Lake Trout Recovering in Southern Lake Michigan, Face Challenges to the North

By Kevin Bunch, IJC

lake trout brimley
A lake trout fry being reared in the Pendills Creek National Fish Hatchery in Brimley, Michigan. Lake trout continue to be reared and stocked in the Great Lakes to restore the native top predator. Credit: US Fish and Wildlife Service/Katie Steiger-Meister

A study of lake trout stocked into Lake Michigan has found a wild population rising in the southern basin of the lake, but struggling in the north where sea lamprey predation and fishing pressure prevents most fish from living long enough to spawn.

The native top predator in four of the five Great Lakes, lake trout are important ecologically and as a game and sport fish. The lake trout – also known as siscowet, lake char, or mackinaw – inhabits cold, pristine, oxygen-rich waters and mature slowly. That slow growth rate led to a population crash in the mid-20th century, when overfishing and invasive sea lamprey predation ravaged the species. A change in the food web due to other invasive species also has impacted common food sources for lake trout. Fishing limits and sea lamprey control programs have helped reduce pressure on the species, however, and restoration efforts are paying off.

US Fish and Wildlife Service fish biologist Matt Kornis said lake trout have been stocked into Lake Michigan for decades in a bid to restore the species. Some of these fish were tagged with coded-wire tags at the hatchery beginning in the mid-1980s. Those tagged fish were stocked in four important spawning areas – one in the southern refuge, a cluster of reefs in the dead center of the lake; one in a northern refuge, a cluster of reefs in the northeast part of the lake; one at Julian’s Reef in offshore Illinois waters; and a nearshore shoal in Wisconsin waters called Clay Banks. The lake trout came from genetic remnant stocks from lakes Michigan and Superior alongside lake trout from New York’s Seneca Lake.

“Not only is the restoration timeframe (from the 1960s to now) long, but the spatial scale is very large,” said US Fish and Wildlife Service Senior Biologist Chuck Bronte. “We’re talking about one of the largest lakes in the world (fifth by area). That’s a big scale for trying to restore a keystone predator.”

In Lake Michigan, Kornis said the US Fish and Wildlife Service (USFWS), along with state and tribal partners, have been cooperatively sampling lake trout using gillnets every year since 1998 to analyze the recovery of tagged fish and get a better idea of survival rates and where they were found in relation to where they were stocked. They’ve found that the survival of stocked lake trout and positive growth in their population were heavily dependent on where the fish were stocked.

“The fish that were stocked in the northern refuge … had a substantially lower survival rate that we attribute to sea lamprey predation and fishing harvest,” Kornis said. “The downside is that there is poor survival in northern Lake Michigan, but the upside is we observed high survival of fish stocked in the southern basin, where we also saw more recent increases in wild recruitment (where fish spawn naturally).”

northern refuge lake michigan trout
The northern refuge of Lake Michigan, highlighted here, is one area where lake trout restoration efforts have hit a snag due to sea lamprey predation and harvesting by humans. Credit: University of Wisconsin-Madison

The problem in the northern refuge with sea lamprey stems in part from a failed dam on the Manistique River which allows sea lamprey access to a large, ideal system to spawn in. The Great Lakes Fishery Commission has been controlling sea lamprey populations in the Great Lakes by using lampricide in spawning habitats and physical barriers, but the Manistique system is not easy to treat with lampricide due to its size, making the dam a vital barrier to keeping lamprey from getting into the river system in the first place. Bronte said that dam will be replaced and upgraded within the next few years, shutting out sea lamprey from that spawning habitat that replenishes their numbers, in turn dramatically reducing their numbers in the area and helping lake trout in the northern refuge recover.

The trout harvesting is done primarily by Native American tribes exercising Great Lakes treaty fishing rights guaranteed under the 1836 Treaty of Washington, Bronte said, which are negotiated jointly by the tribes, the state of Michigan and the US Department of Interior as a consent decree. The current agreement was approved in 2000 and has seen minor revisions as circumstances change in the lakes; it runs until 2020.

Kornis said only a handful of older, mature lake trout were caught in the northern refuge, which means the fish don’t have a large enough parent population size to properly breed. A fecund population, he said, needs a high abundance of older fish from multiple age classes, something that’s been seen in southern sites over the past 10 years but not yet seen in the northern refuge.

“You can stock fish, but if they don’t survive to maturity that’s a problem,” Bronte said. “If you want lake trout restoration (to work) you’ve got to let them live longer and get to higher densities.” Lake trout take six to 10 years to become sexually mature.

All lake trout stocked everywhere in Lake Michigan – and not just those four reefs – started being tagged in 2010, but since lake trout take around five years to reach harvestable size and thus enter the fishery, those fish have yet to be included in the surveys, Kornis said.

Lake trout may be benefitting from Lake Michigan’s reduced alewife population too, as that invasive fish will prey on lake trout fry. Adult lake trout predation on alewives also can lead to deficiency of thiamine, a critical vitamin. Thiamine deficiency reduces the survival of the eggs and larvae of affected parents, Kornis said, an affliction known as “early mortality syndrome.”

Success stories in restoring lake trout to other Great Lakes, thanks to Canadian and US cooperation and planning, provide a sense of optimism for Lake Michigan. Binational programs to limit the harvest, control sea lamprey and stock the fish have been successful in Lakes Superior and Huron, according to Jolanta Kowalski, senior media relations officer at Ontario’s Ministry of Natural Resources and Forestry. Stocking was particularly important given how the fish was nearly wiped out in Lake Huron and had lost much of its adult population in Lake Superior when stocking began in the 1950s.

The lake trout population in Lake Huron is recovering well, Bronte said, with roughly half or more of the fish in the lake being entirely wild. While part of that is related to the alewife population collapsing, sea lamprey control efforts and a consent decree limiting the amount of lake trout that could be harvested also played a role in allowing the parental stocks to recover there. Bronte believes that same situation (low sea lamprey and fishing mortality) may be playing out in the southern end of Lake Michigan to some degree, but the recovery is still in the early stages and requires a low mortality rate to be successful.

