KANSAS CITY, Kan. — Blake Matthews and crew were under attack.
“These things don’t play by the rules,” he said as he smacked an airborne Asian carp with a boat paddle, while watching another pass inches from his face.
Matthews and two other Kansas Department of Wildlife, Parks and Tourism fisheries biologists spent about an hour Tuesday ducking fish where the Kansas River meets the Missouri River.
Hundreds of silver carp, spooked by the boat’s passing, became airborne. More than 50 landed in the boat.
Such numbers were expected.
“We have more (Asian carp) than ever and such a huge year-class from 2010 that are 15-18-inch fish,” said Jason Goeckler, Wildlife and Parks aquatic nuisance species coordinator. “Those fish have a lot of growth potential.
The confluence at Kansas City is far from the only water under attack from the piscine invaders.
Silver and bighead carp escaped into the Mississippi River system about 40 years ago. Private fish growers had imported the Asian filter-feeding fish hoping to clean contaminated waters.
Instead, they now compete with native fish that also feed on plankton. Silver carp jumping eight feet or more in the air when spooked provide a danger to boaters.
Biologists are still learning about silver and bighead carp, which can weigh 60 and 100 pounds respectively.
Duane Chapman, a U.S. Geological Survey fisheries biologist in Columbia, Mo., studies them in the Missouri River and other waters. He’s finding a complex fish that needs unique conditions to reproduce and survive, but can do exceptionally well when all is right.
Asian carp need fast-moving water for good spawning conditions. According to Chapman, the Missouri River is “an ideal place.”
Highly turbulent waters where wing-dams reach into the river are often good spots. High water from heavy rains in 2010 and 2011 made conditions even better.
It also made it difficult for big carp to feed, too.
“Adult fish require deep water that is not flowing or not flowing much,” Chapman said. “If the water’s muddy they can’t eat. We were losing (adult) bigheads left and right because of the high (fast) water. It got to where it was hard to go out and find bighead carp for a while.”
Competing with millions of freshly-hatched Asian carp probably added to the mortalities. But Chapman said many fingerlings often die before they get larger.
Young silver and bighead carp need to spread into shallow and calm backwaters to feed and grow quickly.
Such waters are often rare along the Missouri, except for when flood waters spread across bordering farm fields, often giving the young fish plenty of time to grow.
Sometimes, though, waters recede too quickly, stranding thousands fish in low spots. “When those places eventually went dry, it was like there was this band of silver around the edges,” Chapman said. “That was from all of the dead carp.”
Even with such odds stacked against the invasive species, reproducing longevity is on its side.
“It’s nothing for them to live 25 years,” Chapman said. “They only need to get off a good spawn every 20 years and they can sustain their populations.”
And successful spawns can produce some astronomical numbers of fish. In 2010, one school of four-inch long yearlings below a small dam in Kansas was estimated at up to 400,000 fish.
Goeckler said those fish, which have grown to 15-18 inches in two years, are the main reason the overall population has increased significantly in the lower Kansas River system.
Also, the Asian carp spawn is spread through several months, increasing the chances that some of the fish will hit ideal conditions.
All those little mouths compete with more than just bigger Asian carp for plankton, too.
A little good, a lot of bad
Plankton feeders like paddlefish, bigmouth buffalo and gizzard shad can see population or health declines when Asian carp numbers are high. Catfish in waters with Asian carp seem to be the least affected.
Strong Asian carp spawns come with a few positives, though.
Kevin Irons, of the Illinois Department of Natural Resources, said gamefish like largemouth bass and crappie have fed heavily on small Asian carp.
Much of his research has been done in the Illinois River, probably America’s best habitat for the invasive species.
Irons said the protracted spawning times for Asian carp helps keep fry available throughout the summer for gamefish.
Irons isn’t aware of any species totally eliminated because of competition with Asian carp, though some have seen major changes.
“We’ve seen largemouth bass go from the lowest numbers seen in 20 years to some of the highest seen. Right now they look really good,” he said. “But all those very small (Asian carp) are a double-edged sword. That’s a lot of food, but there’s nothing out there that can eat them fast enough.”
Eventually the young fish grow too large to be a food source for native fish, while becoming a serious competitor for plankton for many years with native fish.
Possibly the biggest problem could be if the fish got established in reservoirs, according to Chapman and Goeckler. Chapman fears what could happen if the fish reproduce in a reservoir. Where that might happen is still a mystery.
“It’s going to take a fairly long tributary, in the ballpark of 60 miles of river for them to pull off a spawn,” he said. “What we don’t know is how small of a river they might spawn in when it’s that long. In most places they won’t be able to reproduce, but all they need is the occasional spawn and they could take over.”
Chapman pointed to Missouri’s Truman Reservoir as a prime candidate for possible spawning grounds. The lake is large and fed by several river systems. Goeckler said Perry, Tuttle Creek and Milford Reservoirs could be possibilities in Kansas.
Any kind of Asian carp population could impact pleasure boating use. Chapman doesn’t overlook the threat silver carp pose to human safety. Though he’s not aware of any fatalities attributed to jumping fish hitting boaters, he has heard of broken jaws and other injuries.
He was smacked in the face by a fish that left him sore for many weeks.
“If it had been an inch lower I’d have lost some teeth,” Chapman said.
He also witnessed the adult driver of a boat come within inches of getting knocked from the craft by a big silver carp. Had that happened, a boat filled with kids would have been rocketing out of control down the river.
High carp populations could quickly cripple sport fishing in reservoirs.
“The fish I really worry about are crappie, white bass, walleye and anything else that lives in the middle of the lake as small fish. They can’t win in a competition with Asian carp,” Chapman said, adding some species of European walleye and perch have already suffered under such conditions.
Most states and federal agencies are doing all they can to prevent the spread of Asian carp to new waters. They’re also trying to figure out how to utilize existing populations. The fish have several uses, including in pet food and fish oil-based vitamins. Both species are tasty, though they have many problematic bones.
The difficulty is finding affordable ways to turn silvers and bigheads into useful products. Chapman said few companies are buying Asian carp, and it doesn’t take many fishermen long to fill those few orders from the Illinois River.
The fish don’t have a huge following in the U.S., unlike in Asia. Some fish are being flash-frozen and shipped to places like China. But it’s a tough market.
“These fish are the hot dog of China. They eat a lot of them but they don’t bring a very good price,” Chapman said. “They usually want their fish fresh instead of frozen. (Asian carp) are also the most aqua-cultured fish in the world. They raise millions of pounds of them per year in Asia.”
Chapman hopes markets will be developed in the U.S, and they’ll be utilized in as many ways as possible. Government funds may be needed.
“We’ll probably establish at least some level of human consumption, then we could use the offal for pet food or to make Omega 3s,” he said. “You can’t make any money off these fish right now without some subsidies, though.”