Out West, resource manages, anglers, and millions of others are understandably concerned as the weather heats up and boating season begins.
They’re worried because this also is prime time for reproduction by zebra and quagga mussels, and people can transport microscopic mussel babies without even knowing that they are doing it.
Lake Mead especially is a focal point of concern, both because of its popularity and because of its exploding quagga mussel population. In the five years since the exotic shellfish were discovered there, their numbers have increased tenfold.
According to the Las Vegas Review-Journal, a researcher estimates that more than 1.5 trillion adult quaggas now live in the Colorado River reservoir, along with 320 trillion mussel babies, also known as veligers.
That's 80 to 160 quaggas for every gallon of water in the nation's largest man-made lake. If mussels were dollars, there would be enough of them to pay off the national debt 20 times over, with a few trillion bucks to spare, according to the newspaper.
"They are everywhere in the lake," says David Wong, a researcher with the University of Nevada-Las Vegas and one of the nation's leading experts on the aquatic invader. "Almost every single rock has some mussels on it."
Wong also cautions that the veligers can survive in the tiniest puddles of water for as many as 27 days, and eventually be introduced to other waters via life jackets, waders, swimsuits, and even the bumper of a car that is backed into the lake to launch a boat.
Experts recommend draining all water from bilges and livewells, as well as cleaning gear with hot water and then leaving it out to dry for at least five days in the summer heat.
The key, Wong says: "Don't bring Lake Mead water home or to another lake, river or stream."
That same advice applies to those who visit any waterways where zebra and quagga mussels have become established.