Kowalski said Lake Huron still seems to have higher sea lamprey marking rates in the North Channel of Lake Huron than officials would like, suggesting there are still tributaries where the invasive species is reproducing with limited controls. Ontario still stocks lake trout in the Georgian Bay and the North Channel of Lake Huron, though the species has recovered enough in the lake’s main basin that it has ceased there.

Lake Superior’s lake trout population is fully restored and large scale binational stocking ended in the mid-1990s, Bronte added, providing hope that rehabilitation efforts can achieve similar success elsewhere.

restoration efforts trout
Restoration efforts have already helped adult lake trout rebound in Lake Huron and Lake Superior, and managers are hopeful the species can make a comeback across all of Lake Michigan over time. Credit: US Fish and Wildlife Service/Katie Steiger-Meister

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

Watermarks: Yearning for Water and Feeling Like a Kid Again

By Jeff Kart, IJC

With the recent release of the IJC’s First Triennial Assessment of Progress on Great Lakes Water Quality, it’s worth noting that high-level actions by governments have an impact at home, to people who live in the Great Lakes basin.

Residents have told us what they care about, including clean drinking water, access for recreation, fishing and beaches. But there are intangibles, too, like memories and emotions that help to shape generations and lives.

The watermarks below are some of more than 20 recorded by Lake Ontario Waterkeeper and the IJC at this year’s Healing Our Waters restoration conference in Buffalo, New York. They speak volumes on why the IJC and agencies in Canada and the US are important partners in protecting and restoring our shared waters.

David Hahn-Barker
David Hahn-Barker

David Hahn-Barker recalls the difference between plentiful beach access in Chicago and a lack of access in Buffalo. Buffalo was built in a way that blocked the lakefront from the people, “one of the sadder things about our community,” he says. But areas like Canalside have become an attraction in Buffalo, helping to satisfy “a yearning for water.”

Leann Sestak
Leann Sestak

Leann Sestak of Erie, Pennsylvania, remembers childhood visits to a gorge with her cousins, and spending afternoons looking for toads, frogs and other tiny creatures. The area she used to visit has since been developed, but it’s also connected to a trail that allows more people to enjoy a natural area.


Kathleen Blackburn
Kathleen Blackburn

Kathleen Blackburn, originally from Texas, now lives in Chicago and recalls stepping for the first time into Lake Michigan earlier this year. “I was struck by how clear the water was, by kind of how bracingly cold and refreshing it was. I felt both like suddenly aware of my body and kind of lost in the experience, too. But I also felt kind of like a kid again.”

Es Jiminez
Es Jiminez

Es Jiminez of New York recalls traveling the world in the military and seeing how people were suffering for clean drinking water. Jiminez feels more connected to the land and its water by working with People United for Sustainable Housing.

“It’s helped me heal within from all the issues that I have from the military and I love doing what I do. I feel like we need to be out there helping protect our water as much as we can. Whether you’re canoeing or whether you’re just like just walking down by the waterway, just make sure you go out there and enjoy it. It’s just very powerful to be able to talk to the water and actually see the work that I’ve done …”

Jeff Kart is executive editor of the IJC’s monthly Great Lakes Connection and quarterly Water Matters newsletters.



Invasive Species Are Changing Lake Trout Diets


By Kevin Bunch, IJC

usgs kato lake ontario trout
A lake trout in Lake Ontario is pulled to the US Geological Survey Research Vessel Kato. Credit: Nicole Saavedra

Invasive zebra and quagga mussels from the Ponto-Caspian region of Europe began to drastically change the ecosystem of the Great Lakes starting in the late 1980s. Scientists wondered how lake trout would adapt. In Lakes Michigan and Ontario, they’ve found that trout are finding meals by going after invasive fish like the round goby.

Invading species changed the food web of the lakes by eating plankton species and drawing nutrients closer to the nearshore and benthic (the lowest part of the water column) regions, reducing their availability to native fish and zooplankton species. In recent decades, scientists have studied the long-term effects on native species, said Nicole Saavedra, a masters student at the State University of New York’s College of Environmental Science and Forestry who works on lake trout in Lake Ontario.

“On the Ponto-Caspian species invasion, it’s not necessarily all doom-and-gloom,” Saavedra said. “While it has changed things in the lake, specifically species like round goby have provided a food source for lake trout as well as other predatory consumers.”

Lake Ontario

Lake trout are the top native predator in the Great Lakes, living long lives and hunting a mix of prey species as they grow. Historically, Lake Ontario trout consumed benthic macrointervebrates called Diporeia and sculpins as juveniles, moving over to rainbow smelt, cisco, alewives and other species as adults, Saavedra said. Since the Ponto-Caspian invasion, juvenile lake trout are primarily eating opossum shrimp, or Mysis, while adults are leaning more heavily on alewives and round goby. Lake trout are still growing to lengths researchers have seen historically, she said, but don’t seem to be as fatty or “lipid rich,” which might suggest a link on how they’re acquiring or using energy.

Given that lake trout are a popular fish for anglers and Canadian and US government agencies have been trying to restore their depleted numbers for decades, it’s important to know what their food supply looks like today. Simply looking at what’s in their stomachs only provides a look at a couple days of meals, but pollutants like polychlorinated biphenyls (PCBs) that bind with fat and lipid tissue in the lake trout can help provide a long-term glimpse into the trout’s diet – especially since data goes back to 1977.

The Ontario Ministry of Natural Resources (MNR) Lake Ontario Management Unit has been studying the lake trout population in Lake Ontario’s Canadian waters since 1996 (prior to that point, the trout were monitored binationally in a netting program). According to a 2016 Great Lakes Fishery Commission report released in March, lake trout numbers declined in the lake in the early 1990s following the invasion and reached their nadir in 2005. Since then, more have been gradually caught, albeit numbers are still below the ideal. The Ministry found that alewife is the most consumed food by weight.

