Art Hasler, Bluntnose Minnows and How Salmon Get Back Home

Happy Fish Fry Day! It’s the day that, like restaurants across Wisconsin, we put fish on our menu. Today’s main course – bluntnose minnows.

Bluntnose minnow on "Fishes of Wisconsin" poster. Photo: Marilyn Larsen
Bluntnose minnow on “Fishes of Wisconsin” poster. Photo: Marilyn Larsen

As we tackle the “Fishes of Wisconsin” challenge, striving to write a post for each of the 183 species of fish found in Wisconsin, one might expect to stumble across a species that, well, just isn’t all that interesting.

I’m happy to report that the bluntnose minnow is NOT that species. In fact, it’s the second species of minnow in as many weeks with connections to an iconic historical figure in our field of study.

Bluntnose minnow.
Bluntnose minnow.

Sure we could tell you that ol’ Pimephales notatus is very likely the most common freshwater fish in the eastern half of North America. We could divulge what it eats and what eats it. Or discuss the new look it gets during the breeding season. But the important thing here is to know that, like many fish, the bluntnose minnow follows its nose.

And that nose played a pivotal role in Art Hasler’s discovery of how salmon return to their natal streams to spawn.

Flash back to the spring of 1945. World War II is over and Art Hasler, a well-established limnologist from the University of Wisconsin-Madison, is serving his country, cataloging the damage done to research stations and laboratories and other scientific edifices as a member of the U.S. Air Force’s Strategic Bombing Survey. Continue reading “Art Hasler, Bluntnose Minnows and How Salmon Get Back Home”

Celebrating World Wetlands Day 3 Ways

Tomorrow is World Wetlands Day, a celebration of the importance (and warning of the fragility) of some of Earth’s most beautiful ecosystems.

The tidal marshes of the Blackwater National Wildlife Refuge, Maryland. Photo: A. Hinterthuer
The tidal marshes of the Blackwater National Wildlife Refuge, Maryland. Photo: A. Hinterthuer

Wetlands, the transitional ecosystem from an aquatic environment to terra firma, provide an incredible array of services to their surrounding landscapes – they filter sediment and pollutants out of the water, they absorb overflow and prevent floods, they provide critical habitat for crabs, fish, waterfowl and a host of other wildlife.

Yet, since the settlement of the United States, we’ve lost more than 50% of our wetlands – draining land for agriculture, paving it for cities, or putting it underwater with dams. With that loss, we’ve seen declines in fisheries and water quality and a rise in flooding and erosion.

Today we’re offering three stories on wetlands to celebrate World Wetlands Day on Februrary 2nd. (Okay, two stories and one slideshow!). We hope you don’t mind getting your feet a little wet!  Continue reading “Celebrating World Wetlands Day 3 Ways”

Winter Redux: What Do Fish Do Under the Ice?

This weekend saw temperatures in the 20s, the sun shining and scores of anglers sitting over holes in the ice of Madison lakes. So we thought we’d revisit a post from this time last year – what life is like for the fish in winter.
These guys can't wait for ice-off so they can start sneakin' Photo: Fargo-Moorhead Dive News
These guys can’t wait for ice-off. Photo: Fargo-Moorhead Dive News

[Originally posted Jan. 30, 2015] – While we’ve been spared (so far) by any sort of climate shenanigans like a polar vortex this winter, our lakes have had a nice thick cover of ice on for a month or more. And lots of people ask variations of the question – what’s life like for fishes under the ice?

Well, the short answer is “Not much different than the rest of the year.” They eat and breathe and try to avoid becoming lunch.But there are some interesting elements to winter life, so we asked CFL grad student, Alex Latzka to help explain. (NOTE: Alex is now a post doctoral research at McGill University)

Up on land, while everything from bears to bats to turtles to raccoons is all curled up, cozy and hibernating, fishes have no such luxury. They have to keep moving enough to pass water over their gills and continue to breathe. But, still, Latzka says, everything slows way down.

“Most forage fishes (like bluegill, or other species that serve as prey for bigger fish) have to stay really still and not expend a lot of energy,” Latzka says. “So they are hanging out in structure, or weed beds, where there’s cover and some food.”

Alex Latzka holds up an impressive pike pulled form the ice of an “undisclosed” Madison lake. Dan Oele assists.

Predators, like northern pike, are then hanging out near the weed beds waiting for something to venture out. Still, Latzka says, “They’re not eating a lot.” Cool water fish like pike and bluegill lose weight in winter, since they can’t find enough food to make up for the “metabolic cost,” or calories they’re burning just staying alive.

In fact, according to the book, “Ecology of Teleost Fishes,” by Robert J. Wootton, in some instances, fish like bluegill won’t eat all winter long, relying on fat stores they accumulated in the fall to get by.

