$1 million carp barrier having impact in Iowa Great Lakes, officials say

August 23, 2014
Sioux City Journal

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Three years after two Asian carp were netted in East Lake Okoboji, officials believe they stopped the voracious aquatic invaders.

The invasive species swam into the lakes during flooding in 2011. One species, silver carp, poses a safety hazard due to its propensity for leaping from the water when startled.

Officials believe a $1 million electronic fish barrier should be enough to keep more Asian carp from entering the lake system and threatening the $300 million tourism industry. Officials believe the fish can’t reproduce in still lake waters, so keeping more carp from swimming in will protect the lakes from being overrun.

It can happen. A South Dakota lake was so overrun by Asian carp and other undesirable fish that officials will kill off all of the fish and restock. Such drastic action shouldn’t be necessary in the Iowa Great Lakes, officials say.

“We think we closed the barn door before we got too many of them,” said Phil Petersen, of the Iowa Great Lakes Alliance, a protective organization.


The netting of the two bighead carp in 2011 was the first time any of the three invasive kinds of Asian carp had been found in the Iowa Great Lakes. The fish were imported to America to clean tanks in fish farms in the 1970s but escaped during flooding.

Their presence in East Lake Okoboji was not a welcome discovery at local bait shops.

“Oh, well, that would be perfect,” Tammy Wittkamp, of Stan’s Bait Shop in Milford, Iowa, recalled thinking sarcastically at hearing the news. “We really need them in our life. One more thing.”

All three species of Asian carp — bighead, silver and grass — have inhabited the Missouri River for years. Historically, they were kept from the Iowa Great Lakes by dams on the Little Sioux River in Harrison County, Iowa, and near Linn Grove, Iowa.

They swam over the dams during the flood in 2011. The fish entered the Iowa Great Lakes through the Lower Gar outlet.

The netting in 2011 was only the first sign of the fish. In 2012, commercial fisherman netted 82 bigheads and 55 silver carp in East Lake Okoboji.

Officials had feared the fish could become so numerous they could damage the lake. Or the jumping silver carp could become a hazard to boaters. Both would threaten the bustling tourism industry at the Lakes and Dickinson County each summer.

A $956,000 electric fish barrier was built in the outlet in 2012. The 21-foot-long concrete apron spans the width of the outlet with eight electrodes that emit a pulse of energy to kill any fish that tries to swim through.

Officials think it is working. So far, few people have reported seeing or snagging Asian carp in the Iowa Great Lakes. There have been no credible reports of silver carp jumping.

“I’ve never seen one,” said Lakes Area fishing guide John Grovner. “I’ve never heard of anybody seeing one and I’m out here eight hours a day every day.”


The battle against Asian carp in the Iowa Great Lakes so far seems to be one of the few times when officials get the jump on an invasive species, said Iowa Department of Natural Resources fisheries biologist Mike Hawkins.

“We got the upper hand quickly,” Hawkins said. “A lot of times there are losing battles.”

In three weeks, wildlife officials will kill every fish in Lake Yankton near Yankton, S.D. The lake near the tailwaters of Gavins Point Dam was overrun by Asian carp and other undesirable fish during the 2011 flooding.

Historic discharges from the dam pushed the Missouri River so high it flooded the nearby lake. Fish from the river, including all three species of Asian carp, were left behind when the floodwaters receded.

Officials were left with no other option than to use a chemical to kill all the fish and start over, said Jeff Schuckman, of Nebraska Game and Parks.

“The water got dirty, the vegetation disappeared and our sportfish really suffered,” he said.

The kill is set for Sept. 10. Restocking will begin this fall.

In spite of the seeming success in the Iowa Great Lakes, officials will be watching closely for similar signs of trouble, just in case.

“It’s always shades of gray. It’s never black and white,” Hawkins said. “We want to really monitor the situation.”