Carp Roundup important to conservation

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STORY AND PHOTOS BY ERIC FOWLER
outdoornebraska.gov

Cattle drives are an important part of one chapter of Nebraska’s history. For about 20 years in the late-1800s, cowboys on horseback would push huge herds of longhorns from Texas to Nebraska, where the animals were loaded on trains and shipped to feed a growing nation.
Cattle drives and roundups remain a part of everyday life on ranches throughout the state today. It’s a pretty simple process, where cowboys on horseback, ATVs or pickups push the cows from one place to another. But sometimes a stubborn old cow, or a few of them, just won’t do what you want them to.
Fish drives, on the other hand, are new to the state. In December 2019, what may be the first fish drive conducted in Nebraska was held at Hanson Lake No. 3 near Plattsmouth. The drive used sound and electricity to push invasive, non-native Asian carp into a bay where they could be seined. And while this roundup was fairly successful in doing so, capturing 25,000 pounds of mostly silver carp, just like in a cattle drive, some of the fish didn’t do what they were supposed to do.
Asian carp have found their way into every tributary of the Missouri River in Nebraska, including the Platte, Elkhorn, Loup or Nemaha rivers, swimming upstream until a dam keeps them from going farther. Just as they found their way into Hanson Lake, they have found their way into other lakes as well, especially during historic flooding in 2019.
“Anything that got flooded at that time has the potential of having these Asian carp in it, whether it’s a sandpit or a pond or a quarry pit that was close to the river,” said Jeff Blaser, private waters specialist with the Nebraska Game and Parks Commission.
Blaser has taken calls from quite a few lake associations on the subject. He first worked with the folks at Hanson Lake in 2011 when white perch and silver carp appeared after flooding. Then again in 2018.
For those that live in the houses that line the shore of this 44-acre sandpit lake, the arrival of the fish, especially the silver carp, was not welcome. Silver carp are easily startled and are known to respond to disturbances ranging from thrown rocks to passing motorboats by jumping up to 10 feet out of the water.
“They’ve just been a real nuisance jumping into boats and hitting people,” said Kevin Eastman, a member of the homeowners association. “People are scared to go tubing and skiing and stuff because they might jump up and hit somebody and hurt them real bad.” Several people have been hit by “flying fish,” but none seriously injured.
With the possible liability involved, the association hired Jeff Reidemann, a commercial fisherman from Minnesota, to seine the lake in 2018. While that operation did remove about 8,000 pounds of Asian carp, estimated to be 20 percent of the total present, obstructions on the lake bottom, including an old truck, snagged the nets and limited the success.
The bright side to these invasions is that unlike common carp, Asian carp do not, except in rare circumstances, reproduce in still water. Their eggs and larvae must drift for some time to be viable. When Blaser aged the fish that were harvested, he found year classes that didn’t match flooding events. Blaser suggested they check any inlet and outlet structures. When they did, they found an outlet used to control lake levels dumped into a ditch that led straight to the Platte River and was not fitted with screens to keep fish out. When water levels were high, “Those older fish and the young of the year fish were finding that and following it up into the sandpit,” Blaser said.
The outlet has since been modified with a pump station and backflow preventer to keep fish out.
In 2019, the association brought the seining company back, along with Tony Havranek of WSB Engineering, a Minnesota company. Havranek brought with him a plan adopted from similar work being conducted to drive and round up Asian Carp in the United States.
DUANE CHAPMAN of the U.S. Geological Survey in Columbia, Missouri, has been working on the biology and control of Asian carp since 2002. Through that work, he has developed relationships with fisheries biologists in China, where these carp species are raised commercially. While working on a book with one of those biologists, one of harvest techniques used by the Chinese, the Unified Method, jumped out at him. He traveled to China in 2015 with another biologist and a commercial fisherman to learn more about it.
There, floodplain lakes along the Yangtze River covering thousands of acres are used as aquaculture facilities. Each year, during the course of a few months, fishermen start at one end of the lake and drive fish to the other. “They get out there in these wooden boats and tiny, funky outboard motors and make a lot of noise and try and chase them out,” Chapman said. As they move fish from an area, they set a series of block nets, suspended from a “forest of bamboo” poles driven into the lakebed to keep fish from returning. When a cell is cleared of fish, they play “leapfrog” with the nets, moving them down the lake. At the other end of the lake, they net fish each day and deliver them to the market live, satisfying the demand but not overwhelming it. Fishermen are disappointed if by year’s end they don’t capture at least 85 percent of the fish in a lake.
Back in the states, Chapman and others tweaked the method to speed up the process. “We don’t really want to spend 31⁄2 months catching a little bit of the fish every day,” he said. Rather than simply rely on the sound of boat motors, they added sound from underwater speakers and electrofishing boats.
Electrofishing, a method used to sample game fish by stunning them with a light charge of electricity and netting them when they float to the surface, doesn’t work well with silver and bighead carp. Those species sense the charge and swim from it. Knowing that, biologists have modified the electrodes to create a wide field and reduce the charge when driving fish. “We don’t want to stun anything, not even the native fish or the carp, we just want to tickle them,” Chapman said.
