Friday August 21, 2026
TCD —
In some of America’s most familiar lakes, invasive crayfish now number in the millions, and their impact reaches far beyond the water’s edge.
Here’s what to know
Lake Tahoe offers one of the clearest examples. As Fox Weather reported, the lake’s invasive signal crayfish population is estimated to have climbed from roughly 56 million in the 1960s to about 240 million to 280 million today.
Tahoe is not alone. Fox Weather, citing WorldAtlas, said invasive crayfish have also appeared in places including Lake of the Woods, Crater Lake, Lake Mead, and Lake Michigan.
Different species are driving the problem in different places. Fox Weather reported that rusty crayfish, which are native to the Ohio River Basin, have spread widely through the Great Lakes region and compete with native crayfish for food and shelter. In Lake Tahoe, Fox Weather said signal crayfish were introduced in the late 1800s partly as food for stocked trout and for people to eat.
When they establish themselves outside their natural range, these crayfish can significantly disrupt ecosystems. According to Fox Weather, they eat aquatic plants, algae, and other organisms, changing food webs and removing vegetation that fish and other species depend on.