Category Archives: Invasive Species

Invasives Hitch Rides with Boaters, Not Birds

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When it comes to moving in to Wisconsin lakes, aquatic invasive species have a preferred mode of transport – one that often involves an outboard motor.

Lakes with lots of boat traffic are far more likely to contain invasive species than wilderness lakes. Photo: Alex Latzka

Boaters prepare for a fishing tournament. Lakes with lots of boat traffic are far more likely to contain invasive species than wilderness lakes. Photo: Alex Latzka

Scientists at the UW-Madison Center for Limnology and the Wisconsin Department of Natural Resources are in the middle of a five year study exploring the spread and distribution of exotic plants and animals into our inland lakes. They’ve discovered that natural dispersal mechanisms, like birds carrying invasives in beaks or bellies, can’t explain the patterns they’re seeing. Only human intervention makes the maps make sense.

“None of the wilderness lakes we surveyed had invasive species in them,” says Alex Latzka, a graduate student in the Jake Vander Zanden lab at the CFL. “But, 30 percent of the lakes we looked at that had human development, like nearby roads, shoreline homes and boat ramps, had at least one invasive species present.”

Although iconic images of northern Wisconsin, invasive species aren't much of a threat to isolated "wilderness" lakes. Photo: Emily Hilts

Although iconic images of northern Wisconsin, invasive species aren’t much of a threat to isolated “wilderness” lakes. Photo: Emily Hilts

The CFL and DNR are monitoring 450 lakes in Wisconsin, hoping that uncovering trends in invasive species dispersal will allow them to better direct their time (and funds) toward protecting lakes that currently boast only native species but will likely face pressure from invasives in the future.

“People often think that the lakes that are the most worthy of our protection and most susceptible to invasion are the pristine wilderness lakes,” Latzka says. “While those kinds of lakes are iconic in the Wisconsin Northwoods, they’re not the lakes most vulnerable to invasive species.”

And there’s also a lot of variability among lakes with signs of human development. For example, only 30% of lakes with public access had Eurasian water milfoil, a prolific exotic plant, and fewer than 20% of lakes had zebra mussels, despite both invasives being problematic exotic species that have thrived in the state for decades.

Alez Latzka (foreground) and Yuri Caldeira wade to shore after surveying a "wilderness" lake for invasive species. Photo: Emily Hilts

Alez Latzka (foreground) and Yuri Caldeira wade to shore after surveying a “wilderness” lake for invasive species. Photo: Emily Hilts

By getting to the bottom of differences like these and getting high risk lakes on the map, Latzka and researchers at the WDNR and CFL hope to better predict and, ideally, prevent invasive species introductions in the future.

To read more on the invasive mapping effort, go here and here.

Carving Ice and Catching Smelt: Winter Sampling on Crystal Lake

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Some of the ice is re-purposed as a mount for the gill net. Page clears the hole so the net can then be slowly unwound into the lake.

Some of the ice is re-purposed as a mount for the gill net. Page clears the hole so the net can then be slowly unwound into the lake.

Last summer, scientists at the CFL launched an ambitious attempt to eradicate invasive rainbow smelt from Crystal Lake in northern Wisconsin. Last weekend, Zach Lawson and Page Mieritz went up north to sample for smelt as researchers look to see what effect the experiment has had on the population.

According to CFL director, Steve Carpenter, “it’s not zero.” In fact, results point to smelt numbers being down by anywhere from 30% to 90%, but we don’t yet know how much of that is natural winter die off versus a result of the experiment. “We have the data to get an estimate, but this is a very complicated calculation,” Carpenter says. The four smelt Zach and Page found over the weekend add to the mountain of data researchers are sifting through to piece the puzzle together.