Another insight from this research: Saavedra said her colleagues at the USGS survey station in Oswego have found a recent increase in natural reproduction of lake trout, which could be a positive trend for the species and related to the changes in the food web (with younger adult lake trout using round goby as prey).

Saavedra said her study is ongoing and she expects to be finished with her research by the spring of 2018.

Lake Michigan

stomach contents lake michigan undergrads
Undergrads check the stomach contents of salmonid species from Lake Michigan. Credit: Austin Happel

Similar work is going on in Lake Michigan, where researchers are investigating the diets of salmonid species – lake trout, Chinook salmon, brown trout, coho salmon and steelhead trout – caught by anglers throughout the lake. Austin Happel, a freshwater ecologist with the Illinois Natural History Survey, said that over 2015 and 2016 they took fish collected from anglers by the US Fish and Wildlife Service’s Great Lakes Mass Marking Program and checked their stomach contents to see what they’d eaten most recently.

They found that round goby are making up a larger share of lake trout diets in Lake Michigan, following a seasonal pattern: goby-heavy diets in the spring and fall when waters are cooler, with more alewives in the summer.

Additionally, like in Lake Ontario, Happel said information from US Fish and Wildlife Service suggests that lake trout seem to be increasing their natural reproduction in Lake Michigan in the southern basin, where high survival of stocked fish has increased parental stock size.

Natural Reproduction

Matthew Kornis, fish biologist with the US Fish and Wildlife Service, said brown trout and lake trout have adjusted to declining populations of preyfish like alewife, sculpin and bloater by hunting and eating other fish, notably the round goby. Pacific salmon are still primarily hunting alewives year-round, and while steelhead salmon are eating more invertebrates, their diets are still alewife-dominated.

“Whether that can be attributed to goby or something else in the food web is still debated quite a bit, but it seems like as alewives are having problems while gobies are expanding. These changes (to the prey base) are coinciding with increases in natural production that is having an effect on the ability of these (salmonids) to reproduce,” Happel said.

Happel said that coincidentally as the round goby population expanded and the alewife population decreased around 2005-2006, Chinook salmon also showed increased signs of natural reproduction, despite not eating gobies. That stable period that lasted until 2013, when Chinook wild reproduction dropped slightly. He said researchers are still trying to determine if any of those prey shifts may have played a role in the increase in wild Chinook spawning.

usfws staff muscle tissue
U.S. Fish and Wildlife staff prepare muscle tissue specimens for stable isotope analysis.  Credit: Matthew Kornis

Using Isotopes

Researchers studying salmonid diets through stable isotopes are reporting similar results. Kornis said researchers track these non-radioactive variations of carbon and nitrogen as they move through the food web. Stable isotopes from prey can remain in a trout or salmon for up to a year before being fully absorbed into the animal’s tissue, and thus stable isotopes offer a picture of diet over a longer time frame compared to the snapshots provided by evaluating stomach contents. Kornis said they then also can chart what kind of overlap there is on prey among the Pacific salmon species (Chinook salmon, coho salmon, and steelhead), brown trout and lake trout.

“It’s led us to conclude that the competition for the remaining pelagic forage like alewife will be greatest among the Pacific salmon, whereas the trout species are diversifying their diet in response to the prey availability,” Kornis said. He added that this suggests that continued stocking and trout recovery efforts are worth pursuing, as the fish will continue to adjust as the forage base changes.

Since this study targeted only fish that were caught by anglers, Happel said it could be skewing the results to favor certain prey species, such as terrestrial insects for steelhead, lake trout caught in the water column (vs. on bottom) having more alewife, or the stomachs from fish caught closer to shore having more round goby. He said the researchers are looking into whether offshore gillnetting would change the results significantly. Round gobies tend to show up where invasive mussels are, as they are one of the few species in the Great Lakes that preys on the zebra and quagga mussels particularly prevalent in southwestern Lake Michigan near Waukegan – coincidentally the area where lake trout are naturally reproducing most successfully. Conversely, the mussels’ filter feeding on plankton seems to hurt alewives and other preyfish that would otherwise be using those food sources, either directly or indirectly, Happel said.

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

How Do Mussels and Nutrient Runoff Impact Lake Michigan’s Food Web?

By Kevin Bunch, IJC

quagga mussels
Quagga mussels have effectively displaced their fellow invasive species the zebra mussel throughout the Great Lakes, and can survive in cooler, deeper water than their counterparts. Credit: US Geological Survey

Scientists have known since the 1972 Great Lakes Water Quality Agreement that nutrient runoff from fertilizer and wastewater is responsible for harmful algal blooms. They’re also aware that invasive quagga mussels are to blame for changes in how nutrients move around the lakes and its food web. Now a recent modeling study has better defined the role quagga mussels play in the use and movement of nutrients within Lake Michigan, which could assist efforts to reduce blooms throughout the Great Lakes.

Quagga mussels are a dreissenid species native to the Ponto-Caspian region of eastern Europe that most likely entered the lakes through ballast water in the 1980s. The tiny creatures form hard shells and latch onto practically any hard surface before filter feeding out plankton in the water column. The mussels thrive in nearshore regions, with quagga mussels outcompeting their fellow invasive zebra mussels in many areas. Quagga mussels also are capable of surviving in deeper water than zebra mussels, pushing the invasion further offshore.

Lake Michigan has seen a decline in offshore primary productivity – essentially the rate of how organisms at the base of the food web convert sunlight and nutrients into biomass energy – for around the past decade, according to Darren Pilcher, research scientist with the Joint Institute for the Study of the Atmosphere and Ocean at the US National Oceanic and Atmospheric Administration’s Pacific Marine Environmental Laboratory. Since these phytoplankton species are eaten by a wide variety of other creatures, including invertebrates and eventually fish, understanding what’s driving that decline is important, he said. There are two major drivers that have been suggested: the decline of nutrient pollution into the lake from runoff since the GLWQA went into force and the growth of the quagga mussel population.

