Dynamics of the Lake Michigan food
web, 1970-2000
Charles P. Madenjian, Gary L. Fahnenstiel,
Thomas H. Johengen, Thomas F. Nalepa,
Henry A. Vanderploeg, Guy W. Fleischer,
Philip J. Schneeberger, Darren M. Benjamin,
Emily B. Smith, James R. Bence,
Edward S. Rutherford, Dennis S. Lavis,
Dale M. Robertson, David J. Jude, and
Mark P. Ebener
USGS Great Lakes Science Center
NOAA Great Lakes Environmental Research
Laboratory
Michigan Department of Natural Resources
Atlantic States Marine Fisheries Commission
Michigan State University
University of Michigan
U. S. Fish and Wildlife Service
USGS Water Resources Division
Chippewa Ottawa Resource Authority
Salmonid Communities in Oligotrophic Lakes
(SCOL)
SCOL-1 focused on changes in the fish community
between 1880s and 1970.
Commercial harvest was used as an index of fish
abundance.
Each of the five Laurentian Great Lakes was
examined.
For SCOL-1, changes in the fish community were
attributed to 3 anthropogenic stressors:
1. Overexploitation of fish stocks
2. Eutrophication and pollution
3. Introduction of exotics
Wells and McLain (1973) concluded that the
invasions of sea lamprey and alewife had
devastating effects on the Lake Michigan fish
community.
Sea lamprey invasion was linked to declines in
abundance of lake whitefish, burbot, and lake trout.
Alewife invasion was linked to declines in
abundance of emerald shiner, yellow perch,
deepwater sculpin, burbot, walleye, and bloater.
SCOL-2
Identify changes in the lake food web during 19702000, in context of the following 5 anthropogenic
stressors:
1. Overexploitation of fish stocks
2. Oligotrophication
3. Introduction of exotics
4. Contaminants
5. Global climate change
Objectives
• Document changes in the Lake Michigan
food web during 1970-2000
• Explain these changes in the food web, in
context of anthropogenic stressors
Available tools
• Long-term surveys of biota
• Flow models
• Catch-at-age models
• Bioenergetics models
• Long-term surveys of contaminants in biota
Available tools
• Long-term records of commercial and
recreational harvest of fish
• Long-term records of air and water temperatures
• Diet composition data for fish
• Lipid content data for fish
• Across – lakes comparisons
Phosphor us loading (m etr ic tons)
8000
7000
6000
5000
4000
3000
2000
1970
1975
1980
1985
Year
1990
1995
1972
1998-2000
Chlor ophyll a (m icrograms/L)
15
12
9
6
3
0
St. Joseph 1
St. Joseph 2
Muskegon
Chlor ophyll a (m icrograms/L)
3
2
1
0
1970
1975
1980
1985
Year
1990
1995
2000
Lake Michigan zooplankton,
1970-2000
• Although species composition of the
crustacean zooplankton community changed
considerably during 1983-1992 in the
offshore waters of Lake Michigan,
crustacean zooplankton biomass varied
without trend during that time
Changes in Lake Michigan
zooplankton, 1970-2000
• Summer daphnid assemblage shifted from a
community dominated by Daphnia retrocurva
during 1972-1976 to a community dominated by
D. galeata mendotae during 1977-1981
• Daphnia pulicaria appeared in 1982 and was an
important part of the zooplankton community
during 1983-1984, but was nearly absent by 1987
Changes in Lake Michigan
zooplankton, 1970-2000
• Spiny water flea Bythotrephes cederstroemi
invaded Lake Michigan in 1986
• Decrease in Daphnia retrocurva abundance
following 1986 was likely attributable to
predation by Bythotrephes
Mysis diluviana in Lake
Michigan, 1970-2000
• Abundance of Mysis diluviana in southern
Lake Michigan has remained relatively
stable from the 1970s through 1998
Bloater
Sculpins
Alewife
Lake
Michigan’s
Planktivore
Prey fishes
Rainbow smelt
Prey base support of
valuable predators
Commercial fisheries
N umer i c densi t y ( number / ha)
Adult alewif e
700
600
500
400
300
200
100
0
1973
1981
1989
1997
2005
1981
1989
1997
2005
Bi omass densi t y ( kg/ ha)
30
20
10
0
1973
Year
Lake Michigan salmon in es
Biom ass (thousands of m etric tons)
32
24
16
8
0
1965
1970
1975
1980
1985
Year
1990
1995
2000
Adult Bloaters
CPE (Number/Tow)
1200
1000
800
600
400
200
0
1975
1978
1981
1984
1987
1990
1993
1996
1999
YOY Bloaters
CPE(Number/Tow)
500
400
300
200
100
0
1975
1978
1981
1984
1987
1990
1993
1996
1999
N umer i c densi t y ( number / ha)
Adult r ainbow smelt
600
500
400
300
200
100
0
1973
1981
1989
1997
2005
1981
1989
1997
2005
Bi omass densi t y ( kg/ ha)
7
6
5
4
3
2
1
0
1973
Year
Trends in Sculpin Abundance
700
Slimy sculpin
Deepwater sculpin
CPE (number/tow)
600
500
400
300
200
100
0
1975
1980
1985
1990
1995
2000
Trends in Sculpin Abundance
700
Slimy sculpin
Deepwater sculpin
CPE (number/tow)
600
500
400
300
200
100
0
1975
1980
1985
1990
1995
2000
LAT
BRT
RBT
CO
CHS
Biom ass (thousands of m etric tons)
32
24
16
8
0
1965
1975
1985
Year
1995
Consum ption (thousands of m etric tons)
LAT
BRT
RBT
CO
CHS
140
120
100
80
60
40
20
0
1965
1975
1985
Year
1995
Consum ption (thousands of m etric tons)
LG AL
SM AL
OTHER
140
120
100
80
60
40
20
0
1965
1975
1985
Year
1995
Lake whitefish
Har vest (m etric tons)
4000
3000
2000
1000
0
1970
1980
1990
Year
2000
Age 4
Age 5
Age 6
Lake whitefish condition (K)
1.20
1.10
1.00
0.90
0.80
0.70
1985
1990
1995
Year
2000
Emerald shiner in Lake
Michigan, 1970-2000
• Emerald shiner abundance has remained at
very low levels
