Invasion History

First Non-native North American Tidal Record: 1874
First Non-native West Coast Tidal Record: 1874
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Mya arenaria's current native range is from subarctic Labrador, Canada to Cape Hatteras, North Carolina and sporadically to South Carolina (Abbott 1974; Gosner 1978), and in the Northwest Pacific, from the Yellow Sea, China to the Bering Sea (formerly as M. japonica; Zenekevich 1963; Golikov et al. 1976). However, based on the fossil record, this species originated in the North Pacific Ocean, possibly around Japan, during the Miocene period and soon colonized the Atlantic, reaching the European coast in the late Pliocene, but then dying out during most of its range in the Pleistocene. In Europe, the West Coast, and Alaska, it is absent for prehistoric human shell middens, disregarding some probable misidentifications (Carlton 1979).The surviving populations were on the East Coast of North America, and the East Coast of Asia (Vermeij 1989; Strasser 1999). Mya arenaria appears to be extinct in the Arctic Ocean, though determining its present distribution is complicated by occurrence of subfossil shells and other species of Mya and related genera (Bernard 1979, James T. Carlton, personal communication). Humans have re-introduced M. arenaria to much of its former range, and beyond. Vikings may have transported this clam to Scandinavia as early as the 13th century, and later shipping and food introductions may have moved it to most of the European coast, from the Barents Sea to the Iberian Peninsula (Petersen 1992; Strasser 1999). It is also established in a few estuaries along the Mediterranean Sea (Zenetos et al. 2003) and in the Black Sea (Gomiou et al. 2002). Softshell Clams were apparently introduced to the West Coast with plantings of Eastern Oysters (Crassostrea virginica) by 1874, and were soon deliberately transplanted as food as far north as Alaska (Carlton 1979; Powers 2006). Recent genetic studies support the recent (post-Pleistocene) introduction of Mya arenaria to Europe and the West Coast of North America (Cross et al. 2016; Lasota et al. 2016).

North American Invasion History:

Invasion History on the West Coast:

Mya arenaria was first reported on the West Coast in San Francisco Bay, California in 1874 (as M. hemphilli, Newcomb 1874, cited by Carlton 1979). It rapidly became abundant and widespread in the Bay, supporting fisheries, as early as the 1880s, and spreading as far upstream as Collinsville and Sherman Lake in the Delta (Cohen and Carlton 1995). Some early introductions to other estuaries, such as Coos Bay, Oregon (OR) (~1875, Dall 1897, cited by Carlton 1979) may have also occurred with oyster plantings, but M. arenaria rapidly became a desirable food item, and was planted deliberately. Early plantings occurred in the Siuslaw River, OR; Willapa Bay, Washington (WA) (in 1884, Stearns 1885, cited by Carlton 1979); Grays Harbor, WA (in 1888, Collins 1892, cited by Palacios et al. 2000); Puget Sound, WA (in 1888, introduced from Willapa Bay, Smith 1896, cited by Carlton 1979); the San Juan Islands (Smith 1896, cited by Carlton 1979); Vancouver Island, British Columbia (BC) (Departure Bay, Strait of Georgia; Taylor 1895, cited by Carlton 1979) and Clayoquot Sound, BC (Newcomb 1893, cited by Carlton 1979). In the 20th century, government and individual plantings occurred in many smaller estuaries from California to British Columbia. In California, populations were established from Bolinas Lagoon to Humboldt Bay and Crescent City by 1920-1922, mostly by state stocking (Weymouth 1920, Bonnot 1940, cited Carlton 1979). In Oregon and Washington, first reports of established populations in smaller estuaries are often later (1917-1950s, Edmondson 1922 and Marriage 1953, cited by Carlton 1979), but this may reflect less sampling in this region.

North of Vancouver Island, BC, M. arenaria was collected in the Queen Charlotte Islands in Massett Inlet in 1939 (Carl and Guiguet 1972; Carlton 1979); Prince Rupert in 1955 (Quayle 1960, cited by Carlton 1979); and Ketchikan, Alaska (AK) in 1946 (Hanna 1966; Carlton 1979). As mentioned above, the history of M. arenaria in Alaska is complicated by the presence of subfossil shells of this species and by the occurrence of similar related species. However, excluding some dubious records, it was present at Hooper Bay, AK (61.5°N) by 1924 (Baxter, personal communication, cited by Carlton 1979), and is common in Bristol Bay (58°N) and Norton Sound (64°N) (Bernard 1979), where it may have been present by 1905. Drift shells have been reported as far north as Kotzebue Sound (67ºN; Bernard 1979). Populations are well established south of the Aleutians, in Prince William Sound (Feder and Paul 1974, cited by Carlton 1979; Powers 2006), Kachemak Bay (1999, Hines and Ruiz 2001), and Kodiak Island (Nybakken 1969, cited by Carlton 1979). These northern occurrences probably represent individual, undocumented introductions, rather than long-range larval dispersal (Carlton 1979).

While M. arenaria has been an extremely successful invader, north of San Francisco Bay, it has not become established in several locations to the south. It was introduced to Santa Cruz, California in 1881 (Stearns 1881, cited by Carlton 1979), and to Morro Bay in 1915 (Heath 1916, cited by Carlton 1979), but both stockings failed. Mya arenaria stocked in Elkhorn Slough, before 1911, may have survived for a while, but by the 1990s, it was locally extinct (Wasson et al. 2001). In San Francisco Bay (Nichols and Thompson 1985; Poulton et al. 2004), Grays Harbor, WA (Palacios et al. 2000) and probably elsewhere, the Softshell Clam has undergone great fluctuations in abundance. In South San Francisco Bay, Nichols and Thompson (1985b) considered it to be an ‘irruptive species, appearing in abundance only one year during a 10-year period’. In the upper estuary of San Francisco Bay, from San Pablo to Suisun Bays, M. arenaria shows great spatial patchiness, as well as temporal variation. During dry periods, when salinities are high, it extends its range into Suisun Bay, but disappears from the upper reaches during flood periods (Nichols and Thompson 1985a). In Grays Harbor, soon after introduction in 1895-1897, a massive population explosion took place, followed by catastrophic mortality, leaving extensive 'death assemblages' of shells (Palacios et al. 2000). In general though, M. arenaria has been notably successful in establishing populations in San Francisco Bay and northward. It is capable of surviving and reproducing at lower salinities than native West Coast bivalves and is often the dominant (or only) marine bivalve in upper estuaries. It also tends to occur higher in the intertidal zone than native clams. Consequently, its invasion success may have been due to filling an unoccupied niche (Carlton 1979).

