Invasion
Invasion Description
1st Record: WA/Willapa Bay (1928, Established, 'sporadic spawning', since 1930, 'occasional large sets', (Carlton 1979; Chew 1979; settlement outside culture areas, Cohen et al. 2001)
Geographic Extent
Bahobohosh Point/WA/Pacific Ocean (2001, de Rivera et al. 2005); Wedding Rocks/WA/Pacific Ocean (2001, de Rivera et al. 2005); Norwegian Point Rock Shelf/WA/Pacific Ocean (2002); WA/Grays Harbor (1930, Carlton 1979; Feldman 2000); WA/Willapa Bay (1928, Established, 'sporadic spawning', since 1930, 'occasional large sets', Carlton 1979; Chew 1979; settlement outside culture areas, Cohen et al. 2001; established 2000-2020, Kornbluth et al. 2022); OR/Tillamook Bay (1940, cultured to the present, Carlton 1979, Oregon Department of Fish and Wildlife 2011 http://www.dfw.state.or.us/mrp/shellfish/bayclams/about_oysters.asp); OR/Netarts Bay (1948, cultured from 1948 to the present, Carlton 1979, Oregon Department of Fish and Wildlife 2011 http://www.dfw.state.or.us/mrp/shellfish/bayclams/about_oysters.asp); OR/Yaquina Bay (1st planting 1906, cultured to present, Carlton 1979, Oregon Department of Fish and Wildlife 2011 http://www.dfw.state.or.us/mrp/shellfish/bayclams/about_oysters.asp); OR/Umpqua Bay (cultured 1948+, Woelke 1955, cited by Carlton 1979, culture continues in Winchester Bay); OR/Umpqua Bay (cultured 1948+, Woelke 1955, cited by Carlton 1979, culture continues in Winchester Bay (a subestuary) Oregon Department of State Lands 2011, http://www.oregon.gov/DSL/SSNERR/docs/EFS/EFS34aquaculture.pdf?ga=t); OR/Coos Bay (1948, cultured from 1948 to the present, Carlton 1979, Oregon Department of Fish and Wildlife 2011 http://www.dfw.state.or.us/mrp/shellfish/bayclams/about_oysters.asp; estblished, Kornbluth et al. 202); CA/Humboldt Bay (cultured, from 1953 to present, Sporadic reproduction seen, Span 1979; Carlton 1979; Boyd et al. 2002; Conte 2007; Kornbluth et al. 2022)
Vectors
| Level | Vector |
|---|---|
| Probable | Oyster Intentional |
Regional Impacts
| Economic Impact | Fisheries | |
| Willapa Bay and Grays Harbor are major oyster-growing areas, producing more than 10% of the US oyster crop, through intensively managed culture (Feldman et al. 2000; Ruesink et al. 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). In Oregon, aquaculture of M. gigas began in 1906 in Yaquina Bay, and 1940-1948 in Netarts, Tillamook, Winchester, and Coos Bays (Carlton 1979), and continues to the present day (Oregon Department of Fish and Wildlife 2011, http://www.dfw.state.or.us/mrp/shellfish/bayclams/about_oysters.asp; Oregon Department of State Lands 2011, http://www.oregon.gov/DSL/SSNERR/docs/EFS/EFS34aquaculture.pdf?ga=t). | ||
| 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 interitdal zone has created large areas of hard, stuctured habitat, which supports greatly increased densities of epibenthic invertebrates, incluiding 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 negetive effect on the native oyster by attracting large numbers of settling larvae of O. lurida, in 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 (Ruesink et al. 2006). This is an underestimate, since it is based on harvested biomass, and excludes feral populations of M. gigas. | ||
| 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 the 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 on the Washington-Oregon-northern California Coast, including Pteropurpura (=Ocinebrellus) inornata (Japanese Oyster Drill) in Willapa Bay, the parasitic copepod Mytilicola orientalis (widespread), the bryozoan Schizoporella japonica, and the tunicates Botrylloides violaceus, Didemnum vexillum and Styela clava (Carlton 1979; Cohen and Carlton 1995; Boyd et al. 2002; Wonham and Carlton 2005). | ||