Silence of the clams: the effect of Dreissena polymorpha (zebra mussels) removal and the health of Douglas Lake Unionidae.

Abstract

Dreissena polymorpa (zebra mussels) are a concern in many waterways throughout the United States. They have begun to choke out native fauna such as clam species in the Great Lakes Region. This study researched the effects of continuous removal of D. polymorpha from shells of native unionid species, Anodonta grandis (giant floaters), Lampsilis siliquoidea (fatmucket clams), Ligumia recta (black sand mussel), and Ligumia nasuta (eastern pondmussels) in North and South Fishtail Bay of Douglas Lake (Pellston Michigan, USA). It also examined the rate of D. polymorpha attachment to clean unionids. Routinely cleaned L. siliquoidea had significantly higher mass (p=.0496), but not longer shells (p=.168). Routinely cleaned and uncleaned L.recta had no difference in length or mass (p=.429 and p=.307). The mass of L. siliquoidea and L. recta was correlated with the length of their shells in both routinely cleaned and uncleaned areas. Dreissena polymorpha were found to attach to unionids at a rate of six new individuals per unionid every two weeks. Cleaning native unionids appears to have a significant effect on the health of L. siliquoidea, but not on L. recta.