Invasion History Elsewhere in the World:

Mya arenaria is present in European fossil deposits from the Pliocene, but is believed to have become extinct in the late Pliocene, and is absent from prehistoric shell middens (Strasser 1999; Behrends et al. 2005). Several specimens in a Danish sand-dune deposit were estimated to date from1245-1295 CE, using C14 dating (Petersen et al. 1992) indicating a possible introduction by Vikings returning from North America. The Softshell Clam appeared very early in Western Europe, with a report from the Netherlands in 1765 (Baster 1765, cited by Wolff 2005). Generally, from Atlantic France to the western Baltic, the date of invasion is unknown, but is believed to be between 1500 and 1700 (Strasser 1999; Goulletquer et al. 2002). Charles Lyell, examining rocks near Stockholm, Sweden, in 1834, noted that this bivalve was abundant in the Baltic, but was absent in fossils, unlike other common Baltic mollusks (Lyell 1835, cited by Munthe 1894). By 1900, it was established along the west and south coasts of Sweden (Swedish Environmental Protection Agency 2006). It is now found in the inner Baltic, including the Gulfs of Bothnia, Riga, and Finland (Strasser 1999; Leppakoski and Olenin 2000; Swedish Environmental Protection Agency 2006; Zaiko et al. 2011; Olenin and Leppakoski 2012). Mya arenaria may have been originally transported with ballast stones or as food, and after its initial introduction, was probably extensively planted as seafood (Strasser 1999). European populations show a low level of genetic diversity, and a relatively homogenous population, indicating rapid gene flow and geographical expansion (Lasota et al. 2004).

In the farther reaches of Europe, Mya arenaria was found on the east coast of Iceland in 1958 (Oskarssen 1961, cited by Strasser 1999). It is established and is absent from the fossil record on the island (Simonarson and Leifsdottir 2009). It is reported to occur all along the coast of Norway, and is abundant in the Oslofjord (Winther and Gray 1985, cited by Strasser 1985), but specific records are not available for the western and northern coast (Strasser 1985). This clam is established in the White Sea (Maximovich and Guerassimova 2003), and to the Barents Sea, east of Svyaty Nos, on the Kola Peninsula (Zenkevich 1963; Galkin 1998). It was present in the White Sea, at least as early as 1963 (Zenkevich 1963; Russanova 1963, cited by Maximovich and Guerassimova 2003).

In the southern part of its European range, M. arenaria is believed to have become established in French waters by 1700 (Goulletquer et al. 2002). However, the first definite record on the Iberian Peninsula was in the Ria de Aveiro, Portugal in 1997 (Conde et al. 2012b). An early record (1988) from the Lima estuary was a misidentification, but M. arenaria is now established in the Lima (2010) and Tagus (2007) estuaries, Portugal (Conde et al. 2009; Conde 2012a). The distribution of the Softshell Clam in the Mediterranean Sea is spotty. Established populations were discovered in two French lagoons, Berre and Vaine in 1976 (Zenetos et al. 2003), and in the Gulf of Saronicos, Greece, in 1984 (Zenetos et al. 2005). Isolated collections were made in Sicily and the Adriatic (Zenetos et al. 2003; not established, Occhipinti-Ambrogi et al. 2011). Mya arenaria was found in the Black Sea in Romania in 1966, and became abundant enough to be regarded as a pest (Gomiou et al. 2002, Skolka and Preda 2010). It has spread to the Sea of Marmara (in 1996, Albayrak and Balcis 1996, cited by Albayrak 2011), and to the Sea of Azov (Savchuck 1980, cited by Zaitsev and Ozturk 2001).


Description

Mya arenaria is a bivalve with a thin, elongate, elliptical shell, gaping at the anterior and posterior ends even when closed. The pallial sinus is deep and somewhat V-shaped. The hinge is asymmetrical, with a long, tongue-shaped chondrophore in the left valve, and a heart-shaped pit on the right. The shell is chalky white with a thin dull-brown or yellowish periostracum. The typical maximum size is 75-100 mm, with a record length of 163 mm. It usually borrows in soft muddy to sandy sediments in shallow waters and intertidal mud flats (Abbott 1974; Gosner 1978; Coan et al. 2000; Coan and Valentich-Scott 2007). In large specimens, the siphon may extend for as much as 200 mm to reach the surface (Newell and Hidu 1986).


Taxonomy

Taxonomic Tree

Kingdom:   Animalia
Phylum:   Mollusca
Class:   Bivalvia
Subclass:   Heterodonta
Order:   Myoida
Superfamily:   Myoidea
Family:   Myidae
Genus:   Mya
Species:   arenaria

Synonyms

Mya acuta (Say, 1822)
Mya acuta mercenaria (Say, 1822)
Mya alba (Agassiz, 1839)
Mya arenaria corbuloides (Comfort, 1938)
Mya communis (Megerle von Mühlfeld, 1811)
Mya corpulenta (Conrad, 1845)
Mya declivis (Pennant, 1777)
Mya elongata (Locard, 1866)
Mya hemphilli (Newcomb, 1874)
Mya lata (J. Sowerby, 1815)
Mya oonogai (Makiyama, 1935)
Mya subovata (Woodward, 1833)
Mya subtruncata (Woodward, 1833)
Sphenia ovoidea (Carpenter, 1864)
Mya paternalis (Matsumoto, 1930)

Potentially Misidentified Species

Mya japonica
Mya japonica (Japanese Softshell Clam) has been found to be a genetically distinct species, occuring from the Yellow Sea, China, to the Bering Sea, Russia (Golikov et al. 1976; Bernard 1979; Zhang et al. 2018). Morphological differences are small, but M. japonica has a taller shell, with a more rounded posterior end, rougher submarginal wrinkles, and a more impressed pallial line. However, morphological variability is high. Genetic analysis and spermatozoon morphology indicates that the two species diverged 4.1-12.5 Myr ago (Zhang et al. 2018). Two specimens of M. japonica have been collected in British Columbia, the first record of this species in the Eastern Pacific (Zhang et al. 2018).

Mya truncata
Mya truncata is native to the Arctic Ocean. The extent of its range into the temperate Atlantic and Pacific has been obscured by its similarity to M. arenaria (Carlton 1979; Strasser 1999; Zhang et al. 2018). Genetic analysis suggests that it is a species complex (Zhang et al. 2018

Mya uzenensis
Mya uzenensis (Siberian Softshell Clam) is native to Alaska and northeast Russia (Zhang et al. 2018).

