S.D. officials expand plan for slowing spread of zebra mussels upstream in Missouri River

Capitol News Bureau

OACOMA, S.D. (KELO) — The South Dakota Game, Fish and Parks Department needs help from state lawmakers in battling zebra mussels that have invaded several Missouri River reservoirs.

Several GFP staff outlined plans Wednesday at a public meeting. A similar session is planned at 7 p.m. Thursday at the Pierre Ramkota.

The bottom line is they want broader authority to check boats to be sure drain plugs are removed when out of the water and there aren’t zebra mussels anywhere on the vessels.

They also want more seasonal staff to do inspections during the main boating months of May through August.

Zebra mussels aren’t a native species to the U.S. but they’ve gradually spread west during the past 30 years.

The first zebra mussel was confirmed in South Dakota in 2014. It was found in Lake Lewis and Clark, the farthest downstream of the major reservoirs on the Missouri River.

Within two years, divers found zebra mussels had encrusted parts of every boat kept in the water at Lewis and Clark marina.

The discovery of zebra mussels in another Missouri River reservoir, Lake Sharpe, in July was “a game changer,” according to Mike Greiner. He’s GFP’s aquatic invasive species coordinator.

Governor Kristi Noem appeared in a video on zebra mussels that state agencies released through the internet ahead of Labor Day weekend.

While they spread by boat, zebra mussels most threaten water systems because they clog pipes, whether inside hydro-power dams that generate electricity or the intakes that draw water for drinking and irrigation.

About 200,000 people in South Dakota get drinking water from Missouri River systems. More than 80,000 acres of crops are irrigated in the state from the river.

Zebra mussels have razor-sharp shells and are three to five centimeters in size as adults, with threads that attach like cement to hard surfaces, according to Greiner.

“They’re very successful invaders,” Greiner said. “Each female can produce up to one million eggs a year.”

Posting inspection teams next summer to check boats at all 101 ramps on the Missouri River in South Dakota would cost an estimated $6 million just in wages and require 404 seasonal hires, he said.

That’s probably not possible, according to Greiner. What might be, if lawmakers agree, is manning 35 stations with 140 seasonal employees at a cost of about $2.5 million in wages.

Lake Lewis and Clark is the reservoir behind Gavins Point dam. Jonas Grundman works there as a natural resources specialist for the U.S. Army Corps of Engineers.

Grundman said two high-intensity UV light systems were installed at the dam and have worked well this season in killing what are called veligers, the larval stage of zebra mussels.

Greiner said veligers are impossible to see with the human eye and are the width of a hair.

He said zebra mussels haven’t been found yet in Francis Case or Oahe, the two other Missouri River reservoirs in South Dakota.

The department became much more aggressive after the July discovery in Sharpe.

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