Hi Dennis, I enjoyed your post about the clams that you found near Beverly
as well as the birding in E. WA. They are indeed Corbicula fluminea, an
invasive species. However they are not a recent introduction. They were
first identified in the U.S. in 1938, near Knappton in Pacific County, near
the mouth of the Columbia River. They have now spread up the Columbia and
Snake Rivers and to 38 of the 50 states. I have found them at Fisher island
[Cowlitz Co.] and Hood Park [Walla Walla Co.]. The scaups and other diving
ducks love to eat them so they may help increase numbers of ducks present.
I first found the clam in 2006 at Capitol Lake in Olympia after finding
shells discarding by diving ducks that had been eating them. These clams
are also present in Lake Washington. Thanks for the post. Good birding [and
shelling too], Bert Bartleson, Olympia