Ecology

General:

Mya arenaria is a large bivalve which inhabits gravelly to muddy bottoms, from the mid-intertidal to about 100 m depth, though they are rare below 9-10 m. In regions with large tidal ranges, they are most-abundant in intertidal mudflats (Gosner 1978; Newell and Hidu 1986). They require temperatures above 12-15°C for spawning, but do not tolerate temperatures above 28°C for prolonged periods (Newell and Hidu 1986). Mya arenaria is unusually tolerant of low salinities, and can be acclimated to feed at 3 PSU (Castagna and Chanley 1973). In estuaries such as Chesapeake Bay and brackish seas such as the Baltic, Softshell Clams can be abundant at salinities as low as 4-5 PSU, while at marine salinities (25-25 PSU), predation may reduce their abundance in subtidal waters (Newell and Hidu 1986; Carlton 1979). Sexes are usually separate, but there is a low incidence of hermaphroditism. Size appears more important than age in determining maturity. Maturity occurs at about 20 mm length, while market size is about 50 mm. Market size is reached in about 1.5 years in Connecticut, 3-6 years in Maine, 5 years in New Brunswick and the White Sea (Sadykhova 1979; Newell and Hidu 1986).

Mya arenaria usually spawns twice a year in spring and fall, mostly in the southern part of its range (Connecticut, Rhode Island, but also in Oslofjord, Norway and southern England), but once a year mostly further north (White Sea- Russia, Maine, New Brunswick, Ireland, Sweden, Wadden Sea, but also the Black Sea) Spawning usually occurs at 10-25ºC, but the temperature range is quite variable (Sadykhova 1979; Newell and Hidu 1986; Strasser 1999; Cross et al. 2012). Reported fecundity ranges from about 100,000 to 3 million eggs (Newell and Hidu 1986). The eggs and sperm are released through the exhaling siphon. Fertilized eggs develop into trochophore larvae within 9 hours and a few hours later they grow their first shell (called 'D-shaped', or 'straight-hinged). The larvae swim and feed on phytoplankton, using a ciliated velum. At about 12-20 days, and 175-230 μm, they develop a ciliated foot, and begin to investigate substrates for settlement (Chanley and Andrews 1971; Newell and Hidu 1986). At the end of this pediveliger stage, the velum is lost and the larvae settle, moving by crawling, and attaching to grains of sand or sediment, seaweeds or surfaces, using byssal threads. As the clams grow, they burrow deeper, the siphons elongate, and the byssus glands atrophy. At about 5 mm size, clams are called 'seed'. As they grow, they tend to move shoreward (Newell and Hidu 1986). Mortality is very high for larvae and seed clams, but once clams reach adult size, a life span of 10 years is typical, with some specimens living for 20 years (Strasser 1999).

Softshell clams are suspension feeders and can burrow up to 20 cm (in large specimens), with their siphon protruding above the surface. They draw water through the incurrent siphon, to the gills, where food particles are trapped in mucus and carried by cilia to the mouth to be ingested. Particles which are too large or inedible, or simply too dense for ingestion, are rejected by the labial palps as pseudofeces. Diatoms and flagellates are optimal food, but clams can obtain some nutrition from suspended detritus. Feeding rates are influenced by temperature, salinity, and food quality. Filtration and assimilation drops to very low levels below 3ºC. These clams are able to feed in water with considerable quantities of suspended silt and are able to sort cells for silt particles before ingestion (Newell and Hidu 1986). Larvae and newly settled spat are very vulnerable to predation. Small clams are eaten by fishes, crabs, clam worms (Nereidae), moon snails (Naticidae), birds, etc. When clams reach ~60 mm in length, they are less vulnerable to predation (Newell and Hidu 1986).

Food:

Phytoplankton

Consumers:

crabs, fishes, birds, humans

Trophic Status:

Suspension Feeder

SusFed

Habitats

General HabitatGrass BedNone
General HabitatUnstructured BottomNone
General HabitatOyster ReefNone
General HabitatSalt-brackish marshNone
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Tidal RangeMid IntertidalNone
Vertical HabitatEndobenthicNone


Tolerances and Life History Parameters

Minimum Temperature (ºC)0Based on range (Abbott 1974).
Maximum Temperature (ºC)32.5Experimental, 24 hr LC 50 (Kennedy and Mihursky 1971).
Minimum Salinity (‰)3Experimental, acclimation (Castagna and Chanley 1973)
Maximum Salinity (‰)35Based on field occurences (Castagna and Chanley 1973)
Minimum Reproductive Temperature4Season and temperature of spawning is highly variable- a Massachusetts population spawned at 4-6 C (Brousseau 1979, cited by Strasser 1999), while larvae in the laboratory developed poorly below 8 C (Stickney 1979, cited by Strasser 1999).
Maximum Reproductive Temperature23Upper limit for optimal development in the laboratory (Stickney 1964, cited by Strasser 1999).
Minimum Reproductive Salinity10Stickney (1965), cited by Castagna and Chanley (1973)
Maximum Reproductive Salinity35Stickney (1965), cited by Castagna and Chanley (1973)
Minimum Duration10Larval duration, laboratory- Loosanoff and Davies 1963, cited by Strasser 1999
Maximum Duration35Larval duration, laboratory- Loosanoff and Davies 1963, cited by Strasser 1999
Minimum Length (mm)20Minimum size at first sexual maturity (Newell and Hidu 1986)
Maximum Length (mm)163But more usually, up to 100 mm (Abbott 1974; Gosner 1978)
Broad Temperature RangeNonePolar-Warm temperate
Broad Salinity RangeNoneMesohaline-Euhaline

General Impacts

Mya arenaria is an important shellfish species in its native range, from Atlantic Canada to Chesapeake Bay, supporting both commercial and recreational fisheries. On the West Coast of the US, it supported commercial fisheries in San Francisco Bay and elsewhere historically, but is now mainly taken by recreational clammers (Cohen and Carlton 1995). Surprisingly, it is apparently rarely eaten in Europe, and may be more frequently used as bait (Eno et al. 1997; Strasser 1999). Where it is abundant, it is an important suspension-feeder, grazing phytoplankton, and an important food item for fishes, invertebrates, and birds (Nichols and Thompson 1985a; Zaiko et al. 2011) It is also a potential competitor with native bivalves (Moller 1986; Conde et al. 2011).

Economic Impacts

Fisheries- Mya arenaria is an important commercial fisheries species, eaten steamed or fried in eastern North America. Intertidal populations in New England and the Maritimes are harvested with rakes, forks, or hoes, while subtidal populations in Chesapeake and Delaware Bays are taken with hydraulic dredges (Newell and Hidu 1986). In San Francisco Bay, they supported a commercial fishery from the 1880s to 1948, but the fishery steadily declined by 1926 and ended by 1948 (Cohen and Carlton 1995). Elsewhere on the West Coast, the fishery has been mostly recreational, as indicated by state agency websites. Native clams and the Japanese Littleneck (Venerupis philippinarum) are often preferred to Softshell Clams. However, at least one culture operation is taking place in Skagit Bay, WA (Washington Department of Fish and Wildlife 2012, http://wdfw.wa.gov/fishing/shellfish/clams/eastern_softshell.html). In Europe, it is not frequently eaten, and does not support commercial fisheries. Web searches for it under the English name 'Sand Gaper' and 'fisheries', 'fishing', etc., turned up only references to using it as bait on a recreational basis (e.g., http://www.ukmarinesac.org.uk/activities/bait-collection/bc1_1.htm). In the Black Sea, it became very abundant about 4-5 years after its original discovery. When large masses of clams washed ashore, they were fed to chickens (Gomiou et al. 2002). Similarly, in the Sea of Marmars, Turkey, it is of 'no commercial importance', except as a food for larger fishes (Ozturk 2002).

