Managing Invasive Carp in the Rice Creek Watershed District
A walk-through of RCWD Carp Management Program. Focused on improving water quality and clarity in the watershed.
What are Common Carp?
Common carp (Cyprinus carpio), native to Eastern Europe and Western Asia, was first introduced in the United States in the late 1800’s. The introduction was purposeful, carried‐out by the U.S. Commission of Fish and Fisheries, and indented to promote a fishery for sport and food sources. Since introduction, common carp spread quickly across the United States; most states now have reproducing populations.
In Minnesota, common carp are widespread and often found in high abundance. Several other species of carp have also been introduced to the United States and Minnesota – for example, silver carp (Hypopthalmichthys molitrix), known for their jumping ability, and bighead carp (Hypopthalmichthys nobilis).
Why are Common Carp a problem in RCWD?
Common carp negatively impact native ecosystems such as lakes and rivers, native fish populations, and water quality by how they feed (uprooting and killing native aquatic plants) and spawn. When there is a lot of carp in a water body, the amount of native plants in the water declines, nutrients (phosphorus) and chlorophyll‐a (algae) increase, and water clarity decreases.
Destroy Native Plants
Carp kick up or "root in" lake sediments (aka the lake bottom), this pulls out or kills native plants that would otherwise stabilize lake sediments. Carp also increase water turbidity (cloud the water with lake bottom sediment) and reduce sunlight penetration which decreases the growth of submerged aquatic vegetation.
Increase Nutrients (phosphorus) and Chlorophyll‐a (algae)
They're bottom-feeding fish that disturb sediments while searching for food, this releases phosphorus and other nutrients trapped in the sediment, making them available for algae growth. They also uproot aquatic plants, which reduces their ability to absorb excess nutrients and stabilize sediments. The increased nutrients from disturbed sediments, combined with less native vegetation, lead to algae blooms and higher chlorophyll-a concentrations.
Compete with Native Fish Populations
Their aggressive feeding habits and ability to tolerate various water conditions give them a competitive edge over native species. By uprooting aquatic vegetation this results in the loss of spawning grounds and nursery areas for native fish.
Learn More
You can learn more about common carp and their negative impacts of ecosystems at the Minnesota Aquatic Invasive Species Research Center. Link below.
Our Carp Management Goals
It's not economically feasible to eradicate common carp from the Rice Creek Watershed (it may never be generally feasible given the circumstances.) The management goal for common carp is to attain and maintain a population density below the threshold of approximately 100 kg/ha (90 lbs/acre), where they won't negatively affect water quality.
The actual threshold may vary across different water bodies, and positive water quality results may be achieved at slightly higher or lower carp densities (it all depends on that specific water body).
Management of common carp alone will not always fully restore lake water clarity. RCWD may need to do other activities around the lake as well as in it to successfully restore the water quality.
Approaching RCWD management threshold goal in 2022.
RCWD Carp Management Plans
Long Lake / Lino Chain of Lakes System – Carp Management Plan
Program Goal: Achieve MN State Water Quality Standards in Long Lake and the Lino Chain of Lakes. Long Lake (deep lake) standard: 40 μg/L total phosphorus, 14 μg/L chlorophylla, and 1.4 meters Secchi depth. Lino Lakes (shallow lake) standard: 60 μg/L total phosphorus, 20 μg/L chlorophyll‐a, and 1.0 meters Secchi depth. Overall Program Goal: Reduce and maintain the common carp density in Long Lake below the ecological impact threshold of 100 kg/ha.
RCWD Common Carp Management Plan
Program Goal: Attain and maintain a population density below the threshold of approximately 100 kg/ha (90 lbs/acre).
Carp Management Tools We Use
The Integrated Pest Management (IPM) approach will provide the overall framework for managing common carp in the RCWD.
IPM has several key components for successful implementation. Continue scrolling to learn more about each component.
1. Monitoring and Modeling
- Estimating the Abundance of Adult Carp
- Detecting and Estimating the Abundance of Juvenile Carp
- Tracking Carp Movement (immigration, emigration, and seasonal migration)
- Lake Monitoring Data
- Modelling Carp Population Dynamics
2. Inducing or Increasing Adult Mortality
- Removing Adult Carp
- Introducing Lake‐wide Toxin (rotenone)
- Introducing Toxins with Bait
- Pathogens
3. Suppressing Recruitment
- Blocking Migration of Adult Carp
- Blocking Migration of Juvenile Carp
- Aeration
- Genetic Engineering
4. Adaptive Management Approach
We use an adaptive management approach in this program. It allows us to be flexible and open to new ideas and strategies. If something isn't working and providing wanted results, we have the ability to adapt and change what we are doing in regard to carp management.