Burbot. Image: New York DNR
Burbot. Image: New York DNR

On the opposite end of that spectrum, cold-water species of fishes thrive in these conditions. While a pike looks a little worse for wear in spring, species like burbot come out of the experience fat and happy. We don’t have burbot in Lake Mendota, but we once had lake trout and cisco, other cold water species that loved long winters, since they weren’t confined to their summer hangout in the coldest, deepest parts of the lake.

And that brings us to another winter issue for fish under the ice – oxygen. With the “lid” on the lake, precious little oxygen enters the water column and  fish are left to survive on what got mixed into the lake in the fall. That’s one reason they slow down so much – being all active and burning through their oxygen reserve is a bad idea.

Oxygen is particularly limited at the bottom of the lake, where microbes are decomposing all of the organic matter that settled out during more productive months. Thanks to the overabundance of nutrients driving all of that growth (and algal blooms) during the summer and fall, Lake Mendota has a LOT of organic matter resting on the bottom and those microbes use up a ton of oxygen breaking it down. The end result can be either hypoxic “low-oxygen” or anoxic “no-oxygen” conditions at the bottom of the lake.

These so-called “dead zones” can also form in summer and are a big reason why you don’t see lake trout or cisco in Lake Mendota anymore – those fishes couldn’t survive when the only remaining parts of the lake with cold-water habitat kept running out of  oxygen every summer.

This is as much excitement as this pike (and Alex Latzka and Jereme Gaeta) will have all winter! Photo: A. Hinterthuer

One final thing about life under the ice that Latzka finds fascinating, is that, in winter, a lake’s habitats get a lot less diverse. “In warmer months, the temperature can vary all over the lake,” he says. Water is nice and warm at the surface, still quite cold down deep, and all sorts of temperature in between those two extremes.

Every species can spread out in search of their optimal temperature comfort zone.

But in winter the entire lake is, more or less, the same temperature. Usually 3 or 4 degrees Celsius. And that leads to behavior you won’t see quite so dramatically in summer.

“If you find warm water inlets,” Latzka says, “and let me qualify by saying ‘Be careful walking on ice near warm water inlets!’ But, where you have pulses of warm water, a lot of species of fish are going to want to be in it, because those levels of temperature change, just a couple of degrees, effects how active they’re going to be, how much they can eat and they’ll grow better in those conditions.”

So there you have it – the not-quite-exciting story of life under ice for our fishes. They mostly stay still, hang out in the same spot and, like a lot of us, wait for spring and open water to get back in action.

Fishes of Wisconsin: Louis Agassiz & the Mississippi Silvery Minnow

Last year we launched an overly ambitious project here on the blog – post each week about one of the 183 species on the epic “FIshes of Wisconsin” poster. That proved easier said than done, but we’re back and ready to tackle more of the 13-foot-long behemoth.

Panorama is a must for a poster this epic. Kandis Elliot's "Fishes of Wisconsin" poster.
Panorama is a must for a poster this epic. Kandis Elliot’s “Fishes of Wisconsin” poster.

This week, a few interesting tidbits about the Mississippi silvery minnow (Hybognathus nuchalis). 

Photo: Marilyn Larsen
Photo: Marilyn Larsen

The Mississippi silvery minnow, like most (but not all) minnows is a small, silver-colored fish found in large schools. This particular minnow prefers the slack water habitat or pools and backwaters  along medium to large rivers and streams. It’s range stretches all along its namesake river from Wisconsin to the Mississippi delta, although it doesn’t stray too far east or west of the Mississippi (except for a population in Texas). Continue reading “Fishes of Wisconsin: Louis Agassiz & the Mississippi Silvery Minnow”

Video: Limnology 101 – Lake Stratification

CFL graduate student, Colin Smith, produced and narrated this first video in our new “Limnology 101” series. Here he explains why lakes separate into warm, upper layers and cold, bottom layers.  Check it out!

Stay tuned for more “Limnology 101,” as we explain some of the basic physical and biological principles of the study of our inland waters.

Note: The video is of the “demonstration only” variety. Some content may not be 100% scientifically accurate, but is still a good example of the basic principles of density and stratification. 

The Bold Prediction on Lake Michigan’s Sport Fishery That, Unfortunately, Was Proven Right

by Steve Carpenter

Every moment, our brains make predictions of what we will next encounter in our lives based on our lifetime of experiences. As our experiences are updated, our brain adjusts and accounts for the new information in its next predictions. The discovery that brains engage in co-evolving cycles of predictions and actions is one of the great accomplishments of neuroscience.