Aesthetic- Soon after its invasion in the Black Sea, by the 1970s, masses of decaying M. arenaria began washing ashore, attracting masses of seagulls (Gomiou et al. 2002). Mass early occurrences and mortalities are also known from Grays Harbor, WA in the late 1800s, though aesthetic impacts were not reported (Palacios et al. 2000).

Ecological Impacts

Herbivory- When abundant, Mya arenaria is a significant herbivore in estuaries, because of its large size and powerful filtration, and its ability to survive in low salinities and wide tidal ranges, where large native bivalves are often rare. Estimated feeding rates of M. arenaria in the southwestern Baltic Sea, off Germany, indicate that this clam can filter the entire water column once or several times a day, depending on water depth (Forster and Zettler 2004). Large biomasses in San Francisco Bay (Nichols and Thompson 1985a; Nichols and Thompson 1985b), the Skagerrak (Moller 1986), the Baltic (Bubinas and Vaitonis 2003; Forster and Zettler 2004; Obolewski and Piesik 2005; Zaiko et al. 2011), and Black Sea (Gomiou et al. 2002) imply significant feeding rates.

Competition- Introduced populations of Mya arenaria in several locations are believed to have reduced or partially replaced native bivalves, including Macoma nasuta (Bent-Nose Macoma) in San Francisco Bay (Cohen and Carlton 1995), Macoma balthica in the Baltic Sea (Obolewski and Piesik 2005), Lentidium mediterraneum in the Black Sea (Skolka and Preda 2010), and Cerastoderma edule (Edible Cockle) in the Skagerrak, Sweden (Moller 1986). In the case of C. edule, competition was reciprocal, with one species or the other having heavy recruitment in some years, and inhibiting recruitment of the other (Moller 1986).

Food/Prey- Mya arenaria, when abundant, has been an important prey organism for clam worms (Nereidae), predatory snails, shrimps, crabs, fishes, ducks, and shorebirds in invaded regions (Carlton 1979; Sadykhova 1979; Ozturk 2002; Bubinas and Vaitonis 2003; Cloern et al. 2007; Skolka and Preda 2010). Because it tolerates low salinities and wide tidal ranges better than many native clams, it has the potential to increase the food supply for predators in estuaries.

Habitat Change- Mya arenaria, as a powerful burrower and filterer, has the potential to alter habitats and sediment characteristics through bioturbation and deposition of peudofeces and also through suspension feeding, increasing water clarity, and light penetration (Obolewski and Piesik 2005; Queiros et al. 2011; Zaiko et al. 2011). Introduced populations of Mya arenaria have often gone through boom-and bust phases, leaving 'death assemblages' of empty shells, providing habitat for many other benthic organisms (Strasser 1999; Palacios et al. 2000).

Trophic Cascade- During periods of exceptional abundance, Mya arenaria may have effects throughout the food web, affecting phytoplankton abundance, and in turn, zooplankton, mysids, and fish recruitment. This may have happened in 1976-1977 in Suisun Bay, California (Nichols and Thompson 1985b; Cohen and Carlton 1995). High abundances of Mya arenaria during 'boom' periods, or its empty shells during 'busts,' can affect the abundance of predators with implications for other benthic organisms. For example, high abundances of M. arenaria shells supported elevated abundances of juvenile Dungeness Crabs (Metacarcinus magister) in Grays Harbor, WA which could lead to increased predation on other benthic organisms (Palacios et al. 2000).

