Jumping several feet into the air, a single silver carp can knock a boat driver unconscious before a passenger even has time to say “Duck!”
For that reason, the Illinois Natural History Survey station in Havana installed netting around the steering wheel and dashboard of its electro-fishing boats.
“It’s simply one of the most dangerous things that we’re doing, so we have to protect ourselves. We can’t have a fish jumping on the throttle [or] a fish knocking somebody out,” says Kevin Irons, INHS fisheries specialist.
The invasive species has become a common sight on the Illinois River and its tributaries, including parts of the Sangamon River, but leaping silver carp are only the most visible representation of a much deeper problem – one that scientists fear will soon spread to the Great Lakes, where Asian carp threaten a $7 billion fishing and tourism industry.
“Economic damage is the fish hitting people, people not wanting to spend time on the water,” says Irons. “But the ecological damage is much worse. … People can see this and say ‘Oh my gosh, this is horrible,’ but they don’t understand the effects of having them in the water year after year after year.”
While biologists and fishermen now see Asian carp as an environmental detriment, the fish were originally brought to the country as an environmentally safe alternative to chemical treatment, Irons says. In the 1960s and 1970s, southern fish farmers imported Asian carp to help keep catfish ponds clean.
“It seemed like a good idea at the time,” Irons says. “We can use a biological control to control nutrients in our catfish ponds, our catfish is healthier, tastes better, and then you have a large fish that you can use for either cleaning up the next pond or you can use for animal feed or fertilizers.”
But once flooding washed Asian carp out of the controlled ponds and into the Mississippi River, the fish quickly became an environmental problem and have been threatening to change the ecology of major waterways ever since.
INHS’ Havana group saw its first bighead carp – the Asian carp known for weighing up to 100 pounds – in 1995, and its first silver carp in 1998, Irons says. But it wasn’t until 2000 that the fish finally started spawning on the Illinois River in great numbers. That year, through its annual sampling of 400 random Illinois River sites, INHS caught about 1,200 bighead carp and several hundred silver carp, mostly small, young specimens, Irons says.
By 2007, sampling brought in more than 10,000 silver carp. “The next year it was over 100,000 juvenile [silver carp].… Most of those are small, but if only 1 percent of those survive you can see how those numbers [rise],” Irons says.
“All that food is impacting every other fish species because all fish need plankton at some point in their life,” Irons says. While he hasn’t seen any extreme long-term population decreases in native fish species, those fish are looking much thinner than in the past.
“The populations are generally fairly robust until 2007-2008, when we thought we were seeing a tremendous crash in our bluegills and sunfish,” Irons says, adding that they hit 17-year lows during the drought-like conditions. “After that, we had good floods and those numbers have rebounded.”
While the relationship between Asian carp and the populations of other fish species is complex, it appears that when water levels are low, the impact of Asian carp is greater. At the same time, Asian carp, like other fish, have more successful spawns under flood conditions.
“It’s really dynamic,” Irons says, explaining that Asian carp have the upper hand because they can survive on the most basic form of food provided by the waterway. “When the water … provides good stuff for the bass and for the carp, they both flourish, but if water levels are low I think Asian carp might win that battle.”
Commercial fishermen say Asian carp are, indeed, taking over native populations.
“We are more or less forced to fish for these fish [Asian carp] because there’s nothing else to catch,” says Dallas City resident Kirby Marsden, president of the Illinois Commercial Fishing Association. “Our nets are coming up [with] 90 percent of these Asian carp. … Where’s our native fish?”
Guarding the Great Lakes
Scientists, fishermen and policymakers are looking to the commercial fishing industry as the most viable solution, not only for downstate Illinois but also for keeping Asian carp from crossing into the Great Lakes, and for good reason, Marsden says. “The idea, if you want to keep them out of the Great Lakes, is to catch these fish before they even get to the barrier.”
About eight years ago, the U.S. Army Corps of Engineers turned on an underwater electric barrier on the Chicago Sanitary and Ship Canal, the artificial waterway that connects the Great Lakes to the Illinois River. Engineers designed the barrier to keep non-native aquatic species, including Asian carp in the Illinois River and the invasive round goby fish in the Great Lakes, from swimming across it and damaging either water system. Since then, the Corps has added an additional electric barrier and is now working on a third in efforts to keep Asian carp from entering Lake Michigan.
Meanwhile, state and federal agencies are looking for more ways to deter the movement of Asian carp, and the Havana INHS station is now studying the effectiveness of one proposed measure.
A graduate student at the University of Illinois in Urbana-Champaign, Blake Ruebush, will soon start a second round of trials for a sound bubble barrier placed just before a dam on Quiver Creek, a tributary to the Illinois River near Havana, in an attempt to deter Asian carp from traveling further upstream. The technology uses a bubble curtain accompanied by LED strobe lights and sound frequencies that only Asian carp are sensitive to.
Last year, the equipment allowed 97 percent of the studied fish, excluding Asian carp, to still pass through the barrier while none of the marked silver carp were recaptured on the other side, suggesting 100 percent effectiveness.
