Saginaw Bay Spawning Reef Assessments
Posted: February 13th, 2026, 9:49 am
Showcasing the DNR: Don’t put all your (fish) eggs in one basket
Thu, Feb 12, 2026 at 2:03 PM
Restored reef in Saginaw Bay diversifies spawning habitat and promotes resilience
Showcasing the DNR
Don ’t put all your (fish) eggs in one basket
Restored reef in Saginaw Bay diversifies spawning habitat and promotes resilience
By JEFFREY JOLLEY, PhD., Southern Lake Huron unit manager
Fisheries Division, Michigan Department of Natural Resources and MARCEE
WARDELL, communications specialist, Fisheries Division, Michigan DNR
Imagine a reef: sunlight streaming through the azure water reveals a vibrant
underwater community, where fish, large and small, dart into holes and crevices or
swim around the reef’s edges while other aquatic creatures make their homes or
search for food.
2/13/26, 1:51 AM
Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
Did you think of a coral reef, covered in pink anemones and surrounded by brightly
colored tropical fish like blue tang and clownfish?
Now imagine a reef, with dappled sunlight and teeming with fish, in Lake Huron, in
Saginaw Bay.
Surprised?
Maybe you shouldn’t be.
aquatic species.
The disappearance of rocky reefs
Reefs used to be common in
Saginaw Bay, and organizations
like the Michigan Department
of Natural Resources and
others are working to restore
reef habitat for the benefit of
f
ish like lake whitefish and
walleye, as well as many other
Though corals did once thrive in the northern Lower Peninsula about 350 million
years ago (the remains of which are now
Petoskey stones), the reefs that existed
in Saginaw Bay were rock reefs. These reefs, mainly comprised of granite and
limestone, were formed by the movement of glaciers.
Since Saginaw Bay has an otherwise very flat bottom and a relatively consistent
depth (about 25 to 30 feet), the thousands of acres of reef in the bay were
important habitat for the bay’s aquatic species, providing places to deposit eggs,
hide from predators or find a meal.
Rock reefs are comprised of cobble – rocks that vary in size from about the size of
an orange to the size of a basketball, piled and rising from the lake bottom.
These stones of different sizes create crevices – called interstitial spaces – and
ledges perfect for spawning fish to deposit eggs into and for young fry (newly
hatched fish) to hide from predators.
Reefs, depending on their location and depth, can get a lot of wave action. The
continual movement of water keeps sediment from building up and filling in those
useful interstitial spaces. It also washes oxygenated water over fertilized fish eggs,
which they need to develop and hatch into healthy fry.
But what happened to the reefs in Saginaw Bay? They were buried.
2/11
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Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
Logging, industrial and agricultural land uses in the area surrounding the bay
exposed sediments, which caused excess erosion and movement of sediment,
which washed out into the bay, covering the rocky structures.
Dredging the lake bottom to remove this sediment and resurface the original rock
reefs would be incredibly costly and disruptive to the use of the bay by humans and
f
ish, if not economically impossible. It would also likely be ineffective, given current
activity in the region causing continued sedimentation.
Check out a video on the project.
The solution researchers have arrived at is to restore reef habitat not by
resurrecting remnants of former reefs, but by building new ones. This kind of reef
restoration work is gaining traction in the Great Lakes and elsewhere.
Walleye decline and recovery strategies
The reef habitat restoration story in Saginaw Bay begins not with a project, but a
problem. Historically,
walleye were abundant in Saginaw Bay. But in the 1940s, this
f
ish population collapsed due to declines in water quality and habitat, caused by
pollution and sedimentation, along with unrestrained fishing .
The opportunity to recover walleye came after the
Clean Water Act took effect in
the early 1970s and the negative impacts were better managed around in the bay.
The DNR began stocking walleye, which boosted the population, but the fishery
didn’t recover to pre-1940s levels and remained dependent on stocking.
DNR researchers attributed
that to
degraded and
ongoing degradation of
spawning habitat (particularly
rock reefs, but also dams
blocking migrating fish), along
with walleye fry predation
from invasive alewives.
Then suddenly, something shifted.
