Giant, Fishy Poster = Happy Fish Fry Day!

Nearly all of the Freshwater Fish of North America in one poster via Pop Chart Labs.

Nearly all of the Freshwater Fish of North America in one poster via Pop Chart Labs.

We’re going to admit that we still favor the more life-like illustrations of the gigantic “Fishes of Wisconsin” folder but, well, you have to give props to biodiversity! Presenting the Freshwater Fish of America, perhaps the only fish-related poster you will ever need. (Excepting that Wisconsin one, of course!) Details about the poster are here.

Happy Fish Fry Day!

What Can Snails Tell Us About Water Quality?

Pete McIntyre

Pete McIntyre

For the past 20 years, biologist Pete McIntyre has traveled to Africa’s Lake Tanganyika, Earth’s second-largest freshwater lake by volume, to study freshwater snails found nowhere else in the world. McIntyre, a professor with the University of Wisconsin-Madison, explains why these snails are important and what they tell us about pollution in the lake.

Q: First off, why study snails?

A: The snails of Lake Tanganyika are very diverse by freshwater snail standards. They’re interesting biologically, but we can also use them as sentinels for change in the environment. Unlike fish, they’re stuck at the bottom of the lake. So if some aspect of the environment changes, they’re also stuck with whatever bad things happen to the system.
Snails are painted bright shades of nail polish so they're easier to locate after they've been put back into Lake Tanganyika. Photo: Ellen Hamann

Snails are painted bright shades of nail polish so they’re easier to locate after they’ve been put back into Lake Tanganyika. Photo: Ellen Hamann

Guest Post: Focus on Phosphorus Control to Improve Water Quality

by Steve Carpenter

Summer is the season for unsightly and toxic blooms in lakes, and 2016 has been a banner year, with major blooms in Florida, Wisconsin’s Lake Petenwell, and other Wisconsin lakes, including those in Madison. The blooms of cyanobacteria produce toxins that threaten human health, like the bloom in Lake Erie that shut down Toledo’s water supply in 2014.

An algae bloom in Lake Erie is capture via satellite photo. Toledo sits on the far western shore of the lake. Photo: NOAA

An algae bloom in Lake Erie is capture via satellite photo. Toledo sits on the far western shore of the lake. Photo: NOAA

What’s more, many cyanobacteria float and form scums that accumulate, rot on beaches, and cause fish kills.

These severe blooms amplify the urgency behind a statement issued today by Canadian and American scientists, myself included, for governments around the world to focus on a proven solution — that is, we must control phosphorus to decrease the intensity and frequency of harmful algal blooms.

A mid-October algae (or phytoplankton) bloom shows up on the Lake Mendota shoreline. Photo: Sam Oliver

A mid-October algae (or phytoplankton) bloom shows up on the Lake Mendota shoreline. Photo: Sam Oliver

Readers of this blog know that phosphorus inputs to lakes and reservoirs, which come from agricultural and urban runoff, are the main driver of blooms, and that phosphorus reduction is the key to improving water quality. Some government agencies, however, have lost sight of this basic fact of lake management.

Recently, some scientists and managers have argued for the control of nitrogen and phosphorus at sewage treatment plants. In response, the European Union has required the removal of both nitrogen and phosphorus from sewage effluents, and in 2011 the US EPA announced that it would be “partnering” with states to control both phosphorus and nitrogen. New Zealand imposed a nitrogen-loading cap on the watershed of its largest lake, Lake Taupo, but failed to define a limit for phosphorus loading. Continue reading

Summer Intern Reflects on the Trout Lake Experience

We had the pleasure this summer to welcome Anna Krieg to a summer spent living, working and playing in Wisconsin’s Northwoods. To say the lake-studded landscape was new to the Arizona resident would be an understatement. We think we made a positive impression, anyway! Here is Anna’s recap of her time up at the CFL’s Trout Lake Station. 

by Anna Krieg

On August 4th, undergraduates gathered in the Juday Conference Room at Trout Lake Station to present their independent projects to an audience of Trout Lake Staff, Center for Limnology faculty, and the people who generously sponsored their summer work. Dom Ciruzzi, a graduate student at UW-Madison, spoke about his experiences this summer as the Graduate Student Fellow where he was saddled with the not-so-simple task of mentoring the undergraduates through their independent projects. I was asked to speak on behalf of the undergrads about the undergraduate experience at Trout Lake Station and these are my thoughts:

(From left to right) Maggie Sobolewski, Brandon Debraska, Keith Lyster, Emily MacParlane, Dom Ciruzzi, and Luke Maillefer presented at the Fellows Luncheon on August 4th. Photo: Anna Krieg

(From left to right) Maggie Sobolewski, Brandon Debraska, Keith Lyster, Emily MacParlane, Dom Ciruzzi, and Luke Maillefer presented at the Fellows Luncheon on August 4th. Photo: Anna Krieg

The undergraduate experience at Trout Lake is unique; I don’t believe there is any other place quite like it. Every undergrad that works here has a different perspective on this experience, on what makes Trout Lake Station special. From those who have been here every summer of their undergraduate career to those who have only experienced one Trout Lake summer, some common themes have arisen to explain the phenomenon that is Trout Lake. This station is a place to grow and change without fear, it is a place where academic and professional goals are developed and solidified, and it is a place which fosters a community that every undergrad who comes through needs in one-way or another.

Summer 2016 undergrads enjoy sunset on Trout Lake Station's pier. Photo: Anna Krieg

Summer 2016 undergrads enjoy sunset on Trout Lake Station’s pier. Photo: Anna Krieg

This summer, I had the privilege of being the Outreach and Communication Intern; Continue reading

Lake Tanganyika Fisheries Declining from Global Warming

by Mari N. Jensen and Adam Hinterthuer

FOR IMMEDIATE RELEASE – The decrease in fishery productivity in Africa’s largest lake is a consequence of global warming rather than just overfishing, according to a report to be published this week in the Proceedings of the National Academy of Sciences.

Local fishers on Lake Tanganyika. Photo credit: Saskia Marijnissen.

Local fishers on Lake Tanganyika. Photo credit: Saskia Marijnissen.


Lake Tanganyika, situated mainly between Tanzania and the Democratic Republic of the Congo, was already becoming warmer in the late 1800’s – the same time that abundance of fish began declining, the team found. The lake’s algae – fish food – also started decreasing at that time. However, large-scale commercial fishing did not begin on Lake Tanganyika until the 1950s.

The new finding helps illuminate why the lake’s fisheries are foundering, said the study’s lead author, Andrew S. Cohen, a geoscientist at the University of Arizona.

“Some people say the problem for the Lake Tanganyika fishery is ‘too many fishing boats,’ but our work shows the decline in fish has been going on since the 19th century,” Cohen said. “We can see this decline in the numbers of fossil fish going down in parallel with the rise in water temperature.”

Ben Kraemer and his group of volunteer limnologists prepare to head out on Lake Tanganyika. Photo: Ben Kraemer

Ben Kraemer and his group of volunteer limnologists prepare to head out on Lake Tanganyika. Photo: Ben Kraemer

The fact that Lake Tanganyika’s fishery has been in decline since before commercial fishing began, says Ben Kraemer, a graduate student at the University of Wisconsin’s Center for Limnology, is at the “heart of this study.” Lake Tanganyika yields up to 200,000 tons of fish annually and provides about 60 percent of the animal protein for the region’s population.

Kraemer has spent a large portion of the last several years in Tanzania researching temperature changes and fishery impacts. “The fish are not just a huge protein source for people, they’re also a huge part of the livelihood and income of people involved in the fishing trade,” he says.

While Kraemer and the paper’s other authors acknowledge that overfishing is one cause of the reduction in catch, they suggest sustainable management of the fishery requires taking into account the overarching problem that as the climate warms, algae – which is the basis for the lake’s food web – will decrease.

And it won’t just be fish food that decreases, but fish habitat as well. In fact, the warming of the lake has reduced the suitable habitat for many species by 38 percent since the 1940s, the team found.

“The warming surface waters cause large parts of the lake’s floor to lose oxygen, killing off bottom-dwelling animals such as freshwater snails,” Cohen said. “This decline is seen in the sediment core records and is a major problem for the conservation of Lake Tanganyika’s many threatened species and unique ecosystems.”

In tropical lakes, increases in water temperature reduce the mixing between the oxygenated top layer of the lake and the nutrient-rich but oxygen-free bottom layer of the lake, Cohen said. Fewer nutrients in the top layer mean less algae and therefore less food for fish.