But Ruebush isn’t ready to declare victory – other variables could have kept the silver carp from even wanting to approach the barrier, and he’s still trying to find out if the mechanism would work on all ages of Asian carp.
“If it is effective, I don’t know if it will be 100 percent effective,” Ruebush says. “So many things can happen.” If anything, the sound bubble barrier would be just part of a comprehensive solution, he adds.
Most stakeholders seem to agree that Asian carp can’t be eliminated entirely.
“The best we can hope for is to control their populations and right now about the only option we have available is the commercial fishing industry,” says Rob Maher, commercial fisheries biologist for the Illinois Department of Natural Resources.
Commercial fishermen have found markets in Thomson, Pearl and Chicago. Another market is across the globe in China, where Asian carp are overfished and intentionally stocked, says Irons.
In Chicago, like in other large cities across the U.S., traditional Asian populations enjoy eating Asian carp. But, throughout the rest of the U.S., people snub the abundant food source, and supply continues to outweigh demand.
“One of the problems is that they’re not native to America, so Americans are just not going to eat them,” Marsden says. “It’s just hard to get people to try them.”
Clint Carter, manager at Springfield’s Carter’s Fish Market, says Asian carp aren’t on his menus, but not because the meat isn’t good. To the contrary, he says the fish, which feed close to the water’s surface, provide clean-tasting white meat.
For fun, Carter experiments with Asian carp and serves them to his friends. “I’ve cooked them for a lot of people and haven’t had many complaints,” he says.
“But the negatives overwhelm it,” Carter says. The ‘Y’ bones that drop down on both sides of a silver carp’s body are enveloped by flesh, making it time-consuming and difficult to separate good meat from inedible bone.
Yet if the Asian carp is properly cut and fried, the bones will pop out of the meat with relative ease, Carter says. He also suggests mincing them up and making patties out of them, or smoking them. He adds that they’d make a great imitation fish.
But besides bones, Asian carp also have a public relations problem. “They’ve got the name ‘carp’ and there aren’t many people who like carp,” Carter says. When people think of carp, they think of the bottom-feeding common variety which have a darker meat, not realizing that Asian carp feed close to the surface, are less likely to hold high levels of contaminants and aren’t fishy tasting.
Despite the setbacks, in the last decade Illinois’ commercial fishing industry managed to ramp up the market for Asian carp from zero to 15 million pounds, but that’s not enough to bring native fish populations back up, Marsden says.
“We need sales for probably closer to 50 million pounds per year to actually reduce [the Asian carp population].” Marsden says that with that amount of production, commercial fishermen could reduce Asian carp populations by 95 percent within five years. In decreasing Asian carp populations, fishermen could turn their attention back to catching native fish, which would be hardier because they’d have less competition for food.
The only problems, Marsden says, are transportation costs to foreign countries and marketing in the U.S.
Cost is also a primary concern for another stakeholder. Dr. Tim Leeds, a representative of Heartland Processing, says he can make a useful product out of parts or all of an Asian carp with virtually no waste and no odor. The company, founded in 2007 by Illinois resident John Holden, makes protein supplement for animal feed using agricultural byproducts, such as the heads and guts of fish.
Last spring the company opened a “show and smell” plant, its first, in Havana to demonstrate the odorless process of grinding fish, leaving only water vapor as the waste product.
The mobile machinery Heartland Processing uses is designed as a rapid response mechanism for any biological hazard, meaning, for example, that the government could use it on location at a farm to eliminate all of the potentially infected chickens where Avian flu is present, thus stopping a national outbreak.
Leeds sees Asian carp as another type of biological hazard, and although he could make fish meal and fish oil out of Asian carp, those products don’t bring in high enough prices to make the process economical without government subsidies.
Heartland Processing shut down its Havana plant after only four months of operation, when Leeds says potential state funding fell through, but the company is back in talks with the state and other stakeholders and hopes to find a funding solution in the near future.
The story of Asian carp is a familiar tale, Irons says, pointing to a long list of other invasive species. Starlings, for instance, spread across the U.S. after literary enthusiasts in the late 1800s introduced them as homage to William Shakespeare, who mentioned the bird in his works. Starlings are now abundant and are known for taking over native birds’ nests, eating crops and, moving in large groups, leaving corrosive droppings wherever they go.
Aquatic examples of invasive species include gobies, zebra mussels, white perch and, brought to the U.S. about 130 years ago, common carp.
“[Silver carp are] kind of a poster child of invasive fish where people aren’t aware of fish,” Irons says, adding that the flying fish provide a “unique opportunity” to talk about invasive species.
“This might be a point where we can make some good legislation to prevent moving around too much. There’s certainly a platform we can talk about not dumping your bait bucket into your favorite lake.”
Do your part to prevent invasion
- Don’t take live fish from one body of water to another.
- Never use wild-caught baitfish in waters it didn’t come from.
- Know the difference between juvenile Asian carp and juvenile gizzard shad. The two look similar.
- Drain water from live wells and boat bilges before leaving the water.
Source: Asian Carp Regional Coordinating Committee, www.asiancarp.org
Contact Rachel Wells at firstname.lastname@example.org.