“Along comes 2003, and we have this big food web change in Lake Huron and
invasive alewives disappear,” said Dr. David Fielder, fisheries research biologist with
the DNR and one of the authors of the report resulting from the research.
This change, due in part to increased predation on alewife by other fish, but mostly
by the invasion of dreissenid mussels – zebra and quagga mussels, which consume
3/11
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much of the phytoplankton that are the base of the food chain – reduced the
number of alewives eating walleye fry.
This had a big effect, and reproductive success boomed. Stocking was discontinued
in 2006, and by 2009, walleye abundance reached recovery targets.
Even though walleye populations were seemingly back to normal, work remained to
be done.
Researchers noted that since rock reef habitat was lost in the bay, the walleye that
demonstrated sustained reproduction were primarily spawning in the tributary
rivers, among them the Saginaw River.
That’s not ideal, because it makes the walleye population vulnerable to changes in
those rivers, like barriers, contamination or natural disasters.
If the river spawning habitat isn’t available, the walleye will be unable to reproduce
with much success. According to Fielder, whether fish spawn in a river or on a reef is
something they likely inherit from their parents, not something they choose based
on environmental conditions.
Without preferred spawning habitat, walleye are left to deposit their eggs wherever
they can. In the case of the few reef-spawning walleye still hanging on in the bay,
this is often on the bottom of the lake.
But eggs on the bottom have a low chance of hatching out into fry, as the dissolved
oxygen they need to develop is low and they’re not hidden from the predators that
like to eat them. Plus, sediment can bury the eggs, just like it buried the former rock
reefs.
While restoration efforts won’t bring back all the rocky reefs once present in the
bay, restoring some of that habitat will still be immensely beneficial.
The metaphor project partners have used to describe this is the portfolio effect: Like
diversifying your investment portfolio can help you weather volatility in the market,
diversification of spawning habitat can help insulate the species from the effects of
big ecosystem changes.
The goal isn’t necessarily more walleye reproduction but more consistent or
dependable walleye reproduction. To ensure a resilient walleye population in
Saginaw Bay, walleye need various spawning habitats, both reef and river.
Lake whitefish spawning in Saginaw Bay
4/11
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Lake whitefish are an incredibly important species in the Great Lakes and Saginaw
Bay, ecologically and culturally, and they are the mainstay of the bay’s state-licensed
commercial fishery.
However,
lake whitefish
populations are in decline
across the Great Lakes,
including Lake Huron, and have
been for years – except for in
the central and lower half of
Lake Huron, which is
something of a stronghold for
the species. Researchers believe this is likely supported by Saginaw Bay, as it’s a
crucial spawning location.
While the ecological changes brought on by zebra and quagga mussels, in particular
the collapse of alewife, seemingly helped walleye populations, they have not had a
positive effect on lake whitefish.
These mussels’ voracious consumption of phytoplankton has devastated the
zooplankton and benthic macroinvertebrates – small marine animals – that not only
alewife but also whitefish fry depend on for early growth. Fry that don’t get enough
food grow slowly and fail to survive to older ages.
The proliferation of dreissenid mussels has had another effect on the lakes,
noticeable even to nonexperts: The water is much clearer. This is due, again, to their
feeding habits, pulling zooplankton and algae out of the water.
Clear water might seem pleasant, but it’s not good for native fishes like lake
whitefish. Additional UV light penetration of the water essentially gives lake
whitefish eggs and fry extreme sunburns, which reduce their survival.
This effect is magnified by the increase in mild winters as the climate changes. Less
ice coverage means even more UV light penetrating the water and harming
developing whitefish.
While managing invasive mussels and their impacts on spawning grounds is still
experimental (through efforts such as the
Great Lakes SWIM project), creating
suitable spawning habitats in productive areas like Saginaw Bay should still benefit
whitefish.
Whitefish also use reefs for spawning, so like walleye, restored reef habitat will
likely improve survival for eggs and fry. Coreyon Reef, an earlier offshore reef
5/11
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project in Saginaw Bay, has already seen whitefish and walleye adoption for
spawning.
What about yellow perch?
Yellow perch are one of the most popular species among Great Lakes anglers, as
demonstrated by
DNR creel surveys, and for good reason. They’re a good fish for
beginners to target, and they’re fun to ice fish for, too.
