BENTON HARBOR, Mich. — The U.S. Fish and Wildlife Service conducted an electrofishing operation on the St. Joseph River Tuesday, surveying for grass carp and other invasive species.
Introduced to the Great Lakes Basin in the 1970s as a solution to plant growth in waterways, grass carp can consume their weight in food (up to 90 pounds) daily, and destroy the weed beds used by native fish for reproduction.
"We've always been told that if you take a picture with a grass carp, you don’t smile." USFWS Aquatic Invasive Species Team Program Leader Cari-Ann Hayer said.
For the past three years, the Green Bay-based crew has monitored native, nonnative and invasive populations in the St. Joseph River, among other Lake Michigan tributaries in the state, as well as in Indiana and Wisconsin.
During this year's survey period, Hayer and company netted nine grass carp from the West Michigan waterway— "ground zero," according to the longtime fisheries worker— and caught "about" 14 total in the Midwest region.
On Tuesday, though, the team's first three, ten-minute "runs" along the banks of the river resulted in a single grass carp sighting, but zero in the net.
"These fish are really hard to find," Hayer said. "They're hard to capture, even though they're really big."
The process of electrofishing involves stunning nearby fish with a high voltage current— calibrated with the salinity and turbidity of the waterway— through the placement of multiple anodes directly below the surface.
When within a few feet of the electrofishing boat, fish may involuntarily swim toward the current, their muscles stiffening to the point where some flip on their side and— for a few seconds— float to the surface.
"It's kind of fun," Hayer said. "You’re sitting there, then as soon as you get complacent, one pops up and all heck breaks loose, right?"
Then, native fish are identified and processed before being released.
"It's a very effective way to get our hands on a bunch of fish in a very short amount of time," USFWS Fisheries Biologist Sharon Rayford explained.
In the less common case of a grass carp, however, the crew removes the fish from the water in a way that is "quick and humane," cutting off its head while also taking blood and muscles samples for testing.
"If you like your bass fishing, if you like your lake trout fishing, or lake sturgeon fishing, you should be concerned about invasive species," Rayford said. "If they come in and take over spawning grounds, it's going to start having an impact on our recreation and commercial fisheries."
READ MORE: DNR: Silver carp 'highly likely' not swimming in St. Joseph River
The Aquatic Invasive Species unit will return to the St. Joseph River in the spring for continued testing, protecting the beauty and biodiversity of the waterway.
"That first ride on the river in the morning when the fog is starting to steam off as the day warms," Rayford said. "It's like you're flying."
“There's fish under there and you don't know what the heck they're doing," Hayer added. "Where are they? What are they doing? I want to catch them."
