Potamopyrgus antipodarum
•Madison River, MT  2000
•Gardner River, WY   2000
•Yellowstone River, MT   2000
•Pahsimeroi River, ID   2000
•Buffalo River, ID   2000
•Green River, UT   2001
•Owens River, CA   2001
•Missouri River, MT  2002
•Colorado River, AZ   2002
•Garrison Lake, OR   2002
•Little Bear, Provo, Jordan, and Logan rivers, UT  2002
•Bighorn River, MT  2002
•Beaverhead River, MT  2002
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Another mollusks, this time an aquatic snail is making a big splash out west. After the initial find in the Grand Canyon in 2002, a subsequent survey found them throughout most of the Grand Canyon.  Although the snails were identified in California in 2001, older samples from as far back as 1997 where found to have them but had been misidentified initially as a native snail. Researchers at Montana State University seem to be finding this snail nearly everywhere.  They have reported densities as high as 750,000/m2.  Changes since the mudsnails arrival include a decrease in algae biomass and decrease in caddis flies and mayflies with an increase in amphipods in one measured site. There are native snails in the region that most likely will be impacted to some degree by the NZMS.