THE DISTRIBUTION, ECOLOGY, AND MANAGEMENT OF
THE LAKE STURGEON (ACIPENSER FULVESCENS
RAFINESQUE) IN MICHIGAN
by
James Philip Baker
A thesis submitted in partial fulfillment
of the requirements for the degree of
Master of Science
(Natural Resources)
in The University of Michigan
1980
Committee members: -
Dr. Alvin L. Jensen, Chairman
Dr. William C. Latta
ACKNOWLEDGMENTS
This study was supported jointly by the Threatened and Endangered
Species and the Living Resources programs of the Michigan Department of
Natural Resources. I would like to thank Mason Shouder, Fisheries
Habitat Biologist, Michigan Department of Natural Resources, for providing
me with much of the raw data for this investigation and with the benefit of
his wide experience with lake Sturgeon. Logistical support was furnished
by the Institute for Fisheries Research of the Michigan Department of
Natural Resources.
I am deeply indebted to Dr. Alvin L. Jensen, the chairman of
my committee, for his advice and encouragement. I offer my sincere
gratitude to Dr. William C. Latta and Mr. James R. Ryckman of the
Institute for Fisheries Research for their guidance and assistance
throughout the project. I would also like to thank Mr. Alan Sutton for
drafting the figures and Mrs. Margaret McClure for typing the manuscript.
Finally, I wish to express my sincere thanks to my mother and grandmother
for their encouragement and support throughout the study.
ii
TABLE OF CONTENTS
ACKNOWLEDGMENTS . . . . . . e e s e e s • e s • e • * * *
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . .
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . .
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . .
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . .
BRIEF HISTORY OF THE LAKE STURGEON FISHERY IN
MICHIGAN WATERS
SYNOPSIS OF THE LIFE HISTORY OF THE LAKE STURGEON.
DISTRIBUTION OF THE LAKE STURGEON IN MICHIGAN WITH
NOTES ON THE FISHERIES . . . . . . . . . . . . . . . . . . .
ESTIMATES OF FISHING PRESSURE AND CATCH PER
UNIT EFFORT . . . . . . . . . . • * * * * * * * * * * * * * * *
POPULATION AND EXPLOITATION ESTIMATES . . . . . . . .
STOCK ASSESSMENT . . . . . - e. e. e. e. e. e o e º e º O e o e º O &
Growth in Length and Weight . . . . . . . . . . . . . .
Mortality . . . . . . . . . . . . . . . . . . . . . . . .
Yield per Recruitment . . . . . . . . . . . . . . . . .
MANAGEMENT RECOMMENDATIONS . . . . . . . . . . . . .
LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . .
iii
Page
ii
iv.
vi
13
22
34
40
48
49
56
64
78
90
Table
LIST OF TABLES
Total lake sturgeon landings (in thousands of
pounds) by Michigan commercial fishermen from
the Great Lakes (including Lake St. Clair) from
1879 through 1970 . . . . . . . . . . . . . . . . . ... O C &
Annual lake Sturgeon spearing harvest in Burt,
Mullett, and Black lakes, 1974-1980 . . . . . . . . .
Rivers in which lake sturgeon have been reported
during the last 10 years . . . . . . . . . . . . . . .
Estimates of effort and catch per unit effort for
the spear fishery of Black Lake, 1975-1976 . . . . .
Estimates of population size and exploitation rates
for lake sturgeon, Black Lake, 1973-1976 . . . . .
Observed and predicted values of length (inches) at
each age for Michigan lake Sturgeon . . . . . . . .
Year classes, assigned ages, and frequencies of
lake sturgeon netted in Black Lake, 1970-1976
Multipliers of the instantaneous fishing rate used
in the Ricker yield model and corresponding rates
of exploitation
Estimation of annual recruitment to the fishable
stock in Black Lake
Page
25
31
37
46
52
58
65
76
iv
Figure
LIST OF FIGURES
Year class frequency of lake sturgeon speared.
and netted in Black Lake, 1970-1977 . . . . . . . . .
Questionnaire regarding lake sturgeon distribution . .
Combined empirical length-age relationship for lake
sturgeon from the Menominee River and the inland
lakes, with fitted von Bertalanffy curve . . . . . . .
Yield in pounds per thousand age-1 recruits as a
function of age at entry into the fishery, xc , and
the instantaneous fishing mortality rate, F
Yield per recruitment as a function of the instan-
taneous fishing mortality rate for different levels
of natural mortality with recruitment at age 1 year
and entry into the fishery at age 22 years . . . . . .
Yield per recruitment as a function of age at entry
into the fishery for two instantaneous rates of
fishing mortality, F . . . . . . . . . . . . . . . . .
Length frequency of lake sturgeon speared in Black
Lake, 1974-1979 -
Percent composition of Black Lake sturgeon harvest
by individual years 1974-1979, for two length
classes
Page
23
51
67
69
71
80
82
ABSTRACT
Significant populations of lake sturgeon exist in Burt, Mullett,
and Black lakes, Cheboygan and Presque Isle counties; the Menominee
River, Menominee County; and Lake St. Clair and the St. Clair River.
Remnant populations of lake sturgeon exist in all of the Great Lakes and
lake sturgeon are occasionally reported in the lower reaches of most of
the larger rivers draining into the Great Lakes. Landlocked remnant
populations of lake Sturgeon are found in Otter Lake, Houghton County;
Manistique Lake, Mackinac and Luce counties: Indian Lake, Schoolcraft
County; Brevoort Lake, Mackinac County; and Monacle Lake, Chippewa
County.
On Black Lake estimated fishing pressure in 1975 during the
winter spearing season was 2, 332 shanty hours and in 1976, 3,972 hours.
Estimated catch per hour was 0.0142 sturgeon in 1975 and 0. 0.086 in 1976.
The population of lake Sturgeon 48.6 inches and larger in Black Lake WalS
estimated to be 1,599 in 1975, with 95% confidence limits of 714 to 3,998.
The rate of exploitation in 1976 was estimated to be 2.1%.
The growth rates of lake sturgeon from Black and Mullett lakes
and the Menominee River were very similar. The parameters of the
von Bertalanffy growth equation for a combined sample of lake sturgeon
from these waters were L 22= 69. 6411 inches, K = 0.0558, and Xo f
-0. 8815. The allometric mean length-mean weight relationship for lake
Sturgeon from the same localities was 26mW = 8. 8949 + 3. 1393 -čni.
vi
The annual mortality rate for Black Lake sturgeon, age 25 years
and older, was 0.097, the instantaneous total mortality rate 0.102. A
fishing rate of 0.026, corresponding to an exploitation rate of 2.5% was
assumed for the purpose of evaluating yield per recruitment. Using this
rate, the natural mortality rate was calculated to be 0.076. The
instantaneous total mortality rate for the Menominee River population
was 0.098.
Fishing regulations for lake sturgeon were evaluated using
Ricker's equilibrium yield model. Growth and mortality rates Of lake
sturgeon from Black and Mullett lakes and the Menominee River were used
in the equation. With age at entry into the fishery held Constant at 22 years,
a doubling of the Original fishing rate (2.5%) causes a 51% increase in yield
per recruitment and reduces the biomass of the spawning stock by about
50%. Since the relationship between the size of the spawning stock and the
number of recruits produced is unknown, it seems prudent to protect the
stock of sexually mature fish if exploitation increase.
The mean annual recruitment to the fishable stock of the Black
Lake population was 4.8%. Annual harvest should not exceed annual
recruitment. The maximum allowable catch for Black Lake was calculated
to be 77 fish. The winter spear fishery, which takes 20 to 40 fish yearly,
appears to be operating with a considerable margin of safety.
The 50-inch minimum size limit currently in effect appears
adequate to protect the fish until they become sexually mature. The
apparent size limit in the winter spear fishery is higher than the legal
vii
minimum size limit. Validation of speared Sturgeon by Michigan
Department of Natural Resources biologists should be continued. If
more stringent regulations become necessary in the future, decreasing
the length of the season would be a more enforceable method of limiting
harvest than increasing the minimum size limit. Controls on the
poaching of spawning sturgeon in the upper Black River above Black
Lake should be strictly enforced. The taking of lake sturgeon during
the months of May and June should be prohibited statewide to protect
spawning sturgeon in the St. Clair River and elsewhere. The season
creel limit for lake Sturgeon Statewide should be decreased from two
to one to promote the status of the sturgeon as a trophy fish.
viii
INTRODUCTION
The lake sturgeon (Acipenser fulvescens Rafinesque) is a member
of the family Acipenseridae, a group of fishes which displays such primitive
characteristics as a cartilaginous skeleton, a heterocercal tail, rows of
large, bony plates instead of scales and a large, cellular swim bladder.
A detailed description of the lake sturgeon can be found in Scott and
Crossman (1973).
There are 25 species of Sturgeons, and representatives of this
family are found throughout Europe, Asia, and North America. Seven
species are native to North America, of which four are anadromous,
Spending most of their lives in the sea. The remaining three species live
entirely in fresh water. They include the lake sturgeon, the shovelnose
Sturgeon (Scaphirhynchus platorhynchus Rafinesque), and the pallid
Sturgeon (Scaphirhynchus albus Forbes and Richardson). The shovelnose
and pallid sturgeons are found only in the Mississippi River drainage.
The lake Sturgeon has the widest distribution of the three
freshwater sturgeons, occurring throughout the Mississippi, Great Lakes,
and Hudson Bay drainages. It is the only sturgeon found in Michigan waters.
Harkness and Dymond (1961) give a detailed account of the distribution of
the lake sturgeon. It is now a rare fish throughout most of its range due
to overexploitation of the stocks by commercial fishermen during the last
Century and destruction of Spawning habitat by dams and pollution. It is
officially classified as rare by the U. S. Department of the Interior (1966)
1
2
and threatened by the Michigan Department of Natural Resources (1976).
Because of the current status of the lake sturgeon as a threatened species,
this study was initiated in the hope that information thereby procured
could be utilized in the future management of Michigan's remaining
populations.
Most study of the lake sturgeon has been carried out in Canada,
where it remained an important commercial fish well into this century.
The life history of the lake Sturgeon in Canada has been intensively
investigated and has been documented by Harkness and Dymond (1961) and
Scott and Crossman (1973). In Wisconsin, the lake sturgeon is the object
of an important winter spear fishery in several large inland lakes
(Winnebago, Winneconne, Poygan, and Butte Des Morts) and various
aspects of this fishery have been examined by Priegel and Wirth (1975,
1977, 1978).
The literature concerning lake sturgeon populations in Michigan,
by contrast, is depauperate. Williams (1951) and Fogle (1975) have
published general articles on lake sturgeon, and some analyses of cree
census data collected during the spearing season on Black, Mullett, and
Burt lakes have been completed (Vondett 1975; Vondett and Williams 1961).
The sturgeon fishery of the Menominee River, a border stream between
Michigan and Wisconsin, has been surveyed by Priegel (1973). Shouder
(1975) attempted to estimate the size of the lake sturgeon population in
Black Lake but had only limited success.
3
It is the intention of this investigation to assess the various
lake sturgeon stocks of the state of Michigan with respect to distribution,
ecology, and population size; to identify local populations of lake
sturgeon heretofore undocumented, and to evaluate the adequacy of
current sturgeon management practices.
BRIEF HISTORY OF THE LAKE STURGEON FISHERY
IN MICHIGAN WATERS
No other freshwater species has had such a broad spectrum of
economic value as had the lake Sturgeon. Before the middle of the 19th
century, it was considered a worthless nuisance. Today, the flesh and
roe of the lake sturgeon command higher prices per pound than any other
freshwater fish. -
Before the appearance of the white man in North America, the
lake sturgeon was exceedingly abundant throughout its range, particularly
in the Great Lakes region. Tody (1974) estimated the standing crop of
lake sturgeon in the Great Lakes prior to 1830 to be in the tens of millions
of pounds. Sturgeon were utilized to varying degrees by several Indian
tribes. Due to its great size, a Single Sturgeon would provide, as much
food as many smaller fish, and the oily flesh was easily smoked. Harkness
and Dymond (1961) state that the Jesuit Relations (historical writings of
early French missionaries) contain numerous accounts of the use of lake
sturgeon by the Indians, and that Pere Francis Xavier Charlevoix, Writing
in 1761, outlined one of the methods by which the Indians captured sturgeon.
Though the Sturgeons have always been held in high regard in
Europe (particularly eastern Europe), and Russia, early white settlers
in North America considered the lake sturgeon to be a trash fish. The
bony plates of the small Sturgeon and the weight of the large ones ruined
5
fishermen's nets, which were set for more valuable fishes such as
whitefish, lake herring, and lake trout. Lake sturgeon taken incidentally
in commercial fishing operations were often piled on the beach like
cordwood and burned. There is an account in Harkness and Dymond
(1961) of sturgeon being used in place of wood to fire the boilers Of
Steamships on the Great Lakes. At this time (prior to 1860), the flesh
was considered fit only for Indians and half-breeds (Wing 1890) and the
roe was worthle SS.
The value of the lake Sturgeon as a commercial species began
to be realized about the time of the Civil War, when it was discovered
- that caviar could be produced from the roe, and that Smoked Sturgeon
WalS a.ſ.l. acceptable substitute for smoked halibut. A Sturgeon processing
plant was established at Sandusky, Ohio, in 1860 (Harkness and Dymond
1961). By 1872, it was handling between 10 and 18 thousand lake
Sturgeon, of an average weight of 50 pounds each, annually (Milner 1874).
