Nutria records for Washington:

East Side:
Ponds in SE Okanogan County
Along the Yakima River

West Side:

Wahkiakum Co. (prob the J.B. Hanson refuge)
SW Pacific County
Thurston County, west of Olympia
King County, 2 Township/Ranges, one probably from Lake Washington, one
from directly east
Grays Harbor County, along the Chehalis R.
Clark County, near Vancouver

Based on museum records and reliable sightings, they are along the
Columbia River and tributaries from the mouth to the Vancouver area and
up the Cowlitz River; along the Chehalis River and in the wetlands of
Thurston Co; and along the east side of the Puget Sound from Skagit to
King Co. They are confined to low-lying wetlands. We have no evidence
they occur in Whatcom or Pierce County, but they are spreading from
original colonies on the west side, so their presence would not be a
surprise. They do not appear to have spread from the original colonies
on the east side. Probably can't take the cold winters. They do much
better in warmer climates (Oregon's Willamette Valley, for example).

Any Tweeter with a reliable observation, preferably backed up with
photo or other evidence, from Whatcom County, Pierce County, or other
areas not mentioned, please feel free to contradict me.

Kelly Cassidy