For about two decades, several species of fish commonly known as Asian carp have been creeping up the Mississippi River and its tributaries, gobbling up food native fish need to survive.
Tales of 30-pound fish literally leaping into boats and injuring anglers would probably be just fish stories if it weren't for YouTube, and if they weren't so common.
"To me, it's surprising we haven't seen more," says fisheries biologist Peter Sorensen of the University of Minnesota. He says there are millions of Asian carp downstream — just a few days' swim away. Some can top 100 pounds. All are voracious eaters. Sorensen says they gobble up the food native fish depend on. And that's why Sorensen has declared war on Asian carp.
"I've been to areas of the world where there's not much but invasive species, and it's pretty pathetic. And I think that's really tragic," he said.
The federal government is spending millions of dollars to keep these invasive fish from moving into the Great Lakes. And now the battle has spread to Minnesota. In March, commercial fishermen caught silver and bighead Asian carp in the Mississippi River near Winona. In April, another bighead was pulled out of the St. Croix.
Here, Gov. Mark Dayton has approved using state Legacy Amendment money to fight aquatic invasive species including Asian carp. And a measure in Congress would direct federal money to help fund the fight.
But critics say an all-out war on the fish may be too expensive, and biologically unsound.
Sorensen's war could prove to be long and costly. Scientists still know very little about how Asian carp move and reproduce. And while adult silver carp living in large groups infamously rough up anxious anglers, they're hard to study because they're surprisingly difficult to track and catch in small numbers.
"It's like catching cats when you're blindfolded or something," he said." They could be all over you but you'll never get them. They swim away."
Sorensen hopes to find a way to interrupt the fishes' sense of smell, or spawning patterns — anything that could keep them from moving and reproducing. He hopes to set up a multimillion-dollar aquatic invasive species research center at the U to help him fight his battle. But in the meantime, he said it's vital to keep the fish from spreading north.
Sorensen and others fear the carp will migrate into lakes connected to the Mississippi River, such as Lake Itasca, where the river begins its journey south. The unwelcome fish could also hitch a ride elsewhere in boaters' bilgewater.
The best way to slow their spread is to close the Mississippi to boat traffic at Minneapolis, Sorensen said. And Legislation in Congress would allow the Army Corps of Engineers to do just that. Sen. Amy Klobuchar introduced a measure in March that would allow the Corps to shut down the Upper St. Anthony lock if adult Asian carp are found upstream of Hastings, or if juveniles are found north of Alma, Wis.
"These fish are a menace, and it's critical that we take quick and decisive action," she said. "We always love in Minnesota to be known as the state of 10,000 lakes. We don't want to be known as the state of 50,000 carp."
But closing part of a major river to boats has generated some strong opposition in the Twin Cities, where two big industrial users still rely on barge shipping: a scrap metal recycler, and Aggregate Industries.
BARGE TRAFFIC VITAL
On Grey Cloud Island south of St. Paul, Aggregate Industries' giant clamshell buckets scoop tons of dripping wet sand and gravel from the Mississippi riverbottom. After it dries, 400,000 tons a year are shipped through the St. Anthony Falls locks in downtown Minneapolis to a site just north of downtown. That's where another company makes concrete that has gone into everything from the new Lowry Avenue bridge nearby to Target Field less than two miles away. Aggregate Industries Senior Vice President Norm Jagger says if the river is closed, all this rock and sand will have to be hauled in trucks.
"To give you an idea, 400,000 tons would mean 20,000 extra trips of material, 20,000 trucks on our roads going from St. Paul into Minneapolis into Yard D to the downtown Minneapolis site," he said.
Giving up barge transportation would also add costs to construction projects, and add more pollution to the air, Jagger says, while adding that many employees of Aggregate Industries are anglers with lake cabins, and they all realize they might need to sacrifice river shipping to protect Minnesota's gamefish.
Greg Breining, a journalist and author of several books on nature and the environment, says Minnesotans should have to make these kinds of choices.
"There's a lot to be learned about exotic species in ecosystems. I think it's worth some research and some study. But to declare war on invasives opens up a big money pit," he asserts.
Breining is no fan of Asian carp. But he says the conventional wisdom that we have to move heaven and earth to stop one type of fish to save others is a false choice. Breining also says control efforts — whether installing electric barriers, introducing predators or closing rivers — could wind up doing more harm than good. And Breining says all this war rhetoric reinforces the myth that humans can control nature.
"It's just not very effective. It's like a war on terrorism or a war on drugs. It's just a way to spend a lot of money to no particularly beneficial end," he said.
Macalester College biologist Mark Davis agrees.
"Non-native species originally, and in many cases still are, referred to as 'invaders.' That's obviously not a neutral term," he said. There is a lot at stake with Asian carp, but the research is far from conclusive, scientists, policymakers and the public all need to be skeptical of worst-case-scenario predictions.
In the Illinois River, another place where silver carp are jumping into boats, native gamefish still survive. However a state biologist there says the natives are smaller than they used to be. That indicates competition for food, but so far Asian carp have not killed off other species. In Chicago, electric barriers are in place to keep the fish out of Lake Michigan. And officials are also trying something more low-tech: Letting commercial fishermen haul off boatloads of them for sale in Asia. It's a thriving business.
Asian carp were first imported decades ago to control algae in commercial fish farms. At the time, few foresaw the consequences. But Davis says those hoping to eradicate the fish need to weigh the environmental consequences of anything they do.
"Are [the invasives] really going to devastate the fisheries? Are they really going to drive some of these species to extinction or near-extinction? In most cases, the new species come in and actually add to biodiversity, because they usually do not drive the native species to extinction," Davis said.
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