But will efforts to bolster lake whitefish and walleye population resilience hurt
yellow perch populations, as many anglers fear?
“Perch are really important; we’re working hard to do what we can for perch
recovery in Saginaw Bay,” Fielder said.
Yellow perch today are at a fraction of their historical abundance in the bay. Yellow
perch spawning is strong, but the yearling perch currently have low survival rates.
This can be attributed largely to predation by larger fish, particularly walleye.
In the past, fisheries managers attempted to fix this by reducing the yellow perch
harvest limit, reducing commercial licenses targeting yellow perch and increasing
harvest opportunity for walleye.
None of these approaches improved perch survival.
Why? While walleye have reached
recovery targets, not all
ecological functions of the bay
are restored.
In the past, abundant pelagic
(midwater) prey fish
populations likely created a
predation buffer to allow for
better perch survival. Those used to be invasive alewife, and earlier, the native cisco
(lake herring). Both are absent now.
The Michigan DNR has
partnered with the U.S. Fish and Wildlife Service to
reintroduce cisco into Saginaw Bay to try to help restore that part of the fish
community, which could ultimately benefit yellow perch abundance.
The Walleye and Yellow Perch Recreational Management Plan for Saginaw
Bay, published by the DNR in 2025, focuses on finding balance between walleye
6/11
Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
and yellow perch in the bay. While walleye do prey on yellow perch, these species
can coexist at desired levels in the bay, and historically, they did.
Restoring reef habitat in the bay
“In that original 2004 plan, we prescribed a lot of different strategies for walleye
recovery,” Fielder said. “One of them was to invest in rock reef restoration in
Saginaw Bay.”
The plan called for two kinds of reefs, offshore and nearshore, with the intention of
seeing which type of reef would be most beneficial. But once initial benchmarks for
walleye recovery in Saginaw Bay had been met, there was little momentum (or
funding) to pursue reef restoration.
The result was
2019.
Coryeon Reef, an offshore reef in inner Saginaw Bay completed in
While a nearshore reef was also considered at the time, further engagement with
the local community was needed to find a site that would deliver the intended
nearshore habitat to native fishes without impeding use of the bay for boating.
The opportunity to pursue a nearshore reef came in the form of funding from the
National Coastal Resilience Fund (a partnership between the National Fish and
Wildlife Foundation and National Oceanic and Atmospheric Administration) for a
feasibility study on further restoration projects in Saginaw Bay.
Channel Island Reef was one of three projects included in the feasibility study, and it
was the one the partners decided to pursue at this time. The other possible
projects, focused on reducing sedimentation and attenuating wave action in flood
prone areas, may be considered for future restoration work in the bay.
Using what they’d learned from the feasibility study, public engagement efforts
headed up by Michigan Sea Grant and the implementation of Coryeon Reef a few
years prior, the team – including DNR, EGLE, GLFC, NOAA, Michigan Sea Grant, and
Environmental Consulting and Technology – set about constructing Channel Island
Reef to the east of Channel Island (also known as Spoils Island, Shelter Island or U.S.
Army Corps Confined Disposal Facility).
Construction began on Sept. 8, 2025, and was completed on Oct. 10, 2025.
The process for building the reef was straightforward: Pieces of limestone, quarried
locally in the Thumb area of Michigan, were moved out to the reef location on
barges. A crane, also on a barge, used a claw to pick up the stone cobble and drop it
into place.
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Channel Island Reef is about
2.5 acres, approximately 190
feet wide and 570 feet long.
The reef is located about 2
miles from the mouth of the
Saginaw River, a half mile east
of Channel Island. It is
underwater, sitting 5.5 feet
below the surface when water levels are lowest, which ensures that it poses a
minimal hazard to navigation.
Funding for construction of the reef came from several sources: the Great Lakes
Restoration Initiative, Great Lakes Fish and Wildlife Act, NOAA, and the
Natural
Resource Damage Assessment and restoration settlement with Dow Chemical.
NRDA funding helps restore ecosystem function and uses of public natural resources
that have been compromised by the release of hazardous substances into the
environment.
