Once silver carp invade your waterways, they are hard to miss. Large filter-feeding fish regularly grows more than It is 3 feet long and easily weighs over 20 pounds. They roam near the surface, where the plankton they feed on is most abundant. And importantly, they are quick to surprise. Silver carp are known to jump several feet into the air when boats pass, posing a projectile threat to both equipment and people. Dozens of fish over 20 pounds jump from 10 feet above the water in chaotic unison, and the maelstrom of fish is so thick that it is difficult to wade through it, let alone relax in its midst. Imagine having difficulty moving on. Or don’t imagine it. clock be video of it.
Obviously, they interfere with recreational boating and other water activities. But from an environmental protection point of view, it’s not the worst situation. Because goldfish grow so large, reproduce so prolifically, and eat so much plankton, they are highly dependent on native fish species (many of which are filter feeders and feed on phytoplankton and zooplankton in their early life stages). (dependent on).
“They can consume so much food and exist in such large numbers that they can actually reduce the amount of food. [resources] “For native fish species.” Peter Alsipan ecologist at the NOAA Great Lakes Environmental Laboratory. Where they invade, research studies have noted changes in plankton communities and associated declines in native fish, he says. “They can have indirect effects on the entire ecosystem. [silver carp] They’re essentially consuming the phytoplankton and zooplankton that are the base of the food web,” Alsip added.
silver carp first introduced Their voracious appetite brought them to the United States on purpose in the 1970s to help manage algae in aquaculture and wastewater facilities. But decades later, the fish has invaded major U.S. watersheds and at least 20 states. According to the U.S. Fish and Wildlife Service, they are found in the Mississippi, Missouri, and Ohio rivers and their tributaries. For many years, they have been trying to enter the Great Lakes, the largest freshwater system on Earth. If this fish were to enter the lake, it would be poised to spread to all adjacent river systems, expanding its occupation to new heights.
But somehow, something holds them back. Despite traveling far up the Illinois River, silver carp have yet to establish a population in Lake Michigan. that the “cutting edge” or frontier of their progress has been stagnant south of Chicago for about a decade. cory saskya fisheries biologist and professor of natural resources and environmental sciences at the University of Illinois at Urbana-Champaign. There are several theories as to why.
Dams and sluices may impede its progress (although research shows “Fish can overcome such physical barriers,” Sasky said. Aggressive culling efforts along the Illinois River may be successful in maintaining carp populations by eliminating the competition that motivates them to find new territory, Alsip suggests. The Illinois River becomes increasingly channelized as it approaches Chicago, capping its natural banks with concrete walls, potentially acting as a deterrent, Suskey said. There is an electric barrier in Joliet along the river, intentionally intended to deter invasive species, Alsip points out. at least one person recently (I crossed the electric fish fence) There’s also a less obvious, latent obstacle: pollution.
One long-standing hypothesis posits that Illinois River silver carp primarily remain well south of Chicago because water quality deteriorates closer to the city. Recent studies, including newly published experimental evidence by Suski et al., support this theory. Silver carp show signs of stress, including physical and behavioral changes, when exposed to river water collected from the Chicago area. Research published Oct. 25 in the journal scientific report.
The findings show that in this one example, humans mistakenly pitted two environmental disasters against each other. If waterways were sufficiently purified (the water quality of the Illinois River would also be have was done Improved over decades), silver carp are more likely to enter the Great Lakes. Otherwise, everything else that lives in and along the river will continue to suffer from pollution.
“We’re not promoting pollution to combat carp,” Saski said. But if water quality continues to improve dramatically, the carp could start moving, he explains. “I wish we could get ahead of it and at least be prepared for it.” Perhaps more awareness of water quality challenges will allow wildlife managers to step up fish removal efforts or make them more targeted. You may be ready to invest in targeted, less toxic, intentional barriers.
Previous research from Suski’s lab suggests that polluted water in suburban Chicago may be deterring carp. 2019 survey The study showed that wild silver carp living near urban areas showed signs of their livers working too hard to filter out toxins, as well as genetic signatures of exposure to toxins. New research reinforces these findings and shows that there is a clear link between water sources and carp physiology, even in laboratory experiments.
In multiple experiments, the researchers compared the responses of juvenile goldfish to the responses of native golden shiners when exposed to water from the Illinois River in the Chicago area. Each study involved approximately 10 fish of each species, and water from the aquaculture facility where the fish were kept constituted the control condition.
Suski and his co-authors found that silver carp became much less active (i.e., froze) when exposed to urban waters. At the same time, your metabolism kicks into high gear, as measured by your breathing rate. “They’re moving less, but they’re expending more energy,” Sasky says. In contrast, the golden specimens showed no significant changes, indicating that the carp are particularly sensitive to any pollutants present in the water, he added.
Taken together, this “suggests that water quality factors may be a significant part of the equation,” says Alsip, who was not involved in the new study. “This is new evidence against this poor water quality theory.”
The study has some limitations. While not all experiments were successful, and a series of experiments using a two-choice shuttle box did not go as planned, this study demonstrated that carp actively avoid more polluted water. They couldn’t, Saski points out. Scientists have only tested the effects of short-term exposure, and long-term exposure may change the fish’s response. Furthermore, the sample size is limited and only juvenile fish were used in this study, which may lead to different responses in adults. Finally, the study did not specify what toxins or contaminants were involved. Further research is needed to determine exactly what is causing the carp’s stress.
And in reality, multiple factors are likely keeping silver carp out of the Great Lakes, Susky and Alsip say. Pollution is just one variable, and carp removal, electrical barriers, and habitat changes likely also play a role.
Still, this study illustrates how complex human impacts on ecosystems can be. “I would never say pollution is good,” Alsip says. “But it’s kind of interesting to see how one mess can help prevent or clean up another mess.”