Jim Kitchell's land-mark paper on the Lake Michigan and Lake Huron fisheries accurately predicted tough times for salmon and lake trout. Photo: Detroit Free Press
Jim Kitchell’s land-mark paper on the Lake Michigan and Lake Huron fisheries accurately predicted tough times for salmon and lake trout. Photo: Detroit Free Press

In a microcosm, it represents the way science is made. Scientists routinely make predictions to evaluate ideas. Usually those predictions are wrong and, through these mistakes, we make the ideas better.

Occasionally, however, a scientist is confident enough to make a public prediction and hits the nail on the head. Center for Limnology director emeritus, Jim Kitchell and his colleagues, Don Stewart and Larry Crowder, made such a prediction in 1981, and now their paper is honored as a Fisheries Classic by the American Fisheries Society. Continue reading “The Bold Prediction on Lake Michigan’s Sport Fishery That, Unfortunately, Was Proven Right”

Science on Tap Adds New Short-Format Series to Its Video Archives

IMG_1998On the first frigid Wednesday night of February, 2013, Science on Tap-Minocqua held  its first event at the Minocqua Brewing Company in northern Wisconsin. On February 3rd, we’ll mark the 3-year anniversary with a talk by Trina McMahon on the “Microbes All Around Us.”

We’re celebrating the anniversary with a new series of short-format “highlight” videos. If you can’t make it to Minocqua or tune in online, and if you don’t have time to watch a full-length recap, we’ve got you covered! Our new 5 to 10 minute videos will highlight the primary points of each talk. It’s not the same as being there, but it is a great way to get up-to-speed on a whole lot of amazing science going on in Wisconsin!

You can find the videos on the Trout Lake Station YouTube channel. Our first is a recap of Jonathan Patz’s talk from last October. Patz, who shared the Nobel Prize as a co-author of the IPCC reports and is currently director of the Global Health Initiative at the University of Wisconsin-Madison, spoke about how the world’s response to climate change may prove to be the biggest public health “win” of this generation (video below). Stay tuned for  Stan Temple’s talk on why using cutting-edge science to resurrect extinct species may not be a great idea and Patricia McConnell on the science of dog behavior!


Awards, Judges Set for “Our Waters, Our Future” Writing Contest

MADISON — Two of Wisconsin’s literary leaders will help decide the winner of the Our Waters, Our Future writing contest. Peter Annin, journalist and author of Great Lakes Water Wars, and Fabu, as Madison’s third poet laureate is professionally known, have agreed to help select the top stories that imagine a positive future for water and people in south-central Wisconsin.

What is your vision for the future of Madison's lakes? Image:
What is your vision for the future of Madison’s lakes? Image:

The contest encourages Wisconsinites to envision a desirable future and participate in building that future through storytelling. Representatives from Madison Magazine, which will publish the winning story, will also be part of the judges’ panel.

Peter Annin. Photo: Northland College
Peter Annin. Photo: Northland College

“We are leaving the century of oil and entering the century of water, which means water will become the most important natural resource in the world by 2100. Communication—especially writing—can play a key role in helping people understand just how important water is becoming on a regional, national and international level,” says Annin, who is also the co-director of the Mary Griggs Burke Center for Freshwater Innovation at Northland College.

Originally from the southern United States, Fabu draws on her connection with the Mississippi River, which she says has “watered [her] both historically and creatively.”


“I felt at home in Wisconsin when I saw the Mississippi River in La Crosse. It has been a pleasant discovery learning about the various waters in Wisconsin. Our Waters, Our Future speaks to the importance of this resource, and I am excited to read what writers say about this topic,” says Fabu, who served as Madison’s poet laureate from 2008 to 2012.

Several local businesses specializing in outdoor recreation have offered their support of the contest as awards sponsors for the winner and top finalists, including Fontana Sports Specialists, Brittingham & Wingra Boats, Rutabaga Sports and REI. Local artist John Miller, whose work often features water, will also create an illustration for the winning story.

The contest seeks short stories that are solutions-oriented and, while fictional, are also scientifically plausible. Stories should take place in the year 2070 and in the region around the Yahara Watershed and/or the affiliated counties of Dane, Rock and Columbia.

Despite this regional focus, the contest is open to all Wisconsin residents and students 18 years or older. Since the region contains the state’s capital and flagship university, thousands of acres of productive farmland and valuable water resources, including the Yahara river and lakes, the issues it faces have statewide significance.

The deadline to submit stories is February 1, 2016. Complete contest details can be found at

The contest is a collaborative effort by the University of Wisconsin-Madison’s Water Sustainability and Climate project and Center for Limnology, Madison Magazine, Sustain Dane and the Wisconsin Academy and Sciences, Arts & Letters.


CONTACTS: Peter Annin,, 715-682-1360; Fabu,, 608-235-4745; Jenny Seifert,, 608-512-6259



Fish species, rural livelihoods threatened by new dams on world’s largest rivers

FOR IMMEDIATE RELEASE: Advocates of huge hydroelectric dam projects on the Amazon, Congo, and Mekong rivers often overestimate economic benefits and underestimate far-reaching effects on biodiversity, according to an article in the Jan. 8 issue of Science by a cadre of scientists representing 30 academic, government, and conservation organizations in eight countries.

A map showing current or proposed dams in the drainage basins of the world's largest rivers. Credit: K. Winemiller
A map showing current or proposed dams in the drainage basins of the world’s largest rivers. Credit: K. Winemiller

“These three river basins hold roughly one-third of the world’s freshwater fish species,” said Kirk Winemiller, professor of wildlife and fisheries sciences at Texas A&M University and lead author on the article. “The 450 additional dams being planned or under construction in these basins put many unique fishes at risk.”

The Belo Monte hydropower complex on Brazil's Xingu River. Photo" K. Winemiller
Scientists are concerned about Brazil’s Belo Monte power complex because its placement threatens several species of fish that do not exist elsewhere. Photo by Kirk Winemiller.

Impacts of the hundreds of proposed Amazon dams include forced relocation of human populations and expanding deforestation. “Even when environmental impact assessments are mandated, millions of dollars may be spent on studies that have no actual influence on design parameters, sometimes because they are completed after construction is underway,” said co-author Leandro Castello, assistant professor of fish conservation at Virginia Tech, who studies how global change affects the ecology and conservation of fish and fisheries. “A lack of transparency during dam approval raises doubts about whether funders and the public are aware of the risks and impacts on millions of people.”

“Long-term ripple effects on ecosystem services and biodiversity are rarely weighed appropriately during dam planning in the tropics,” said co-author Peter McIntyre, assistant professor of zoology in the Center for Limnology at the University of Wisconsin–Madison. “There is good reason for skepticism that rural communities in the Amazon, Congo, and Mekong basins will experience benefits of energy supply and job creation that exceed costs of lost fisheries, agriculture, and property. An improved approach to dam evaluation and siting is imperative.”

There is a better way, according to the researchers. For the first time, spatial data on biodiversity and ecosystem services are adequate to support sophisticated analyses that balance the costs and benefits of hydropower. For instance, new analytical methods can account for cumulative impacts from multiple dams upon hydrology, sediment dynamics, ecosystem productivity, biodiversity, fisheries, and rural livelihoods throughout watersheds. “Incorporating these data and tools into assessment protocols would boost the credibility of dam siting in the eyes of all stakeholders,” said Winemiller.

“Institutions that permit and finance hydropower development should require basin-scale analyses that account for cumulative impacts and climate change. Common-sense adjustments to assessment procedures would ensure that societal objectives for energy production are met while avoiding the most environmentally damaging projects,” the article concludes.



The named researchers can be reached as follows:

Kirk Winemiller,, 979-777-8570 (cell)

Leandro Castello,, 774-392-4262 (cell)

Peter McIntyre,, 734-657-1488 (cell)

Dear Mom: Letter Explains Carbon Cycle via Christmas Ornaments

Happy Holidays from the CFL! Graduate student, Julia Hart, is so ready to head home and see family that she wrote this great primer in advance to tell her Mom what, exactly, she studies here at the UW-Madison. Enjoy!

Photo by Paul VanDerWerf via Flickr
Photo by Paul VanDerWerf via Flickr

by Julia Hart

Dear Mom,

How’s it going? Are you busy decorating the house? Are you ready for the whole family to visit? Have you prepared your standard answer for “What are the kids doing these days?”

Well, I’m here to help with that last one—by telling you what exactly it is I do. I know you’re proud of me—that “Julia’s busy studying lakes in Wisconsin.” But what I really do is study the carbon cycle in lakes. I know, I know. Scary words, “the carbon cycle”—nobody ever explains what it really is! It’s a pretty important process—especially when it comes to water quality and climate change. But after you read this, you’ll be able to tell Uncle Steve, Aunt Jan, and all the cousins about your daughter who studies the carbon cycle in Wisconsin lakes. You’re welcome.

Let’s back up a little and start with the big picture. Everything is made up of carbon—this tiny little atom is the building block of life. You are made up of carbon. Trees are made of carbon. Even fish are made of carbon. It’s in our bodies, atmosphere, and lakes. And it’s constantly moving. So how does it even get there? What happens while carbon is in a lake? And where does it end up?

The answer might be in the bins and bins of holiday ornaments you’ve probably dredged up from the basement in the last few days. Let’s think about all of those ornaments as carbon. And our house as the lake. Continue reading “Dear Mom: Letter Explains Carbon Cycle via Christmas Ornaments”