Pete McIntyre

Pete McIntyre

Those rising temperatures also mean less space for fish, says Pete McIntyre, a professor at the UW-Madison Center for Limnology and another of the paper’s co-authors. In fact, based on instrumental records of oxygen in the lake water, the study’s researchers calculated that since 1946 the amount of oxygenated lake-bottom habitat decreased by 38 percent.

That’s because, unlike temperate lakes in North America, the oxygen in a deep tropical lake like Lake Tanganyika doesn’t go all the way down to the bottom. Instead, says McIntyre, there’s a “floor” within the water column and, beneath that floor, there is no more oxygen in the lake. Over the last 150 years, that floor has been rising in Lake Tanganyika.

“Whether you’re a snail living on the bottom, or a fish swimming in the middle of the lake, you have less oxygenated habitat to operate in than you used to,” says McIntyre.

This shrinking habitat is reflected in cores the team of scientists took from Lake Tanganyika’s bottom sediments. The remains of fish, algae, molluscs and small arthropods are preserved in the annual layers of sediment deposited in the bottom of Lake Tanganyika. By examining cores from the bottom of the lake, the team reconstructed a decade-by-decade profile of the lake’s biological history going back 1,500 years.

The team found that as the lake’s temperature increased, the amount of fish bits, algae and molluscs in the layers of sediment decreased.

You can think of the story playing out in Lake Tanganyika like a play, says McIntyre, “It’s not that the cast is changing, it’s that the amount of stage they have to work with is being reduced. That means fewer fish for people to catch and less habitat to support viable populations of the amazing diversity of life in Lake Tanganyika.”

“We know this warming is going on in other lakes,” adds Cohen. “It has important implications for food and for ecosystems changing rapidly. We think that Lake Tanganyika is a bellwether for this process.”

The study’s authors are Andrew S. Cohen, University of Arizona, Elizabeth Gergurich, now at the University of Oklahoma in Norman; Benjamin Kraemer and Peter McIntyre of the University of Wisconsin, Madison; Michael McGlue of the University of Kentucky in Lexington; James M. Russell of Brown University in Providence, Rhode Island; Jack D. Simmons, now at Weston Solutions, Inc. in Austin, Texas; and Peter W. Swarzenski, now at the International Atomic Energy Agency of Monaco.

The National Science Foundation, the Lake Tanganyika Biodiversity Project, the U.S. Geological Survey, the Society of Exploration Geophysicists Foundation, the Packard Foundation and the Nature Conservancy funded the research.

* This release is a modified version of the original version written by Mari N. Jensen at the University of Arizona.

Researcher contact:

Peter McIntyre

University of Wisconsin – Center for Limnology


Ben Kraemer

University of Wisconsin – Center for Limnology

Andrew S. Cohen

University of Arizona

After July 16: +1-520-621-4691

James Russell

Brown University


Up In the Air: Understanding Lake Mendota’s Climate Contributions

An unusual scene at Picnic Point – Ankur Desai’s lab prepares to install an anemometer and gas analyzer on the UW Safety tower. Photo: A. Hinterthuer

On a hot, windy morning in late June, Ankur Desai and other members of his lab took their first steps to bridging a big gap in data between the aquatic and atmospheric sciences, as they set out in a cherry picker for a leisurely ride down the Lakeshore Path. Jonathan Thom and David Reed, two research associates in Desai’s lab, led the slow-rolling charge toward the UW-Madison’s safety pole stationed at Picnic Point.

While we often tout Lake Mendota as “the most studied lake in the world,” when it comes to how the lake interacts with the atmosphere around it, says Desai, “we’ve really just been scratching the surface.” Continue reading

6th Annual Trout Lake Open House – August 5th!

BOULDER JUNCTION, WI – The UW-Madison Center for Limnology will host its 6th annual open house at the Trout Lake Research Station on Friday, August 5th.


Visitors on the pier watch researchers haul in a Fyke net at the Trout Lake Open House.

From 1 to 5pm, visitors will get a first-hand look at what research is going on at the station this summer, as well as meet the scientists and students conducting it.

Visitors will have the chance to ride out on pontoon boats for a “research cruise” on Trout Lake, meet some of the fish that call Wisconsin’s northern lakes home, learn to tell invasive species from natives, and talk with scientists about the state of Wisconsin lakes and our role in keeping them healthy for future generations.

