Scientists Go With the Flow to Collect Better Freshwater Data

On a clear, sunny afternoon this September, two of Trout Lake Station’s green-hued jon boats were out on Sparkling Lake, just off of highway 51. For CFL faculty member, Emily Stanley, and grad student, Luke Loken, it was like a lot of other days at the office. For Scott Ensign, however, the outing was the first lake-based field test for what could be a big advancement in aquatic scientific equipment.

Scott Ensign displays a HydroSphere he recovered from Sparkling Lake. Photo: Emily Stanley

Scott Ensign displays a HydroSphere he recovered from Sparkling Lake. Photo: Emily Stanley

Earlier in the week Ensign, a co-founder of Planktos Instruments, had dropped two hard-plastic spheres containing thousands of dollars of instrumentation into the crystal clear waters of Sparkling Lake. He calls the devices “HydroSpheres” and their job is to float along with currents in the lake like some sort of free-range buoy and collect data on the lake’s temperature, water chemistry and productivity.

Ensign’s company had already honed the HydroSphere’s spherical design to sit at neutral buoyancy just below the water’s surface and travel down rivers, specifically the Neuse and Cape Fear Rivers in North Carolina, where the company is based. But Sparkling was their first attempt at a lake. Continue reading

Arthur Hasler Tells UW-Madison Video Archives “Lake Mendota Is Our Laboratory”

We recently stumbled across this old video of Art Hasler (in an amazing coat/hat ensemble, we might add) discussing the “congregation” of professors and students at the UW-Madison who work on Lake Mendota “trying to unfathom the unknowns of the aquatic community.” We hope you enjoy it as much as we did!

The video was embedded in a short piece on Hasler history called “Lake Mendota is Our Laboratory” published on the UW Archives webpage. It’s a good read and full of interesting insights into one of limnology’s forefathers.

Hasler and Fisherman

Hasler (right) conducts a creel census, checking in on an unidetified Lake Mendota ice angler. Photo: UW Archives



Lake Mendota: A Scientific Biography

How did we miss this excellent feature on Lake Mendota and the CFL? We have no idea, but better late than never – enjoy!

By: Masarah Van Eyck

Steve Carpenter. ©UW-Madison University Communications  Photo by: Jeff Miller

Steve Carpenter.
©UW-Madison University Communications
Photo by: Jeff Miller

From the window of his second-story office overlooking Lake Mendota, Steve Carpenter can see the UW rowing team running drills. On a warmer day, he might glimpse yellow-hulled “tech” boats, piloted by amateur sailors, lurching around the buoys. And on an early autumn morning, a lone paddler might suggest the image of a traveller from long ago, navigating the waters in a birchbark canoe.

Like all lakes, this one holds the past, present and even the future in its depths.

“Lakes reflect the land around them,” Carpenter says. “They also reflect the ways that humans use that land, and the ways we use the water.”

Often called “the most studied lake in the world,” Mendota is the birthplace of the field of limnology, the scientific study of inland waters. Thanks to a trove of long-term data gathered over more than 100 years by UW scientists like Steve Carpenter, the connection between Mendota and the humans who have interacted with it over time is unusually well understood.

This data offers a glimpse of the lake’s future — one that Carpenter and his colleagues are eager for us to realize that we are responsible for writing. Continue reading here –>

Fishes of Wisconsin: Attack of the Clones

Happy Fish Fry Day! Once again fish is on the menu here at the CFL blog (and just about every restaurant in Wisconsin). Today we’re continuing the epic slog through all of the images on the Fishes of Wisconsin poster and we’re sticking with small plates. In fact, it’s a two-course deal. Introducing, the finescale dace and the northern redbelly dace.

Photo: Marilyn Larsen

Photo: Marilyn Larsen

Many anglers many know finescale dace (Chrosomus neogaeus) and northern redbelly dace (Chrosomus eos) as relatively hardy kinds of bait fish, which likely has readers of this blog groaning “Not again! TWO tiny fishes? Didn’t we have a boring little minnow last time?”

Photo: Marilyn Larsen

Photo: Marilyn Larsen


Well, yes, yes we did.

But the fact that no one came to the defense of the bullhead minnow’s reputation doesn’t discount the following facts:

  1. Dace aren’t minnows.
  2. Minnow” does NOT mean “little fish.”
  3. When it comes to reproduction, when the finescale dace meets a northern redbelly dace, something crazy happens.

