There are six species of Asian carp in United States waters, but it’s four in particular—Bighead Carp, Black Carp, Grass Carp and Silver Carp—that worry scientists and policymakers. These fish are found in the Mississippi River drainage from Louisiana to Minnesota, as far west as South Dakota, and as far east as Ohio. Several states, including Illinois, have long struggled with these aggressive invaders that wreak havoc on waterways with their voracious appetites, high reproductive rates and lack of natural predators.
Joe Parkos, director of Kaskaskia, Ridge Lake, and Sam Parr Biological Stations, and research biologist Steve Butler at the Illinois Natural History Survey (INHS) are working to change that. Thanks to funding from the Illinois Department of Natural Resources (IDNR), Parkos and Butler are assessing the success of methods aimed at scaling back the intruders as they inch toward the Great Lakes, in hopes of stabilizing the delicate ecosystems in Illinois’ streams and rivers.
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What’s working?
“At this point, multi-agency removal efforts have held the line and prevented the advancement of the leading edge of these invasions,” said Parkos, “Bighead Carp and Silver Carp have not gotten further than the Des Plaines and Joliet area.” Dams and electric barriers have blocked some upriver movement and commercial fishers contracted by the state remove thousands of tons of Asian carp from Illinois waterways. This removal has reduced their numbers upstream of the Starved Rock Lock and Dam, subsequently lowering the burden on the electric barriers that guard the entry to Lake Michigan.
But the Asian carp problem is a complex one because simply harvesting fish only provides a temporary and localized solution to a large-scale problem. Asian carp reproduce in such high numbers that they can easily replenish their populations with a single successful spawning season. Identifying when and where Asian carp spawn is, therefore, an important component for developing an integrated management strategy.
INHS is monitoring for Asian carp reproduction throughout the Illinois River. However, traditional methods for monitoring Asian carp reproduction are extremely time consuming. To speed up this process, Parkos and Butler are working with U.S. Geological Survey (USGS) colleagues and Mark Davis of INHS to develop genetic screening tools to detect Asian carp eggs and larvae using quantitative polymerase chain reaction, better known as quantitative PCR, or qPCR. Quantitative PCR is a technique that monitors the amplification of a targeted DNA molecule (in this case, for bigheaded carp) in real time, allowing for a measurement of the amount of DNA in the amplified sample. This approach will provide researchers with a timely and cost-effective solution to assess Asian carp spawning and allow them to provide this information to managers and policymakers in days instead of weeks to months.
Other monitoring tools include using reverse-time egg transport analysis for predicting Asian carp spawning grounds in the Illinois River. Using an algorithm that reverses the streamflow dynamics that move Asian carp eggs downstream, researchers can predict the spawning location where drifting eggs originate from in the river. INHS scientists collaborated with colleagues at the University at Buffalo, University of Illinois, and USGS to model the transport of Asian carp eggs through the Illinois River. Using this technology, INHS researchers can gain a better understanding of reproductive success and spawning locations, which are critical to identifying a reproductive front and developing control efforts. In a case study from 2015, researchers were able to identify tailwater sections below the Locks and Dams on the Illinois River as preferred spawning locations for Asian carp, and the furthest upstream spawning location detected was in the upper Marseilles navigation pool, only 25 miles downstream of the electric barrier.
In addition to monitoring the sprawl of Asian carp, Butler and Parkos are working around the clock to identify, manage, and predict the ecological impacts of Asian carp on various native fish species, and on entire food webs.
“Although some effects are known, and we can hypothesize about other potential impacts, it's important that we explicitly identify how Asian carp affect native fish and other aquatic biota so that we can accurately communicate the risk that these invasive species pose to North American river systems,” Butler said.
Parkos and Butler are continuing to focus their research toward the question of whether removing Asian carp from the water can mitigate the damage these fish have inflicted upon aquatic ecosystems and if these ecosystems will subsequently replenish.
“It's well established that Asian carp have strong effects on plankton communities, but we're still working to better understand all the cascading effects that these fish might have on other components of aquatic systems,” Butler said.
Other ongoing research examines what factors possibly influence Asian carp reproduction and further investigating their foraging habits. “This work will help managers better monitor these fish, and therefore make more informed decisions about controlling their populations,” Butler said.
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What’s not working?
Following a 2017 lawsuit against the Fish and Wildlife Service (FWS) by the United States Association of Reptile Keepers (USARK), the United States Court of Appeals ruled that the FWS does not have the authority to prohibit interstate transport of injurious wildlife. Before the ruling, the FWS could actively monitor interstate transport of fish under the Lacey Act of 1900, a conservation law that prohibits trade in wildlife, fish, and plants that have been illegally taken, possessed, transported, or sold.
“This new regulatory environment allows Asian carp to be transported through some regions of the country without restrictions, which creates the risk for further introductions into new watersheds,” said Butler. “Because carp don’t recognize state boundaries, an introduction into one state could spread to surrounding states through shared waterways.”
In 2009, Michigan (joined by New York, Minnesota, Ohio, Wisconsin, and the Canadian province of Ontario) filed a lawsuit against Illinois, asking the U.S. Supreme Court to close the O'Brien Lock and Dam in the Calumet-Sag Channel and the Chicago Controlling Works in the Illinois River in an attempt to seal Illinois waterways from Lake Michigan. The Supreme Court rejected the states’ appeal.
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Where did they come from?
Asian carp were brought to the United States in the 1970s to help fish farmers control algae in their ponds and began showing up in Illinois waterways in the mid-1990s. Their numbers exploded in the early 2000s shortly after being detected in Illinois rivers by IDNR and INHS monitoring programs. Monitoring the expansion of Asian carp has been a collaborative effort involving U.S Fish and Wildlife Service, U.S. Geological Survey, INHS, U.S. Army Corps of Engineers, Illinois DNR, Missouri, Wisconsin, and Canada, to name a few.
“What we are facing is these fish heading toward Lake Michigan, and maybe they wouldn’t thrive in the colder water of that environment, but if they become established, they could spread into tributary rivers throughout the lake’s basin. These species have harmful effects on native aquatic species and human commercial and recreational use of waterways. We should not take the risk of letting these species into the Great Lakes, because once a species becomes established and abundant, they are here and it is too late,” said Parkos. “In habitats where they are already established, we hope they will undergo a natural decline to a low stable abundance, but the fear is that they will continue to be hyper-abundant and dramatically change ecosystem dynamics.”