KANSAS CITY, Mo. -- Andy Jansen dipped a net into the swirling waters of the Kansas River and immediately came up with more than 100 reasons to be concerned.
With little effort, he scooped up a net full of young Asian carp, an invasive species in the midst of a population boom.
"I can't believe how many silver and bighead carp there are in here," said Jansen, a fisheries biologist for the Kansas Department of Wildlife and Parks, as he stood below a low-water dam along Interstate 435 in Johnson County.
"We knew they had made their way into the river. But they were never this abundant until this year.
"We think that the combination of all the rain and the water rises we've had, plus the warmer temperatures, have just made for ideal spawning conditions.
"And that's not good. We definitely don't want them in our waters."
The carp were brought to the United States in the 1970s by the aquaculture industry to improve water quality in ponds and to be raised as a food fish.
They did fine in their confined quarters, though they never did fill a niche as table fare. But once they escaped hatcheries during flooding and moved into major waterways such as the Mississippi and Missouri rivers, they started causing big problems.
As with many invasive species, they haven't exactly fit into their new surroundings. With a voracious appetite and a fast growth rate -- they can reach upwards of 50 pounds -- they have quickly multiplied and have become resource managers' newest crisis.
There were days when the silver carp's penchant for jumping at the sign of advancing boats was viewed as a novelty. Fishermen on the Missouri River would even carry trash-can lids that served as makeshift shields. Those lids were emblazoned with the letters "CDD" -- for Carp Deflection Device.
But that novelty has worn off. As the carp become more numerous -- as they have in the Kansas River -- the dangers they present to humans and the fisheries are capturing the attention of fisheries managers, boaters and fishermen.
They certainly caught kayaker Brad Pennington's attention last week on the Missouri River. As he competed in the Missouri 340 race, a silver carp flew out of the water and knocked him on the head. He reported becoming dizzy and had to drop out of the race.
"It felt like a brick hit me," he told The Associated Press.
Fisheries officials also worry about the rapidly expanding Asian carp population, which so far has been found only in major river systems such as the Missouri, Mississippi, Kansas and others.
"These Asian carp grow so fast that they don't have much value as a baitfish," Jansen said. "Our biggest fear is that they'll get in our reservoirs.
"If that happens, we could be in for some big trouble."
But those concerns aren't confined to Asian carp.
Zebra mussels, a diminutive bottom dweller, have made their way into popular fisheries such as Lake of the Ozarks, Lake Taneycomo, Milford Lake and Perry Lake and threaten to create turmoil because of their penchant for spreading quickly and competing with gamefish for valuable plankton.
And white perch, a popular species in the northeast United States, have caused big problems in Kansas after being accidentally stocked in waters such as Cheney Reservoir near Wichita. They became so abundant there several years ago that they contributed to the decline of walleye and white bass numbers.
Add the invasion of exotic types of vegetation that are beginning to show up, and resource managers have good reason to worry.
"Back in the good old days, we never saw things like this," said Jason Goeckler, aquatic nuisance species coordinator for the Kansas Department of Wildlife and Parks. "But as we've gone to a global economy, it's become more and more of a concern.
"We're seeing many species being transported from overseas by the shipping industry. I saw one study that showed that ballast water from transcontinental ships has 5,000 to 7,000 species in transit right now.
"And that's frightening."
This year has provided ideal conditions for Asian carp, and they have flourished.
Not only has the population boomed in the Kansas River, the waterways below Smithville, Mozingo, Longview and Blue Springs reservoirs, as well as Lake of the Ozarks, have seen big infestations of Asian carp.
Once the fish get into a waterway, little can be done to control them. That's why resource managers are so concerned that they one day might get into area reservoirs.
"They feed on plankton, and they would be competing with our baitfish and young-of-the-year gamefish," said Tim Banek, invasive species coordinator for the Missouri Department of Conservation. "With the way they multiply so quickly, they could become a real problem."