Regional Impacts

NEA-IINoneEcological ImpactHabitat Change
In Poole Harbour, England, Mya arenaria, was the most important species contributing to bioturbation of sediments (Queiros et al. 2011).
MED-IXNoneEcological ImpactCompetition
'Mya arenaria, became a dominant species on sandy bottoms, inducing structural changes in native associations previously dominated by the bivalve Lentidium mediterraneum (Costa, 1829)' (Skolka and Preda 2010).
MED-IXNoneEcological ImpactFood/Prey
'Since the tiny Lentidium mediterraneum is a food resource for the juveniles of many native bottom fish species while the juveniles of Mya arenaria are consumed by the adults of the same' (Skolka and Preda 2010).
B-VIINoneEcological ImpactCompetition
Some community impacts (Zaiko et al. 2011). Off the Pomeranian coast of Poland, Mya arenaria and Macoma balthica often have an inverse relationship, suggestive of competition (Obolewski and Piesik 2005).
B-VIINoneEcological ImpactHabitat Change
Some habitat impacts (Zaiko et al. 2011). Mya arenaria can alter sediment characteristics through bioturbation and deposition of pseudofeces (Obolewski and Piesik 2005).
B-VIIINoneEcological ImpactCompetition
Some community impacts (Zaiko et al. 2011)
B-VIINoneEcological ImpactFood/Prey
Mya arenaria is a frequent food of European Flounder (Platichthys flesus) in the Baltic, off Lithuania (Bubinas and Vaitonis 2003), and of several flounder species off the Pomeranian coast of Poland (Obolewski and Piesik 2005).
NEP-VNorthern California to Mid Channel IslandsEconomic ImpactFisheries
By the 1880s, M. arenaria supported a commercial fishery of 500-900 tons per year in San Francisco Bay, but this declined to 100 tons per year by 1916 to 1926, and ended after 1948, due to overharvesting, pollution, and possible preference for Venerupis phillipinarum (Japanese Littleneck). However, recreational harvests continue to the present (Cohen and Carlton 1995). Extensive plantings were carried out along the California coast by individuals and the California Department of Fish and Game (Weymouth 1920; Bonnot 1940, both cited by Carlton 1979). Recreational clamming probably occurs in many other estuaries where clams are common.
NEP-VNorthern California to Mid Channel IslandsEcological ImpactCompetition
Mya arenaria may have replaced Macoma nasuta in clam beds in San Francisco Bay (Cohen and Carlton 1995).
P090San Francisco BayEconomic ImpactFisheries
By the 1880s, M. arenaria supported a commercial fishery of 500-900 tons per year in San Francisco Bay, but this declined to 100 tons per year by 1916 to 1926, and ended after 1948, due to overharvesting, pollution, and possible preference for Venerupis phillipinarum (Japanese Littleneck). However, recreational harvests continue to the present (Cohen and Carlton 1995).
NEP-VNorthern California to Mid Channel IslandsEcological ImpactHerbivory
Mya arenaria, when abundant, has had significant impact as a filter-feeder. During periods of high salinity, it has been one of several filter-feeders contributing to low phytoplankton biomass in Suisun Bay (Nichols and Thompson 1985a).
NEP-VNorthern California to Mid Channel IslandsEcological ImpactFood/Prey
Mya arenaria is an important prey organism for ducks, shorebirds, flounders, skates, rays, and native crabs and shrimps (Carlton 1979; Cloern et al. 2007).
P090San Francisco BayEcological ImpactCompetition
Mya arenaria may have replaced Macoma nasuta in clam beds in San Francisco Bay (Cohen and Carlton 1995).
P090San Francisco BayEcological ImpactHerbivory
Mya arenaria, when abundant, has had significant impact as a filter-feeder. During periods of high salinity in 1976-1977, it has been one of several filter-feeders contributing to low phytoplankton biomass in Suisun Bay (Nichols and Thompson 1985a).
P090San Francisco BayEcological ImpactFood/Prey
Mya arenaria is an important prey organism for ducks, shorebirds, flounders, skates, rays, and native crabs and shrimps (Carlton 1979; Cloern et al. 2007).
NEP-IVPuget Sound to Northern CaliforniaEconomic ImpactFisheries
In Humboldt Bay. 'It is taken for bait and food by sport clammers.' (Boyd et al. 2002). Recreational clamming for M. arenaria is also popular in Oregon. According to the Oregon Division of Fish and Wildlife, this clam is present in nearly every Oregon estuary (http://www.dfw.state.or.us/mrp/shellfish/bayclams/dig_softshell.asp). In Washington, they are less popular than Butter Clams (Saxidomus gigantea) or Littlenecks (Leukoma staminea- Pacific Littleneck; Venerupis philippinarum- Japanese Littleneck) (Washington Department of Fish and Wildlife 2012, http://wdfw.wa.gov/fishing/shellfish/clams/eastern_softshell.html).
NEP-IIIAlaskan panhandle to N. of Puget SoundEconomic ImpactFisheries
In Washington, they are less popular than Butter Clams (Saxidomus gigantea) or Littlenecks (Leukoma staminea- Pacific Littleneck; Venerupis philippinarum- Japanese Littleneck). However, commercial culture is taking place on private grounds in Skagit Bay and Port Susan (Washington Department of Fish and Wildlife 2012, http://wdfw.wa.gov/fishing/shellfish/clams/eastern_softshell.html). In British Columbia, they are occasionally harvested recreationally, but fisheries are often closed due to red tides (British Columbia Provincial Government, http://www.shim.bc.ca/species/softshel.htm).
P290Puget SoundEconomic ImpactFisheries
According to the Oregon Division of Fish and Wildlife, this clam is present in nearly every Oregon estuary (http://www.dfw.state.or.us/mrp/shellfish/bayclams/dig_softshell.asp). In Washington, they are less popular than Butter Clams (Saxidomus giganteus) or Littlenecks (Leukoma staminea- Pacific Littleneck; Venerupis philippinarum- Japanese Littleneck). However, commercial culture is taking place on private grounds in Skagit Bay and Port Susan (Washington Department of Fish and Wildlife 2012, http://wdfw.wa.gov/fishing/shellfish/clams/eastern_softshell.html).
B-INoneEcological ImpactCompetition
In the Gulmarfjord, Sweden, high densities of adult M. arenaria inhibited recruitment of spat of both Cerastoderma edule and M. arenaria . However, in some years, heavy recruitment of C. edule could inhibit M. arenaria recruitment (Moller 1986).