“These mussels are able to just graze and eat the phytoplankton as they grow, and that’s one mechanism showing how productivity has been reduced in the lake,” Pilcher said.

The model Pilcher and his partners built shows representations of the lake’s productivity under different conditions. Researchers can see what the lake would look like with a reduced number of mussels, or with a reduced amount of nutrient runoff (based on the observed decline going back to before the mussels invaded). This allows them to tease out the effect of each process. The model accounts for how water moves throughout the lake and for its ecosystem, particularly phytoplankton and zooplankton – organisms that eat phytoplankton.

Pilcher said they found that the growth of the quagga mussel population and drops in total nutrient runoff have impacted the lake, but at different times and places. Quagga mussels have the biggest impact in the spring and late autumn due to how the water moves within the lake, Pilcher said. The mussels live at the bottom of the lake, while phytoplankton tend to live in the upper layers to soak in the sun’s rays. During spring and late autumn those water layers tend to mix, bringing those plankton down to where the mussels can eat them. In the summer, the water layers stratify and rarely mix, denying quagga mussels that food source outside of the nearshore zone where waters are shallower. The researchers had hypothesized that would be the case, and with the modeling they were able to see how the quagga mussel’s seasonal dependence worked.

“The phytoplankton sit in the top layer (of water) and no mussels are grazing on them, so they’re able to continue as business as usual at that point,” Pilcher said.

Cladophora algae mats have surged in nearshore areas where phytoplankton isn’t available to use phosphorus runoff as a nutrient source into the Great Lakes. Credit: Wisconsin Sea Grant

However, since mussels in shallower nearshore zones can continue to feed on phytoplankton, they’re clarifying the water and leaving a niche for other algae and bacterial species to move in and use the phosphorus there to grow and expand into blooms. This also has the effect of shuffling nutrients predominantly to the nearshore zone and processing them into a more bioavailable form, in what’s called the nearshore nutrient shunt. Runoff can exacerbate that, and as a result the impact of the runoff is mostly seen in the summer, when harmful algal blooms can grow and species like Cladophora, a kind of algae that lives on the lake bottom, can spread into large mats.

Since those nutrients aren’t making it into the offshore zones in the first place, species in the deep water zones are still out of luck. Pilcher said that some fish in nearshore zones still can conceivably eat algae or the mussels, but those in the offshore regions have a harder time finding food unless they’re willing and able to venture closer to shore. This has been thought to be contributing to the population declines of several fish species in the Great Lakes, such as lake whitefish, as they struggle to find food where they live.

In the future, Pilcher said they’d like to see benthic algae such as Cladophora added to the models to better understand how the mussels are affecting their growth. With the mussels clearing out more desirable phytoplankton in nearshore regions, phosphorus is going unused by those species, giving undesirable algae and bacteria an opening to grow. This information could be helpful as the Great Lakes states and Ontario work on reducing phosphorus loading into the Great Lakes, particularly Lake Erie, by helping refine phosphorus loading targets and expectations. Pilcher added that models using similar parameters could be developed for the other four Great Lakes; they already exist to some degree for Lake Erie.

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

Sea Lamprey: The Greatest Invasive Control Success Story

By Kevin Bunch, IJC

sea lamprey
Sea lampreys are among the oldest invaders of the Great Lakes. Credit: C. Krueger, GLFC

An invader in a massive freshwater basin. An uncountable number of spawning grounds. A fishery on the brink. A desperate search for a solution that ended up becoming the most successful aquatic invasive species control team effort in American and Canadian history. It’s not a movie, but rather the true tale of the sea lamprey’s invasion of the Great Lakes.

The sea lamprey is parasitic fish native to the Atlantic Ocean. As an adult, it latches onto other fish with its suction cup-like mouth, using a rasping tongue to cut into its victim to suck out bodily fluids and blood. In the Atlantic it doesn’t typically kill its hosts, but the fish in the Great Lakes have no such luck. It’s estimated that a single lamprey can destroy an average of 18 kilograms (39 pounds) of fish in its parasitic lifetime, with only about one in seven fish surviving a lamprey attack. It’s not to be confused with native lamprey, which are smaller and have different coloration, and don’t usually kill the host fish.

Sea lampreys were first detected in Lake Ontario in 1835. While there has been discussion on whether it is native to Lake Ontario, it most likely is an invasive species that entered through the Erie Canal, according to Marc Gaden, communications director for the Great Lakes Fishery Commission (GLFC), a binational organization funded by the Canadian and US governments. The 1919 reconstruction of the Welland Canal, which bypasses Niagara Falls to connect Lake Ontario to Lake Erie, likely allowed the sea lamprey to enter Lake Erie and on to the rest of the basin. They were discovered in Lake Erie in 1921, Lake Michigan in 1936, Lake Huron in 1937 and Lake Superior in 1939. The sea lamprey found an immense number of tributaries featuring the combination of rocky nesting grounds to lay eggs and silt for larval lampreys to grow in, making the Great Lakes a lamprey Eden. In its native habitat, the sea lamprey spends most of its life in saltwater, making it the rare species that has adapted to living entirely in freshwater systems like the Great Lakes, similar to the Pacific salmon species introduced to control invasive alewives.

lake trout lamprey
A Lake Trout caught in Lake Huron with a sea lamprey attached. Credit: Marc Gaden, GLFC

The impact on the Great Lakes fishery was devastating. Prior to the invasion, about 20 million pounds or about 9 million kilograms of fish were harvested commercially each year in the upper Great Lakes – Superior, Huron and Michigan. By the 1960s that amount was reduced to about 300,000 pounds (136,077 kg) per year, while sea lamprey were killing close to 100 million pounds (45.4 million kg) of fish each year, and 85 percent of the remaining fish were scarred with lamprey attack wounds.

“Commercial fishermen and fishery managers first realized they had a problem around 1940, when it became clear what was happening to the Huron-Michigan fisheries from lamprey,” Gaden said. “That’s when the managers and scientists went into high gear and started seeking control measures.”

