The Mystery of the Vanishing Mussels

What's driving America's freshwater mussels toward extinction?

- BY ROBERT KUNZIG

American streambeds were once paved with these beautiful burrowing creatures—300 species of them.

Some 10 percent are extinct already. Many more are endangered, including the Northern riffleshell (pale with fine green rays, at bottom) and the clubshell (with darker splotches, at middle).

THROUGH MY SWIM MASK, I could see what Wendell Haag's finger was pointing at two feet below me on the riverbed. But I couldn't immediately see that it was alive. It looked like a rock with some kind of grayish goo stuck to it. We were in the South Fork of the Kentucky River, and I was on my hands and knees with my face in the water and my backside in the air—an inelegant pose I had learned from mussel biologists such as Haag. Finally, after a long, dumb stare, I recognized the mussel. It was mostly buried, but it, too, had left its posterior exposed, and the shell was slightly agape. Draped around that dark slit were fleshy protrusions that flapped like pennants in the current. The mussel, called a pocketbook, was fishing for bass.

A bass, it seems, would mistake those protrusions for an edible minnow. It would snap at the lure, whereupon, instead of food, it would get a mouth blast of mussel larvae—thousands of bivalved vampires smaller than salt grains, some of which would immediately latch on to its gills and start feeding on its blood.