Future technologies and management tools may provide new opportunities to improve the overall program efficiency, effectiveness, or reliability.
Carp Management Project Tour
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Johanna Creek Common Carp Barrier Project
The Johanna Creek Carp Barrier is one of the multiple projects within the Long Lake – Lino Chain of Lakes Carp Management Program. This project uses a physical barrier in Johanna Creek in the city of New Brighton to prevent the migration of common carp out of Long Lake through Johanna Creek to the southern parts of the watershed for spawning.
The barrier creates an opportunity for adult carp removal, as migrating carp swim and stop at the barrier RCWD can then remove those carp. RCWD plans to remove up to 4,000 lbs. of carp in the first year of operation, eventually reducing overtime as the population is kept in check to a long-term average of around 2,000 lbs. of carp.
These barriers have been proven to work and used successfully in two other locations within the RCWD. With a life expectancy of 25 years, these barriers provide the watershed with long-term common carp management with minimal maintenance.
**Important Note: Native fish are let past the barrier during numerous field checks and carp removal. The barrier is only closed during migration, not all year long. Native fish populations and quantities are low in this location.
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Rondeau Lake Fish Barrier
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RWJD1 Fish Barrier
"Although natural resources managers have long known that carp have a negative impact on lake ecology and water quality, recent research has shed light on the magnitude and mechanisms of their impact. Additionally, new management tools have been developed and tested by the University of Minnesota and their many partners. With this information and promising new tools, common carp management has the potential to drastically improve ecological function and water quality in many lakes around the Rice Creek Watershed and Minnesota."
~Rice Creek Watershed Common Carp Management Plan
Carp Management Photos Throughout the Years at RCWD
Implications for Not Controlling Invasive Common Carp in RCWD
Not controlling invasive common carp in lakes can have several negative implications for both the ecosystem and human activities. Common carp (Cyprinus carpio) are highly adaptable and can thrive in a wide range of aquatic habitats, making them a particularly troublesome invasive species.
Here are some of the key implications of not controlling common carp in lakes:
- Altered Ecosystem Dynamics: Common carp are bottom feeders that uproot aquatic vegetation and disturb the substrate, leading to changes in the structure and composition of native aquatic plant communities. This can negatively impact the habitat for other fish species and aquatic organisms.
- Water Quality Issues: Carp are known to stir up sediments, releasing nutrients and other pollutants into the water column. This can lead to decreased water quality, increased turbidity, and higher nutrient concentrations, which can fuel algae blooms and disrupt the balance of the aquatic ecosystem.
- Impact on Native Fish Species: Carp can outcompete native fish for food and habitat, leading to declines in native fish populations. Additionally, they can consume the eggs and larvae of native fish species, further reducing their numbers.
- Loss of Biodiversity: Invasive common carp can have cascading effects on the entire food web of a lake. By altering the composition of native aquatic plants and impacting native fish species, they can lead to a loss of biodiversity in the ecosystem.
- Recreational and Economic Impacts: Carp can negatively affect recreational fishing opportunities. They are often considered a nuisance by anglers because they compete with desirable fish species and are not typically targeted for sport. This can have economic implications for local communities dependent on tourism and recreational fishing.
- Infrastructure Damage: Carp have been known to damage submerged infrastructure such as dams, bridges, and water control structures by digging in the sediment and destabilizing the substrate. This can lead to increased maintenance costs and potential safety hazards.
- Increased Management Costs: Over time, if common carp populations are not controlled, the costs associated with managing their negative impacts can increase significantly. Eradication or control efforts may become more difficult and expensive as carp populations grow.
- Spread to New Water Bodies: If not controlled, common carp can easily spread to new water bodies through natural waterway connections, human activity, or flooding events. This can lead to the invasion of previously unaffected lakes and rivers.
To prevent these negative implications, it is often necessary to implement control measures such as fish removal, habitat restoration, and public education to prevent the introduction and spread of common carp in lakes and rivers. Early detection and rapid response are critical in managing invasive species to minimize their impact on aquatic ecosystems and associated human activities.
