Each of the famous four has its own special talent, and when they join forces, they are, like the Fantastic Four, pretty much unstoppable. Grass carp (Ctenopharyngodon idella) eat aquatic plants. Silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) are filter feeders; the two fish suck water in through their mouths and then rake out the plankton using comb-like structures in their gills. Black carp (Mylopharyngodon piceus) eat mollusks, like snails. Throw farm clippings into a pond and the grass carp will eat them. Their waste will promote algae growth. The algae will then feed silver carp and also tiny aquatic animals, like water fleas, the preferred diet of bighead carp. This system has allowed the Chinese to harvest immense quantities of carp—almost fifty billion pounds in 2015 alone.
In the sort of irony the Anthropocene teems with, the number of free-swimming carp in China has crashed even as pond-raised populations have soared. Thanks to projects like the Three Gorges Dam, on the Yangtze, river fish are having trouble spawning. The carp are thus at once instruments of human control and victims of it.
The four famous fish ended up in the Mississippi, at least in part, owing to Silent Spring—another Anthropocene irony. In the book, whose working title was The Control of Nature, Rachel Carson denounced the very idea.
“The ‘control of nature’ is a phrase conceived in arrogance, born of the Neanderthal age of biology and philosophy, when it was supposed that nature exists for the convenience of man,” she wrote. Herbicides and pesticides represented the very worst kind of “cave man” thinking—a club “hurled against the fabric of life.”
The indiscriminate application of chemicals was, Carson warned, harming people, killing birds, and turning the country’s waterways into “rivers of death.” Instead of promoting pesticides and herbicides, government agencies ought to be eliminating them; “a truly extraordinary variety of alternatives” were available. An alternative Carson particularly recommended was setting one biological agent against another. For instance, a parasite could be imported to feed on an unwanted insect.
“In that book the problem—the villain—was the broad, almost unrestricted use of chemicals, particularly the chlorinated hydrocarbons, like DDT,” Andrew Mitchell, a biologist at an aquaculture research center in Arkansas who’s studied the history of Asian carp in America, told me. “So that’s the context of all this: How are we going to get rid of this heavy chemical usage and still have some sort of control? And that probably has as much to do with the importation of carp as anything. These fish were biological controls.”
One year after Silent Spring’s publication, in 1963, the U.S. Fish and Wildlife Service brought the first documented shipment of Asian carp to America. The idea was to use the carp, much as Carson had recommended, to keep aquatic weeds in check. (Weeds like Eurasian watermilfoil—another introduced species—can clog lakes and ponds so thoroughly that boats or even swimmers can’t get through.) The fish were baby grass carp—“fingerlings”—and they were raised at the agency’s Fish Farming Experimental Station in Stuttgart, Arkansas. Three years later, biologists at the station succeeded in getting one of the carp—now grown—to spawn. Thousands more fingerlings resulted. Pretty much immediately, some escaped. Baby carp made their way into the White River, a tributary of the Mississippi.
Later, in the 1970s, the Arkansas Game and Fish Commission found a use for silver and bighead carp. The Clean Water Act had just been passed, and local governments were under pressure to comply with the new standards. But a lot of communities couldn’t afford to upgrade their sewage-treatment plants. The Game and Fish Commission thought that stocking carp in treatment ponds might help. The carp would reduce the nutrient load in the ponds by consuming the algae that thrived on the excess nitrogen. For one study, silver carp were placed in treatment lagoons in Benton, a suburb of Little Rock. The fish did indeed reduce the nutrient load before they, too, escaped. No one is quite sure how, because no one was watching.
“At the time, everybody was looking for a way to clean up the environment,” Mike Freeze, a biologist who worked with carp at the Arkansas Game and Fish Commission, told me. “Rachel Carson had written Silent Spring, and everybody was concerned about all the chemicals in the water. They weren’t nearly as concerned about non-native species, which is unfortunate.”