MED-IXNoneEconomic ImpactAesthetic
By the 1970s, 4-5 years after its initial discovery in the Black Sea, Mya arenaria became so abundant that it washed ashore in decaying masses, attracting huge flocks of seagulls (Gomiou et al. 2002).
MED-IXNoneEconomic ImpactFisheries
During mass occurrences in the 1970s, Mya arenaria was fed to chickens (Gomiou et al. 2002).
MED-VIIINoneEcological ImpactFood/Prey
Mya arenaria in the Sea of Marmara is eaten by Rapana venosa (Veined Rapa Whelk), and by fishes, including sturgeons, Turbot (Scophthalmus maximus), mullets, and gobies (Ozturk 2002).
B-VIINoneEcological ImpactHerbivory
Inferred from large reported biomasses (Bubinas and Vaitonis 2003) and the reporting of 'some ecosystem impacts' (Zaiko et al. 2011).
AR-IIINoneEcological ImpactFood/Prey
In Kandalaksha Bay, White Sea, Russia, the most frequent predators of Mya arenaria are sandpipers (Sadykhova 1979).
P090San Francisco BayEcological ImpactTrophic Cascade
During a drought in 1976-1977 in Suisun Bay, a high abundance of Mya arenaria and other marine filter-feeders may have contributed to a low phytoplankton abundance, which in turn contributed to low zooplankton abundance and a scarcity of the omnivorous Neomysis mercedis, an important food for juvenile fishes. This, in turn, may have led to decreased recruitment of Morone saxatilis (Striped Bass), an economically important introduced gamefish (Nichols and Thompson 1985b; Cohen and Carlton 1995).
NEP-VNorthern California to Mid Channel IslandsEcological ImpactTrophic Cascade
During a drought in 1976-1977 in Suisun Bay, a high abundance of Mya arenaria and other marine filter-feeders may have contributed to a low phytoplankton abundance, which in turn contributed to low zooplankton abundance and a scarcity of the omnivorous Neomysis mercedis, an important food for juvenile fishes. This, in turn, may have led to decreased recruitment of Morone saxatilis (Striped Bass), an economically important introduced gamefish (Nichols and Thompson 1985b; Cohen and Carlton 1995).
NEP-IVPuget Sound to Northern CaliforniaEcological ImpactHabitat Change
In Grays Harbor WA, large shell deposits provide a highly favorable habitat for settling Dungeness Crab (Metacarcinus magister) juveniles. High densities of these crabs may, in turn, limit the recruitment of M. arenaria).
P280Grays HarborEcological ImpactHabitat Change
In Grays Harbor WA, large shell deposits provide a highly favorable habitat for settling Dungeness Crab (Metacarcinus magister) juveniles. High densities of these crabs may, in turn, limit the recruitment of M. arenaria.
B-IIINoneEcological ImpactHerbivory
Estimated filtration rates of Mya arenaria populations in the southwestern Baltic Sea, Germany, at 0.5-9 m depth indicate that that this clam can filter the entire water column in one day or less (Forster and Zettler 2004).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NA-ET1 Gulf of St. Lawrence to Bay of Fundy 0 Native Estab
NA-S3 None 0 Native Estab
NA-ET2 Bay of Fundy to Cape Cod 0 Native Estab
NA-ET3 Cape Cod to Cape Hatteras 0 Native Estab
CAR-VII Cape Hatteras to Mid-East Florida 0 Native Estab
NEP-V Northern California to Mid Channel Islands 1874 Def Estab
NEP-IV Puget Sound to Northern California 1875 Def Estab
NEP-III Alaskan panhandle to N. of Puget Sound 1888 Def Estab
NEP-I Alaska north of the Aleutians 1924 Def Estab
NEA-III None 1700 Def Estab
NEA-II None 1245 Def Estab
AR-V None 1700 Def Estab
B-I None 0 Def Estab
B-II None 0 Def Estab
B-IV None 0 Def Estab
B-III None 0 Def Estab
B-V None 0 Def Estab
B-VI None 1834 Def Estab
B-VII None 1917 Def Estab
B-X None 1900 Def Estab
B-XI None 1900 Def Estab
NEA-IV None 1600 Def Estab
B-IX None 0 Def Estab
B-VIII None 0 Def Estab
MED-VII None 1987 Def Estab
MED-II None 1976 Def Estab
MED-III None 1987 Def Unk
MED-VI None 1984 Def Estab
MED-IX None 1966 Def Estab
NEA-V None 1600 Def Estab
MED-X None 1980 Def Estab
AR-III None 1963 Def Estab
P170 Coos Bay 1875 Def Estab
P260 Columbia River 1973 Def Estab
P130 Humboldt Bay 1917 Def Estab
P070 Morro Bay 1915 Def Failed
P080 Monterey Bay 1911 Def Extinct
P090 San Francisco Bay 1874 Def Estab
P100 Drakes Estero 1919 Def Estab
P095 _CDA_P095 (Tomales-Drakes Bay) 1922 Def Estab
P110 Tomales Bay 1916 Def Estab
P105 _CDA_P105 (Tomales-Drakes Bay) 1919 Def Estab
P112 _CDA_P112 (Bodega Bay) 1916 Def Estab
P116 _CDA_P116 (Big Navaro-Garcia) 1920 Def Estab
P117 _CDA_P117 (Mattole) 1920 Def Estab
P120 Eel River 1920 Def Estab
P135 _CDA_P135 (Mad-Redwood) 1920 Def Estab
P143 _CDA_P143 (Smith) 1920 Def Estab
P160 Coquille River 1943 Def Estab
P180 Umpqua River 1943 Def Estab
P190 Siuslaw River 1880 Def Estab
P200 Alsea River 1943 Def Estab
P210 Yaquina Bay 1917 Def Estab
P220 Siletz Bay 1917 Def Estab
P223 _CDA_P223 (Siltez-Yaquina) 1954 Def Estab
P226 _CDA_P226 (Wilson-Trusk-Nestuccu) 1917 Def Estab
P240 Tillamook Bay 1917 Def Estab
P250 Nehalem River 1954 Def Estab
P270 Willapa Bay 1884 Def Estab
P286 _CDA_P286 (Crescent-Hoko) 2001 Def Estab
P280 Grays Harbor 1888 Def Estab
P292 _CDA_P292 (San Juan Islands) 1895 Def Estab
P293 _CDA_P293 (Strait of Georgia) 1959 Def Estab
P290 Puget Sound 1888 Def Estab
MED-VIII None 1996 Def Estab
AR-IV None 1958 Def Estab
P093 _CDA_P093 (San Pablo Bay) 1895 Def Estab
NA-S2 None 0 Native Estab
P297 _CDA_P297 (Strait of Georgia) 1976 Def Estab
P288 _CDA_P288 (Dungeness-Elwha) 1999 Def Estab
NEP-II Alaska south of Aluetians to the Alaskan panhandle 1924 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
7988 Newcomb 1874, cited by Carlton 1874) 1874 1874-01-01 Alameda County Def 37.7652 -122.2416
7989 Cohen and Carlton 1995 1995 1995-01-01 Collinsville Def 38.0769 -121.8500
7990 Cohen and Carlton 1980 1980 1995-01-01 Suisun Bay Def 38.0541 -121.8683
7991 Nichols and Thompson 1985b 1974 1974-01-01 Palo Alto Def 37.4419 -122.1430
7994 Bonnot 1940, cited by Carlton 1979 1922 1922-01-01 Bolinas Lagoon Def 37.9183 -122.6811
7995 Weymouth 1920, cited by Carlton 1979 1919 1919-01-01 Drakes Estero Def 38.0474 -122.9422
7996 Clark 1916, cited by Carlton 1979 1916 1916-01-01 Tomales Bay Def 38.1285 -122.8730
