‘Amazing’ Progress Reported on Keeping Carp Out of the St. Croix

Researchers have discovered new ways to stop the destructive non-native fish.




8 minute read

Sunnyside Marina manager Rick Chapman
Rick Chapman with Sunnyside’s wash water water recycling system.

Editor’s note: Rick Chapman is general manager of Sunnyside Marina on the St. Croix River in Stillwater, MN. Rick and Sunnyside are leaders in the Clean Marina Program, which St. Croix 360 covered in 2014

Rick attended the Minnesota Invasive Carp Forum on March 10 and wrote a report for the Midwest Marina Association, where he serves as president. St. Croix 360 is pleased to publish an edited version of that report below. 

Invasive bighead carp (Photo via U.S. Fish and Wildlife Service)
Invasive bighead carp (Photo via U.S. Fish and Wildlife Service)

This the fifth year I have attended this forum. In the first year there was nearly no coordination between the different groups making presentations and there was no particular plan to stop the invasive carp from establishing themselves in the Upper Mississippi, Minnesota or St. Croix Rivers. Fast forward to today where all of the groups are working together to come up with a plan or several plans to stop these invasive carp. It really is quite amazing.

There were several presentations made during this forum. Many of the presentations were very technical. In my summary, I will attempt to take my five pages of notes and try to make some practical sense from all of this information.

Invited Guest Speaker Quinton Phelps with the Missouri Department of Education:

Quinton was speaking about what is being accomplished at Lock and Dam No. 19, which is located near Keokuk, Iowa. This structure is high enough to create a barrier to stop the carp from moving north. Although there have been many catches of bighead carp north of this structure, it is still believed that there are no reproductive fish north of this structure and if there are reproductive fish, they are limited. It is also believed that any invasive carp moving past this structure are moving through the actual lock, but not through the spillways. The locks and dams below No. 19 allow these fish to move freely whether the lock is open or closed.

[Tweet “They compete with the natural fish species in the watersheds and they have no natural predators.”]

The invasive carp have had a devastating ecological effect on the Mississippi River and tributaries below Lock and Dam No. 19. The silver carp have a high growth rate and a life expectancy of about six years, whereas the bighead carp grow slower and live longer, from twelve to fifteen years. They compete with the natural fish species in the watersheds and they have no natural predators. Silver carp, which are the jumping carp we have all seen on the Illinois River, can and have destroyed fishing and recreational boating in watersheds where they have been established and are flourishing. Sturgeon, paddlefish and catfish seem to be co-existing fairly well with the invasive carp. Other game fish are not.

In 2014, 10 bighead carp and 15 Silver Carp were tagged tagged for tracking purposes below Lock and Dam No. 19. Tracking equipment was installed at each end of the lock and on some barges that pass through the lock. In 2014 there were 10 of these tagged fish tracked within one mile of the structure. In 2015 there was confirmation that 1 of the tagged fish made it through the lock structure. These fish are capable of swimming 400 miles in seven days.

The invasive carp have a long spawning period, from mid-May to mid-September. If harvesting is considered as a control method, it is estimated that 30 percent of the adult fish would have to be harvested by commercial fishermen in order to control the population below lock and dam number 19. These fish would have to be harvested before they reached their reproductive age. The people in the area of Lock and Dam No. 19 are just now become more receptive to other types of control measures, like noise deterrents, bubblers and lights. They have received funding to tag another 300 fish in 2016 and 2017.

In a related and totally bizarre coincidence, while we are trying to figure out a way to stop these invasive carp, China is trying to figure how to re-populate their Yangtze River, which has been over-fished.

[Tweet “While we are trying to stop invasive carp, China is trying to re-populate their Yangtze River.”]

Nick Frohnauer, Minnesota DNR:

The DNR continues its efforts to sample for invasive carp. They have been targeting Lake Pepin near Lake City. The most effective way to find the carp is through commercial fishermen and their nets. The carp do not feed on fishing bait so it is unlikely anyone will catch them with a fishing pole and a hook.

A total of five fish were caught on the St. Croix River. The DNR was only able to get their hands on one of these fish. The other four were taken and eaten by the fishermen who caught them.

The U.S. Fish and Wildlife Service is still doing eDNA testing each year. This testing, even when it is positive, does not necessarily mean the fish are present. Their eDNA could be brought to the river by birds.

The closure of the lock and dam at St. Anthony Falls has allowed the DNR to focus more of their efforts on the Minnesota and St. Croix Rivers. More effort has been placed on the bighead carp and silver carp although the black carp and grass carp are still a concern.

[Tweet “Closing the St. Anthony Falls lock has allowed the DNR to focus more efforts on the St. Croix River.”]

The grass carp can still be purchased in Iowa even if they can reproduce. In Minnesota, grass carp can be purchased, but only if they are incapable of reproduction. It is believed that the grass carp caught in the Minnesota River in 2015 was brought in by someone using the fish to clean up vegetation in a pond. This is a popular use of the grass carp. 

Adam Kokotovich, University of Minnesota:

Adam brought the group up-to-date on a two-day “Invasive Carp Risk Assessment” meting that took place over two days on March 8 and 9, 2016. The meeting was attended by host of parties including, but not limited to, the Minnesota DNR, The National Park Service, the Army Corps of Engineers, The US Fish and Wildlife Department, the US Geological Survey, the University of Minnesota, and others.

