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Soft Shell Clam

Mya arenaria

Unlike most other clams, soft shell clams cannot completely retract their siphons into their shells. (Dave Cowles/Rosario Beach Marine Laboratory)
Unlike most other clams, soft shell clams cannot completely retract their siphons into their shells. (Dave Cowles/Rosario Beach Marine Laboratory)

The soft shell clam is a bivalve with thin, elongated shells. It lives buried in soft sediments in the middle Chesapeake Bay.

Appearance:

The soft shell clam's thin, oval, elongated shells grow to 3 to 4 inches in length. Its shells are chalky white with a thin, brittle covering that varies in color from brownish to gray. When closed, the shells gape open at both ends. One foot and two long, leathery siphons protrude from either end. Left shell has a spoon-like depression at the hinge, which the right shell fits into.

Habitat:

Burrows deeply in soft sediments from the shoreline to a depth of about 20 feet. Unless disturbed, it will spend its entire adult life in one place.

Range:

Widely distributed throughout most of the Chesapeake Bay. Concentrated in the middle Bay, from Eastern Bay to Pocomoke Sound on the Eastern Shore and from the Severn River to the Rappahannock River on the western shore.

Feeding:

As filter feeders, soft shell clams draw in water through one siphon, then filter out plankton from the water. Unused water and particles are ejected through the other siphon.

Predators:

Adult soft shell clams have many natural predators, including raccoons, blue crabs, horseshoe crabs, diving ducks and cownose rays. Humans harvest soft shell clams commercially.

Reproduction and Life Cycle:

These clams usually spawns twice per year: once in late spring and once in mid- to late autumn. Both eggs and sperm are released into the water column. The number of eggs a female releases depends on its size. Eggs develop into larvae within one day of being fertilized. Larvae swim freely for about 1-3 weeks, during which they develop a foot and shells. Larvae eventually find a suitable place to settle and anchor themselves to the bottom using thin threads secreted from a gland on the foot. Juvenile soft shell clams can be very active. Eventually they find a permanent place to burrow. Some soft shell clams have been known to live 12 years.

Other Facts:

  • Adults can only move vertically and cannot rebury themselves if removed from their burrow.
  • Unlike most other clams, soft shell clams cannot completely retract their siphons into their shells.
  • When disturbed, soft shell clams squirt water out of their siphon.

Sources and Additional Information:




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