By Shoshana Herndon
MSU College of Forest Resources

MISSISSIPPI STATE -- The lakes of the Mississippi Delta offer numerous recreational uses throughout the year. However, too many invasive aquatic plant species can create a less-than-optimal environment for fish and people.

A project in Mississippi State University’s Forest and Wildlife Research Center is looking at two different management practices to improve the habitat and increase public use of lakes for fishing, hunting and other recreational purposes.

Led by wildlife and fisheries professor Eric Dibble, the treatments include a controlled herbicide application and the use of grass carp. The four-year project seeks to selectively remove invasive aquatic species, both native and exotic.

“These small lakes are used fairly heavily for recreation -- both hunting and fishing -- and invasive species can block access to areas of the lakes,” Dibble said. “Additionally, the invasive species may have negative effects on the fisheries.”

Dibble is working with graduate student Matthew Spickard and John Skains, a biologist with the Mississippi Department of Wildlife, Fisheries and Parks.

“Our goal is to develop best management practices regarding chemical and biological aquatic plant control methods to restore habitat and facilitate fishery management goals in Mississippi Delta lakes,” Dibble said.

The state has other goals for the project, including access issues.

“Keeping ramps and piers open to the public is a priority for the state agency,” Skains said. “This project will address access and fisheries habitat, which is a win-win for everyone.”

Fishers want the biggest, healthiest fish, and the study will look at the best management practices for controlling native and exotic plant species to provide the proper amount of plant coverage for fisheries habitat, Skains added.

Removal of invasive plants is not an easy task, and it is often complicated by the diversity of plants in the lakes. Though the researchers seek to remove plant matter, the removal of too much plant coverage or a reduction in the diversity of native and exotic plants could negatively impact fisheries and the lake environment.

Skains, who led herbicide application for the project, said aquatic plants can be controlled using chemical, mechanical or biological means.

“This project will help in determining the best method for controlling aquatics and the effects these methods have on not only the fish population, but the whole lake ecosystem,” Skains said.

Known differences in the two applications include lag time for results and cost.

“Herbicides typically get faster results than grass carp and may control an invasive that is typically not favored by grass carp,” Dibble said. “However, herbicides can be expensive. Grass carp are typically cheaper in the short run than herbicides and can provide long-term control, but they are less selective.”

The study includes analysis of pre-treatment, treatment-year and at least two years of post-treatment data on six Delta lakes selected for their aquatic plant nuisance problems.

The project began in July 2007 with the gathering of pre-treatment data. During 2008, treatments were applied separately to different lakes to determine the effects of each on native plant species, water quality and the fisheries.

The herbicide, selected in coordination with the U.S. Army Engineer Research and Development Center and provided by the Aquatic Ecosystem Restoration Foundation and Cygnet Enterprises Inc., was applied by sprayer to two lakes. The Mississippi Department of Wildlife, Fisheries and Parks stocked two lakes with grass carp and two lakes were left for reference.

A similar four-year project was recently completed in a few Minnesota lakes, studying the effects of herbicide treatments for invasive plant control. The results revealed successful removal of most of the invasive plants and restoration of native plants and beneficial habitat for fish, Dibble said.

If the treatments in the Delta lakes show similar results by reducing the number of invasive plants, people may begin to have more regular access to the lakes.

“We are now collecting data from the six lakes,” Dibble added. “This data includes information about recreational use through volunteer random surveys conducted by the project team during routine visits to the lakes.”

Researchers involved expect recreational access and use to increase as plants are controlled and invasive plants eliminated. This will provide increased angler access to fishing areas and possibly improve gamefish populations.