• Perhaps alewife abundance is still
sufficiently high to interfere with emerald
shiner reproduction
Lake sturgeon in Lake Michigan,
1970-2000
• Lake sturgeon population collapsed during early
1900s due to overexploitation and habitat
degradation
• During the 1990s, small populations associated
with at least 13 Lake Michigan tributaries
• With continued removal of dams on tributaries,
lake sturgeon population should increase in size
Round goby in Lake Michigan,
1970-2000
• Invaded Lake Michigan during the 1990s
• Established populations in harbors around
the lake
• Decline in mottled sculpin abundance in
Calumet Harbor linked to
round goby invasion
Contaminant stressor in Lake
Michigan, 1970-2000
• Great Lakes Water Quality Agreement in 1972 led
to remedial actions in areas of concern
• Production of PCBs banned in 1970s
• Use of pesticide DDT discontinued in 1970s
• Uses of pesticides chlordane and dieldrin became
restricted during 1970s
30
Thousands of nests
D ouble -crest ed cormora nts
20
10
0
1975
1980
1985
1990
Year
1995
2000
Global climate change stressor in
Lake Michigan, 1970-2000
• Very gradual changes in biota expected
• Magnuson et al. (1997) reviewed predictions for
changes in Great Lakes food webs due to global
warming
• Two long-term time series for Lake Michigan
water temperature have been examined
• One site at St. Joseph and one site in southern
Green Bay
Global climate change stressor in
Lake Michigan, 1970-2000
• Neither site exhibited an overall increasing
trend in water temperature
• Duration of summer stratification
significantly increased at the St. Joseph site
• To date, unable to ascribe changes in the
Lake Michigan food web to global climate
change
Manipulations of Lake Michigan
ecosystem during past 40 years
• Sea lamprey control (beginning in 1950s)
• Major stocking program for salmonines
(beginning in 1965)
• Reduction in phosphorus loadings
(beginning around 1980)
• Bans on pesticides and PCBs (in 1970s)
Sea lamprey control
• Enabled the buildup of salmonine
populations between 1965 and early 1980s
• Set the stage for lake whitefish recovery
beginning in 1960s
• Set the stage for burbot recovery beginning
in 1980s
Stocking of salmonines
• Stocking of salmon and trout was successful in
reducing alewife abundance
• Reduction in alewife abundance likely led to
recoveries of burbot, yellow perch, and deepwater
sculpin populations during the 1980s
• Reduction in alewife abundance likely enabled the
appearance of Daphnia pulicaria during 19821987
Reduction in phosphorus loadings
• Phosphorus loadings to Lake Michigan declined
substantially during 1980-1987, but have leveled
off since 1987
• Decrease in phosphorus loadings probably led to
the apparent decrease in primary production in
nearshore waters between 1970 and 2000
• Decrease in primary production in nearshore
waters was likely responsible for the observed
decrease in density of benthic macroinvertebrates
between 1980 and 1993
Continued decrease in Diporeia
abundance
• Associated with the zebra mussel invasion
during the 1990s
• Mechanisms by which zebra mussels are
negatively affecting Diporeia remain
unidentified
Have “bottom-up” effects led to a
reduction in fish abundance?
• Salmonine, burbot, lake whitefish, alewife,
and sculpin abundances did not decrease
during the 1990s
• Bloater abundance appears to be cyclic
• Difficult to “prove” that bottom-up effects
have led to reduced fish abundance
Have “bottom-up” effects led to a
reduction in fish condition?
• Decline in lake whitefish condition and growth
between 1995 and 2000 associated with zebra
mussel invasion and decline in Diporeia
• Decrease in alewife condition and growth during
1990s associated with decline in Diporeia
Bans on pesticides and PCBs
• Increase in size of double-crested cormorant
population during 1980s and 1990s is
linked, at least in part, to decrease in DDE
(metabolite of DDT) concentration in the
birds
Overexploitation of fish stocks
• Likely responsible, in part, for the
prolonged period of reduced yellow perch
recruitment during the 1990s
Additional conclusions
• No trend in primary production in offshore waters
from early 1970s to 2000
• No trend in crustacean zooplankton biomass in
offshore waters from 1983 to 2000
• No trend in Mysis abundance from 1970s to 2000
• Decrease in deepwater sculpin abundance during
late 1980s was likely attributable to predation by
burbot
Additional conclusions
• Alewives have a “double whammy” effect on lake
trout natural reproduction
• Alewives prey upon lake trout fry
• A diet rich in alewives can lead to low levels of
thiamine (B1 vitamin) in adult lake trout, leading
to low levels of thiamine in lake trout eggs and
lower survival of lake trout eggs and fry
• Alewives represent the most serious impediment
to lake trout restoration in Lake Michigan today
Additional conclusions
• Bloater abundance may be exhibiting quasiregular cycles with a period of approximately 30
years
• These cycles may be largely independent of
human interventions and interactions with other
fish populations
• To understand the food web dynamics in an
ecosystem as large and complex as Lake
Michigan, the importance of long-term research
can not be overstated