In addition to NRDA funds, grant funding is necessary for getting these kinds of
projects off the ground. In times when everyone is feeling the financial pinch, grants
allow the DNR and partners to accomplish large projects that would otherwise be
financially out of reach for the organizations on their own.
The entire reef construction process was funded through grants or settlement, not
by state tax dollars or license fee revenue.
‘We’re going to learn a ton’
What’s exciting about this project for researchers like Dr. Fielder is the learning
opportunity that it presents.
Before either reef was constructed, assessment projects were conducted in the area
to learn about the species that were using it and the predators that were present,
as well as the dissolved oxygen levels, water temperatures and other environmental
conditions. Similar assessments were conducted after the installation of Coreyon
Reef, for comparison.
“This before and after investigation really helps inform us on what we achieved with
this reef reconstruction,” Fielder said.
The assessments found that walleye and lake whitefish both adopted Coryeon Reef
for spawning almost immediately. The nearshore Channel Island Reef could have
similar results.
8/11
“I'm excited for the completion of the Channel Island Reef construction. During my
PhD research at Purdue University in collaboration with DNR, we found lake
whitefish and walleye were already spawning on Coreyon Reef just a year after its
construction,” said Dr. Scott Koenigbauer, fisheries biologist with USFWS working
out of the Alpena Fish and Wildlife Conservation Office.
“We found both species were releasing more eggs at the Coreyon Reef site after its
restoration than before. We also observed a variety of species there, including
yellow perch, lake trout, burbot and cisco, during our surveys.”
Koenigbauer believes that future work will likely demonstrate that spawning reefs in
Saginaw Bay support stability for key species.
“With the construction of
Channel Island Reef, scientists
can now compare how these
species utilize nearshore and
offshore restored reefs in
Saginaw Bay,” he said.
Historically, we know that
there were both nearshore and
offshore reefs in the bay.
“The question is: Offshore, in the open water, will the fish find and use that reef, or
will they prefer a more nearshore environment?” Fielder said.
“Success in this rocky habitat requires lots of hydraulic agitation. That keeps the
water refreshed, oxygenated and clean of sediment. So, a nearshore reef that’s
shallower and has more wave agitation may perform differently – may perform
better – than the offshore Coryeon Reef.”
As with Coreyon Reef, Dr. Fielder and staff at the
Alpena Fisheries Research Station will be working with Purdue University to conduct assessments on the reef.
Starting in the spring, the researchers will start a two-year evaluation period,
monitoring the long-term effects of the reef. Some questions they’ll be investigating
are whether the fish are using the reef, whether they’re using it more or less than
Coryeon (which will also be evaluated during this period) and whether sediment or
dreissenid mussels are affecting the habitat.
Studying the reef could have implications for future projects – if Channel Island and
Coreyon Reefs are a success, there could be interest in more reef restoration work,
9/11
While Saginaw Bay hasn’t always received the same attention as other parts of the
Great Lakes, that’s changing.
The area’s agriculture and industry have contributed significantly to the success of
the state’s economy, but current and historical land and water use practices
resulting from this hard work have degraded aquatic habitat.
So, while the bay has an excellent fishery, there’s room for improvement and
habitat restoration.
This opportunity for improvement has sparked interest in restoring and enhancing
the bay’s natural resources. Funding agencies are poised to invest in Saginaw Bay
and its watershed, and there’s no shortage of creative thinking when it comes to
habitat improvement efforts, from reef restoration to fish passage solutions to
stream barrier removal. Channel Island reef is one of many such projects on
Saginaw Bay’s recovery arc.
Reef-4: Construction on Channel Island Reef began on Sept. 8, 2025, and was
completed on Oct. 10, 2025. (Photo: Zak Allan, Great Lakes Fishery Commission)
Reef-5: Limestone cobble was built up to create a rock reef that sits 5.5 feet below
the surface when water levels are lowest. (Photo: Zak Allan, Great Lakes Fishery
Commission)
The Michigan Department of Natural Resources is committed to the conservation,
protection, management, use and enjoyment of the state's natural and cultural
resources for current and future generations. For more information, go to
Michigan.gov/DNR.
