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  • Writer's pictureDon Yurewicz

Asian Clam (EXOTIC)

Updated: Jun 18, 2020

The Asian clam has been identified in 7 waterbodies within New Hampshire.

The Asian clam is a small (<50 mm) lightly-colored bivalve. The shell is oval-triangular shaped with distinct, concentric ridges. The outside of the shell is olive, or yellowish to black-brown in color, with 1-3 brown/purple colored radial bands (particularly in juveniles) and white erosion rings near the "beak".

Why are Asian clams a nuisance?

  • The clam reproduces rapidly and is tolerant to cold waters adding to its success as an invasive species. Asian clams can self-fertilize, and release up to 2,000 juveniles per day, and more than 100,000 in a lifetime. Juveniles are only 1 mm long when discharged, and take one to four years to reach maturity.

  • The high concentration of nutrients (e.g. nitrogen) excreted by clams enhances the growth of algae. Slimy green algae blooms could dominate what are now clear and beautiful waterbodies.

  • The clams quickly form dense mats of sharp shells in shallow sandy areas… not at all friendly to the feet of swimmers.

  • The clams can create localized calcium-rich environments that are more friendly to other invaders, such as zebra mussels, enabling them to thrive.

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