By Forrest Adams

Elbows rested on the tables, and backs lined the walls in the American Legion conference room Tuesday night as a large crowd gathered for Dr. Peter Sorensen’s talk about carp.

The University of Minnesota fisheries professor’s audience included interested and concerned lake residents, city officials, an interviewer for public radio and state Rep. Joe Hoppe.

Sorensen is developing a management plan to control common carp in Lake Riley, Lake Susan and Rice Marsh Lake. He said Chanhassen’s Lake Susan has probably the best-studied carp population in the world, adding: “The carp are running wild in this lake.”

Seize the carp: University of Minnesota Fisheries Professor Peter Sorensen in the Chanhassen American Legion

With the help of local volunteers, students and DNR staff, he removed carp from the lake for study purposes, and the average age of the fish so far has been 20 years old. The group has even removed a fish from the lake that was 53 years old.

Carp live long and prosper once they’re old enough, Sorensen said, but life is hard when they’re minnows.

“They reproduce every year like gangbusters,” he said, adding that while they leave behind billions of eggs, he’s been surprised to learn that “it’s a rare event that a larval carp lives.”

“Most years they don’t survive,” he said. “These are not iron-clad creatures.”

However, when winter is the coldest, and there’s a lake freeze that drives oxygen out of the shallow waters, thus killing off predatory fish, the carp minnows survive, he thinks.

“We obviously can’t control the winters,” so what Sorensen intends to do is develop a sustainable carp control project in which adult carp are removed, re-infestation is eliminated, spawning and/or survival of young carp is eliminated and all three actions are adjusted as needed.

He called it “systematic, rigorous carp removal.”   

This is not about totally eradicating common carp, he said, but about decreasing their numbers to more manageable levels. Sorensen hopes at the end of three years to have developed and implemented barrier techniques that prevent carp from migrating between lakes, as well as strategies that suppress their proliferation. He intends to eventually develop “a guidebook” for managing the fish that can be used nationwide.

In addition to conducting the local study in the Riley Purgatory Bluff Creek Watershed District, Sorensen and fellow Dr. Przemek Bajer are conducting a common carp study in Hutchinson in several lakes that are similarly connected to those in Chanhassen.