Banek and others stress that fishermen need to help in containing the spread of the invasive species. Because the Asian carp young look similar to shad, which are native baitfish, biologists are concerned that fishermen will mistakenly net them and transport them to reservoirs to use as bait.
Regulations in both states prohibit transporting live Asian carp to other bodies of water and violators are subject to fines. Still, there are worries.
"The best way to tell Asian carp and shad apart is that the carp have an upturned mouth and their eyes are set lower than their mouth," Goeckler said. "Shad typically have a black spot on them.
"And in a bait bucket, you'll see the difference. Shad are fragile and often die without much oxygen. Asian carp are much hardier and will survive in much tougher conditions."
When zebra mussels were discovered this summer on a boat lift at Smithville Lake, resource managers wasted little time in jumping in action.
The lift, which had been brought to the Kansas City area from Lake of the Ozarks, was immediately removed. The Missouri Department of Conservation applied an algaecide that contains copper, which is toxic to zebra mussels, to the water near where they were first discovered.
Now it's wait and see. Scott Ryan, a fisheries biologist for the Missouri Department of Conservation, is hopeful that he and others caught the problem in time.
Craig Johnson, a fisheries biologist for the Kansas Department of Wildlife and Parks, knows all about those problems.
He manages El Dorado Lake near Wichita, the first area reservoir to become infested with the tiny mussels.
"When we found them at the end of August in 2003, you would have to pick up eight rocks to find one zebra mussel," Johnson said. "By 2005, you could pick up one rock and find literally thousands them.
"That's how fast they spread."
As the zebra mussel numbers climbed to a peak in 2006, it appears there were effects on the fishery. Shad numbers declined and fishermen complained of seeing many skinny fish. Whether that was caused solely by zebra mussels, which feed voraciously on the plankton that baitfish and young-of-the-year gamefish depend on, no one knows.
But biologists suspect that the zebra mussels at least played a part.
Thankfully, the zebra mussel population has declined at El Dorado, in part because of their short life cycle and to several wet years that have resulted in a higher flow-through rate in the reservoir. But Johnson still isn't ready to say that the problems are over.
Since the zebra mussels were first discovered in the two-state area, they have expanded to other waterways. Kansas now has nine reservoirs and the rivers associated with them that contain the invasive species while Missouri has seven.
The best way to stop their spread? Fishermen and boaters should drain water from their live wells and bilges, they should clean their boats with hot water, then they should dry them thoroughly before taking them to another reservoir.
"Fishermen and boaters have to be aware of what's at risk," Goeckler said
So what's the answer?
That's a question resource managers have been struggling with.
But that doesn't mean there aren't ways to battle the invaders. Resource managers are studying ways to reduce numbers of Asian carp, including increasing their marketability to commercial fishermen.
Various treatment options are being studied for lakes infested with zebra mussels. And states such as Kansas have taken safeguards to ensure that they won't receive contaminated stocks again.
But it's a tough battle, officials admit.
"With our global economy, I think we're going to have to deal with more problems in the future," Banek said.
Invasive species have moved into Missouri and Kansas, and they are creating problems for humans and native fish. Here's a look:
ASIAN CARP
Silver and bighead already are a big problem in major waterways such as the Missouri and the Kansas rivers. The silvers, which typically weigh 20 to 40 pounds, jump at the sound of everything from outboard motors to trains and have caused injuries to boaters. Bighead carp can approach 100 pounds. Both species are a threat to established fisheries because they multiply quickly, are voracious eaters and compete with gamefish.
ZEBRA MUSSELS
These tiny mussels were introduced to the United States in the late 1980s when they hitched a ride on transcontinental ships. They first affected the Great Lakes, but have since spread inland to states including Missouri and Kansas. They are considered a danger because they can build large colonies in a short amount of time, filtering the water of plankton and attaching to boats and intake systems of water and power plants.
WHITE PERCH
They're considered a desired species in the Northeast, but not in Kansas. When they were made their way into Cheney Reservoir in the early 1990s through a contaminated stocking, they caused big problems. They quickly built huge numbers, and their huge appetite had an effect on everything from baitfish to gamefish.
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