Here’s how to stop spreading invasive species this July 4

It’s summer and it’s hot — the perfect weather to jet around an Iowa waterway on a boat. You bask in the sun and feel the thrum of the engine as wind knots your hair.

But you’re not the only one who detects murmurs from the boat engine rippling through the water. Stumble across the right patch of river and the vibrations may trigger an explosion of leaping fish. One may even land in your boat or send a splash your way.

Silver carp are notorious for their jumping habits — and their rapid, harmful and invasive spread throughout U.S. waterways. They’re one of several invasive aquatic species in Iowa, along with some plant and mussel species.

Squads across Iowa are combating the spread of invasive aquatic species — but they need residents’ help, said Kim Bogenschutz, the state’s aquatic invasive species program coordinator. Boaters can accidentally facilitate the invasion by not correctly cleaning their watercraft between rides.

Here’s the invasive aquatic species you need to know about in Iowa and how you can help mitigate their spread this holiday weekend.

  Buy Photo

Invasive aquatic plants

The Iowa Department of Natural Resource’s Aquatic Invasive Species program began with a single plant: Eurasian watermilfoil.

Eurasian watermilfoil was first introduced to the state in 1993 in North Central Iowa’s Crystal Lake, and has fanned from there. It grows early in the spring before other plants do, displacing native plants and the insects and invertebrates that rely on them. It grows into dense clumps of long stems covered in feather-like leaves and reproduces by fragmentation, not by seed.

Its spread led to a law prohibiting transport or introduction of the plant, which eventually evolved into today’s aquatic invasive species law.

Brittle naiad is another invasive aquatic species plaguing Iowa waters. It’s a bushy, dense plant with curved leaves that resemble a coral reef, Bogenschutz said. It was first found in 2003 and has since surpassed Eurasian watermilfoil in coverage. Unlike the watermilfoil, brittle naiad reproduces with seeds that latch onto anything — making it much harder to control.

Another invasive aquatic plant has been here since the 1940s: curly-leaf pondweed. Its life cycle differs from native pondweeds because it reproduces with little vegetative buds that sprout in the fall, live under ice during winter and survive to the spring. The species plagues every county in the state.

The Iowa DNR primarily uses herbicides to combat its invasive aquatic plants. Teams pour low quantities of the treatments into an affected water body — or, in the case of curly-leaf pondweed, they’re injected under the ice. The herbicides may impact other plants, but they only kill the specific species they target.

Some efforts are more successful than others. Eurasian watermilfoil, for instance, has been successfully eradicated from most locations in the state. But because the other invasive plants have seeds that get lodged into sediment, it’s more difficult.

“We can be very specific with killing certain species of plants because those herbicides have been developed specifically for those plants,” Bogenschutz said. “Most of them have no restrictions on swimming or fishing or even drinking water.”

Invasive invertebrates, fish

Zebra mussels are small, sharp mollusks the size of a fingernail. Their shells are adorned with zigzag stripes. They filter water for plankton and algae, which native mussels and fish species need to survive.

Baby zebra mussels, called villagers, can float in water for up to two weeks. That’s how they came to Iowa and the Mississippi River, after European ships unintentionally brought them to the Great Lakes in the 1980s and they spread through the Illinois River. Zebra mussels can also attach to hard surfaces, like boats or vegetation.

So far, Iowa doesn’t have many lakes with zebra mussels. But the invasive creatures do inhabit some popular spots, like Storm Lake and the Okoboji Lakes. They also clog up intake pipes for water treatment plants and hatcheries.

Unlike the control it has over invasive plants, the Iowa DNR does not have control over the rapid spread of zebra mussels in the state. There currently are no treatments that would kill the invasive mussels without killing native mussels as well. Researchers are looking into a bacteria that may affect only zebra mussels, but it’s still being tested.

“I think in the future, we will have some ways to control them a little bit,” Bogenschutz said. “We might not eradicate them, but just be able to help control their impacts.”

Species of invasive carp — as of now, the bighead carp and silver carp — have also invaded Iowa waters. The fish can reach more than 100 pounds and are filter feeders, competing with paddlefish and native mussels.

Iowa DNR seasonal worker Trevon Zeman stands at the bow of a boat as he looks for silver carp while electro-fishing along the bank of the Cedar River during a weekly project to track and manage the invasive species at Palisade-Kepler State Park in Mount Vernon, Iowa, on Friday, June 16, 2023. The fish, which can reach a maximum size of about 40 inches and 60 pounds, compete for plankton with native fish species. (Jim Slosiarek/The Gazette)

  Buy Photo

Electrodes dangle in the water around cover, silver carp's habitat, during the Iowa DNR's weekly project to track and manage the invasive species at Palisade-Kepler State Park in Mount Vernon, Iowa, on Friday, June 16, 2023. The fish, which can reach a maximum size of about 40 inches and 60 pounds, compete for plankton with native fish species. (Jim Slosiarek/The Gazette)

  Buy Photo

Iowa DNR fisheries biologist Chris Mack holds a female silver carp during a weekly project to track and manage the invasive species at Palisade-Kepler State Park in Mount Vernon, Iowa, on Friday, June 16, 2023. The fish, which can reach a maximum size of about 40 inches and 60 pounds, compete for plankton with native fish species. (Jim Slosiarek/The Gazette)

  Buy Photo

prev

next

Carp don’t need much help from humans to increase their range. They swam up the Mississippi and Missouri Rivers and several interior waterways by themselves, circumventing dams during floods.

Similar to zebra mussels, the Iowa DNR is struggling to manage invasive carp populations. But there are advances being made: For example, researchers are trying to target invasive carp using a sound barriers. By playing different sounds while tracking fish movement, they can see what deters invasive carp while not bothering native fish.

“It's just preventing them from moving into areas,” Bogenschutz said. “We’re just trying to figure out what we can do to control them because right now, there's nothing that will kill them that wouldn't kill other fish.”

Best mitigation practices

To help stem the spread of invasive aquatic species in Iowa, Bogenschutz has three words of advice: clean, drain and dry.

Before leaving a boat ramp, clean everything off your watercraft, including plants, mud and mussels. If it’s staying in the same water body, let your boat sit out and dry for a few days to kill anything on it. If you’re going to another water body, power-wash the watercraft to make sure everything is off.

Drain water from your boat and any bait containers, live wells and ballast tanks you may have. Don’t dump your bait in the lake; take it home and put it in the trash if you don’t want it anymore.

“It’s not just a recommendation anymore,” Bogenschutz said. “It’s the law.”

The state’s aquatic invasive species law prohibits the transport of any aquatic invasive species or plants. The fine for violating the law is $500. Failing to remove your drain plug to drain water results in a $75 fine.

“It just takes a couple minutes to walk around your boat, make sure everything is cleaned off,” Bogenschutz said.

  Buy Photo

Brittney J. Miller is the Energy & Environment Reporter for The Gazette and a corps member with Report for America, a national service program that places journalists in local newsrooms to report on under-covered issues.

Comments: (319) 398-8370; brittney.miller@thegazette.com