Continue reading

At Home in the Water, “Condemned” to Life on Land

This essay originally appeared in the Lakeland Times in Minocqua, Wisconsin. Carol is an Aquatic Invasive Species expert and outreach specialist with the CFL and Wisconsin DNR.

by Carol Warden

Carol Warden for a short stay in her favorite element. Photo courtesy: Carol Warden

Carol Warden for a short stay in her favorite element. Photo courtesy: Carol Warden

Throughout my life I’ve been surrounded by water. Whether it was lakes, rivers or the sea, the water and I have had an intimate relationship. I remember thinking as a child, “These fish are so lucky; they never have to get out of the lake. They get to swim all day. How do they breathe underwater and what’s stopping me from doing it?”

A fish depends on oxygen just like we do except fish breathe oxygen that is dissolved in water. Instead of having lungs to breathe, a fish has gills. Lungs and gills have the same purpose; they both supply the body with oxygen.  Unlike human lungs that sit inside our bodies, gills of a fish are on the outside of their bodies. They sit right behind the mouth on both sides of the fish like where an ear is on our head. On some fish, the gills curve from the eye to the mouth. On other fish like sharks, the gills look like slits from a knife on the side of their bodies.

Most fish can open their mouths and let water in then when they shut their mouths the water is forced out past their gills and the gills absorb the dissolved oxygen in the water. Other fish, like tuna, don’t have the best system to force this water out and so they have to swim continuously so water is constantly passing over their gills.

Courtesy: University of Maryland Extension

Courtesy: University of Maryland Extension

Gills are very delicate, almost paper-like structures that depend on the buoyancy of water to remain open. The fragile gills will collapse if the fish is taken out of the water because air doesn’t have the same density and buoyancy water has to keep the gills open and functioning. This is why a fish cannot live outside the water. Gills also have much more surface area proportionate to their bodies than our lungs do proportionate to our bodies. This added surface area allows the fish to be very efficient at removing oxygen from water. Since water only holds a fraction of oxygen air does, it is important for fish to be really efficient breathers. Some fish can remove up to 85 percent of dissolved oxygen from the water that passes over their gills.

Carol feeds her lungs the oxygen they need via the compressed air of a scuba tank. Photo courtesy: Carol Warden

Carol feeds her lungs the oxygen they need via the compressed air of a scuba tank. Photo courtesy: Carol Warden

Alas, I will never be able to join the fish and swim all day. Gills are great for air and water exchange while our human lungs are only adapted to exchanging air. If our lungs were on the outside of our bodies like fish, we would lose too much water from our bodies because we don’t have the constant replenishment of moisture like fish do living in water. The same is true for a fish out of water. Even if their gills did not collapse, they would eventually lose too much water from their bodies to survive. They require a constant flow of water over their gills to absorb dissolved oxygen and to keep their gills moist. Also, our lungs do not have enough surface area to pull out the amount of oxygen from water that we humans require to live. I’m condemned to a life on land.

Fish Fry Day: Bass Set to Win, Walleye Lose Under Warming Projections

We interrupt the “Fishes of Wisconsin” challenge to be bring you this report from former CFL graduate student/post doc, Gretchen Hansen. Published yesterday in the journal Global Change Biology. For more, check out this amazing website


Contact: Gretchen Hansen; Minnesota DNR,, 651-259-5245

Climate change predicted to change sport fish communities in Midwestern lakes

MADISON, WISCONSIN—Climate change is predicted to alter sport fish communities in Midwestern lakes, according to a new study that related water temperature to suitability for walleye and largemouth bass in over 2,100 Wisconsin lakes.

Walleye. Photo: Gretchen Hansen

Walleye. Photo: Gretchen Hansen

Walleye populations have been declining and largemouth bass populations have been increasing in lakes across Wisconsin for the past 30 years. These changes are cause for concern for many anglers and policy makers; freshwater fishing in Wisconsin is valued at over $1.5 billion, and walleye are the preferred species for many anglers.

Researchers identified characteristics of lakes where walleye or largemouth bass were most likely to thrive. Both species were strongly influenced by water temperature; walleye populations thrived in cooler, larger lakes, while largemouth bass were more abundant in warmer lakes.