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The fish—mostly silver carp—lay in a bloody heap. There were scores of them, and they’d been tossed alive into the boat. I’d been watching them pile up for hours, and while the ones at the bottom were, I figured, by now dead, those on top continued to gasp and thrash. I thought I could detect an accusatory glint in their low-set eyes, but I had no idea if they could even see me or whether this was just projection.
It was a sultry summer morning a few weeks after my trip on City Living. The gasping carp, a trio of biologists employed by the state of Illinois, several fishermen, and I were all bobbing on a lake in the town of Morris, about sixty miles southwest of Chicago. The lake had no name, having started off as a gravel pit. To get access to it, I’d had to sign a release form from the company that owned it, stating that, among other things, I was not carrying any firearms and would not smoke or use “flame-producing devices.” The form showed the outline of the pit-turned-lake, which looked like a child’s drawing of a tyrannosaurus. Where the tyrannosaurus’s navel would be, if tyrannosauruses had had navels, was a channel linking the lake to the Illinois River. This arrangement accounted for the carp. Carp need moving water to reproduce—either that or injections of hormones—but once they’re done spawning, they like to retreat to slack water to feed.
Morris might be thought of as the Gettysburg in the war against Asian carp. South of the town, the carp are legion; north of it they are rare (though how rare is a matter of debate). A great deal of time, money, and fish flesh are devoted to trying to keep things this way. The process is known as “barrier defense,” and it’s supposed to prevent large carp from reaching the electric barriers. If electrocution were a fail-safe deterrent, then barrier defense wouldn’t be necessary, but no one I spoke to, and this included officials like Shea, at the Army Corps of Engineers, seemed eager to see the technology put to the test.
“Our goal is to keep carp out of the Great Lakes,” one of the biologists told me as we floated over the former gravel pit. “We’re not depending on the electric barriers.”
At the start of the day, the fishermen had set out hundreds of yards of gill net, which they were now pulling in from three aluminum boats. Native fish—flathead catfish, say, or freshwater drum—that got caught in the net were disentangled and tossed back into the lake. Asian carp got thrown into the center of the boats to die.
In the nameless lake, the supply of carp seemed endless. My clothes and also my notebook and tape recorder were spattered with blood and slime. No sooner were the nets hauled in than they were reset. When the fishermen needed to get from one end of their boats to the other, they’d simply wade through the writhing carp in the middle. “Who hears the fishes when they cry?” Thoreau asked. “It will not be forgotten by some memory that we were contemporaries.”
The very same qualities that have made the “domestic fishes” famous in China have made them infamous in the United States. A well-fed grass carp can weigh more than eighty pounds. In a single day it can eat almost half of its body weight, and it lays hundreds of thousands of eggs at a time. Bigheads can, on occasion, weigh as much as a hundred pounds. They have bulging brows and look as if they were nursing a grudge. Lacking a true stomach, they feed more or less continuously.
Silver carp are equally voracious; they’re such effective filter feeders that they can strain out plankton down to four microns across—a quarter of the width of the finest human hair. Just about wherever they show up, the carp outcompete the native fish until they’re practically all that’s left. As the journalist Dan Egan has put it: “Bighead and silver carp don’t just
invade ecosystems. They conquer them.” On the Illinois River, Asian carp currently make up almost three-quarters of the fish biomass, and on some waterways the proportion is even higher. The ecological damage, meanwhile, extends beyond fish; black carp, which feed on mollusks, are, it’s feared, pushing already-threatened freshwater mussels over the edge.
“North America has the most diverse assemblage of mussels of any place in the world,” Duane Chapman, a research biologist with the U.S. Geological Survey who specializes in Asian carp, told me. “Many species are endangered or already extinct. And now we’ve essentially dumped the world’s most efficient freshwater molluscivore on some of the most endangered mollusks.”
