Daniel showed the pet store manager how to kill the freshwater interloper by dunking it in super-salty water, and they removed the moss balls from the shelves. Still, by March 8, the USGS reported mussel sightings in moss balls in Alaska, California, Colorado, Florida, Georgia, Iowa, Massachusetts, Michigan, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, Tennessee, Vermont, Virginia, Wisconsin, Washington, and Wyoming—with more states added since. Officials are investigating what Daniel refers to as the “chain of custody,” trying to determine whether the moss balls all came from a single producer, likely a wholesaler based in Ukraine, or from several sources. Meanwhile, with the US Fish and Wildlife Service and other partners, the USGS issued guidance for going ham on the moss balls to quash the new invasion—that’s where all the bleaching, boiling, freezing, and other pummeling comes in. Afterwards, the brutalized ball should end up in the trash, in a sealed bag.
Introductions from home aquaria aren’t the most common vector for species entering waterways such as the Great Lakes, but “they do happen,” says Christine Mayer, an aquatic ecologist at the University of Toledo. “Especially with fish—people don’t want to kill them. People don’t feel so bad about putting a plant in the compost, but they’re not sure they know how to humanely euthanize a fish.” Mayer says that ecologists sampling in the Great Lakes will sometimes come across a goldfish, either freed from a fishbowl or descended from others gone feral.
A preemptive strike is the best way to keep zebra mussel populations small, because established communities are incredibly difficult to eradicate. “Everyone who works with invasive species says prevention is better than cure,” Mayer says. “Keeping things out is cheaper, easier, and better than trying to kill them once they’re there.”
Introductions from large ships aren’t such a major issue anymore, because there are now procedures for how, where, and when ballast water can be dumped, says Eva Enders, a research scientist at Fisheries and Oceans Canada who has studied the mussels’ muscling through Lake Winnipeg, in Manitoba. Now, Enders says, “the risk that remains is inland—the transport by small leisure or recreational boats from lake to lake, river to river.” To aid in prevention, ecologists, naturalists, and others around the Great Lakes region have encouraged boaters to inspect their hulls and motors and thoroughly drain and dry water-holding compartments between outings.
It’s hard to picture a future in which waterways that are suffused with the mussels are ever fully free of them. “The Great Lakes are kinda … they’re already a thing,” Mayer says. That’s not the case everywhere, though, and more recent efforts have focused on stifling invasive zebra mussels in the western US, where they haven’t yet claimed as much turf. Groups such as the Invasive Mussel Collaborative, which works in partnership with the Great Lakes Commission, USGS, National Oceanic and Atmospheric Administration, and others, share tactics for snuffing out small populations. In New York’s Lake George, for example, a team successfully evicted a fledgling mussel population by quarantining the entire lake and dispatching divers to remove them manually.
Other strategies include pumping carbon dioxide into the water column, which suffocates the mussels inside it, and laying tarp-like benthic mats on mussel-studded bottoms, barricading the creatures from oxygen, light, and food. Several states have “decontamination stations,” where boats are inspected and cleaned, Weibert says. In Alberta, Canada, mussel-sniffing dogs are trotted out at highway checkpoints, Enders notes. USGS staff are currently adapting a test, initially developed for invasive carp, to suss out genetic evidence of zebra mussels in the water; Daniel thinks it could be up and running in the next several months.
But for now, ecologists really want your help preventing new spreads—and that involves unleashing some hellfire fury on moss balls.
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