“Generally this means that lakes that are best for walleye are not the best for largemouth bass, and vice versa” said study author Gretchen Hansen, former Wisconsin DNR Research Scientist currently with the Minnesota DNR. “Going forward, we predict that many Wisconsin lakes are going to become more suitable for largemouth bass, and less suitable for walleye”. Continue reading

Fishes of Wisconsin: Help Us Prove That Bullhead Minnows Aren’t Boring

Happy Fish Fry Day, the weekly holiday where our fair state (always) puts fried fishes on the menu and we here at the CFL (sometimes) put fishes on the blog. Summer’s drawing to a close and it’s time to resume our “Fishes of Wisconsin” challenge.

Without further ado, I give you – the bullhead minnow.

Bullhead minnow illustration on the Fishes of Wisconsin poster. Photo: Marilyn Larsen

Bullhead minnow illustration on the Fishes of Wisconsin poster. Photo: Marilyn Larsen

Houston, we have a problem. We once promised to prove to you that each Wisconsin fish is amazing in its own right. But, well…it’s really hard to find something all that interesting about a bullhead minnow.

Pimephales vigilax is one of four of the pimephales species, generally referred to as the bluntnose minnows as a whole, but also including the “bullhead,” “fathead” and (winner of the most flattering pimephales nomenclature) the “slim” minnow.

The native range of the bullhead minnow includes streams and rivers of the Mississippi River Basin, tributaries of Lake Michigan and Lake Huron and even the Rio Grande, where they prefer shallow, silty habitat and eat lots of aquatic insects. But, given their affinity as bait for fishermen, they’ve managed to move into unconnected waters throughout the years via bait buckets. The USGS map below illustrates this perfectly in the form of the red splotches far outside of the bullhead minnow’s home range.

US auto-generated map

And that, dear reader, is where the trail runs cold. We have nothing more to report on the bullhead minnow. So, in a first for this blog, we are asking you, our reader, to submit any sort of trivia, picture, anecdote or story into this narrative – what makes a bullhead minnow cool? Help us keep the streak alive and fill our comments section with tales of the majesty of this lowly minnow and we will update accordingly.

And, again, Happy Fish Fry Day!



Yahara Watershed to Star on Wisconsin Public Television – Sept. 1st

by Jenny Seifert

The future of the Yahara Watershed takes center stage in a new documentary born of a partnership between the UW-Madison’s Water Sustainability and Climate project (WSC) and Wisconsin Public Television (WPT). Called “Yahara Watershed: A Place of Change,” the show will debut on Thursday, September 1st at 7:30pm on WPT.

Will technological advances save the Yahara watershed? Illustration: John Miller

Will technological advances save the Yahara watershed? Illustration: John Miller

Nearly five-years in the making, the thirty-minute documentary features the research conducted by the WSC project team (Steve Carpenter and Corinna Gries from the Center for Limnology are two of the six principal investigators on the project) which is studying the impacts of changes in climate and land-use on freshwater resources and other natural benefits in the Yahara Watershed.

The show focuses on challenges related to the co-existence of agriculture and urban life in the region, as well as an innovative way of investigating what these challenges and their potential solutions could mean for the future of its water and people.

“Having WPT integrated into our WSC project from the beginning has allowed us to showcase interdisciplinary research from a perspective that differs significantly from our traditional reporting of research in scientific journals,” says Christopher Kucharik, lead principal investigator for the WSC project and a professor of agronomy and environmental studies at UW-Madison.

As this map shows, land in the Yahara Watershed is used for all sorts of purposes, from agriculture to development to public open space. Managing the area for these mixed uses is a challenge.

As this map shows, land in the Yahara Watershed is used for all sorts of purposes, from agriculture to development to public open space. Managing the area for these mixed uses is a challenge.

The partnership sprouted fortuitously through a personal connection just as the research team was assembling the proposal for the National Science Foundation grant they eventually received. While no one knew exactly how the documentary would unfold at the time, the end result is a critical component of the project’s outreach portfolio.

“This affords us a unique opportunity to reach a much broader audience through a storytelling lens,” says Kucharik.

The partnership also serves WPT’s mission to contextualize issues affecting Wisconsinites and improve the public understanding and application of that knowledge, explains Christine Sloan-Miller, executive producer of news and public affairs at WPT.

“Since water science affects us all, and climate science is rapidly becoming the most pressing area of study for the future, it was a natural partnership opportunity. Our job is to shine light on the relevant issues to enable a wider, more well-informed dialogue,” says Sloan-Miller.

Click here for additional air times.

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