(Click on any picture below for slideshow view. Photos by Page Mieritz, Zach Lawson)

 

Study Documents Round Goby’s Rapid Invasion of Wisconsin Streams

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Round gobies are usually a mottled, beige/brown color, but males turn jet black during spawning. Photo credit: Matt Kornis

Round gobies are usually a mottled, beige/brown color, but males turn jet black during spawning. Photo credit: Matt Kornis

In 1990, a small stowaway was dumped from the ballast tank of an ocean-going freighter into the waters of the St. Clair River, joining more than 180 other non-native species in the Great Lakes. Two decades later, the round goby, an aggressive, voracious, bottom-dwelling fish has invaded all five Great Lakes and has had profound impacts on other fish populations. As is the case with most aquatic invasive species, the lakes were only the first stop of the goby invasion. Now new research out of the Center for Limnology (CFL) shows that the fish is rapidly spreading into Wisconsin streams.

Researchers studied sites throughout Wisconsin tributaries of Lake Michigan for the presence and abundance of round gobies and several native fishes.

Researchers studied sites throughout Wisconsin tributaries of Lake Michigan for the presence and abundance of round gobies and several native fishes.

Reporting in the February issue of the journal Diversity and Distributions, a team of CFL-affiliated researchers shows that, between 2007 and 2010, goby populations in already invaded streams increased more than ten-fold. And that’s just the average increase, says Matt Kornis, the study’s lead author and a postdoctoral fellow at the Smithsonian Environmental Research Center. In some cases, the goby population boom was much more pronounced. Take, for example, the Ahnapee River in Door County, Wisconsin. “At one site we caught a single round goby in 2007,” Kornis recalls. “In 2010, using the same sample method, we caught upwards of 60.” Continue reading →

Wordless Wednesday – Take 7

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LTER Fish Crew member (and UW Undergrad), Chantal Van Guten, weighs a common carp caught in a Trammel net during the fish crew’s annual census of Wisconsin fish. It wasn’t all carp, though, plenty of desirable fish like perch, walleye and pike were hauled in as well!

Another week, another winner! Blog follower “Gator” heaves a last-second desperation shot at the buzzer and wins it all (note: “it” ain’t much!) with the caption:

The Carp Curl

Since the “fish weighs more than you do” jokes were flying during the taking of that shot, we had to give a nod to anything referencing aquatic weightlifting. Although we will start calling Chantal “Aquagirl” around here thanks to a solid runner up post.

As always, the real caption is now attached to the picture. And, as always, another round of the Wordless Wednesday caption contest begins now. See you all after Turkey Day and have fun captioning the unusual signage below!

 

Enter caption contest by providing your own humorous suggestion in the comments section below.

Limno in the Lab: Fish Ears, “Tree” Rings and a Sectioning Saw

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Aaron Koning uses a sectioning saw to cut a slice of otolith that will be mounted on a slide and polished, enabling him to see it clearly under a microscope.

After the spring and summer field seasons, it’s time to return to the lab to work up all the specimens collected in the field. For many grad students at the Center for Limnology, this means days, if not weeks, hunched over a circular sectioning saw and buffing wheel.

What are they doing using equipment more appropriate for a jewelry store? Cutting and polishing fish ear stones, of course.

These ear stones, or otoliths, are small disks of calcium carbonate that grow on either side of a fish’s brain. Much like the inner ear in humans, otoliths help fish hear, sense vibrations, and maintain balance and orientation. While certainly an essential little piece of anatomy for the fish, otoliths are nearly as essential to fisheries researchers. Continue reading →

Crystal Lake: Are Invasive Smelt on Their Way Out?

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Team members move a GELI (attached to a red air hose) into the water so it can be towed to its spot in Crystal Lake by boat.

Back in 2009, a team of engineers and scientists affiliated with the Center for Limnology had a crazy idea – they wanted to see if they could manipulate an entire lake to kill off an invasive fish without harming the lake’s native fish. (The usual method for eradicating an invasive species is poisoning the entire lake, killing everything, and then re-stocking it with native fish).

Team members attach the rubber air bladder to the metal frame of the GELI.

