Invasion of the Killer Carp: $7B Fishing Industry at Risk as Asian Carp Move Nearer to the Great Lakes
Asian carp have broken new water.
Eggs produced by the invasive freshwater fish were discovered near Lynxville, Wis., 250 miles upstream from previously identified spawning grounds in the Mississippi River, the United States Geological Survey reported last week.
“Very few Asian carp have turned up in that zone, so it was a real surprise to us to find the fish reproducing up there in the Upper Mississippi,” said Duane Chapman, a fishery biologist at USGS. “As these Asian carp move up [north], we are going to see more direct impacts on important fisheries.”
If the invaders reach the Great Lakes, they will likely devastate the region’s $7 billion fishing industry. In American rivers where Asian carp already flourish, they out-compete native fish species for food and habitat, creating a stranglehold on the local ecosystem. Scientists attribute the decline of yellow perch, walleye, and gizzard shad, a key prey fish, to skyrocketing Asian carp populations.
Aquaculture farmers originally imported the fish from Asia in the 1970s for use as natural, eco-friendly pond cleaners. But the carp soon escaped their enclosures and have been claiming new territory ever since. According to some estimates, Asian carp make up as much as 97 percent of the fish biomass in parts of the Mississippi River basin.
Voracious eaters, Asian carp consume as much as 10 percent of their body weight each day in plankton, growing up to four feet long and weighing up to 100 pounds. They also tend to leap into the air when frightened by the sound of approaching boats, which has led to serious injuries for fishermen and boaters, including broken bones and even fatalities.
Biologists at USGS have noticed that an important element of the Asian carp’s life cycle—the stage between the egg and the young three-inch fish—is the Achilles' heel of its development. “Either the eggs die or the larvae die or get eaten,” said Chapman. “Something happens between the very early life stages and the adult fish.”
Figuring out why Asian carp larvae are susceptible could be a key to reining in the population. Chapman and his team are examining what predators might be favoring Asian carp eggs, with an eye toward raising the numbers of those predators to keep the carp numbers down.
Other USGS research is trying to pinpoint the habitats in which Asian carp thrive in order to minimize ideal growing conditions. For example, they can withstand aquatic environments with low-dissolved oxygen concentrations, allowing them to swim to areas that predators can’t tolerate.
Then there’s the knife-and-fork approach. While Americans are not yet crazy for carp, some enterprising chefs are exploring recipes that bring out the Asian carp’s singular flavor, hoping to hook more seafood lovers. More than 1.5 million pounds of Asian carp were harvested from the Mississippi River last year alone.
But until McDonald’s or another large-scale food distributor creates Invasive McNuggets, the number of carp removed from the ecosystem by humans will likely not make a dent big enough to contain them. What’s worse, if consumer demand for Asian carp suddenly took off, suppliers might be tempted to move carp to other locations or take steps to increase the population.
Still, biologists are optimistic that the new research will identify solutions to the growing problem. “Asian carp aren’t magical,” Chapman said. “We can manage Asian carp, but we have to know how. What we’re working on now is the techniques.”