Monday, October 12, 2015

Carp Talk – Keeping Tabs on Carp in the Phalen Chain

Jordan Wein measures carp caught in Kohlman Lake box nets.
Photo credit: Anita Jader

By Bill Bartodziej

Over the last six years, we have made substantial progress in understanding the common carp population and ecology in the Phalen Chain of Lakes. We have learned that carp densities over 90 pounds per acre typically result in negative impacts to lake water quality. This has become our long-term carp management target. 

We also discovered that carp actively spawn in the main lakes, but bluegill sunfish consume most of their eggs. However, adult carp in small lakes, ponds, and connecting wetlands can be very successful in producing young carp if bluegill are absent. So if we want to keep carp at low levels in the main Chain of Lakes, we must turn to managing these small connected waters. 

We have located the key spawning areas that are connected to the Chain and have been actively working to eliminate the juvenile carp in these systems (e.g., Casey Lake, Markham Pond, Owasso Basin, and Kohlman Basin).
This map shows key targeted areas in the Phalen Chain where carp management
has been in progress in the past few years.

This year the Watershed District contracted with Carp Solutions, LLC, to conduct carp survey work in connecting ponds and small lakes and to trap adult carp in the main Chain of Lakes. District Natural Resources staff have been working closely with Dr. Przemek Bajer of Carp Solutions and his staff. This effort is progressing very nicely and the results have been encouraging.

Adult Carp Management

We will continue to reduce the adult population in the main Chain of Lakes over the next several years. At the beginning of this year, we estimated that there were 2,900 adult carp remaining in the Phalen Chain. Through summer box-netting (images below), we have been able to remove 500 carp to date. This is over 17% of the remaining adult carp population. Although this not glamorous work, summer box-netting has proven to be a very useful carp management tool. For the purpose of systematically reducing the carp population at a reasonable cost, this seems to be the most effective tool at this time.

Over the last several years, we have reduced the adult carp density by over 60 percent, from 158 pounds per acre to 55 pounds per acre (average biomass for Kohlman, Gervais and Keller Lakes). We are now well under our 90 pound per acre management goal. The captured carp are making their way to the Ramsey County Correctional Facility greenhouse where compost is being produced. A good portion of this compost material will be used to grow native plants at the nursery.

Cracked corn is used to attract carp into the box nets. Natural Resources Technician, Simba Blood,
and interns, Thea Evans (left) and Carrie Taylor (right), bait trap nets.

In addition to being an effective tool in carp removal, the box netting effort suggests that young carp are not common in the Phalen Chain. So far we have not captured a juvenile carp in the netting operation. All the fish have been big adults. These results support the idea that substantial carp recruitment (young fish moving into the adult population) has not taken place in 2014-15 in the main Chain of Lakes. This is very good news!

Herding captured carp into the corner of the box net for removal.

Keeping Tabs on the Nursery Areas

Trap nets were set to capture small fish in carp nursery areas in the northern part of watershed. Good news! No young carp were sampled in Markham Pond, Casey Lake and Willow Lake. Additionally, other survey work suggests the absence of adult carp in these systems. This confirms that we are making progress in effectively managing these systems and eliminating the threat of large numbers of juvenile carp moving into the Chain.

Trap nets set in Markham Pond. No carp were found.

Kohlman Basin Management

Kohlman Basin is a ponding and storm water treatment area that receives water from Willow and Kohlman Creeks; water exits and makes it way to Kohlman Lake. The main basin is located on the south side of Beam Avenue between Highway 61 and Hazelwood Street across from Costco. Previous survey work (Justine Koch’s thesis study, U of MN) suggested that there were a few hundred adult carp, and surprisingly, some gamefish in this Kohlman Basin system. 

The drawdown of Kohlman Basin, a wetland complex located along Beam Avenue in Maplewood.

This year, only one young carp was found in a small connecting wetland just to the north of Kohlman Basin (we did not survey for adults). Although only one juvenile carp was netted, this is an indication that carp are successfully reproducing in this system. Thus, this confirms the necessity to manage these systems to minimize the risk of a large year class of juvenile carp being produced.

Stephen Theis, RWMWD Natural Resources Intern,
sets up a net at Kohlman Basin outlet before the drawdown

On October 1st, watershed staff opened the outlet and began to draw down Kohlman Basin and the connecting wetlands to the north. Our main objective is to drain most of the water and then net carp in the remaining pool. We will preserve all the gamefish in the system. After our fall harvest, the outlet will be closed, and the basin will be filled before winter. We will certainly keep you updated on this carp management effort.

The drawdown of Kohlman Basin in progress. View is facing the outlet on the west side.

Keep your fingers crossed that the Kohlman Basin drawdown is successful. Rest assured our work with carp is not over yet. The Watershed District intends to comprehensively manage carp over the long-term in the Phalen Chain of Lakes. Stay tuned to your local dial for the next installment.

"Working on removing carp from the Phalen Chain of Lakes! This haul from Lake Gervais
was 46 adult carp, or as we prefer to think of it, 50 million future fish."

- Simba Blood, RWMWD Natural Resources Technician


“A scrapbook of carp photos isn’t complete without a shot of
Jordan Wein’s latest catch from a box net.”
   - Sage Passi

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