For about two decades, several species of fish commonly known as Asian carp have been swimming up the Mississippi River. The non-native fish, imported to help control algae in commercial fish farms, have been gobbling up food native fish need to survive. The U.S. government is spending millions to keep these invasive species from migrating through Chicago to the Great Lakes. And now the battle has spread north to Minnesota. However, critics say an all-out war on the Asian carp could be expensive and biologically unsound.
Tales of 14-kilogram fish leaping into boats and injuring anglers would probably be just a myth if it weren't for YouTube, the online site where fisherman have posted dozens of “flying Asian carp” videos, and a slew of TV news reports.
While you might expect sport fishers would be delighted to have their catch literally jumping into their boats, it is actually the last thing anglers in Minnesota want. They're worried by the news that commercial fishermen caught Asian carp in the Mississippi River, in southeastern Minnesota, this past March. In April, another turned up in a tributary nearby.
"To me, it's surprising we haven't seen more," says fisheries biologist Peter Sorensen from the University of Minnesota.
According to Sorensen, there are millions of Asian carp just downstream in Iowa. Some can top 45 kilograms. They’re big eaters and compete with native fish for food, which is why Sorensen he 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," he says. "And I think that's really tragic."
But scientists still know very little about how Asian carp move and reproduce. At his lab, Sorensen has several huge tanks full of the fish. He hopes to find a way to interrupt their sense of smell or spawning patterns, anything to keep them from migrating and breeding. But in the meantime, he says it's vital to prevent the fish from spreading farther north.
Sorensen fears Asian carp will move into Minnesota’s famed 10,000 lakes region and decimate native fish. He says the best way to slow Asian carp is to close the northern end of the Mississippi River to boat traffic.
U.S. Senator Amy Klobuchar introduced a measure in Congress that would allow a lock in Minneapolis to be shut down if just one adult Asian carp is found nearby. The Minnesota lawmaker says the fish are a major threat to her state’s tourism industry, which relies heavily on sport fishing.
"These fish are a menace, and it's critical that we take quick and decisive action," Klobuchar says. "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."
However, the lock-closure plan has its critics. Industrial users say banning barges would mean more trucks on the road. And Greg Breining - a journalist and author of several books on nature and the environment - says drastic steps to eliminate the fish could be expensive and futile.
"I think it's worth some research and some study," Breining says. "But to declare war on invasives opens up a big money pit."
Breining says control efforts - whether installing electric barriers, introducing predators or closing rivers - could wind up doing more harm than good. And he says the war rhetoric reinforces the myth that humans can control nature.
"It's just not very effective," he says. "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."
Biologist Mark Davis at Macalester College in St. Paul, Minnesota, agrees. He says scientists and policymakers need to be skeptical of worst-case-scenarios. Davis concedes there could be a lot at stake with Asian carp. But he says the research is far from conclusive.
"Are they 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 says.
In the Illinois River, another place where silver carp are jumping into boats, native fish appear to be surviving. However, a local biologist says the natives are smaller than they used to be, indicating they are competing less successfully for food. But so far, Asian carp have not killed them off.
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.
When Asian carp were first imported decades ago, few foresaw their environmental impact. Today, critics say those hoping to eradicate Asian carp could learn from that experience, and consider the costs and unintended consequences of their campaign.