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Grant feature #2: Can bubble barriers stop carp?

Can bubble carriers stop carp?

Carp harvesting efforts have been underway for years in the Yahara River watershed, but more could be done to manage the population of invasive fish. In this month’s Clean Lakes Grants spotlight, we’re sharing the efforts of our partners at Friends of Pheasant Branch Conservancy, who are ready to tackle the challenge.

Friends of Pheasant Branch Conservancy is a not-for-profit organization devoted to protecting and restoring Pheasant Branch Conservancy on the northwest shore of Lake Mendota. Through a $8,750 grant awarded for 2018, the group will evaluate the feasibility of installing a new carp “bubble barrier” system on Pheasant Branch Creek to ultimately craft a recommendation and action plan for implementation.

Common carp have been present in the Yahara lakes since they were introduced in the 1890s. In their search for food, carp will uproot native vegetation, altering habitats and reducing water clarity. As the carp disturb the nutrient-rich soil of the lakebed, phosphorus is introduced back into the water, feeding harmful cyanobacteria blooms.

To evaluate the potential to use carp barriers in the Yahara watershed, the Friends at Pheasant Branch will compile and review data from past studies, collect their own data on barrier effectiveness and environmental impacts, and analyze possible sites at Pheasant Branch Creek. The Friends hope to replicate successful use of similar barriers in Green Lake and Beaver Dam Lake.

The barrier being studied works by creating a wall of bubbles that blocks carp migration without obstructing other wildlife within the lake or stream. If found to be feasible and effective, the carp barrier could improve water quality in Pheasant Branch and be replicated in other sensitive areas throughout the Yahara lakes. Potential benefits include reduced phosphorus concentrations in the water column, reestablished native vegetation, improved boating access, and cascading impacts on water quality in Lake Mendota.


Understanding the impact of carp

“My Really Truly Stream Monitoring Story”

Shared Summer 2017 by Lloyd Eagan, Friends of Pheasant Branch Board Chair
Clean Lakes Alliance Community Board Member and former Chair

For the past three years, I have led a Citizen Stream Monitoring Team that samples Pheasant Branch just north of County Road M and above the outlet of the creek to Lake Mendota. Shell Goar and Pat Kandziora have been my able assistants. We sample the stream for dissolved oxygen, take a grab sample for phosphorus, check on the automatic thermometer tidbit we deployed in the stream, and measure the transparency of the water in the Creek with a turbidity tube.

I love checking on the water quality in the creek and answering the inevitable questions we get from the nearby trail users. “JUST WHAT are you doing?” It is fun to carry the equipment, take care of a dissolved oxygen monitor and baby a water sample on ice while I take it to the lab at the Madison Metropolitan Sewerage District.

Usually, we find the stream is slow moving but, despite a rather soft bottom, dissolved oxygen levels have been good and water clarity is usually excellent. On June 5th this year, we found a very different looking stream.

It had not rained in the previous few days, so we were surprised to find the water looking cloudy. I checked the dissolved oxygen. It measured 7.2 mg/L, which was down from the elevated level of 13.9 mg/L we had measured on May 8th.

Next, I took the water sample for the lab. It looked a little cloudy.

The real surprise was the transparency tube measurement. Usually, at this site, we take the obligatory two samples. I wade out into the stream twice and fill the 120 centimeter transparency tube full. Then on the bank we look down the tube to see if we can see the black and white on the mini secchi disc on the tube bottom. Most of the time, we see the black and white right away and our average transparency is 120 cm.

This time, we couldn’t see the black and white at the bottom of the tube. So I had to let out water from the bottom of the tube until Pat could see the black and white. Our average of two tries was only 51.5 cm. We were puzzled and concerned. What happened to our sparkling clear creek?

Then we heard some thrashing and splashing upstream of us. We looked upstream and saw at least six big carp rolling around. They were stirring the whole bottom of the stream up. This was the first time we had seem them there in the three years of monitoring. Their presence definitely correlated with the poor water clarity we measured.

It has been suggested to me that hunting carp with a bow and arrow works well. I’m not sure about that, but I would be happy to see the carp removed and our stream run clear again.


Since Lloyd shared her story with us last summer, the Friends of Pheasant Branch along with Clean Lakes Alliance have studied this new way to keep carp from entering sensitive natural areas.

Can bubble barriers stop carp? Clean Lakes Alliance is excited to invest in this new study, and looks forward to working with Friends of Pheasant Branch Conservancy on innovative approaches to lake improvement.

Visit our carp page to learn more about the impact of this invasive fish on our lakes.

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