Mrs. O’Leary’s Cow, Meet the Asian Carp

At the rate of 35 miles a year, the carp have migrated north, leaping so high at times they have smacked the boat-borne fishermen and researchers in the face.

They are almost here now and, beyond their unexplained aerial assaults, pose what biologists believe may be a major ecological threat to North America’s largest water system.

Fat, voracious and with a complexion only a dermatologist could love, Asian carp are just 25 miles from this city’s downtown entryway to the Great Lakes. The only thing standing in their way is an experimental electrical curtain.

As long as 5 feet and weighing up to 110 pounds, the carp eat as much as half their body weight daily in plankton, the same food virtually every other fish in the lakes eats when it is young. They breed so quickly that Australian biologists call them “river rabbits.”

“They could essentially wipe out the base of the food chain in the entire Great Lakes,” said Dennis Shornak of the International Joint Commission, which oversees water systems that affect both the United States and Canada. “We could honestly end up in a situation where the Great Lakes are nothing more than a carp pond.”

With the fish approaching, the commission has taken to lobbying the highest levels of the U.S. and Canadian governments for help, including Secretary of State Colin L. Powell, since the issue is of international concern. But many fishery biologists are skeptical that the carp can now be kept out of the Great Lakes and are beginning to consider how to mitigate the damage.

Mitigation has become the less-than-ideal method of battling other invasive species that couldn’t be kept out of the Great Lakes, such as the zebra mussel, which made its way from Europe in the 1980s, transported in the ballast water of ships.

No longer does anyone expect to rid the lakes of zebra mussels, only to continue fighting the creatures, which attach themselves to ship hulls, bridge pilings, other mussels and drinking-water intake systems. The bill for fighting the mussels throughout the lakes: $3 billion in just a decade.

Asian carp, scientists fear, could do exponentially more damage than zebra mussels or any other of a handful of invasive species in the Great Lakes, including sea lampreys, which decimated trout populations 50 years ago. They are likely to compete for food with such commercial fish as paddlefish, gizzard shad, bigmouth buffalo, and virtually every other fish while they’re in a larval stage. And once they get in, there is no getting them out.

They pose another problem. These fish can jump--more than 12 feet out of the water.

“It’s not a phenomenon you have to wait for,” said Pam Thiel, a fishery expert for the U.S. Fish and Wildlife Service in La Crosse, Wis. “Just go to a place where they are dense and they will be flying.”

A most impressive sight, from afar.

“They don’t mix well with water-skiers, jet-skiers and boaters,” Thiel added.

Some commercial fishermen have taken to protecting themselves from incoming carp with cookie sheets or garbage can lids. A fisherman on the Kaskaskia River in southern Illinois suffered a broken nose when one leaped into his face.

Virtually every researcher for the Illinois Natural History Survey, which studies area fisheries, has taken at least one carp hit, said Kevin Irons, a river ecologist with the group. One ichthyologist, who already had been whacked several times, was injured so badly during a recent flying-carp encounter that he is receiving medical treatment.

With large, mottled scales and eyes that seem to have slid halfway down their faces, Asian carp are considered trash fish of the lowest order in the West.

Although their white, low-oil meat is rather tasty, many agree, the fish--probably because it is a carp--has never gained a market in North America beyond the Chinatowns in a few major cities. And even where there is a market, the fish must be trucked there alive because, as with lobsters, connoisseurs prefer them fresh.

The much-maligned carp do have a place to call home. Halfway around the world in East Asia, the arrival of a migratory school would likely be greeted not by an electric shock but a celebration.

In much of China, carp are not only a food staple but symbols of strength for their mythic ability to leap the entire rapids of the Yellow River, and perseverance for their actual talent at swimming upstream. They are common images in watercolors and other artwork, often pictured leaping high out of the water, twisting in the air with gusto and grace.

Two species of Asian carp, bighead and silver, are the primary cause of concern here. Imported by Arkansas fish farmers in the early 1970s for their skill as underwater vacuums, the carp were slipped into catfish ponds to gobble up algae blooms.

The fish escaped, as it were, during heavy floods in the early 1990s, making their way out of the ponds and into tributaries of the Mississippi River. They swiftly swam north.

In 1999, according to a study by the Natural History Survey, researchers found not a single bighead carp in the Illinois River, a tributary of the Mississippi River, though they were appearing with ever-increasing frequency downstream in the Mississippi. The next year the scientists discovered more than 1,400 of the fish at a single site in the Illinois.

“They went from being nonexistent to being one of the most common fish in the river,” Irons said. “We don’t know much about these guys yet. What we do know is an adult female will lay millions of eggs a year, and the populations have the potential to grow dramatically.”

The Illinois connects to the Chicago River, which connects to Lake Michigan, which in turn connects directly or indirectly to all of the other Great Lakes. The carp migration is now less than a year’s swim from Lake Michigan, though individual fish could make the trek in a day or two.

The Army Corps of Engineers is trying to halt their progress with an electrical current at a site in the Chicago Sanitary and Ship Canal. In April, the corps laid a series of charged cables across the artificial bottom of the canal and flipped the switch, sending a current that the fish find less than pleasant all the way to the surface.

The unproven electrical curtain, however, doesn’t even have a generator in case of a power outage--a regular summertime occurrence in Chicago.

Such electrical walls have proved effective in the laboratory and in small natural settings in turning fish back, but they have never been employed on anything close to this scale. Chicago Mayor Richard M. Daley is asking Congress for $700,000 for a generator to keep the curtain live in case of a blackout, and to build a second barrier, perhaps using bubbles or a wall of sound to keep the carp at bay.

Of course, many researchers believe it entirely likely that some fish could simply jump the barrier.

Ironically, if it were not for a massive tinkering with nature more than a century ago, the fish would have no way of swimming from the Mississippi into the Great Lakes in the first place.

The Chicago River, which runs through the heart of the city, used to have no connection with the Mississippi drainage. And it used to flow in the other direction.

In the late 19th century, Chicago dumped its sewage, waste water and the carcasses from its sprawling slaughterhouses into the Chicago River, which flowed into Lake Michigan. The problem was, the city also obtained its drinking water from Lake Michigan. Chicagoans were dying in droves from the poisoned lake water.

With large-scale environmental consciousness still decades in the future, the city and federal governments decided not to clean up the river but to turn it around, sending all the fetid materials west, into the Mississippi.

Workers built a lock at the river’s entrance to Lake Michigan, dug a series of artificial canals connecting to the Illinois River, and reversed the Chicago River’s flow.

With the carp almost here, scientists are considering every option, including one being tested in Australia, where several waterways have been invaded: gender selection.

Altering an enzyme in female carp that helps determine sex, the Australian scientists are seeing whether they can get carp mothers to give birth to considerably more males than females. In theory, the ratio of male to female carp would grow so lopsided in favor of the males that the population would collapse.

That’s only in theory, however. Even on paper, the method takes decades to play out.

Meanwhile, scientists here are hoping for funding to build the redundant barrier not far from the existing one, near the Chicago suburb of Romeoville, in case the initial wall doesn’t stop the carp. Researchers for the Natural History Survey frequently send electric charges into the water to stun fish and bring them to the surface for study. Irons, who pilots a research boat, has installed a special mat that he stands on while at the wheel.

If a carp knocks him into the water, the sudden reduction in weight on the pad will shut down any electric currents the scientists are sending into the river, so he won’t be electrocuted.

“I had one come at me like a football recently--and this is a six- or seven-pound fish,” Irons said. “Man, this one was a missile.”