL) 0.41 0.59 (402)

60

Appendix A. Cont.

 

 

Season Location Gear Age % F ° M N
Spring Permit Zone TN-L 4 0.46 0.54 35
5 0.48 0.52 42

6 0.40 0.60 20

7 0.52 0.48 33

8 0.67 0.33 21

9 0.59 0.41 17

10 0.50 0.50 10

11 0.00 1.00 1

MEAN (TOTAL) 0.50 0.50 (179)

Summer Permit Zone TN-L 4 0.37 0.63 35
5 0.47 0.53 32

6 1.00 0.00 2

7 0.20 0.80 5

8 1.00 0.00 1

MEAN (TOTAL) 0.43 0.57 (75)

Fall Bayport TN—S 3 1.00 0.00 1
Islands 4 0.50 0.50 4

5 0.19 0.81 27

6 0.28 0.72 47

7 0.45 0.55 44

8 0.10 0.90 20

9 0.20 0.80 5

MEAN (TOTAL) 0.30 0.70 (148)

1989 Saginaw Bay All 2 1.00 0.00 2
3 0.55 0.45 22

4 0.46 0.54 98

5 0.42 0.58 129

6 0.35 0.65 242

7 0.34 0.66 161

8 0.40 0.60 77

9 0.36 0.64 25

10 0.44 0.56 18

11 0.55 0.45 11

12 1.00 0.00 1

MEAN (TOTAL) 0.39 0.61 (786)

61

 

Appendix A. Cont.
Season Location Gear Age % F % M N
Summer Permit Zone TN—L 2 1.00 0.00 2
3 0.55 0.45 22
4 0.48 0.52 92
5 0.50 0.50 98
6 0.50 0.50 88
7 0.40 0.60 52
8 0.42 0.58 24
9 0.67 0.33 6
10 0.50 0.50 6
11 0.50 0.50 4
MEAN (TOTAL) 0.48 0.52 (394)
Fall Permit Zone TN-L 4 0.25 0.75 4
5 0.10 0.90 10
6 0.30 0.70 54
7 0.38 0.62 60
8 0.41 0.59 37
9 0.30 0.70 10
10 0.56 0.44 9
11 0.67 0.33 6
12 0.00 1.00 l
MEAN (TOTAL) 0.36 0.64 (191)
Fall Bayport TN-S 4 0.00 1.00 2
Islands 5 0.19 0.81 21
6 0.24 0.76 100
7 0.22 0.78 49
8 0.38 0.63 16
9 0.22 0.78 9
10 0.00 1.00 4
11 0.00 1.00 1
MEAN (TOTAL) 0.23 0.77 (202)

62

 

 

 

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vHH o o H N N m mH om ON m 0 4-29 uHEHmm 0N\mo
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HOH H w b m m 4H m mN NH m N A128 uHEHmm mH\mo
NOH H o m w m m mH mv oN 9 0 4-29 uHEHom mN\¢o
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mN o o o m H HH 9 m o o o WMZB .um Ucmm OM\OH
H.4coov

 

.m XHUGOQQN

Appendix C.

Tagging and tag return data for all tags recovered during
1990 and 1991.

 

 

Tagging Tagging Tag Date Return

date location number returned location

11-04-89 Heisterman Is. 02158 04-90 Grid 1508
02263 04-15-90 Permit Zone
02155 07—02-90 Permit Zone
02211 11-14-90 Sand Point
02259 10-20-91 Permit Zone
00018 06-91 Permit Zone
00076 06-91 Permit Zone
00004 10-90 Heisterman Is.
00154 07-11-90 Permit Zone
00129 10-22-90 Permit Zone
00066 04-01-91 Grid 1507
00111 05-20-91 Permit Zone
00081 10-11—911 Sand Point
00149 . 10-20-91 Permit Zone
00107 10—28-91 Maisou Island
00147 10—30-91 Permit Zone
00116 11-20—91 Maisou Island
00031 03-15-91 Grid 1608
00008 10-12-91 Grid 1608

11-07—89 Permit Zone 00212 06—91 Permit Zone
00309 06—91 Permit Zone
00177 06—91 Permit Zone
00373 05-22—90 Permit Zone
00189 10-31-90 Permit Zone
00215 05-20-91 Permit Zone
00214 10—09—91 Sand Point
00235 10—30—91 Permit Zone
00231 05—28-91 Heisterman Is.

11-09—89 Sand Point 00567 06-91 Permit Zone
00429 10—90 Racine,

Wisconsin

00580 07—02—90 Permit Zone
00441 10-22-90 Permit Zone
00561 10—31-90 AuGres (Rifle B)
00572 11-01—90 Heisterman Is.
00683 05-21-91 Permit Zone
00500 10-20—91 Permit Zone

11—12-89 Sand Point 07907 06-91 Permit Zone
00841 06-91 Permit Zone
00838 04-90 Grid 1507
00796 04-90 Grid 1507
00870 10-24-90 Permit Zone
00851 10-31-91 Permit Zone
00946 10-11-91 Permit Zone
00847 10-30—91 Heisterman Is.
00939 10-30-91 Permit Zone
01381 06—91 Permit Zone

 

 

Tagging Tagging Tag Date Return

date location number returned location
01342 06—91 Permit Zone
01229 04-91 Permit Zone
01257 04-91 Permit Zone
01520 04-91 Permit Zone
01117 04-91 Permit Zone
01293 04-04-90 Permit Zone
01183 04-12-90 Grid 1507
01077 04-20-90 Grid 1408
01024 05—03—90 Grid 1408
01283 05-15-90 Grid 1507
01213 05-22-90 Permit Zone
01525 05-24-90 Permit Zone
01251 05—28—90 Permit Zone
01191 06-05-90 Permit Zone
01350 10-16—90 Grid 1608
01502 10-25-90 Heisterman Is.
01495 10—26-90 Heisterman Is.
01130 10-29—90 Heisterman Is.
01112 11-01—90 Heisterman Is.
01338 11-10-90 Sand Point
01055 11-14-90 Sand Point
01347 05—08-91 Permit Area
01500 11-14—91 Maisou Island
01041 10—20—91 Permit Zone
01029 10-22-91 Heisterman Is.
01501 10-28-91 Heisterman Is.
01220 10-30-91 Grid 1507
01289 10-31-91 Maisou Island
01486 11-01-91 Grid 1507
01084 10—23-91 Saginaw Bay
01115 10-23-91 Saginaw Bay

11-13—89 Permit Zone 07407 10-90 Heisterman Is.
07267 04-25—90 Permit Zone

11—13—89 Sand Point 07347 06-91 Permit Zone
07328 10-20-90 Heisterman Is.

11—14-89 Heisterman Is. 02112 NA NA
01905 Fall 91 NA
02356 11-90 s. Lake Huron
02310 10-90 Heisterman Is.
02127 04—19-90 Grid 1507
01648 04-22-90 Grid 1408
01819 05-03-90 Grid 1408
01758 05—04-90 Permit Zone
02011 06-04—90 Permit Zone
01953 06—27-90 Permit Zone
01680 06-27-90 Permit Zone
02319 08—24-90 8. Lake Huron
02348 10—22-90 AuGres, Rifle

Bar

02164 10-23-90 Heisterman Is.
00036 10-31-90 Heisterman Is.
02362 11—01-90 Heisterman Is.
01582 03-19-91 5. Lake Huron
01909 04—17—91 Grid 1507

66

 

 

Tagging Tagging Tag Date Return
date location number returned location
01754 10—20—91 Permit Zone
02181 10-25—91 Maisou Island
02064 10-28—91 Heisterman Is.
01564 10-29-91 Sand Point
01719 10-30-91 Permit (Oak Pt.)
01670 10-31-91 Maisou Island
02194 11-01—91 Heisterman Is.
01607 06-12-91 Grid 1608
01677 10-28-91 Saginaw Bay
04—12-90 Au Gres 08624 06-90 Au Gres
08225 06-20-90 Grid 1408
08709 04-15-91 Grid 1508
08992 04-17—91 Grid 1507
04-16—90 Permit 08504 04-91 Permit Zone
08815 04-20—90 Permit Zone
08517 05-24-90 Permit Zone
08514 06—20—90 Permit Zone
08511 05-20-91 Permit Zone
05-04-90 Permit 08548 06-20-90 Permit Zone
11-02-90 Permit 10516 03—91 s. Lake Huron
11-03—90 Heisterman Is. 10156 04-91 Grid 1609
10073 03-25-91 Grid 1508
10077 04-24—91 Saginaw Bay
10074 06-02-91 Permit Zone
10174 10-11-91 Permit Zone
10297 04-18-91 Grid 1707
11-03-90 Sand Point 10635 06-91 Permit Zone
10716 05-20-91 Permit Zone
10627 06—18-91 Permit Zone
10180 10—10—91 Sand Point
10796 10-31—91 Maisou Island
10721 11-15—91 Maisou Island
10242 04-91 Permit Zone
10226 04-18-91 Permit Zone
10995 07-14-91 Grid 1407A
10902 11-08-91 Grid 1507
09048 11-08-91 Grid 1507
10985 11-10—91 Grid 1507
08019 07—14-91 Grid 1407A
08016 10-18—91 Grid 1507
11—09—90 Heisterman Is. 09979 NA NA
09779 06-91 Permit Zone
09778 06-91 Permit Zone
09774 04-91 Permit Zone
09529 Fall 91 NA
09337 03-29—91 Grid 1508
09486 04-01-91 Grid 1408
09995 04—05-91 Grid 1507
09019 04-18—91 Grid 1508
09986 05—10-91 Bay City (1707)
09673 06-06—91 Permit Zone
09881 10—10-91 Sand Point
09651 10—23—91 Sand Point

67

 

 

Tagging Tagging Tag Date Return
date location number returned location
09357 10—29-91 Sand Point
09912 10—31-91 Maisou Island
11-10-90 Sand Point 08766 07-15—91 Grid 1608
08364 06-91 Permit Zone
02473 04—25-91 Permit Zone
08876 11-01-91 NA
11-14—90 Heisterman Is. 8848 04-25-91 Grid 1507
7632 06-91 Heisterman Is.
7130 Fall 91 Heisterman Is.
7191 04—23—91 Heisterman Is.
7032 10—22-91 Heisterman Is.
Unknown Unknown Unknown 04—91 Permit Zone
06—91 Grid 1508
06-91 Grid 1508
06-91 Grid 1508
06-91 Grid 1508
03-90 Grid 1507
03—90 Grid 1507
05-90 Grid 1410
05-90 Grid 1410
04—05-90 Grid 1507
04-05-90 Grid 1507
05—24—91 Grid 1507

 

 

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