Fishermen, boaters can help limit the spread of aquatic invasive species in local waters

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Denver Link, a seasonal employee with the Iowa DNR’s aquatic invasive species unit, led a program at Pikes Peak State Park near McGregor on Saturday. (Photos by Audrey Posten)

Locally, one of the most common aquatic invasive species is the zebra mussel. The tiny invaders spread quickly by attaching themselves to boat propellers, trailers and equipment, clinging to aquatic plants and remaining in water from undrained containers and boat hulls. They also attach themselves to native mussels, eventually out-competing other mussels for food and killing them.

By Audrey Posten, North Iowa Times

By following a simple slogan, “Clean, Drain and Dry,” fishermen and recreational boaters can help limit the spread of aquatic invasive species in local waters.

“An invasive species is a non-native plant or animal that infests an area,” explained Denver Link, a seasonal employee with the Iowa DNR’s aquatic invasive species unit, who led a program at Pikes Peak State Park on Saturday. “They have no natural predation, and they can have a traumatic effect on native species.”

He’s spent the summer visiting boat landings, where he inspects watercraft and educates people on some of the area’s invasive species threats and how they can help keep waters healthy and vibrant.

Locally, zebra mussels are one of the biggest problems, Link said. Brought to the region by Great Lakes barges, the tiny invaders have spread to rivers and some interior lakes. According to the DNR, they feed extensively on microscopic plankton, reducing the food for native small fish and organisms and disrupting the entire aquatic ecosystem.

“They’re filter feeders, just like our mussels,” Link said, “and they cling onto our native mussels and compete with them, and eventually out-compete and kill them.” 

“They cause a lot of harm for boaters and fishermen as well,” he added. “If you have pipes under water, they’ll go up into the pipes and clog the pipes.”

 Zebra mussels spread quickly by attaching themselves to boat propellers, trailers and equipment, clinging to aquatic plants and remaining in water from undrained containers and boat hulls.

So far, said Link, the Upper Mississippi has been spared from another well-known invasive species, the Asian carp. Like zebra mussels, they compete with native species by eating plankton and altering food webs. 

“A few commercial fishermen have caught some,” Link shared, “but we’re still unsure of their potential in this part of the river due to the colder water.”

 There’s a “line” drawn at the lock and dam at Keokuk, he noted. “They have electrical currents to keep them from swimming through the dam, but the problem is they can still lock through with the barges.”

Animals aren’t the only aquatic invasive threats; plants cause problems too. Curly-leaf pondweed and Eurasian watermilfoil are the most common.

Link said these plants grow in thick mats, smothering native plants and making it difficult for boaters to navigate waters. 

“People think, ‘Well, we have more vegetation. They’re giving oxygen,’” he said. “Maybe for a short period of their life cycle. But later in the summer, as temperatures increase, they actually die off and the bacteria that helps with decomposition takes all the dissolved oxygen in stagnant areas and causes fish kills.

Curly-leaf pondweed and Eurasian watermilfoil can spread by wrapping around boat propellers, trailer axels, bunks and rollers. Just one small piece can grow a new weed bed in another body of water. 

In some areas, Link said officials cut curly-leaf pondweed in order to manage it and leave areas open to recreation. Another option is to put chemicals in the water to eradicate the invasive plants, but that can impact other aspects of the ecosystem.

“That’s really complicated,” he explained, “and it’s actually really expensive.”

Purple loosestrife—a tall, spiky plants with purple flowers—is another common invasive plant. 

“It looks pretty and a lot of people like to plant it in their yardscape, but it’s very invasive, especially by wetlands,” said Link. “It takes out a lot of the native wetland plants, like cattails” and can reduce food, shelter and nesting areas for native animals.

The spread of these invasives can be slowed by following “Clean, Drain and Dry.” 

Clean your watercraft, trailer, motor and equipment, removing any visible aquatic plants, zebra mussels and mud before leaving any water access.

“In 2013, Iowa passed a set of laws that says you can’t transport aquatic vegetation of any kind. So if a boater pulls out from a landing and has vegetation hanging from his or her boat, on the trailer, on the motor, in the live well, it needs to be removed before transport,” Link stated. “If you have an invasive species, it can be a $500 fine.”

Drain water from the boat, bilge, motor and live well by removing the drain plug and opening all water draining devices away from the boat ramp. 

Dry everything at least five days before going to other waters and landings, or spray or rinse recreational equipment with high pressure and hot water.

“You can actually get fined, too, if you get caught with your drain plug during transport,” Link said. “These are just some little things we’re trying to do just to stop the water and vegetation from transferring.” 

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