One of the fishermen I met in Morris, Tracy Seidemann, was wearing a pair of waterproof overalls that were smeared with gore and a T-shirt with the sleeves cut off. I noticed that he had a tattoo of a carp on one of his sunburned arms. It was, Seidemann told me, a common carp. Common carp, too, are invasive. They were introduced from Europe back in the 1880s and probably wreaked their own kind of havoc. But they’ve been around so long, people have grown accustomed to them. “I should have put an Asian carp there, I guess,” he said, shrugging.
Seidemann told me he used to catch mainly buffalo, which are native to the Mississippi River and its tributaries. (Buffalo look a bit like carp but belong to an entirely different family.) When Asian carp arrived, buffalo populations plummeted. Now Seidemann makes most of his income from contract killing for the Illinois Department of Natural Resources. It seemed rude to ask him how much, but later I learned that contract fishermen can gross more than $5,000 a week.
At the end of the day, Seidemann and the others loaded their boats on trailers and, with the carp still in them, drove into town. The fish, now inert and glassy-eyed, were dumped into a waiting semi-trailer.
This round of barrier defense continued for another three days. The final tally was six thousand four hundred and four silver carp and five hundred and forty-seven bighead. Collectively, the fish weighed more than fifty thousand pounds. They were shipped west in the semi, to be ground into fertilizer.
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The Mississippi River’s drainage basin is the third largest in the world, exceeded in area only by the Amazon’s and the Congo’s. It stretches over more than 1.2 million square miles and encompasses thirty-one states and slices of two Canadian provinces. The basin is shaped a bit like a funnel, with its spout sticking into the Gulf of Mexico.
The Great Lakes’ drainage basin is also vast. It extends over three hundred thousand square miles and contains eighty percent of North America’s fresh surface water supply. This system, which has the shape of an overfed seahorse, drains east into the Atlantic, by way of the St. Lawrence River.
The two great basins abut each other, but they are—or were—distinct aquatic worlds. There was no way for a fish (or a mollusk or a crustacean) to climb out of one drainage system and into the other. When Chicago solved its sewage problem by digging the Sanitary and Ship Canal, a portal opened up, and the two aquatic realms were connected. For most of the twentieth century, this wasn’t much of an issue; the canal, loaded with Chicago’s waste, was too toxic to serve as a viable route. With the passage of the Clean Water Act and the work of groups like the Friends of the Chicago River, conditions improved, and creatures like the round goby began to slip through.
In December 2009, the Corps shut down one of the electrical barriers on the canal to perform routine maintenance. The nearest Asian carp was believed to be fifteen miles downstream. Still, as a precaution, the Illinois Department of Natural Resources dosed the water with two thousand gallons of poison. The result was fifty-four thousand pounds of dead fish. In the mix, one Asian carp—a twenty-two-inch-long bighead—was discovered. Doubtless many fish had sunk to the bottom before they could be netted. Were there more Asian carp among them?
The Chicago River’s reversal connected two great drainage basins.
The reaction from neighboring states was fierce. Fifty members of Congress signed a letter to the Corps, expressing their dismay. “There may be no greater threat to the ecosystem of the Great Lakes than the introduction of the Asian carp,” the letter said. Michigan filed a lawsuit, demanding that the link between the drainage systems be broken. The Corps studied the options and then, in 2014, released a two-hundred-thirty-two-page report.
According to the Corps’ assessment, reimposing “hydrologic separation” would, indeed, be the most effective way to keep carp out of the Great Lakes. It would also, in the Corps’ estimate, take twenty-five years—three times as long as the original digging of the canal had—and cost up to $18 billion.
Many experts I spoke to said the billions would be money well spent. They pointed out that each of the two drainage basins has its own roster of invasives, some, like the carp, brought over intentionally, but most introduced accidentally, in ballast water. On the Mississippi side, these include: Nile tilapia, Peruvian watergrass, and convict cichlid from Central America. On the Great Lakes side are: sea lamprey, threespine stickleback, fourspine stickleback, spiny waterflea, fishhook waterflea, New Zealand mud snail, European valve snail, European ear snail, greater European pea clam, humpbacked pea clam, Henslow pea clam, red swamp crayfish, and bloody red shrimp. The surest way to control the invaders would be to plug the canal.
