FREMONT, Ohio — Researchers at the University of Toledo are making significant strides in tracking invasive species of fish in area rivers and the Great Lakes. The invasive grass carp fish has been repopulating the Sandusky River for years and could ruin Lake Erie's wetland ecosystems.
Bob Mapes leads the University of Toledo Grass Carp Field Crew and knows the Sandusky River like the back of his hand. His team's mission is to locate and catch the highly invasive fish species.
“They’re pretty big suckers, they tend to be 2 to 3 feet long and average 30 to 40 pounds in weight,” said Bob Mapes.
Grass carp are from Eastern Asia and were introduced to the U.S. in the 1960s to clean ponds in homes or golf courses. They’re herbivores and can eat their entire body weight in plants a day, which is a huge problem for wetland sustainability on Lake Erie and in area watersheds. Mapes said 5% of the historic Lake Erie shore wetlands are already gone.
“A population that’s been slowly growing over decades that we just kind of recently got to the point of causing concern,” said Mapes.
But grass carp are difficult to catch.
“They’re rare,” said Mapes. “Pretty hard to find now which means this is the time we can actually make an impact.”
The tool making that process easier for researchers is electrofishing nets. When the nets get placed into the water, it creates a 10-to-15-foot cloud of electricity underneath and around the boat. It immobilizes the fish and makes it easier for researchers to scoop up invasive species.
“This is the least invasive way to capture the fish,” said Mapes.
The new method created by the University of Toledo researchers shows progress in fighting the spread of grass carp, but could now lead to new management strategies for other "sleeper species". According to UToledo's recent publication, the estimates from the new model show that from 2018 to 2020 there were less than 200 grass carp in the Sandusky River. During that time period, the field crew captured 96 carp in 64 out of 380 events. The research also finds that grass carp are dying faster.
"The field crews went out and did studies with enclosed areas with nets and were able to sample over and over again and determine the probability of the detection of our gear," said Dr. Christine Mayer, professor of Environmental Science at the University of Toledo. "New runs of this model that the number that we think are in the rivers are going down."
Grass carp start spawning in May when the water is warmer, so we didn’t catch any Tuesday but fishing is a practice of patience and, in this case especially, a thoughtful strategy.
“Before their population expands and gets too big to manage, if we hit them hard right now, we might be able to stop further spread and further degradation,” Mapes said.
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