The group spent a summer up at Trout Lake Station and built from scratch a contraption that looked like a giant trampoline. It was a rubber air bladder stretched around a metal frame and attached to an air hose. They called it a gradual entrainment lake inverter, or GELI, for short. Four summers later, their experiment may be paying off. The smelt in Crystal Lake are acting very strange without the cold bottom layer of water they used to enjoy. Perhaps this will be the summer of their discontent….

Read more about the Mixing Project from the UW-Madison College of Letters and Science online newsletter.

Zach Lawson displays a rainbow smelt, target of the group’s ambitious eradication effort.

Without any context, Zach Lawson’s current endeavor seems downright morbid.

Lawson has spent the past two and a half years working on a project that, should things go according to plan, will kill thousands upon thousands of fish in a northern Wisconsin lake.

“The idea is to extirpate the entire population,” he said.

Read the full story at the College of Letters & Science “News and Notes” page.

Or watch Zach discuss the latest update from the shores of Crystal Lake:

And, for a longer history of the entire mixing project, you can watch this:

Finally, a few shots of gulls picking agitated smelt off the surface of Crystal Lake. (Normally during the hot summer days, adult smelt congregate in the cold deeper waters of the lake).

 

Limno in the Lab: Measuring Tiny Helmets and Microscopic Tail Spines

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Sure, we get to do some awesome fieldwork in the name of science,  but what we do with all those samples and data sets once we’re back in the lab is just as important.To give you a fuller sense of what it means to study limnology, we bring you a new series complementing our stories of Limnology in Action – Presenting: “Limno in the Lab.”

Jake Walsh puts a water sample of daphnia pulicaria under the microscope.

Jake Walsh may have spent his summer out on Lake Mendota collecting zooplankton samples, but his real work begins when he gets all those tiny animals into the lab and under a microscope. Walsh, a graduate student in the Vander Zanden lab, is currently looking at the dynamics between the algae-grazing zooplankton, daphina pulicaria, and one of its principal predators, the invasive spiny water flea.

Daphnia are an important source of food for aquatic invertebrates and Lake Mendota’s smaller fish and also one of the prime drivers of the “clear water phase” the lake experiences each Spring. But daphnia are under attack by a larger and formidable invasive zooplankton called the spiny water flea. Originally brought to the Great Lakes in the ballast tanks of ocean-going ships, spiny water fleas have steadily moved to inland waters, turning up in Lake Mendota (and surprising an undergraduate Zoology class) in 2009.

Undergraduate student, Carly Broshat, counts daphnia pulicaria samples taken from different depths in Lake Mendota to calculate their abundance at different levels of the water column.

But dahpnia pulicaria isn’t completely defenseless against its predators. For one thing, Walsh says, daphnia can change their range in the water column, dropping to deeper, darker waters to avoid sight-based predators like fish and the spiny water flea. Walsh currently has undergraduate student, Carly Broshat, working this summer on counting daphnia samples from different depths in the water column to see if daphnia heads down when spiny water flea numbers start to rise.

A sample of daphnia under the microscope (and projected on a computer monitor) allows Walsh to measure body size, as well as helmets and tail spines.

The microscopic creature can also grow hard “helmets” and “long” tail spines in response to heavy predation, features that make it less palatable for fish and, Walsh says, “harder to handle” for predators like the spiny water flea. Walsh has been looking for such changes in the daphnia’s morphology and is now exploring “whether those changes have anything to do with the [rise in abundance of] the spiny water flea.”

In Lake Mendota, “spiny water flea pops up in July and becomes abundant in September,” Walsh says, leading him to wonder if a similar rise in the proliferation of bigger daphnia with larger helmets and tail spines occurs as summer moves into fall. If so, it might be a sign that one of Lake Mendota’s most important zooplankton isn’t going down without a fight. Good news for both the food web and the water clarity of Madison’s largest lake.

Limnology in Action: Bug Pickin’

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“Alright. Who is ready to get messy?”

