For years, wildlife agencies have known grass carp exist in the Sandusky River, a tributary of Lake Erie. Consequently, this has been a concern for several state, federal and international agencies.
For the second successive year, various agencies were on the Sandusky seeking the invasive species as well as data on it, which can be used in the future to determine the method of how to control the fish in western Lake Erie.
This is not the same sterile grass carp farm pond owners are allowed to use to control vegetation. The Ohio Division of Wildlife (DOW) has also used these triploid species of the grass carp, also known as the white amur. They live in the Amur River in the extreme climates of Siberia and are one of four species of Asian carp.
The diploid version can reproduce and likely entered rivers via high water levels as they escaped from private ponds that owners stocked in the 1970s before the sterile grass carp were approved for use.
Since they are in waters now, the key is to find how best to control them. That’s why research is happening on the Sandusky as well as the Maumee River.
There are plenty of unknowns about grass carp, according to Rich Carter, executive administrator for fish management group at the DOW. It is known they do eat vegetation, but not known how much they may eat in a river like the Sandusky. They are a concern because vegetation is important young fish and young waterfowl.
On a short morning trip on the Sandusky with Travis Hartman, a Putnam County native, who is the DOW’s Lake Erie Program Administrator, and John Windau, DOW media specialist out of Columbus who used to work at the Wildlife District Two office in Findlay, we observed a section boats were working near Memory Marina.
Hartman explained preferred grass carp habitat involves, “branches, logs or timber in the water near a forested bank line.” High water flow gets them moving to spawn and they spawn in areas that walleye prefer to spawn. There was plenty of river flow (more than researchers preferred) after a couple days of heavy rains. Although they wanted high flow, such a high flow left quite a bit of debris floating down the river as well.
There were 16 boats in the operation with four each to a section. Two netting boats and two electrofishing boats were in each section. The section we observed had DOW and Michigan Department of Natural Resources netting boats and Michigan DNR and Canadian Department of Fish and Oceans electrofishing boats. The Trammel nets are placed in what appears to be grass carp habitat.
As Hartman explained, the netting boats put out Trammel nets and once there were in place, the electrofishing boat trimmed its motor and cruised over the nets to try and herd fish into them and “shocking” whatever fish might come to the surface where they would be netted. The turbidity of the water made it more difficult to shock since visibility is lessened drastically.
Trammel nets are one of the most complex, yet efficient gill nets that are in popular use worldwide. Unlike single wall gill nets, which will catch a narrow range of fish sizes, a Trammel net will catch a wide variety of fish sizes. Essentially, a Trammel net is three layers of netting tied together on a common floatline and common leadline, according to to Miller Net Company.
We saw quite a bit of fish activity in the net before the electrofishing boat began its path over it. During this period, Hartman received a call that a grass carp had been taken near Fremont in the Brady’s Island area. That fish was to have had a tag placed and can be tracked like other tagged grass carp via acoustic telemetry.
Five tagged fish were found Sunday near Fremont via a Michigan State University project, indicating they were spawning since a group was discovered. Hartman said grass carp eggs are like striped bass eggs.
“They need buoyancy and current to hatch,” he said.
Working with eggs is part of the research work that the University of Toledo and U.S. Geological Survey supply.
Other agencies working on the project besides those already mentioned are: U.S. Fish and Wildlife Service, Ohio State University, The Nature Conservancy, Ontario Ministry of Natural Resources and Forestry, Minnesota DNR, Great Lakes Fishery Commission, Quebec Ministry of Forest, Wildlife, and Parks and New York DEC.
After the agencies have studied their data, results of the research project will be released. A total of 30 grass carp were were caught during the project (27 from the Sandusky and 3 from the Maumee).
Eric Weimer, DOW fisheries supervisor, lauded the the cooperation among the various agencies He noted as research continues, the long-term goal is to see how they can control grass carp in Lake Erie and its tributaries. “You can never get complete eradication, but we want to work on control,” he said.
Currently, there is no evidence of negative ecological or economic impacts to the Lake Erie ecosystem attributed to grass carp.
Hartman noted an interesting aside during the research project the last two years. It was discovered the Sandusky has a pretty good flathead catfish fishery. They have flatheads up to 30 pounds and larger.
Al Smith is a freelance outdoor writer. You may contact him at firstname.lastname@example.org and follow him on Twitter @alsmithFL