Slow year is good year on invasive carp front

Winona, Minn. — While the Minnesota DNR’s invasive carp-monitoring effort hasn’t found anything of note this spring, a pair of bighead carp have turned up on the Wisconsin side of the Mississippi River.

A Wisconsin man arrowed a bighead carp during a bowfishing tournament on Pool 5A of the Mississippi River near Fountain City, Wis., on June 12. And Nick Frohnauer, the Minnesota DNR’s invasive fish coordinator, said another bighead carp was found near La Crosse, Wis., in April, hooked on the crankbait of a youth angler.

But it’s still been quieter on the invasive carp front than last June, when six bighead carp were caught near the King Power Plant near Stillwater.

John Waters, DNR invasive carp fisheries specialist, monitors for the unwelcome invasives on the St. Croix and Mississippi rivers, employing different methods to look for adult, juvenile, and larval fish.

“We’re pretty much covering the whole base,” Waters said.

The U.S. Fish and Wildlife Service also does some monitoring for larval Asian carp on Minnesota’s southern-most stretch of the Mississippi River.

Only adult fish have been found in Minnesota waters, as the presence of juveniles and larvae would indicate the presence of a breeding population. The closest the fish have been verified to be breeding is Pool 19 of the Mississippi River, which is the southernmost pool, on the Iowa border.

“I am optimistic that they won’t (spawn here),” Frohnauer said, “but I can’t say with any certainty. … The hope is that the work we are doing will prevent them from ever making it this far.”

The work he referenced includes the monitoring effort, but also the research being done by the University of Minnesota’s Aquatic Invasive Species Research Center.

Waters returned to the King plant twice this spring to look for more bigheads, since so many were found there last year, but didn’t turn up anything in the low water conditions. Last year, water was running high there, and bighead carp are known to advance with high-water events.

In February, a bighead carp was caught by a commercial fisherman on the Minnesota River, the first time one of the invasive fish was documented in that river. At the time, the DNR wasn’t able to do much searching for more fish because of ice floes, but it did get out eventually, said Tony Sindt, the Minnesota DNR’s Minnesota River specialist based out of Hutchinson.

Sindt said there hasn’t been any monitoring for more Asian carp since, nor has there been much effort from commercial anglers on the river.

“We have gone about business as usual,” Sindt said, noting that most of the invasive carp-monitoring effort has been focused on the Mississippi River “because they would show up there first.”

Sindt said he will be doing some sampling on backwaters of the Minnesota River later this year, looking for young bighead carp, but doesn’t expect to find anything.

“I am very interested when the commercial fishermen do get back out, and I will likely visit their seine haul and monitor what they are catching,” he said.

Ann Runstrom, a fish biologist with the U.S. Fish and Wildlife Service based in La Crosse, Wis., said federal crews went out last week in the area where the bowfisherman caught the one bighead earlier this month, setting up 1,200 yards of gill nets and doing some electrofishing.

“We caught 15 paddlefish, six lake sturgeon, one bigmouth buffalo, and one freshwater drum, but no bighead carp,” said Runstrom, noting that the search included nearby areas known for being good paddlefish waters.

“We tend to find those species together,” she said, noting that both are filter feeders. “They like the same habitat. They eat the same food.”

In general, invasive Asian carp, which includes both bighead and silver carp, do appear to be slowly becoming more prevalent farther north in the Mississippi River.

In July 2014, two silver carp and a bighead were caught in Pool 2 of the Mississippi River, the farthest north they had ever been found, Waters said.

Frohnauer is hopeful the fish can be kept at bay using a variety of techniques including acoustic and flow-level barriers employed at one of the lock and dams, and perhaps through thinning their numbers by using commercial seine hauls to keep “that population low enough so that the pressure to expand upstream is lessened,” he said.

He mentioned that a set of three meetings with various agencies is slated for this year, where a prevention strategy will be the focus, and the Minnesota DNR is close to issuing a request for proposals for a feasibility study for using acoustic technology at Lock and Dam No. 5.

Peter Sorensen, at the AISRC, said many of his lab’s research projects are coming along and are at or near the point that they could be employed. In a lab, using sound as a barrier, Sorensen said three-quarters of fish have been repelled.

Sorensen’s lab also is studying, among other things, the swimming abilities of invasive carp and how that relates to flows out of the gates at the locks and dams.

“We have found that they are only average swimmers,” he said. “We think locks and dams are almost certainly good deterrents, but the way they are being managed is to reduce flows and erosion. If anything, that’s helping carp move upstream. By just adjusting the gates by a few inches we can have enormous ramifications.”

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