Invasion
Invasion Description
1st Record: Sherman Island, near Antioch/CA/Sacramento-San Joaquin Delta- (1993, Modlin and Orsi 1997);
Geographic Extent
Sherman Island, near Antioch/CA/Sacramento-San Joaquin Delta- (1993, Modlin and Orsi 1997); CA/Sacramento-San Joaquin Delta-Suisun Bay (1993, Modlin and Orsi 1997); China Camp marsh/CA/San Pablo Bay (5/2002, Dean et al. 2005, one collection)
Vectors
| Level | Vector |
|---|---|
| Probable | Ballast Water |
Regional Impacts
| Ecological Impact | Competition | |
| By 1995, H. longirostris became the predominant mysid in the Delta, largely replacing the native Neomysis mercedis (Nobriga and Feyrer 2008). | ||
| Ecological Impact | Food/Prey | |
| Hyperacanthomysis longirostris is smaller than the native Neomysis mercedis, which had been a major food item for juvenile Striped Bass Morone saxatilis, a major introduced sport fish in the San Francisco estuary. It also maintains smaller population densities, probably due to the reorganization of the estuaries foodweb by massive populations of the filter-feeding Asian Brackish-Water Clam Corbula amurensis (Feyrer et al. 2003; Nobriga and Feyrer 2008). Feyrer et al. (2003) found that following the clam and exotic mysid invasion, the percentage of mysids in the diet dropped drastically for Striped Bass (spring 90- fall 80% to 40%, post-clam, exotic mysids), Starry Flounder (Platichthys flesus, native) (70-40% to near 0), and Yellowfin Goby (Acanthomysis flavimanus, introduced) (50-20% to 5%). For Striped Bass, the decline of the native mysid N. mercedis and its relacement by the smaller H. longirostris resulted in the fish starting mysid feeding at a smaller size and shifting to piscivory at a smaller size (Feyrer et al. 2003). The decline of the native mysid, and its replacement by smaller numbers of a smaller species may be a major factor in the decline of Striped Bass populations in the estuary (Nobriga and Feyrer 2008) | ||