Invasion
Invasion Description
1st Record: Whidbey Island/WA/Penn Cove, Puget Sound (1994, 25% M. galloprovincialis, 10% hybrids, Suchanek et al. 1997). In this bioregion, local populations of Mytilus galloprovincialis have become locally established, especially near aquaculture areas and ports, in warmer and shallower inlets, hybridizing with the native M. trossulus is being cultivated in commercial aquaculture operations (Anderson 2002; Wonham 2005). In a recent study of Mytilus in Puget Sound, Elliott et al. (2008) found that pure M. galloprovincialis comprised 0-14% of mussels sampled, while hybrids were 0-37%. 'Frequencies of M. galloprovincialis and M. galloprovincialis x M. trossulus were higher in subtidal habitats, such as docks, than on intertidal rocks, walls or pilings. Within intertidal habitats, M. galloprovincialis and M. galloprovincialis x M. trossulus were more frequent than M. trossulus in the lower reaches of the intertidal. At slightly more than half the sites the frequency of the three genotypes accorded with random mating expectations, suggesting no consistent barriers to gene flow between species' (Elliott et al. 2008).
Geographic Extent
Whidbey Island/WA/Penn Cove, Puget Sound (1994, 25% M. g., 10% hybrids, Suchanek et al. 1997); Edmonds/WA/Puget Sound (1998, 19% M. galloprovincialis, Anderson 2002; Wonham 2005); Seahurst County Park/WA/Seattle (19% M. galloprovincialis, 1998, Anderson 2002; Wonham 2005); Silverdale/WA/Dyes Inlet (35% M. galloprovincialis, 1998, Anderson 2002; Wonham 2005); Shelton/WA/Hammersley Inlet, Puget Sound (33-43% M. galloprovincialis, 1997- 1998, Anderson 2002; Wonham 2005); Taylor Shellfish Rafts/WA/Totten Inlet (75-100% M. galloprovincialis, 1997- 1998, Anderson 2002; Wonham 2005)
Vectors
Level | Vector |
---|---|
Alternate | Ballast Water |
Alternate | Hull Fouling |
Alternate | Fisheries Intentional |
Alternate | Fisheries Accidental (not Oyster) |
Regional Impacts
Economic Impact | Fisheries | |
Extensive aquaculture of M. galloprovincialis is conducted in waters of British Columbia and Puget Sound (Anderson et al. 2002; Wonham 2004; Elliott et al. 2008; http://www.taylorshellfishfarms.com/ourStore-mussels-mediterranean). | ||
Ecological Impact | Hybridization | |
Locally high rates of hybridization (10-57% of sampled mussels) between Mytilus galloprovincialis and native M. trossulus have been found in locations in Puget Sound near marinas, ports, and shellfish farms (Anderson et al. 2002; Wonham 2004, Elliott et al. 2008). | ||
Ecological Impact | Competition | |
In Puget Sound, where M. trossulus was once the sole mussel species, the frequency of M. galloprovincialis is greatest in protected waters near areas of likely introduction, including marinas, shipping harbors, and aquaculture sites, but also shallow, warmer waters favorable to the growth of the introduced mussel. At 4 of about 60 sites in this bioregion, purebred M. galloprovincialis exceeded 25% of the mussels sampled (Wonham 2004). Elliott et al. (2008), sampling more selectively in Puget Sound, found 6 of 29 sites in which frequencies of M. galloprovincialis comprised more than 25% of the sampled mussels. In most sites in Puget Sound (Wonham 2004; Sheilds et al. 2010), the abundance of M. trossulus and its hybrid are so low that competitive impacts on M. trossulus are likely to be small. | ||