Thu, Feb 12, 2026 at 2:03 PM
Restored reef in Saginaw Bay diversifies spawning habitat and promotes resilience
Showcasing the DNR
Don ’t put all your (fish) eggs in one basket
Restored reef in Saginaw Bay diversifies spawning habitat and promotes resilience
By JEFFREY JOLLEY, PhD., Southern Lake Huron unit manager
Fisheries Division, Michigan Department of Natural Resources and MARCEE
WARDELL, communications specialist, Fisheries Division, Michigan DNR
Imagine a reef: sunlight streaming through the azure water reveals a vibrant
underwater community, where fish, large and small, dart into holes and crevices or
swim around the reef’s edges while other aquatic creatures make their homes or
search for food.
2/13/26, 1:51 AM
Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
Did you think of a coral reef, covered in pink anemones and surrounded by brightly
colored tropical fish like blue tang and clownfish?
Now imagine a reef, with dappled sunlight and teeming with fish, in Lake Huron, in
Saginaw Bay.
Surprised?
Maybe you shouldn’t be.
aquatic species.
The disappearance of rocky reefs
Reefs used to be common in
Saginaw Bay, and organizations
like the Michigan Department
of Natural Resources and
others are working to restore
reef habitat for the benefit of
f
ish like lake whitefish and
walleye, as well as many other
Though corals did once thrive in the northern Lower Peninsula about 350 million
years ago (the remains of which are now
Petoskey stones), the reefs that existed
in Saginaw Bay were rock reefs. These reefs, mainly comprised of granite and
limestone, were formed by the movement of glaciers.
Since Saginaw Bay has an otherwise very flat bottom and a relatively consistent
depth (about 25 to 30 feet), the thousands of acres of reef in the bay were
important habitat for the bay’s aquatic species, providing places to deposit eggs,
hide from predators or find a meal.
Rock reefs are comprised of cobble – rocks that vary in size from about the size of
an orange to the size of a basketball, piled and rising from the lake bottom.
These stones of different sizes create crevices – called interstitial spaces – and
ledges perfect for spawning fish to deposit eggs into and for young fry (newly
hatched fish) to hide from predators.
Reefs, depending on their location and depth, can get a lot of wave action. The
continual movement of water keeps sediment from building up and filling in those
useful interstitial spaces. It also washes oxygenated water over fertilized fish eggs,
which they need to develop and hatch into healthy fry.
But what happened to the reefs in Saginaw Bay? They were buried.
2/11
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2/13/26, 1:51 AM
Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
Logging, industrial and agricultural land uses in the area surrounding the bay
exposed sediments, which caused excess erosion and movement of sediment,
which washed out into the bay, covering the rocky structures.
Dredging the lake bottom to remove this sediment and resurface the original rock
reefs would be incredibly costly and disruptive to the use of the bay by humans and
f
ish, if not economically impossible. It would also likely be ineffective, given current
activity in the region causing continued sedimentation.
Check out a video on the project.
The solution researchers have arrived at is to restore reef habitat not by
resurrecting remnants of former reefs, but by building new ones. This kind of reef
restoration work is gaining traction in the Great Lakes and elsewhere.
Walleye decline and recovery strategies
The reef habitat restoration story in Saginaw Bay begins not with a project, but a
problem. Historically,
walleye were abundant in Saginaw Bay. But in the 1940s, this
f
ish population collapsed due to declines in water quality and habitat, caused by
pollution and sedimentation, along with unrestrained fishing .
The opportunity to recover walleye came after the
Clean Water Act took effect in
the early 1970s and the negative impacts were better managed around in the bay.
The DNR began stocking walleye, which boosted the population, but the fishery
didn’t recover to pre-1940s levels and remained dependent on stocking.
DNR researchers attributed
that to
degraded and
ongoing degradation of
spawning habitat (particularly
rock reefs, but also dams
blocking migrating fish), along
with walleye fry predation
from invasive alewives.
Then suddenly, something shifted.
“Along comes 2003, and we have this big food web change in Lake Huron and
invasive alewives disappear,” said Dr. David Fielder, fisheries research biologist with
the DNR and one of the authors of the report resulting from the research.