But no one who spoke up for “hydrologic separation” said they thought it would ever happen. To re-replumb Chicago would mean rerouting the city’s boat traffic, redesigning its flood controls, and revamping its sewage-treatment system. There were too many constituencies with a vested interest in the way things were. “Politically, it just would never move,” the leader of one group that had pushed for separation but had eventually given up on the idea told me. It was a lot easier to imagine changing the river once again—with electricity and bubbles and noise and anything else anyone could dream up—than changing the lives of the people around it.
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The first time I got hit by a carp was near the town of Ottawa, Illinois. It felt like someone had slammed me in the shin with a Wiffle-ball bat.
What people really notice about Asian carp—what literally leaps out at them—is that silver carp jump. One noise that sends them jumping is the thrum of an outboard motor, so waterskiing in carp-infested areas of the Midwest has become its own version of an extreme sport. The sight of silver carp arcing through the air is at once beautiful—like attending a piscine ballet—and terrifying—like facing incoming fire. One of the fishermen I met in Ottawa told me he’d been knocked unconscious by an encounter with a flying carp. A second said he’d long ago lost track of his carp-related injuries, because “you pretty much get hit every day.” A woman I read about was knocked off her Jet Ski by a carp and survived only because a passing boater noticed her life jacket bobbing in the water. Countless videos of carp acrobatics are available on YouTube, with titles like “Asian Carpocalypse” and “The Attack of the Jumping Asian Carp.” The town of Bath, Illinois, which sits on a particularly carp-rich stretch of river, has tried to cash in on the mayhem by holding an annual “redneck fishing tournament,” which participants are encouraged to attend in costume. “Protective gear is highly recommended!” the tournament’s website advises.
Silver carp, when startled, fling themselves out of the water.
The day I got hit, I was out on the Illinois River with another group of contract fishermen doing “barrier defense.” Also on the trip were several other tagalongs, including a professor named Patrick Mills. Mills teaches at Joliet Junior College, which is just a few miles from the spot where the Corps is hoping to erect its “disco” noise-and-water-jet barrier. “Joliet is kind of the tip of the spear,” he told me. He was wearing a Joliet Junior College baseball cap with a GoPro camera clipped to the bill.
Mills was one of several people I met in Illinois who,
for reasons that were not always entirely clear to me, had decided to throw themselves into the fight against Asian carp. A chemist by training, he’d developed a special kind of flavored bait that was supposed to attract carp to the nets. With the help of a local confectioner, he’d produced a truckload of prototypes. These were the size and shape of bricks and made mostly of melted sugar. “It’s a bit MacGyvered,” Mills acknowledged.
The flavor being tested on this day was garlic. I sampled one of the baits, and it tasted, not unpleasantly, like a garlicky Jolly Rancher. Mills informed me that the following week would be devoted to anise. “Anise is a very good river flavor,” he said.
Mills’s work had attracted the interest of the U.S. Geological Survey, and a research biologist had come up from Columbia, Missouri—a six-hour drive—to see how the trials were going. The candymaker who’d helped make the baits had come, too, and so had his wife. The Illinois River at this point, about eighty miles from Chicago, was wide and untrafficked. A pair of bald eagles soared overhead, and fish jumped around and sometimes into the boat. Everyone seemed in a festive mood, except for the fishermen, for whom this was, so to speak, just another day at the office.
A few days earlier, the fishermen had set out a couple of dozen hoop nets, which look and function like wind socks. (The nets expand when there’s water flowing through them and collapse when there isn’t.) Half of the hoop nets had been baited with Mills’s bricks, which hung in little mesh bags. The hope was that the baited nets would attract more carp. The fishermen made no secret of their skepticism. One of them griped to me about the smell of the carp candy, a complaint I found curious since the odor it was competing with was the stench of dead fish. Another rolled his eyes at what he saw as a waste of money.
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