7997 Packard 1918, cited by Carlton 1979 1915 1915-01-01 Bodega Harbor Def 38.3235 -123.0478
7998 Weymouth 1920, cited by Carlton 1979 1920 1920-01-01 Navarro River mouth Def 39.1921 -123.7611
7999 Weymouth 1920, cited by Carlton 1979 1920 1920-01-01 Big River Def 39.3021 -123.7947
8000 Weymouth 1920, cited by Carlton 1979 1920 1920-01-01 Eel River mouth Def 40.6415 -124.3123
8001 Carlton 1979 1917 1917-01-01 Humboldt Bay Def 40.7498 -124.2095
8002 Boyd et al. 2002 2000 2000-01-01 Southport Landing Def 40.6948 -124.2489
8003 Weymouth 1920, cited by Carlton 1979 1920 1920-01-01 Stone Lagoon Def 41.2501 -124.1010
8005 Weymouth 1920, cited by Carlton 1979 1920 1920-01-01 Big Lagoon Def 41.1708 -124.1272
8006 Weymouth 1920, cited by Carlton 1979 1920 1920-01-01 Lake Earl Def 41.8257 -124.1887
8007 Weymouth 1920, cited by Carlton 1979 1920 1920-01-01 Smith River Delta Def 41.8754 -124.1254
8008 Marriage 1953, cited by Carlton 1979 1943 1943-01-01 Coquille River Def 43.1237 -124.4301
8009 Dall 1897, cited by Carlton 1979 1875 1875-01-01 Coos Bay Def 43.3616 -124.3064
8010 Marriage 1953, cited by Carlton 1979 1943 1943-01-01 Reedsport Def 43.7023 -124.0968
8011 Edmondson 1920, cited by Carlton 1979 1880 1880-01-01 Florence Def 43.9826 -124.0998
8012 Marriage 1953, cited by Carlton 1979 1943 1943-01-01 Waldport Def 44.4268 -124.0687
8013 Edmondson 1920, cited by Carlton 1979 1917 1917-01-01 Newport Def 44.6368 -124.0535
8014 Edmondson 1922, cited by Carlton 1979 1917 1917-01-01 Siletz Bay Def 44.9034 -124.0198
8015 Marriage 1954, cited by Carlton 1979 1954 1954-01-01 Salmon River Def 45.0468 -124.0062
8016 Marriage 1954, cited by Carlton 1979 1952 1954-01-01 Netarts Bay Def 45.4023 -123.9457
8017 Edmondson 1922, cited by Carlton 1979 1917 1917-01-01 Nestucca Bay Def 45.1826 -123.9526
8018 Edmondson 1922, cited by Carlton 1979 1917 1917-01-01 Tillamook Bay Def 45.5129 -123.9165
8019 Marriage 1954, cited by Carlton 1979 1954 1954-01-01 Nehalem River Def 45.6582 -123.9346
8020 Sytsma et al. 2003 2002 2002-10-07 Trestle Bay, Columbia River Def 46.2227 -124.0023
8021 Sytsma et al. 2003 2002 2002-07-09 Ilwaco Def 46.3025 -124.0366
8022 Stearns 1885, cited by Carlton 1979 1884 1884-01-01 Willapa Bay Def 46.4851 -123.9546
8023 Collins 1892, cited by Palacios et al. 2000 1888 1888-01-01 Grays Harbor Def 46.9204 -124.1396
8024 de Rivera et al. 2005 2003 2003-01-01 Neah Bay Marina Def 48.3677 -124.6116
8025 Smith 1896, cited by Carlton 1979 1888 1888-01-01 Tacoma Def 47.2529 -122.4443
8026 Cohen et al. 2001 2000 2000-05-20 Mud Bay, Eld Inlet, Puget Sound Def 47.0558 -122.9888
8027 Cohen et al. 2001 2000 2000-05-17 Magnolia Park, Seattle Def 47.6324 -122.3986
8028 Cohen et al. 2001 2000 2000-05-18 Kellogg Island Passage, Elliott Bay Def 47.5592 -122.3513
8029 MacGinitie 1959, cited by Carlton 1979 1959 1959-01-01 Bellingham Bay Def 48.7365 -122.5646
8030 Smith 1896, cited by Carlton 1979 1896 1896-01-01 San Juan Islands Def 48.5409 -123.0860
8031 Baker 1910, cited by Carlton 1979 1910 1910-01-01 Orcas Island Def 48.6543 -122.9382
8032 Quayle 1970, cited by Carlton 1979 1936 1936-01-01 Coffin Island Def 48.9980 -123.7690
8033 Schrenk 1945, cited by Carlton 1979 1945 1945-01-01 Mayne Island Def 48.8400 -123.2750
8034 Taylor 1895, cited by Carlton 1979 1895 1895-01-01 Departure Bay, Straits of Georgia Def 49.2070 -123.9570
8035 Quayle and Bernard 1966, cited by Carlton 1979 1966 1966-01-01 Barkley Sound Def 48.8630 -125.4050
8036 Newcomb 1893, cited by Carlton 1979 1893 1893-01-01 Clayoquot Sound Def 49.2150 -126.1200
8037 1955, Quayle 1960, cited by Carlton 1979 1955 1955-01-01 Prince Rupert Harbour Def 54.3510 -130.3290
8038 Quayle 1943, cited by Carlton 1979 1939 1939-01-01 Masset Inlet ( Def 53.7020 -132.3380
8039 Quayle 1960 cited by Carlton 1979 1955 1955-01-01 Naden Harbour Def 54.0180 -132.6390
8040 Hanna 1966 1946 1946-01-01 Ketchikan, Tongass Narrows Def 55.3886 -131.7522
8041 Hines and Ruiz 2001 1999 1999-01-01 Jakolof Bay, Kachemak Bay Def 59.4567 -151.5186
8042 Powers et al. 2006 2001 2001-04-01 Copper River Delta, Prince William Sound Def 60.3333 -145.4667
8043 Nybakken 1969, cited by Carlton 1979 1969 1969-01-01 Three Saints Bay Def 57.1492 -153.4881
8044 Bernard 1979 1979 1979-01-01 Kotzebue Sound Def 66.5461 -162.7494
8045 Bernard 1979; Carlton 1979, 1979 1979-01-01 Bristol Bay Def 57.3264 -159.8247
8046 Bernard 1979; Carlton 1979 1979 1979-01-01 Norton Sound Def 63.8492 -164.2689
8047 Bousfield 1960 None 9999-01-01 Baie St. Paul Native 47.4500 -70.5000
8048 U.S. National Museum of Natural History 2012 None 9999-01-01 Grand Manan Island Native 44.7000 -66.8000
8049 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Point at end of Ingonish Harbor Native 46.7000 -60.3667
8050 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Pointe du Chene Native 46.2550 -64.5050
8051 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Eddies Cove Native 51.4360 -56.4480
8052 Academy of Natural Sciences of Philadelphia 2012, None 9999-01-01 near Port Mouton Native 43.9270 -64.8070
8053 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Kitson's Island, opposite Baddeck Native 46.1020 -60.7520
8054 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Fullerton's Marsh, Bunbury Native 46.2350 -63.0540
8055 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Basin Island, off Coffin Island, Magdalen Islands Native 47.3250 -61.3610
8056 Academy of Natural Sciences of Philadelphia 2012, None 9999-01-01 None Native 47.8660 -69.5120
8057 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Pictou Native 45.6780 -62.6860
8058 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Miquelon Native 47.1000 -56.3778
8059 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 L'Anse Aux Meadows Native 51.6167 -55.5000
8060 Museum of Comparative Zoology 2010 None 9999-01-01 Trenton, S of Trenton Bridge Native 44.4390 -68.3700
8061 Museum of Comparative Zoology 2012 None 9999-01-01 South Thomaston Native 44.0515 -69.1278
8062 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Kittery Native 43.0834 -70.7078
8063 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Meadow Cove, Damariscotta River Native 43.8740 -69.5912