With little experience with aquatic invasive species, a wide variety of control methods were attempted. These methods included physical barriers to keep lamprey from entering the streams they use to spawn, crude electrical barriers to block their advances and sieves to stop larvae from eventually entering the Great Lakes from those inland streams. Entrepreneurs tried to make sea lamprey a commercially fished species for human consumption, but none of these attempts worked in stopping the sea lamprey.

The breakthrough came after years of searching for a chemical compound that would kill sea lamprey and not harm other organisms. A compound called TFM was discovered and field-tested in 1957, and entered management usage in 1958 through the binational GLFC. It has been used to great success.

The lampricide targets larval sea lampreys living in streams. After hatching from eggs found upstream in rocky areas, larvae make their way to silty areas and burrow into the substrate until they emerge as adults. The lampricide kills them in that weak, larval state by disrupting their metabolism before they can ever grow up to become the top predator in the Great Lakes. After decades of use, Gaden said the sea lamprey population in the Great Lakes has been reduced by about 90-95 percent from their peak in the late 1950s, and dropped the amount of fish killed by the lamprey to about 10 million pounds (4.5 million kg) a year. While it also affects native lamprey species, sea lamprey larvae tend to live and spawn in different areas from the native species; fishery managers focus on those stream areas where sea lamprey larvae burrow to minimize the impact on native species.

Dead sea lamprey larvae washed up on the shore of the Manistee River after a successful lampricide treatment. Credit: R. McDaniels, GLFC

Lampricide isn’t the only tool used to control lamprey numbers, Gaden said, as good pest control takes multiple tacks. Physical barriers are still in use to deny lampreys a path to their preferred spawning grounds. And if those lampreys can’t reach a place to spawn, there’s no need use lampricide treatments, which is expensive and time-consuming. The GLFC also deploys traps to catch lamprey entering or leaving the streams to remove them from the system, and has tested sterilizing male lamprey in the St. Marys River to try and overwhelm the number of fertile males. Most recently, Gaden said the GLFC “is on the cusp” of using isolated lamprey pheromones to affect their behavior – drawing lamprey away from ideal spawning locations and toward traps.

“We’re working on unlocking their genome,” Gaden said. “There are things within the lamprey genome we can exploit, like create conditions so they only produce males, but that’s further into the future.”

Mark Burrows, physical scientist and project manager in the IJC’s Great Lakes Regional Office, said the GFLC has sponsored important research devoted to controlling and eradicating sea lampreys while protecting native species, much of which was highlighted at the recent International Association for Great Lakes Research conference in Detroit.

“They deserve a lot of praise for the progress they have made in combatting this destructive invasive species, and I look forward to the GLFC forging another 10-fold decrease in lamprey numbers at some point in the future,” Burrows said.

While a focused and targeted approach to invasive species can work in smaller inland lakes, the size of the Great Lakes makes controlling aquatic invaders difficult. That they invaded a waterway that also serves as a border between Canada and the United States added an additional wrinkle. It meant both countries needed to work together, even though fishery management is primarily the domain of state, province, tribal and First Nation governments. This team effort has kept sea lamprey from completely dominating the ecosystem of the Great Lakes for decades.

lamprey traps
Sea lamprey traps are being tested in the field, set up in the Ocqueoc River in Michigan. Credit: T. Lawrence, GLFC

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.


Invasive Mussels Turning Central Lakes into a Food Desert

By Kevin Bunch, IJC

invasive mussels nutrients
Invasive mussels have caused nutrients such as phosphorus in the Great Lakes to clump closer to the shorelines. Coupled with mussels’ tendency to clarify water, this has led to an expansion of the algae Cladophora. Credit: USGS

Invasive zebra and quagga mussels are taking nutrients that would otherwise be in deeper waters and shunting them closer to the shore, which could make it more difficult to halt harmful algal blooms.

Known as the “nearshore nutrient shunt,” this migration of phosphorus and other nutrients used as food by plankton has led to some severe negative impacts in the existing Great Lakes food web. Algae, particularly Cladophora which grows on the hard surfaces near the mussels and feeds on the nutrients the mussels excrete, are thriving in those nearshore regions where nutrients are stockpiling.

The shift in nutrient locations also has benefitted other species that prefer nearshore and benthic – or lake floor – environments, according to Dr. Harvey Bootsma, associate professor in the School of Freshwater Sciences at the University of Wisconsin-Milwaukee.

Historically, a greater chunk of phosphorus entering the lakes has found its way offshore, where it serves as food to phytoplankton. Those in turn are eaten by zooplankton, and fish can feed on both types of plankton, as well as other aquatic species that eat them. Some phosphorus ends up finding its way into the benthic level, periodically getting kicked back up dissolved into the water, where it can continue to serve as fertilizer for phytoplankton.

With invasive mussels, more phosphorus is staying in the nearshore environment, cycling through and never making it into deeper waters. Nearshore currents also tend to keep dissolved phosphorus in the water column, where Cladophora gets the first crack at this food supply. Coupled with the mussels’ voracious appetites clarifying the water column, this can lead to greater harmful algal growth, resulting in the blooms seen on Lake Erie and in bays throughout the Great Lakes. The mussels also are capable of scavenging offshore plankton as it drifts into the nearshore zone, ultimately retaining the nutrients from the plankton in the mussels’ nearshore home.

zebra quagga mussels
The zebra mussel, left, and quagga mussel, right, are a pair of invasive species originally from Europe that have dramatically altered the Great Lakes food web. Credit: NOAA

The impact this has had on the food web is significant. Some species of fish that historically have lived offshore or in the water column are willing to enter nearshore or benthic regions for food. Round goby, an invasive fish that feeds on the mussels and other invertebrates, has a ready food source in the nearshore region. This has led to some native predatory fish, like the brown trout, steelhead trout and Atlantic salmon, venturing into the nearshore areas to feed on the gobies. Other species, such as Chinook salmon and coho salmon, don’t feed on round gobies and aren’t making that move into the nearshore. Instead, their food supply is declining as the offshore plankton production is limited by the mussels, and their populations are suffering.

