by Sarah Einselen
They swim. They jump. They eat their body weight in plankton.
And they’re creeping up the Wabash River.
Two species of Asian carp have been found spawning in shallower areas of the Wabash River than researchers previously thought possible, according to a Purdue University study recently published. A series of deeper spots in the Wabash River on Logansport’s west side even provide a sort of safe haven for the invasive fish in summers, said Purdue researcher Reuben Goforth.
Bighead carp and silver carp reached the Logansport area of the Wabash river in the early to mid-2000s, Goforth said. They’ve become a problem for local fishing enthusiasts because they eat much of the same plankton that feeds native species, crowding them out of the food chain, and because they can jump as high as 10 feet out of the water if they’re disturbed.
“People actually do get injured as a result of jumping silver carp,” said Goforth. “If you’re in your motorboat and you’re tooling around at 25-30 miles per hour, then something that’s on average about the same mass as a bowling ball hits you in the face — it’s softer than a bowling ball, but there have been cases of concussion, broken bones, that sort of thing that have resulted from fish jumping out of the water and colliding with people.”
Bighead carp don’t jump, he said, but some hybrids of the two species do.
Asian carp arrived around Logansport in about the early to mid-2000s, Goforth said. The species were originally imported and confined to southern U.S. aquaculture facilities and fish farms. However, some escaped into the wild in the 1970s and have been swimming northward since then, according to the Asian Carp Regional Coordinating Committee’s website.
While conservation workers and scientists are working hard to contain Asian carp, there is still concern that they could spread to other tributaries if they get into the Great Lakes, according to a Purdue release about the study.
They’re voracious, eating algae and other microscopic organisms that native fish species live off of, according to the regional committee’s website. Juvenile Asian carp can eat anywhere from 20 percent to 120 percent of their body weight each day.
Previously, researchers thought Asian carp could spawn only in relatively deep or fast-moving water, and would stop doing so sometime in July.
The Purdue study found evidence of fish spawning as far upstream as Wabash, where the water level is half that of the river’s level around Lafayette, and found eggs drifting in the water as late as September.
Over the summer, they “hunker down” until the first autumn rainfall, when they swim back downstream for the winter.
“It turns out that the area around Logansport in the Wabash is a fairly important summer refuge for a portion of the population,” Goforth said. In summer, the holes where the Asian carp like to congregate are typically at least 6 feet deep — a favorable environment for fish that consider 3 feet “pretty shallow,” he added.
The study was conducted last spring, as water levels were dropping due to last year’s severe drought, he said. The drought limited stream flows, according to the Purdue release, but Asian carp eggs were still found in shallow and narrow portions of the Wabash once thought incapable of supporting the species.
“We didn’t have the normal spring floods and they spawned anyway,” Goforth said. “Those changes in water flow and depth might be a cue to spawn, but they’re not something that’s absolutely necessary.”
It’s difficult to say just how many Asian carp are calling Logansport home.
“They’re really hard to do population estimates on because they’re real skittish,” explained Goforth. “So when you get close to them they tend to swim away very quickly.”
He said silver carp are likely more abundant than bighead carp around Logansport.
Goforth is conducting further research into what allows Asian carp to adapt to conditions unlike those in their native habitats. He added that he’s also tracking the movements of silver carp in particular.
In the meantime, what should boaters and fishing enthusiasts do?
Since Asian carp can be found just about anywhere when the water level is high, Goforth recommends being watchful — or you might get hit while boating or wading down the river.
“You just have to be aware of what’s going on around you,” he said. “There’s not really any simple formula to when a carp’s going to come flying out of the water and smack you.”
Sarah Einselen is news editor for the Pharos-Tribune. She can be reached at firstname.lastname@example.org or 574-732-5151.