• Don Yurewicz

Asian Clam (EXOTIC)

Updated: Jun 18

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.

Sources: https://www.kcet.org/redefine/the-tiny-clams-that-ate-the-bay-delta; https://www.lakegeorge.com/lakefriendlyliving/2011/11/so-why-is-a-little-asian-clam-so-bad-for-the-lake-anyway/; http://www.tsusinvasives.org/home/database/corbicula-fluminea#:~:text=The%20clam%20reproduces%20rapidly%20and,four%20years%20to%20reach%20maturity.


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Conway Lake is currently free of invasive (aka "exotic") species. The posts below include descriptions of invasive plants and animals we need to watch for when we patrol on Conway Lake. New Hampshire

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