The expanded Cladophora mats could be causing other problems too. Bootsma said studies have shown Cladophora can harbor higher concentrations of bacteria as it decomposes on beaches. In northern Lake Michigan there have been an increasing number of birds killed by avian botulism. Bootsma said there is evidence suggesting the Cladophora could be promoting growth of the bacteria that cause botulism. When round gobies end up eating the toxic bacteria and in turn get eaten by birds, the birds get sick and die.

This nutrient shunt has led researchers to conclude that more stringent controls on the amount of phosphorus and other nutrients making it into the Great Lakes are needed to improve water quality. While mussels are the primary culprit behind the resurgence of Cladophora, on Lake Erie it’s believed this is why harmful algal blooms and other water quality issues associated with excessive nutrients rebounded in the 1990s, despite existing regulations of phosphorus and other nutrients, and have continued to plague the lake in the decades since.

The United States and Canada have agreed to reduce phosphorus entering Lake Erie by 40 percent of 2008 runoff amounts, though neither government has unveiled its plan yet. Bootsma said based on historical data and numerical models, that reduction amount should be enough to reduce the problems of toxic algae and deep-water hypoxia – the formation of oxygen-deprived zones in the water – to acceptable levels. The IJC recommended similar reduction amounts in a 2014 report released as part of the Lake Erie Ecosystem Priority.

While reduced phosphorus loading may help to address phytoplankton blooms in Lake Erie, Bootsma said there’s still uncertainty as to how nearshore Cladophora growth will respond to a reduction in phosphorus entering the water. Lake Michigan, with its lower phosphorus concentration compared to Lake Erie, still has problems with the nearshore algae. This is leading scientists to question whether localized phosphorus reductions will impede Cladophora growth or if phosphorus concentrations in the entire lake need to come down first. Lower phosphorus concentrations in the offshore areas could further reduce the amount of plankton in those areas, hurting the food web in those areas even more than the mussels already have.

“What we need now is models, based on solid research, that tell us how both the offshore and the nearshore zones will respond to changes in phosphorus loading,” Bootsma said.

Great Lakes Water Levels Expected to Stay Above Long-Term Average

(See also: “Extreme Conditions and Challenges During High Water Levels on Lake Ontario and the St. Lawrence River“)

By Kevin Bunch, IJC

chicago coastline lake michigan
Extremely high water levels can cause erosion and increase flood risks in coastal areas, such as along the Chicago coastline off Lake Michigan. Levels are not expected to be high enough to significantly increase those risks in the coming months, however. Credit: L.S. Gerstner

Water levels on the Great Lakes are likely to remain above the long-term average through the spring and summer, according to forecasts assembled by the US National Oceanic and Atmospheric Administration, Fisheries and Oceans Canada, Environment and Climate Change Canada and the US Army Corps of Engineers. But none of the Great Lakes are expected to reach record high water levels set mostly in the 1980s or 1950s.

While each lake is unique, they all tend to follow a similar cycle based on seasonal changes. Water levels typically reach their seasonal low during the winter months before increasing in the spring due to snowmelt and precipitation. Water levels tend to peak during the summer months, before beginning to drop in the fall and early winter.

There are three main factors that impact lake water levels, said Drew Gronewold, physical scientist with NOAA’s Great Lakes Environmental Research Laboratory: the precipitation over the lakes, evaporation of water on the lakes into vapor, and the runoff that comes into the lakes.

These variables, in turn, are affected by changes in air and water temperatures. For example, Gronewold said the timing of big runoff pulses is dependent on the amount of snow building up in the winter months and when it melts in the spring.

A water level decline in the fall is generally driven by evaporation, as air temperatures drop while surface water temperatures are still relatively warm. While water temperatures were relatively warm during the fall and winter months of 2016-2017 – leading to a lack of ice cover – evaporation amounts have been typical for this time of year due to a relatively mild winter air temperatures, Gronewold said.

These recent conditions, coupled with historical data, lead agencies to expect the water level rise to remain fairly typical this spring and into the summer. As water levels are already above their long-term average for this time of year, researchers expect that they’ll remain above average in the coming months, Gronewold explained.

There is still plenty of uncertainty, he added, as the amount of snow on the ground is less than it has been in some recent winters. It’s also difficult to predict continental-wide meteorological and climate patterns that impact Great Lakes weather patterns and temperatures. These can range from an El Niño effect like the one seen in the winter of 2015-2016 or a “polar vortex” that hit the region in the winters of 2013-2014 and 2014-2015. This uncertainty is expressed as a range of possible water levels in the forecasts released by the US Army Corps and Fisheries and Oceans Canada.

Great Lakes water levels also can be influenced by human management. Hydropower plants and a gated dam on the St. Marys River are used to manage outflows from Lake Superior into Lake Michigan-Huron, while a hydropower plant on the St. Lawrence River is used to manage outflows from Lake Ontario. Outflows through these structures are managed binationally by boards and according to orders and criteria established by the IJC. Nonetheless, the control of water flows through these lakes is limited, and weather conditions and water supplies remain the most significant factor affecting water levels.

Water levels are measured based on the International Great Lakes Datum, defined as the height above sea level at Rimouski Quebec on the St. Lawrence River. Agencies have been measuring lake levels since the 1860s, with more reliable levels going back as far as 1918. They base the lakes’ long-term average water levels on that information.

“We expect a range of water level conditions depending on water supplies,” said Jacob Bruxer, senior water resources engineer with Environment and Climate Change Canada. “There’s a lot of variability and uncertainty in weather and water supply forecasts, particularly when looking beyond a few weeks’ time, so we don’t try to forecast any specific trends and instead consider a full range of water supply scenarios that could be expected.”

