When silver carp invade a waterway, they’re hard to miss. The large, filter-feeding fish regularly grow more than three feet long and easily exceed 20 pounds. They loiter near the surface, where the plankton they feed on is most abundant. And, crucially, they’re easily startled. When boats go by, silver carp are known to catapult themselves multiple feet into the air, posing a projectile threat to both equipment, and people. Imagine dozens of 20+ pound fish jumping 10 feet out of the water in chaotic unison, causing a piscine maelstrom so thick it’s hard to navigate through it, let alone relax in its midst. Or, don’t imagine it– just watch a video of it.
Obviously, they disrupt recreational boating and other water-based activities. But from an ecological perspective, that’s far from the worst part. Silver carp grow so large, reproduce so numerously, and eat so much plankton that they outcompete native fish species, many of which are filter feeders, reliant on phyto- and zooplankton during their early life stages.
“They consume so much food and can exist in such great numbers that they can really reduce the amount of [resources] for resident species of fish,” says Peter Alsip, an ecologist with the NOAA Great Lakes Environmental Research Lab. Where they’ve invaded, research studies have noted changes in the plankton community and corresponding declines in native fish, he says. “They can have indirect effects on the whole ecosystem because [silver carp] are consuming phytoplankton and zooplankton, which are essentially the base of the food web,” adds Alsip.
Silver carp were initially introduced to the U.S. intentionally to help manage algae in aquaculture and wastewater facilities with their voracious appetites in the 1970s. Yet decades on, the fish have made their way into major U.S. watersheds and at least 20…
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