The flesh was smoked, caviar was made from the roe . the Offal was
rendered for its oil, and isinglass (a clarifying agent used in beer and
wine) was produced from the swim bladders. Even at this time, Milner
remarks that Sturgeon caught in Green Bay, Lake Michigan, were still
being wantonly destroyed. The Ninth Biennial Report of the Michigan State
Board of Fish Commissioners (1890) documents the existence of a caviar
factory in Algonac, which processed sturgeon taken in the many channels
of the St. Clair River.
After the commercial value of the lake sturgeon was established,
fishing pressure on the species increased tremendously and the stocks
6
began a rapid decline to very low levels from which they have never
recovered. Although formal catch records are incomplete, Tody (1974)
reported that in 1880, the landings of lake sturgeon in Michigan amounted
to 4, 300,000 pounds. By 1890, the total landings had fallen to 1,481,000
pounds, and in 1900, only 177,000 pounds of lake surgeon were harvested.
The dramatic drop in lake Sturgeon landings from the very high levels of
the 1880's is illustrated in Table 1.
As it became evident that the lake sturgeon fishery was in dire
straits, interest in the artificial propagation of the species began to
develop. The first documented attempt to artificially hatch lake sturgeon
eggs took place on the Detroit River between 1883 and 1887. This
information was recounted by the President of the American Fisheries
Society during the discussion of a paper by Carter (1904). Over the next
25 years, further attempts to propagate Sturgeon were made at Algonac,
Michigan, in 1889 (Post 1890), the Detroit River in 1890 (Leach 1920),
1893 and 1894 (Michigan State Board of Fish Commissioners 1895), the
Missisquoi and Lamoille rivers of Vermont in 1900 and 1901 (Stone 1901),
and Lake of the Woods, Minnesota in 1911 and 1912 (Eddy and Surber 1943).
None of these endeavors met with anything more than limited success.
There were a number of recurrent problems which beset all
attempts at sturgeon culture. Perhaps the greatest was the difficulty
of securing ripe male and female fish at the same time. Another problem,
related to the first, was the scarcity of truly ripe females among those
participating in the spawning migration. As an example, Post reported
7
Table 1. --Total lake sturgeon landings (in thousands of pounds) by Michigan
commercial fishermen from the Great Lakes (including Lake St. Clair)
from 1879 through 1970.
*-a-
Year Lake - * Total
- Erie St. Clair Huron Michigan Superior
1879 - 999 204 gº ſº wº 1, 202+
1880 tº sº º tºº º * …
1881 º tº. tºº tº º gºe * >
1882 gº ame tº tº º º
1883 tºº gº gº tºº ans eme
1884 wº tºº - • º ( * >
1885 91 228 216 9.25 131 1, 591
1886 tºº tº *s ſº gº $º
1887 * - tºº gº gº sº * -º
1888 dº - tº- gº - * -->
1889 2 97 559 475 83 1, 216
1890 33 309 366 733 40 1,481
1891 22 76 398 254 75 825
1892 14 96 179 196 40 525
1893 17 101 201 107 31 457
1894 13 62 87 112 21 295
1895 13 30 92 84 6 225
1896 56 28 48 83 10 225
1897 46 33 36 58 8 181
1898 47 21 91 68 9 236
1899 41 19 85 64 9 218
1900 48 19 23 76 11 177
1901 27 9 22 69 5 132
1902 17 3 25 38 23 106
1903 17 2% 34 50 8 109
1904 16 1 32 46 6 101
(continued, next page)
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Table 1. --concluded.
Year Erie St. Clair #. Michigan Superior Total
1955 G- 1 2 # 3+
1956 tº- 1 1 * 2+
1957 tºº >; 1 + 1+
1958 ſº 1 1 >; 2+
1959 me 1 1 >; 2+
1960 >}< 1 1 >k 2+
1961 >k 1 2 >}< 3-H
1962 >; 1 1 * 2+
1963 Sk 1 3 3% 4+
1964 - 1 3 >k 4+
1965 º >; 2 >; 2+
1966 <- >}< 2 1 3+
1967 º 1 >k tº º 1+
1968 tº- >}< 2 >}< 2+
1969 tº >; 3 tºº 3+
1970 -> tº - tº-º . ->
Taking of lake sturgeon prohibited December 1, 1970.
*-
# Includes Detroit and St. Clair rivers.
º Landings unknown.
* Landings amounted to less than 500 pounds.
a Commercial fishing in Michigan waters of Lake St. Clair prohibited in 1909.
b
A number followed by a + indicates that the number is a minimum, i.e., the
landings from one or more lakes are unknown.
Data included in Table 1 were taken from Baldwin and Saalfeld (1962) and Great
Lakes Fishery Commission (1970 and unpublished).
10
that although he and his co-workers at Algonac handled some 4,000
Sturgeon, only two ripe females were found. Still another complication
was that the lake Sturgeon eggs seemed to be especially susceptible to
attack by fungus.
The last documented attempt at artificial lake sturgeon culture
was made by Harkness in 1924. Several thousand sturgeon fry were
hatched in Seth Green floating boxes in the Gull River about 20 miles
above Lake Nipigon, Ontario. Attempts to rear the fry failed, as no
Suitable food could be found for them (Harkness and Dymond 1961).
Declining sturgeon Stocks brought a trend toward increasingly
Stringent fishing regulations. In the 13th Biennial Report of the Michigan
State Board of Fish Commissioners (1899) the statistical agent of that
body recommended the prohibition of the taking of small sturgeon and
Curtailment of the use of unbaited set-lines (used to grapple sturgeon
*S they roll and root about on the bottom during spawning). Whether
or not these suggestions were followed is unclear. but in any case the
decline in the sturgeon catch continued. By 1929, the catch had dropped
to such low levels that the taking of lake sturgeon, both commercially and
for Sport, was prohibited statewide.
Beginning in 1948, a limited sport fishery was allowed during the
nonths of January and February on inland lakes open to spearing. The -
**gulations governing this spear fishery during 1948 and 1949 are somewhat
Vague. - In 1950, spearing through the ice was allowed on Lake St. Clair.
°ommercial fishermen were allowed to sell Sturgeon taken incidentally in
11
their nets beginning in 1951 williams 1951). Hook-and-line fishing for
Sturgeon became legal in 1952. Commercial fishing for lake sturgeon
in Lake Erie ended in 1964 and in 1970, Lakes Huron, Michigan, and
Superior were closed.
The size limit on lake sturgeon taken by sport fishermen was
set at 36 inches when the season was first reopened in 1948. It was
Subsequently raised to 42 inches in 1952 and 50 inches in 1974. The
Creel limit for lake sturgeon taken in Lake St. Clair and inland waters
has remained set at two fish per season since 1951. -
Fishing regulations for the Menominee River have generally
been formulated by the state of Wisconsin, but have followed a pattern
of increasing size limits and decreasing creel limits similar to that
of Michigan.
Since lake sturgeon are highly vulnerable to capture during the
Spawning migration, regulations aimed at protecting the fish on their
Spawning run have been applied in one particular case. The Upper Black
River from its confluence with Black Lake to Kleber Dam, the major
Spawning area for the sturgeon population of Black Lake, is closed to
all fishing during the months of April and May.
Current (1980) fishing regulations concerning lake sturgeon in
Michigan waters are listed below.
12
Hook-and-line seasons
Trout streams,
designated trout lakes No Open season
Non-trout streams,
inland lakes January 1-February 29
Great Lakes, Lake St. Clair,
Detroit, St. Mary's, and
St. Clair rivers No closed season
Menominee River September 1–November 1
Spearing season
February, on non-trout waters.
All sturgeon speared in Black, Burt, or Mullett lakes must be
validated at the Indian River DNR field office or at the Black
Lake Hotel within 48 hours.
Size limit (includes both spearing and hook-and line): 50 inches.
Creel limit (includes both spearing and hook-and-line):
two per season.
Special provisions:
Cheboygan County: During April and May, unlawful to fish in any
manner on the Black River between Kleber Dam and the Red Bridge
(Sec. 5, T 3.5 N, R 1 E). (This regulation is to protect spawning
lake sturgeon, which run upstream from Black Lake. )
SYNOPSIS OF THE LIFE HISTORY OF THE LAKE STURGEON
A brief account of the biology of the lake sturgeon follows with
special regard (where possible) to the populations of Michigan. Lake
Sturgeon are exclusively bottom feeders, preferring large, shallow lakes -
and large rivers with abundant bottom fauna such as mayfly nymphs,
fingernail clams, crayfish, caddis flies, and chironomid larvae. Although
Small fishes are occasionally found in the stomachs of sturgeon, they
constitute only a miniscule portion of the diet.
Lake sturgeon live to the greatest age of all the freshwater fishes.
There is a documented account of a 208 pound fish, taken in Lake of the
Woods, Ontario in 1953, which was determined to be 152 years old
(MacKay 1963). The oldest lake Sturgeon ever taken from Michigan
waters (of which the writer has knowledge) was a 98 year old fish speared
in Mullett Lake in 1975. Ages are generally determined by examination
of the annular rings in a cross section of the ossified first ray of the
pectoral fin (Cuerrier 1951). This fin ray can easily be removed with a
hacksaw and a pocket knife with no harm to the living fish. Age can also
be ascertained from annular markings in otoliths and opercular bones,
but these methods require the sacrifice of the fish. All age data used in
this study were determined from fin ray sections. Very old sturgeon are
exceedingly difficult to age accurately. Age determinations of very large
fish are probably accurate only to within 5 or 6 years.
13
14
Lake sturgeon in Michigan leave their home lakes and move up
rivers to spawn during the months of May and June, depending upon the
water temperature. Priegel and Wirth (1977) stated that lake sturgeon
in Wisconsin usually spawn when the water temperature reaches 53 F,
but noted that, during years of low water discharge and more rapid
increases in water temperature, they may spawn at temperatures of
58–59 F. I obse rved lake sturgeon on their spawning run in three
different localities in May and June of 1979. Locations, dates, and
water temperatures were -- Indian River, Schoolcraft County:
May 22-23: 53 F; Black River, Cheboygan County: May 24: 52 F; and
St. Clair River, St. Clair County: June 16: 52 F. Michigan lake
- sturgeon spawn at water temperatures very similar to those observed
in Wisconsin.
The spawning act takes place in rapids and deep pools, where
the current is swift enough to provide a substrate of large, clean rubble.
Lake spawning is also known to occur, mainly in wave-swept areas where
the bottom is composed of large rubble. No nest is constructed; the eggs
and milt are scattered over the bottom where the fertilized eggs adhere
to the rocks. The eggs receive no parental care.
Very little is known of the life of the lake sturgeon, from the time
the eggs are deposited until the end of the first growing season. Harkness
and Dymond (1961) reported that at water temperatures of 60-64 F lake
Sturgeon eggs hatched in 5 to 8 days and that newly hatched fry were 1/3 inch
in length. It is not known how long the lake sturgeon fry remained in the
15
river before descending to the lake. Shouder (1975) reported that attempts
to capture small lake Sturgeon in the upper Black River during August 1973,
were unsuccessful. No lake Sturgeon younger than 9 years old has ever
been captured in Black Lake. However, the continual appearance of new
year classes in the monitoring nets led Shouder to conclude that reproduction
was taking place and that the construction of a dam on the upper Black River
in 1949 had not adversely affected reproduction. Information concerning
year class strength gathered since the time of Shouder's study supports
this conclusion. The year class frequencies of Black Lake sturgeon netted
and speared from 1970 through 1977 are illustrated in Figure 1. Year
classes more recent than 1955 are onitted, as these cohorts were
inadequately sampled by the fishing gear.
Young-of-the-year lake sturgeon have been found in significant
numbers in the Menominee River (Priegel 1973) and several very small
Sturgeon have been taken by Department of Natural Resources research
vessels in Lake St. Clair.
Growth of the lake Sturgeon is quite rapid during the first 10 years
of life, then slows down and becomes extremely variable among different
individuals. As an example of this variability, one sturgeon tagged in 1973
was 51. 75 inches long. When recaptured in 1974 it had grown to 53.25
inches, an increase of 1.5 inches in a single year. In contrast, a 48-inch
Sturgeon which was tagged in 1974 was recaptured in 1975 and had not
grOWn at all.
16
33O
+: - Before Kleber | After Kleber
} Dam | Dam
|
-C 25H |
C
CU |
-C
Q2 20H | \ n = 351
CU, |
Q1)
Cl |
Cſ) |
15H
C. |
O
QD |
S) |
E 10H |
C/D |
3 |
5F |
Q1) |
£ |
= _l | | | |
1935 194O 1945 1950 1955
Year Class

Figure 1. --Year class frequency of lake sturgeon speared
and netted in Black Lake, 1970-1977.
17
The largest lake sturgeon ever taken in Michigan, for which
there is documentation, was 7 feet 11 inches long and weighed 310 pounds
(Van Oosten 1956). A photograph of this leviathan is included in the July-
August (1943) issue of Michigan Conservation magazine (Vol. 12, No. 6,
p. 11). It was captured by swimmers in 1943 in Lake Michigan, near the
mouth of the St. Joseph River. It had apparently been injured by a
collision with a boat propeller. -
The current state angling record for lake sturgeon is a 193
pound fish, speared in Mullett Lake in 1974. However, most sturgeon
taken by spearers during the February season are 4 1/2 to 5 feet long
and weigh 45 to 60 pounds.
