Invasion
Invasion Description
1st Records: CA/Tomales Bay (1987, McDonald and Koehn 1988); Muir Beach/CA/Pacific Ocean (1987, McDonald and Koehn 1988); San Rafael/CA/San Pablo Bay (1987, McDonald and Koehn 1988); Port San Luis/CA/Pacific Ocean (1987, MacDonald and Koehn 1988)
The actual invasion date of M. galloprovincialis is unknown. The invasion may have coincided, or followed with a heavy settlement of Mytilus 'edulis' in southern California in the 1940s (Carlton 1979). This species was first detected in molecular surveys, which began in 1985 (McDonald et al. 1991). This bioregion is a hybrid zone for Mytilus galloprovincialis and the native M. trossulus. Since molecular studies began in the late 1980s and early 1990s, both species and hybrids have coexisted but have varied in abundance with changes and gradients of salinity and temperature, with M. galloprovincialis prevailing at higher salinities and lower temperatures, while M. trossulus predominated at lower salinities, and at lower temperatures. These interactions were complex, so that M. trossulus outnumbered M. galloprovincialis at low salinity sites in San Francisco Bay, even though these sites had higher temperatures. In spite of these variations, the range of M. galloprovincialis has shifted northwards (Braby and Somero 2006). However, in 2005-2007, the frequency of M. galloprovinicalis and hybrids, north of 39°N declined from ~15-70% to about 5%. This change was attributed to lower temperatures, resulting from the Pacific Decadal Oscillation (Hilbish et al. 2010).
Geographic Extent
Shelter Cove/CA/Pacific Ocean (1995, Rawson et al. 1999); Mendocino/CA/Pacific Ocean (1995, Rawson et al. 1999); Gualala Point/CA/Pacific Ocean (1995, Rawson et al. 1999); Bodega Head/CA/Pacific Ocean (1995, Rawson et al. 1999); CA/Bodega Bay (1990, Sarver and Foltz 1993; 1995, Rawson et al. 1999; Braby and Somero 2006); CA/Tomales Bay (1987, McDonald and Koehn 1988; McDonald et al. 1991; 1990, Sarver and Foltz 1993; 1995, Suchanek et al. 1995, ongoing aquaculture, California Department of Fish and Game- Marine Region 2010); Miller Point/CA/Tomales Bay (Braby and Somero 2006); Muir Beach/CA/Pacific Ocean (1987, McDonald and Koehn 1988; McDonald et al. 1991); San Rafael/CA/San Pablo Bay (1987, McDonald and Koehn 1988; McDonald et al. 1991); North Beach/CA/San Francisco Bay (37 29N, 122 06W, 1992, Suchanek et al. 1997); Sausalito/CA/Golden Gate (1990, Sarver and Foltz 1993); Benicia/CA/Carquinez Straits (1990, Sarver and Foltz 1993); Berkeley/CA/San Francisco Bay (Sarver and Foltz 1993); Palo Alto Yacht Club/CA/South San Francisco bay (1992, Suchanek et al. 1997); CA/Half Moon Bay (1995, Rawson et al. 1997); CA/Elkhorn Slough (1992, Suchanek et al. 1997); Santa Cruz/CA/Monterey Bay (1995, Rawson et al. 1997); Moss Landing/CA/Monterey Bay (1990, Sarver and Foltz 1993); near Moss Landing/CA/Salinas River Mouth (1990, Sarver and Foltz 1993); Monterey Marina/CA/Monterey Bay (1995, Rawson et al. 1997); Garrapata State Park/CA/Pacfic Ocean (1995, Rawson et al. 1997); San Simeon State Park/CA/Pacific Ocean (1995, Rawson et al. 1997); CA/Morro Bay (1992, Suchanek et al. 1997); Hazard Beach/CA/Pacific Ocean (1990, Sarver and Foltz 1993); Port San Luis/CA/Pacfic Ocean (1987, MacDonald and Koehn 1988); Point San Luis/CA/Pacfic Ocean (1990, Sarver and Foltz 1993)
Vectors
| Level | Vector |
|---|---|
| Alternate | Hull Fouling |
| Alternate | Ballast Water |
Regional Impacts
| Ecological Impact | Competition | |
| In this bioregion, the native M. trossulus once was the sole mussel species. Based on field (Bodega Marine Laboratory, open coast) and lab experiments, Mytilus galloprovincialis displaces M. trossulus (Bay Mussel) and M. californianus (Sea Mussel) through interference competition (limiting movement, outfiltering, and overgrowing) with the native mussels as well as simply outgrowing them (Shinen and Morgan 2009). Physiological observations indicate that M. galloprovincialis is better adapted metabolically to warmer temperatures than M. trossulus, while M. trossulus is favored by cooler temperatures (Braby and Somero 2006; Lockwood and Somero 2011a). Mytilus trossulus is better adapted to low salinities (Lockwood and Somero 2011a). Consequently, climatic cycles such as the Pacific Decadal Oscillation and El Nino can cause cyclic fluctuations in the range, abundance, and hybridization of the two species (Braby and Somero 2006; Hilbish et al. 2010; Lockwood and Somero 2011a b). | ||
| Ecological Impact | Hybridization | |
| This species was first detected in molecular surveys which began in 1985 (McDonald et al. 1991). Central California is a hybrid zone for Mytilus galloprovincialis and M. trossulus. Since molecular studies began in the late 1980s and early 1990s, both species and their hybrids have coexisted but have varied in abundance with cyclic changes and gradients of salinity and temperature, with M. galloprovincialis prevailing at higher salinities and higher temperatures, while M. trossulus predominated at lower salinities, and at lower temperatures (Braby and Somero 2006). The fact that most detected hybrids are first-generation (F1) suggests little genetic exchange between populations and possible genetic incompatibility (Rawson et al. 1999). In earlier surveys, the hybrid zone extended north of Cape Mendocino (McDonald et al. 1991; Sarver and Foltz 1993; Rawson et al. 1999). In 2005-2007, the frequency of M. galloprovinicalis and hybrids, north of 39°N declined from ~15-70% to about 5%. This change was attributed to lower temperatures, resulting from the Pacific Decadal Oscillation (Hilbish et al. 2010). | ||
| Economic Impact | Fisheries | |
| Mussel aquaculture has been conducted in Tomales Bay (Conte 1992; California Department of Fish and Game 2010). Websites indicate that these operations continue (http://tomalesbayoysters.com/). | ||