The invasive Asian clam is more common in the lower Columbia River than its native habitat of southeast Asia, according to a study of the clam's abundance in the river. The findings don't bode well for potential future invasions by the even more destructive quagga and zebra mussels. So far, the Columbia is one of the only major U.S. rivers to remain free of these notorious ecology-destroying, equipment-clogging bivalves.

 

For this study, published in journal International Review of Hydrobiology, the researchers sampled 27 sites along 481 kilometers (about 299 miles) of the river, stretching from the ocean to Richland, Washington. They found Asian clams were able to live at a variety of temperatures, water quality and substrates, such as silt, sand or rock. The team did find greater abundance of Asian clams below the Bonneville Dam than above it, and their greatest concentration, about 430 individual clams per meter, was found at the Sandy River confluence in Gresham, Oregon. The clams tended to be more prevalent in warmer waters and where slope of the bank or stream bed was less steep or more sandy, but few habitats were entirely devoid of Asian clams.