Priegel and Wirth state that male lake sturgeon in Wisconsin
reach sexual maturity at 14-16 years of age, and females at 24-26 years
old. Also, instead of spawning every year, females spawn only once
every 4 to 6 years, while males may spawn every other year. Because
of the similarity of latitude and length of the growing season, it is felt
that these ages at maturity and intervals between successive spawnings
also apply to Sturgeon in Michigan waters Mason Shouder, personal
communication).
Roussow (1957) reported that the spawning periodicity of lake
Sturgeon could be determined by examination of the spacing of the annuli
in the pectoral fin ray cross sections. According to Roussow, the growth
Of the sturgeon in the years just prior to the year of spawning is quite
slow, resulting in a series of annuli located very close together. After
18
the year of spawning, the growth rate increases, and this increase is
reflected in the wider spacing of subsequent annuli. As the fish begins
to produce sex products prior to the next spawning, growth slows down
again and the cycle is repeated.
I examined the fin ray sections of 32 lake surgeon in an attempt
to determine the spawning periodicity of Michigan populations, but could
not distinguish the wide and narrow bands of annuli which Roussow
discussed. The sturgeon upon which Roussow conducted his investigations
were taken from lakes in northern Quebec, where the growing season is
much shorter. It is possible that Michigan lake Sturgeon, having a longer
growing season, do not suffer from as great a disruption in growth during
the formation of the sex products as do fish from areas farther north.
Natural mortality in lake sturgeon is very low throughout most of
the life span. By the end of the second growing season, the average
length of a lake sturgeon is nearly 12 inches, thus rendering them too
large a prey for all but the largest of the predatory fishes. The sharp,
bony plates in the skin also make them a very unpleasant mouthful.
There are no records to indicate that young lake sturgeon have ever
been found in the stomachs of any other fish, but this might reflect the
Scarcity of the prey rather than its lack of utilization by predators.
Once a lake sturgeon has reached about 20 inches in length (about 5 years
of age) its size has rendered it an unfit prey even for the large muskellunge.
From this point on, the chief predator of the lake sturgeon is man.
19
Male and female lake sturgeon are apparently subject to different
rates of mortality after the first 10 or 15 years of life. Among the older
and larger sturgeon there is a predominance of females.
The sex ratio for 151 lake sturgeon 50 inches and larger taken
from Black and Mullett lakes by spear fishermen during the years 1974-
1979 was 71% female and 29% male. Among larger fish the preponderance
of females was even greater. Eighty percent of the sturgeon over 60 inches
long were females, and among fish 70 inches and larger, 86% were females,
This imbalance of the sex ratio is known to occur in other lake sturgeon
populations. - Probst and Cooper (1955) reported that 96% of the lake
Sturgeon over 59 inches long speared in Lake Winnebago were females.
Probst and Cooper attributed the predominance of females among larger
Sturgeon to either a longer natural life span for females or a lower rate
Of exploitation, suggesting that males might be subjected to a significant
illegal harvest in the rivers during the spawning run. The latter might
indeed be the case for at least one Michigan population. Even though the
upper Black River above Black Lake is closed to all fishing during April
and May, poaching of spawning Sturgeon remains a serious problem
(Eugene Elsenheimer, conservation officer, personal communication).
Mason Shouder (personal communication) has speculated that most of the
mortality not directly attributable to legal fishing in the Black Lake population
can be attributed to the illegal harvest of Sturgeon during the spawning run.
Lake sturgeon compete with other bottom-feeding fishes for
the same food items. Probably the greatest competitors with the lake
20
sturgeon for food are the various species of suckers (Catostomidae).
However, the extent of this interspecific competition is not known.
Lake Sturgeon are hosts to a variety of parasites. The most
Serious of these are the lampreys. The sea lamprey (Petromyzon
marinus) is known to attack and even kill large lake Sturgeon in the
Great Lakes. In Black Lake, sturgeon are parasitized by the smaller
Silver lamprey (Ichthyomyzon unicuspis). The extent of parasitism by
the silver lamprey in Black Lake is not known, but two of the first three
Sturgeon speared in Black Lake in 1980 were found to have lampreys
attached to them. I identified one of the lampreys taken from these fish
as L. unicuspis.
Hoffman (1967) listed 12 parasites found in lake Šturgeon.
Margolis and Arthur (1979) listed the following 17 parasites of lake
Sturgeon: Monogenea, 3 species; Trematoda, 8 species; Nematoda,
3 species; Acanthocephala, 1 species; Hirudinoidea, 1 species; Branchiura,
1 species. Neither of these lists include the Coelenterate Polypodium sp.
Which has been found in the ovaries of Sturgeon taken in Black Lake
(Hoffman et al. 1974). This is the only North American record of this
unique parasite. About 20% of the female sturgeon in Black Lake are
believed to be infested with Polypodium in varying degrees (Mason Shouder,
personal communication). John Hnath, fish pathologist for the Michigan
Department of Natural Resources, and I examined for parasites in
December 1979, a dead male lake sturgeon, 35 inches long and weighing
10 pounds, 2 ounces. This fish was captured alive, but floundering, in
21
the Saginaw River (Saginaw County) within the city limits of Saginaw in
late July 1979. The only parasites found were a single specimen of
Cucullanus chitellarius, found in the hind gut, and 23 specimens of
Spinitectus gracilis from the esophagus, both species being nematodes.
These are tentative identifications, done by Hnath, and are included
because there are so few records of lake sturgeon parasites for
Michigan populations.
very little is known concerning the bioaccumulation of chemical
toxicants by lake sturgeon. The lake sturgeon has very fatty flesh and
lives to great age, which suggests that it could accumulate high
concentrations of fat soluble toxicants such as chlorinated hydrocarbon
pesticides and polychlorinated biphenyls (PCB's). Evans et al. (1972)
reported that 1970 mean mercury levels in lake Sturgeon taken from
Lake St. Clair and the St. Clair River were 2. 0-3.0 ppm.
DISTRIBUTION OF THE LAKE STURGEON IN MICHIGAN
WITH NOTES ON THE FISHERIES
In order to identify existing lake Sturgeon populations, a
questionnaire was sent to all Michigan Department of Natural Resources
regional and district fishery biologists, fishery habitat biologists, and
Great Lakes research stations (Fig. 2). Each questionnaire was followed
up by a telephone interview within 2 weeks so that responses might be
obtained more quickly. The results of this questionnaire survey, and of
Subsequent field investigations that I conducted are discussed below.
There are three significant populations of lake sturgeon known
to exist in Michigan. These populations are located in:
() Burt, Mullett and Black lakes in the Cheboygan
River system, Cheboygan and Presque Isle counties;
(2) the Menominee River, a boundary stream between
Wisconsin and the Upper Peninsula (chiefly Menominee
County); and
(3) Lake St. Clair and the St. Clair River.
Burt, Mullett, and Black lakes
The populations of Burt, Mullett, and Black lakes are
essentially landlocked, connection with Lake Huron having been
blocked by a dam with lock on the Cheboygan River in the 1920's.
22
23
LAKE STURGEON QUESTIONNAIRE
Do you have any lake Sturgeon in your district 2
Have you had any reports of Sturgeon in your district 2
If a population of lake Sturgeon is present, where is it located ?
(Please give county, township, range, section, and site.)
How recent is your latest information concerning the existence
of sturgeon in your district 2
Do you have any information regarding the size of the population(s)?
Do you have any specific biological information (lengths, weights,
exploitation, etc.) about the population(s)?
Do you know of anyone else who might have information about
sturgeon populations in your district 2
Figure 2. --Questionnaire regarding lake sturgeon distribution.
24
The lakes have supported a significant winter spear fishery since 1948.
Characteristics of this fishery were described by Williams (1951). The
Michigan Department of Natural Resources has closely monitored the
fishery in these lakes since 1974. It is known that Black Lake (the
Shallowest of the three lakes) has a substantial population of Sturgeon,
and most of the annual harvest is taken there. However, the largest
surgeon taken each year invariably come from Mullett Lake. No
Sturgeon have been speared in Burt Lake since 1974, and the population
there is believed to be very Small. Fishermen no longer actively pursue
lake sturgeon in Burt Lake, the fishery now being confined to Mullett and
Black lakes.
- Since 1974, all successful Sturgeon spearers on Burt, Mullett,
and Black lakes have been required to have their catch verified and tagged
by a state fishery biologist within 48 hours. Thus, the total catch is known
for each of these three lakes for the past 7 years (Table 2). In these
years a total of 203 lake sturgeon have been harvested by sport fishermen,
166 from Black, 36 from Mullett, and 1 from Burt Lake.
The upper Black River, from its confluence with Black Lake to
Kleber Dam, is the principal spawning area for the Black Lake population.
In 1972, four artificial spawning reefs were built in the river to provide
the spawning sturgeon with more suitable substrate. In 1973, the Northern
Michigan Electric Coop., Inc. (which owns and operates Kleber Dam)
agreed to provide a minimum flow of approximately 80 cfs from May 1
through July 31 each year. This minimum flow serves to keep the artificial
25
Table 2. --Annual lake Sturgeon spearing harvest in Burt, Mullett,
and Black lakes, 1974-1980.
Lake
Year Burt Mullett Black Total
1974 1 9 13 23
1975 0 1 33 34
1976 * 0 7 34 41
1977 0 0 29 29.
1978 0 4 24 28
1979 0 9 19 28
1980 0 6 14 20
Total 1 36 166 203
26
spawning reefs submerged and free of silt during the spawning season
(Shouder 1975). Sturgeon are also known to run down the lower Black
River, as far as Alverno Dam during the spawning season (Mason
Shouder, personal communication).
The lake sturgeon population of Mullett Lake utilizes the Pigeon
River as a spawning ground. Sturgeon from Burt Lake may spawn in the
surgeon River (Mason Shouder, personal communication). The extent
of the spawning runs and suitable spawning habitat for these populations
is unknown.
The Menominee River
The Menominee River population is landlocked, being confined
to the portion of the river between the White Rapids Dam upstream and
the Grand Rapids Dam downstream, a distance of 26 river miles (Priegel
1973). It is the object of a hook-and-line fishery each year during the
months of September and October. Burdick (1968) has described the
nature of this fishery. Management of the Menominee River population
is carried out jointly by Wisconsin and Michigan. Priegel (1973) has
Conducted detailed investigations of the Menominee Sturgeon population
and its fishery.
Lake St. Clair and the St. Clair River
Very little is known about the lake sturgeon population of Lake
St. Clair, except that a substantial (and largely illegal) fishery has
27
taken place in the North Channel of the St. Clair River for many
years.
Each year during the month of June, lake sturgeon migrate up
the North Channel to a series of deep holes along the mainland shore,
across from Dickinson Island. They advertise their presence by rolling
on the surface and jumping, thus alerting local anglers. It is believed
that the sturgeon spawn in these deep holes, as they concentrate in very
localized areas. Local residents report that the bottom in these areas
is composed of large cinders, dumped by steamships many years ago.
The current is very strong in the North Channel, and if the substrate is
as reported, then conditions would be ideal for spawning sturgeon.
Further proof of spawning activity is the occurrence of ripe female
Sturgeon in the anglers' harvest. I was shown a color photograph, taken
by a local resident, of several gallons of ripe Sturgeon roe removed from
a fish caught by the person's son in 1978.
Very small sturgeon, estimated to be only 1 or 2 years old, have
been taken by Michigan Department of Natural Resources research vessels
in Anchor Bay (Robert Haas, personal communication). Also, larger lake
Sturgeon of varying sizes and ages have occasionally been collected all
Over Lake St. Clair over the past 12 years. Thus the Sturgeon, though
Still rare, are apparently reproducing.
Some local residents catch spawning lake Sturgeon in much the
Same manner as is employed in the Menominee River fishery. Very
heavy tackle is utilized, and bottom fishing with nightcrawlers is the
28
preferred method. The taking of sturgeon in this manner is legal, as
there is currently no closed season with respect to sturgeon fishing in
the Great Lakes and connecting waters. However, most of the sturgeon
taken in this fishery are snagged, not caught on live bait. Violations
are the rule rather than the exception in this fishery. The most
common terminal fishing gear consists of a heavy sinker (1 to 1 1/4 pounds)
and two to four very large treble hooks. A single point of each treble hook
is baited with a plastic worm, thus circumventing the fishing regulation
which states that all lines must be baited. This type of gear bears great
resemblance to the equipment used to snag paddlefish in the large rivers
of the western United States.
The violator thus equipped allows the current to carry his sinker
and hooks into the deep hole where the sturgeon are concentrated. The
Slack line is taken up and the gear is allowed to remain on the bottom
until a sturgeon swims into it, thus jerking the line. The violator then
heaves back on his heavy rod, hoping to drive the points of the treble hooks
into the fish's body. Though apparently crude, this method accounts for the
majority of the sturgeon taken in this fishery.
Set-lining, though illegal, is also a popular method among the
local residents for taking sturgeon, and heavy set-lines can be seen tied
to many docks in the vicinity of the "sturgeon holes."
The harvest of lake sturgeon from the North Channel, by both
legal and illegal methods, is substantial. One resident, who has kept
meticulous records concerning the number of Sturgeon he has caught or
29
Seen caught from the main fishing area since 1963, told me that in 1969
he saw more than 100 sturgeon taken in 2 days, all of them Snagged.
