The Great Lakes Fishery Commission’s 66th annual meeting began Tuesday with an update on the latest efforts to control one of the oldest and most menacing of all invasive species: vampire-like sea lamprey.
There also was a talk about how each of the lakes, especially Lake Erie, are almost becoming a tale of two lakes. Their near-shore areas are getting too many nutrients from farm runoff and other sources, while the open waters of each lake are becoming more starved of the nutrients they need. It’s a perplexing situation to fish scientists, and was the subject of a recent report.
But perhaps the most localized information for northwest Ohio came from a panel about grass carp, which featured targeted efforts by a University of Toledo professor and others to thin out numbers of that invasive fish in the Maumee and Sandusky rivers, especially the latter.
Christine Mayer, a UT ecology professor who’s helped physically remove grass carp from the Sandusky River since 2017, including 98 in 2020, compared the ongoing effort to running a New York apartment building.
“When one moves out, another moves in,” she said. “There's definitely a pool of fish out in the lake ready to move into the Sandusky. There is definitely a pool of fish out in the lake ready to move in when an apartment opens up.”
Grass carp are one of four so-called carp species known as Asian carp.
They are worrisome because they feed on large swaths of vegetation and are one of dozens of invasive species upsetting the balance of nature in the Great Lakes. But they typically don’t garner as much attention as the two species scientists are fighting hardest to keep out, the bighead and silver carp.
Both have been swimming up the Mississippi River system and threatening to enter Lake Michigan in Chicago.
The bighead is the largest of those species. Silver carp are internet sensations. There are many online videos of them being akin to fleshy projectiles because of their high sensitivity to motor vibrations, causing them to leap into the air and occasionally strike at passing boaters.
Grass carp eggs have been found in the Maumee River near downtown Toledo.
But that type of carp spawns especially heavily in the Sandusky River near Fremont, Ms. Mayer said.
Part of the research Ms. Mayer and others are doing pertains to their habitat and spawning. They want to know more about their life cycles to help get rid of them.
Between 2018 and 2020, the grass carp population in the Sandusky was believed to have ranged between 164 to 183 a year, according to numbers Ms. Mayer presented.
Even the 98 grass carp removed in 2020 hasn’t appeared to make an appreciable dent in the river’s population.
“We're estimating 160 to 180 fish in the river and it hasn't changed much,” she said. “We've removed fish, but we haven't seen a drop in numbers.”
She and other scientists are trying to find out why.
About 75 percent of the grass carp removed from the Sandusky those years were capable of reproducing.
This year, the Great Lakes Fishery Commission’s Lake Erie Committee is seeking funds to increase the number of carp-catching teams from three to 10. It also has set a goal of removing 390 reproductive-capable grass carp from the Great Lakes a year, said John Dettmers, the GLFC’s fisheries management director.
Mr. Dettmers and Ms. Mayer were joined on the afternoon grass carp panel by John Navarro, Ohio Department of Natural Resources aquatic invasive species program administrator, who talked about plans for a high-tech barrier he and other officials hope will be built to keep grass carp away from their spawning habitat.
Another dam?
Not at all. The Ohio DNR and others just had the aging Ballville Dam south of Fremont removed to improve spawning for other fish.
“Right out of the gate, we want to make clear we’re not doing that. We don’t want a hardened structure,” Mr. Navarro said.
Instead, they envision a seasonal structure to disrupt the grass carp spawning season from May through August with acoustic sounds, light, and air bubbles, he said.
Now that a feasibility study is done, agencies are seeking grant money from the Army Corps of Engineers to proceed. Then, the project would enter its final design phase, Mr. Navarro said.
“We really think between removal and this barrier, we can really knock this species back,” he said.
Much is dependent upon the federal Great Lakes Restoration Initiative, which has been reauthorized by Congress and approved for higher funding.
“If we did not have that, we would not be where we are today, which is hopefully eradicating one of the Asian carp in the Great Lakes,” Mr. Navarro said.
The effort includes multiple state and federal agencies, and university researchers across the Great Lakes basin.
“Grass carp is definitely a team sport,” Ms. Mayer said. “Nobody's doing this alone.”
The second and final day of this year’s Great Lakes Fishery Commission meeting is Wednesday. The event is being held online because of the coronavirus pandemic.
First Published May 25, 2021, 10:32 p.m.