The idea behind this meeting was to assess the risk the invasive carp actually have on our waterways before determining the best course of action to slow them down or stop them. Is it possible for our rivers to look like the Illinois River? Some people in attendance at this meeting want to stop the carp at all costs, without truly knowing the outcome of their efforts. Could there be unexpected consequences?

Two issues that came up through these discussions was the idea that plans could possibly be made from apathy or from fear. These two sides are best illustrated by the opposing views to press releases. Some people want each carp that is caught in the upper Mississippi, Minnesota or St. Croix River to be front-page news, while others feel if there is too much publicity, the public will simply become apathetic towards the issue.

The results of this “Risk Assessment” will be available soon.

Dr. Peter Sorensen, University of Minnesota:

Dr. Sorensen was granted $1.5 million by the state of Minnesota in 2012 to study invasive carp. These funds will run out in 2017. Through his research, Dr. Sorensen has determined that Lock and Dam No. 5, located near Winona, Minnesota, is the best place for the carp to be stopped or slowed down. The structure is similar to Lock and Dam No. 19.

[Tweet “Dr. Sorensen has determined that Lock and Dam No. 5 is the best place for the carp to be stopped.”]

In 2015, Dr. Sorensen was able to identify the invasive carp’s ability to swim. It was determined that although they are good long distance swimmers, they are not particularly strong swimmers. This means that the spillways of the dam can be adjusted in a way to keep the invasive carp from getting through. The Army Corps of Engineers has agreed to make the adjustments to the spillways.

Dr. Sorensen has also determined that the invasive carp, like the common carp, have exceptional hearing and can be deterred by sound. Native fish do not have this same sense of hearing. Dr. Sorensen will install sound barriers at the mouth of the lock and inside the lock to keep the invasive carp from entering the lock when it is opened. This work will be accomplished in 2016. (More about this project will be published on St. Croix 360 soon.)

Allen Mensinger, University of Minnesota – Duluth:

Allen updated the group on his efforts to determine how sound affects the behavior of the invasive carp. Much of this research was used by Dr. Sorenson. Allen started this project in 2014. He wanted to determine what made the silver carp jump. He determined they jumped from the hearing the sound of outboard motors. He used this sound in his experiments.

His first experiments were done in a cement pond that was built outdoors. He placed speakers at each end of the pond and studied the behavior of the carp when sound was introduced at one end. The carp moved to the other end. He then turned the sound off on the original end and turned it on at the end the carp were now inhabiting. The carp moved to the other end.

Allen calls this his “Ping-Pong” experiment.

He then moved on by adding a barrier in the center of the pond with an opening in the center. He placed the speakers on one side of the barrier with the fish on the same side. When the sound was turned on the fish would not move through the barrier. In the same experiment, native fish were introduced and the sound did not affect their movements.

In 2015, Allen moved this experiment to an outdoor natural pond and found the same results. He also experimented with the use of sound to herd the fish in one direction. This herding of the fish was also successful.

In 2016, Allen has plans to attempt to herd fish directly into nets so they can be captured. Allen also determined that in order for the sound to be effective, it has to be turned on and off. If sound is left on continuously for 48 hours the fish simply become used to the sound and it no longer affects them.

Phil Larson, Minnesota State University – Mankato:

Phil introduced three of his graduate students who have been working on mapping the Mississippi River to determine how the river has changed its flow and how this information can help to determine where the invasive carp may live and reproduce in the river.

The researchers had analyzed the river channel and floodplains changes over time through historic records stretching back to the Great Depression. Using high-tech methods, they also mapped the modern depth of the river and other technical details that contribute to creating carp habitat.

Jon Amberg, US Geological Survey, Lacrosse, Wisconsin:

Jon is working on the chemical compound that can be used to eliminate the invasive carp (the “Kill Pill”). A chemical has been created that seems to kill the invasive carp without harming the native species. The next problem was how to deliver the chemical. Since the invasive carp are primarily plankton eaters, it was determined this would be the best way to deliver the chemical. Tests have been done with some success, but more testing is needed. In some of the testing last year the delivery method clumped up. It is important that the chemical disperse in small quantities so the invasive carp will ingest it and die. There is more testing being done in 2016. 

Byron Karns, National Park Service:

Byron did a brief presentation on a study on the St. Croix River to determine if the invasive carp are having an adverse effect on lake sturgeon in the river. This testing is being done near the Allen S. King power plant in Bayport where several bighead carp have been caught. It was noted that the sturgeon being tested have shown signs of less muscle mass, but it is inconclusive whether the invasive carp are a factor or if there are other issues involved.

St. Croix River Food Web, National Park Service

This study was conducted to see the differences in the food chain between the Mississippi River and the St. Croix River. It is hoped that this study can help to determine if the St. Croix is a good habitat for the invasive carp or not. Of course we hope the results show that the St. Croix River is not a good place for these carp to reproduce and flourish.

Take Action

If you boat or fish on the St. Croix River…

  • Do not release bait and dispose of unwanted bait in the trash.
  • Be on the lookout for Invasive Asian carp; if you catch one contact the Minnesota DNR at (651) 259-5100 or the Wisconsin DNR at (608) 785-9012.
  • Volunteer to share information with other boaters. To learn about ongoing volunteer efforts and programs on the St. Croix River, please contact Angelique at the St. Croix River Association (angeliqued@scramail.com or 715-483-3300).


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‘Amazing’ Progress Reported on Keeping Carp Out of the St. Croix