Even if this figure is greatly exaggerated, it still indicates a very large
number of spawning Sturgeon is being taken. Residents report that the
catch of Sturgeon during the June fishery was much larger in past years
than it is now, and that many more people are now fishing for sturgeon
than formerly did.
Apprehension of violators operating in this fishery is exceedingly
difficult. Most of the fishing goes on at night, making observation of
fishermen difficult. In the case of the snaggers, a fish must be caught
and in possession or no violation can be charged. At times, no fish may
be caught for several days. This makes direct observation of the fishery
by conservation officers a relatively fruitless endeavor.
From June 15 through June 24, 1979, I conducted a creel census
on the North Channel of the St. Clair River. Several lake sturgeon were
observed jumping and rolling on the surface, but no legal-size sturgeon
were caught by any of the anglers that were interviewed. One sublegal
surgeon was reported caught and released. Anglers and local residents
Stated that several large sturgeon were taken on the weekend prior to the
beginning of the creel census. Not enough data were collected for an
estimate of fishing pressure to be made.
Lake St. Clair and the St. Clair River apparently still support
a significant population of lake sturgeon. However, more stringent
*egulations governing the taking of Sturgeon during the spawning season
are necessary if the population is to be given an opportunity to increase.
30
Other Michigan sturgeon populations
In addition to the populations discussed above, lake Sturgeon
are still present in all of the Great Lakes, though not in numbers
approaching their abundance of a century ago. Sturgeon are reported
Only occasionally by commercial fishermen in pursuit of other species
and by state research vessels. Commercial fishing for lake sturgeon
has been illegal since 1970. Organ et al. (unpublished) report that, based
on information gathered from commercial fishermen, lake sturgeon have
spawned or are spawning in parts of Lake Erie, the Detroit River, the
St. Clair River, Lake Huron, and Lake Michigan. Maps showing the
locations of these spawning areas are included in that publication.
Lake sturgeon are occasionally reported in most of the larger
streams flowing directly into the Great Lakes. The fish are most often
seen during the months of May and June, when they come in from the
lakes to spawn. Reports of Sturgeon are almost exclusively from the
lower reaches of the rivers, below the first dam. In two cases, reports
of sturgeon have come from lakes at the end of river systems. Both of
these lakes communicate directly with Lake Michigan, so these fish do
not belong to landlocked populations.
Rivers in which lake sturgeon have been reported at least once
during the last 10 years are listed in Table 3.
Lake sturgeon are occasionally encountered in Pere Marquette
Lake, Mason County, but have not been reported from the Pere Marquette
River.
31
Table 3. --Rivers in which lake sturgeon have been reported during the
last 10 years.
River County Comments
Upper Peninsula
Mille coquins Mackinac below Millecoquins Lake
Sturgeon Houghton, Baraga below Prickett Dam
Waiska Chippewa
Lower Peninsula
Cheboygan Cheboygan below paper mill dam in Cheboygan
Au Sable Iosco below Foote Dam
Manistee Manistee below Tippy Dam
Muskegon Muskegon below Croton Dam, also Muskegon
Lake
Grand Ottawa, Kent below city of Grand Rapids
St. Joseph Berrien below Berrien Springs Dam
32
Several local populations of lake Sturgeon exist in various lakes
in the Upper Peninsula. Most of these populations are landlocked,
connections with the Great Lakes via river systems having been blocked
by impoundments. Lakes harboring such populations include: Otter Lake,
Houghton County; Manistique Lake, Mackinac and Luce counties; Indian
Lake, Schoolcraft County; Brevoort Lake, Mackinac County; and Monacle
Lake, Chippewa County. Not much is known concerning the Sturgeon
populations of any of these lakes. The only direct attempt to assess one
of these populations was made in 1979.
In late May 1979, I assisted the U. S. Forest Service in an
assessment of the magnitude of a lake Sturgeon spawning run in the upper
Indian River in Schoolcraft County, near Manistique. The sturgeon
population of Indian Lake Spawns in the upper reaches of the Indian River.
In 5 days of electrofishing, six lake Sturgeon were captured and length,
weight, and girth measurements were taken. Pectoral fin bones Were
removed from all Sturgeon for the purpose of age determination. Twelve
other lake sturgeon were observed but not captured by Forest Service
personnel. Approximately 20 lake Sturgeon were observed by a local
resident on the night of May 15, about 7 miles upstream from the site
of the electrofishing (Charles Basset, personal communication). (The
electrofishing boat could only travel about 1 mile upstream from the
In Outh of the river, due to the width of the stream and the frequency of
obstructions.) Some illegal harvest is taken from the Indian Lake population
during the spawning run, but the severity of this problem is not known.
33
Evidently, these small inland populations do not support
significant fisheries. Lake sturgeon are occasionally speared through
the ice during the winter spearing season on Indian Lake, but the number
of fish harvested is not known. More research is necessary to determine
the size of these populations and rates of exploitation.
Outside of the three major fisheries discussed above, the angler
harvest of lake sturgeon from the other sturgeon populations of Michigan,
including the Great Lakes, is very small. A few sturgeon are taken on
hook and line each year in the Great Lakes and at the mouths of rivers
by anglers fishing for other species. The number of legal sturgeon
taken under these conditions probably amounts to less than ten fish
annually.
ESTIMATES OF FISHING PRESSURE AND
CATCH PER UNIT EFFORT
Estimates of fishing pressure and catch per unit effort were
only possible for the Black Lake spear fishery and the hook-and-line
fishery of the Menominee River, as these were the only fisheries for
which adequate creel census information was available.
Black Lake
A creel census of the Sturgeon fishery in Black Lake was
conducted by Department of Natural Resources personnel during the
1975 and 1976 spearing seasons. Sturgeon anglers returning from
fishing were interviewed at random and the numbers of hours spent
fishing and fish speared were recorded. Counts of occupied shanties
on the sturgeon spearing grounds were made, but it was later found
that the shanty counts for both years were not made in a random manner,
so the shanty count data were not used in the development of the effort
estimates. Since each Sturgeon Speared in Black Lake must be
validated by a DNR fishery biologist, the total catch for the entire
Season was known, thus allowing estimates of fishing pressure and
catch per unit effort to be made using only the interview data and the
total catch.
It was assumed that the interviews of spearers comprised a
random sample of the population of all Sturgeon Spearers. Catch per
34
35
hour was calculated for each day of the season on which interviews were
conducted. The mean catch per hour £e for the entire season was then
calculated as follows:
where 2 i is the catch per hour calculated for day i , and n is the
number of days sampled.
e 2^
The estimated variance of Lic was determined using the
following formula:
2 (28.)”
2^. > 3’ “ - ––
v(ſic) = + Il
n(n-1)
Fishing effort was measured in Shanty hours. The estimated number
ASN
of shanty hours H was then calculated from the known catch and the
estimated mean catch per hour.
known Ca toh
AN
P'c
/N
H =
The estimated variance of the fishing pressure is
T A /\
V(H) = H —-
because, if B and C are any two random variables, and A = B/C,
then according to Cochran (1963)
36
ºs-smams
2|V(B) + V(C)
- 2 COV (B, C)
B2 C2
V(A) = A
In this case, the known catch is a constant. Since the variance of a
constant is Zero the B term is omitted from the equation. It was
assumed that the covariance of the known catch and £e Wa S Ze I’O.
Confidence intervals (level of significance = 0.05) were
constructed for estimates of total shanty hours and catch per hour.
Estimates of effort and catch per unit effort, confidence
intervals, and the known catch for the 1975 and 1976 spearing seasons
are listed in Table 4.
A shanty hour is a unit indicating that a spearing shanty is
occupied by an angler or anglers for a period of 1 hour. One shanty
hour is essentially equivalent to One angler hour, since there is no
relationship between the number of anglers in a single shanty and
spearing success. Catch per hour estimates are made more meaningful
by converting to hours per fish which is the reciprocal of catch per hour.
In 1975, 70.4 shanty hours of effort were expended for every
surgeon harvested. In 1976, each sturgeon speared represented 116.8
shanty hours of effort. The mean number of hours expended per fish in
1975 and 1976 is 93.6 hours per fish.
There are statistically significant differences between 1975 and
1976 for both fishing effort and catch per hour. These differences were
shown by the techniques, of hypothesis testing, using a level of significance
37
Table 4. --Estimates of effort and catch per unit effort for the spear
fishery of Black Lake, 1975-1976.
Catch per
Effort 95% unit effort 95% Total
Year (shanty confidence (i. i Ol." confidence known
hours) limits 1Sh per limits catch
- Shanty hour)
1975 2, 332 1895, 2769 0.0 142 0.01.15, 0.0168 33
1976 3,972 3503, 4441 0.0086 0.0075, 0.0096 34
38
of 0.05. It is interesting that the total catch in 1975 and 1976 remained
essentially the same. Catch per hour decreased in 1976, but this
decrease was evidently balanced by an increase in the number of shanty
hours. The reason for the differences in fishing effort and catch per
unit effort between 1975 and 1976 is not known.
Vondett (1957) estimated the fishing pressure on Black Lake
during the 1956 spearing season to be 5,076 angler hours. (Vondett's
angler hour is equivalent to the Shanty hour used in this investigation,
since Vondett sent questionnaires to the owners of shanties at the end
of the spearing season.) The estimated total catch in 1956 was 55
Sturgeon. The greater number of fish taken in 1956 (55 as compared
with 33 in 1975) can be attributed to the 2-month-long fishing season
in 1956 (January and February), and to the 42-inch minimum size limit
then in effect, rather than to a decline in the sturgeon population.
Vondett also estimated that 84 hours of effort were expended for every
Sturgeon speared. This agrees fairly well with the mean estimated
effort per sturgeon for 1975 and 1976 (93.6 hours per fish).
Menominee River
Priegel (1973) estimated the fishing pressure and total catch
for the Menominee River hook-and-line fishery in 1969 to be 14, 300
angler hours and 59 lake sturgeon, respectively. In 1970, the estimated
fishing pressure was 11,400 angler hours and the estimated total catch
Was 48 lake sturgeon.
39
The amount of effort expended for each Sturgeon harvested was
calculated using Priegel's estimates of fishing pressure and total catch.
In 1969, 242. 4 angler hours were expended for each legal Sturgeon,
while in 1970, the effort was 237.5 hours per fish. These estimates
of the number of hours fished per sturgeon harvested are much higher
than similar estimates for the Black Lake spear fishery. The difference
in the amount of effort necessary can partially be accounted for by the
different types of gear employed. Also, Priegel did not mention in his
report whether or not sturgeon fishermen were distinguished from
anglers fishing for other species. If all anglers were considered
together, the estimated number of angler hours spent in pursuit of
sturgeon would be inflated, since the time spent by anglers not fishing
for sturgeon would also be included.
POPULATION AND EXPLOITATION ESTIMATES
Black Lake
A mark-and-recapture study was conducted by Shouder (1975
and personal communication) in which he captured and marked lake
sturgeon in Black Lake during the month of June from 1970 through
1978. Each fish handled was marked, total length was recorded, and
a pectoral fin-bone was taken for aging. I obtained Shouder's raw data
for the purpose of making population estimates and thereby estimating
exploitation rates, since the total catch for each year by sport fishermen
was known. Because of the nature of the mark-and-recapture data
available, it was necessary to make several modifications so that the
data could be analyzed by a standard estimation method.
The Chapman modification of the Petersen estimator was used
to estimate the population size for a even year. The formula is as
follows:
* = CM + 1) (C + 1)
(R, + 1)
/\ .
where N is the estimated size of the population, M is the number of
marked fish at large in the population, C is the size of the second, or
recapture sample, and R is the number of marked fish recaptured in
40
41
the second Sample. This estimator is slightly biased, but the bias
becomes negligible when MC is greater than 4N (Robson and Regier
1964).
Because of the small number of fish marked in any given year
and the small number of recaptures, it was necessary to combine the
groups of fish marked over a period of several years in order to obtain
realistic population estimates.
Since annual mortalities occurring over several years would
tend to reduce the number of marked fish at large in the population,
a correction was made in the size of the marked population using the
following procedure. All of the fish marked in a given year i were
considered as a single cohort mi . For each year that the cohort was
at large in the population, the percent annual mortality was subtracted
from it. It was assumed that both marked and unmarked fish were
subject to the same annual mortality. The annual mortality rate was
obtained from the instantaneous total mortality rate which was calculated
by least squares regression of the descending leg of a catch curve, a.S
will be described later. By this method, annual mortality was found to
be 0.097 or 9.7%.
As an example, suppose that in 1970, 16 sturgeon were marked,
and that we wish to know how many of these fish should still be available
for a population estimate in 1974. Using the formula
m. -- 1 = m = - a m:
l l l
42
where a is the annual mortality rate, the results would be as follows:
1971: 16 – 9. 7% = 14.45
13.05
1972: 14.45 – 9.7%
-:
1973: 13.05 – 9. 7% = 11.78
The result for the year under consideration was then rounded off to the
nearest whole number.
When a Petersen estimator is used, the population estimate
obtained applies to the time when the marked fish were released. Since
in this case the marked fish were released over a period of several
years, the population estimate was arbitrarily assigned to the year
immediately preceding the year of the recapture sample.
When the fish were marked, both sublegal fish and fish of legal
size were tagged. During the winter Spearing season, only Sturgeon 50
inches and larger can be legally taken. I wished to use the catch records
from the spearing season in conjunction with the netting data so as to
increase the size of the second sample, C , in the Petersen estimator.