Students sift through trays of sediment and plants, picking out aquatic invertebrates

Zach Lawson’s question is greeted with incredible enthusiasm. It is all-hands-on-deck in the wet lab and, today, everyone is sorting bugs.

Ten undergraduate students crowd around two small tables, armed with small plastic sampling bottles and metal tweezers. They meticulously sift through plastic tubs of sand, muck and aquatic plants, looking for any small movements in the water. Suddenly, spotting the slightest flicker, a hand strikes, snatching up a very tiny red worm-like creature. The student yells “I have a diptera!” and Lawson quickly walks over to inspect and label the specimen. The students work for hours, leaving no leaf or rock unturned, and soon the lab is filled with bottles of invertebrates. Continue reading →

Smallmouth Bass: One Hazard of Fieldwork in Wisconsin Lakes

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Center for Limnology grad student, Gretchen Hansen, took this video from a past summer’s field season up in Vilas County. While we’ll honor the tradition of fishermen not sharing their favorite spots, it’s safe to say smallmouth bass are doing quite well in this particular lake.  Watch as one bass gets aggressive while Gretchen tries to collect rusty crayfish for her research. She says opportunistic bass would often grab her “samples” before she got a handle on them. Not this time, though!

We Have Liftoff on the Crystal Mixing Project

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A group gathers next to a deflated GELI on the shore of Crystal Lake to hear about the mixing experiment

Over the last three years a group of CFL students, professors and staff have worked on an experiment near Trout Lake Station that, they hope, will eradicate rainbow smelt and restore populations of native fish, like yellow perch, bluegill and largemouth to Crystal Lake. The experiment is finally ready to go.

As the early melt in March sent fishermen and boaters scrambling for their gear, members of the Crystal Lake Mixing project, also hurried to get their equipment in place.

“We flipped the switch [on Wednesday],” says Jordan Read, “and plan to leave it running. So far it’s looking good and things are moving along pretty well.”

PhD candidate, Jordan Read, explains how GELIs will mix the lake

Read, a PhD candidate in civil and environmental engineering at the University of Wisconsin-Madison, is one of the lead researchers on the project. Along with his colleagues, he’s built what looks like an armada of trampolines in the middle of Crystal Lake. They’re called “gradual entrainment lake inverters,” or GELI’s for short, and they’re hooked up to a bank of air compressors on the shore that, when controlled by a central computer, will send GELIs rising to the surface of Crystal Lake and sinking to the bottom throughout the summer.

You can read more and get real-time Crystal Lake data here.

The GELIs were designed to mix the entire water column and prevent Crystal Lake from stratifying this summer. That would keep the cold bottom layer of water from forming and, hopefully, make the lake too warm for the cold-water smelt to survive. The mixing won’t hurt native fish, since they’re all warm-water species.

Rainbow smelt are originally from saltwater habitats. They were brought to Michigan as forage fish for stocked salmon populations and soon escaped into the Great Lakes. Smelt became a popular table fish for some fishermen and researchers think they entered inland Wisconsin lakes via illegal stocking or in nets that hadn’t been properly cleaned.

Zach Lawson describes how the invasive smelt disrupt Crystal Lake's native fish populations

With an estimated smelt population of over 200,000 fish, a sudden die off could be quite obvious. If the experiment is successful, says Zach Lawson, a research assistant at Trout Lake Station, one sign may be dead smelt washing up on the beach.

“It’s a pretty common concern of people,” he says. “But you have to keep in mind that we are out there every morning before 9 am starting work, monitoring and maintaining GELI’s , and sampling. We’re out there every day, so we should be there to see anything that happens.”

And, Lawson says, it would be a short-term problem. A team of students and staff at Trout Lake Station are “on call” all summer to take care of any problems.

In other words, summer undergraduates should have shovels at the ready and wait for the call of – “Clean up on Crystal Beach!”

Watch the video of the creation of the Crystal Mixing project below: