Invasion
Invasion Description
1st Record: WA/Willapa Bay (1928, Established, 'sporadic spawning', since 1930, 'occasional large sets', 'many substrates, large adult populations' 'Carlton 1979; settlement outside culture areas, Cohen et al. 2001)
Geographic Extent
WA/Willapa Bay (1928, Established, 'sporadic spawning', since 1930, 'occasional large sets', 'many substrates, large adult populations' Carlton 1979; settlement outside culture areas, Cohen et al. 2001)
Vectors
| Level | Vector |
|---|---|
| Probable | Oyster Intentional |
Regional Impacts
| Economic Impact | Fisheries | |
| Willapa Bay is a major oyster-growing area, producing 10% of the US oyster crop, through intensively managed culture (Ruesink et all. 2006). A negative impact of this aquaculture operation is the use of the pesticide carbaryl to kill the mud shrimps Neotrypaea californiensis and Upogebia pugettensis, which interfere with oyster culture by burrowing and suspending sediment. The pesticide also kills juvenile Dungeness Crabs (Metacarcinus magister), English sole (Parophrys vetulus), and other commerical and sport fishery species, as well as raising general environmental concerns (Feldman et al. 2000). | ||
| Ecological Impact | Habitat Change | |
| Intensive oyster production has greatly altered Willapa Bay. Most of the production takes place in the intertidal zone, which was formerly mudflat. The native Olympic Oyster, O. lurida, now rare, was primarily subtidal. Oyster growth in the intertidal zone has created large areas of hard, stuctured habitat, which supports greatly increased densities of epibenthic invertebrates, including mussels, scaleworms, and tube-dwelling amphipods (Ruesink et al. 2005; Ruesink et al. 2006; Hosack et al. 2006). However, the large accumulations of shell which M. gigas creates in the intertidal zone has a negative effect on the native oyster by attracting large numbers of settling larvae of O. lurida, to the interitdal zone, where their survival is poor, acting as a recuriment sink (Ruesink et al. 2005). | ||
| Ecological Impact | Herbivory | |
| The greatly increased oyster biomass has resulted in an increase in filtration rate of about 25%, from 0.8 to 1.3% of the bay's volume. This is an underestimate, since it is based on harvested biomass, and excludes feral populations of M. gigas. However, oyster-rearing habitat consitutes only a small portion of Willapa Bays area (Ferraro and Cole 2007). | ||
| Ecological Impact | Competition | |
| Competition between the introduced Pacific Oyster (Magallana gigas) and the native Olympia Oyster (Ostrea lurida) is expected to be minimal, since M. gigas tends to settle, and is cultivated in intertidal areas, while the native oyster tends to grow in lower intertidal and subtidal areas. However, where they do overlap, M. gigas grows much faster, and has a higher filtration rate (Ruesink et al. 2005). Competition for space occurs when M. gigas displaces native Eelgrass (Zostera marina), in culture operations (Wagner et al. 2012). | ||
| Ecological Impact | Parasite/Predator Vector | |
| Parasite-Predator vector- The introduction of M. gigas has been a possible/probable vector for a number of oyster foulers or predators in Willapa Bay, including Pteropurpura (=Ocinebrellus) inornata (Japanese Oyster Drill), the parasitic copepod Mytilicola orientalis (widespread), the bryozoan Schizoporella japonica, and the tunicate Botrylloides violaceus (Carlton 1979; Cohen et al. 2001). | ||