Therefore, I decided to consider only fish 50 inches and larger in
evaluating C.
In order to allow for the sublegal fish, and to increase the number
of legal-size marked fish available at the time of recapture, fish which
would be 50 inches long by the year of recapture were included in the
marked population M. Predictions of growth were obtained from the
von Bertalanffy growth curve, which will be discussed later. Since the
43
marked sublegal fish ranged in size from 38 inches to 50 inches, the
mean predicted annual growth increment was calculated for fish in this
size range from the predicted lengths at age of the von Bertalanffy
model. The mean annual growth increment for lake Sturgeon from
38 inches to 50 inches in length is 1.4 inches.
I used the growth increment calculated from the von Bertalanffy
model in preference to the increments derived directly from mean
length. at age, because in the empirical data the mean length at age
x + 1 is often less than the mean length at age x due to the small
sample size of fish in each age class.
For each sublegal fish in a cohort of marked fish, the mean
annual growth increment was added to its length successively until a
length of 50 inches was reached. For example, a 42-inch Sturgeon
marked in 1970 would not be considered available for recapture until
1976 when it reached 50 inches in length.
It should be noted that since the population estimate has been
assigned to the year previous to that of the recapture sample, the
estimate resulting from the use of data treated in the manner described
above will be of the number of sturgeon 48.6 inches and larger. This is
because the last mean growth increment will not yet have been added.
Since these fish are of nearly legal size, the estimated size of the
population of legal fish would be very close to the estimated population
of fish 48.6 inches and larger.
44
By integrating the aforementioned procedures, and applying
them to each cohort of marked fish, the size of M at the time when
the second sample (C) was made was determined. For example,
consider the conor Of fish marked in 1970. I wanted to know how many
of these fish were available when the recapture sample (C) was taken
in 1974. The number of fish marked in 1970 was 17. Three of these
fish were not of legal size, but by adding the mean annual growth
increment to each fish's length four times, I found that two of them
would be of legal size by 1974. Thus I had 16 fish which either were
of legal size or would be legal by 1974. I then subtracted successive
annual mortalities for 1971-1973 and obtained a final figure of 12
marked fish still available for recapture in 1974.
This procedure was carried out for each group of fish marked
in successive years. The numbers of marked fish from each group which
would be available at the time of the recapture sample were summed and
the number of marked fish of legal size (M) was thereby obtained. The
second, or recapture sample (C) was composed of the combined netting
and spearing data for the following year. since some Of the netted fish
were not of legal size, these were not included in the second sample. In
simple form, fish in recapture sample equaled fish speared plus fish
netted minus sublegal fish netted. Tagged fish which were speared and
netted were combined to give the number of recaptures in the second
sample (R). A 95% confidence interval for each estimate was calculated
45
using a table, based on the Poisson frequency distribution and found
in Ricker (1975).
Exploitation rates for sport fishing were calculated by dividing
the known catch for a given year by the population estimate for the
previous year and extreme values of exploitation were determined by
calculating exploitation rates using the confidence limits of the
population estimates. The estimates of population size and exploitation
rates for the years 1973-1976 are listed in Table 5.
Population estimates for 1976 were not possible because no
marked fish were recaptured in 1977. Marked fish were taken in 1978
and 1979, but data for the netting surveys of 1978 were unavailable and
no netting was done in 1979. Therefore, population and exploitation
estimates for these later years were not feasible.
I feel that the population estimate for 1975 and the resulting
exploitation estimate for 1976 are the most representative of the true
conditions, as the 1975 estimate is based on the largest number of
recaptured marked fish (4) and therefore has a smaller bias than the
Other two estimates.
Menominee River
Priegel (1973) estimated the population of legal size (42 inches
and larger) lake sturgeon in the Menominee River to be 243 + 7.1% in
1969 and 185 + 30% in 1970. He estimated the exploitation rates to be
13% and 17% in 1969 and 1970, respectively.
46
Table 5. --Estimates of population size and exploitation rates for lake
sturgeon, Black Lake, 1973-1976.
Year M1 M2 R. º º wº ar
limits % Limits
1973 97 33 1 1, 666 505, 30.29
1974 117 41 - 1 2, 478 751, 4505 0.8 0. 4, 2.6
1975 122 64 4 1, 599 714, 3998 1. 3 0. 7, 4.4
1976 -
2. 1 0.8, 4.8
47
It should be noted that the size limit for surgeon in the
Menominee River has been raised to 50 inches since Priegel conducted
his investigations, so presumably the present exploitation rates are
not the same as they were in 1970.
STOCK ASSESSMENT
An evaluation of the adequacy of the current spearing regulations
for lake sturgeon in Michigan's inland lakes was carried out using the
equilibrium yield equation of Ricker (1958). This is a dynamic pool model
of the general form
* = FN(x) w (z)
dx
where Y is yield, x is age, F is the instantaneous fishing mortality
rate, N (x) is the number of individuals of age x , and W (x) is the
weight of an individual of age x. A derivation of the model is given in
Ricker (1975). With the Ricker model yield can be calculated for a
given weight or number of recruits at various levels of fishing mortality
and ages at entry into the fishery, so that the combination of regulations
which will give a maximum yield from the fishery can be ascertained.
Although this analysis deals primarily with spearing regulations, the
results concerning maximum rates of exploitation are equally applicable
to hook-and-line fisheries, such as those of the Menominee and St. Clair
rivers.
48
49
Growth in Length and Weight
Age-length relationship
Raw length and age data for fish taken in Black and Mullett
lakes and the Menominee River were procured from files and reports
of the Michigan Department of Natural Resources. Due to the methods
of collection employed in the different locations, no single data set
considered alone adequately represented the growth of the lake sturgeon
through its entire lifetime. In the Menominee River, sturgeon were
collected by electrofishing (Priegel 1973), and the sample was
predominantly composed of fish less than 20 years old. By C Ontra St,
the fish captured in Black and Mullett lakes We Jºe taken either by
spearing during the February fishing season or in large mesh gill nets
as described by Shouder (1975). The fish taken by these two methods
were predominantly older than 20 years.
Because of the very small amount of data from Mullett Lake,
information from this location was combined with that from Black Lake.
The small sample size precluded any attempt to show a statistically
significant difference in growth rates between the two lakes, thus Black
and Mullet lakes were considered together and identified simply as the
inland lakes.
In order to evaluate the growth of the lake sturgeon over its
entire theoretical life span, it was necessary to combine the age-length
data from the inland lakes and Menominee River populations. The
50
length-age relationships of the two data sets are so similar that I judged
the growth rates of the inland lake and Menominee River populations were
not significantly different (Figure 3). -
The growth equation of von Bertalanffy (1988) as developed by
Beverton and Holt (1957) was fitted to the length-age data by the method
of least squares using FORTRAN program. BGC3 from Abramson (1971).
The equation is of the form
24. = L-2 [1 - e-k(x-xo),
where 2& is length at age x', L 2 is the theoretical asymptotic
length, k is a growth coefficient, and x,\ is the theoretical time
O
when length is zero. The parameters of the von Bertalanffy model
for Michigan lake Sturgeon are
Loo = 69. 6411 inches, k = 0.0558, xo = -0.8815
Graphic analysis of residuals showed no significant biases in the model.
The predicted von Bertalanffy growth curve for Michigan lake sturgeon
is given in Figure 3. Lengths predicted by the model and observed mean
lengths for ages 1-65 are given in Table 6.
It should be noted that surgeon of length greater than L 22
are not uncommon. These large sturgeon are generally taken by spear
fishermen during the February season. They tend to be very old, and
aging these fish accurately is nearly impossible. Since very large
51

8OF
D D []
. - D
70––––––––––––––––––5–
O O RH · L [ba [T] [...]
O [...]
. O ->tº D-"
6OH- . º *ºff" [I]
t; O sº +H O []
.* O
~50H- © [2(TI)
-C O [...]
O 7ſ D
S .7
S 4O * O
O) O
C
QD
~!
3OH
• Menominee River
D Inland Lakes
2OH- T Fitted von Bertalanffy
• Curve
1OH-
| | | | | |
1O 2O 3O 4O 5O 6O
Age -
Figure 3. --Combined empirical length-age relationship for lake
Sturgeon from the Menominee River and the inland lakes, with fitted
von Bertalanffy curve.
52
Table 6. --Observed and predicted values of length (inches) at each age for
Michigan lake sturgeon. -
Age - Length —
(years) - observed - - Predicted
(empirical mean) (von Bertalanffy)
l 6.0 6.. 9
2 11.0 10. 3
3 12.5 13. 6
4 16. 1 16. 6
5 20. 2 19. 5
6 22. 1 22.2
7 24. 7 24.8
8 27. 5 27. 2
9 30. 3 29. 5
10 31. 9 31. 7
11 34.8 33.8
12 37. 0 35.7
13 39. 7 37.6
14 41. 5 39.3
15 44. 6 40. 9
16 42.5
17 46. 1 44. 0
18 46. 1 45.4
19 46.2 46.7
20 48.9 4.7. 9
21 49.0 49. 1
22 50.3 50.2
23 50. 7 51.3
24 50. 9 52.3
25 52.8 53. 2
26 52.9 54. 1
(continued, next page)
- 53
Table 6. --continued.
Age - Observ Length. 5–
(years) served - - Predicted
(empirical mean) (von Bertalanffy)
27 54.8 55. 0
28 54.7 55.8
29 57. 6 56. 5
30 54. 5 57. 2
31 57.7 57. 9
32 - 57. 2 58. 5
33 - 56. 7 59. 1
34 - 59. 5 59. 7
35 - 58. 9 60. 2
36 60. 2 60.8
37 61.3 61.2
38 60.7 61. 7
39 64. 5 62. 1
40 65. 0 62. 5
41 62.6 62. 9
42 63. 9 63.3
43 62.0 63. 6
44 57.8 64. 0
45 66. 0 64. 3
46 65. 5 64. 6
47 69. 9 64.8
48 65.8 65. 1
49 65. 6 65. 3
50 75. 0 65. 6
51 61. 5 65.8
52 66. 0
53 64. 5 - 66. 2
54 - 66.4
(continued, next page)
54
Table 6. --concluded.
Length
gº. ) observed Predicted
(empirical mean) (von Bertalanffy)
55 66. 3 66. 6
56 76. 0 66. 7
57 70. 3 66. 9
58 72. 3 67.0
59 67. 2
60 73. 5 67. 3
61 69. 5 67.4
62 67. 6
63 72. 3 67. 7
64 - 67. 8
65 67. 9
55
sturgeon constitute only a very small portion of the total population,
only fish of age 65 years and younger were considered in this analysis.
Length-weight relationship
Only mean length and mean weight data for each age were
available for the Menominee River population, so mean length and mean
weight data from the inland lake stocks were used in conjunction with the
Menominee River data for the purpose of determining a length-weight
model for a typical Michigan lake sturgeon population.
The allometric length-weight relationship was fitted to the mean
length and weight data by the technique of simple linear regression. The
relationship is of the form
W = a LP
where W is weight, L is length, and a and b are parameters.
The length-weight relationship for Michigan lake sturgeon
WaS
2&w - -8.8949 3, 1893 AL.
The coefficient of determination for this model was 0.986. The
standard deviation of the regression was 0. 169, which is considered
to be large. The discrepancies between the predicted and observed
56
values were quite large, amounting to as much as 15 pounds in SOIſle
of the largest fish. However, in fish Of Over 100 pounds (which constitute
only a small portion of the total catch) such an error was not of great
consequence.
It is reasonable to suppose that the variation in the length-weight
model could be reduced appreciably by considering male and female fish
separately. However, as determination of sex generally requires
dissection, it is not a feasible procedure when fish are to be released
alive. For this reason very little raw data where sex wº recorded were
available, and such data as could be procured came exclusively from fish
of 50 inches and larger taken by sport fishermen. These data would be
unrepresentative of the full life span of the fish.
Mean weights at age were calculated from lengths at age
(predicted by the von Bertalanffy equation) using the length-weight
relationship described above. These weights were incorporated into
the Ricker equilibrium yield model.
Mortality
Black Lake
Due to the small number of sturgeon taken in any one year,
no single data set adequately represented the relative abundances of
several consecutive age groups. In order to construct a catch curve,
it was necessary to combine age and frequency data collected over a
period of several years.
57
Data concerning age frequencies of lake sturgeon captured in
gill nets were utilized in the construction of the catch curve. The
number of fish of known age netted from 1970 through 1976 was larger
than the number of fish speared from 1974 through 1977, for which age
was known, and the netting sample exhibited a more uniform representation
of frequencies over several consecutive year classes than did the spearing
Sample.
Ages of fish taken in gill nets ranged from 9 to 55 years, while
ages of speared fish ranged from 20 to 63 years. However, only 5 fish
older than 55 years were speared from 1974 through 1977 out of 107 aged
fish. Since there is a significant amount of overlap of the age distributions
of netted and Speared Sturgeon, it was felt that the netting data would
provide an adequate estimate of the mortality rate of recruited fish.
The age-frequency data for sturgeon netted from 1970 through
1976 were transformed by subtracting the age of each individual from
the year in which the individual was captured, thereby obtaining the year
class of each fish. Each year class was then further transformed by
assigning to it the age which fish of that year class would attain in the
year 1976. This latter transformation was done arbitrarily, its purpose
being to give the resulting catch curve its traditional configuration,
with the right leg descending. Age frequencies resulting from this
manipulation are listed in Table 7. The top of the dome of the catch
curve was chosen by inspection of a graph of the natural logarithm of
frequency against assigned age. Fish of less than 25 years old (assigned
58
Table 7. --Year classes, assigned ages, and frequencies of
lake sturgeon netted in Black Lake, 1970-1976.
: * Frequency
1966 10 1
1959 17 - 1
less - 20 3
1955 21 6
1954 22 7
1953 as 7
1952 24 8 .
1951 25 . 14
1950 26 15
1949 27 10
1948 28 17
1947 - 29 10
1946 - 30 - 7
1945 31 13
1944 32 7
1943 33 - 6
1942 - 34 5
1941 . 35 11
1940 36 10
(continued, next page)
59
Table 7. --concluded.
Year Assigned Frequency
class age -
1939 37 8
1938 38 - 7
1937 39 5
1936 40 - 7
1935 41 1
1934 42 - 2
1933 43 2
1932 44 2
1931 45 3
1930 46 3
1929 47 2
1928 48 º 1
Total 201
60
age) were not considered to have been randomly sampled. Data
concerning these fish were deleted, and a line was fitted to the
remaining data by the method of least squares. The slope of this line
is a point estimator of the instantaneous total mortality rate, Z, for
the range of ages encompassed by the data.
The following assumptions must be made in order to consider
the descending leg of the catch curve described above to be an age-
specific survival curve. -
1. Survival is constant over the range of age groups in question.
2. There has been no change in the survival rate with time.
3. The samples taken from the age groups involved are random.
4. The age groups under consideration were equal in numbers
at the time each age group was recruited into the fishery.
The instantaneous total mortality rate for Black Lake Sturgeon
was 0. 102. The coefficient of determination for the regression model
was 0.727 and the standard deviation of the regression 0. 452, which is
considered to be large.
The survival rate S was calculated by the formula
and was found to be 0.903. Subtracting the survival rate from one (1)
gives, a , the annual mortality rate. The annual mortality rate for
Black Lake sturgeon was 0.097, which was utilized in the construction
of population estimates discussed earlier.
61
The large amount of variation in the regression model can be
accounted for in two possible ways. First, it must be remembered that
the total number of fish of known age netted from 1970 through 1976 was
only 205. Thus, the sample size for each age group was quite small
when the number of age groups sampled was taken into consideration.
Secondly, some of the variation in year class strength was no doubt due
to fluctuations in recruitment from year to year.
Instantaneous total mortality is defined as the sum of the
instantaneous natural and fishing mortality rates
Z = F + M.
Fishing mortality F is generally calculated, and the remaining
mortality is assigned to natural or non-fishing causes (M).
The instantaneous fishing mortality rate was calculated using
the following formula, taken from Everhart, Eipper, and Youngs (1975):
in which F is the instantaneous fishing mortality rate, E is the rate
of exploitation, Z is the instantaneous rate of total mortality, and
S the survival rate.
For the purpose of the yield analysis, an exploitation rate of
0.025 (2.5%) was assumed. Using this exploitation rate, together with
the estimates of Z and S calculated from the catch curve, the
instantaneous fishing mortality rate was calculated to be 0.026.
62
Instantaneous fishing mortality rates were calculated for the
years 1974 through 1976, based on the rates of exploitation for those
years, which were calculated as described earlier. The results are
as follows:
Year F
1974 0.008
1975 0.014
1976 0.022
Menominee River
The Menominee River population was sampled by electrofishing,
and although this fishing method was not obviously selective for fish of
any particular size range, most of the sample consisted of Sturgeon less
than 20 years old. Priegel (1973) attributed the predominance of smaller
fish to a lack of larger fish in the population, rather than gear selectivity.
A line was fitted to a plot of the natural logarithm of frequency
versus age and the instantaneous total mortality rate was determined in
the same manner as for the Black Lake population.
The instantaneous total mortality rate for Menominee River
sturgeon was 0.098. The coefficient of determination for the model was
0.757; the standard deviation of the regression 0.714. The large amount
of variation can again be ascribed to the small sample sizes for individual
age groups and annual fluctuations in reproduction. The corresponding
survival and annual mortality rates were 0.907 and 0.093 respectively.
63
Instantaneous rates of fishing mortality were determined in
the same manner as was used for the Black Lake population. Exploitation
estimates taken from Priegel (1973) were used in conjunction with the -
above estimates of instantaneous total mortality and survival, and the
instantaneous fishing mortality rates for 1969 and 1970 were found to be
0.137 and 0.179 respectively.
Priegel and Wirth (1975) estimated the instantaneous total
mortality rates in the Lake Winnebago population to be 0.054 for sturgeon
from 16 to 36 years of age, and 0. 134 for older fish. Since the mortality
estimates were made by using regression techniques on two segments of
the descending leg of a single catch curve, instead of fitting a single line
to the entire descending leg (as has been done for the Michigan populations
here), the Winnebago estimates are not directly comparable with the
mortality estimates for Michigan lake sturgeon. It should also be noted
that Priegel and Wirth worked with a much larger sample of fish.
Incorporation into the yield equation
- Since Ricker's yield model allows the use of different mortality
rates for different age groups in the calculation of me yield equation,
it was thought prudent to partition natural mortality according to the
quantity of information available for different segments of the age
distribution. The instantaneous total mortality rate for Menominee
River sturgeon was developed for a sample of fish which was composed
mainly of individuals less than 20 years old. Therefore, the instantaneous
64
total mortality rate for Menominee River fish was used as the natural
mortality rate in the yield model for sturgeon up to 20 years of age.
Under the present fishing regulations, fish o: less than 20 years old
suffer virtually no fishing mortality.
Natural mortality for lake sturgeon of ages greater than 20 years
WalS calculated using the instantaneous total mortality rate for the Black
Lake population. The arbitrary fishing mortality rate of 0.026, mentioned
earlier (page 61), was subtracted from the instantaneous total mortality
rate (0. 102) to give an instantaneous natural mortality rate of 0.076.
The instantaneous fishing mortality rate of 0.026 (calculated
from a hypothetical exploitation rate of 0.025) was utilized in the yield
model Multipliers used in conjunction with this fishing rate, resulting
multiples of the Original fishing rate, and rates of exploitation
corresponding to each multiple are listed in Table 8.
Yield per Recruitment
The Ricker equilibrium yield model operates under the
assumptions that recruitment is constant and that fluctuations in population
density are not of sufficient magnitude to facilitate changes in the growth
or mortality rates of the population under scrutiny (Ricker 1975).
For the purpose of this analysis, recruitment consisted of 1,000
age-1 sturgeon. Under the current fishing regulations, lake surgeon
enter the fishery at an age of 22 years, by which time they are 50 inches
long. For a population in a steady state, with an exploitation rate of 2.5%,
65
Table 8. --Multipliers of the instantaneous fishing rate used in
the Ricker yield model and corresponding rates of exploitation.
Multiplier F º *
0. 5 - 0.018 0.012
1.0 0.026 0.025
2.0 0.052 0.049
3.0 0.078 0.074
4. 0 0. 104 * 0.099
5. 0 0.130 - 0. 124
6. 0 0. 156 - 0. 148
7.0 0. 182 0.173
8. O 0. 208 0. 198
9. 0 0.234 0.223
10. 0 0. 260 - 0.247
66
the yield was calculated to be 1, 522 pounds for every 1,000 recruits.
This calculation was repeated for ages at entry ranging from 1 to 65
years, and 11 multiples of the original instantaneous fishing rate Of
0.026 such that the fishing rates evaluated corresponded to exploitation
rates ranging from 1. 25 to 25%. All calculations were performed using
the computer program of Paulik and Bayliff (1967). Isopleths were fitted
to the resulting yield matrix (Figure 4). The x indicates the point at
which the Black Lake spear hºmery was Operating in 1976, with an age
at entry into the fishery of 22 years and an instantaneous fishing rate of
0.022, corresponding to an exploitation rate of 2.1%. The circle and
square represent the locations of the Menominee River hook-and-line
fishery in 1969 and 1970, respectively. Here, age at entry was 16 years,
as a 42-inch minimum size limit was then in effect.
The maximum yield attainable for any given fishing rate occurs
at the point where a vertical line originating at the fishing rate of interest
is tangent to the left edge of a contour. The loci of all such tangents form
the eumetric fishing line of Beverton and Holt (1957). A segment of the
eumetric fishing line, extending over the fishing rates under consideration
is included in Figure 4 as line AA'. For each fishing rate, the age at entry
which will provide the maximum yield can be found by drawing a vertical
line from the fishing rate to line AA', then drawing a horizontal line from
AA' to the vertical axis. As an example, for a fishing rate of 0.026 (2.5%
exploitation rate), the maximum yield is 2, 157 pounds for every 1,000
recruits. This maximum occurs when age at entry into the fishery is
8 years.
67
| xe - Age at Recruitment
60 F - Instantaneous Fishing Rate
- 500 -
- 1000 "
_ 1500 "
2000 –
— 2500 "
, 3000 -
A
– 3000 –
= 2500 -
- 2000 *
1 1–lººr
.O52 .104 .156 .2O8
F
Figure 4. --Yield in pounds per thousand age-1 recruits as a
function of age at entry into the fishery, xc , and the instantaneous
fishing mortality rate, F.
–
–
.26O

68
As the rate of fishing F increases, the age at entry
corresponding to the maximum yield ×e * also increases, but the
amount of increase in x per unit increase in F is very small
C Iſla X
and the increment of increase becomes miniscule at high levels of F.
For example, a doubling of the original rate of fishing causes an increase
Of *c max of only 2 years. Multiplying the original fishing rate by 10 -
causes <e max to increase by only 7 years. Thus, the eumetric fishing
line approaches an asymptote corresponding to a very low age at entry
into the fishery.
Since natural mortality rates are difficult to determine accurately
in exploited stocks, it seems appropriate to evaluate yield per recruitment
at various rates of natural mortality. The relationship between yield per
recruitment and instantaneous fishing mortality for four possible rates of
natural mortality with age at entry into the fishery held constant at 22 years
is shown in Figure 5. It is evident that, due to the slow growth rate of the
lake sturgeon, small changes in the natural mortality rate cause large
changes in the yield per recruitment. For example, the fishery in Black
Lake is currently believed to be operating with a natural mortality rate of
0.076. If I have underestimated the true natural mortality rate, then
there is a possibility that the stock is being overexploited. If the true
natural mortality rate is as high as 0.20 (not a large figure when
compared with natural mortality rates of most freshwater species)
then yield per recruitment is very low at all practical fishing
rate S.
10,000-
8,
O
O
O
Mºe
6,OOOH
4,000H
M= O.IO_
2,000H
M= O.15_
T. M= O.2O
mº- I | _l I —l
.052 104_, 156 . .208 . .260
Instantaneous Fishing Mortality
Figure 5. --Yield per recruitment as a function of the instantaneous
fishing mortality rate for different levels of natural mortality with recruit-
ment at age 1 year and entry into the fishery at age 22 years.


70
There is no reasonable fishing rate which will give a true
maximum yield, as all of the yield curves approach asymptotes (Figure 5).
This is because the weights of individual fish do not increase sy a large
amount during their life in the fishery (Cushing 1968). If the age at entry
into the fishery was 5 years, instead of the current age of 22, there would
be at least a tenfold increase in the weights of individual fish during their
lifetime in the exploitable stock, and the resulting yield curve would have
the conventional domed shape. With age at entry set at 22 years, the
weight of individuals during their lifetime in the fishery increases only
by a factor of about 2.5.
Since the trend in sport fisheries is toward increased fishing
pressure as the number of participants increases, an evaluation of the
effects of increased rates of exploitation on equilibrium yield per
recruitment is in order. If age at entry into the fishery is held constant
at 22 years, increasing the rate of exploitation from 2.5% to 5%
(corresponding to a doubling of the original instantaneous aming rate
of 0.026) changes the equilibrium yield from 1, 522 pounds to 2,293
pounds for every 1, 000 recruits, an increase of 51%. Tripling the
original rate of exploitation produces an 80% increase in yield over the
original value. The effect of doubling the instantaneous fishing rate
upon yield per recruitment for all possible ages at entry into the
fishery is illustrated in Figure 6. -
Inspection of the isopleth diagram (Figure 4) with respect to
the yield from the Black Lake spear fishery operating in 1976 (and still
71
23.
Age at Entry (Years)
Figure 6. --Yield per recruitment as a function of age at
entry into the fishery for two instantaneous rates of fishing
mortality, F.

72
believed to operate at the same level today) leads to the conclusion
that the fishery is underexploited. In order to maximize yield at the
current instantaneous fishing rate (0.022) the age at entry into the
fishery would have to be lowered to about 7 years. This would correspond
to a 25-inch minimum size limit. However, it must be taken into account
that male lake sturgeon do not become sexually mature before an age of
14-16 years and females do not mature until 24-26 years of age (Priegel
and Wirth 1977). Since the relationship between the size of the spawning
stock and the number of recruits produced is unknown, it only seems
prudent to protect the fish until at least some of them have had the
opportunity to spawn Once.
- Assuming that all Sturgeon are sexually mature by an age of
25 years, the total biomass of fish 25 years and older can be regarded
as the biomass of the spawning stock. For the purposes of this analysis,
the total biomass of the spawning Stock will consist of the sum of the
individual biomass values for fish of ages 25 through 65 years. Very
few lake sturgeon live past 65 years, and their contribution to the
biomass of the spawning stock, as predicted by the model, is miniscule.
The yield model predicts the total biomass of the spawning stock
for a population from which no harvest is taken to be 70 , 276 pounds per
thousand age-1 recruits. If an exploitation rate of 2. 5% and an age at
entry of 22 years is imposed upon the stock, the total biomass of the
spawning stock decreases to 48,057 pounds, a 32% decline. Doubling
the rate of exploitation (5%) causes a 51% decrease in spawning stock
73
biomass. If the rate of exploitation rises to 25% (not a high figure for
most other tiºn species the remaining total biomass of the Spawning
stock is only 10% of the pre-harvest value.
If the age at entry into the fishery is lowered to 7 years, and
the exploitation rate is set at 2.1% (the age at entry and exploitation
rate which should theoretically produce maximum yield from the fishery
at its 1976 level of operation, as discussed above) the total remaining
biomas. of the spawning stock is 36,485 pounds, a 48% decrease from
the pre-harvest level. If, at this exploitation rate, age at entry into the
fishery is raised to 22 years (corresponding to the 50-inch minimum size
limit currently in effect) the total remaining biomass of the spawning
stock is 50, 749 pounds, a decrease from the pre-harvest figure of only
28%. -
What is the highest rate of exploitation which a lake sturgeon
population can tolerate without showing a decline in numbers and what
effect will a high rate of fishing have upon the stock 2 Cushing (1975)
has described two types of overfishing; growth overfishing and
recruitment overfishing. If recruitment does not change as fishing
mortality increases, but the increased fishing rate causes yield to
decrease because mortality exceeds growth, growth overfishing is
occurring. This type of overfishing usually occurs in situations where
the individual fish grow significantly during their lives in the fishery.
Species such as plaice and halibut may grow in weight by a factor of
ten or more during their recruited lifetime, and graphs of yield per
74
recruitment against instantaneous fishing mortality for these species
will reveal that the yield curves increase to a maximum at some
intermediate fishing rate and then decrease as the fishing rate continues
to increase. When these characteristics are present in an analysis of
yield per recruitment for a particular species, growth overfishing
becomes a possibility. Examination of a graph of yield per recruitment
as a function of fishing mortality for a slow-growing fish will show that
the yield curve continuously increases toward an asymptote, indicating
that there is no fishing rate which will produce a true maximum yield.
The graph of yield per recruitment as a function of instantaneous fishing
mortality for lake Sturgeon (Figure 5) is of this type.
- Recruitment overfishing occurs when the mortality of the adult
stock due to fishing is sufficient to adversely affect the level of
subsequent recruitment. Recruitment overfishing is difficult to
document because stock-recruitment relationships are hard to establish;
the necessary data seldom exist. However, Priegel and Wirth (1975)
estimated the annual recruitment of legal size Sturgeon into the Lake
Winnebago fishery to be 4.7%, based on the average portion of the catch
of all age groups for the years 1955 through 1967, and suggested that the
annual harvest should not exceed the annual recruitment. In a similar
manner, I calculated recruitment into the fishable stock for the Black
Lake population.
I assumed that the size of the adult stock in Black Lake was
constant. Since there have been no significant changes in the size or
75
age distributions of the catch for the years 1974 through 1979, this
assumption appears reasonable. - If the population of adults is stable,
then recruitment will fluctuate about some mean value. Since lake
sturgeon enter the fishery over a broad range of ages, and annual
growth of lake sturgeon near the minimum size limit is only about
1 inch, I examined the proportion of fish in the annual catch which were
between 50 and 51 inches in length. Fish taken by spearing and netting
were combined where possible, in order to increase the size of the
samples. The percentage of the total catch which was from 50.0 to
50.9 inches in length was calculated for the years 1970 through 1979.
Results are shown in Table 9.
The mean percentage of sturgeon 50.0 to 50.9 inches long in
the total catch, for the years 1970 through 1979, is 4.8% which agrees
very well with Priegel and Wirth's estimate.
The natural mortality rate of adult lake sturgeon is believed
to be very small. It is likely that the only significant source of mortality
other than legal fishing is the illegal harvest of adult sturgeon during the
spawning run (Mason Shouder, personal communication). If this is the
case, then the maximum allowable exploitation rate for Black Lake is
approximately 4.8%. Using the 1975 population estimate of 1,599 legal
size lake sturgeon and the above exploitation rate, the maximum allowable
catch of sturgeon from Black Lake was calculated to be 77 fish. The
average annual harvest of sturgeon from Black Lake during the years
1974 through 1980 was 24 fish, less than half of the calculated maximum,
76
Table 9. --Estimation Of annual recruitment to the fishable stock in
Black Lake. (Sturgeon from 50.0 to 50.9 inches in length were considered
recruits.)
Year Spearing Recruits Netting Recruits Total Total º
catch catch catch recruits ment
1970 No record NO record 17 1 17 1 5. 9
1971 NO record No record 42 2 42 2 4.8
1972 No record No record 30 1 30 1 3. 3
1973 NO record NO record 49 2 49 2 4. 1
1974 13 0 27 1 40 1 2.5
1975 33 2 11 2 44 4 9. 1
1976 34 1 - 31 2 65 3 4. 6
1977 29 0 25 2 54 2 3. 7
1978 24 0 NO record NO record 24 0 0. 0
1979 19 2 No record No record 19 2 10.5
77
so the fishery currently appears to be operating with a considerable
margin of safety.
MANAGEMENT RECOMMENDATIONS
In order to insure the continued survival of Michigan's remaining
lake sturgeon stocks, each individual population should be managed
according to the best information available concerning that population.
Fisheries for other species of fish must be managed on a statewide basis
because of the tremendous number of populations present in the many lakes
and streams of the state. In contrast, there are only a very few populations
of lake sturgeon remaining in Michigan.
The Menominee River
Fishing regulations for the Menominee River population have
traditionally been formulated jointly by the states of Michigan and
Wisconsin. The Wisconsin Department of Natural Resources conducted
a survey of the sturgeon population during the summer of 1978, but the
final report has not yet been published. The report is being written at
the present time and should be published sometime this year (Thomas
Thuemler, Wisconsin DNR, personal communication). In lieu of making
recommendations concerning the management of the fishery based on
information which is 10 years old, it would be preferable to review the
management policies after this new information becomes available.
78
79
Black, Mullett, and Burt lakes
These three lakes have traditionally been managed as a single
stock, and at the present time, there is no reason to alter that strategy.
The fishing regulations currently in effect are, at the present time,
sufficien to protect the Sturgeon populations from overexploitation.
If the maximum exploitation rate which a sturgeon population can tolerate
without showing a decline in numbers is 6% (as postulated earlier), then
the present exploitation rate of 2 to 2 1/2% allows a margin of safety.
Apparently the greatest factor affecting sturgeon harvest in any given
year is water early rather than availability of legal size fish.
(Sturgeon spearing is done in areas where the water depth is about 20
feet. If the water is turbid due to adverse weather conditions, the spearer
cannot detect his quarry at those depths.)
The 50-inch minimum size limit currently in effect appears to
be adequate to protect the sturgeon until they are sexually mature. Male
lake sturgeon become sexually mature at ages ranging from 14 to 16
years, and so are sexually mature before they reach 50 inches in length.
Female lake sturgeon mature at 24 to 26 years o: age and lengths of 52
to 55 inches.
Examination of Figure 7 reveals that, for the years 1974-1979,
the great majority of the sturgeon speared in Black Lake were more than
55 inches long. Virtually all of the fish taken in Mullett Lake during the
same period were more than 55 inches in length.
The catch from Black Lake for each individual year, divided by
length into two classes: those fish from 50-59 inches in length, and those
80

2
O
*
45 so 55 6o 65 7o 75 so
Length Class (Inches)
Figure 7. --Length frequency of lake sturgeon speared in Black
Lake, 1974-1979 (class length = 5 inches).
81
60 inches and larger is shown in Figure 8. In 5 years out of 6, the
percentage Of the catch 60 inches and larger exceeds the percentage
of 50- to 59-inch fish. This does not reflect a lack of the smaller
sturgeon, as Shouder (1975 and personal communication) has found a
substantial population of lake Sturgeon from 40 to 60 inches long during
his netting and tagging Operations. Judging from all available information
it would appear that either the smaller sturgeon do not frequent the
grounds where the winter spearing takes place or that they are being
passed up by spearers because the spearers do not judge them to be of
legal size.
Spear fishermen on Black Lake report that they seldom see
sman Sturgeon in the areas where Sturgeon fishing activity is concentrated.
Vondett (1957) mapped the traditional sturgeon spearing grounds of Burt,
Mullett, and Black lakes. My investigations reveal that these areas have
not changed in the ensuing years. Since most of the fishermen told Iſle
that they attempt to spear any fish that even approaches what they judge
to be legal size, and since most of the fish they spear are larger than 55
inches, it would appear that (1) the traditional sturgeon spearing grounds
are frequented by the larger fish, and (2) that the spearers may tend to
err in favor of the larger fish when judging whether or not a fish is of
legal size. Thus, the apparent size limit is higher than the legal minimum
size limit due to this combination of factors.
Based on the above information, it is recommended that the
50-inch minimum size limit be retained. Since the apparent size limit
82
1OOT []50-59 NCHES
-C 2, 60 INCHES AND OVER
O
tº 80H
O
Tº
3 6OH
H -
3
QD ºme
3, 40
º y
Caſ
QD
9 20H
QD
Cl-

# -º-º-º-º-º:
Year
Figure 8. --Percent composition of Black Lake sturgeon
harvest by individual years 1974-1979, for two length classes.
83
is closer to 55 inches, most of the fish should have the opportunity to
spawn at least once before becoming completely vulnerable to the fishery.
Raising the size limit to 60 inches (for example) would decrease the
harvest, but might also result in a larger number of sublegal sturgeon
being speared, since fish 55 inches and larger appear to frequent the
spearing areas, and also because spearers probably cannot estimate the
size of a fish within a margin of error closer than about 5 inches at the
depths where sturgeon are speared (usually about 20 feet). Thus the
minimum size limit, while effective in protecting Smaller individuals in -
hook-and-line fisheries where fish can be measured and released with a
fairly good chance of survival, is of less value in a spear fishery where
size must be estimated prior to capture and speared sublegal fish usually
do not survive.
validation of speared sturgeon by a DNR fishery biologist should
be continued. Acceptance o: this program by the fishermen has been very
good, and information gathered from speared fish is vital in Order to
monitor the effect of the fishery upon the population. Length, weight,
sex, and condition of the gonads should be recorded for all speared fish.
A pectoral fin-bone should be collected from all sturgeon under 100 pounds
in weight. Especially important are the ages of the smaller fish which
have just entered the fishery, in order to estimate the magnitude Of
recruitment into the fishery, the relative strength of individual year classes
and the ages of first and subsequent spawnings. This information, together
with the total catch, will give an indication of the size and age structure of
84
the population, the rate of exploitation, and trends in the population with
regard to numbers, growth, and mortality.
If it should become necessary at some future time, due to
increased fishing pressure and exploitation rates, to more severely
restrict the fishery, the most enforceable regulation would be to shorten
the season, rather than raise the minimum size limit. Cutting the length
of the season to the first 2 weeks of February would decrease the harvest
by an average of 34%. If the season were closed every other year, the
harvest would be cut by 50%. It is, of course, possible that the fishing
-pressure would increase with a shorter season, thus partially negating
the desired effect.
- The poaching of spawning lake sturgeon in the upper Black River
remains a serious problem. Since the magnitude o this illegal harvest
is unknown, it is potentially a much more serious threat to the Black Lake
population than is the legal fishery. Because of the remoteness of the area
º surrounding the upper Black River from Black Lake to Kleber Dam,
enforcement of the fishing ban in effect during April and May is very
difficult. In the future, it may be necessary to initiate continuous patrols
of the upper Black River by conservation officers during the sturgeon
spawning season, in order to discourage poachers. The Black Lake
sturgeon population is the largest inland stock in the state of Michigan
and supports most of the winter spear fishery. In order to maintain this
population and fishery, some extra effort by the law enforcement agencies
is certainly justifiable.
85
More research is necessary to determine the size of the sturgeon .
populations of Mullett and Burt lakes. Almost all of the sturgeon speared
in Mullett Lake are very large, and only a few fish are speared there
annually. It may be that reproduction is not occurring in the Mullett Lake
stock. It is possible that this population could benefit from the construction
of artificial spawning reefs like those installed in the upper Black River.
A study of possible sites for reef construction in the Pigeon River would
not be expensive or time consuming.
Sturgeon fishing pressure on Mullett Lake has traditionally been
low, but may increase rapidly in the next few years. During the 1980
Spearing season, a group of about 60 fishermen from Wisconsin fished
on Mullett Lake. These fishermen are veteran sturgeon spearers, most
having participated in the Sturgeon fishery of Lake Winnebago. Two very
large sturgeon (180 pounds and 104 pounds) were speared by Wisconsin
fishermen on the first day of the 1980 season. If the spearers from
Wisconsin continue to participate in the Mullett Lake fishery in the future,
the increased fishing pressure may be more than the apparently small
population can tolerate.
