Biologists See Decline of Zebra Mussels in St. Croix River

Created: 03/29/2013 9:37 PM KSTP.com By: Scott Theisen

It appears zebra mussels are disappearing from key portions of the St. Croix River, and there's a chance the river could soon be nearly free of the invasive mussels - as long as they're not reintroduced.

Biologists once estimated the river was full of millions of zebra mussels from Stillwater down to Prescott. Now, they say that number is more like thousands. They check eight locations ever year and say the invasive species is definitely on the decline.

A couple of theories: One is a faster current during higher water levels in recent springs. The faster current can wash the offspring downstream. Another bit of evidence contributing is that common carp in the river have figured out that zebra mussels make a pretty good meal.

Biologists have checked out the belly contents of carp and found them filled with zebra mussels.

They caution the numbers could rise in the future under the right conditions, but they are encouraged by what they're seeing.