This change, due in part to increased predation on alewife by other fish, but mostly
by the invasion of dreissenid mussels – zebra and quagga mussels, which consume
3/11
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2/13/26, 1:51 AM
Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
much of the phytoplankton that are the base of the food chain – reduced the
number of alewives eating walleye fry.
This had a big effect, and reproductive success boomed. Stocking was discontinued
in 2006, and by 2009, walleye abundance reached recovery targets.
Even though walleye populations were seemingly back to normal, work remained to
be done.
Researchers noted that since rock reef habitat was lost in the bay, the walleye that
demonstrated sustained reproduction were primarily spawning in the tributary
rivers, among them the Saginaw River.
That’s not ideal, because it makes the walleye population vulnerable to changes in
those rivers, like barriers, contamination or natural disasters.
If the river spawning habitat isn’t available, the walleye will be unable to reproduce
with much success. According to Fielder, whether fish spawn in a river or on a reef is
something they likely inherit from their parents, not something they choose based
on environmental conditions.
Without preferred spawning habitat, walleye are left to deposit their eggs wherever
they can. In the case of the few reef-spawning walleye still hanging on in the bay,
this is often on the bottom of the lake.
But eggs on the bottom have a low chance of hatching out into fry, as the dissolved
oxygen they need to develop is low and they’re not hidden from the predators that
like to eat them. Plus, sediment can bury the eggs, just like it buried the former rock
reefs.
While restoration efforts won’t bring back all the rocky reefs once present in the
bay, restoring some of that habitat will still be immensely beneficial.
The metaphor project partners have used to describe this is the portfolio effect: Like
diversifying your investment portfolio can help you weather volatility in the market,
diversification of spawning habitat can help insulate the species from the effects of
big ecosystem changes.
The goal isn’t necessarily more walleye reproduction but more consistent or
dependable walleye reproduction. To ensure a resilient walleye population in
Saginaw Bay, walleye need various spawning habitats, both reef and river.
Lake whitefish spawning in Saginaw Bay
4/11
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Lake whitefish are an incredibly important species in the Great Lakes and Saginaw
Bay, ecologically and culturally, and they are the mainstay of the bay’s state-licensed
commercial fishery.
However,
lake whitefish
populations are in decline
across the Great Lakes,
including Lake Huron, and have
been for years – except for in
the central and lower half of
Lake Huron, which is
something of a stronghold for
the species. Researchers believe this is likely supported by Saginaw Bay, as it’s a
crucial spawning location.
While the ecological changes brought on by zebra and quagga mussels, in particular
the collapse of alewife, seemingly helped walleye populations, they have not had a
positive effect on lake whitefish.
These mussels’ voracious consumption of phytoplankton has devastated the
zooplankton and benthic macroinvertebrates – small marine animals – that not only
alewife but also whitefish fry depend on for early growth. Fry that don’t get enough
food grow slowly and fail to survive to older ages.
The proliferation of dreissenid mussels has had another effect on the lakes,
noticeable even to nonexperts: The water is much clearer. This is due, again, to their
feeding habits, pulling zooplankton and algae out of the water.
Clear water might seem pleasant, but it’s not good for native fishes like lake
whitefish. Additional UV light penetration of the water essentially gives lake
whitefish eggs and fry extreme sunburns, which reduce their survival.
This effect is magnified by the increase in mild winters as the climate changes. Less
ice coverage means even more UV light penetrating the water and harming
developing whitefish.
While managing invasive mussels and their impacts on spawning grounds is still
experimental (through efforts such as the
Great Lakes SWIM project), creating
suitable spawning habitats in productive areas like Saginaw Bay should still benefit
whitefish.
Whitefish also use reefs for spawning, so like walleye, restored reef habitat will
likely improve survival for eggs and fry. Coreyon Reef, an earlier offshore reef
5/11
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2/13/26, 1:51 AM
Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
project in Saginaw Bay, has already seen whitefish and walleye adoption for
spawning.
What about yellow perch?
Yellow perch are one of the most popular species among Great Lakes anglers, as
demonstrated by
DNR creel surveys, and for good reason. They’re a good fish for
beginners to target, and they’re fun to ice fish for, too.