According to recent forecasts, through September 2017 Lake Superior is likely to remain at or above seasonal averages, with a small chance of falling below its long-term average in July. There is less uncertainty for the spring months; water levels were about 5.5 inches (0.14 meters) above the long-term average by the end of March, and by May that range could be between 2.7 inches to 10 inches above the average (0.07 meters to 0.27 meters). By September, water levels could be as high as 1 foot (0.3 meters) above the long-term monthly average for Superior.

low water levels grand traverse bay
Low water levels can limit boat access to the water – as seen with these docks off Grand Traverse Bay in Michigan – and cause shipping problems in the Great Lakes. Credit: Michigan Sea Grant

Lake Michigan-Huron, considered as one lake hydrologically, was about 9.4 inches (0.24 meters) above the March long-term average by the end of the month. By September, Michigan-Huron is expected to remain above the long-term average, in a range of 1-16 inches (0.02-0.4 meters). Gronewold said Michigan-Huron saw water levels fall slightly more during the fall months of 2016 than is typical, but that is unlikely to make a discernible difference during this spring and summer.

Higher-than-average water levels are anticipated on Lake Erie, which has seen water levels on the rise in recent months, reaching more than 17 inches (0.44 meters) above the long-term average by the end of March. Water levels are expected to continue to remain above average this spring, before starting to fall around June to a range of 3.9-16 inches above average (0.10-0.41 meters).

Lake Ontario has a slight chance of being just barely below its long-term average going into summer, but will more likely be above it by up to 15 inches (0.38 meters). The forecasted peak is in May, when water levels could be 3.9-21 inches above average (0.10-0.55 meters). Water levels are then expected to fall at about the same degree as they usually do, according to the long-term average.

The US Army Corps publishes 12-month forecasts for Lakes Erie, Huron-Michigan and Superior, as well as Lake St. Clair, based on current conditions and similar historical weather data. Uncertainty grows substantially more than six months out, but most outcomes for Lakes Erie and Michigan-Huron suggest a greater likelihood of continued higher-than-average water levels through the year. Lake Superior also has a better chance of higher-than-average water levels, but faces a substantial possibility of being below that long-term average, too.

(See also: “Extreme Conditions and Challenges During High Water Levels on Lake Ontario and the St. Lawrence River“)

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.

Finding Inspiration on ‘Big Water’

By IJC staff

Great Lakes Watermarks are about inspiration. The two latest examples come from Katherine O’Reilly and John Kennedy.

O’Reilly, a graduate student at Notre Dame, talks about growing up near Lake Erie, “pea green water” and how she was moved to study coastal wetlands and their role in improving water quality.

Kennedy, of Green Bay, Wisconsin, says his interest in “big water” started as a child, on Lake Michigan. He’s spent decades working to solve water quality problems in Green Bay.

The IJC’s Great Lakes Watermark Project includes these and other watermarks in partnership with Lake Ontario Waterkeeper. We’ve been gathering and sharing stories about the freshwater seas since last year.

See a special Watermark Project website for more, including how to submit your own.

Scientific Institute of the Month: School of Freshwater Sciences

By Jeff Kart

The School of Freshwater Sciences at the University of Wisconsin-Milwaukee prides itself as the only graduate school in the North America solely dedicated to freshwater issues. For 50 years, it’s maintained the largest water-focused academic research institute on the Great Lakes.

“What sets us apart from your average school is that we tackle water from an interdisciplinary perspective,” says Eric Leaf, assistant dean for advancement. That means integrating a wide variety of scientific disciplines, as well as engineering, urban planning, policy and public health. “The networks of inputs (to the Great Lakes) is so complex that you need every discipline to understand it.”

Emily Tyner, a graduate student in the School of Freshwater Sciences, dives while working with the National Park Service to study benthic oxygen dynamics at Sleeping Bear Dunes National Lakeshore and how they may trigger avian botulism outbreaks. Credit: Harvey Bootsma/University of Wisconsin-Milwaukee
Emily Tyner, a graduate student in the School of Freshwater Sciences, dives while working with the National Park Service to study benthic oxygen dynamics at Sleeping Bear Dunes National Lakeshore and how they may trigger avian botulism outbreaks. Credit: Harvey Bootsma/University of Wisconsin-Milwaukee

The school is located in Milwaukee’s urban harbor near the shores of Lake Michigan, giving researchers and students a unique vantage point.

“It’s everything about our culture,” Leaf said. “We can walk out the back door, get on a boat and go do research.”

The Neeskay in the Milwaukee River. Credit: Troye Fox/University of Wisconsin-Milwaukee
The Neeskay in the Milwaukee River. Credit: Troye Fox/University of Wisconsin-Milwaukee

The school focuses on four areas: Ecosystem dynamics with an emphasis on large lakes, human and ecosystem health, water policy, and water technology. Overall, there are 120 people in the organization, including 20 faculty and senior scientists and 60 master’s and Ph.D. students. In addition, the school maintains close ties to water-focused groups in engineering, geosciences, atmospheric sciences, architecture, and urban planning at the University of Wisconsin-Milwaukee.

“Student success, research excellence and university engagement are the main themes of UWM,” Leaf said. “At the school I can’t separate those things. The students are working on real research projects that affect the community.”

The School of Freshwater Sciences was founded on the idea that policy decisions that affect the lakes should be driven by science. “That’s what our students are learning,” Leaf said, “how they as scientists can affect policy, how to communicate science and how to communicate with decision makers.”

The school operates a research vessel called the Neeskay — a named derived from a Ho-Chunk Native American word that means “pure, clean water.” Leaders are in the early stages of planning and fundraising for a next-generation ship that will operate as a research vessel and floating classroom.

See also: Milwaukee to Host Second Public Meeting on Progress to Restore Great Lakes

Students from the school conducting research on Lake Michigan aboard the Neeskay. Credit: Peter Jakubowksi/University of Wisconsin-Milwaukee
Students from the school conducting research on Lake Michigan aboard the Neeskay. Credit: Peter Jakubowksi/University of Wisconsin-Milwaukee

Since the Great Lakes are a shared resource with Canada, collaboration with agencies in that country also are routine — and valuable, says Associate Professor Harvey Bootsma.

