Agencies work to reduce Asian carp in rivers

As Asian carp continue to dominate the Mississippi River, wildlife experts say eradicating the invasive species is impossible, but the growing population could be managed with help from the public.

Dave Knuth, fisheries management biologist at the Missouri Department of Conservation, said it and other agencies have been tracking fish in the Mississippi for more than 20 years. Since Asian carp were introduced in the 1970s as a biological control in commercial aquaculture, he said the fish population has grown dramatically.

"We're definitely seeing an increase in numbers and we don't know what number we'll end up reaching ..." he said. "The scary thing is they'll end up making 30 to 50 percent of the biomass, which is the total weight of fish out there. ... What that's doing is not only directly competing with ... native fish that depend on the same food source, it's also a competition for space. A body of water can only support so many fish."

The silver, black and bighead carp -- all from Asia -- represent a threat to native fish because they disrupt the food chain. They eat microorganisms such as plankton, which are a major food source for the small gizzard shad, which in turn is a major food source for larger game fish.

Some rivers, such as the Missouri River, are supporting the maximum number of Asian carp possible, but the Mississippi River has yet to hit that milestone, Knuth said.

Fisherman from the Illinois River near Pearl and Pleasant Hill, Ill., were the first to unload their thousands of pounds of fish, mostly Asian carp, Wednesday April 30, 2014, at the American Heartland Fish Products factory on Illinois Route 3 in Grafton, Ill. The first load of fish totaled nearly 4,000 pounds. The plant began test runs with fish Wednesday and will play their part in reducing the number of the invasive Asian carp that are so plentiful on the Illinois River. (AP Photo/The Telegraph, John Badman)

Bighead and silver carp are reported to comprise more than 90 percent of the biomass in parts of the Illinois River, said Dave Wethington, program manager for the U.S. Army Corps of Engineers Great Lakes and Mississippi River Interbasin Study.

Because the Asian carp has no natural predator or check, it's difficult to keep its population at a reasonable level. The carps' fast growth and high reproduction rate also exacerbate the problem; Knuth said the carp can produce up to 200,000 eggs per year.

The invasive species can be found all along the Mississippi and any body of water connected to it, he said. State and federal agencies have been working to keep the fish out of other large bodies of water such as the Great Lakes. The corps' most recent study, which addresses the need to reduce the risk of invasive species transfers between the two basins, presented options such as electric barriers and other technologies to help keep species such as the Asian carp at bay. Adult populations of Asian carp are about 55 miles from Lake Michigan and have not moved upstream for several years, Wethington said.

Locally, Knuth said preventing Asian carp from moving to other areas depends on proper public education. The easiest and most common way the fish are introduced to new bodies of water is through live bait dumping. While it's illegal to transport the species as live bait, it often happens accidentally, since young Asian carp look similar to gizzard shad, a popular live bait fish.

For those who gather live bait in one area to fish in another body of water, Knuth said it's important either to dump the bait on the ground or return it to its original area. This practice could help keep the fish from lakes free of the invasive species.

"We've got them right below Wappapello Lake, right at the dam. So all it would take is someone with a bucket of bait from below the dam [to] take it up to the lake and you're going to totally change that fishery," Knuth said. "Not only that, but you're probably going to see the end of water skiing."

Silver carp are known to jump out of the water and into the air in reaction to boat motors and other noises. Knuth said getting hit with a 20- to 40-pound fish while out on the water would be "like getting hit with a bowling ball."

For areas already home to the invasive species, he said there have been some efforts to make use of the plentiful fish. In Illinois and Kentucky, plants process up to 200 million pounds of fish per year to make omega-3 fish oil and dog food. Some of the Asian carp is flash frozen and shipped to China, where it's a popular food fish.

While these plants could help keep the Asian carp's rampant growth in check, Knuth said there's a reason more aren't popping up along the Mississippi River.

"Right now, commercial fishermen can go out and get 60 cents to a dollar per pound for catfish, buffalo, some of our meat fish that live in the river -- whereas Asian carp, they're only getting 10 to 15 cents per pound," he said. "So it's not worth their time, their gas and their effort to go out and target those fish right now, just because the processing plants are not very well established yet and there's not a huge market for this. ... The pain to flash freeze a fish and ship it over to China, it costs a lot to do that. There's nothing really local."

The Asian carp isn't a popular American food fish because it's bony, he said. But with the proper cleaning technique, the bones aren't difficult to remove and the meat is worth the effort. Knuth said the white, firm meat is often compared to scallop or halibut.

"The other really good thing about this fish is since it feeds on plankton and those microscopic organisms basically, and that's all it feeds on, it's very low in contaminants," he said. "There's no mercury. There's no cadmium or zinc or heavy metals in that tissue because it's not feeding on food sources that would have those contaminants in them. It's eating very high on the food chain."

Although eradication would be ideal, the corps similarly focuses on control and monitoring -- a more attainable goal. Whether it's promoting the Asian carp as a food fish or finding some other market, the state's conservation department is working with other agencies to find a way to reduce the population.

"Eradication will never happen; we'll never be able to get rid of all of them. But if we can provide some sort of check, some control that doesn't exist for this invasive species, that's the road we're going to go," Knuth said. "Our big promotion right now is the fish are very low in contaminants and they're very good to eat."

The department also hopes to create a new market for the fish through a sport that's gained in popularity recently: bow fishing. Silver carp swim close to the surface, Knuth said, making them prime targets for bow fishermen.

It's too soon to tell how effective these efforts at reducing the Asian carp's population will be, but Knuth said it's vital to the river's ecosystem that a method is found.

"It's just changing the whole dynamics of the river, basically, the way it used to function," he said. "It's a totally different species out there that's dominating the fish population."

srinehart@semissourian.com

388-3641

Pertinent address:

Cape Girardeau, Mo.

Wappapello, Mo.