But will efforts to bolster lake whitefish and walleye population resilience hurt
yellow perch populations, as many anglers fear?
“Perch are really important; we’re working hard to do what we can for perch
recovery in Saginaw Bay,” Fielder said.
Yellow perch today are at a fraction of their historical abundance in the bay. Yellow
perch spawning is strong, but the yearling perch currently have low survival rates.
This can be attributed largely to predation by larger fish, particularly walleye.
In the past, fisheries managers attempted to fix this by reducing the yellow perch
harvest limit, reducing commercial licenses targeting yellow perch and increasing
harvest opportunity for walleye.
None of these approaches improved perch survival.
Why? While walleye have reached
recovery targets, not all
ecological functions of the bay
are restored.
In the past, abundant pelagic
(midwater) prey fish
populations likely created a
predation buffer to allow for
better perch survival. Those used to be invasive alewife, and earlier, the native cisco
(lake herring). Both are absent now.
The Michigan DNR has
partnered with the U.S. Fish and Wildlife Service to
reintroduce cisco into Saginaw Bay to try to help restore that part of the fish
community, which could ultimately benefit yellow perch abundance.
The Walleye and Yellow Perch Recreational Management Plan for Saginaw
Bay, published by the DNR in 2025, focuses on finding balance between walleye
6/11
Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
and yellow perch in the bay. While walleye do prey on yellow perch, these species
can coexist at desired levels in the bay, and historically, they did.
Restoring reef habitat in the bay
“In that original 2004 plan, we prescribed a lot of different strategies for walleye
recovery,” Fielder said. “One of them was to invest in rock reef restoration in
Saginaw Bay.”
The plan called for two kinds of reefs, offshore and nearshore, with the intention of
seeing which type of reef would be most beneficial. But once initial benchmarks for
walleye recovery in Saginaw Bay had been met, there was little momentum (or
funding) to pursue reef restoration.
The result was
2019.
Coryeon Reef, an offshore reef in inner Saginaw Bay completed in
While a nearshore reef was also considered at the time, further engagement with
the local community was needed to find a site that would deliver the intended
nearshore habitat to native fishes without impeding use of the bay for boating.
The opportunity to pursue a nearshore reef came in the form of funding from the
National Coastal Resilience Fund (a partnership between the National Fish and
Wildlife Foundation and National Oceanic and Atmospheric Administration) for a
feasibility study on further restoration projects in Saginaw Bay.
Channel Island Reef was one of three projects included in the feasibility study, and it
was the one the partners decided to pursue at this time. The other possible
projects, focused on reducing sedimentation and attenuating wave action in flood
prone areas, may be considered for future restoration work in the bay.
Using what they’d learned from the feasibility study, public engagement efforts
headed up by Michigan Sea Grant and the implementation of Coryeon Reef a few
years prior, the team – including DNR, EGLE, GLFC, NOAA, Michigan Sea Grant, and
Environmental Consulting and Technology – set about constructing Channel Island
Reef to the east of Channel Island (also known as Spoils Island, Shelter Island or U.S.
Army Corps Confined Disposal Facility).
Construction began on Sept. 8, 2025, and was completed on Oct. 10, 2025.
The process for building the reef was straightforward: Pieces of limestone, quarried
locally in the Thumb area of Michigan, were moved out to the reef location on
barges. A crane, also on a barge, used a claw to pick up the stone cobble and drop it
into place.
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2/13/26, 1:51 AM
Gmail - Showcasing the DNR: Don’t put all your (fish) eggs in one basket
Channel Island Reef is about
2.5 acres, approximately 190
feet wide and 570 feet long.
The reef is located about 2
miles from the mouth of the
Saginaw River, a half mile east
of Channel Island. It is
underwater, sitting 5.5 feet
below the surface when water levels are lowest, which ensures that it poses a
minimal hazard to navigation.
Funding for construction of the reef came from several sources: the Great Lakes
Restoration Initiative, Great Lakes Fish and Wildlife Act, NOAA, and the
Natural
Resource Damage Assessment and restoration settlement with Dow Chemical.
NRDA funding helps restore ecosystem function and uses of public natural resources
that have been compromised by the release of hazardous substances into the
environment.
