Most bass anglers realize that Asian carp pose a threat to the nation's sport fisheries. But they know that because of what they have read and heard, not because of what they've seen and experienced. For them, the danger is theoretical, especially since most of the focus has been on possible consequences to the Great Lakes if/when these large and prolific exotics gain entrance there.
Bighead and silver carp, however, already are damaging bass fisheries and showing up in frightening numbers in others. In southern Illinois, Kentucky, and Tennessee, the invasion has begun and casualties are mounting.
"Once you needed 12 to 20 pounds to win a tournament on the Kaskaskia (Mississippi River tributary south of St. Louis)," said Rick Brynes, who runs the Angler's Choice Tournament Trail. "But now that's gone, and we're starting to see the same thing on the Smithland Pool (Ohio River). During the past three to four years, the weights have dropped dramatically.
"It's a crisis, and not enough anglers see it," added the Illinois fisherman who has been pressing officials and agencies for action and sounding the alarm to everyone who will listen. "We're going to lose our fisheries. It's just going to take longer in some places than others."
In Kentucky, guide Jim Perry said that "zillions" of young-of-the-year carp are showing up along the shorelines below both Kentucky and Barkley dams. "Plus there are schools of them above those dams all around the intakes, where the water goes down to the generators," he added.
Steve McCadams, another guide, added crappie anglers are worried about carp eating up all of the zooplankton and algae that young-of-the-year typically feed on. "Our overall crappie fishery has experienced some declines the last few years as to catch rates and recruitment," he said.
Kentucky fisheries chief Ron Brooks pointed out that little data exists regarding the impacts of Asian carp on native species. "We have ancillary information concerning their effect on paddlefish," he said, adding that Illinois has evidence of harmful impacts to buffalo, and pelagic sport fish, such as sauger, in the Illinois River.
"We also are seeing fewer shad and skipjack in our tailwaters in western Kentucky," the fisheries chief said. "The real problem with measuring impacts of Asian carp in fertile waters is that they may be very subtle until a certain point of density is reached when a system is finally depleted, or nearly depleted, of algal and invertebrate forage. We are hoping to avoid reaching that threshold."
Arguably thresholds already have been reached on portions of the Missouri and Illinois Rivers, where net sampling has revealed Asian carp now comprise more than 95 percent of the biomass. In other words, those waters contain less than 5 percent native species by weight. Notorious for leaping when frightened, the silver carp also has made boating hazardous in these places, especially in the Illinois River below Peoria.
Riverine fish in their native China, silver and bighead carp spread in every direction after escaping Mississippi Delta aquaculture facilities because of flooding during the 1970s. Prolific, voracious, and fast-growing, they overwhelmed those Midwest waters first. They did so by gobbling up phytoplankton and zooplankton, which is critical forage not just for shad, paddlefish, and buffalo, but for fry of sport fish, including crappie and bass.
"Between 1994 and 1997 commercial catches of bighead carp in the Mississippi River increased from 5.5 tons to 55 tons," reported the Tennessee Wildlife Federation. "Today, commercial fishers in the Illinois River regularly catch up to 25,000 pounds of bighead and silver carp per day.
And while most attention was focused on the fear that the invaders might migrate into the Great Lakes via a manmade connection between Lake Michigan and the Illinois River, they quietly pushed east into the Ohio. That gave them entrance to the Tennessee River and Kentucky Lake, as well as Lake Barkley and the Cumberland system. Now, their numbers are exploding in those reservoirs, even as they have been found as far up the Cumberland as Old Hickory and as far up the Tennessee as Watts Bar.
"Personally, I think it's too late to fully save the Mississippi and Ohio Rivers. The quantity of carp in both those rivers is unimaginable, although, sustained fishing does help," said Ben Duncan, a commercial fisherman, as well as high school mathematics teacher. "If we don't start soon, the Tennessee and Cumberland Rivers will soon follow."
Duncan added that he already sees how native fish have changed their behavior because of the carp invasion. "I think it's even influenced the crappie population and spawn on Kentucky Lake," he said. "Commercially, we catch way fewer fish in the bays than we did seven to eight years ago, especially buffalo, a fish that competes with Asians for food."
Even more concerning, they are growing to sizes never before seen, even in their native China. Earlier this year, Bill Shroeder foul-hooked and landed a 106-pound silver carp in Kentucky Lake. Fisheries experts say the maximum weight for that species should be about 60 pounds.
What's being done to protect sport fisheries in these imperiled waters? Not enough, stressed Byrnes, who has pressed the U.S. Geological Survey (USGS), the U.S. Fish and Wildlife Service, and other agencies to explain why they are not more aggressively exploring and implementing strategies to manage Asian carp.
"Things could be done to eradicate them that are not being done," he said, adding that lack of funding seems a contributing factor.
"We're 25 years into this, and we need some action now," the Illinois angler said. "Asian carp can take over and change our fisheries forever."
While resource agencies aren't responding to the Asian carp threat as quickly as some would like, they are working on control methods, according to Michael Hoff with the U.S. Fish and Wildlife Service.
"It is unlikely, in my experience, that any technology will be the end all," he said. "That is why we, in the U.S. agencies, are researching and developing a variety of containment and control technologies that are feasible now, and may be implemented within the next few years."
Any strategies, he added, must take into account "a variety of scientific, social, political, and environmental constraints."
Genetic modification is one option. It would require stocking hundreds of thousands of altered carp to breed with the existing population to cause reproductive failure, reduced fertility, or ineffective recruitment. But concerns about the effects of genetically modified animals on the environment and humans makes this option less likely. Variations that do not require modification of the nuclear genome also are being explored, but they likely would work only where densities are low.
Distribution of "microparticles" that only silver and bighead carp would eat seems a more likely strategy.
"Those microparticles are being developed to kill only Asian carp," Hoff said. "I am hopeful that the microparticle technology will be approved for use within the next several years."
As research continues on methods to control Asian carp populations, Kentucky and Tennessee have followed the lead of Illinois in promoting commercial harvest. The mild-flavored fish is highly prized for food in Asian, and slowly is growing in popularity in the United States. Additionally, meal made from carp can be used in livestock food, as well as fertilizers.
Kentucky fisheries chief Ron Brooks said that Riverine Fisheries International, LLC has retrofitted a salmon processing ship to accommodate carp and now is towing it to his state from New Orleans. "The owner has a very aggressive plan of attack concerning fishing the carp and expects to eventually haul in about 150,000 pounds of Asian carp daily," he said, adding that he knows of at least two other processors.
"The good thing about the larger companies is their interest in Asian carp in Kentucky and Barkley Lakes," Brooks added. "The carp grow faster and are more robust in those reservoirs than they are in the rivers. They pose immediate threats not only to the fisheries, but boaters as well."
Tennessee, meanwhile has no major processors as of yet, but the Tennessee Wildlife Resources Agency (TWRA) "proposes to use commercial fishing methods to remove large volumes of bighead and silver carp in established populations such as Kentucky, Barkley, and Cheatham Lakes."
First, a few carp will be caught and then tagged.
"Silver carp tend to stay in large groups so biologists could track the tagged fish to larger groups of silver carp," it said. "Biologists or commercial fishermen could then set nets in areas of known silver carp concentrations and remove them."
(This article appeared originally in B.A.S.S. Times.)