8064 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Halifax Harbour Native 44.6410 -63.5470
8065 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Barnstable Native 41.7168 -70.2661
8066 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Plymouth Native 41.9751 -70.6661
8067 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Revere Beach Native 42.4251 -70.9828
8068 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Nantucket Native 41.3043 -70.0453
8069 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Sherwood Island, Westport Native 41.1148 -73.3309
8070 US National Museum of Natural History 2012 None 9999-01-01 Woods Hole Native 41.5237 -70.6786
8071 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Robin's Island, Long Island Native 40.9695 -72.4620
8072 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 mouth of Dias Creek Native 39.0936 -74.8764
8073 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Ocean City Native 39.2776 -74.5746
8074 Ristich et al. 1977 None 9999-01-01 Weehawken Native 40.7559 -74.0268
8075 US National Museum of Natural History 2012) None 9999-01-01 Govenors Run, Chesapeake Bay Native 38.6800 -76.5300
8076 U.S. National Museum of Natural History 2012 None 9999-01-01 Ocean City Native 38.3237 -75.1052
8077 U.S. National Museum of Natural History 2012 None 9999-01-01 Camp Fuller, Wakefield/ Native 41.4098 -71.5112
8078 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Moores Beach Native 39.1876 -74.9502
8079 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Irvington Native 37.6615 -76.4191
8080 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 10 miles NW of Easton (Wye Island) Native 38.8873 -76.1191
8081 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Beaufort Harbor Native 34.7163 -76.6646
8082 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Folly Beach Native 32.6552 -79.9404
8083 Museum of Comparative Zoology 2012 None 9999-01-01 Little Island, Virginia Beach Native 36.5699 -75.8885
8094 Zenkevich 1963 1963 1963-01-01 east of Svyatoy Nos Def 68.1500 39.7333
8095 Sadykhova 1979 1979 1979-01-01 Chupa Inlet, Kandalaksha Bay Def 66.3228 33.5258
8096 Strasser 1999 None 9999-01-01 Faroe Islands Def 62.0000 -6.7500
8097 MarLin 2012 None 9999-01-01 Shetland Islands Def 60.3038 -1.2689
8098 Lasota et al. 2004 None 9999-01-01 Oosterschelde Def 51.5539 3.9658
8099 Cross et al. 2012 None 9999-01-01 Bannow Bay Def 52.2000 -6.7667
8100 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Tholen Def 51.5333 4.2167
8101 Academy of Natural sciences of Philadelphia 2012 None 9999-01-01 Mouth of River Faughan, Lough Foyle Def 54.9833 -7.3000
8102 Academy of Natural sciences of Philadelphia 2012 None 9999-01-01 Southampton Def 50.8970 -1.4042
8103 Academy of Natural Sciences of Philadelphia 2012 None 9999-01-01 Charente-Maritime Def 45.9500 -0.9667
8105 Oskarssen 1961, cited by Strasser 1999 1958 1958-01-01 east coast Def 63.9067 -16.7072
8106 Academy of Natural Sciences of Philadelphia 2012 1923 1923-01-01 Helsingborg Def 56.0500 12.7167
8107 Petersen et al. 1992 1245 9999-01-01 Skagen Odde, Viking excavations Def 57.7400 10.5956
8109 Winther and Gray 1985, cited by Strasser 1999 None 9999-01-01 Oslofjord Def 59.3500 10.5833
8110 Lyell 1835, cited by Munthe 1894 1834 9999-01-01 4 mi. south of Stockholm Def 59.3294 18.0686
8111 Lasota et al. 2004 None 9999-01-01 Mechelinki Def 54.6089 18.5122
8112 Obolewski and Piesik 2005 None 9999-01-01 Kolobrzeg Def 54.1833 15.5833
8113 Museum of Comparative Zoology 2012 None 9999-01-01 Egg Harbour Native 53.7770 -56.9070
8114 Museum of Comparative Zoology 2012 1897 9999-01-01 Limfjorden Def 56.9428 9.0750
8115 Bubinas and Vaitonis 2003 None 9999-01-01 Klaipeda Def 55.7000 21.1333
8116 Pollumae et al. 2009 None 9999-01-01 off Tallin Def 59.4372 24.7453
8117 Pollumae et al. 2009 None 9999-01-01 Kardia Def 58.9982 22.7469
8118 Lasota et al. 2004 None 9999-01-01 Gironde estuary Def 45.2669 -0.7108
8119 Strasser 1999 None 9999-01-01 Arcachon Basin Def 44.6833 -1.1667
8120 Conde et al. 2011 2007 2007-01-01 Coina Def 38.5936 -9.0408
8121 Conde et al. 2011 2010 2010-01-01 Rio Lima estuary Def 41.6667 -8.8333
8122 Conde et al. 2012 1997 1997-01-01 Murtosa Def 40.7375 -8.6381
8123 Zenetos et al. 2003 1976 1976-01-01 Etang de Berre Def 43.4458 5.1139
8124 Crocetta and Turolla 2011 2008 2008-01-01 Sacca di Goro, Po River valley Def 44.7833 12.2500
8125 Crocetta and Turolla 2011 2004 9999-01-01 Sligo Def 54.2667 -8.4833
8126 Crocetta and Turolla 2011 1996 9999-01-01 Forsol Def 70.7203 23.7986
8127 Zenetos et al. 2005; Crocetta and Turolla 2011 1984 1984-01-01 Gulf of Saronicos Def 37.7839 23.6178
8128 Albayrak and Balcis 1996, cited by Albarak 2011 1996 1996-01-01 Sea of Marmara Def 40.7500 28.0000
8129 Gomiou et al. 2002, Skolka and Preda 2010 1966 1966-01-01 Black Sea Def 44.6333 28.8833
8130 Gomiou et al. 2002 1966 1966-01-01 Dneister estuary Def 46.1833 30.3333
8131 Savchuk 1980; Zaitsev and Ozturk 2001 1980 1980-01-01 Sea of Azov Def 46.0000 37.0000
26712 Fairey et al. 2002 2001 2001-09-19 Tomales Bay Infaunal 01 Def 38.2062 -122.9381
27412 Bonnot 1932, 1932 1932-01-01 Suisun Bay - Martinez Def 38.0287 -122.1333
27525 Cohen, et al. 2005 (SF Bay Area RAS) 2004 2004-05-24 Fruitvale Bridge, San Francisco Bay Def 37.7690 -122.2296
28761 Foss 2009 2005 2005-06-07 Oakland Inner Harbor - Shipping cranes Def 37.7947 -122.3095
28798 Foss 2009 2005 2005-10-20 San Pablo Bay Pumphouse Def 38.0446 -122.4326
29326 Foss 2009 2005 2005-06-09 Paradise Area Def 37.9062 -122.4768
29472 Foss 2009 2005 2005-06-09 McNears Beach Def 37.9962 -122.4556
29789 Foss 2011 2010 2010-06-03 Berkeley Flats/Berkeley Pier Def 37.8600 -122.3256
29968 Foss 2009 2005 2005-06-08 Sea Plane Lagoon Def 37.7761 -122.2998
30861 Foss 2009 2005 2005-10-19 Hercules Wharf Def 38.0231 -122.2928
31951 Foss 2009 2005 2005-07-08 Richmond Marina Def 37.9137 -122.3504
32641 Foss 2009 2005 2005-11-15 China Camp Def 38.0025 -122.4617
32945 Foss 2009 2005 2005-06-10 Toll Plaza Def 37.8266 -122.3166
33121 Foss 2011 2010 2010-06-13 Hayward Landing Def 37.6447 -122.1543

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