In addition to NRDA funds, grant funding is necessary for getting these kinds of
projects off the ground. In times when everyone is feeling the financial pinch, grants
allow the DNR and partners to accomplish large projects that would otherwise be
financially out of reach for the organizations on their own.
The entire reef construction process was funded through grants or settlement, not
by state tax dollars or license fee revenue.
‘We’re going to learn a ton’
What’s exciting about this project for researchers like Dr. Fielder is the learning
opportunity that it presents.
Before either reef was constructed, assessment projects were conducted in the area
to learn about the species that were using it and the predators that were present,
as well as the dissolved oxygen levels, water temperatures and other environmental
conditions. Similar assessments were conducted after the installation of Coreyon
Reef, for comparison.
“This before and after investigation really helps inform us on what we achieved with
this reef reconstruction,” Fielder said.
The assessments found that walleye and lake whitefish both adopted Coryeon Reef
for spawning almost immediately. The nearshore Channel Island Reef could have
similar results.
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“I'm excited for the completion of the Channel Island Reef construction. During my
PhD research at Purdue University in collaboration with DNR, we found lake
whitefish and walleye were already spawning on Coreyon Reef just a year after its
construction,” said Dr. Scott Koenigbauer, fisheries biologist with USFWS working
out of the Alpena Fish and Wildlife Conservation Office.
“We found both species were releasing more eggs at the Coreyon Reef site after its
restoration than before. We also observed a variety of species there, including
yellow perch, lake trout, burbot and cisco, during our surveys.”
Koenigbauer believes that future work will likely demonstrate that spawning reefs in
Saginaw Bay support stability for key species.
“With the construction of
Channel Island Reef, scientists
can now compare how these
species utilize nearshore and
offshore restored reefs in
Saginaw Bay,” he said.
Historically, we know that
there were both nearshore and
offshore reefs in the bay.
“The question is: Offshore, in the open water, will the fish find and use that reef, or
will they prefer a more nearshore environment?” Fielder said.
“Success in this rocky habitat requires lots of hydraulic agitation. That keeps the
water refreshed, oxygenated and clean of sediment. So, a nearshore reef that’s
shallower and has more wave agitation may perform differently – may perform
better – than the offshore Coryeon Reef.”
As with Coreyon Reef, Dr. Fielder and staff at the
Alpena Fisheries Research Station will be working with Purdue University to conduct assessments on the reef.
Starting in the spring, the researchers will start a two-year evaluation period,
monitoring the long-term effects of the reef. Some questions they’ll be investigating
are whether the fish are using the reef, whether they’re using it more or less than
Coryeon (which will also be evaluated during this period) and whether sediment or
dreissenid mussels are affecting the habitat.
Studying the reef could have implications for future projects – if Channel Island and
Coreyon Reefs are a success, there could be interest in more reef restoration work,
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While Saginaw Bay hasn’t always received the same attention as other parts of the
Great Lakes, that’s changing.
The area’s agriculture and industry have contributed significantly to the success of
the state’s economy, but current and historical land and water use practices
resulting from this hard work have degraded aquatic habitat.
So, while the bay has an excellent fishery, there’s room for improvement and
habitat restoration.
This opportunity for improvement has sparked interest in restoring and enhancing
the bay’s natural resources. Funding agencies are poised to invest in Saginaw Bay
and its watershed, and there’s no shortage of creative thinking when it comes to
habitat improvement efforts, from reef restoration to fish passage solutions to
stream barrier removal. Channel Island reef is one of many such projects on
Saginaw Bay’s recovery arc.
Reef-4: Construction on Channel Island Reef began on Sept. 8, 2025, and was
completed on Oct. 10, 2025. (Photo: Zak Allan, Great Lakes Fishery Commission)
Reef-5: Limestone cobble was built up to create a rock reef that sits 5.5 feet below
the surface when water levels are lowest. (Photo: Zak Allan, Great Lakes Fishery
Commission)
The Michigan Department of Natural Resources is committed to the conservation,
protection, management, use and enjoyment of the state's natural and cultural
resources for current and future generations. For more information, go to
Michigan.gov/DNR.