The sturgeon spear fishery of Burt Lake is, for all practical
purposes, gone. No fish have been taken there since 1974, and the size of
the remaining population is unknown. Virtually no fishermen actively
pursue sturgeon in Burt Lake anymore (Mason Shouder, personal
communication) and it seems likely that any sturgeon speared there in the
future will be taken incidental to other species (e.g., northern pike). An
86
assessment of the sturgeon population of Burt Lake, possibly during the
spawning season, should be done to ascertain whether or not enough fish
remain to justify a continued spearing season.
The Great Lakes and connecting waters
The illegal taking of spawning sturgeon from the St. Clair River
cannot be allowed to continue. The Lake St. clair sturgeon population is
the only known Great Lakes stock with a suitable spawning area and a -
natural potential to increase in numbers.
Since the Great Lakes and connecting waters are traditionally
considered as a management unit, it is proposed that the sturgeon season
in an Of these waters be closed during the months of May and June. If
vigorously enforced, this closure will allow surgeon in the St. Clair River
and elsewhere to spawn with a minimum of interference. It does not seem
unreasonable to protect a threatened species during the annual period of
reproduction. In the case of lake sturgeon, the spawning run is the period
of highest vulnerability to capture. During the rest of the year Sturgeon
in the Great Lakes are widely scattered and much less vulnerable to
recreational fishermen.
There is no reason why the sturgeon fishing season in the Great
Lakes cannot be allowed to continue during the rest of the year. The catch
of lake sturgeon by recreational fishermen is very small, amounting to
only a handful of fish annually. Thus, the harvest of lake sturgeon from
the Great Lakes by sport fishermen (excluding those taken during the
87
spawning season) has little or no impact upon the populations. In addition,
it seems unfair to expect a fisherman who has accidentally caught the
largest fish of his or her life to return it to the water.
Other lake sturgeon populations
The lake sturgeon populations present in the several inland lakes
of the Upper Peninsula (discussed earlier) bear further investigation
Attempts should be made to ascertain the size of these populations and
the extent Of reproduction. Also, the extent of the winter spear fisheries
(if any) should be determined. -
It is known that Indian Lake (Schoolcraft county) harbors a fair
number of sturgeon, as evidenced by the findings o: the U. S. Forest
Service survey in May 1979. At least one surgeon was taken there during
the 1980 spearing season, according to newspaper reports. It is suggested
that a netting survey, similar to that of Shouder (1975) be conducted on this
lake to determine whether or not the population is large enough to support
a fishery. Otter Lake (Houghton County) is also known to contain a
significant sturgeon population (Merle Galbraith, personal communication)
and would benefit from further research.
Recommendations for management of
lake Sturgeon populations statewide
It is suggested that the season creel limit for lake sturgeon
statewide be decreased from two fish per season to one. This will have
very little effect upon the annual harvest. (In Black Lake it will decrease
88 -
the harvest by only one or two fish annually.) Also, the creel limit is
ineffective as a means of more evenly distributing the harvest among
fishermen. Instead, the purpose of cutting the creel limit to one fish per
season is to promote the status of the lake sturgeon as a trophy fish. The
achievement of catching or spearing a large Sturgeon is akin to that of
bagging a trophy buck deer or a bear. (Indeed, catching a sturgeon,
especially on hook and line, is a great deal more difficult.) The state of
Wisconsin now allows only one sturgeon per spearer per year to be taken
from Lake Winnebago. -
Control of the illegal harvest of spawning sturgeon is essential
if existing sturgeon populations are to maintain themselves. Habitat -
improvements aimed at creating more sturgeon spawning habitat, such
as have been constructed in the upper Black River, should be made wherever
such structures are feasible on streams which have significant sturgeon
spawning runs. Spawning habitat improvement could be especially appropriate
for some of the Upper Peninsula populations such as Indian Lake.
More research is necessary concerning the early life history of the
lake sturgeon. The growth, mortality, movements, and food of lake Sturgeon
fry, and factors affecting spawning success and year class strength should
all be thoroughly investigated. Knowledge of these factors is especially
critical in fished populations, because of the 20-year time lag between the
time the fish are born and their entry into the fishery. If after a thorough
investigation it is found that reproduction is not occurring in a particular
population, the fishery utilizing that population should be closed and
remedial measures taken.
89
The Wisconsin Department of Natural Resources is about to
undertake a study of the early life history of the lake sturgeon in the
Lake Winnebago system. The work will begin in the spring of 1980
(James Kempinger, personal communication).
Artificial propagation of lake sturgeon is more feasible now than
in the past. The Russians are currently hatching sturgeon eggs, and have
released 243 million sturgeon fingerlings into the Volga River in the past
7 years (Whitney 1979). A detailed account of Russian Sturgeon culture
techniques is found in Bardach et al. (1972). Culture of lake Sturgeon by
the same methods is a distinct possibility. Lake sturgeon fingerlings
could be stocked in inland lakes, and in time could provide spear fisheries
similar to those of Black and Mullett lakes. Also, it is possible that
artificially cultured Sturgeon could be planted in some of the larger rivers
flowing into the Great Lakes (the Grand River, for example). These fish
would enter the Great Lakes and return when mature to spawn in their
"home" river, thus making them available to hook-and-line fishermen.
Both types of fisheries could be maintained by stocking.
In conclusion, the lake Sturgeon populations of Michigan and the
unique fisheries they provide can both be preserved (and in some cases
possibly increased) if they are closely monitored to prevent recruitment
overfishing and if suitable feeding and spawning habitat for Sturgeon
continues to be available.
LITERATURE CITED
Abramson, N. J. (compiler). 1971. Computer programs for fish Stock
assessment. Food Agr. Org. Fish. Tech. Pap. 101.
Baldwin, N. S., and R. W. Saalfeld. 1962. commercial fish production
in the Great Lakes. Great Lakes Fish. Comm. Tech. Rep. 3.
166 pp. -
Bardach, J. E., J. H. Ryther, and W. O. McLarney. 1972. Aquaculture
--the farming and husbandry of freshwater and marine Organisms.
Wiley-Interscience, New York. 868 pp. --
von Bertalanffy, L. 1938. A quantitative theory of organic growth.
Human Biol. 10: 181-213.
Beverton, R. J. H. , and S. J. Holt. 1957. On the dynamics of exploited
fish populations. Her Majesty's Stationery Office, London. 533 pp.
Burdick, M. E. 1968. Patience man, patience. Wisconsin Conserv. Bull.
33 (5): 24-25.
Carter, E. N. 1904. Notes on sturgeon culture in Vermont. Trans. Am.
Fish. Soc. 33: 60-75.
Cochran, W. G. 1963. Sampling techniques. (2nd ed.) Wiley & Sons,
New York. 165 pp.
Cuerrier, J. P. 1951. The use of pectoral fin rays for determining age
of sturgeon and other species of fish. Can. Fish Cult. 11: 10-18.
90
91
Cushing, D. H. 1968. Fisheries biology. A study in population dynamics.
Univ. Wisconsin Press, Madison. 200 pp.
Cushing D. H. 1975. Marine ecology and fisheries. cambridge University
press. 278 pp. -
Eddy, S., and T. Surber. 1943. Northern fishes. Sturgeon. pp. 57–61.
Univ. Minnesota Press.
Evans, R. J. , J. D. Bails, and F. M. D'Itri. 1972. Mercury levels in
muscle tissues of preserved museum fish. Env. Sci. Tech. 6:
90 1-905.
Everhart, H., A. W. Eipper, and W. D. Youngs. 1975. Principles of
fishery science. Cornell Univ. Press. 288 pp.
Fogle, N. E. 1975. Michigan's oldest fish. Mich. Nat. Resources
44(1): 32-33.
Great Lakes Fishery Commission. 1970. Supplement to Tech. Rep. 3.
96 pp.
Harkness, W. J., and J. R. Dymond. 1961. The lake surgeon. The
history of its fishery and problems of conservation. Ontario
Dep. Lands Forests, Fish Wildl. Branch. 121 pp.
Hoffman, G. L. 1967. Parasites of North American freshwater fishes.
Univ. Calif. Press, Los Angeles. 486 pp.
Hoffman, G. L., E. V. Raikova, and W. G. Yoder. 1974. Polypodium sp.
(Coelenterata) found in North American sturgeon. J. Parasit.
60 (3): 548-550.
92 -
Leach, G. C. 1920. Artificial propagation of sturgeon. Review of sturgeon
culture in the United States. Report U. S. Fish Comm. for 1919,
App. III.
MacKay, H. H. 1963. Fishes of Ontario. Ontario Dep. Lands Forests,
Fish Wildl. Branch. 300 pp.
Margolis, L., and J. R. Arthur. 1979. Synopsis of the parasites of
fishes of Canada. Fish. Res. Board Can. Bull. 199. 269 pp.
Michigan Department of Natural Resources. 1976. Michigan's endangered
and threatened species program.
Michigan State Board of Fish Commissioners. 1890. Ninth Biennial
Report. p. 44.
Michigan State Board of Fish Commissioners. 1895. Eleventh Biennial
Report. p. 28.
Michigan State Board of Fish Commissioners. 1899. Thirteenth Biennial
Report. p. 26.
Milner, J. W. 1874. The fisheries of the Great Lakes. U.S. Fish.
Comm. Rep. 2: 67–75. (Report for 1872–1873).
Organ, W. L. . G. L. Towns, M. O. Walter, R. D. Pellitier, and
D. A. Riege. (unpublished) Past and presently known spawning
grounds of fishes in the Michigan coastal waters of the Great -
Lakes. Michigan Dep. Nat. Resour. Fish Div. Tech. Rep. 79- 1.
Paulik, G. J., and W. H. Bayliff. 1967. A generalized computer program
for the Ricker model of equilibrium yield per recruitment.
J. Fish. Res. Board Can. 24(2): 249-259.
93
Priegel, G. R. 1973. Lake sturgeon management on the Menominee
River. Wisconsin Dep. Nat. Resour. Tech. Bull. 67. 20 pp.
Priegel, G. R. , and T. L. Wirth. 1975. Lake sturgeon harvest, growth,
and recruitment in Lake Winnebago, Wisconsin. Wisconsin Dep.
Nat. Resour. Tech. Bull. 83. 25 P9.
Priegel, G. R. , and T. L. Wirth. 1977. The lake sturgeon: its life
history, ecology and management. wisconsin Dep. Nat. Resour.
Publ. 4-3600 (77). 19 pp.
Priegel, G. R. , and T. L. Wirth. 1978. Lake sturgeon populations,
growth, and exploitation in lakes Poygan, Winneconne, and Lake
Butte Des Morts, wisconsin. Wisconsin Dep. Nat. Resour.
Tech. Bull. 107. 23 pp.
Probst, R. T., and E. L. Cooper. 1955. Age, growth, and production
of the lake sturgeon (Acipenser fulvescens) in the Lake Winnebago
region, Wisconsin. Trans. Am. Fish.Soc. 84 : 207-227.
Post, H. 1890. Sturgeon; experiments in hatching. Trans. Am. Fish.
Soc. 19: 36-40.
Ricker, W. E. 1958. Handbook of computations for biological statistics
of fish populations. Fish. Res. Board Can. Bull. 119. 300 pp.
Ricker, W. E. 1975. Computation and interpretation of biological
statistics of fish populations. Fish. Res. Board Can. Bull. 191.
382 pp.
Robson, D. S., and H. A. Regier. 1964. Sample size in Petersen mark-
recapture experiments. Trans. Am. Fish. Soc. 93(3): 215-226.
94
Roussow, G. 1957. Some considerations concerning sturgeon spawning
periodicity. J. Fish. Res. Board Can. 14: 553–572.
Scott, W. B. , and E. J. Crossman. 1973. Freshwater fishes of canada.
Fish. Res. Board Can. Bull. 184. 966 pp.
Shouder, M. F. 1975. A progress report on the lake sturgeon in the
Black Lake system, Cheboygan and Presque Isle counties.
Michigan Dep. Nat. Resour. Fish. Div. Tech. Rep. 75-8. 6 pp.
Stone, L. 1901. Sturgeon hatching in the Lake Champlain basin.
Trans. Am. Fish. Soc. 30: 137-143.
Tody, W. H. 1974. Whitefish, sturgeon, and the early Michigan
commercial fishery. Pages 45-60 in Michigan Fisheries
centennial Report 1873- 1973. Michigan Dep. Nat. Resour.
Fish. Div. Manage. Rep. 6.
U.S. Department of the Interior. Bureau of Sport Fisheries and Wildlife.
1966. Rare and endangered fish and wildlife of the United States.
Sheet F-2. -
Van Oosten, J. 1956. The lake sturgeon in our endangered wildlife.
National Wildl. Fed. Washington, D.C. pp. 9-10.
Vondett, H. J. 1957. A questionnaire census of sturgeon spearing.
January–February, 1956, on Black, Burt, and Mullett lakes,
Cheboygan County. Mich. Dep. Nat. Resour. , Inst. Fish.
Res. Rep. 1529. 12 pp.
95
Vondett, H. J., and J. E. Williams. 1961. The sturgeon fishery of
Black, Burt, and Mullett lakes, Cheboygan County, 1957-1958.
Mich. Dep. Nat. Resour., Inst. Fish. Res. Rep. 1616. 29 pp.
Whitney, C. R. 1979. Where caviar comes by the ton.
Internat. Wildl. 9(6): 4-11.
Williams, J. E. 1951. The lake Sturgeon.
Mich. Conserv. 20 (6): 15-18.
Wing, Talcotte E. (editor) 1890. History of Monroe County.
Munsell & Co., New York.
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