Freshwater bryozoan

Freshwater bryozoan

There will be aquatic-themed crafts for kids, an art exhibition of material produced by the station’s annual “Artists in Residence,” and, of course, free Babcock Dairy ice cream brought up from the University of Wisconsin’s Madison campus!

The event is free and open to visitors of all ages.

Scientists at the Center for Limnology conduct research all over the world, exchanging knowledge and helping to solve global environmental problems. We hope you’ll join us at Trout Lake Station, where researchers are doing world-class research on Wisconsin lakes.

Trout Lake Station is located at 10810 Hwy N. (between Hwy 51 and Hwy M). For more information, call 715-356-9494.

Notes from the Northwoods: Putting Aquatic Plant IQ to the Test

This summer, Anna Krieg, an undergraduate at Arizona State University, will spend a few months in a much wetter habitat as the CFL’s summer outreach intern at our Trout Lake Station. These are her Notes from the Northwoods:

Susan Knight points out the features of an aquatic plant during the small group rotations. Photo: Anna Krieg

Susan Knight points out the features of an aquatic plant during the small group rotations. Photo: Anna Krieg

by Anna Krieg – On June 28th, 25 people climbed into 6 boats and set off to identify plants on Tomahawk Lake in northern Wisconsin. It was a beautiful day, sunny and calm, and it was time to put everything we’d learned that day to the test. How much did we know about aquatic plants?

From June 28th-30th, aquatic plant identification workshops were held at the Kemp Natural Resource Station, part of the UW-Madison’s College of Agricultural and Life Sciences (CALS) and located just outside Minocqua. Employees from Wisconsin’s Department of Natural Resources mostly populated the classes, but there were also a handful of local residents who just wanted to be able to better identify the plants living in “their” lakes.

Each day started with an introductory PowerPoint session and then everyone was broken up into small groups and began their rotations around the room to learn about all of the aquatic plants. Susan Knight, Interim Direction of UW-Trout Lake Station, spent the week before the plant workshop collecting these samples for the class. Knight is the Center for Limnology’s “plant guru,” and has spent much of her career getting to know the flora of northern Wisconsin lakes. She can stand for hours on end at our annual open houses, just holding court on everything from the invasive Eurasian water milfoil to native carnivorous bladderworts. She has even shared some aquatic plants stories on WXPR public radio.

Continue reading

Wisconsin’s Shrinking Panfish & New Fisheries Management Policy

Happy Fish Fry Day! Enjoy this post from the Long Term Ecological Research Network.

Bluegill hooked on Crystal Lake in northwestern Dane County, 1998. Photo: WDNR

Bluegill hooked on Crystal Lake in northwestern Dane County, 1998. Photo: WDNR

by Terra Alpaugh

Between 2013 and 2015, Andrew Rypel traveled the state of Wisconsin attending public meetings led by state and local fisheries staff— always with a set of graphs in hand. These graphs showed the steady decline in the size of panfish found in state lakes over the past seventy years. Panfish (unsurprisingly) are fish that fit nicely in a frying pan — as opposed to the larger, more charismatic, and better-regulated gamefish. Showing citizens his evidence of shrinking panfish size, Rypel and collaborating fisheries management staff asked, “What, if anything, should we do about it?”

Rypel, a fishery ecologist with Wisconsin’s Department of Natural Resources (WDNR) and the Northern Temperate Lakes LTER, published the research behind those graphs in Fisheries in May 2016. It relied on fish surveys conducted by the WDNR and its predecessor, the Wisconsin Conservation Department, supplemented by 35 years of NTL LTER surveys and some careful statistical analysis. Their study found that while the mean size of panfish was declining, gamefish were mostly getting bigger — or at least holding their ground. Keep Reading –> 

Slideshow: Highlights from Hasler Lab’s 5th Annual Open House

June 24th dawned warm and clear and it was obvious that we’d picked a beautiful day to open our doors to the public. By the time we wrapped things up at 6pm, nearly 300 people had passed through Hasler Lab and learned a little bit about their lakes and the work we do. We hope you enjoy these pictures and we’ll see you next year!

(Fantastic photography courtesy: Sarah Collins, Mark Gahler and Carol Jenkins-Espinosa)