BIOTIC Species Information for Mya arenaria
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Researched byLizzie Tyler Data supplied byUniversity of Sheffield
Refereed byThis information is not refereed.
Distribution and Habitat
Distribution in Britain & IrelandFound on all British coasts but is not recorded from the Isles of Scilly.
Global distributionFound on the European coast from the White Sea to northern Norway, in the Baltic Sea and Wadden Sea to Portugal as well as the Black Sea. Reported from Labrador to Georgia in the W. Atlantic and from North Sound, Alaska to California in the E. Pacific.
Biogeographic rangeNot researched Depth range0 - 20 m
MigratoryNon-migratory / Resident   
Distribution Additional InformationThe southern distribution of Mya arenaria may be restricted by a limit of 28 °C for both adults and larvae (Newell & Hidu, 1986; Strasser, 1999). Various authors suggested that the northern distribution was limited by critical spawning temperature of 10-12 °C and 12-15 °C required for larval development, however, Strasser (1999) noted some exceptions and concluded that this hypothesis needed further examination.

Distribution: Mya arenaria is found most abundantly in intertidal and shallow subtidal areas but can reach 192 m depth in the subtidal (Strasser, 1999). The majority of clams >50 mm are found in sediment between 15 - 20 cm deep in the Wadden Sea, but may burrow up to 40 cm deep. As they grow adults live deeper in the sediment, their siphons growing accordingly and large clams establish a permanent burrow. Young clams (up to 50 mm) can burrow again if disturbed. However the foot becomes much reduced and shorter in larger specimens. With increasing size it becomes more difficult for exposed specimens to raise the shell into position and therefore. if disturbed, fewer large than small individuals manage to reburrow. For example, 62% of small clams (35-50mm), 39% of medium sized (51-65 mm) and only 21% of large clams (66-75 mm) had reburrowed within 48 hours (Pfitzenmeyer & Drobeck, 1967).

Mya arenaria grows faster in fine rather than coarse sediments and fastest in sand or sandy mud. The clam has difficulty burrowing in sediments larger than 0.5 mm (coarse sand). Areas with fast currents support highest densities and growth rates whereas excessive silt reduces growth rates (Newell & Hidu, 1986). Densities of adults vary between years and location, e.g. Clay (1966) reported adult densities between ca 5 /m² to 300 /m² in the UK and Strasser et al. (1999) reported abundances between 0-243 individuals /m² (with a mean of 11.8 individuals /m²) in the Wadden Sea. Strasser et al. (1999) concluded that the Wadden Sea population is greatest at the mid to low tidal level and resulted from larval settlement. Its patchy distribution and dominance of single year classes being due to wind direction during peaks of larval settlement, and when juvenile predation is low. Clams that survive the first year may reach several years of age but mass mortalities may occur at any time, due to indeterminate causes (Strasser et al, 1999).

Global distribution: Mya arenaria became extinct on the east coasts of the Pacific and Atlantic during the glaciations of the Pleistocene. It subsequently colonized the European coast between the 13 th and 17 th centuries, possibly introduced by the Vikings (as food or bait) (Eno et al., 1997; Eno et al., 2000; Strasser, 1999). Mya arenaria has been reported from Kamchatka to southern Japan and China, however these records may have been confused with Mya japonica (Strasser, 1999). Strasser (1999) also regarded additional records from Iceland, the Mediterranean and Florida as dubious. Mya arenaria probably invaded the Pacific east coast as a by-product of oyster transplants but was later intentionally introduced as a commercial fishery. It was probably introduced into the Black Sea around 1960 as larvae in the ballast waters of Baltic Sea tankers (Strasser, 1999) . Strasser (1999) notes that although introduction may have been effected by man its present distribution is also the result of significant natural expansion.


Substratum preferencesMuddy gravel
Coarse clean sand
Fine clean sand
Muddy sand
Mud
Mixed
Sandy mud
Physiographic preferencesStrait / sound
Sealoch
Ria / Voe
Estuary
Enclosed coast / Embayment
Biological zoneMid Eulittoral
Lower Eulittoral
Sublittoral Fringe
Upper Infralittoral
Lower Infralittoral
Upper Circalittoral
Lower Circalittoral
Wave exposureExposed
Moderately Exposed
Sheltered
Very Sheltered
Tidal stream strength/Water flowModerately Strong (1-3 kn)
Weak (<1 kn)
SalinityFull (30-40 psu)
Low (<18 psu)
Reduced (18-30 psu)
Variable (18-40 psu)
Habitat Preferences Additional Information
Distribution References Fish & Fish, 1996, Campbell, 1994, Hayward et al., 1996, Tebble, 1976, Foster-Smith, 2000, Turk & Seaward, 1997, Crothers, 1966, Allen, 1962, Seaward, 1982, Seaward, 1990, Bruce et al., 1963, Newell & Hidu, 1986, Strasser, 1999, Eno et al., 1997, Clay, 1966, Newell, 1982, Armonies, 1994, Kühl, 1981, Anonymous, 1996, Strasser et al., 1999, Hawkins, 1994, Dow & Wallace, 1961, Pfitzenmeyer & Drobeck, 1967, Hayward & Ryland, 1990,
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