Bootsma grew up in Canada and studied at the University of Manitoba and the University of Guelph. He conducts nearshore work related to problems like Cladophora, a type of algae that grows to nuisance levels, and invasive species like zebra and quagga mussels.

He says working with colleagues at the University of Waterloo has been especially helpful. Workshops between the Milwaukee school and the Ontario university have allowed scientists to compare notes and helped jumpstart several areas of research.

“We have similar problems in a number of the Great Lakes, especially nearshore issues,” Bootsma said. “It’s really beneficial for groups of scientists from different lakes to get together.”

What is the school trying to discover?

“It’s more of a lab-by-lab thing,” Leaf says. “From a broad perspective, the school wants to investigate how the Great Lakes and other water systems function—and how we as humans impact them—so that decision makers and managers can make informed decisions to manage our most precious water resources.”

That includes work such as developing a model of nutrient contamination to help water managers reduce the size and duration of “dead zones” in Green Bay.

“We do a tremendous amount of work collaborating with the community in southeast Wisconsin and around the Great Lakes,” Leaf said. “That’s one of the points we take pride in: Our work is not theoretical, it is applied science.”

Leaf notes a movement in Milwaukee to revitalize its inner harbor. The school recently received a grant to conduct an extensive aquatic survey of the harbor.

“In addition to revitalizing land use of the harbor and making it a stronger part of the community, (organizers) want a harbor that’s environmentally clean, that supports recreational fishing, that supports birds and wildlife, that becomes a natural refuge in the city,” he said.

School researchers are working with partners including the Harbor District Inc. and the Wisconsin Department of Natural Resources to assess existing fish forage and spawning habitat and develop a map to inform strategic development.

“It’s a really interesting project because it’s being done in Milwaukee but the way we’re doing it could theoretically be done in almost any harbor,” Leaf said. “It’s science to inform policy decisions and drive economic activity.”

Jeff Kart is executive editor of the IJC’s Great Lakes Connection and Water Matters newsletters.

Where are Water Levels Heading on the Great Lakes?

By Kevin Bunch, IJC

lake michigan beach water levels great lakes noaa
A Lake Michigan beach located near Frankfort, Michigan, in September 2015. Credit: NOAA

Forecasting agencies in the United States and Canada expect Great Lakes water levels to remain near or above their long-term average for the next six months.

Water levels are measured on the International Great Lakes Datum, defined as the height above sea level at Rimouski Quebec on the St. Lawrence River estuary. According to the coordinated, binational forecast at the beginning of July, Lake Superior is expected to remain about 6 inches, or 15.4 centimeters, above its long-term average for this time of year through the summer, before falling closer to average levels in the fall. While this forecast is based on normal weather conditions in coming months, lake levels could be higher or lower depending on whether we have a wetter or drier than normal summer and fall. Long-term averages are based on data going back to 1918.

Lake Michigan-Huron, which have a common level due to their connection at the Straits of Mackinac, is expected to be 10-12 inches (30.8 cm) above average in the summer before falling closer to average in the fall. Lake Erie also is expected to be within 1 foot above average in the summer before ending closer to 8 inches, or 20.32 cm, above average in the fall. Lake Ontario’s July level is 1 inch (2.54 cm) below average for this time of year and is expected to remain close to average in the fall.

Jacob Bruxer, Environment and Climate Change Canada senior water resources engineer, said Lake Ontario’s comparatively lower water levels are due to the warm, dry weather conditions around the lake that started around March. Bruxer is also a member of the IJC’s International Lake Superior Board of Control and the Great Lakes-St. Lawrence River Adaptive Management Committee.

“Those conditions would be bad if we started at average levels, but we’re right around average,” Bruxer said. “We’re not seeing any significant concerns to shipping or recreational boaters.”

The higher water levels on Superior, Michigan-Huron and Erie mean some boat launches could be underwater and beaches are smaller than they would be with lower levels. On the flip side, boaters should have plenty of depth to get their boats into their docks, and anglers may find more coastal areas to fish than they would otherwise. Bruxer added that high levels can lead to greater erosion along bluffs and shorelines due to waves and storms.

Drew Gronewold, a hydrologist at the Great Lakes Environmental Research Laboratory in Ann Arbor, Michigan, explained that the Great Lakes typically follow a seasonal cycle where water levels rise in the spring from runoff and peak in early summer. The lakes then fall in the autumn and winter months as evaporation — caused by temperature differences between the warm water and cool air — picks up, reaching their lowest point around January and February.

As of mid-July, Gronewold said there’s no indication that the autumn dip will be stronger than usual in the lakes, or that water levels will increase – something that occurred in the autumn and winters of 2013 and 2014 on Lake Michigan-Huron and Lake Superior. Bruxer said the lakes are expected to remain either near or slightly above seasonal averages for the foreseeable future.

Coordinated six-month forecasts of Great Lakes water levels are published online each month by the US Army Corps of Engineers and Environment and Climate Change Canada (via the Canadian Hydrographic Service). The US National Oceanic and Atmospheric Administration (NOAA) also provides these forecasts on its water level online viewer each month. Forecasted water levels are determined using binational data and several different models that account for possible variations in evaporation, precipitation and runoff on the lakes over the coming months.

While forecasts are typically only for a six-month period, the Army Corps of Engineers has recently developed a 12-month probability outlook.

Lauren Fry, civil engineer with the Corps, said the model provides potential outcomes given climatic scenarios, developed based on current conditions and similar existing historical weather data. For example, with the strong El Niño cycling over the past winter, Fry said the agency used data from  similarly strong 1982 and 1997 El Niño events to determine a range of potential lake level impacts from October 2015 until September 2016. The most recent one-year outlook from April suggests higher-than-average water levels will most likely continue until April 2017.

water levels measured feet meters great lakes michigan huron graph
Water levels are measured in feet or meters above sea level, with data compiled by US and Canadian organizations. The green line represents forecasted water levels, while the red line indicates recorded points for Lakes Michigan and Huron as of June 30. Credit: US Army Corps of Engineers

Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.