The first test of the method came in 2016 on a 5-mile long, 500-acre sandpit lake southwest of Chicago along Illinois River, where biologists are fighting to keep silver and bighead carp from finding their way into Lake Michigan. Before the test, acoustic transmitters were implanted in carp and receivers placed throughout the lake to measure the effectiveness. When the speakers were turned on, fish moved the entire length of the lake in a matter of hours. “The distance that we’re able to push these fish and the rapidity with which were able to do it is frankly amazing,” Chapman said.
“The great advantage we have with this method when it comes to bycatch is most of our native fish don’t run away from the sound like the carp do.”
Using sound, electricity and block nets to drive the fish to a capture area, state and federal biologists and commercial fishermen removed 100,000 pounds of silver and bighead carp.
Similar efforts have since been conducted on other lakes in Illinois, a section of the Illinois River, bays of Kentucky Lake, and several lakes in Missouri. At Creve Coeur Lake, a 2,100-acre lake in suburban St. Louis, biologists and commercial fishermen spent three weeks in 2018 driving fish and setting nets and, in the end, removed about 47,000 silver and bighead carp, weighing 225,000 pounds. Many more fish were released from the trap nets when ice storms and scheduling conflicts ended the project.
Not only had the Asian carp become a nuisance to kayakers and other users of Creve Couer, they also had decimated what was a  premier crappie fishery. Chapman suspected several years ago that crappies would be the game fish most affected by Asian carp, and that is coming to fruition.
“In all of these floodplain lakes, when they get Asian carp in them, the crappie catch goes through the floor eventually,” he said. The reason, he believes, is reduced recruitment because 2- to 4-inch crappie compete directly with large carp for that zooplankton resource. The year carp were removed, crappie recruitment was the best it had been since their arrival, and officials are now working on a barrier to keep the invasive fish out for good after the next roundup.
The effects Asian carp can have on a fishery were evident at Lake Yankton, located below Gavins Point Dam. When silver and bighead carp and other rough fish invaded the border water during flooding on the Missouri River in 2011, the game fish populations collapsed. By the time the lake was renovated in 2014, rough fish, primarily silver carp, made up 90 percent of the biomass. Bass, panfish, catfish and walleye, as well as aquatic vegetation, have since thrived.
CONSIDERABLY smaller in size, the work at Hansen Lake No. 3 wouldn’t require the manpower or equipment needed at other operations. The first afternoon on the lake, Havranek, Riedmann and their crews used boats with side-scan sonar to survey the lake. A shallow bay on the east end of the lake where they planned to net the fish was devoid of them. A narrow channel connects this bay to the main lake where sonar found several large schools of Asian carp. Using boats equipped with underwater speakers, they drove fish out of the western portion of the lake and left speakers running overnight on the west shore.
The next day, they again used sound to again push fish east before setting a block net across the middle of the lake. Gill nets were set on the ends of the net and behind a small hole beneath it in an area that was deeper than the net. They continued to use sound and an electrofishing boat to drive fish east before leaving speakers running on the block net overnight.
On the third and final morning, after scans found numerous fish in the east bay, a block net was set to close it off from the main lake. A 1,250-foot seine was wrapped around the bay, and crews pulled in 26,000 pounds of fish, 80 percent of which were silver carp, 14 percent bighead carp, and the remainder bigmouth and smallmouth buffalo, common carp, grass carp and gar. Follow-up scans found that some fish had found their way under the block net and into the west portion of the lake and others remained in the eastern portion of the main lake, but they estimated that about one third of the rough fish biomass was removed.
Happy with the results in what was a learning experience for each of the parties involved, they are hoping to try again this winter. “This time, I’m going to bring enough net to make three different blocks and really try to crowd those fish into that eastern part of the lake,” Havranak said.
Eastman said there were noticeably fewer jumping fish at the lake this past summer. “If they can get 80 percent of what’s left or so, I think that would be a win.” Residents are already hopeful they can improve the fishery, and last year more than tripled their typical budget for fish stocking.
THE WORK at Hanson Lake was Havranek’s first attempt at driving silver and bighead carp with sound. Most of his fisheries management work involves common carp. Last winter, he worked with the Minnesota Department of Natural Resources and commercial fishermen on a suburban lake in Minneapolis on a project to remove common carp. With radio tags in fish, they knew where a large number of fish wintered. Because the shallow bay was strewn with boulders, it could not be seined. They used underwater speakers to drive fish from the area, monitoring the movement of tagged fish. Weeks later, they used a block net to cut off their escape route and directed fish into a seine, capturing 12,000 pounds. Havranek used speakers to move carp at other times during the year, and while there would be substantial logistics and planning involved, he sees potential for use elsewhere to manage carp populations.
As for using sound to drive and harvest Asian carp in floodplain lakes, “This is a no-brainer that this is going to be an incredible tool,” Chapman said.
It would be impossible to use it in the Missouri or other large rivers due to the current and debris present, Chapman said. But if suitable netting areas could be cleared of debris, it may be possible to harvest fish in tributaries with sufficient depth and low velocities, like the mouth of the Big Nemaha River. “You could drive these fish up and down there like cattle,” he said.
Like cattle, there will always be fish that don’t want to cooperate. Unlike cattle, which are easy to see breaking from the herd, it’s harder to see fish making a break underwater, even with today’s high-tech fish finders. But it’s certainly a promising control technique.
So, yee-haw! Get along little fishy!

Carp Roundup

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