Carp removal part of a three-year project to improve water quality of Lake Nokomis

Carp from research project on Lake Nokomis

Above: This carp was tagged with a radio device in 2017 so that researchers can monitor its location. Below: Carp caught with a box next on Lake Nokomis.

People may notice a lot of activity on and near Lake Nokomis in the coming weeks. Contractors are testing box-netting techniques that may play a part in long-term control of invasive carp at Lake Nokomis. Much of this work is scheduled to occur late at night and early in the morning. Carp at Lake Nokomis have been getting corn regularly from a feeding station, which will be used in tandem with the box net to remove carp at various times during the open-water season.carp caught with a box net

In addition, if conditions are favorable, large-scale removal of invasive carp will also occur using a seine net. This removal process would occur as lake temperatures drop and carp begin schooling – or forming a tight aggregation. The location of schools can be determined by carp that have been tagged with radio tracking devices. Schooling, a behavior of many fish species, provides the best opportunity to remove a large number of carp at one time.

Carp removal is part of a three-year project to improve Lake Nokomis’ water quality by reducing the lake’s population of this species. Research conducted during the project will also guide the development of an Integrated Pest Management plan for this invasive species. The goal is to keep the carp population low enough so that the fish don’t affect water quality, and large-scale removals are infrequent or even no longer necessary.

Below are details on both types of removal processes, as well as the Lake Nokomis Carp management research project.

carp removal with a box net

Carp are lured into a box net with regular feedings of corn at a bait station.

Details on box netting

Due to the feeding schedule of carp, this type of netting may occur very early in the morning.  Contractors may be working from boats or from shore, using headlamps. Testing and modifications have been made to the box net to minimize the chances of sport fish being caught. Any sport fish or radio-tagged carp caught during the process will be returned to the lake.

Details on seine netting

If conditions are right for seine netting, three large boats with motors will use a 3,000-foot-long seine net to encircle and capture the fish. Once they are transported to shore, the fish will be weighed, measured and examined, with any sport fish or radio-tagged carp getting returned to the lake. The remaining carp will be transferred off-site by a semi truck, to be sold at one of several markets. Paths that cross the lake’s boat launch may be blocked for short periods of time so that the boats can load, unload or transfer carp to the truck. This type of netting generally occurs between 8 a.m. and 5 p.m.

telemetry device used to track carp locations on Lake Nokomis

Using a telemetry device, researchers track the locations of tagged carp to learn when and where the population is aggregating for the winter.

Why do we need to manage the carp population?

As a bottom-feeding fish, carp are capable of disturbing the beds of lakes, which releases excess phosphorus into the water. This diminishes water quality by creating algal blooms. Carp also eat and uproot vegetation, which can destroy a lake’s aquatic plant community. Lakes with an overgrowth of carp typically have high phosphorus concentrations, low water clarity, and little to no aquatic plant growth.

The MPRB was awarded funding for a carp management research project in 2016, after staff observations and preliminary estimates of the carp mass in Lake Nokomis, determined by electrofishing, indicated that the carp population had become excessive. The project goal is to apply new research to a proven approach to manage the carp population, and develop long-term practices to improve the lake’s water quality. Visit the project page to learn more.

Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources.

The Trust Fund is a permanent fund constitutionally established by the citizens of Minnesota to assist in the protection, conservation, preservation, and enhancement of the state’s air, water, land, fish, wildlife, and other natural resources.

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