Invasion
Invasion Description
1st Record: WA/Puget Sound (1902, Carlton 1979)
Geographic Extent
Ketchikan/AK/Inside Passage (1939, cultured, Carlton 1979); Brooks Peninsula, Vancouver Island/British Columbia/Pacific Ocean (2006, Gillespie et al. 2007; http://www.pices.int/publications/presentations/PICES_15/Ann15_S8/S8_Gillespie.pdf); British Columbia/Pendrell Sound (Quayle 1969); Vancouver Island/British Columbia/Barkley Sound (Ruesink 2007); Cortez Island/British Columbia/Georgia Straits (Kelly et al. 2008); Ladysmith, Vancouver Island/British Columbia/Georgia Strais (1912, natural spawning and settlement observed starting in 1926, Quayle 1969); Campbell River, Vancouver Island/British Columbia/Georgia Strait (2008, Choi et al. 2016); Vancouver Island/British Columbia/Mad Bay (Mach et al. 2017); mNanaimo/Vancouver Island/British Columbia/Georgia Strait (2008, Choi et al. 2016; Mach et al. 2017); Port Alberni, /Vancouver Harbour (2008, Choi et al. 2016); Vancouver Island/British Columbia/Alberni Inlet (2008, Choi et al. 2016); Vancouver/British Columbia/Natural settlement range- Sooke Harbour, Vancouver Island/British Columbia/Strait of Juan da Fuca to Quadra Island/British Columbia/Pendrell Sound (Quayle 1969); WA/Samish Bay (1905, Carlton 1979); Vancouver/British Columbia/Vancouver Harbour (2007-2009, Sylvester et al. 2011, in hull fouling); WA-BC/Boundary Bay (Dall 1926 cited by Carlton 1979; Quayle 1969); WA/Bellingham Bay (Dall 1926, cited by Carlton 1979); WA/Samish Bay (1905, Carlton 1979); WA/Padilla Bay (1932, de Rivera et al. 2005; Riggs 2011); WA/Puget Sound (1902, sporadic but successful reproduction and settlement, since 1934, Carlton 1979; Chew 1979); WA/Quilcene and Dabob Bay, Hood Canal (natural settlement, Chew 1979); Kamilche Point/WA/Totten Inlet (12:30-1:40 pm, 19 May 2000 47° 09' 07.253' N; 123° 01'06.195' W, Salinity 30 psu, Water temperature 15°C, on cobble beach, Cohen et al. 2001); WA/School Creek, Neah Bay (2001, de Rivera et al. 2005); Salinity 30 psu, Water temperature 15°C, on cobble beach; Cohen et al. 2001); WA/Hood Canal (Ruesink et al. 2005); WA/Quilcene and Dabob Bay, Hood Canal (natural settlement, Chew 1979); Belfair/WA/Hood Canal (1942, Valdez and Ruesink 2017); Puget Sound to Haida Gwai (2000-2020, widely establiushed, Kornbluth et al. 2020)
Vectors
Level | Vector |
---|---|
Probable | Oyster Intentional |
Regional Impacts
Ecological Impact | Habitat Change | |
On San Juan Island, Washington, intertidal M. gigas altered rocky shore communities by providing a light-colored substrate, decreasing substrate temperatures from a maximum of 56°C to 41°C. On average, oysters were 3.3°C cooler than surrounding rocks, and supported higher densities of limpets (4 species, Lottia strigatella, L. pelta, L. scutum, and L. digitalis). The most abundant limpet, L. strigatella was 3X more abundant on oysters than on surrounding rocks (Padilla 2010; Herbert et al. 2016). On rocky shores of British Columbia, where M. gigas primarily recruits in the upper intertidal zone, it increases the amount of habitat available for barnacle settlement (Bourne 1979, cited by Ruesink et al. 2005). Expanding cultivated and feral oyster beds of M. gigas have resulted in the reduction of Eelgrass (Zosters marina) beds on Cortes Island, in Georgia Strait, British Columbia. Eelgrass tends to disappear in areas seaward of the beds as well. These areas had reduced abundance of epifaunal invertebrates, but increased abundance of infauna (Kelly et al. 2008). The large accumulations of shells 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, in the intertdal zone, where their survival is poor, acting as a recruitment sink (Ruesink et al. 2005). | ||
Economic Impact | Fisheries | |
Magallana gigas has been reared in Puget Sound since 1902 in commercial operations (Carlton 1979). Commercial rearing includes bottom and raft culture in many of the Sound's inlets. However, pollution limits the extent of oyster culture. The fishery is largely dependent on hatcheries for reproduction, but some natural settlement occurs (Pauley et al. 1998; Cohen et al. 2001). In British Columbia, plantings began around 1912. Fisheries gradually expanded, especially with a mass spawning in 1958, but closures due to sewage pollution in the 1960s began to limit harvests in developed areas (Quayle 1969). Since the 1990s, most culture in British Columbia has primarily used raft culture on suspended ropes (BC Shellfish Grower's Association 2011; http://bcsga.ca/about/industry-encyclopedia/oysters/). In 2005, 7,638 tonnes of Pacific oysters were produced in British Columbia at a value of $8 million CAN (Canadian department of Fisheries and Oceans 2006; http://www.dfo-mpo.gc.ca/aquaculture/shellfish-mollusque/pac_oyster-huitre-eng.htm). | ||
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-British Columbia coast, including the seaweed Sargassum muticum, Pteropurpura (=Ocinebrellus) inornata (Japanese Oyster Drill), the flatworm Pseudostylochus ostreophagus, the parasitic copepod Mytilicola orientalis, the bryozoan Schizoporella japonica, and the tunicates Botrylloides violaceus, Didemnum vexillum, and Styela clava (Carlton 1979; Cohen et al. 1998; Cohen et al. 2002; Gillespie et al. 2007). | ||
Ecological Impact | Food/Prey | |
Juvenile M. gigas were a preferred food of the native Red Rock Crab (Cancer productus) in Puget Sound. Impacts on oyster populations were complicated by the fact that the crabs also fed on introduced predatory snails (Japanese and Atlantic Oyster Drills - Pteropurpurea inornata and Urosalpinx cinerea) (Grason and Miner 2012). | ||