Invasion
Invasion Description
1st Record: Astoria/OR/Youngs Bay, Columbia River estuary (1997, USGS Nonindigenous Aquatic Species Program 2007)
1st Nontidal Record: just downriver from Hagerman/ID/Lower Salmon Falls Dam impoundment, Snake River (1987, USGS Nonindigenous Aquatic Species Program 2007)
Geographic Extent
Hammond Harbor MarinaOR/Columbia River-Pacific Ocean (Hoy et al. 2012, 0.3-31 PSU); Astoria/OR/Youngs Bay, Columbia River estuary (1997, USGS Nonindigenous Aquatic Species Program 2007); Wallooskea/OR/Youngs River, Interior Port of Ilwaco/WA/Columbia River estuary (2002, Sytsma et al. 2004); OR/Cathlamet Bay (Bersine et al. 2008); WA/Baker Bay (2002, Bersine et al. 2008); WA/Grays Bay (Bersine et al. 2008); Kalama/WA/Columbia River estuary (2002, USGS Nonindigenous Aquatic Species Program 2007; Bersine et al. 2008); Knappa/OR/Columbia River estuary (2002, Sytsma et al. 2/004); WA/Lewis and Clark River (2002, Sytsma et al. 2004);
Vectors
| Level | Vector |
|---|---|
| Alternate | Ballast Water |
| Alternate | Fisheries Accidental (not Oyster) |
Regional Impacts
| Ecological Impact | Trophic Cascade | |
| In aquarium experiments with assemblages of Columbia River estuary species, high abundances of P. antipodarum led to increased consumption by fishes (Staghorn Sculpin- Leptocottus armatus; Threespine Stickleback- Gasterosteus aculeatus; Juvenile Starry Flounder Platicthys stellatus), and a shift away from the native isopod Gnorimosphaeroma insulare to the native amphipod Americorophium salmomis. This change in diet may have resulted from a change in foraging behavior in the fishes, in the presence of the snails (Brenneis et al. 2011). | ||
| Ecological Impact | Food/Prey | |
| Field surveys indicate that the dominant species of fishes in the Columbia River estuary (Staghorn Sculpin- Leptocottus armatus; Threespine Stickleback- Gasterosteus aculeatus; Juvenile Starry Flounder- Platicthys stellatus; Shiner Perch- Cymatogaster aggregata) rarely fed on P. antipodarum, despite the snail's high abundance in the benthos. However, field stomach contents and experimental observations indicate that the abundance of the snails had little effect on energy consumption by the fishes (Brenneis et al. 2011). | ||